Common Infectious Diseases of Raccoons
Raccoons are susceptible to a large number of different
infectious agents including bacteria, viruses, and parasites.
Several of these infectious diseases are zoonotic. Veterinarians
are faced with the diagnosis and treatment of wildlife including
raccoons and need to be able to make the correct diagnosis
as well as educate clients on the potential hazards associated
with exposure to raccoons.
Leptospirosis is a common bacterial disease in raccoons
caused by a number of different species of Leptospira.
Transmission is thought to occur via urine contamination
of feed and water. Antemortem diagnosis is based upon
serology and dark field examination of urine. Histopathologic
examination and fluorescent antibody testing of liver and
kidney are two postmortem procedures that can be done to
help further aid the diagnosis of leptospirosis. Other
natural bacterial infections reported in raccoons
are listeriosis,yersiniosis,pasteurellosis, and tularemia.
Viral diseases of raccoons include rabies, canine distemper,
raccoon parvoviralenteritis, infectious canine hepatitis,
and pseudorabies. Rabies is a zoonotic disease that is endemic
in raccoon populations in Pennsylvania
and New England. In recent years,
there has been a shift of rabies infected raccoons westward
(see Diagnostic Forum Vol. 8, No 2, 1997).
Canine distemper virus infection is probably the most common
viral disease in raccoons. The clinical signs, and gross
and histopathologic lesions in raccoons are similar to distemper
in dogs. Neurologic signs due to distemper virus infection
in raccoons are virtually indistinguishable from rabies
induced neurologic disease. Diagnosis is based upon
histopathologic lesions in brain, lung, spleen, and small
intestine. Intranuclear and intracytoplasmicinclusion bodies
can be visualized in many cells including epithelial cells
in the respiratory epithelium, gastric mucosa, and transitional
epithelium lining the renal pelvis and urinary bladder.
The best tissues for fluorescent antibody testing and virus
isolation of canine distemper virus are lung, brain, stomach,
small intestine, kidney, and urinary bladder.
Parvoviral enteritis in raccoons is due to a unique raccoon
parvovirus that is most antigenically similar to feline
parvovirus. Clinical signs include bloody diarrhea, lethargy,
inappetance, and loss of fear of humans. Raccoons do not
develop clinical disease when exposed to canine parvovirus.
Diagnosis is based upon histopathologic lesions of necrotizing
enteritis and identification of the virus by fluorescent
antibody testing. The most common method in which raccoons
acquire pseudorabies virus infection is via the ingestion
of virus-infected pig carcasses.
An important parasitic disease of raccoons is toxoplasmosis,
which is a protozoal disease caused by Toxoplasmagondii.Felids
are the definitive host for T. gondii, and they excrete
potentially infective oocysts in their feces. Toxoplasmosis
in raccoons is commonly associated with immunosuppression
from canine distemper virus infection. Necrotizing encephalitis
and pneumonitis are frequent lesions associated with toxoplasmosis.
Another parasite of importance in raccoons is Baylisascarisprocyonis,
which is an intestinal roundworm of raccoons. Baylisascaris
is a known cause of cerebral nematodiasis and ocular and
visceral larval migrans in domestic and non-domestic animals,
and humans. Transmission commonly occurs through the ingestion
of infective eggs, which results in aberrant migration in
hosts other than raccoons.
- by Jim Raymond, DVM
- edited by M. Randy White, DVM, PhD