Lecture 12: Small Ruminant Viruses Flashcards
What is virus induced transformation and how does it happen?
- Transformation: normal cell turning into neoplastic cell
o Genetic changes in: cell proliferation/differentiation/apoptosis
o Proto-oncogenes (promote growth), tumor suppressor genes (rregulate protooncogenes) - Oncogenic viruses: viruses that lead to tumor formation
What is the agent causing ovine pulmonary adenocarcinoma
Ovine Pulmonary Adenocarcinoma (OPA)
* Many names: Jaagsiekte
* Agent: Jaagsiekte sheep retrovirus
What is the mechanism of ovine pulmonary adenocarcinoma
- Mechanism: epithelial cells in bronchioles and alveoli (type 2 pneumocytes)/lymphocytes/myeloid cells
o Carry oncogene (E – protein, envelope protein) - Pathogenesis: go to lung and infect type 2 pneumocytes
o Infect lymphoid and myeloid cells
o Virus replicate and express E-protein
Transform type 2 pneumocytes
o Tumor growth and metastasis to LN +/- 2 infection
o Increased fluid production in lung (from tumors) – excrete into environment
o Large tumors and necrosis and death
Where is ovine pulmonary adenocarcinoma located
- Prominent worldwide: NA/Asia/Africa/SA – wherever there are sheep (except Iceland and Australia/NZ)
What does ovine pulmonary adenocarcinoma target and what are the clinical signs
- Target: sheep <7-9mo
- Clinically: in sheep >2yo (2-4yo) fatal after onset of clinical signs
o In recently infected flocks = higher mortality (30-80%)
o Flocks infected for a while = lower mortality (1-5%)
o Dyspnea/ cough – chronic respiratory signs
o Large amounts of clear frothy fluid
o Progressive weight loss
o Wheelbarrow test: lift hind legs and lower head to collect respiratory fluid
Does not detect all sheep with tumors (must be productive/later stage) = negative doesn’t mean free of disease
o Carriers are subclinical
How is ovine respiratory adenocarcinoma transmitted
- Transmit: respiratory via aerosol/droplet or milk/colostrum
o Infected animals are lifelong carriers
o Incubation 3-36mo
What are the histologic and gross features of ovine pulmonary adenocarcinoma
- Histo: IHC and IF visualize viral proteins (evidence of viral replication via detecting viral proteins)
o Antibody detect via ELISA
o Antigen detect via ELISA - Gross: frothy trachea and nares
o Enlarged and edematous lungs (fail to collapse)
o Focal to diffuse bulky mass
o Between normal lung architecture and tumor (potentially abscesses in tumors if 2nd infection)
o Enlarges bronchial and mediastinal LN (10% contain metastasis)
How is ovine pulmonary adenocarcinoma diagnosed and treated
- Dx:
o Clinical: not certain because there can be 2nd infection confounding
o Lab:– use BAL fluid for RTPCR
No serology - Ig’s to this virus not detected in serum (b/c no immune response - Tx: none
o No immune response because there are endogenous retrovirus elements in thee sheep genome = cannot develop vaccine because it will induce autoimmune rxn - Prevention: most animals can carry without clinical signs
o Test + quarantine prior before introducing into flock (but incubation is long time)
o Single age herd preferable (prevent introducing new infected)
o Hand raise lambs with milk replacer (because it is transmitted by milk)
What is another name for Maedi-Visna and what type of virus is it
Ovine Progressive Pneumonia (OPP)
* Lentivirus – retrovirus
How is Maedi-Visna transmitted and what are the clinical signs
- Clinically: most subclinical but some develop fatal disease
o Dyspnea (Maedi)
o Neurologic signs (Visna)
o Reduced milk prod - Transmit: respiratory/colostrum
What are the gross features of Maedi-Visna infections
- Gross: lungs fail to inflate and contain coalescing multifocal gray-white nodules + atelactic nodules in parenchyma
o Lung – swollen and heavy/not deflated
o and trachea – thickened mucosa
What are the 2 types of Maedi-Visna infection
- Visna form: rare - fatal
o Brain and spinal cord affected: hindlimb weakness/ataxia/tremor/paresis/paralysis - Maedi form: respiratory form + mastitis and arthritis + 2 bacterial infections
How to diagnose and control Maedi-Visna
- Dx: Agar gel immunodiffusion test/western blot/ RTPCR
- Control: avoid feeding colostrum but virus may have transplacental mechanisms
What type of virus is caprine arthritis and encephalitis virus
Caprine Arthritis and Encephalitis
* Lentivirus
What animals are affected by caprine arthritis and encephalitis virus and how is it transmitted
- Mainly goats (also sheep)
- Transmit: colostrum and milk
What are the 4 clinical/pathological manifestations of caprine arthritis and encephalitis virus
- Clinically: most subclinical – 20% develop into progressive/untreatable dz
o Poly arthritis – adult
Swelling around carpus +/- pain and thickening around joints (proliferative and fibrinous synovitis)
Synovial membrane – edema/hypertrophy/fibrosis/mineralization/necrosis
Multinucleated syncytia
o CNS: Encephalomyelitis – kids
Hind limb paralysis/head pressing
Invade into white matter
Lesions: perivascular cuffing/destruction of myelin/discoloured spinal cord and brain/accumulation of mononuclear cells/meningitis
o Indurative mastitis (hard udder due to lymphocytic infiltration) = reduced milk production
o Chronic interstitial pneumonia
What cell types are targeted by caprine arthritis and encephalitis virus
- Target: macrophage/DC/synovial membrane cells
How to diagnose and control caprine arthritis and encephalitis virus
- Dx:
o Clinically: young (encephalitis + ataxia and inability to adduct hindlimbs)
If older: arthritis, weight loss, and poor hair coat
o Path: lymphopenia if chronically infected/marked pleocytosis in CSF/red tinges synovial fluid with high mononuclear cell count
o Lab: AGID/ELISA
Also western blot radioimmunoassay/virus isolation/RTPCR/IHC - Control: no cure/vx
o Prevent vertical transmission via colostrum and milk
o If you get 2 negative tests (AGID) 6 months apart = animal negative
Another name for orf
Contagious Ecthyma/Orf
HHow is orf transmitted, what species does it target, and what type of virus is it
- Target: sheep and goats (also alpaca/muskox/big horned sheep/dogs) – zoonotic
o High risk for farmers, abattoir workers, vets, shearers - Poxviridae – parapox virus – orf virus
o enveloped - Replicate in epithelial cells (in localized lesions
- Transmit: cut/abrasion – resistant to the enviro because the keratin of the skin protects them
incubation period for orf
- Incubation 2-3d
What are the clinical signs of orf
- Clinically: resolve in 4 weeks – high morbidity and low mortality
o Initial papules/pustules/vesicles with inflammation and ulceration – progress to thick brown scabs - Path: target organ (skin/mucosa) – mouth/nose/eyes/eyelid/feet/udder/perineum
What are histo changes of orf
- Histo:
o Cells (epitheliotropic virus/epidermal keratinocyte)
o Leading to ballooning degeneration of epithelial cells
o Replicated in the cytoplasm – intracytoplasmic inclusions (pox virus)
How to control orf
- Vaccine: vaccines will induce classical lesions of the disease…
o Shed virus
o Vaccine can infect humans
o Doesn’t produce long lasting immunity
What type of virus is blue tongue? What species does it target
Bluetongue
* Reoviridae – obivirus – bluetongue virus
o Many strains (27)
* Target: sheep/cattle/deer/goat/camelid – sheep most severe, cattle – main reservoir
How is bluetongue transmitted and where?
- Transmit: Culicoides midges (biting midget) – late summer and fall, can carry virus long distances
- In tropical regions – emerging in CA due to climate change
What are the clinical signs of blue tongue
- Clinically (sheep): fever/eye and nasal discharge
o Drooling (due to ulcers in mouth)
o Swelling of head and mouth and neck
o Lameness and inflame at coronary band
o Difficulty breathing
o Abortion and developmental abnormalities
o Serotype 8: Cerebellar aplasia – circling/head pressing/staggering - Clinically (deer/goat/cattle) – mild, self-limiting
Caprine arthritis encephalitis (CAE) is characterised by progressive clinical
syndromes. What is your approach to control this disease? (3 marks).
Answer:
1. No cure and no effective vaccines available,
2. Prevent vertical
transmission through milk and colostrum and
- Establish a CAEV free farm-
2 negative AGID tests 6 month apart. Cull the positive animals and keep the negative animals
Against Jaagsiekte disease developing a vaccine is not recommended.
Why? (2 marks)
Answer: Approximately 20 copies of enJSRVs integrated in the sheep
genome. enJSRVs are expressed in sheep reproductive tract→ may induce
autoimmune inflammatory reactions when vaccination is attempted
breaking the tolerance.
What is TRUE relevant to ovine pulmonary
carcinoma/Jaagsiekte disease
a Is caused by a virus belonging to the Reoviridae family
b Can be transmitted by biting midges
c Wheelbarrow test can be used to detect excess fluid in
lungs in some of the sheep with tumors
d Rising antibody titers determined by paired serum
samples are diagnostic
e Dry trachea and nares are suggestive of the disease
C
Two viruses that can be transmitted via feeding colostrum
are
a Bovine corona virus and orf virus
b Bovine respiratory syncytial virus (BSRV) and blue
tongue virus
c Bovine viral diarrhea virus (BVDV) and blue tongue virus
d Bovine leukosis virus and caprine arthritis encephalitis
virus
e Bovine herpes virus 1 and Orf virus
D
What is FALSE relevant to clinical manifestation of caprine
arthritis and encephalitis (CAE) virus infection
a Leads to polyarthritis in adults
b Causes polyarthritis in kids
c Encephalomyelitis is common in kids and adults can be
affected
d Leads to indurative mastitis
e Causes chronic interstitial pneumonia
B
What is TRUE relevant to orf/ contagious ecthyma
a The causative virus is enveloped and not stable in
the environment
b The causative virus is epitheliotropic
c The vaccines are effective in inducing long lasting
immunity with no side effects
d Primarily affects goats but not sheep
e Due to the narrow host spectrum human infections
are not possible
B
