Chronic wasting in sheep and goats Flashcards
Presentation of chronic wasting: Individual animal
- Syndrome – many causes of a similar presentation
- Adults over one year, typically 3 – 5 years
- Affects single to few animals at a time but
> Several individuals over time
> May indicate a higher proportion of flock infected - Thinner than cohorts
- Thinner than expected
> BCS goals/scoring info available (supplemental) - Fail to respond to good nutrition
Presentation of chronic wasting: Group or flock level
- If group is too thin
- Inadequate nutrition for stage of production
- Feeding management
Common causes of chronic wasting
- Competition
- Dental disease
- Retroviral diseases > Maedi visna (sheep), Caprine arthritis encephalitis (goats)
- Paratuberculosis (Johne’s disease)
- Caseous lymphadenitis
- Enzootic nasal adenocarcinoma
- GI parasitism (more common in adult goats than sheep)
- Lameness (will cover in another section)
Competition - ways it arises
- Inadequate feeder space
> Pregnancy status
> Ad-lib versus limit fed - Mixing (size, age, pregnancy status)
- Horned versus no horns
- Species
- Breed
Dental disease
- presenting complaint
- epidemiology
- “broken mouth”
- Presenting complaint & history
> Adult usually 4 years or older
> Sporadic, low incidence - Epidemiology
> Some farms worse than others
> Risk factors not well understood
Dental disease - Pathogenesis, clinical presentation
- Normally OK until 7 or 8 years of age
- Primary gingivitis
- Tooth loss and abnormal wear
- Secondary osteomyelitis
<><><><>
Clinical Presentation - Thin, ≤ BCS 2
- Appetite but slow eating
- Decreased cud chewing
- Swellings on jaw
Dental disease – Clinical exam
- Pull down lower lip
> Loss of incisors – broken mouth
> Clinical significance? depends on diet, worse for pasture
<><> - Palpate dental arcade for uneven wear
<><> - Osteomyelitis associated with dental disease
Dental disease – Post mortem findings
- Tooth loss and uneven wear
- Osteomyelitis
- Long stems in rumen (poor mastication)
- Soft tissue infection
Dental disease – Treatment & control
Treatment
* Usually none
> Pets: rasp premolars and molars
* Recognize and cull or euthanize depending on fitness for transport
<><>
Control
* Grazing poor quality soil
* Thistles and awns in hay
Maedi Visna - Epidemiology
- geography
- prevalence
- effect on production
- Widespread throughout the world
> Except Australia and New Zealand
<><> - Canada – high prevalence
- Within flock seroprevalence
> 20 to 40% up to 90-100%
<><> - Seroprevalence increases with age
<><>
Effect on productivity: - Reduced reproductive performance
- Early culling of adults
- Reduced lamb growth & survival
Maedi Visna (aka Ovine Progressive Pneumonia)
- what does it mean??
- nature of the pathogen
- presenting complaint and history
- Maedi = dyspnea
- Visna = neurological disease with wasting (but neorologic signs are rare)
<><> - Small ruminant lentivirus
- Two groups (one common in sheep, one in goats) but each can infect the other
<><> - Presenting complaint and history:
- Adult sheep
- Dyspnea / productive cough
- Exercise intolerance
- Hard udders at lambing with insufficient milk
- Often unrecognized
Maedi Visna
- Pathogenesis
- target tissues
- Chronic active inflammatory process
> Virus targets macrophages, stimulates lymphocytic proliferation
<><><>
Target tissues: - Mammary gland
- Lungs
- CNS
- Joints
Maedi Visna - Transmission
- Aerosol – respiratory secretions !!!!!!!!!!
- Colostrum !!!!
- Milk !!
- In utero transmission !!
- Blood contaminated instruments / needles +/-
- Semen – white blood cells +/-
<><><><> - Can be infected multiple times!
Maedi Visna – Presentation – Respiratory disease
- Common presentation
- Afebrile, bright and alert
- Productive cough
- Exercise intolerance
- No response to treatment
- Progressive & 100% fatal
Maedi Visna – Presentation – Udder
- Lymphocytic mastitis
- Common presentation
- “hard bag”
> Udder uniformly firm to touch
> Milk normal but decreased
> Negative CMT - Lambs hungry
> Steal milk or starve
Maedi Visna – Less common presentations
Neurological (Visna)
* Hind end ataxia and paresis – paralysis
* Circling, head tilt
* Fine tremor of lips
<><>
Arthritis
* Carpus, stifle, hock
* Uncommon except in some flocks
Maedi Visna – Diagnostics
Serology – ELISA
> Good sensitivity and specificity
* Seroconversion variable time
> 2 weeks to 6 months
* Offered by the AHL (Guelph)
Maedi Visna – PM lesions
Postmortem
* Lungs are tanned coloured, highly cellular, firm, heavy
* Worse affected dorsally
* Histopathology reveals lymphoid follicles
* Large, heavy lungs ,imprint of esophagus, thick mucous in trachea
Maedi Visna – Treatment and Control
Treatment
* None - euthanize
* Necropsy adults with chronic wasting & non-responsive pneumonia
<><><><>
Control
* Serological testing of adult sheep
* Culling to slaughter
* Market this year’s offspring of seropositive ewes
* Test all replacement stock
<><><><>
* Ontario Maedi Visna Flock Status program
Caprine Arthritis Encephalitis (CAE)
* Presenting complaint and history
* etiology? pathogens?
- Goats with enlarged joints, lameness – may progress to recumbency
- Chronic wasting
<><><><>
Etiology - Caprine arthritis encephalitis virus (CAEV)
- Genus lentivirus – small ruminant lentivirus (SRLV) * Possible for cross-infection with sheep to occur
Caprine Arthritis Encephalitis (CAE)
- common in what animals?
- prevalence
- pathogenesis? similar to?
- Very common in dairy and meat
- High seroprevalence
- Similar pathogenesis as for Maedi Visna
Caprine Arthritis Encephalitis (CAE)
- transmission?
- Aerosol, saliva & genital secretions (esp. confinement) !!!!!!!!!!!!
- Colostrum & milk of infected does (1 mL)!!!!
- Milking equipment (adults)!!
- In utero transmission (3 to 6%)!!
- Blood contaminated instruments, needles +/-
Caprine Arthritis Encephalitis (CAE)
* Clinical findings
- Arthritis and bursitis
> Carpus, stifle, scapula, occipital joint - Arthritis progresses to contracted tendons secondary to recumbency
- Udder
> As for MV
> Hard at freshening
> Little milk but normal appearing
> CMT normal - Milk production ~ 10% less than non-infected does
<><><><><><><>
(uncommon) - Neurological
> Kids 1 to 5 months
> Posterior paresis > Uni- or bilateral progresses to tetraparesis
> Torticollis - Progressive Pneumonia
> Like MV
Caprine Arthritis Encephalitis (CAE)
Diagnostics
- Serology
- Note: seroconversion can be delayed
