Anthelmintic resistance of Haemonchus contortus from sheep flocks in Brazil: concordance of in vivo and in vitro (RESISTA-Test©) methods

Abstract

This study evaluated the resistance status of Haemonchus contortus from sheep flocks in the state of São Paulo, Brazil, through comparison between the fecal egg count reduction test (FECRT) and the larval development test (LDT). For the FECRT, 35 sheep were selected in each of five flocks and divided into groups treated with: benzimidazole, levamisole, ivermectin, monepantel and control. Feces were collected for EPG and fecal cultures. The LDT was performed using thiabendazole (TBZ), levamisole (LEV), ivermectin aglycone (IVM-A) and Zolvix (ZLV). Resistance to all drugs was detected using FECRT in 100% of the flocks, except in relation to ZLV (40% resistant and 20% suspected of resistance). LDT indicated resistance to TBZ and IVM-A in all flocks, to LEV in 80% of flocks and to ZLV in 10%. Total agreement was obtained between the two tests for TBZ and IVM (k = 1.0), while for LEV (k = 0.8) and ZLV (k = 0.9), substantial and almost perfect agreement were obtained, respectively. The concordance between the tests was significant, thus showing that it is possible to use the outcome of the LDT to predict the FECRT, and hence validating the former as a fast diagnostic test for use by sheep farmers in Brazil.

Investigating the Benefits of Target Selective Treatment by Average Daily Weight Gain Against Gastrointestinal Nematodes in Morada Nova Lambs

“…In the dry season, however, while RESISTA-Test © and molecular test were concordant (RT > CT > TST), the FECRT was not so aligned (RT > TST > CT). In a study conducted in Brazilian ocks with a historical use of levamisole, the resistance detected was aligned in both FECRT and RESISTA-Test © (Gainza et al 2021).…”

Parasitofauna and current status of anthelmintic resistance in Latvian sheep farms

“…To determine the parasitofauna on the farms, we examined the coprological samples of sheep according to the methods of McMaster and Baermann [13].…”

“…On small farms, 10% of the sheep from the total herd were included in this study, while it was up to 20% from medium and large farms. All animals underwent a coprological examination before the start of the study, and to obtain statistically relevant data, only sheep diagnosed with more than 200 McMaster eggs per gram of feces (EPGs) were included in the study [13].…”

“…Recently, publications have appeared where FECRT is combined with molecular testing methods. Some authors also suggest combining molecular methods with FECRT [8,13,14].…”