Rabies: Something to Foam at the Mouth About
Well, it is almost time to go back to school, and I had to take my son to get his tetanus booster today. It is also “National Immunization Awareness Month.” So, I decided to talk about vaccines, and I will start with rabies.
Rabies virus is caused by a bullet-shaped rhabdovirus, which is an RNA virus. All warm-blooded animals are susceptible, but carnivores and bats are affected most frequently. Rabies is maintained in wildlife, and the largest reservoir in Oklahoma is skunks. Bats are our second largest reservoir, however. As of July 31, 2017, there have been 35 confirmed cases of rabies in Oklahoma for the year.
Transmission is through virus-laden saliva. After a bite, the virus travels along peripheral nerves to the brain and spinal cord. It replicates in the central nervous system, and then, it migrates back along the peripheral nerves to the salivary glands.
The incubation period of rabies is long, ranging from 3 weeks to 6 months, but most dogs develop signs within 21-80 days. Because of the long incubation period of the virus, humans can be treated with post-exposure prophylaxis (PEP) because rabies is fatal once clinical signs develop.
Clinical signs are neurological, and they can be seen in three phases. The first phase is the prodromal phase. Animals exhibit behavioral changes, dilated pupils, and fever. This phase usually lasts 1-3 days. Next, animals enter the excitement or furious phase. They will experience exaggerated reactions to sight and sounds. Their pupils become smaller than normal. They will often exhibit aggression. Wild animals may lose their fear of humans, and nocturnal animals may wander around in the daytime. Animals may salivate profusely, and they may experience ataxia or seizures. This phase lasts 1-7 days. The last phase is the dumb phase or paralytic phase. Animals can exhibit pharyngeal paralysis and be unable to swallow. They can become paralyzed, lose the ability to close their jaw, go into a coma, and die. This phase lasts 2-4 days.
Interestingly, our feline friends exhibit the furious form of rabies approximately 90% of the time. Cats often die within 3-4 days of developing clinical signs whereas other species often live 1-10 days.
As you can see, clinical signs are rapidly progressive once animals are symptomatic. So, if an animal bites, a 10-day quarantine is a sufficient amount of time to determine if they are rabid. However, there is no way to confirm rabies in a live patient, and the way to confirm a diagnosis is through examining brain tissue. If rabies is suspected, the entire head should be removed and taken to the state health department. You can visit the Oklahoma State Health Department for more information about submission and handling of the animal at www.ok.gov/health.
Obviously, rabies is a horrible disease, and it is seen worldwide. The incidence is lower in the USA primarily because of rabies vaccination in pets and also because of use of an oral vaccine in wildlife. Puppies and kittens should be vaccinated at 8-12 weeks of age. They should be given a booster dose one year later, and they should then be vaccinated every 1-3 years thereafter. The frequency of rabies vaccine administration depends on the product label and also on both state and local ordinances. In addition to regular rabies vaccines, you can also keep your pet indoors to decrease risk of exposure to rabid animals. If you see a stray animal in your neighborhood, contact animal control to remove them.
You can also protect yourself. Be careful around animals showing aggression, and learn bite prevention techniques. Don’t pick up dead animals, especially bats and skunks. Wash the bite wound immediately, and continue to wash for 10 minutes. Contact your health care provider as soon as possible to determine if you need antibiotics or a tetanus booster. If the animal tests positive (or is unavailable for testing), you will need post-exposure prophylaxis.
If you or your pet gets bitten by a wild animal, contact animal control to help catch the animal. The animal should then be euthanized and tested for rabies. If you don’t have the wild animal, you can talk to your veterinarian about boostering your pet’s rabies vaccine.
As mentioned previously, a 10-day quarantine is sufficient to determine if a pet has rabies. In Oklahoma, we are required to quarantine animals for that 10-day period with a licensed veterinarian if they are not currently vaccinated by a licensed veterinarian (the state department will not recognize vaccines administered by the owner). If the pet that bites someone has a current rabies vaccine, they may be quarantined for 10 days at home.
To wrap this up, rabies is truly a horrible, fatal disease that is preventable with vaccination. Please booster your pet’s vaccine regularly for your safety as well as theirs.
