Red Meat Pathology 1: Sheep

Most lesions in sheep are usually seen in the ____.

Lungs

Describe the classic appearance of enzootic pneumonia.

• Local Rejection of Lungs

• Cranioventral consolidation - caused by mycoplasma ovipneumoniae

Describe the classic appearance of fibrinous pneumonia.

• Local Rejection of lungs

• Bilateral or unilateral - caused by mannheimia haemolytica

Describe the classic appearance of ovine pulmonary adenocarcinoma.

• Pink areas of central consolidation

• Local rejection of lungs

Also find frothy fluid in airway

• Caused by JSRV: Jaagsiekte Sheep Retrovirus

Describe the classic appearance of verminous pneumonia - muellaris capillaris.

• Common agent is muellarius capillaris - multifocal lesions on the dorsal aspect of the lungs

• Also causes lead shot lesions - chronic lesions

  • Tend to coalesce and get larger

• Acute lesions: hemorrhagic, very congested

• Larvae in interstitium - adults in bronchi + bronchioles

di

Describe the classic appearance of verminous pneumonia - dictyocaulus filaria.

• Adults found in bronchi - larger airways

Describe the classic appearance of lung abscesses.

Describe the appearance of hydatidosis.

• regional incidence

• intermediate stage Echinococcus granulosus

• cysts usually in lung

• other major organs possible eg liver

• unilocular, fluid-filled, thick capsule

• REJECT pluck and any affected organs, carcass goes through

• zoonosis - check farmer and family

Describe the appearance of caseous lymphadenitis.

• Corynebacterium pseudotuberculosis

• lungs only = LOCAL

• check rest of carcase though!

Describe the appearance of maedi visna.

Viral Pneumonia - overinflated lungs (Retrovirus)

• Lungs palpate - rubbery

Describe the appearance of blood splashing.

• sudden blood pressure increase due to electrical stunning

• ecchymotic or petechial haemorrhages

• lung, heart and occasionally skeletal muscle

• if numbers increase

• check

• stunning procedure

• amperage may be too high

Describe the appearance of pericarditis.

• part of the pasteurellosis complex

• acute pericarditis

• fibrinous exudate

• RARE in abattoir

• residue lesions more common

• fibrous adhesions between layers of pericardial sac

Describe the appearance of cysticercosis or sheep measles.

CYSTICERCOSIS (C. ovis) also called Sheep Measles

• dog tapeworm

• Taenia ovis

• sheep ingest dog faeces

• Intermediate host

• larvae develop in sheep muscles

• Cysticercus ovis

• check heart, diaphragm and other skeletal muscles including the heart, diaphragm, and skeletal muscles

**NB: MOC: Meat infected with cysticerci shall be declared unfit for human consumption. However, where the animal is not generally infected with cysticercus, the parts not infected may be declared fit for human consumption after having undergone a cold treatment. Individual/low numbers of cysts found = local. Generalised = total.

Describe the appearance of osteomyelitis.

• Osteomyelitis is a serious infection and inflammation of the bone and bone marrow, usually caused by bacteria (such as Staphylococcus aureus)

What species account for the main rejections or causes of liver damage in sheep?

Fasciolosis and cystericosis

Describe the main features of fasciolosis.

Describe the pathology caused by the migratory phase of fasciolosis.

**Possible sequela - vessel rupture - massive haemorrhage

Describe the pathology caused by chronic fasciolosis.

Describe the main features of cysticercosis c. taenuicollis.

• Causes serpentine lesions in livers as well

Describe the main pathological features of grid in sheep.

Coenurus cerebralis = larval form of dog tapeworm Taenia multiceps occasionally infests other ruminants

Larva enters CNS by haematogenous route zoonosis

Clinical Signs: relate to space occupying lesion in brain or cord (blindness, nystagmus, deviation of head, eyes, ataxia, collapse)

Diagnosis: Parasitic induced cerebral cysts

Cause: Coenurosis due to Coenurus cerebralis, the immature stage of the tapeworm seen as the adult Taenia multiceps in the canids.

What are the main control measures to minimize the incidence of taenia spp. infections in sheep?

• don't feed farm dogs with uncooked meat / raw diet

• remove carcasses of dead sheep as soon as possible

• dispose of sheep carcasses as ABP category 2

• regular dosing of dogs with anthelmintic (praziquantel)

• at least every three months

• farmer to put notes in public footpaths running through sheep fields explaining the disease risks and encouraging dog walkers to worm their dogs regularly

Describe some common kidney pathologies.

Describe the main pathology caused by Johne’s bacteria.

• Most affected area is the ileum

• Check mesenteric lymph nodes

• Mycobacterium avium subsp. paratuberculosis

Describe the main features of small intestinal adenocarcinoma.

“Kissing tumour”

What are the main causes of pallor (Due to anemia) in sheep?

What are the main causes of carotenoid pigment accumulation in adipose tissue?