Danielle Flores & Bailey Brown Rabies

What is Rabies? Rabies is a preventable viral disease of warm blooded mammals most often transmitted through the bite of a rabid animal.

Etiology Rabies is caused by lyssaviruses in the Rhabdovirus family The Rhabdoviruses are uniquely bullet-shaped. They contain a negative stranded RNA genome and are very stable to drying. Lyssaviruses are a group of viruses that includes rabies and bat lyssavirus Lyssaviruses are usually confined to 1 major species in a given area, although spillover to other species is common.

Rhabdovirus

Rabies History The disease was first documented by the ancient Babylonians. Girolama Fracastoro discovered the rabies virus. Louis Pasteur discovered the rabies vaccine in 1895, when he was 63 years old, relying on Fracastoro's written notes. Rabies was so feared in early history that many patients who suffered from the illness were put to death, either intentionally or accidentally It was common practice to shoot, poison, suffocate or use some other form to kill any animal or human with the rabies virus.

Signalment Breed: Rabies most commonly affects carnivores and bats, but can affect all mammals. Age: Young animals may be more susceptible to rabies than older animals. Gender: It is unknown whether the males or females are more susceptible to rabies.

Transmission Rabies is zoonotic (primarily through bats) Rabies can infect all mammals through transmission in the saliva(dogs are primary vectors) Most exposure results from animal bites When an animal is bit, the virus ascends through the peripheral nerves to the brain. Once it enters the brain, the virus replicates. It then moves to the salivary glands. After the virus enters the salivary glands, it may be transmitted to other animals or humans.

Clinical Phases The clinical course may be divided into 3 phases Prodromal Lasts 1-3 days Loss of appetite Lethargy Intermittent fever irritability Excitative “mad-dog” phase Lasts less than a week Sometimes skipped Lack of coordination, twitching, and/or seizures Aggressive behavior Restlessness and roaming lack of recognition for familiar people and places Lack of fear toward natural predators paralytic/endstage Foaming at the mouth This symptom is caused by the growing paralysis of the throat and jaw muscle Slack jawed appearance Full body paralysis, which results in death It should be noted that the virus can remain active inside a dead animal for forty-eight hours

Clinical Signs Most animals will exhibit signs of disturbance in the CNS, but signs vary with species. Common signs include: progressive paralysis sudden anorexia apprehension or nervousness Irritability Hyperexcitability Ataxia altered phonation changes in temperament

Tests Humans: Fluorescent antibody test on punch biopsy of skin from the nuchal region and corneal impressions In vitro virus isolation from saliva Virus neutralization assay on serum, for evidence of rabies antibody Virus neutralization assay on cerebrospinal fluid, for evidence of rabies antibody rt-pcr (Real Time-Polymerase Chain Reaction) for viral RNA and genomic nucleotide sequence analysis on saliva Animals: Testing in animals is most frequently done using the direct fluorescent antibody (DFA) test. requires brain tissue from animals suspected of being rabid. The test can only be performed post-mortem

Treatment No cure. if a person is bitten by a rabid animal and has not yet experienced symptoms, there is an extremely effective post-exposure treatment, which includes an injection of rabies immune globulin and several containing rabies vaccine given over a 28-day period. Rabies vaccination (can be given before or after infection) using a human diploid cell vaccine (HDC) or Purified chick embryo cell vaccine (PCEC). Killed rabies vaccine is given at 12 weeks or older in dogs and cats.

Treatment Always wash and care for a wound, if bitten, with soap and water as soon as possible. If your pet bites a person, it must be quarantined for 10 days at your expense.

Prognosis Rabies is considered a fatal disease, with death occurring three days to one week from the first sign of symptoms. There are few, if any, reports of recovery from rabies.

Pathologic Lesions Histopathologic evidence of rabies inflammation in brain tissue and meninges includes the following: Mononuclear infiltration Perivascular cuffing of lymphocytes or polymorphonuclear cells Lymphocytic foci Babes nodules consisting of glial cells Negri bodies

Perivascular cuffing or inflammation around a blood vessel. Perivascular inflammatory cell infiltrates in hematoxylin & eosin stained brain tissue. (100x Magnification Babes Nodules

Negri body in infected neuron Enlargement of a Negri body in Sellers stained brain tissue. Note the basophilic (dark blue granules in the inclusion).

Prevention Avoid Wild Animals (&BATS!) Many bites and scratches that necessitate post exposure therapy occur when people try to feed or handle a wild animal. Vaccinate Domestic Animals Approved rabies vaccines are currently available for dogs, cats, ferrets, horses, cattle, and sheep. Pre-exposure Vaccination of Humans Pre-exposure vaccination should be offered to all persons whose activities place them at increased risk for being exposed to the rabies virus or to potentially rabid animals. A. Prevent contact with saliva of infected animals, B. Wash bite wounds and apply providone-iodine solution; C. Vaccinate dogs and cats

Client Education Vaccinate pets Never handle wild animals that appear tame Don’t leave food outside The quarantine is to protect humans, not your pet. We don’t want rabies!

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