Bunyaviridae Flashcards
general
spherical, enveloped
glycoprotein spikes
no matrix protein
3 nucleocapsid segments, helical symmetry
segmented (-)ssRNA
3 RNA segments: L (large), M (medium), S (small)
cytocidal (kills) for vertebrate cells
replication
cytoplasm
budding into gogi vesicles
T/F genetic reassortment occurs
True, between closely related species
What are the arthropod borne viruses
Genus orthobunyavirus: akbane virus
genus phlebovirus: rift valley fever virus
what are the nonarthropod borne viruses
genus hantavirus: hantaan virus
Rift Valley Fever (RVF)
Genus: phlebovirus
sheep, cattle, goats most affected (others can be seen)
throughout africa
RVF in humans
most inf result from percutaneous or aerosol exposrue while slaughtering infected animals or handling infected aborted fetuses
also from bites of infected mosquitoes (aedes mosq.)
no human-human transmission
Transmission of RVF
biological: mosquitoes
primary aedes
secondary culex and anopheles sp
mechanical: biting flies (culicoides, midges)
enzootic cycle
normal rainfall
local enzootic transmission
epizootic-epidemic cycle
abnormlaly heavy rainfall flooding of dambos (dry depressions where eggs survive long time)
massive emergence of transovarially infected aedes spp. mosquitoes
more infected cattle and human epidemic (more infected cattle and sheep lead to even more infected mosquitoes- secondary vectors)
amplification- very high proportion of animals and humans at risk
RVF pathogenesis
replicates rapidly, reaches very high titer in target tissues
replicates in liver, and other major organs causing widespread cell necrosis
encephalitis, hemorrhages in GIT, englarged spleen
hepatic necrosis, renal failure, and shock (sometimes hemorrhagic complications) leads to death
90-100% [pregnant animals have abortions
what is common to see in terminally affected sheep
extensive hepatocellular necrosis
RVF Clinical signs
Sheep: 90-100% mortality in young lambs
if survive hepatic inf. can see encephalomyelitis
90-100% ewes abort
Cattle: less severe, 90-100% cows abort
Diagnosis RVF
should be suspected when abnormally heavy rains and flooding are flowed by widespread occurrence or abortions and mortality among new born animals characterized by hepatic necrosis, concurrent with flu-like disease in people handling animals or products
RVF control
based primarily on livestock vaccination and vector control
attenuated virus RVF produced in mouse brain and in embryonated eggs are effective and inexpensive for sheep, but cause abortions
inactivated virus vaccines in cell cultures dont cause abortions but are expensive
