It is important that Irish producers are aware of the disease and the need to strictly comply with importation requirements to keep it out of Ireland.
Symptoms: Increased respiratory rate with a soft cough. Sheep remain bright with a good appetite unless a secondary bacterial pneumonia develops (this becomes more common in affected flocks). Later in disease, lots of clear frothy fluid flows from nostrils when head down.
Survival: Jaagsiekte sheep retrovirus (JSRV) will survive several weeks in the environment
Spread: By respiratory aerosol & via contaminated troughs & water. Transmitted via milk & colostrum. Uterine spread low if at all.
Pathology: Oronasal infection leads to a cancer in the lung with lots of white foaming fluid. Incubation is generally 3 years long but it can be seen from 2 mths to 11 yrs old
Diagnosis: No immune response so no blood serology possible. PCR is possible in the respiratory system & peripheral blood lymphocytes but it is not commercially available and it has a low sensitivity as virus levels fluctuate. Thoracic ultrasound can used to identify infected animals if the lesions are greater than 2cm and on the surface of the lung.
- Identify & cull infected ewes and their offspring.
- House & manage in single age groups – especially keep young sheep separate from adults
- Reduce close contact – consider housing, stocking density, trough feeding.
- Snatch lambing & rear artificially – shown to be successful in a German case study
Context: Prevalence of OPA in Ireland appears to be similar to the UK with JSRV-positive sheep identified in the counties of Donegal, Kerry, Kilkenny, Offaly, Tipperary, Waterford and Wicklow, often clustered within the same flocks. Nearly 2000 adult sheep were investigated and 1.6% were found to be infected with JSRV
and 0.5% with OPA.
Ovine Johnes Disease
Symptoms Sheep get very thin and emaciated but do not scour like
cattle with Johnes do. Increase in n and emaciated but do not scour
like cattle with Johnes do. Increase in culling rates due to poor
Survival 9 months in water, 11 months in slurry, 48
months in soil
Spread Ingested orally. Invades & multiplies in
small intestine lymphatic tissue & mesenteric lymph nodes. Shed
in faeces of clinical & pre-clinical cases. Found in milk &
placenta of clinical cases. Any age is susceptible but especially
Pathology 70% of cases are multibacillary – lots
acid-fast bacilli in mucosal macrophages. Villous fusion, gut
thickening, humoral antibody response 30% of cases are
paucibacillary –few or no bacilli. Cell-mediated response but
little gut change or antibody response.
Diagnosis ELISA test
detects 3-6 months post infection or AGIDT test – both have good
specificity but poor sensitivity (as low as 50% for paucibacillary
cases) – so lots of false-negatives. PCR on 50% for paucibacillary
cases) – so lots of false-negatives. PCR on faeces works well and
can pool faeces from up to 10 animals Most reliable diagnosis by
postmortem histopathology of small intestine and mesenteric lymph
1. Limit spread by early culling of clinical
cases & remove offspring.
2. Test & cull. Blood testing,
faecal culture or PCR two to four times a year. Expensive
Management – limit lambing in wetter areas. Keep young stock away
from adults. Use automatic water feeders & strict hygiene
Vaccine Gudair (Virbac) is now available in UK - suggest
vaccinated everything below one year old & all bought-ins.
Vaccinates will still shed Johnes in faeces & have detectable
Ab so not suitable for export. Review of several papers indicates:
Vaccination reduces culture +ve sheep >70%, lesions by 96%,
clinical cases by >50%
CLA - Caseous lymphadenitis
Symptoms Discrete swellings around the head and neck which can
burst to discharge a thick pus
Survival This bacterium with a lipid
coat survives for 8months in soil, 24h in dip Spread Incubation is
6 weeks - 4months as it spreads from infected wound to the draining
Spreads by close contact – at clipping, dipping,
especiallyshowering and post-dipping. Also respiratory spread in
droplets. Very low prevalence in sheep up to 1 year old and little
spread to pre-weaned lambs
Diagnosis Difficult to diagnose
(especially once the abscess becomes walled off) Blood test ELISA
(Sensitivity=87%, Specificity= 99%) which means a few false
positives & lots of false negatives. Confirm a positive by
Western Blot test. SAC Monitoring Scheme tested pre-sale (Isolate
for 12 weeks & then required 2 negative ELISA taken 6 weeks
Control options Restrict movement & contact with
infected flock. Avoid any nose-to-nose contacts at sale. Check
flock regularly. Handle young sheep first. Keep ram lambs separate.
Investigate suspicious cases. Avoid puncturing abscesses
unnecessarily. Don’t handle closely in dusty yards. Quarantine
infected premises for a long time.
Vaccine Glanvac available from
Zoetis Australia – VMD reports that approximately 25000 doses are
imported into UK each year & it is estimated that this is half
the total imported Research at Moredun has developed a DIVA vaccine
but not commercially available.
Is caused by a pestivirus with very similar
epidemiology to BVD in cattle. It is transmitted via the oro-nasal
route with the persistently infected (PI) animals as important
reservoirs of infection in a flock.
Pregnant ewes are at most risk
as they either abort or produce PI lambs that are either weak,
normal or ‘hairy shakers’ that continually shed virus.
Disease was considered fairly important in Ireland with a
prevalence of 5.6% of individuals and 46% of flocks though many of
these were found to actually be BVD virus and suggested to be a ‘
spill-over’ from cattle2 .
Hopefully these figures may have reduced
as a result of the cattle BVD eradication scheme.
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