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Zoonotic Diseases in Shelters

Introduction

A zoonotic disease is an infection that is naturally transmitted from vertebrate animals to human beings. Potential zoonotic agents include bacteria, viruses, fungi, internal parasites and arthropods. There are many factors common in animal shelters that make zoonotic disease a particular concern in this environment. For the protection of shelter staff and volunteers as well as that of the public, it is critical that animal shelter professionals be familiar with the most common zoonotic threats in a shelter environment, and the general principles of preventing transmission of zoonotic disease. This guide is intended to familiarize shelter professionals with some of the general considerations in preventing zoonotic disease, and key features of some of the diseases most likely to be encountered in a shelter. Diseases were selected for inclusion because they are either common or potentially very severe. Many of the diseases included are of increasing importance in recent years. Although the focus of this guide is diseases affecting dogs and cats, shelters often care for a wide range of species, from wildlife to livestock. Virtually all species can be carriers of zoonotic disease, and unusual diseases may also be seen in the more common species seen in shelters. This guide is by no means exhaustive.

An animal shelter is unlike virtually any other environment in which animals are maintained, and poses unique challenges for the control of infectious disease in general and zoonotic disease in particular. There is often a high degree of turnover of the population of animals in a shelter, meaning that there is always a new group of animals at risk of contracting disease. Stress, poor nutrition, and presence of concurrent disease or parasitic infestation are common problems that increase the risk of transmission of infectious disease and the likelihood that infected animals will shed significant amounts of disease causing agents into the environment. Many shelters struggle to care for animals in older facilities that may be difficult to properly sanitize, and may be characterized by poor ventilation, overcrowding, and uncomfortable temperature extremes, all of which contribute to the ready spread of infection. Treatment with antibiotics, common at many shelters for such conditions as kennel cough and upper respiratory infection, further reduces animals' resistance to some gastrointestinal infections, and can increase the spread of such zoonotic infections as salmonellosis.

In addition to the general difficulties of controlling infectious disease in a shelter environment, certain factors common in sheltered animals specifically increase the risk of various zoonotic diseases. Animals frequently enter shelters without a history of proper veterinary care or vaccination. Zoonotic diseases more likely to occur in unvaccinated animals include rabies and leptospirosis. Many animals in shelters have a history of roaming outdoors, hunting or scavenging. This increases the risk of infection with such zoonotic conditions as echinococcosis, leptospirosis, salmonellosis, and rabies. Animals that have spent time outdoors and received minimal care are more likely to be infested with external parasites. Some external parasites can be directly transmitted to humans (i.e. scabies, cheyletiella), or they can serve as vectors for zoonotic disease such as Lyme disease and Rocky Mountain spotted tick fever. Finally, animals entering shelters are often frightened, disoriented, and of unknown temperament. Staff handling these animals are at increased risk of being bitten or scratched. Besides the injury and infection that can occur due to the wound itself, this can serve as a means of transmitting zoonotic diseases such as rabies and cat scratch fever.

Geneal principles of prevention and control of zoonotic disease in a shelter environment

As described in the individual disease profiles below, many animals infected with and potentially shedding a zoonotic disease show minimal or no clinical signs. Diseases for which animals are usually or commonly asymptomatic include toxocariasis, salmonellosis, leptospirosis, cat scratch fever, and toxoplasmosis. In addition to the existence of clinically inapparent diseases, many animals will continue to shed infectious agent for some time after recovery from clinically apparent disease, as can be the case for ringworm, salmonella, leptospirosis and others. It is imperative, therefore, that shelter staff realize the potential for any animal to be a potential source of infection, and maintain protective measures as a matter of routine, not just when disease is recognized.

General principles of sanitation and infectious disease control apply to control of zoonotic diseases:

1. A fomite is any inanimate object that can spread disease. Fomites include hands, dishes, and tools such as grooming implements and poop scoopers. Hands should be washed and disinfected after animal contact, including indirect contact from cleaning cages, handling dishes or litter pans. Toys, blankets and dishes should be machine washed or discarded between animals, or should go home with newly adopted animals.
2. Special attention should be paid to incoming animal processing areas and exam rooms. Exam surfaces should be cleaned between each animal, and the whole area cleaned thoroughly at least once a day. Areas that multiple animals pass through each day, such as "getting acquainted" areas where animals and adopters meet, should be cleaned after each use and thoroughly disinfected at least once a day.
3. Feces should be cleaned up at least once a day from runs and cages, and should be removed immediately from common play areas and disposed of properly.
4. Feces should be cleaned up at least once a day from runs and cages, and should be removed immediately from common play areas and disposed of properly.
5. Dirt and grass play yards, while aesthetically pleasing, can serve as a reservoir for resistant agents such as roundworm. It is particularly important that puppy and kitten play areas be readily cleaned and disinfected, as these young animals are most likely to be affected by many infectious agents.
6. Routine disinfection should be performed using agents effective against most bacteria and viruses. Acceptable choices include bleach (diluted at 1:32) and quaternary ammonium compounds. Shelter staff should be aware of agents, such as ringworm and many parasitic infestations, that require more rigorous or specific disinfection procedures.
7. Animal flow and handling order should be planned to reduce spread of infectious disease.

Many animals with zoonotic conditions show no outward signs. However, when zoonotic diseases do cause signs, they often present with vague signs similar to other common infectious conditions in shelters. Therefore, extra precautions should be taken whenever handling sick animals. Such preventive measures protect the shelter population as well as human health.

1. Sick animals should be housed in isolation, and the number of staff caring for these animals should be limited.
2. Staff handling sick animals should wear protective clothing, which should be removed after leaving isolation wards.
3. Appropriate diagnostics should be performed when zoonotic disease is suspected.
4. It may not be practical or warranted to isolate animals with mild conditions such as diarrhea, but these animals should be clearly identified as suffering from a possibly infectious condition and should not be walked or socialized in common areas that can't be easily cleaned.
5. Volunteers should be trained to perform a visual health check before socializing with any animal, and notify shelter staff before handling the animal if any sign of disease is noted.
6. When a zoonotic condition is specifically diagnosed or suspected, the animals cage should be clearly posted with the name of the condition and any precautionary measures (such as protective clothing or special cleaning procedures) required.

Internal and external parasites contribute to a state of general ill health and increase susceptibility to infectious conditions. In addition, internal and external parasites may be directly infectious to humans, or may serve as vectors to spread disease. Parasite control increases animals' comfort and adoptability as well as protecting human health.

1. Internal parasite control should, at minimum, include routine treatment of puppies, kittens and nursing mothers for roundworms and hookworms (see discussion below under specific disease descriptions).
2. Ideally, all incoming animals should be treated with an age and species-appropriate product effective against fleas and ticks as needed depending on region and time of year. If this is too costly, severely infested animals should be individually treated.
3. Environmental treatment of group housing and common areas of shelter as needed for flea control.
4. Rodents and insects can spread zoonotic disease, as well as spreading non-zoonotic infections.
5. Food should be stored in sealed containers and not left in runs overnight where rodents are a problem. Further rodent and insect control measures should be undertaken as needed.

Protection of Staff and Volunteers

It is vital that staff and volunteers have the knowledge and equipment they need to perform their jobs effectively while protecting themselves from zoonotic disease.

1. Provide training and continuing education for staff on the risks of zoonotic disease.
2. Provide appropriate clothing and other protective equipment to prevent transmission of disease.
3. Train all staff to wash hands frequently, after handling animals, before eating and at the end of each shift.
4. Post guidelines detailing what to do in case of a bite or suspected zoonotic disease exposure, including phone numbers for medical emergencies, public health, physician and veterinary contacts.
5. Provide staff with pre-exposure rabies vaccination according to Center for Disease Control guidelines. Maintain written records for staff members regarding vaccination status for rabies and tetanus.

It is becoming increasingly common for community members (as well as shelter staff) to provide temporary care for animals in their own homes. Often very young or sick animals are most in need of this special care. These animals can greatly benefit from care outside of the shelter, but these are also the animals most at risk for contracting and spreading infectious disease, including zoonoses. Foster home environments are often more difficult to effectively disinfect than shelters, and can become chronically contaminated by durable agents such as ringworm (dermatophytes) or roundworm (Toxocara spp.). Contaminated foster homes can then serve as a focus for infection of the many vulnerable animals passing through that home, and these animals may return to the shelter to spread their new infection to other animals, staff and adopters. Therefore, for the protection of foster care providers as well as shelter animals, special precautions should be taken when placing animals in foster care.

Foster care providers should receive training as described above for staff members regarding zoonotic disease, including written information in foster care training material.

1. All animals should receive fecal exams (ideally), or if staffing limitations prohibit this, at minimum animals with persistent or severe diarrhea should be screened.
2. All cats, and dogs with skin lesions should be examined with a Woods lamp as well as visually for signs of ringworm. Suspicious lesions should be treated as described below under ringworm discussion.
3. Puppies, kittens and nursing mothers should be dewormed, and a schedule arranged for re-treatment and vaccination.
4. Animals should be treated for fleas and ticks as needed before leaving the shelter to avoid contaminating a private home.
5. Ill animals and animals suspected or known to have a zoonotic condition should be restricted in the foster home to an easy to disinfect area such as a bathroom. Protective clothing should be worn when handling these animals, just as in a shelter. During times when shelters are having frequent problems with infectious disease, these precautions should be extended to all animals in foster care.
6. Several zoonotic conditions are readily spread from aborted tissue, and may cause no other signs in the affected animal (i.e. Q fever, Brucella canis). When pregnant animals are placed in foster care, foster care providers should be advised to wear protective clothing and take extreme care in handling tissue should an abortion occur.
7. Liability and ethical issues associated with placing animals with a known zoonotic condition in foster care should be discussed and a written policy established.

As shelter professionals, we have an obligation to protect those people who adopt our animals to the greatest extent possible, both from zoonotic disease and injury from bites or scratches. In addition to ethical considerations, shelters can suffer financial liability when adopted animals transmit disease. Pet stores and veterinarians have been sued for adopting out animals with such zoonotic conditions as ringworm and roundworm, with settlements in some cases over a million dollars2-4. Shelters can ill afford the financial blow or negative publicity that would arise from such a case. Specific liability issues should be discussed with legal council; however, shelters can help protect themselves and the public by ensuring that the public is given non-alarmist but accurate information about the risk of zoonotic disease, and that reasonable efforts are made to identify and control zoonotic disease in the shelter.

1. Post prominent signs encouraging all visitors to the shelter to wash hands after handling any animal and after visiting the shelter. Make sure hand washing stations (sinks or hand-sanitizer dispensers) are readily available in animal areas.
2. Give adopters general written and verbal information on preventing zoonotic disease, such as the importance of hand washing, preventing feces from building up in the environment, maintaining internal and external parasite control, and maintaining a regular program of veterinary care.
3. Advise adopters in writing of any specific steps that have been taken to control zoonotic disease in an individual animal, such as prophylactic deworming, and when any further treatments will be required. Also inform adopters of any exams that have been performed, and whether or not the animal has been examined by a veterinarian.
4. Develop an adoption contract that requires a visit to a veterinarian within a week of adoption, and explain the importance of this in protecting the health of family members as well as the new pet.
5. Include a written statement in the adoption contract stating that the animal's health can not be guaranteed. If the animal has not been examined by a veterinarian, include this statement in the contract, along with the shelter's policy on animals found to be ill soon after adoption.
6. Develop a shelter policy on adopting out animals with known or suspected zoonotic conditions. If such animals are to be adopted out, written material should be provided to adopters on the specific disease, and a waiver should be signed. Be aware that such waivers may not protect the shelter from liability.
7. Provide results of any temperament testing that was performed. Temperament concerns involving aggression or a history of biting/scratching should be treated in a similar manner to diagnosed or suspected zoonotic conditions in terms of potential liability.

Many zoonotic diseases are much more severe or even deadly in immunocompromised people. There are many examples discussed in this guide, including bartonella infection (the agent of cat scratch fever), salmonellosis, bordetellosis (kennel cough), and toxoplasmosis. People at increased risk include people with AIDS, people on chemotherapy or being treated for immune mediated disease, people with organ or bone marrow transplants, the elderly, the very young, and pregnant women. General guidelines exist describing ways immunocompromised people can safely keep pets. These are readily available from several sources; for example, PAWS (Pets Are Wonderful Support), in conjunction with the Humane Society of the United States, has produced guidelines which can be found at the PAWS website at www.pawssf.org. Guidelines for people infected with HIV are also available from the Center for Disease Control5. Specific considerations for shelters include the following.

1. It may not be apparent that a potential adopter is immunocompromised, and people may be reluctant to discuss this private issue. Therefore, material regarding immunocompromised people and pets should be readily available and prominently placed to allow for anonymous contemplation.
2. The safest choice of dog or cat for an immunocompromised adopter is an adult animal (over 1 year old) that is current on its vaccinations and was surrendered from a private home with a history of being a well-cared for pet and with no history of roaming loose. The very safest choice would be to facilitate adoption of such an animal directly from its former home, rather than having it pass through the shelter and potentially become infected with a zoonotic condition.
3. Immunocompromised adopters should avoid any animal showing signs of disease or ill health. Animals selected should be free of fleas and ticks and treated for internal parasites prior to going home.
4. As with any new adoption, the animal should be assessed by a veterinarian soon after adoption and appropriate deworming, vaccination and other treatment instituted or continued.
5. Reptiles are not recommended as pets for immunocompromised people, because of the high risk of salmonella infection.

An overview of some zoonotic diseases of importance in a shelter environment.

Zoonotic diseases found in the gastrointestinal tract of animals

Zoonotic skin diseases

Zoonotic diseases spread by bites and scratches

Miscellaneous zoonotic diseases

Campylobacteriosis

Disease name: Campylobacteriosis

Type of agent: Gram negative bacteria

Shelter speciesmost commonly infected:
Dogs, cats, many other mammalian and avian species. Puppies and kittens at higher risk. More common in animal shelters and kennels than in private homes.

Clinical signs in affected animals:
Most often asymptomatic. May cause diarrhea with or without anorexia, fever and vomiting.

Diagnosis in animals:
Tentative diagnosis can be made by examination of fresh fecal smear. Campylobacter species appear on gram stain as gram negative, gull-wing shaped slender rods. Fresh fecal samples can also be examined by darkfield or phase-contrast microscopy for curve shaped, motile bacteria. Non-pathogenic species of Campylobacter appear identical on microscopic examination, so culture of fresh fecal sample is required for species identification and definitive diagnosis.

Transmission between animals: Fecal-oral spread.

Transmission to humans:
Most human infection is from contaminated water or food. Transmission from infected animals occurs through fecal-oral route.

Clinical disease in humans:
Fever, abdominal pain, watery or bloody diarrhea, occasionally chronic colitis, arthritis. More severe disease in AIDS patients. Guillan-Barre syndrome (post-infection polyneuropathy) is a rare but serious complication.

Comments:
If affected animals are offered for adoption, a written waiver should be signed by adopters.

For more information:
Visit the CDC's Disease Information site: Campylobacter infections

References

Chomel B, Arzt J. Dogs and Bacterial Zoonoses: WHO/PAHO Collaborating Center on New and Emerging Zoonoses
School of Veterinary Medicine, University of California, Davis, 1999.

Greene C. Infectious diseases of the dog and cat: W. B. Saunders Company, 1998.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Willard MD. Gastrointestinal zoonoses. Veterinary Clinics of North America. Small Animal Practice 1987;17:145-178.

Hydatid disease

Disease name: Hydatid disease

Type of agent: Cestode tapeworms

Disease agent: Echinococcus granulosus, Echinococcus multilocularis

Shelter speciesmost commonly infected: Dogs

Clinical signs in affected animals: Asymptomatic

Diagnosis in animals:
Eggs can be seen on fecal floatation. They can be readily distinguished from eggs of the more common tapeworm seen in dogs, Diplydium caninum. However, they can be difficult to differentiate from Taenia spp. ova, which can also infect dogs.

Transmission between animals:
Dogs, jackals and wolves are the definitive host of E. granulosis. Dogs and foxes are definitive hosts of E. multilocularis. Dogs become infected by ingesting the intermediate host: sheep, goats and some wild ruminants (including deer) for E. granulosis, and rodents for E. multilocularis. Dogs most at risk, therefore, are those that are likely to hunt rodents or scavenge sheep, deer or other livestock carcasses.

Transmission to humans:
Ingestion of ova shed in feces of infected dogs. Human infection is uncommon. E. Granulosis is primarily seen in Alaska and Western United States, and E. multilocularis is more common in North-Central United States.

Clinical disease in humans:
Although uncommon, this disease is included because it is potentially fatal and may be on the increase. Infection with E. granulosis leads to formation of tumor-like "hydatid cysts". These cysts form most commonly in the liver, lungs or central nervous system, and can grow very large, causing organ dysfunction through mechanical pressure. Surgical removal is the most common treatment, but spread to other organs is possible.

Prevention:
Any suspect animal should be treated with an agent effective against tapeworms, such as praziquantal. In areas where the disease is known to occur or where animals are very likely to be exposed, prophylactic treatment is appropriate. Disinfectants, including bleach, are ineffective at destroying ova in the environment.

For more information:
Visit the CDC's Disease Information site: Hydatid disease

Eckert J, Conraths FJ, Tackmann K. Echinococcosis: an emerging or re-emerging zoonosis? Int J Parasitol 2000;30:1283-94.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Giardiasis

Disease name: Giardiasis

Type of agent: Flagellated protozoan

Disease agent: Giardia spp.

Shelter speciesmost commonly infected:
Dogs (reported prevalence up to 25-36% in dogs with diarrhea), cats.

Clinical signs in affected animals:
Commonly asymptomatic. May cause diarrhea with or without blood or mucous in the stool. Diarrhea may be chronic or intermittent. Weight loss, anorexia and listlessness may occur.

Diagnosis in animals:

• Demonstration of motile trophozoites on fresh fecal smear, or detection of cysts on zinc-sulfate fecal flotation (using a centrifugation technique). Cyst excretion can be intermittent, so fecal exams should be repeated several times over the course of a week to increase the likelihood of detecting disease.
• In-house ELISA tests are available, and are much more sensitive than ordinary non-centrifugation fecal float techniques.
• Immunoassays are available to detect Giardia antigen in feces - samples must be submitted to a commercial laboratory.
  

Transmission between animals:
Shed in feces, can be carried widely by water, other fomites, including on the fur of infected animals.

Transmission to humans:
Humans are much more likely to be infected with Giardia from a contaminated water source than from an infected pet. However, it is known that the same species of Giardia can infect domestic animals and humans, so precautions should be taken when handling infected animals. Transmission is by direct or indirect fecal-oral route.

Clinical disease in humans:
Gastrointestinal signs, including diarrhea, nausea, anorexia and abdominal cramps.

Comments:
If affected animals are offered for adoption, a written waiver should be signed by adopters.

Prevention:
Any animal diagnosed with Giardia should receive appropriate treatment. No treatment for giardia is 100% effective, so it is important to recheck fecal samples after treatment to ensure that the animal is no longer shedding. Dogs may be re-infected from cysts surviving in their hair or in their environment, so infected dogs should be bathed concurrent with treatment, and their environment thoroughly cleaned. Cysts can survive in moist environments for extended periods; however, quaternary ammonium compounds commonly used in shelters are an effective disinfectant, as is 1% bleach.

For more information:
Visit the CDC's Disease Information site: Giardiasis

Hookworm (Ancylostomiasis)

Disease name: Hookworm (Ancylostomiasis)

Disease name in humans: Cutaneous Larva Migrans

Type of agent: Nematode roundworms

Shelter speciesmost commonly infected: Dogs, cats,

Clinical signs in affected animals:
Commonly cause no signs. Heavy infestation can lead to anemia. Skin lesions also possible: spongy, soft footpads, pruritic (itchy) rash on the chest, sternum and ventral abdomen and other skin surfaces in contact with the ground.

Diagnosis in animals: Characteristic eggs identified on fecal floatation.

Transmission between animals:
Trans mammary transmission in milk from infected bitch, ingestion of eggs from soil or other matter contaminated by infected dog feces.

Transmission to humans:
Ingestion or direct penetration of skin or mucous membranes.

Clinical disease in humans:
Cutaneous larva migrans is a linear, red, intensely itchy rash caused by larvae migrating beneath the skin. Can also cause "Eosinophilic enteritis" characterized by abdominal pain and cramping.

Prevention:
Prevention is the same as described above for roundworm (Toxocara spp), including anthelminthic treatment of all incoming puppies and nursing bitches. Hookworm eggs are less resistant than roundworm eggs, and can be destroyed by freezing, 1% bleach following thorough cleaning of non-porous surfaces, or sodium borate at 10 pounds per 100 square feet for gravel and dirt (will kill vegetation).

For more information:
Visit the CDC's Disease Information site: Hookworm (Ancylostomiasis)

Bowman D. Georgi's parasitology for veterinarians. 7th ed. Philadelphia: W.B. Saunders company, 1999.

Roundworm (Toxocariasis)

Disease name: Roundworm (Toxocariasis)

Disease name in humans: Visceral and ocular larva migrans.

Type of agent: Nematode roundworm

Disease agent: Family Ascaridae, most commonly Toxocara canis

Shelter speciesmost commonly infected: Dogs, cats, raccoons.

Clinical signs in affected animals:
Worms are present in the GI tract and commonly cause no signs. A heavy infection can cause diarrhea, and adult worms may be seen in feces.

Transmission between animals:
Transplacental infection in utero (dogs only), transmammary transmission in milk from infected bitch, ingestion of eggs from soil or other matter contaminated by infected dog feces, ingestion of larvae in tissue of infected paratenic (accidental) hosts such as rodents.

Transmission to humans:
Ingestion of eggs from soil or other matter contaminated by infected dog feces. Puppies and kittens are much more likely to pass eggs in feces than are adult animals. Children are at highest risk of becoming infected.

Clinical disease in humans:
Larvae migrate through the body of the accidental human host, so clinical signs depend on the organ affected. Respiratory signs are common, but other systems may also be involved, including the liver, heart and central nervous system. The disease is usually self-limiting, but can be severe or even fatal, especially when the heart or central nervous system is infected. In the ocular form of the illness, the larvae migrate to the eye and can occasionally cause blindness.

Prevention and control:
Because transmission is possible before birth (in puppies) and in the mother's milk, virtually all puppies and kittens are infected very early in life. Once in the environment, roundworm eggs are extremely resistant to disinfection and extremes of temperature, and may persists for years. The best prevention is therefore to treat all puppies and kittens with an anthelminthic effective against roundworms. The Center for Disease control recommends treating puppies at 2, 4, 6 and 8 weeks of age; kittens should be treated at 6, 8 and 10 weeks of age6. For all puppies and kittens under the age of 16 weeks with an unknown treatment history, at least 2 treatments should be given, 2 weeks apart. Pregnant and nursing mothers should also be treated. Pyrantel pamoate is commonly used for this purpose in shelters (trade names include Nemex® and Strongid®). Many other drugs are also effective.

Eggs passed in feces are not immediately infective; therefore feces should be removed on a daily basis from all dog and cat play areas, cages and runs. Puppy play areas, in particular, should have a surface from which all organic material may easily be cleaned, or a surface that is periodically replaced to decrease the inevitable build-up of infective agents in the environment.

Comments:
Shelters that keep puppies and kittens for more than two weeks should develop a system to identify animals needing repeat deworming treatment (this may be given in conjunction with booster vaccinations). Adopters should be specifically advised of the risk of roundworm infection and the very high prevalence of this condition in young animals, whether from a shelter or any other source. Shelters should provide written and verbal advice to new owners emphasizing the importance of anthelminthic treatment for their new pet.

For more information:
Visit the CDC's Disease Information site: Visceral and ocular larva migrans.
For more information on effective treatments see : Preventive Anthelmintic Treatments

Bowman D. Georgi's parasitology for veterinarians. 7th ed. Philadelphia: W.B. Saunders company, 1999.

Glickman LT. Zoonotic Visceral and Ocular Larva Migrans. Veterinary Clinics of North America. Small Animal Practice 1987;17:39-54.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Wilson JF, Lacroix C, Allert C. Zoonotic parasitic diseases: a legal and medical update. Veterinary Forum 1996:40-46.

Salmonellosis

Disease name: Salmonellosis

Type of agent: Gram negative rod shaped bacteria

Disease agent: Salmonella spp.

Shelter speciesmost commonly infected:
Reptiles, many other species, including dogs, cats, birds and livestock

Clinical signs in affected animals:
Most commonly asymptomatic. Can cause fever, anorexia, vomiting and diarrhea with or without blood and mucous, in severe cases leading to septicemia and death. Severe cases can resemble panleukopenia or parvo. Cats that prey on birds may develop "song bird fever", acute salmonella infection causing severe, often bloody diarrhea following ingestion of infected birds. Shedding of Salmonella can persist for as long as 6 weeks after clinical recovery. Up to 90% of reptiles are asymptomatic chronic carriers.

Diagnosis in animals:
Fecal culture. Intermittent shedding is possible so 3 negative fecal cultures at two week intervals are required to call an animal free of salmonella.

Transmission between animals:
Fecal-oral spread directly, in contaminated water, food or on fomites such as food dishes and grooming implements. Free roaming cats and dogs at increased risk for exposure. Risk of infection increased by stress, poor nutrition (including overfeeding), overcrowding, antibiotic therapy and surgery. Spread from infected humans to animals is possible.

Transmission to humans:
Fecal-oral route from surfaces, food or water contaminated by feces, or handling of infected animals, especially reptiles. Most common source is food-borne, but infected animals are significant risk.

Clinical disease in humans:
Abdominal cramps, nausea, vomiting and diarrhea. Can cause severe and occasionally fatal disease, especially in very young children and immunocompromised individuals.
Prevention: Routine hygiene and sanitation. Hand washing after handling reptiles or any animal with diarrhea should be emphasized. Salmonella is quite durable in the environment and can survive for weeks under hospitable conditions, but is destroyed by most commonly used disinfectants.
Comments: The Center for Disease Control recommends "written point-of-sale education provided to consumers on the risks for and prevention of reptile-associated salmonellosis". Shelters should consider providing such guidelines to people adopting reptiles. Reptiles are not recommended as pets for immunocompromised people because of the threat of salmonellosis.

For more information:
Visit the CDC's Disease Information site: Salmonellosis

Chomel B, Arzt J. Dogs and Bacterial Zoonoses: WHO/PAHO Collaborating Center on New and Emerging Zoonoses
School of Veterinary Medicine, University of California, Davis, 1999.

Greene C. Infectious diseases of the dog and cat: W. B. Saunders Company, 1998.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Willard MD. Gastrointestinal zoonoses. Veterinary Clinics of North America. Small Animal Practice 1987;17:145-178.

Toxoplasma gondii

Disease name: Toxoplasmosis

Type of agent: Protozoal coccidium

Disease agent:Toxoplasma gondii

Shelter speciesmost commonly infected: Cats

Clinical signs in affected animals:
Usually asymptomatic. Recent infection may cause transient fever, diarrhea or respiratory signs. Symptoms more likely in young kittens and cats with concurrent disease. Occasionally causes chronic or more severe disease, including neurological and ocular disease.

Diagnosis in animals:
Serology can be performed to determine whether a cat has ever been exposed to toxoplasmosis, but is of little practical value. Cats may shed infectious oocysts before developing antibodies to toxoplasma, and the vast majority of cats that are positive on serology are not shedding oocysts. Oocysts may be detected on fecal floatation, although it is impossible to differentiate these from the oocysts of certain other protozoan parasites. Absence of oocysts in fecal floatation should not be used to rule out disease.

Transmission between animals:
Cats are the only domestic species that shed infectious oocysts in feces. Cats may become infected through ingestion of oocysts or ingestion of infected intermediate hosts such as rodents. Transmission to kittens through mother's milk is also possible. Most cats become infected in the first year of life, and oocyst shedding is usually highest at the time of first infection.

Transmission to humans:
The most common mode of human infection is through ingestion of intermediate stages of toxoplasma in undercooked meat. Humans may also become infected by ingestion of oocysts from soil contaminated by cat feces, usually following gardening or ingestion of raw vegetables from such soil. Transmission by the fecal-oral route after exposure to cat feces is also possible, usually when cleaning litter boxes. Shelters commonly contain a large, non-immune population of young cats with the potential to experience initial infection and shed the organism in large quantities, which could increase the risk of spread by ingestion of oocysts.

Clinical disease in humans:

1. Usually asymptomatic in immunocompetent adult, may cause transient flu-like symptoms and swollen lymph nodes.

2. Can cause abortion or severe congenital disease in infants, especially when pregnant mothers are infected between the 2nd and 6th month of gestation. May cause acute systemic illness at birth, with respiratory, neurological, liver and spleen being among the organs affected. Most common long term problems in congenitally affected children are blindness, decreased IQ and hearing impairment.

3. May cause severe disease in immunocompromised patient, most often causing neurological signs including headache, seizures, cognitive impairment and partial paralysis. This usually represents reactivation of latent infection rather than new infection.

Prevention:
Since most infections are not transmitted by direct contact with cats or cat feces, the best prevention for the general public is to cook meat properly, wash vegetables thoroughly or peel before eating, and wear gloves when gardening. To prevent transmission from cat feces, litter boxes should be changed and thoroughly cleaned daily with hot water and disinfectant . This is particularly important in group cat rooms in shelters to prevent extensive cat-to-cat transmission. Pregnant women should not handle cat litter. Pregnant women may consider getting tested for antibodies to toxoplasma; if negative, retesting during pregnancy to detect new infection should be discussed with the physician.

Comments:
Shelters may consider offering serologic testing for female employees of child-bearing years at start of employment. Employees testing negative should be warned of the risk of contracting toxoplasmosis during pregnancy.

For more information:
Visit the CDC's Disease Information site: Toxoplasmosis

Cheyletiellosis (Walking Dandruff)

Disease name: Cheyletiellosis (Walking Dandruff)

Type of agent: Arachnid mite

Disease agent: Cheyletiella spp.

Shelter speciesmost commonly infected: Cats, rabbits,dogs

Clinical signs in affected animals:
Variable; range from mild scaling and crusting along dorsum (back) without itching, to intensely itchy dermatitis with rash and hair loss. Cats may present with excessive grooming without obvious rash.

Diagnosis in animals:
Direct examination of animal with powerful magnifying class, scotch tape prep, microscopic examination of hair and scale collected by flea comb, identification of mite eggs on fecal floatation. None of these diagnostic techniques will be positive in all cases; therefore presumptive diagnosis may be made based on clinical signs and response to treatment.

Transmission between animals:
Direct contact or spread on fomites, such as blankets and grooming tools. Eggs shed on hair into environment may serve as source of spread or re-infestation. Easily transmitted, especially between young animals.

Transmission to humans:
Most commonly direct contact with infested animals.

Clinical disease in humans:
Itchy, red, raised rash, most often on arms, legs or trunk. Self limiting if no environmental source of re-infestation.

Prevention:
Prevention in a shelter ideally includes prophylactic application of topical flea control products such as fipronil (Frontline®) or imidicloprid (Advantage®) to every incoming animal, as these flea products may also be effective in eliminating Cheyletiella infection. If cost is prohibitive, topical flea control products may be administered to those animals with skin rash, hair loss or other signs of infestation with fleas or mites at intake. If Cheyletiella is diagnosed, the infested animal and all in-contact animals should receive appropriate treatment. Weekly application of a variety of pesticides is reported to be effective. In areas where thorough mechanical cleaning is possible (i.e. stainless steel cages), environmental treatment beyond normal disinfection procedures is probably not necessary. However, mites can survive in home-like environments for some time (i.e. group cat rooms, foster homes), and these areas should be treated with environmental flea control products.
Considerations for shelters: Because of the possibility of human infection and environmental contamination, infested animals should not be placed in homes until treatment has been completed and cure has been microscopically confirmed.

Comments:
If affected animals are offered for adoption, a written waiver should be signed by adopters.

For more information:
Visit the Merck Veterinary Manual site: Cheyletiellosis

Moriello KA. Treatment of Sarcoptes and Cheyletiella Infestations. In: R. W. Kirk and J. D. Bonagura, eds. Kirk's Current Veterinary Therapy XI: Small Animal Practice.

Muller G, Scott DW, Griffin CE. Muller and Kirk's small animal dermatology. 6th ed. philadelphia: W.B. Saunders Company

Scott DW, Horn RT. Zoonotic Dermatoses of Dogs and Cats. Veterinary Clinics of North America. Small Animal Practice 1987;17:117-144.

Ringworm (Dermatophytosis)

Disease name: Ringworm (Dermatophytosis)

Type of agent: Filamentous Fungi

Disease agent: Microsporum caninum (most common species), Trichophyton mentagrophytes

Shelter speciesmost commonly infected: Cats, dogs (young animals, Persian cats and Yorkshire terriers at greater risk).

Clinical signs in affected animals:
Most common: circular area of hair loss and scaling. Most common location is face, ears, feet and tail. Wide range of presentations possible, including hair loss with or without crusting, nail bed infection, infection that mimics "stud tail" and feline acne, and generalized infection. Asymptomatic carriage of ringworm is possible.

Diagnosis in animals:
Definitive diagnosis requires fungal culture and microscopic identification. Woods lamp detects about 50% of Microsporum cases; can be used for screening procedure but can't be relied on for diagnosis. Direct microscopic examination of hairs likewise can be used to make a positive diagnosis, but often fails to detect the presence of ringworm.

Transmission between animals:
Direct contact, contaminated environment, or spread by fomites. May be spread to animals from infected humans.

Transmission to humans:
Direct contact, contaminated environment or contact with fomites.
Clinical disease in humans: Ring shaped areas of scaling and hair loss, with or without redness, crusting and itching.

Clinical disease in humans:
Ring shaped areas of scaling and hair loss, with or without redness, crusting and itching.

Prevention:

1. Recognition:
Ringworm is extremely persistent in the environment and is not destroyed by any disinfectant at concentrations routinely used in shelters. The best prevention is early recognition to limit environmental contamination. Kittens and cats should be carefully examined at intake, and examined by Woods lamp before being sent to foster care or placed in group housing situations. Suspected lesions should be cultured, and animals treated as positive until culture results are available.

2. Care in the shelter:
Positive or suspect animals should be isolated and handled with protective clothing. Toys and blankets should be reserved for the affected animal and discarded after use. Contaminated surfaces and implements should be cleaned with bleach diluted to 1:10. Contaminated cages should be allowed to sit open for 24 hours and cleaned again with bleach prior to reuse. All treatments (such as clipping and dipping) should be performed in an easy to clean area, separate from areas where other medical procedures are performed and from where sick animals are housed. Clippers used for affected animals should be reserved for that purpose. If animals are housed and treated in the shelter or in foster homes, clipping and topical therapy is indicated to reduce environmental contamination.

3. Decontamination of environment:
Environmental decontamination is essential to prevent recurrence of the disease. Without aggressive cleaning spores may persist and remain infectious for years. All surfaces, vents, heating ducts, etc. must be cleaned, using bleach diluted at 1:10 where-ever possible.

For more information:
Visit our ringworm information page

References

Moriello KA, DeBoer DJ. Feline dermatophytosis. Recent advances and recommendations for therapy. Veterinary Clinics of North America. Small Animal Practice 1995;25:901-21.

Muller G, Scott DW, Griffin CE. Muller and Kirk's small animal dermatology. 6th ed. philadelphia: W.B. Saunders Company

Scott DW, Horn RT. Zoonotic Dermatoses of Dogs and Cats. Veterinary Clinics of North America. Small Animal Practice 1987;17:117-144.

Sarcoptic mange (Scabies)

Disease name: Sarcoptic mange (Scabies)

Type of agent: Arachnid mite

Disease agent: Sarcoptes scabiei var. canis (canine scabies)
Notoedres Cati (feline scabies)

Shelter speciesmost commonly infected: Dogs, cats

Clinical signs in affected animals:
Canine: Intense itching, rash, reddened, crusty skin, and hair loss typically affecting the ear flaps, elbows, ventral abdomen and chest, and legs. The dorsum (back) is rarely affected.
Feline: Intense itching, followed by reddened, raised rash usually affecting the ears, face, neck, feet and perineum.

Diagnosis in animals:
Definitive diagnosis is made by demonstration of mites on skin scraping. However, negative scrapings are common in dogs with scabies. Multiple scrapings should be performed, and scabies suspected in any dog with characteristic clinical signs even in the absence of a positive scraping. Skin scrapings are usually positive in affected cats.

Transmission between animals:
Close contact with infected animals or environment. Fomite transmission possible but uncommon. Individually kenneled dogs pose little risk of infection for other dogs as long as direct contact is prevented. More readily transmitted between cats, especially those housed together.

Transmission to humans:
Close contact with infected animals.

Clinical disease in humans:
Itchy, raised rash (papules, pustules or crusts) in pet-contact areas of skin, usually arms, legs, abdomen or chest. Skin scrapings in humans are frequently negative, so it is important to tell heath care providers about suggestive history. Usually self-limiting.

Prevention of sarcoptic mange:
Affected animals and all same-species animals that have been in direct contact should receive appropriate treatment. Treatment options are available that are less labor intensive than the traditional dips and may be more practical in a shelter setting, including ivermectin and selamectin (Revolution®) at appropriate doses. Protective clothing should be worn when handling infested animals. Mites do not survive longer than a few days under normal indoor conditions, but survival is increased in cool and humid conditions. In cases involving multiple infested animals or where infestation recurs, treatment of contaminated areas with an environmental flea control product is recommended.

Considerations for shelters :
Because of the possibility of human infection and environmental contamination, infested animals should not be placed in homes until treatment has been completed and cure has been microscopically confirmed.

For more information:
Visit the CDC's Disease Information site: Scabies

Moriello KA. Treatment of Sarcoptes and Cheyletiella Infestations. In: R. W. Kirk and J. D. Bonagura, eds. Kirk's Current Veterinary Therapy XI: Small Animal Practice. Philadelphia: W.B. Saunders, 1992;558.

Muller G, Scott DW, Griffin CE. Muller and Kirk's small animal dermatology. 6th ed. philadelphia: W.B. Saunders Company

Scott DW, Horn RT. Zoonotic Dermatoses of Dogs and Cats. Veterinary Clinics of North America. Small Animal Practice 1987;17:117-14

Bartonellosis (Cat Scratch Fever)

Disease name: Bartonellosis (Cat Scratch Fever)

Type of agent: pleiomorphic gram negative bacterium

Disease agent: Bartonella henselae

Shelter speciesmost commonly infected:
Cats (kittens at increased risk for transmitting disease, shelter cats at increased risk compared to other cats).

Clinical signs in affected animals:
Almost always asymptomatic. Experimental infection causes transient febrile illness.

Diagnosis in animals:
Blood culture is the only way to document bacteremia. Serology does not correlate with bacteremia. Many seropositive cats will not be bacteremic, and 2% of seronegative cats can be bacteremic.

Transmission between animals:
Transmitted by flea bites. Cat to cat transmission does not occur in the absence of fleas.

Transmission to humans:
Cat scratch or bite, most likely transmitted by contaminated flea dirt inoculated into wound. Other close contact with cats/fleas may transmit disease as well.

Clinical disease in humans:
Immunocompetent: Children most commonly affected. Most common symptom is painful, markedly swollen lymph nodes 1-3 weeks after exposure. May be accompanied by flu-like symptoms of fever, anorexia, chills and headache. Lesion resembling an insect bite at site of inoculation (scratch or bite) is common. Usually self limiting. Severe complications include meningitis and encephalitis.

Clinical disease in immunocompromised humans:
A more serious syndrome occurs in immunocompromised patients, called "bacillary angiomatosis" (BA). BA causes multiple, blood filled cystic nodules on the skin. It can also affect internal organs including the liver and spleen, and is a common cause of neurologic deterioration and dementia in AIDS patients.

Prevention:
Since fleas are considered essential for transmission, flea control is key to limiting spread of this disease. All incoming cats should be treated with a topical flea product, and severely infested animals should receive additional treatment such as bathing if needed. All bites and scratches should be promptly and thoroughly washed with soap and water. Kittens are at much higher risk of transmitting the disease, so immunocompromised persons should be encouraged to adopt cats older than 1 year.

For more information:
Visit the CDC's Disease Information site: Bartonellosis or visit the the Winn Foundation's health article on Cat Scratch Disease.

Chomel B, Arzt J. Dogs and Bacterial Zoonoses: WHO/PAHO Collaborating Center on New and Emerging Zoonoses
School of Veterinary Medicine, University of California, Davis, 1999.

Greene C. Infectious diseases of the dog and cat: W. B. Saunders Company, 1998.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Willard MD. Gastrointestinal zoonoses. Veterinary Clinics of North America. Small Animal Practice 1987;17:145-178.

Dog and cat bites

Nationally, 90% of bites are from dogs, 6% from cats, and 4% from other species. An estimated 3-5% of dog bites and 20-50% of cat bites become infected. Risk of infection is highest for crush and puncture wounds. Most bite wound infections are a mix of aerobic and anaerobic bacteria from the animal's mouth and the victim's skin.

Type of agent: Two infectious agents account for the majority of serious complications:

1. Pasteurella spp.
   1. More commonly found infecting cat bites than dog bites.
   2. Wound becomes very swollen, red and painful within 24 hours of bite (often within 3-6 hours).
   3. Severe complications and systemic spread possible if not treated; complications include cellulitis, arthritis and tendonitis. Septic shock is possible, especially in immunocompromised patients.
      
      
2. Capnocytophaga canimorsus
   1. More commonly found infecting dog bites than cat bites.
   2. Signs of infection may not appear for 24 hours to several weeks post-bite.

Bite prevention/response:

• Provide training to allow staff and volunteers to handle animals safely, and handling equipment such as muzzles, squeeze cages, pole syringes and control poles.
• Ensure that animals are properly restrained and/or sedated for exams and procedures, and that adequate staff is available for this purpose.
• All bites should be thoroughly washed with soap and water, and irrigated with saline or an appropriate disinfectant. A 20 gauge needle attached to a syringe can be used. Prompt cleaning can help prevent transmission of zoonotic disease as well as infection.
• All staff and volunteers should be aware of reporting procedures for a bite, and these should be clearly posted in appropriate locations.
• Required quarantine procedures should be followed (see comments under rabies section).
• Ensure that the victim receives appropriate medical attention, including tetanus prophylaxis and rabies prophylaxis if indicated.
  

For more information:
Visit the CDC's Bite wound Information site

Chomel B, Arzt J. Dogs and Bacterial Zoonoses: WHO/PAHO Collaborating Center on New and Emerging Zoonoses

Greene C, Goldstein EJC, Wright JC. Bite wound infections In: C. Greene, ed. Infectious diseases of the dog and cat. 2nd ed. Philadelphia: W.B. Saunders, 1998;330-335.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Underman A. Bite wounds inflicted by dogs and cats. Veterinary Clinics of North America. Small Animal Practice 1987;17:195-208.

Rabies

Disease name: Rabies

Type of agent: Virus of family Rhabdoviridae, genus Lyssavirus

Disease agent: Rabies virus

Shelter speciesmost commonly infected:
Most warm blooded animals can be infected. Predominant species infected vary by region; most commonly infected species in United States are bats, skunks, raccoons, foxes and coyotes. Although vaccination is highly effective, it is not 100% protective; vaccinated dogs and cats have been reported to develop rabies.

Clinical signs in affected animals:
Two presentations, "furious" form and "dumb" or paralytic form. Furious form characterized by aggression, disorientation, anxiety, and roaming. Paralytic form characterized by progressive paralysis, often starting with the throat muscles, leading to an inability to swallow and hypersalivation. Licking at site of wound inoculation is common early in disease. Atypical presentation is possible, and rabies should be kept in mind as a differential for any abnormal behavior or neurological disease of unknown cause. Hydrophobia is characteristic of human infection, but is not generally seen in animals.

Diagnosis in animals:
Infected dogs, cats and ferrets will show clinical signs of rabies within 10 days of the time virus is present in the saliva, which forms the rationale for the quarantine period. Definitive diagnosis is by post-mortem immunofluorescent antibody testing of brain tissue.

Transmission between animals
Bite or ingestion of an infected animal.

Transmission to humans:
Saliva generally needs to enter tissue for infection to occur, so a bite that breaks the skin is by far the most common means of transmission. Rabies may also be contracted through a scratch, and cases have been documented following aerosol exposure of spelunkers in bat-infested caves, and slaughterhouse workers exposed to infected carcasses.

Clinical disease in humans:
Incubation period is usually from 3 weeks to 3 months, but may be as long as several years. Symptoms start as a flu-like illness, often accompanied by pain at site of original wound, progressing to neurological signs, including altered behavior, paralysis, coma and death. Hydrophobia and aerophobia may be seen in humans. Once clinical signs have become apparent, rabies is virtually 100% fatal.

Prevention:

• All bites should be reported, and the appropriate quarantine or testing performed. Local or state public health department should be contacted for specific quarantine and sample submission guidelines. Dogs, cats and ferrets may be quarantined for 10 days under normal circumstances; there is no accepted quarantine period for wildlife species or exotic pets.
• If staff is responsible for decapitating animals for sample submission, appropriate protective clothing should be worn, including gloves and goggles.
• Bite wounds should be immediately and thoroughly cleaned with soap and water.
• Post-exposure treatment consists of rabies immunoglobulin and a series of intramuscular rabies vaccinations. The need for post-exposure treatment should be determined by a physician and depends on the species, circumstances, and location of the bite.
• Animal control workers in rabies epizootic areas are considered to be in a high risk category. The Center for Disease Control recommends pre-exposure vaccination with human diploid cell vaccine and serologic testing every 2 years to ensure adequate antibody levels for these workers. For animal control workers in areas with infrequent rabies, pre-exposure vaccination is also recommended, but serologic testing is not required. Pre-exposure vaccination may also be indicated for other staff depending on amount of animal handling performed.
  

For more information:
Visit the CDC's Rabies Information site or visit the National Association of State Public Health Veterinarians website where you may download the Compendium of animal rabies prevention and control for 2005

Kennel cough (Bordetellosis)

Disease name: Kennel cough (Bordetellosis)

Type of agent: Gram negative bacteria

Disease agent: Bordetella bronchiseptica

Shelter speciesmost commonly infected:
Dogs, cats

Clinical signs in affected animals:
Usually causes harsh cough with or without retching without signs of systemic illness. Cases complicated by primary or secondary infection with other agents may present with cough, nasal or ocular discharge, and systemic signs such as fever and anorexia. May progress to pneumonia in severe cases.

Diagnosis in animals:
Usually based on clinical signs and rule out of more serious conditions. Bacterial culture can be performed of nasal or transtracheal swab; transtracheal swab results more likely to indicate clinically significant infection.

Transmission between animals:
 Direct contact, airborne spread or transmission on fomites

Transmission to humans:
Bordetella is not considered to be a zoonotic risk to immunocompetent individuals. However, it may cause infection in immunosuppressed people or those suffering from pre-existing respiratory disease. Kennel cough associated with clinical bordetellosis is extremely common in sheltered dogs, so although transmission to humans is uncommon, shelter staff should be aware that certain groups are at risk.

Clinical disease in humans:
Respiratory infection most common.

Prevention:
Dogs with kennel cough should receive appropriate treatment, and isolated from the general population if facilities permit. Bordetella is not particularly durable, and routine disinfectants are adequate to destroy this bacteria. Immunosuppressed people or those with respiratory conditions should be advised not to adopt dogs with current or recent kennel cough, since shedding may continue for several months after recovery.

Comments:
If affected animals are offered for adoption, a written waiver should be signed by adopters.

For more information:
Visit our Kennel cough treatment protocol

References

Ford R. Bordetella bronchiseptica has zoonotic potential. Top Vet Med 1995;6:18-22.

Greene C. Infectious diseases of the dog and cat: W. B. Saunders Company, 1998.

Gueirard P, Weber C, Le Coustumier A, et al. Human Bordetella bronchiseptica infection related to contact with infected animals: persistence of bacteria in host. J Clin Microbiol 1995;33:2002-6.

Leptospirosis

Type of agent: Gram negative spirochete bacteria

Disease agent: Leptospira spp; multiple serovars

Shelter speciesmost commonly infected:
Dogs (cats uncommonly affected). Dogs with a history of hunting or exposure to livestock or wildlife are at increased risk. Although leptospirosis is uncommon in dogs, disease in dogs (and humans) appears to be on the increase in recent years.

Clinical signs in affected animals:
Commonly asymptomatic. Severe cases can cause vomiting, depression, anorexia, fever, ocular and nasal discharge/coughing, kidney and liver disease, severe depression and death.

Diagnosis in animals:
Serology (blood samples sent to diagnostic lab). May be negative in first week to ten days of disease, so suspect cases should be treated as positive until confirmed otherwise. Recent vaccination for leptospirosis may cause false positive results on serology. PCR test has been developed and may be available from selected labs.

Transmission between animals:
The infectious agent is primarily present in urine. The most common route of infection is through contact with water or soil contaminated by the urine of infected livestock or rodents. Outbreaks can occur during periods of flooding. Infected dogs can shed bacteria intermittently in urine for months even after recovery; direct transmission from urine or aborted tissue may occur and is increased in crowded kennel situations. Free roaming cats and dogs are at increased risk for exposure.

Transmission to humans:
Human cases most commonly result from exposure to contaminated water, but an increasing number have been attributed to exposure to domestic animals. Transmission occurs via skin break or mucous membrane contact. Urine and aborted tissue from infected animals can be highly infectious to humans. Infection and shedding in urine can occur in healthy appearing, vaccinated dogs.

Clinical disease in humans:
Wide range of symptoms, from mild febrile disease with transient rash on palate and skin, to severe disease including liver and kidney failure, meningitis, hemorrhage, myocarditis, blindness and death in a small percentage of cases. Infection during pregnancy can cause fetal death.

Prevention:
The most important step shelters can take to prevent spread of disease to humans is to treat all urine as potentially infectious. Gloves and goggles should be worn when hosing out kennels, and whenever handling suspect dogs or urine. Iodophor disinfectants are highly effective against Leptospira. Vaccination is available for dogs; an effective vaccination protocol should be discussed with a local veterinarian or veterinary school. Vaccination of shelter dogs should not be considered to protect human health, as infection has been documented in vaccinated animals, and vaccination is never immediately protective.

Comments:
Because shedding can continue for an extended period, dogs with a known recent history of leptospirosis should not be housed in an animal shelter unless strict isolation is possible. Shelters must carefully consider the possible liability of adopting out a dog with a potentially severe zoonotic condition.

For more information:
Visit the CDC's Disease Information site: leptospirosis

Chomel B, Arzt J. Dogs and Bacterial Zoonoses: WHO/PAHO Collaborating Center on New and Emerging Zoonoses
School of Veterinary Medicine, University of California, Davis, 1999.

Greene C. Infectious diseases of the dog and cat: W. B. Saunders Company, 1998.

Palmer SR, Soulsby, Simpson. Zoonoses: Biology, Clinical Practice, and Public Health Control. New York: Oxford University Press, 1998.

Willard MD. Gastrointestinal zoonoses. Veterinary Clinics of North America. Small Animal Practice 1987;17:145-178.