VSV & BLuetongue Flashcards
1
Q
What doe “Rhabdo-“ mean?
A
rod (bullet-shaped)
2
Q
What genus does Vesicular stomatitis virus belong to?
A
Vesiculovirus
3
Q
What are the physical characteristics of VSV?
A
- Enveloped
- (-)ssRNA
- 11Kb genome
- 5 distinct proteins
- G: neutralizing epitopes
4
Q
What species are affected by VSV?
A
- Horses, Cattle, Swine
- wildlife, very rare in sheep, goats, llamas, alpacas
- Zoonotic potential
5
Q
How many serogroups of VSV are there?
A
- 2 serogroups - distinct NAb
- New Jersey
- Indiana
6
Q
What is the geographical spread of VSV?
A
- Limited to the Americas
- sporadic outbreaks in US
- limited to western states since 1980s
- sporadic outbreaks in US
7
Q
How does VSV affect humans?
A
- Most cases asymptomatic
- Can cause flu-like illness
- Headache, fever, muscle aches, weakness for 3-5 days
- Rare - vesicles and encephalitis
8
Q
When does VSV occur?
A
- Seasonal variation - vector availability
- May to October
9
Q
Why is VSV important?
A
- Reportable disease
- May result in trade restrictions
10
Q
How is VSV transmitted?
A
- Direct: contact with infected animals - mucosa and skin
- Indirect: contaminated shared feed and water stations
- Blood-feeding insects:
- sandflies, black flies, biting midgets
- Biological vectors
- Associated with water sources, typically warmer months
- sandflies, black flies, biting midgets
11
Q
How do insects spread VSV?
A
- Insect pick up VSV from feeding on infected animals
- replicate the virus
- secrete it from their salivary glands when they feed again
12
Q
What are the clinical signs of VSV infection?
A
- Incubation period 2-8d
- Fever - before or same time lesions appear
- Broad tissue tropism
- Typically self-limiting, resolves in 10-14 days
13
Q
How prevalent is VSV? How fatl?
A
- Morbidity rate generally low in herd: 10-20%
- Previous exposure, underlying immunity, route of exposure
- Seroprevalence may be high - approaching 100%
- Mortality rare
14
Q
How are VSV and FMDV similar?
A
-
Identical clinical presentation to FMDV
- Excessive salivation: ptyalism )often 1st sign)
-
Vesicles, ulceration, erosion of various sizes of the oral and nasal mucosa, mucocutaneous junction of lips, sloughing of the epithelial surface of tongue
- Coronary bands, foot lesions, and lameness
- Prepuce, vulva, and teat lesions , possible 2° mastitis
- loss of appetite, reluctance to eat/drink
- Crusting lesions of the muzzle, ventral abdomen, ears, sheath, and udder
15
Q
When were significant outbreaks of VSV?
A
- 2005/2006
- 9 states, 445 premises
- 584+ equines cases
- 202+ bovine cases
- 2009
- 2 states, 5 premises
- 7+ equine cases
- 2012
- 2 states, 36 premises
- 51+ equine cases
- 2015/2016
- 823 VSV-affected premises confirmed or suspected in 8 states
- 2019
- 1144VSV affected premises confirmed or suspected in 8 states
- 2020
- 326 VSV affected premises confirmed or suspected in 8 states
- KS: 196 affected premises
16
Q
How is VSV diagnosed?
A
- REPORT to Authorities/Regulatory Veterinarians
- Samples collected FAD diagnostician
- Zoonotic - PPE should be worn when handling affected animals
- Antibody detection
- VI/PCR or active vesicular lesions
- Vesicular fluid, epithelial tags from lesions, lesion or mucosal swab
- Typically no viremia
17
Q
What are the DDx for VSV?
A
- FMDV
- SVDV
- VESV
- SVA
18
Q
How is VSV managed?
A
- No specific treatment available
- Soft feed for pain associated with oral lesions
- Cleaning wounds with mild antiseptics (prevent 2° infections)
-
Reduce exposure to vector
- Shelter/housing, insecticides, eliminate insect breeding areas
- Pasture away from moving water (streams, rivers)
- Isolate affected animals, quarantine
- Premises containing affected animals are quarantined for at leas 14 days from the onset of lesions in the last affected animal
- Biosecurity, disinfecting equipment/fomites
- Commercial vaccines not available in US
19
Q
Is there a vaccine for VSV?
A
- Commercial vaccines are NOT available in the US
20
Q
What is the triad of Vesicular Diseases?
A
- Vesicles
- Fever
- Lameness
- All vesicular diseases are clinically indistinguishable
- All require testing to confirm diagnosis
21
Q
What Family and Genus are Bluetongue Virus part of?
A
- Reoviridae
- REO - Respiratory, enteric orphan viruses
- Orbivirus - BTV, EHDV
22
Q
What are the characteristics of BTV?
A
- dsRNA 19kb
- Nonenveloped
- Segmented genome - 10
- >26 different serotypes worldwide
- >13 in US
23
Q
What is BTV?
A
- Non-contagious infectious arthropod-borne viral disease of domestic and wild ruminants (known for >100y)
- Geographical restriction due to climate and environmental conditions needed to support Culicoides biting midge vectors
- In US: C. sonorensis and insignis
- detected in southern and western states
24
Q
What type of vector are biting midges for BTV?
A
- Biological vector:
- virus replicates in midge
- vector becomes infected by blood from an infected ruminant
- Etiological cycle between vector and susceptible ruminant
25
Q
Why are Culicoides biting midges important?
A
- >1400 species worldwide
- Different species transmit BTV, EHDV (many other viruses) in distinct global ecosystems
26
Q
How is BTV transmitted?
A
- Virus has high affinity for blood cells
- initially all blood cells than only erythrocytes
- NO replication in RBC
-
Prolonged viremia in presence of NAb
- Not persistent, generally < 60 days
- May be up to 11 weeks in cattle
- Can contribute to year-round transmission
- initially all blood cells than only erythrocytes
-
Primary Route: Vector
- Virus in secretions/excretions minimal
- direct/indirect/aerosol transmission unlikely
- Semen from viremic bulls potential source through natural breeding or AI
- Transplacental transmission in cattle reported
- Virus in secretions/excretions minimal
27
Q
What animals are primarily effected by BTV? Mortality?
A
- Most common in sheep - principally European sheep reeds
- Peracute to chronic course
-
Mortality rate highly variable 2-90%
- Peracute: may die within 7-9 d
- severe pulmonary edema, dyspnea, frothing from nostrils
- Chronic: may die after 3-5 seeks
- secondary bacterial infections
- Peracute: may die within 7-9 d
- Mild cases usually recover rapidly
28
Q
What production losses does BTV cause?
A
- Deaths
- unthriftiness
- wool breaks
- Reproductive losses
29
Q
What are the clinical signs of BTV in sheep?
A
- Incubation: 4-6 days
- Fever (105-107.5F)
- Listless/depression, reluctance to move
- edema of lips, nose, face, submandibular region, eyelids, ears
- Congestion/hyperemia of mouth, nose, nasal cavities, conjunctiva, and coronary bands
- lameness, hoof defects
- Serous nasal discharge (mucopurulent) dyspnea
- Sore muzzle
-
Blue tongue
- some have severe edema and cyanosis of tongue
- Reduced appetite, erosions/ulcers can occur in oral cavity
- Dermatitis may result in abnormal wool growth
- Muscle loss, torticollis
30
Q
What is the pathogenesis of BTV that allows for the clinical signs in sheep?
A
- Vascular endothelial damage
- Increased capillary permeability, intravascular coagulation
- edema, congestion, hemorrhage, inflammation, necrosis
- Increased capillary permeability, intravascular coagulation
31
Q
What is the pathogenesis and clinical signs of BTV in cattle?
A
- C/S rare but similar to sheep:
- Fever
- Increased respiratory rate
- lacrimation
- salivation
- stiffness
- Oral vesicles and ulcers
- hyperesthesia
- dermatitis
32
Q
What are the clinical signs of BTV in pregnant cattle/sheep?
A
- May abort or deliver malformed calves/lambs
- infection in early gestation
- Cerebral malformation
- Hydranencephaly, ,porencephaly
- Ataxia and blindness at birth
33
Q
What are the clinical signs of BTV in WTD and pronghorn?
A
- Severe hemorrhagic disease leading to sudden death
34
Q
What are the characteristic lesions of BTV found at necropsy?
A
- Petechiae, ecchymoses, or hemorrhage in wall and base of pulmonary artery
- Focal necrosis of papillary muscle of left ventricle
- Ulcers/hemorrhage/necrosis in oral cavity, tongue, esophageal groove, and omasal folds
- SQ, IM and LN edema and hemorrhage, skeletal myonecrosis and hemorrhage, myocardial and intestinal hemorrhage, pleural and pericardial effusion, pulmonary edema, pericarditis, and pneumonia
- Characterized by vascular permeability, thrombosis and tissue infarction
35
Q
How is BTV diagnosed?
A
- Consistent clinical signs and pathology
-
VI/PCR
- whole blood in anticoagulant
- Spleen, ln, bone marrow
- Antibody response detected 7-14dpi, generally lifelong
- AGID, ELISA
- Identity of isolate (serotype)
- can be performed on both virus and Ab
36
Q
How is BTV managed?
A
- No specific treatment
- Rest, soft food, husbandry
- Controlling secondary infections
- Vaccination
- Control of vectors
37
Q
What is the BTV vaccine?
A
- Modified live virus (MLV) and Inactivated vaccines commercially available
- In US:
- monovalent (BTV 10) MLV vaccine available for use in sheep
- MLV vaccine can cause abortion or malformation of fetuses when given in the first half (ewe) or first trimester (cow) of pregnancy
- Vaccination with different serotypes does NOT provide consistent cross-protection
- MLV vaccines should NOT be used during Culicoides season:
- insects may transmits the vaccine virus
- potential for reassortment, new viral strains
- insects may transmits the vaccine virus
38
Q
does BTV undergo genetic shift?
A
- Genetic shift by reassortment of gene segments during infection of insects or animals with more than 1 strain/serotype of BTV
39
Q
What are some concerns about the future of BTV?
A
- Climate changes: increased range of environment supportive of the vector?
- Additional emerging serotypes?
- different species virulence
- origin of virus
40
Q
What are the characteristics of Epizootic hemorrhagic disease virus (EHDV)
A
- dsRNA virus
- Nonenveloped
- Segmented genome
- >10 different serotypes worldwide
41
Q
What is EHDV?
A
- Non-contagious infectious arthropod-borne viral disease of domestic and wild ruminants
- Historically, a disease of WTD in NA - rarely a clinical disease of cattle
- Ibaraki virus - outbreak in Japan 1959
- Historically, a disease of WTD in NA - rarely a clinical disease of cattle
- Emerging disease in cattle: OIE notifiable since 2008
- Biological vector: Culicoides biting midge
- Immunological cross-reactivity with BTV
- Seasonal due to vector
- REPORTABLE
42
Q
What animals are hosts to EHDV
A
-
WTD most important
- Morbidity and Mortality may be as high as 90%
- varies between years and geographical locations
- Morbidity and Mortality may be as high as 90%
- Other wild ruminants may seroconvert:
- mule deer, pronghorn, black-tailed deer, red deer, elk, moose, bighorn sheep
- Cattle: subclinical infection common, outbreaks rare
- Culicoides sp. transmit virus to ruminants after external extrinsic period of 10-14 days
43
Q
What is the Pathogenesis of EHDV
A
- Viremia can be prolonged > 50d in the presence of NAb
- Virus associated with RBC
- Virus infects endothelium all tissues affected
44
Q
What are the clinical signs of EHDV in WTD?
A
- Incubation: 5-10d
- Fever, weakness, reduced appetite, excessive salivation, head and neck edema, hyperemia of conjunctiva and mucus membranes of oral cavity, coronitis, stomatitis
- Prolonged disease: ulcers on dental pad, hard palate, and tongu
- Terminal: excessive bleeding, bloody diarrhea, hematuria, death
45
Q
What are the clinical signs of EHDV in cattle
A
- Incubation: 5-10d
- Acute disease similar to BTV;
- fever, reduced appetite, conjunctival edema, redness and crusting of nose and lips, oculonasal discharge, stomatitis, salivation, lameness, tongue edema, oronasal erosion, dyspnea, coronitis, difficulty swallowing
- Abortions/stillbirths reported
- Mortality low (<10%)
46
Q
What lesions are common in WTD with EHDV
A
- Widespread hemorrhage and edema
- especially in heart and GIT
47
Q
jHow is EHDV diagnosed?
A
- REPORTABLE
- Differentials:
- WTD: BTV, FMDV
- Cattle, BTV, BVDV, FMDV, IBR, VSV, MCFV
- FAD investigation
-
VI/PCR
- whole blood in anticoagulant
- spleen, lungs, ln, liver
- Serology: paired serum samples
- AGID, ELISA, SN
48
Q
How is EHDV managed?
A
- Control Vector
- insecticides, repellents on susceptible ruminants, management of culicoides breeding areas
- NO VACCINE commercially available for preventing EHDV in US
