Zoonotic diseases of exotic animals (Proceedings)

With the growing popularity of exotic pets in the United States, the incidence of zoonotic diseases attributed to these pets should be expected to rise. Veterinarians play an important role in educating the public and should have an understanding of the epidemiology of these potentially devastating diseases. The purpose of this presentation is to introduce veterinarians to the most common zoonotic diseases encountered in non-traditional species and review diagnosis, treatment and prevention.

Salmonella spp. are Gram-negative facultative anaerobes that are ubiquitous in the environment. These bacteria have been isolated from all of the different classes of animals. There are over 2,400 different Salmonella serotypes, and they should all be considered pathogenic. Most animals appear to be asymptomatic reservoirs for this microbe. Salmonella sp. is primarily transmitted via the fecal-oral route or from contaminated fomites. Humans that contract salmonellosis from non-traditional species may experience headaches, nausea, vomiting, abdominal pain, enteritis, or septicemia. The incubation of Salmonella in humans is approximately 6-48 hours. Because of the inherent zoonotic risks associated with non-traditional species (e.g., reptiles), ownership should be limited to cases that have adult supervision. Strict hygiene, including hand washing with soap, should be practiced to reduce the risk of exposure.

Chlamydophila psittaci is a bacterial pathogen in psittacines. Affected birds may be asymptomatic or develop intense systemic disease, including pneumonia, splenitis, and hepatitis. This pathogen is generally spread via aerosolization. Affected humans may also be asymptomatic or develop severe clinical disease as described in the birds. Birds being introduced into an aviary should be tested for the disease and quarantined.

Campylobacteriosis is a serious zoonosis. Although contaminated food (e.g., poultry) is the primary source of Campylobacter spp., non-traditional small mammals, such as the ferret and hedgehog, may harbor Campylobacter jejuni or C. pylori. The incubation of Campylobacter spp. is approximately 2-5 days. In general, the disease is self-limiting (10-14 days), however, it may persist in the immunocompetent host. Campylobacter-positive ferrets that have recovered from an active infection may shed the bacteria for over 100 days. Humans with compromised immune systems should limit contact with ferrets or other species of animals that have been identified as Campylobacter-positive.

Mycobacterium spp. have a cosmopolitan distribution. Mycobacterium spp. have been isolated from all of the major classes of animals. Many of the Mycobacterium spp. that can infect animals, can also infect humans. Mycobacterium spp. can be transmitted to humans from non-traditional species through aerosolization of contaminated respiratory secretions or direct skin contact. Pet owners should always practice strict disinfection protocols when handling their pets and limit contact when they have open wound on their hands.

Rat-bite fever (RBF) is a rare, but serious, zoonosis caused by Streptobacillus moniliformis and Spirillum minus. These bacteria are generally considered to be indigenous flora in rats. Domestic rats are considered the primary reservoir for RBF and primarily transmit the bacteria through a bite. The incubation for streptobacillary RBF in humans is approximately 3-10 days, while spirillary RBF is 1-6 days. The clinical signs attributed to RBF are generally observed at approximately the same time the bite wound is healing, and include relapsing fever, chills, vomiting, myalgia, and regional lymphadenopathy. Individuals infected with S. moniliformis frequently develop a maculopapular rash on their extremities. The maculopapular rash does not occur with spirillary RBF. Rat-bite wounds should be immediately disinfected to reduce the likelihood of transmitting these bacterial pathogens.

Yersinia pseudotuberculosis is a Gram-negative coccobacilli that is routinely isolated from clinically normal rodents and lagomorphs. Yersinia pseudotuberculosis has been associated with epizootics in rodent and lagomorph colonies worldwide. Affected animals generally experience diarrhea and progressive weight loss. Significant mortalities have been attributed to this bacteria. Although captive rodents have not been identified as an important source of infection for humans, they certainly could serve as competent reservoir of the bacteria in the human environment.

Type A and B influenza viruses are common pathogens of both ferrets and humans. These viruses are generally transmitted via aerosolization. The disease is characterized by a mucopurulent nasal and ocular discharge, sneezing, lethargy, fever, and inappetance. Pneumonia can develop in immunocompromised individuals. Infected animals should be quarantined to minimize the likelihood of transmitting the virus.

Lymphocytic choriomeningitis (LCM) is a viral meningitis in humans associated with an arenavirus. Rodents are considered the primary reservoir for this disease. This virus is transmitted via horizontal and vertical routes in rodents and affected rodents are generally asymptomatic, although clinical disease, including weight loss, photophobia, tremors, and convulsions, may occur. Humans generally become infected from exposure to contaminated feces or urine, or from a bite. Affected humans frequently report clinical symptoms consistent with the flu. Fatal cases are rare. Humans working closely with large populations of rodents should practice strict hygiene and wear protective clothing to reduce the likelihood of exposure.

Cryptosporidiosis is a common zoonotic pathogen. Cryptosporidium parvum does not appear to be host specific. Affected animals may be asymptomatic or present with chronic diarrhea. Individuals with compromised immune systems should limit their contact with Cryptosporidium-positive non-traditional species.

Encephalitozoon cuniculi is an obligate protozoal parasite of rabbits. This parasite is generally transmitted through urine, although vertical transmission can also occur. Infected animals are frequently asymptomatic, but may develop severe neurologic disease. There is no effective treatment for encephalitozoonosis in lagomorphs. This parasite has only recently surfaced as a pathogen in humans.

Sarcoptic mange can infest a number of different mammalian species. Affected animals frequently develop intense pruritis, scales, erythema, and generalized alopecia. Humans can become infected with sarcoptic mange through direct contact with infested animals. Affected animals should be quarantined and only handled with gloves to limit exposure. Lime sulfur shampoos and ivermectin may be used to treat affected animals.

Trichophyton mentagropthytes is an opportunistic fungal disease of mammals. Affected animals may be asymptomatic or present with focal to multi-focal alopecia, including pruritis, crusts, scabs and excoriations. Immunocompetent humans are generally asymptomatic; however, alopecia and crusts may develop in humans with this fungus.

Veterinarians working with exotic animals should familiarize themselves with the common zoonotic diseases associated with the species presented to their practice. Preparing education pamphlets for your owners that remind them to adhere to strict hygiene practices to limit their exposure to zoonotic diseases is also highly recommended.