A050 - PESTE DES PETITS RUMINANTS

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A050 - PESTE DES PETITS RUMINANTS

Nature of the disease
Peste des petits ruminants (PPR) is a highly contagious disease of goats and sheep caused by a Morbillivirus close to Rinderpest virus and characterised by fever, necrotic inflammation of the mouth, enteritis and high mortality.
Classification
OIE List A disease
Susceptible species
Goats and sheep are the natural hosts of PPR. Goats appear to be more susceptible and suffer a more severe clinical disease than sheep. The American white-tailed deer and some African wild species of Ruminant are also sensible. 

Cattle and pigs develop silent infection.

Distribution
PPR is endemic in sub-Saharan Africa, extending to the Arabian peninsula. It is also present in Middle Eastern countries and India.
Clinical signs 
The disease begins with a sudden onset of fever. There is:
  • Fever (41°C)
  • Severe depression and loss of appetite
  • Watery nasal discharge progressing to profuse muco-purulent discharge with catarrhal exudate occluding the nostrils
  • Respiratory distress and sign of broncheupnomonia
  • Conjunctivitis with sometimes catarrhal conjunctivitis
  • Necrotic lesions in the mouth (dental pad, hard palate, cheeks) progressing to erosions with tags of epithelium
  • Severe diarrhoea, dehydration and weight loss
  • Abortion
  • Mortality rate 55-90%

In sheep the disease tends to be milder. It can be present in goats without affecting sheep.

Post-mortem findings 
In acute cases, the following can be seen:
  • Carcase will be dehydrated with faecal soiling
  • Necrotic lesions in the mouth and nose
  • Congestion of the ileocaecal valve
  • Engorgement and blackening of the folds in the caecum, colon and rectum (‘zebra striping’)
  • Enlarged spleen
  • Oedematous lymph nodes
  • Bronchopneumonia
Differential diagnosis 
Specimens required for diagnosis 
Whole blood collected on heparin (blood and anticoagulant should be mixed gently) should be submitted for serological diagnostic. Serological tests include Virus Sero-neutralisation ( recommended by OIE), competition ELISA, Counter immunoelectrophoresis, Agar gel immunodiffusion and Immuno-diffusion inhibition test.

Samples can also be submitted for identification of the agent. Such techniques include detection of the antigen by immunologial method (counter immunoelectrophoresis, ELISA...) virus identification, and virus RNA detection using PPR-specific DNA probes or amplification by polymerase chain reaction (PCR).

For these methods specimen can be collected on live animals: swabs of the eye (conjunctival sac), nasal secretions, and mouth and rectal lining, clotted and whole blood (with EDTA anticoagulant) or at post-mortem: fresh and preserved samples of tonsil, tongue, spleen, lymph nodes, affected areas of the alimentary tract mucosa.

Transmission   
PPR virus survives poorly outside the host. Spread of infection to new areas is largely by the movement of infected animals. Transmission is usually by direct contact via aerosols.

Virus is present in semen and embryos.

Feeding milk from infected animals to kids or lambs can spread infection.

Risk of introduction   
Since importation of small ruminants from endemic countries is not permitted, and as the virus survives poorly outside the host, the risk of introduction to Pacific island countries is low.
Control / vaccines  
To eradicate the disease, stamping out, systemic vaccination or a combination of both may be used.

An attenuated cell culture-adapted rinderpest virus vaccine provides protection against PPR for at least four years. NB - this vaccine will affect any subsequent surveys for evidence of rinderpest. 

A French attenuated PPR virus vaccine is also available. This has proven effective in field trials, providing immunity for at least three years.

References
  • GEERING WA, FORMAN AJ, NUNN MJ, Exotic Diseases of Animals, Aust Gov Publishing Service, Canberra, 1995, 440p
  • Office International des Epizooties, 2002
  • Peste des Petits Ruminants, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 539-541