Sensitivity and specificity analysis for targeted selective treatment using eye colour chart in sheep flocks naturally infected with Haemonchus contortus

Abstract

An eye color chart for screening the flock for anaemic sheep was developed and is in use since 2008 in organized farms in arid Rajasthan. In present analysis its accuracy (sensitivity and specificity) was analyzed in identifying anaemic sheep (PCV 3001 epg. An inverse relation exists between sensitivity and specificity of the TST system. Based on criteria, the overall sensitivity of TST system ranged from 22.9% (criteria as FEC 3001 epg and PCV 85% during both monsoon season and winter. The overall specificity varied from 20.0 (criteria as FEC >3001 epg and PCV <22) to 81.5% (criteria as FEC <1,000 epg and PCV <18). Thus it appears that in sheep flocks predominantly infected with H. contortus, the application of the TST system as a guidance for the administration of anthelmintic drugs can be an important tool in management of GINs in Rajasthan.

Keywords

• Anaemia
• Eye colour chart
• Haemonchus contortus
• Sensitivity
• Sheep
• Specificity