Rabies (Canine)
| PrintRabies is justifiably one of the most feared infectious diseases known. Once symptoms develop, rabies is incurable and fatal. All warm-blooded animals including humans are susceptible, with dogs and cats being important natural vectors and thus sources of exposure for people. Vaccination is protective. Rabies is reportable.
Common name: Rabies
Scientific name: Rabies
Diagnosis
Signalment
Any age or sex can become infected, but adult animals that have contact with wildlife are at highest risk.
Incidence/prevalence
More than 27,000 cases of animal rabies are reported yearly worldwide, with a much larger number of cases going unnoticed in wildlife. Human deaths from rabies are estimated at up to 50,000 per year, mostly in developing nations. In the United States, canine and feline rabies cases typically number under 1000 per year, with feline cases currently more common due to a higher rate of vaccination among dogs.
Geographic distribution
There are only a few known rabies-free areas in the world, mostly small island nations and peninsulas. Australia, New Zealand, Japan, England, Ireland, Iceland, Scandinavia, and Antarctica are notable areas with no naturally occurring rabies.
Clinical signs (primary most to least frequent, scientific term, synonyms)
Abnormal behavior, aggression, disorientation, seizures, ascending paralysis, vocalization changes (caused by paralysis of the larynx).
Clinical signs (secondary most to least frequent, scientific term, synonyms)
Fever, hypersalivation, death in 7-10 days from the onset of clinical signs.
Cause (scientific, common term)
Rabies virus (Family Rhadoviridae, Genus Lyssavirus).
Organ system affected (most to least affected)
Central nervous system, peripheral nervous system, salivary glands, musculoskeletal tissue (at the site of virus entry).
Diagnostic tests
Direct fluorescent antibody test on brain tissue after death.
Differential Diagnosis
Insecticide poisoning, head trauma, Viral encephalitis, Choking, Laryngeal paralysis, Brain tumor, Pseudorabies.
Overview
Rabies is a highly fatal viral disease that can affect any warm-blooded animal, including humans. More than 27,000 cases of animal rabies are reported yearly worldwide, with a much larger number of cases going unnoticed in wildlife. The classic rabbies is the well known furious form of the disease in which the animal attacks and bites indiscriminately. However, rabid animals can also suffer from a paralytic, or "dumb" form, which is less easily recognized. The source of infection for dogs and cats is nearly always from the bite of an infected wild animal, but can also result when a rabid animal is eaten. The primary animal vector varies by geographic region, with raccoons, skunks, coyotes and bats being the most important vectors in the United States. In other parts of the world the domestic dog is a far more important reservoir of rabies due to lack of vaccination and high numbers of feral animals. There is no sustainable cat-to-cat transmission in nature.
Once infection has occurred the virus replicates in tissue around the wound and enters peripheral and motor nerves. The virus is transported passively by the body along nerve axons to the central nervous system, and then outward from the brain to the salivary glands, where the virus is shed in large quantities. The length of time it takes the virus to enter the nervous system is variable, from a few days to several months depending on the amount of virus injected, the length of the nerve fibers, and other host factors. Central nervous system involvement in cats and dogs is typically seen between three and eight weeks, and death follows in less than ten days thereafter. Dogs and cats do not shed the virus in saliva and are therefore no able to transmit the virus for longer than three days before showing clinical signs. This is why a ten-day quarantine period after a dog or cat bites a person is usually all that is needed to rule out rabies, despite the potentially long incubation period of the disease. An unvaccinated dog or cat that is bitten by a suspected rabid animal is quarantined for up to six months depending on local or state regulations. Typically dogs and cats are vaccinated after 12 weeks of age, again at one year and then every there years depending on the approved vaccine label. Dogs and cats entering rabies-free countries typically require six month quarantine.
Treatment
Home Care
Any dog or cat known or suspected to have contact with a rabid animal or any unvaccinated animal showing neurological signs must be considered a rabies suspect and requires immediate veterinary examination.
Professional Care
There is no treatment for a rabies infected dog or cat. Animals suspected of having rabies must be euthanized immediately and tested due the obvious public health risk they pose.
Action
There is no treatment for rabies in domestic animals, nor should any be attempted. Efforts must focus on accurate diagnosis, identification of contacts, and post-exposure prophylaxis for humans who have come in contact with a suspect rabid animal.
The primary role of the veterinarian and pet owner in rabies control is insuring that all dogs and cats are properly vaccinated. Vaccination which occur on a regular schedule starting at 3 months of age, is protective.
Outcome
Rabies is considered uniformly fatal once neurological sign develop. Rabies cases are reportable.
Recommended Treatment
Rabies viral infection is fatal. See your veterinarian immediately if your pet may have become exposed to a rabid animal.
References/Additional Readings
Ettinger, Stephen J. Textbook of Veterinary Internal Medicine. 4th edition. Philadelphia: W.B. Saunders Company, 1995; 398-400, 434-435.
Fenner, Frank, J. Veterinary Virology. 2nd edition. San Diego. 1993: 493-500.
Greene, Craig E. Infectious Diseases of the Dog and Cat. 3rd edition. St.Louis: Saunders, 2006 167-183.
Nelson, Richard W. Small Animal Internal Medicine. 2nd edition. St Louis: Mosby,1998: 1014-1015.
Author
Colin Dwyer, DVM
Editor
Steven Hansen, DVM, MS, MBA, DABVT, DABT
Please note that PetVet should only be used as a guide and in no way should be substituted for licensed veterinary care.
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