Systematic Veterinary Virology

Peste des petits ruminants (PPR)

PESTE DES PETITIS RUMINANTS (PPR)

Field diagnosis

• In the field, a presumptive diagnosis is made on the basis of clinical, pathological, and epizootiological findings.

Clinical materials to be collected

• Tears - Cotton buds or swabs of absorbent cotton wool are inserted into the conjunctival sac and swirled around to collect tears. The bud/swab is broken off into a container and about 150 microlitres of sterile phosphate-buffered saline (PBS pH 7.2 to 7.6)
• Gum debris - This material can be collected by a spatula or finger rubbed across the gum and inside the upper and lower lips. The material collected is then scraped into a container and 150 microlitres of PBS are added
• Tissues – Tissue to be collected are from lymph nodes found around the lungs (mediastinal) and alimentary tract (mesenteric); portions of the spleen and the lungs. Two sets of each tissue are required; one set is chilled but not frozen, and the other is put in 10 percent formalin solution to preserve the samples
• Unclotted blood - This is needed for virus isolation and should be collected in bottles containing anticoagulants (heparin or ethylenediaminetetracetic acid [EDTA]).
• Clotted blood or serum – For identification of antiboies

Isolation and identification

• The tissue culture used are lamb kidney cells and Vero cells. The characteristic CPE appear around 5^th day and are cell rounding and aggregation and syncytia formation
• Identification of virus
• Immunocapture enzyme-linked immunosorbent assay (Sandwich ELISA)
• Counterimmunoelectrophoresis (CIEP): Most rapid test for detecting viral antigen
• Agar gel immunodiffusion (AGID): Very simple and inexpensive and gives results within 1 day, but not sensitive to mild forms of PPR
• Immunofluorescence and immunoperoxidase
• Polymerase chain reaction (RT-PCR)
• Nucleic acid probes

Serology

• Competitive ELISA
• Virus neutralization test (Prescribed test for international trade)

Differential diagnosis

Rinderpest	Clinically, RP and PPR are similar, but the former should be the prime suspect if the disease involves both cattle and small ruminants.
Pasteurellosis	Enzootic pneumonia or the septicemic form of pasteurellosis is characterized by obvious respiratory signs, infrequent diarrhea, and a fatality rate rarely exceeding 10 percent
Contagious caprinepleuropneumonia	There is no digestive system involvement, and the clinical signs and lesions are confined to the respiratory system and pericardium.
Bluetongue	Swelling of the lips, muzzle, and oral mucosa, together with edema of the head region, helps to differentiate bluetongue from PPR. Coronitis, common in bluetongue, is not a feature of PPR. Also, sheep are more affected than goats.
Heartwater	There is often central nervous system involvement, including convulsions. There is no diarrhea.
Contagious ecthyma (contagious pustular dermatitis, orf)	The orf virus causes proliferative, not necrotic lesions, that involve the lips rather than the whole oral cavity. The absence of nasal discharges and diarrhea also distinguish orf from PPR.
Foot-and-mouth disease	This condition is comparatively mild, and the most characteristic clinical sign, lameness, is not a feature of PPR
Nairobi sheep disease	Sheep are more severely affected than goats
Coccidiosis	There is no upper digestive tract and respiratory system involvement.
Plant or mineral poisoning.	Several plants and minerals may cause severe intestinal lesions. Case history and absence of fever should distinguish poisoning from PPR.