Peste des petits ruminants
Aetiology Epidemiology Diagnosis Prevention and control References
AETIOLOGY
Classification of the causative agent
Virus family Paramyxoviridae, genus Morbillivirus. Antigenically close to rinderpest virus
Resistance to physical and chemical action
Temperature: Some virus may resist 60°C/60 min pH: Stable between pH 4.0 and 10.0 Chemicals: Susceptible to alcohol, ether, detergents Disinfectants: Susceptible to most disinfectants, e.g. phenol, sodium hydroxide 2%/24 hours Survival: Survives for long periods in chilled and frozen tissues EPIDEMIOLOGY
- Morbidity rate 90% (susceptible population)
- Mortality rate 50-80% (susceptible population)
Hosts
- Sheep and especially goats. To date diagnosed only in captive wild ungulates from families of Gazellinae (dorcas gazelle), Caprinae (Nubian ibex and Laristan sheep) and Hippotraginae (gemsbok)
- Experimentally the American white-tailed deer (Odocoileus virginianus) is fully susceptible
- Cattle and pigs develop inapparent infections
- Breed-linked predisposition in goats
Transmission
- Direct contact between animals
- No carrier state
- Seasonal variations: more frequent outbreaks during the rainy season or the dry cold season
Sources of virus
- Tears, nasal discharge, coughed secretions, and all secretions and excretions of incubating and sick animals
Occurrence
PPR occurs in Africa, the Arabian Peninsula, the Middle East and India
For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin
DIAGNOSIS
Incubation period is 3-10 days.
Clinical diagnosis
Acute form
- Sudden rise in body temperature (40-41°C) with effects on the general state: restlessness, dull coat, dry muzzle, depression of appetite
- Serous nasal discharge becoming mucopurulent and resulting, at times, in a profuse catarrhal exudate which crusts over and occludes the nostrils. Respiratory distress
- Small areas of necrosis on the visible nasal mucous membrane
- Congestion of conjunctiva, crusting on the medial canthus and sometimes profuse catarrhal conjunctivitis
- Necrotic stomatitis with halitosis is common
- Severe non-haemorrhagic diarrhoea
- Bronchopneumonia evidenced by coughing is a common feature
- Abortion
- Dehydration, emaciation, dyspnoea, hypothermia and death within 5-10 days
Peracute form
- Frequent in goats
Subacute and chronic forms
- Frequent in some areas because of local breed susceptibility
- 10-15 days development with inconsistent symptoms
- Pneumopathy
Lesions
- Emaciation, conjunctivitis, erosive stomatitis involving the inside of the lower lips and adjacent gum near the commisures and the free portion of the tongue
- Lesions on the hard palate, pharynx and upper third of the oesophagus in severe cases
- Rumen, reticulum and omasum rarely have lesions
- Small streaks of haemorrhages and sometimes erosions: in the first portion of the duodenum and the terminal ileum
- Extensive necrosis and sometimes severe ulceration of Peyer's patches
- Congestion around the ileo-caecal valve, at the caeco-colic junction and in the rectum. 'Zebra stripes' of congestion in the posterior part of the colon
- Small erosions and petechiae on the nasal mucosa, turbinates, larynx and trachea
- Bronchopneumonia is a constant lesion
- Possibility of pleuritis and hydrothorax
- Congestion and enlargement of spleen
- Congestion, enlargement and oedema of most of the lymph nodes
- Erosive vulvovaginitis may exist
Differential diagnosis
- Rinderpest
- Contagious caprine pleuropneumonia
- Bluetongue
- Pasteurellosis
- Contagious ecthyma
- Foot and mouth disease
- Heartwater
- Coccidiosis
- Mineral poisoning
Laboratory diagnosis
Procedures
Identification of the agent
- Antigen detection
- Agar gel immunodiffusion
- Counter immunoelectrophoresis
- Indirect fluorescent antibody test
- ELISA
- Immunohistopathology
- Virus isolation and identification
- In primary lamb kidney cells or VERO cell line
- Virus neutralisation
- Electron microscopy
- Virus RNA detection
- PPR-specific cDNA probes
- Amplification by polymerase chain reaction (PCR)
Serological tests
- Virus neutralisation (prescribed test in the Manual)
- Competitive ELISA
- Counter immunoelectrophoresis
- Agar gel immunodiffusion
- Immunodiffusion inhibition test
Samples
- Swabs of the conjunctival discharges and from the nasal, buccal and rectal mucosae
- Whole blood collected on heparin (blood and anticoagulant should be mixed gently)
- Lymph nodes, especially the mesenteric and bronchial nodes
- Spleen
- Large intestine and lungs
Samples should be transported under refrigeration
PREVENTION AND CONTROL
- No specific treatment
- Antibiotics may prevent secondary pulmonary infections (oxytetracycline, chlortetracycline)
Sanitary prophylaxis
- Recommended when the disease appears in previously PPR-free countries (see rinderpest)
Medical prophylaxis
- Rinderpest vaccine is commonly used
- A homologous PPR vaccine is also available and is preferable, to avoid confusion when retrospective serological surveys are done
- Both vaccines give strong immunity
- Genetically engineered recombinant vaccines are currently undergoing limited field trials
REFERENCES AND OTHER INFORMATION
- Reference experts and laboratories
- Classified as an OIE List A disease (A050)
- Chapter 2.1.5. in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.
- Terrestrial Animal Health Code
- Other references - see the Index
- World Animal Health .
- Current Animal Health Status (Disease Information)
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Contact : scientific.dept@oie.int