Rhabdoviridae Flashcards
what is unique about rhabdoviridae morphology? very characteristic
enveloped and BULLET SHAPED
what are the 5 important proteins encoded by rhabdoviridae
1 - L. Large protein, RNA dependent RNApol
2- G. Glycoprotein that forms the envelope spikes
3- N. Nucleoprotein, associates with RNA to form nucleocapsid
4- P. Phosphoprotein, mediates binding of L protein to the nucleocapsid
5- M. Matrix protein, associates with the viral nucleocapsid and lipid envelope.
t/f - rhabdoviridae have single stranded, negative sense RNA
true
rhabdoviridae replicate in the ______ and maturation is done by budding through the _______
cytoplasm
plasma membrane
t/f - rhabdoviruses can cause rapid cytopathology OR be non-cytopathogenic.
true.
i.e. vesicular stomatitis virus, cytopathic.
street rabies virus strains, non-cytopathogenic.
what are the three major diseases caused by rhabdoviridae, and which genera are they?
- bovine ephemeral fever virus (Ephemerovirus)
- rabies virus (Lyssavirus)
- vesicular stomatitis virus (Vesiculovirus)
what is the particular etiology of rabies?
Genotype-1 Lyssavirus
what are some low risk countries for rabies?
japan, singapore, NZ, antarctica, and lots of caribbean islands
what are the 8 species that you need to know for contracting rabies?
High risk: cats and cattle
Moderate risk: dogs, sheep, goats, horses, primates, humans
main mode of transmission of rabies?
bite or scratch of animal with virus in saliva
what are some minor modes of transmission for rabies?
Less often, an animal or person is infected by contact with infectious saliva or neurological tissues, through mucous membranes or breaks in the skin.
Aerosol transmission has been documented in special circumstances, such as in laboratories and bat caves
A few human cases have been reported after transplantation of organs, particularly corneas but also pancreas, kidneys and liver
Though most animals are susceptible to rabies infection, many are ‘dead end’ hosts who will be unlikely to transmit the infection. Such ‘dead end’ hosts include ______________________
humans and most herbivores: cattle, sheep, goats and horses
why are bats significant in rabies?
Important Wildlife Reservoirs: Bats
Many species of bats harbor different variants of rabies virus.
In many bats, the infection is asymptomatic
Rabid bats may develop paresis or paralysis, or may be disoriented, or may sometimes show aggression
there are three important kinds of bats for lyssavirus. what are they, and where are they?
1) Insectivorous bats - north america
2) vampire bats - mexico, central, south america
3) fruit bats - australia
t/f - skunks are a reservoir for rabies
true:
Skunks have been most important in the perpetuation of wildlife rabies in the central regions of USA.
They account for most cases of cattle rabies
t/f raccoons and red foxes are reservoirs for rabies
true
raccoon is most frequently reported rabid wildlife species
describe pathogenesis of rabies virus, with regards to entry of the virus
- After Intramuscular inoculation, virus may
enter peripheral nerves directly, or replicate locally in non-nervous tissue until they reach sufficient concentration to reach motor or sensory nerve endings in the muscle or skin. - the G or glycoprotein of the virus bind to axon terminals of peripheral nerve fibers through lipoprotein receptors, including those for acetylcholine, facilitating its entry into nerve endings.
- The greater the degree of innervation at the site of bite, the shorter the incubation period.
- Location of Injury: Bites to face have the greatest risk
T/F - although uncommon, after intranasal exposure, the rabies virus may enter the trigeminal nerves and ganglia in its course to the CNS
true
describe pathogenesis of rabiesvirus with regards to the spread into the CNS, and excretion.
The second phase of infection begins when the virus progresses centripetally to the CNS via the axoplasm of the peripheral and central nerves.
The virus reaches the limbic system where it replicates extensively, leading to the “furious” form of rabies.
Spread within the CNS continues, with replication in the neuro-cortex, resulting in the “dumb” or “paralytic” form of rabies
Late in infection, the virus moves centrifugally from the CNS down the peripheral nerves to a variety of organs including the adrenal cortex, pancreas and the salivary glands (via cranial nerves).
Extensive replication of virus in salivary glands results in high concentration of virus in saliva
what are the epidemiological cycles of rabies?
one sylvatic and one urban
urban- dogs are the main reservoir; predominant in africa, asia, central/south america
sylvatic- predominant in europe and north america; also present simultaneously with the urban cycle in some parts of the world.
what are the characteristic macroscopic lesions of animals who’ve died from rabies?
psyche! there are none
The brains of animals with rabies exhibit variable inflammation and often only modest histological evidence of neuronal injury.
how do you detect the immune response in an animal as the rabies virus moves from the bite into the CNS?
PSYCHE
you don’t bruh. usually no CMIresponse or humoral during that time period.
when do antibodies appear in serum/CSF with rabies infections?
after neuro signs appear. serum first, then CSF
explain what is unique about neuronal MHC, and why it is relevant to rabies.
No MHC class I is expressed. very little stimulation of host immune response
further, infection is non-cytopathic in muscles and nerve cells.
how does incubation period vary in rabies?
Depends on dose of inoculated virus, strain of virus, site of bite, degree of innervation.
Closer site of bite to brain, shorter the incubation period
Higher the degree of innervation at site of bite, shorter the incubation period
what are the three phases of the clinical course of rabies?
- prodromal
- acute excitative (furious form)
- paralytic endstage (dumb form)
in rabies, survival is _______
rare
the period of rabies virus shedding and temperament change before clinical signs appear is known as what?
the prodromal phase
key points of “mad dog” syndrome?
rabies - furious form(acute neural excitative phase)
- nervous, irritable, aggressive
- animals lose caution and fear
- alertness, anxiety
- pharyngeal paralysis (can’t swallow water “hydrophobia”)
- excessive salivation, sensitive to light/sound, hyperesthesia
what is key in the dumb form of rabies?
paralytic form
- encephalitis progresses, fury gives way to paralysis
- ataxia, muscle weakness, loss of sensation
- terminally, there are: convulsive seizures, coma, respiratory arrest. death occurs 2-14 days after onset of signs
which animals are most likely to exhibit fury with rabies?
cats, dogs, horses
ruminants and lab species are less likely
what is the main Dx tool for rabies?
Direct FAT; demonstrate rabies antigen in touch impressions of brain tissue. recommended by WHO and OIE
what histological finding is ABSOLUTELY SUPER DUPER IMPORTANT in rabies?
NEGRI BODIES:
inclusion bodies, proteins of the virus
BUT REMEMBER, they do not always appear. pretty rare in wildlife, and only 75% of human case.
when isolating the rabies virus in weanling lab mice, what clin sign do you see
ENCEPHALITIS develops w/in 14 days
controlling rabies in rabies free countries vs endemic countries?
rabies free: QUARANTINE, segregate dogs and cats, at least 6 months
endemic: vaccination of dogs/cats/wildlife(bait vaccines)
Preexposure and postexposure recommendations for dogs and cats?
pre-
vaccinate 3 months, then once again every 1/3 yr
post-
previously unvaccinated: lol yer fucked. euthanize, or quarantine for 6 months and then vaccinate
vaccinated, but not current: case by case
vaccinated, current: revaccinate immediately, and keep under owner’s control for 45 days
What is the etiology of vesicular stomatitis?
Genus Vesiculovirus, family Rhabdoviridae
t/f - vesicular stomatitis serotypes offer cross-protection
FALSE
important serotypes of vesiculovirus in north america?
Indiana
New Jersey - more virulent and widely distributed
hosts of vesicular stomatitis are?
mostly cattle, pigs and horses in N America
occasionally sheep./goats
influenza-like zoonosis for humans
where does vesicular stomatitis occur?
mostly americas and caribbean
how does vesicular stomatitis get transmitted?
mostly through breaks in the mucosae or skin
- contact with contaminated milking machines (teats/udder lesions)
- chewing/ingestion of contaminated fomites (oral lesions)
Arthropods!
black flies, sand flies, leafhoppers, culicoides
virus replicates in arthropods, BUT mechanical transmission is believed to be more significant than biological
describe the pathogenesis of vesicular stomatitis
mucous membranes of oral cavity and skin infected –> formation of fluid-filled vesicles –> ulcerate
not unusual for epithelium of entire tongue or teat to slough
no apparent significant systemic or viremic phase except in perhaps swine and lab animals
first major signs of vesicular stomatitis?
cattle and horses: excess salivation and fever
swine: lameness
what’s common for vesicular stomatitis in horses, swine and humans?
horses: pronounced tongue lesions
swine: snout and coronary band lesions
humans: self-limiting influenza-like disease lasting for 3-5 days
What are some differentials for vesicular stomatitis????
clinically indistinguishable from FMD (swine/cattle), Swine vesicular disease, and vesicular exanthema of swine.
for horses, vesicular lesions are characteristic ONLY of vesicular stomatitis
is vesicular stomatitis reportable?
YEAHHHHHH
what is the etiology of bovine ephemeral fever? what is another name for the condition?
Genus Ephemerovirus, family Rhabdoviridae
aka 3-day Sickness
hosts of bovine ephemeral fever?
cows, water buffalo
where in North America is bovine ephemeral fever endemic?
PSYCHE
never reported in North America you big dummy
‘cept you knew that cause you’re LITERALLY SMART AS FUCK
what are the vectors of bovine ephemeral fever?
Arthropods, but not totally sure which ones.
BELIEVED to include Culicoides, and possibly Culicine/Anopheles mosquitos
though poorly understood, what are the key points of bovine ephemeral fever pathogenesis?
- associated with buffy coat fraction of blood
- early neutrophilia with a left shift (high immature neuts)
- plasma fibrinogen goes up, calcium goes down
most common lesions of bovine ephemeral fever?
polyserositis of the joints, pleural and peritoneal surfaces
bovine ephemeral fever is ultimately what kind of disease? (big picture here)
INFLAMMATORY
bovine ephemeral fever may be associated with an acute ______-dependent _________ hypersensitivity.
neutrophil; immune complex
key clinical features of bovine ephemeral fever?
- biphasic, triphasic, or polyphasic
- excessive salivation, serous nasal discharge, tachycardia, dyspnea, stiffness, lameness
- DRAMATIC recovery usually in ~3 days
- some animals become recumbent and paralyzed for 8hrs to >1 wk
