Hyperacute:

Suddendeath

Acute: 

Sudden onset anorexia and dullness
pyrexia
hyperpnoea/dyspnoea
serous ocular and nasal discharges
frothy fluid at the mouth in the terminal stages.

Sub-acute and chronic presentations: as above but more transient/milder, may lead to ill thrift. Most common to see outbreaks in May-July. Morbidity typically 10%, mortality 2%. 

Important cause of sudden death in lambs up to 12 weeks old.

Clinical signs:

Depressed, easily caught
Injected mucous membranes
Marked dyspnoea.
Usually pyrexic (rectal temperature >40.0C). 

Pathology: pleurisy and pericarditis with petechiae in the myocardium, spleen, liver and kidney, enlarged lymph nodes and hepatic fatty change 

- Nasal swabs and serology are of no use.

- Diagnosis by clinical signs and post-mortem findings,

- bacteriology from untreated cases (lung, liver, kidney, spleen, thoracic fluid, heart blood).

- Congestion without consolidation in hyperacute cases resembles clostridial disease, autolysis etc. 

•   Haemorrhages over neck and thorax, pleura, diaphragm and epicardium.
•   Swollen lungs with haemorrages and blood stained froth in airways – no
• consolidation.
•   Necrotic erosions in pharynx around tonsils, nasal mucosae and upper
• alimentary tract.
•   Liver congestion with necrotic infarcts in liver, kidney and spleen. 

- Infection appears common in young lambs, mostly causing transient or persistent inapparent infection. May also cause enteritis.

- Vaccination practiced in Hungary, where adenoviruses seem to be important pathogens in large feedlots.
RSV, Reovirus etc no major role demonstrated. 

A non-progressive chronic pneumonia of housed sheep under a year old caused by Mycoplasma ovipneumoniae, and possibly Chlamydia psittaci. Predisposing factors may include PI3 and M. haemolytica.

A chronic soft cough with some mucopus nasal discharge that spreads slowly through a group of lambs. Some dullness and tachypnoea, growth rates are reduced. Some develop 2 pasteurellosis. 

Red-brown or grey consolidated then later collapsed areas in the apical and cardiac lobes. Histology shows a lymphocytic cuffing pneumonia with pseudoepithelialisation of the alveoli and hyperplasia of the bronchial epithelium. 

The most pathogenic lungworm in sheep is Dictyocaulus filaria. Deaths are uncommon, but it may cause outbreaks of coughing and weight loss in the late autumn/early winter. Infection may trigger 2 pasteurellosis.
The life cycle of Dictyocaulus filaria is similar to D. viviparus. First stage larvae are passed in the faeces, which develop to infective L3 on pasture. Spring pastures are infected by overwintered larvae or via faeces of ewes or hoggs. Clinical disease is seen in the autumn, with adult worms in the bronchi. 

0. This follows pneumonic pasteurellosis (or atypical pneumonia) and occurs when pockets of bacterial infection persist, and are walled off as chronic abscesses in the lung tissue or pleural space. It may also be caused by bacteraemic spread from a septic focus. Bacteria involved may include Mannheimia haemolytica, Arcanobacterium pyogenes, Pasteurella multocida and Escherichia coli. Other causes of lung abscesses may include CLA (Corynebacterium pseudotuberculosis) and tuberculosis. 

•   Weight loss / ill thrift in individual animals

•   Mild fluctuating pyrexia or normal temperature

•   +/- dyspnoea/purulent nasal discharge, or no respiratory signs

•   +/- muffling on thoracic auscultation 

• History, clinical signs

•   Ultrasonography

•   Hyperglobulinaemia (>50g/l)- due to chronic inflammation 

•   PM examination

•   (Radiography) 

• Incubation period several months

•   Disease in 2-4 year old sheep, occasionally in the yearling lambs of infected

  dams

 Early

clinical signs: 

loss of body condition exercise intolerance serous nasal discharge

o episodes of mouth breathing o appetite OK, afebrile

 Then:

o

nostrils when the head is lowered o soft cough

o fluid sounds may be heard on auscultation, ventral and cranial 

Death frequently follows secondary infection with Pasteurella haemolytica with

depression, anorexia, pyrexia. Temporary response to antibiotics. 

Tumour of type II pneumocytes ( surfactant) which replace normal alveolar cells. Tumours are confined to the lungs which are enlarged and heavy (>2 kg). Tumours usually occupy the anteroventral lung fields, are solid and grey and are well demarcated from normal lung tissue. Lesions may contain abscesses, or be hidden by extensive pleurisy. Bronchi and trachea contain copious frothy fluid. 

Etiology
A lentivirus causing respiratory disease (maedi), nervous disease (visna), mastitis and arthritis. 

Diagnosis on the basis of clinical signs alone is not satisfactory due to the range of clinical signs and the fact that most cases occur in older sheep with concurrent infections. Diagnosis may be masked at post mortem examination by pneumonic pasteurellosis or pulmonary adenomatosis.

Histological diagnosis may be no more reliable, as the lesions are not pathognomic e.g. smooth muscle hypertrophy may occur with lungworm infection, infestation and lymphoid infiltration with mycoplasma and chlamydial infections.

Diagnosis, therefore, relies on detecting antibody to the virus by the agar gel diffusion test (AGID). This test is the basis of the MVV accreditation scheme. Unfortunately some animals never develop antibodies, and because the AGID test is not particularly sensitive, it can not detect recently infected sheep. ELISA tests with higher sensitivity have now been developed. 

•   Texel and Suffolk (Tups more commonly affected?)

•   Short neck confirmation plus ?trauma/dust/infection leads to oedema, respiratory

  distress and arytenoid abscessation

  CLinical signs: 

  0. Pronounced inspiratory stridor and dyspnoea Tachypnoea and orthopnoea

     Pyrexia
     Treatment: Steroid IV( dexamethasone 20mg)  and antibiotic (macrolide) 7-10 days ab ( tulathromcin, synulox) 

     Prognosis: guarded at best, many recur within 1 month. Should these animals be retained for breeding? 

   Control: 

  early ID and treatment

  reduce concentrate feeding

  avoid trauma

  improve ventilation

  conformation=breeding