Epidemiology of strongyle nematode infections and first report of benzimidazole resistance in Haemonchus contortus in goats in South Darfur State, Sudan

Abstract

Background Since pastoralists in South Darfur, Sudan, had complained about lack of albendazole (ABZ) efficacy to control nematodes in goats, the frequency of infection with gastrointestinal helminths was studied before in vivo faecal egg count reduction tests (FECRT) were conducted using ABZ orally either at the dose recommended for sheep, 5 mg/kg body weight (bw) or at 10 mg/kg bw. Experiments included goats naturally infected with gastrointestinal nematodes or experimentally infected with local Haemonchus contortus isolates. Three study areas (Nyala, Beleil and Kass) were visited in autumn or winter. Results Out of 478 screened goats, 82.4% were infected with gastrointestinal helminths and 82% were shedding eggs of strongyle nematodes with 90% of the strongyle larvae representing Haemonchus spp. A FECRT using naturally infected goats ( n = 225: 71 untreated, 104 and 50 treated with 5 and 10 mg ABZ/kg bw, respectively) detected reduced ABZ efficacy in Nyala and Kass. Paired and unpaired FECRT calculations detected reductions of 72–92% with samples taken at 8 days post treatment with 5 mg ABZ/kg bw and of 85–94% with 10 mg ABZ/kg bw. The FECRT based on day 14 post treatment samples showed reductions of 69–77% with 5 mg/kg and of 75–87% with 10 mg ABZ/kg bw. In Beleil, ABZ efficacy was 95%. In the egg hatch test EC 50 values for Nyala and Kass ranged from 0.12–0.24 μg thiabendazole/ml, corresponding to benzimidazole resistant phenotypes. Only Haemonchus spp. larvae were present after treatments in coprocultures. When the efficacy was evaluated experimentally using isolates of H. contortus from Nyala and Kass, the 5 mg ABZ/kg dose revealed reductions of 76–78% on day 8 and of 62–70% on day 14 with the unpaired method. Using 10 mg ABZ/kg, the FECR was still only 77–82%. Conclusions Both, in vivo and in vitro methods detected resistant H. contortus populations in goats from South Darfur State. The time point 14 days post treatment was more sensitive for detection of ABZ resistance than 8 days post treatment. This is the first report on the occurrence of anthelmintic resistance in Sudan confirming that anthelmintic resistance selection is occurring in African subsistence farming systems. Electronic supplementary material The online version of this article (10.1186/s12917-019-1937-2) contains supplementary material, which is available to authorized users.

New codon 198 β-tubulin polymorphisms in highly benzimidazole resistant Haemonchus contortus from goats in three different states in Sudan

“…Phenotypically BZ resistant H. contortus populations (FECRT: 75-87%; EHT: 0.12-0.24 µg/ml thiabendazole) were very recently reported for the first time in goats in Sudan from the State South Darfur [34]. The present study aimed to identify additional BZ resistant populations and to understand the mechanisms of BZ resistance, through detecting the changes in isotype 1 β tubulin sequences, in three different Darfur States of Sudan.…”

“…In South Darfur, BZ resistance in goats (Capra hircus) was evaluated using both phenotypic, FECRT and EHT, and molecular techniques, while in East and Central Darfur, the resistance was only studied at the molecular level using samples from abattoirs. Since phenotypic BZ resistance was recently reported in goats from Kass and Nyala [34], samples from these areas collected during the previously reported field trials (June 2015-December 2016) were used here and studied at the molecular level. No previous data were available for the other areas.…”

“…A total of 328 goats of both sexes and in different age groups that had not received any anthelmintic treatment for at least one month were selected for collection of faecal samples to be tested for the presence of GIN infections. Twenty-nine farms [Rehed Al-Birdi (n = 15) and Tulus (n = 14)] with at least five animals per farm [34] were screened. Before sampling, the age (grouped into young (< than 1 year-old) and adults (≥ 1 year-old), based on dentition [37]) and the sex of the goats were determined.…”

“…Goats positive for infection with strongyle nematodes were classified into groups of egg shedding intensity: low (< 500 eggs per gram (epg) faeces); moderate (500-2000 epg); or high (> 2000 epg) intensity [38]. Accordingly, 127 moderate to highly infected goats [Rehed Al-Birdi (n = 77) and Tulus (n = 50)] of both sexes and age groups were selected for a FECRT and grouped into control and treated groups using the same strategy as recently described [34]. Two commercial albendazole brands were used [Endospec 2.5% (batch No: XMF031A; Bimeda, Llangefni, Wales); and Albex ® 10% w/v oral suspension (batch No.…”

“…Since the 5 mg/kg body weight (bw) (ovine dose) is still prescribed on the package labels of different albendazole commercial brands in Sudan to be used in the treatment of GIN infected goats, and the farmers in South Darfur usually retreat their animals with the same anthelmintic at the same dose again after 14 days [34], here different treatment strategies were adopted and dosages to obtain information regarding (i) the BZ resistance status by administering the appropriate dose of albendazole for goats (10 mg/kg bw) [41]; (ii) the efficacy of the 5 mg/kg bw recommended on the label of the drugs in Sudan; (iii) the differences in efficacy of albendazole at doses of 5, 7.5, 10 and 12.5 mg/kg bw to remove some economically important GINs of goats based on genus-specific PCR; (iv) the variants in allele frequencies at the three codon positions associated with BZ resistance when the 5 mg/kg albendazole dose recommended for goats in Sudan was compared to 7.5, 10 and 12.5 mg/kg bw; and (v) to measure the effects of repeated treatments with 5 mg/kg bw as frequently used by local farmers on frequencies of resistance alleles.…”