Infection with peste des petits ruminants virus

After an incubation of about 3-6 days, a sudden high fever appears with depression and loss of appetite, followed by serous nasal and eye discharge that turns mucopurulent and may crust over the nostrils. Within days the gums redden and necrotic erosions spread through the mouth with salivation, foul breath and crusted lips. Watery, sometimes bloody diarrhoea, coughing and laboured breathing follow; pregnant animals may abort, and death can come within 5-10 days. Necropsy shows erosive stomatitis, 'zebra stripe' congestion in the posterior colon, bronchopneumonia and enlarged lymph nodes.

Peste des petits ruminants (PPR) is caused by small ruminant morbillivirus (still widely called PPRV), a Paramyxoviridae virus related to rinderpest, measles and canine distemper viruses. There is one serotype and four genetic lineages; lineage 4 dominates outside Africa. After mainly respiratory entry, the virus damages mucosal epithelium, producing necrotic foci and shallow erosions in the mouth, pharynx, upper oesophagus and genital tract, necrosis of Peyer's patches and congestion of the large intestine. It also suppresses immunity, so concurrent bacterial and parasitic infections worsen. Bronchopneumonia is a constant lesion, and animals usually die from dehydration caused by diarrhoea, from pneumonia, or both.

Goats and sheep are the reservoir hosts; goats are usually hit harder. Clinical cases also occur in camels, water buffalo, gazelles, ibex and other wild ungulates, while cattle seroconvert without disease. The virus is shed in ocular and nasal discharges, saliva, urine, faeces and milk and spreads mainly by close contact and inhalation, with fomites playing a smaller role; there is no carrier state. Outbreaks rise with the rainy or cold dry season and with trade movements. PPR is endemic across much of Africa, the Middle East and Asia; lineage 4 reached Morocco in 2008 and later Algeria and Tunisia through cross-border animal trade. It is not zoonotic, is WOAH-listed and is targeted for global eradication by 2030.

Foot-and-mouth disease causes lameness but not breathing problems or diarrhoea. Bluetongue brings head oedema, bluish oral discoloration and coronary band lesions. Uncomplicated orf lacks oral necrosis, diarrhoea and pneumonia. Pneumonic pasteurellosis is purely respiratory, without mouth lesions or diarrhoea. Contagious caprine pleuropneumonia affects only goats, has no oral lesions and leaves fibrinous fluid in the chest. Rinderpest (now eradicated) needed contact with sick cattle. Heartwater, coccidiosis and Nairobi sheep disease are also listed differentials.

Oral mucosa, lips, respiratory tract, lungs, abomasum, small and large intestine, Peyer's patches, lymph nodes, eyes and conjunctiva, genital tract, immune system

Vaccination in endemic regions (live vaccines can give lifelong immunity); import testing and quarantine; movement controls, culling and disinfection in outbreaks; keep flocks apart from wildlife.

No specific treatment; supportive care and treating co-infections may cut deaths. Naive flocks: morbidity 90-100%, mortality 50-100% (WOAH); case fatality 80-90% (CFSPH). Endemic areas: as low as 10-20%. Survivors convalesce slowly, keep long immunity.

Wild small ruminants and antelopes