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Virology > RVFV & EHDV > Flashcards

RVFV & EHDV Flashcards

1
Q

What type of virus is RVFV? What Genus does it belong to?

A
  • Bunyaviruses
  • Phlebovirus
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2
Q

What are the characteristics of RVFV?

A
  • Enveloped
  • Single-stranded RNA (Group V)
  • segmented genome:
    • L (large) M (medium) S (small)
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3
Q

How is RVFV spread? How can the virus be inactivated?

A
  • Arthropod-borne (mosquitos)
  • Zoonotic
  • Inactivated by lipid solvents, detergents, and low pH
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3
Q

How is RVFV spread? How can the virus be inactivated?

A
  • Arthropod-borne (mosquitos)
  • Zoonotic
  • Inactivated by lipid solvents, detergents, and low pH
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4
Q

What is the genomic structure of RVFV?

A
  • Segmented - 11.9kb
  • Large: Viral polymerase
  • Medium: Glycoproteins (Gn, Gc), NSm
  • Small: Nucleoprotein (N), NSs
    • Ambisense RNA segment
  • Relatively low genetic diversity for RNA virus
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5
Q

What is the geographic spread of RFVF?

A
  • Mosquito-borne zoonotic disease of domestic and wild ruminants:
    • 1st reported in Kenya in early 1900s
    • Endemic in tropical and subtropical regions of Africa, Madagascar, Arabian Peninsula
      *
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6
Q

What are the common results of epidemics/epizootics of RVFV?

A
  • Acute febrile disease
  • Abortion in livestock
    • abortion storm
  • death of young animals
  • Major affected species:
    • Sheep
    • cattle
    • goats
  • influenza-like illness in humans
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7
Q

Why is RVFV important?

A
  • Emerging transboundary viral disease
  • Reportable FAD
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8
Q

When do outbreaks of RVFV occur?

A
  • associated with abnormally heavy rainfalls or localized flooding
    • Epidemics occur at 5-15y intervals in Africa - peaks in late rainy season, late summer
    • Seasonal outbreaks in colder regions
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9
Q

Why are outbreaks of RVFV associated with heavy rainfall?

A
  • Transovarial transmission in mosquitoes - dormant virus in eggs in soil
  • Heavy rainfall ⇢ eggs hatch, infected mosquitoes emerge
  • Virus can also subclinically cycle between mosquitoes and mammalian hosts between outbreaks
  • Virus is spread by movement of viremic animals and wind-borne mosquitoes
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10
Q

What are the insect vectors of RVFV

A
  • Mosquitoes:
    • Aedes
    • Anopheles
    • Culex
    • Other potential species including US mosquitoes
  • Biting flies - mechanical vector
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11
Q

Can infected animals/humans infect mosquitos with RVFV?

A
  • Infected livestock - sheep, cattle, goats
    • High levels of viremia
      • Sufficient to infect feeding mosquitoes
      • Establishes disease in environment
      • Leads to large epizootic/epidemics
  • Humans can have viremia levels high enough to infect mosquitos
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12
Q

What animals are the most susceptible to RVFV?

A
  • Mortality 100%
    • young animals (lambs, calves, kids, puppies, kittens, rodents)
  • Severe illness abortion mortality
    • Sheep, cattle, goats, humans
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13
Q

What animals are resistant to RVFV?

A

Horses and pigs

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14
Q

What is the mortality rate of RVFV in lambs/kids? Clinical signs?

A
  • Very high mortality (90-100%)
  • Incubation period 12-36 hours
    • high fever (up to 108F)
    • Listlessness
    • Reluctance to move
    • reduced appetite
    • abdominal pain
    • tachypnea
  • Death within 12 hours to 3 days
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15
Q

What is the mortality rate of RVFV in sheep/goats? Clinical signs?

A
  • Lower mortality (20-30%)
  • Incubation period: 24-72h
    • Fever
    • lethargy
    • diarrhea
    • icterus
    • hematemesis
    • hematochezia
    • mucopurulent nasal dishcarge
  • Can be subclinical
16
Q

What is the mortality rate of RVFV in calves? Clinical signs?

A
  • Less susceptible than lambs (10-70% mortality)
  • Clinical signs similar to lambs/kids:
    • fever
    • depression
    • acute death
  • Death within 2-8d after onset
17
Q

What is the mortality rate of RVFV in cattle? Clinical signs?

A
  • Lower mortality (5-10%)
  • infections are often subclinical
    • Fever
    • weakness
    • reduced appetite
    • lacrimation
    • salivation
    • nasal discharge
    • dysgalactia
    • diarrhea
    • hematochezia
    • icterus
18
Q

What are the clinical signs of RVFV in pregnant livestock?

A
  • Abortion - may be only sign
  • Abortion storm in affected herds
    • Ewes/does: high rate (5-100%) seen, occurs at any stage of gestation
    • Cattle: usually < 10%, can be up to 85% during outbreaks
  • Aborted fetuses are usually autolyzed
19
Q

Is there a vaccine for RVFV?

A
  • Modified-live Smithburn vaccine
  • Not available in US
  • Side effects:
    • early embryonic death
    • congenital CNS abnormalities
    • arthrogryposis
    • Abortion / stillbirth
20
Q

Who should perform the necropsy on animals with suspected RVFV?

A

trained personnel with appropriate PPE

21
Q

What gross lesions are expected in an animal with RVFV?

A
  • Hepatitis:
    • Enlarged, soft, yellow, friable liver
    • Irregular congested patches or petechial hemorrhages
    • numerus grayish white necrotic foci
  • Hemorrhage and edema of gallbladder wall and mucosa of abomasum
  • Dark born intestinal contents
  • Splenomegaly + lymphadenopathy with edema and petechiae
22
Q

What microscopic lesions are expected in an animal with RVFV?

A

severe and extensive hepatic necrosis

23
Q

When should RVFV be suspected?

A

When abnormally heavy rains and flooding are followed by widespread occurrence of abortions and mortality among newborn ruminants characterized by necrotic hepatitis, concurrent with influenza-like disease in people handling animals

24
Q

How is RVFV diagnosed?

A
  • Reportable FAD
  • PCR/VI
    • tissue of aborted fetuses, liver, spleen
    • blood of infected animals
  • Viral antigen detection
    • ELISA, IHC, antigen staining of organ impression smears
  • Serological tests
    • Acute and convalescent samples
    • IgM ELISA - detects recent infection
25
Q

How should RVFV be managed?

A
  • Contact authorities:
    • PPE - gloves, coveralls, boots, eyewear, respirator
    • Avoid contact with infected tissues/blood
    • Restrict animal movement, quarantine
    • Do NOT slaughter sick animals - bury or burn
  • Vaccination - NOT in US
  • Vector control:
    • insect repellents, environmental management (standing water breeds mosquitoes)
26
Q

How do humans become infected with RVFV?

A
  • Readily infects people via direct contact
    • Slaughter or necropsy of infected animals
    • Contact with infected tissues, body fluids, aborted fetuses
  • High risk: veterinarians, farm laborers, abattoir workers, butchers
  • NO person-to-person transmission reported
27
Q

What are the human clinical signs of RVFV?

A
  • Usually subclinical
  • Incubation period 2-6 days
    • flu-like illness - fever, malaise, myalgia, headache, nausea, vomiting, arthralgia
    • Self-limiting - recovery in 4-7 days
  • Sever Disease 1-2% of cases
    • Ocular disease (retinopathy), encephalitis, or severe hepatic lesions with hemorrhage
    • Death in 10-20% of severe cases
  • Overall mortality rate: ~1%
28
Q

What family is Schmallenber virus (SBV) part of? Genus?

A
  • Bunyaviruses
  • Orthobunyavirus
29
Q

What are the characteristics of SBV?

A
  • Enveloped
  • ssRNA viruses (Group V)
  • Segmented genome
  • Arthropod-borne (Culicoides sp)
  • Domestic and wild ruminants only - not zoonotic
  • Susceptible to common disinfectants
30
Q

What is the history of SBV?

A
  • Identified in 2011 - European cattle, sheep, goats, bison
    • Affected dairy cow herds:
      • fever, reduced appetite, reduced milk production, weight loss
      • High herd morbidity (20-70%), recovery after a few days
    • Sheep, goats, cattle:
      • abortions and stillbirths with congenital malformations
      • up to 20-50% aborted/deformed lambs in affected sheep flocks
31
Q

How is SBV transmitted?

A
  • Biting flies (Culicoides sp)
  • Vertical transmission by in utero infection
  • Direct transmission between animals NOT reported - unlikely
32
Q

What are the clinical signs of SBC in adult sheep/goats?

A
  • Increased abortions and congenital malformations in offspring
  • Otherwise generally subclinical
33
Q

What are the clinical signs of SBV in adult cattle?

A
  • Can be subclinical
  • Transient fever, reduced appetite, malaise, reduced milk production, diarrhea, abortion - recovery within a few days
  • Lower incidence of congenital malformations than sheep
34
Q

What Congenital malformations can SBV cause in neonates and fetuses?

A
  • Arthrogryposis/hydranencephaly syndrome (AHS)
  • Specific signs reflect stage of gestation when infected
  • Stillbirth, premature birth, mummified fetuses
  • Arthrogryposis, hydranencephaly, ataxia, paralysis, muscle atrophy, joint malformations, torticollis, kyphosis, scoliosis, behavioral abnormalities, blindness
35
Q

Why is SBV important?

A
  • FAD - Reportable
  • Chance of introduction to US
36
Q

How is SBV diagnosed?

A
  • PCR, VI, SN Ab test, ELISA, IFA
    • fetus/neonate: brain, spleen, blood, placenta, amniotic fluid, meconium
    • Dam/Adult: blood
37
Q

How is SBV controlled?

A
  • No specific treatment
  • Vector control - house pregnant animals indoors at night during critical periods to reduce exposure
    • breed outside the vector season
  • Inactivated vaccines - available in some countriessss

Virology (37 decks)

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