VALUE OF POOLED GASTRO-INTESTINAL NEMATODE COPROANTIGENS IN THE DIAGNOSIS OF INHIBITED LARVAE INFECTION IN EGYPTIAN SHEEP

Abstract

Parasitic gastroenteritis (PGE) infecting sheep in acute or chronic forms causes severe economic losses. Infections by adult worms can be easily diagnosed and controlled, but infection by migrating and inhibited larvae are difficult to diagnose. Detection of anti-parasite antibodies in sera of infected animals needs special Ag for each species and presence of antibodies in sera does not reflect the actual infection. This study evaluated diagnostic efficacy of two pooled Copro Ag(s) prepared from feces of PGE infected sheep with larval5 species (Haemonchus spp., Trichostrongylus spp., Nematodirus spp., Cooperia spp. & Ostertagia spp.) in sheep. Diagnostic values of pooled Ag(s) were compared with two separate worm Ag(s) (Haemonchus spp. & Trichostrongylus spp.) using indirect and antigen capture ELISA. The results showed high sensitivity for pooled Copro and larval Ag(s) than individual parasitic Ag(s) in detecting Ab(s) in infected animals. Copro Ag showed high sensitivity (87.69%) than larval Ag (75.38%). For Haemonchus and Trichostrongylus Ag was 44.62% & 32.31% respectively. Pooled larval antigen showed high specificity (86.66%) than Copro Ag (78.33%), without cross reaction with non-infected controls. In migrating and inhibited larvae, pooled Ag showed 80% sensitivity in detecting PGE circulating antigen in animals without eggs in feces compared to 30% sensitivity using pooled Copro antigen by sandwich ELISA. Positive animals shed eggs in feces during follow up prior to parturition. Diagnosis of inhibited larvae circulatingAg(s) using pooled larval antigen was promising method in expecting time of autoinfection of sheep due to activation of arrested larvae within the bodies. This facilitated their therapeutic treatment at a critical time before the sudden re-appearance of infection.