Appraisal of interpretation criteria for the single intra-dermal comparative cervical tuberculin test for the diagnosis of tuberculosis in dromedary camels in Ethiopia

Abstract

Dromedary camels are the main sources of milk, meat and income for the Ethiopian pastoralists as they withstand the harsh environments of the regions of the country. Tuberculosis (TB) affects dromedary camels causing morbidity and mortality in these animals. Hence, early diagnosis and identification of infected camels play a significant role in reducing the transmission of TB in camels. This study was conducted on 168 camels between October 2014 and July 2015 to evaluate the performance of single intra-dermal comparative cervical tuberculin (SICCT) to diagnose TB in camels. Gross pathology was used as a gold standard to define disease status of each camel. The result showed that at the cutoff value of ≥ 3 mm SICCT had optimum performance with sensitivity and specificity of 60.7 and 85%, respectively. Moreover, at a cutoff ≥ 3 mm, the receiver operating characteristics (ROC) revealed area under the ROC curve was 0.729 (0.615-0.842) which is statistically significant (p = 0.000). Thus, the result of the present study could suggest the use of ≥ 3 mm cutoff value for the diagnosis of TB in dromedary camels in Ethiopia.

Tuberculosis caused by Mycobacterium caprae in a camel (Camelus dromedarius)

“…However, the accurate ante-mortem diagnosis of TB is generally difficult, and few studies reporting the performance of TB diagnostic tests using different interpretation criteria in live OWC are available [ 4 , 13 ]. The use of the comparative intradermal tuberculin (CIT) test rather than a single intradermal tuberculin (SIT) test is usually preferred as a first option for diagnosis owing to the potential interference caused by environmental mycobacteria or Corynebacterium pseudotuberculosis infections [ 8 , 14 ]. In addition, some studies have highlighted the potential diagnostic value of the serological tests, since they have proved to have a higher sensitivity in the case of OWC than tests based on cell-mediated immunity [ 4 , 15 ].…”