Bunyaviridae

Question 1

What’s unique about bunyaviridae envelopes?

Answer 1

there’s no matrix protein

Question 2

describe bunyaviridae genomes

Answer 2

SEGMENTED, negative sense, ssRNA

Question 3

bunyaviridae are generally ______ for vertebrate cells

Answer 3

cytocidal

Question 4

what are the four genera of bunyaviridae?

Answer 4

arthropod borne:

• orthobunyavirus; akabane
• phlebovirus; rift valley fever
• nairovirus; Nairobi sheep virus

non-arthropod borne:
-hantavirus; Hantaan

Question 5

etiology of Rift Valley Fever virus?

Answer 5

phlebovirus, family bunvyaviridae

Question 6

hosts of Rift Valley Fever?

Answer 6

sheep cattle and goats

can infect humans as well

Question 7

how does rift valley infect humans?

Answer 7

percutaneous or aerosol exposure while slaughtering or handling infected fetus

Aedes mosquito bites

NO HUMAN TO HUMAN TRANSMISSION

Question 8

rift valley fever occurs throughout _________

Answer 8

most of africa

Question 9

main vectors of rift valley fever?

Answer 9

mosquitos(biological):
Primary - Aedes spp
Secondary - Culex spp, and Anopheles spp

biting flies(mechanical) - culicoides

Question 10

describe the epizootic-endemic cycle of rift valley fever

Answer 10

• flooding of dambos (increased rain)
• massive emergence of transovarially infected Aedes –> feed on livestock –> abortion storms(epizootic) –> culex/anopheles infections –> human infections (epidemic)

details:
 The virus is transmitted transovarially (thorugh egg) among floodwater Aedes
spp. mosquitoes.
 The virus survives for very long periods in mosquito eggs laid at the edges of
usually dry depressions, called “dambos”.
 When the rains come and the dambos flood, the eggs hatch, and infected
mosquitoes emerge and infect nearby wild and domestic animals.
 These Aedesmosquitoes become very numerous after heavy rains, and infect
sheep and cattle.
 Large number of these infected sheep and cattle become viremic, allowing
many more mosquitoes (inducing secondary mosquito vectors) to become
infected.
 This amplification, together with mechanical transmission by biting flies, results
in infection and disease in a very high proportion of animals and humans at
risk

Question 11

describe the pathogenesis of rift valley fever

Answer 11

 Rift Valley fever virus replicates rapidly and reaches very high titer in target tissues.
 Virus replicates in liver and other major organs, resulting in widespread cell
necrosis.
 Extensive hepatocellular necrosis is common in terminally affected sheep.
 Encephalitis, hemorrhages in GI tract and enlarged spleen.
 Hepatic necrosis, renal failure, and shock, sometimes with hemorrhagic
complications, are the primary causes of death.
 About 90-100% of pregnant animals abort

Question 12

clinical signs of rift valley fever?

Answer 12

 Sheep:
 Mortality in young lambs is high (90%–100%)
 Young animals surviving the hepatic infection may show encephalomyelitis.
 90-100% of pregnant ewes abort.

 Cattle:
 Less severe than sheep. However, 90-100% of infected pregnant cows abort

Question 13

rift valley fever Dx?

Answer 13

RVF should be suspected when abnormally heavy rains and flooding are followed by widespread occurrence of abortions and mortality among newborn animals characterized by necrotic hepatitis, concurrent with influenza-like disease in people handling animals or their products

Question 14

rift valley fever control?

Answer 14

 Control is based primarily on livestock vaccination, but vector control (via use of
mosquito larvicides and insecticides) is also used during outbreaks.
 Attenuated-virus Rift Valley fever vaccines produced in mouse brain and in
embryonated eggs are effective and inexpensive for use in sheep, but they cause
abortions in pregnant ewes.
 Inactivated-virus vaccines produced in cell cultures avoid the problem of abortion,
but are expensive

Question 15

Akabane is a ________-transmitted virus that causes ___________________ in ruminants

Answer 15

insect; congenital abnormalities of the CNS

Question 16

what is the etiology/host of akabane?

Answer 16

orthobunyaviridae, of family bunyaviridae

congenital dz of cattle, sheep, goats

Question 17

transmission of akabane?

Answer 17

Akabane virus is transmitted by biting midges (gnats) of genus Culicoides, as well as by mosquitoes (Aedes and Culex spp)

Question 18

pathogenesis of Akabane in a pregnant animal?

Answer 18

 After the bite of an infected mosquito, the virus infects the pregnant ruminant
(cow, goat, or sheep).
 Virus reaches the fetus from the maternal circulation.
 The most severe fetal lesions in cattle result from infection at 3–4 months of
gestation, and earlier in sheep and goats, when the central nervous system is
developing.
 Fetal infection results in both encephalomyelitis and polymyositis.
 Virus infection of CNS causes destruction of the developing brain and subsequent
hydranencephaly.
 Arthrogryposis, the other highly characteristic manifestation of fetal infection
with Akabane virus, is characterized by muscular atrophy and the abnormal
fixation of several limbs

Question 19

4 main conditions to associate with Akabane?

Answer 19

polymyositis, hydranencephaly, arthrogryposis, encephalomyelitis

Question 20

clinical signs of akabane?

Answer 20

No clinical signs in adults and young animals.

 Infection of pregnant cattle or sheep can lead to one of two outcomes:
 death of the fetus and abortion,
 or birth, sometimes premature, of progeny with congenital defects.

 Affected fetuses characteristically have:
 Hydranencephaly
 Arthrogryposis

Question 21

diagnosis of akabane?

Answer 21

 Detection of a specific neutralizing antibody in serum collected from aborted fetuses or from newborn calves, kids, or lambs before ingestion of colostrum.
 Virus is difficult or impossible to isolate after calves, kids, or lambs are born, but can be isolated from placenta or aborted fetus

Question 22

control of akabane?

Answer 22

Akabane disease should be reported immediately to state or federal authorities upon diagnosis or suspicion of the disease.
 An inactivated virus vaccine is available in Japan and Australia

Question 23

tell me about the Schmallenberg

Answer 23

 Etiology: Belongs to genus Orthobunyavirus
 Host:Cattle, Sheep, Goats
 Distribution: European countries
 Transmission:Insect vector transmission, Culicoides spp
 Clinical signs:
 Malformed animals (Arthrogryposis/ Hydranencephaly) and stillbirths
 Adults (cattle): Diarrhea, Abortion, reduced milk production