Flashcards in One Health approach to zoonoses Deck (33)
How often is rabies transmitted to humans?
99.9% dog bites
(>99% dogs, <1% other carnivores, bats)
On which continent are there the most deaths due to Rabies?
Asia, closely followed by Africa
What are the 2 rabies reservoirs?
Urban - domestic dogs - Africa, Asia, Latin America,
Sylvatic - wild animals (skunk, raccoons, bats) - Europe, N/S America, Asia
What does human outcome depend on? 3
Clinical onset may not be immediate
How common is rabies in children?
over 40% cases are in children (unknown why, perhaps less educated)
Outline rabies pathogenesis
Bite: slow multiplication of virus in muscle cells (incubation)
Rapid transport of virus genomes in nerve axons
Rapid virus spread within CNS
Massive virus replication in nerve cells
Transport in nerve axons to salivary glands and other peripheral organs
VIRUS EXCRETION AND EXPRESSION OF CLINICAL SIGNS
Clinical signs - dog rabies
FURIOUS FORM (30%): agitated, aggressive, difficulty swallowing, salivation, seizures - death, incoordination, paralysis, coma and death
DUMB FORM (70%): dropped jaw, bone in throat, incoordination, paralysis and death
Outline rabies in livestock
Incubation = 10-40 days
Morbidity = 3 days
Death can occur per-acutely with no clinical signs
Manifests as furious form in 80% animals
CS: changes to behaviour, aggression, head butting, drooling, animals can be restless, depressed, head tremors, incoordination, paralysis
How many rabies vaccination boosters should you hav?
Boost 1/2 years after primary vaccination. Subsequent boosters should be given at 3-5 year intervals.
What are the 2 types of RIG that can be used in humans
Human RIG (HRIG)
Equien RIG (ERIG)
As much of the RIG dose as anatomically feasible should be infiltrated in the area around the wound and the remaining volume is administered IM. RIG provides transiet protection during the period before vaccine-induced immunity is conferred (usually 1 week)
How can exposure to rabies be categorised?
CATEGORY 1 = touching or feeding animals licks on intact skin - NO Tx
CATEGORY 2 = nibbling of uncovered skin, minor scratches or abrasions without bleeding - Local treatment of wound and immediate vaccination
CATEGORY 3 - single or multiple transdermal bites or scratches, licks on broken skin, contamination of MM with saliva from licks, exposures to bats - local treatment of wound, immediate vaccination and administration of RIG.
Current limitations of RIG
difficulty in finding immune donors
batch-to-batch variation of polyclonal sera
risks related to use of blood products
What are possible alternatives to RIG?
serveral murine Abs
How are domestic animals vaccinated against rabies?
Inactivated virus + adjuvant (aluminium phosphate)
IM or SC with peak neutralising Ab titre reached by 4-6 weeks in dogs.
Single dose --> protective immunity:
Nobivac (Intervet): dog, cat, horse, cattle
Rabisin (Merial): dog, cat
Booster required: 1-3 years
Outline oral vaccination of dogs against rabies
Considered as a supplement to PN vaccination. Could be applied on a larger scale.
How can wildlife be vaccinated against rabies?
Oral vaccination - live attenuated vaccine within a bait (fishmeal).
SADB19, SAD p5/88 (attenuation mechanism unknown)
SAG2 (2 point mutations in the glycoprotein gene)
VRG (vaccinia recombinant expressing glycoprotein)
What are the 'rules of steck'? 3
Compartmentalisation of the contaminated area using natural and artificial barriers.
Repeat vaccination until rabies elimination is confirmed and to protect rabies-free areas.
Establish concerted plans of vaccination with neighboring countries - fly over border and drop baits on both sides.
Oral Rabies Vaccination
How did ORV affect fox rabies in W. Europe?
Within 25 years of introduction of ORV, fox rabies was eliminated in W. Europe.
Outline lyssavirus evolution
NEW WORLD: classical rabies virus, NO other lyssaviruses
OLD WORLD: lyssaviruses in bats, NO classical rabies virus
OVERALL: epidemiological confusion
Clinical presentation - EBLV-1 - bat rabies
Fierce reaction to high frequencies
Prolonged very loud screaming
Uncontrolled wing beats
Strong biting and aggressive behaviour
When was rabies eradicated in the UK?
1902 with leash laws, muzzles and destruction of strays. Never became established in terrestial wildlife.
See occasional cases of imported human disease
How can rabies be diagnosed?
FAT and real time PCR - within 3 hours
Virus isolation - 2 days --> mice innoculation --> developed rabies in 9 days.
Immunohisopathology identification of rabies virus Ag in the medulla.
When was PETS introduced?
Outline PETS from January 2012
Dogs, cats and ferrets
–No longer requirement for blood testing if vaccination certificate in order
–No requirement for quarantine where importation from unlisted ‘third countries’
–Instead, vaccination, blood tested 1 month later and a further 3 month wait in country of origin prior to entry
–Risk of illegal importation remains
–Loss of requirement for tick treatment-tapeworm treatment debated
How can wildlife rabies be controlled?
Provision of emergency vaccine stockpile
Ring vaccination (ORV)
Is rabies a candidate for true eradication?
No due to the distribution and abundance of bats as reservoir hosts.