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Describe a broad overview of rabies. (4)
- zoonotic viral encephalomyleitis of mammals
- caused by Lyssavirua (fam Rhabdoviridae)
- almost always fatal once clinical signs occur
- globally, dogs are the source of the vast majority of human rabies deaths
What are rabies reservoirs, and where is each the principal reservoir?
- Globally- Dogs
- Asia, Africa- Dogs
- South America- vampire bats
- Developed countries- terrestrial carnivores (raccoon, skunk, fox, coyote), BATS (most human cases in U.S. come from bats)
What is the major methods of trying to keep the rabies virus confined to the east coast?
oral rabies vaccine
How is rabies transmitted?
through saliva or brain/ nervous system tissue when introduced to a bite wound, open cut, or onto mucous membranes
Classify an exposure.
- Bite- any penetration of skin by teeth
- Non-bite- contamination of open wounds, MMs
- Bat bites are hard to find/ identify- treat any person who has come into contact with a bat and unsure if bitten or not
Describe rabies pathogenesis.
- virus introduced through bite wound, open skin wound, or MM
- travels along nerves from site of bite to brain
- virus multiplies in brain, leading to inflammation
- virus moves from brain to salivary glands and saliva, where virus is shed
How long is rabies incubation?
as short as 2 weeks, as long as 1 year
Can an animal transmit rabies during it's incubation period?
no, and behavior remains normal
How do we decide how to handle an exposure?
- compendium of animal rabies prevention and control
- READ THIS DOCUMENT for exam
What is reportable?
whenever a person is bitten by a dog or other mammal, a report must be made of this bite within 24 hours to the health commissioner of the district in which the bite occurred
What happens when a bite is reported?
- the animal must be quarantined under an order issued by the health commissioner- for no less than 10 days from which the person was bit (why?--> if they are shedding virus at the time of the bite, by 10 days later they should be showing signs of disease or dead)
- animal cannot be released from quarantine until it has been properly vaccinated against rabies by a DVM
- if animal dies, the head should be submitted
If a domestic animal has potentially been bitten by a wild animal,...
- if the wild animal is not available for rabies testing, the domestic animal should be regarded as exposed and next steps depend on vaccination status
- veterinarian should report to health department
- mammal should be confined until determine to be rabies free
How is rabies diagnosed?
- Post-mortem testing- Direct fluorescent antibody on brain tissue (brain stem and cerebellum)
- Human Dx- saliva, serum, CSF, hair follicle tested; ante-mortem Dx requires many tests
Rabies treatment and prevention in humans.
- no effective treatment once clinical signs appear
- rabie post-exposure prophylaxis (PEP) given before onset of symptoms is nearly 100% effective (wound cleansing, rabies Ig, rabies vaccine)- no time limit to give PEP
Describe the use of rabies post-exposure prophylaxis in humans.
- previously unvaccinated people- 4 doses of vaccine IM, rabies Ig with first vaccine
- previously vaccinated people- 2 doses of vaccine and no rabies Ig
What is the only lab in Ohio that can perform DFA rabies test?
Ohio Department of Health State Laboratory
Describe ante mortem rabies testing. (5)
- no ante mortem test can reliably diagnose all positive cases
- false neg can lead to human cases; false pos can lead to animal euthanasia
- Serum antibody test cannot differentiate vaccinate from infection; often not positive until well into clinical phase
- Saliva testing- shedding is inconsistent; can trust your positives more than your negatives (1 virion can cause infection and no be detected)
- DFA Direct Flurorescent Antibody of Brain tissue (gold standard)
What is the gold standard test for rabies testing?
DFA (Direct Fluorescent Antibody) of Brain Tissue- brains stem (full section essential for negative diagnosis), cerebellum
Describe principals of rabies testing sample collection. (4)
- wear PPE to cover exposed skin, protect eyes and MMs (goggles and face mask at a minimum)
- don't use power tools (can aerosolize virus)
- should be previously vaccinated
- DO NOT SUBMIT LIVE ANIMALS, don't damage the head when euth
What samples do you send for rabies testing?
- Small vermin: (bats, rats, chipmunks) send entire body
- Small Animals: (cats, dogs) send entire head
- Large Animals/ Horned animals: send entire brain (special exception for trained vets- send entire brainstem and 3 lobs of cerebellum)
Describe important principals of specimen handling for rabies testing. (5)
- keep specimen refrigerated
- do not fix tissues
- avoid freezing (may delay testing, repeated freezing/ thawing degrades sample)
- double bag, cover sharp edges
- ship in styrofoam cooler with ice packs
How should a rabies testing specimen be labeled?
- "Biologic Substance, Category B", UN 3373 label
- Category B= human or animal material being transported for diagnostic or investigational purposes
- overnight courier, not on Friday or before a holiday
How should the remains of known positives be handled?
- incineration is ideal
- the virus can survive freezing
- virus is destroyed by burning, desiccation, sunlight, and almost all disinfectants
- deep burial acceptable but only in some jurisdictions
Where is rabies post-exposure prophylaxis administered?
in the deltoid muscle
How are rabies titers tested?
- rapid fluorescent focus inhibition test (RFFIT)- virus neutralization test- quantifies ability to neutralize the virus 9not just amount of antibodies)
- complete neutralization at 1:5 dilution of better, otherwise, booster vaccine recommended
How often should veterinarians and their staff get their rabies titers tested?
every 2 years (frequent, but not continuous, risk)
Compare the risk of exposure associated with a rabid cat to a rabid wild animal.
a rabid cat exposes 7 times the number of people as a rabid wild animal
Describe reporting of rabies exposures required by law.
- all dog bites and rabies exposures are required to be reported in all states, regardless of vaccination status of the animal
- Ohio requires reporting of all mammal bites
- in Ohio, report to the local health department whose jurisdiction the bite took place in
What are non-bite rabies exposures? (3)
- scratch with saliva contamination
- inhalation of aerosolized rabies virus
- saliva, brain, or other neural tissue coming in contact with broken skin or MMs
What is the main mode of rabies exposure?
any mammal bite that breaks the skin
Describe the special circumstances of determining rabies exposure via a bat.
- bite or scratch with saliva
- finding the bat in a room with a pet, sleeping person, child, otherwise impaired individual who cannot recall or communicate contact with bat
What types of contact are NOT considered rabies exposure? (4)
- petting or touching a rabid animal
- contact with something a rabid animal touched (unless wet from the mouth)
- contact with urine or blood
- skunk spray
Bites from dogs, cats, and ferrets- quarantine or euthanize?
- neurologic signs--> euthanasia and submit head
- no signs--> 10 day quarantine for healthy animals that have bitten a human (vets do not have authority to order quarantine, local health department)
When does viral shedding of rabies virus occur in the clinical course? How does this translate ot the 10 days quarantine?
- no more than a few days prior to onset of symptoms (1-3 days pre-clinical shedding w/o symptoms)
- 1-3 days pre-clinical shedding, 3-5 days clinical illness prior to death, +2 days for abundance of caution
Report domestic animals to the local health department if they were...
bitten or had potential saliva exposure to a rabies positive animal or suspect positive, a wild carnivore, a bat, any animal displaying signs of rabies
How do you handle potentially exposed domestic animals with different rabies vaccination status?
- Currently vaccinated with proof: booster and 45 day quarantine
- Overdue with proof: booster and 45 day quarantine
- Overdue, no proof: as unvaccinated or paired serology
- Unvaccinated dog, cat, or ferret that is exposed: euthanasia and testing; if doubt as to exposure may isolate 4 months (K,Fe) or 6 months (ferret)
What is legal proof of rabies vaccination?
- certificate signed by a licensed veterinarian
- vaccine approved for that species
What are the recommendations for home quarantine?
- confined in an outdoor double barrier enclosure
- on a leash under control of a responsible adult
- do not take off premises or change ownership
- no new pets in home
- limit human contact, do not touch saliva