Infectious (Iceberg) Dx in Sheep Flashcards
Describe common viral, bacterial, protozoal ?
Infectious causes of poor fertility?
- Chlaydophilia abortus AKA Enzootic Abortion of Ewes (EAE)
- Toxoplasma gondii
- * Campylobacter fetus fetus
* Salmonella
* Q fever
* Listeria monocytogenes
* Border disease
* Schmallenberg
* Bluetongue
* (Brucellosis- Brucella ovis)
What do we mean by Iceber diseases?
- Low Clinical Visibility
- Lack of availability of effective diagnostic testing
- High Subclinical PResence
- Economic & Health Impact
Jhone’s dx in sheep caused by ..?
Mycobacterium avium sbsp Paratuberculosis
Lon incubation , no tx
Johne’s seen in?
animals >2.5yrs - weight loss
CLS Johne’s ?
- Chronic weight loss despite normal appetite
- Poor fleece quality
- Bottle jaw in later stages
What is NOT a sign of JOHNES
NO Diarrhoea
What does Johnes indirect consequences?
More susceptible to other infections - mastitis etc
Lambs born to ewes in late stage = poor weight
Transmission of Johne’s?
- Ingestion of contaminated faeces by lambs
- Acquired in utero- less common
- Animals shedding without clinical signs
Jhone’s diagnosis?
Serum albumin and globin
- Profound hypoalbuminaemia
- Normal globulins
- PLE
Serum ELISA
- Low sensitivity & high Sp (high n° false neg)
- Individual testing expensive
Pooled faecal PCR (on cull animals to establish prevalence)
Jhones Control?
- Probably in all UK flocks
- Regular BCS
- Culling
- Testing of thin sheep/culls (PM, Pooled faecal PCR)
- Cull & re-stock with low risk ewes
- Vaccination
- CLOSED FLOCK
What is the agent for Caseous Lymphadenitis? (CLA)
Corynebacterium pseudotuberculosis
Transmission of CLA?
- Direct sheep-sheep during close confirnement or shearing equipment
- highly infectious
- Able to stay in environment for long time
What gross path of CLA?
Abscessation of superficial lymph nodes and LN of internal organs
Transmission of CLA
- sheep:sheep in close conact
- through contaminated equipment
- Rams head lesions whilst fighting
- Aerosol
- Shared dipping
Which superficial LNs affected by CLA?
- parotid, submandibular, popliteal, precrural and
prescapular - Easily spread when abscesses open
- Don’t often show clinical signs
What does Internal CLs cause?
= spread to internal lymph nodes
- thin ewes syndrome
- associated clinical signs e.g. dyspnoea
Diagnosis:
- Blood sample - western blor
- Interferon-Y
-Bacteriology
Tx & Management?
- difficult to treat as ABs can’t penetrate the fibrous capsule/ into abscess to work
PRevention LDA?
- Biosecurity & testing
- Shearing equipment /other equipment
- buy from dx free flock
Management of CLA?
Vaccination- not in UK-wont lead
to eradication
True positive Vs vaccinated
Test and Cull
Test entire flock at repeated
intervals and cull
Describe Ovine Pulmonary Adenocarcinoma/ Jaagsiekte
- Viral-induced Adenomatous lung tumours
- Jaagsiekte sheep retrovirus JRSV
Transmission of OPA?
- Horizontal transmission- ewe to ewe
- Aerosol and infected surfaces
- Prolonged incubation
- Age 2-4
CLS of OPA?
- Non-specific
- Chronic weight loss
- Progressive dyspnoea
- Respiratory distress
- Crackles
- High pitched moist lung sounds
- Death
- Build up of excessive fluid
- Free flowing frothy nasal
discharge - Secondary bacterial infection
Diagnosis of OPA?
- No serological test
- PME lesions=diagnostic
Ultrasound =>
* Early diagnosis (tumours >1cm)
* Before clinical signs
* Flock screening
What can we do to ‘find’ OPA?
Wheelbarrow test -> fluid comes out
Tx for OPA?
fatal/none
Prevention/Control OPA?
- Closed flock
- Buying from known dx free - history of no clinical cases
- Quarantine?
Management for OPA?
- Management of ewes in age groups
- Remove lambs from clinical animals
- Reduce environmental contamination
Prevention of OPA?
- Culling out at earliest signs
- Ultrasound screening
Describe Maedi Visna Virus?
➢ Small ruminant Lentiviruses
➢ Long incubation
➢ Horizontal spread- aerosol, faeces &
colostrum/milk
CLS of Maedi Visna?
➢ >3 years old
➢ Progressive wasting
➢ Progressive Interstitial Pneumonia
➢ Progressive neurological signs
➢ Ataxia and incoordination – toe dragging
➢ Weakness
➢ Paralysis
➢ Asymptomatic carriers
➢ Chronic mastitis or poor colostrum/milk
production
what does MAedi Visna mean?
➢ Maedi = ‘laboured breathing’
➢ Visna = ‘Wasting’ ‘shrinkage’
Subclin dx of MAedi Visna?
- Production limiting effects
- Lower conception rates
- Reduced longevity
- Lower milk yields
- Poor lamb production
- Chronic mastitis/inflammation
Diagnosis of Maedi Visna ?
Clinical signs
Postmortem-
* Enlarged heavy lungs with grey discolouration
* Impression of ribs
* Secondary bacterial pneumonia
* Raised mediastinal LNs
* Histopathology to confirm
Serology
- Long time to seropositive conversion
- Repeated testing (ELISA, AGIDT)
How to go about Maedi Visna Diagnosis?
MV control options?
Control & prevention ? (pt 1)
- Run a closed flock where possible once flock
health has been established. - Consider running shearlings/ewe lambs as a
separate flock. This enables monitoring of older
ewes and protecting replacements for as long as
possible before mixing. - Fence off water courses and limit lambing in wet
areas - Avoid mixing sheep close to tupping or during
pregnancy (border disease). - Handle young sheep first at
scanning/shearing/vaccination (contagious
lymphadenitis). - Dagging/lambing shed hygiene is important (Johne’s disease).
Control & prevention (pt2)
- Be vigilant with regards to fomites
- Consider fencing – escapee sheep from infected
neighbours are a real threat. - Take care with regards to pooled colostrum (maedi
visna/Johne’s disease/ovine pulmonary
adenomatosis) or cow colostrum. - Demand health status of purchased sheep
- Avoid buying through markets or dealers mixing sheep
from multiple sources.
