Phenotypic and genotypic characterisation of Haemonchus spp. and other gastrointestinal nematodes resistant to benzimidazole in infected calves from the tropical regions of Campeche State, Mexico

Anthelmintic resistance (AR) in sheep raised under mountain farming conditions in South Tyrol (Northern Italy) was assessed on eight farms (n=99 animals). A faecal egg count reduction (FECR) test was...

Detection of benzimidazole resistance in gastrointestinal nematodes of sheep and goats of sub-Himalyan region of northern India using different tests

Corrigendum to “Status of benzimidazole resistance in Haemonchus contortus of goats from different geographic regions of Uttar Pradesh, India” [Vet. Parasitol. 208 (2015) 263–267

Production of beef cattle is one of the most important economic activities in Mexico. However, anthelmintic resistance (AR) has affected animal productivity. The aim of this study was to determine the presence of AR in gastrointestinal nematodes (GIN) of beef cattle in Candelaria Municipality of Campeche State, Mexico. Sixty-five-month-old beef calves were selected for the faecal egg count reduction test (FECRT) and the inhibition of egg hatch (IEH) assay. These parameters were determined using albendazole (benzimidazole, BZ), ivermectin (IVM, Macrocyclic lactone, ML) and levamisole (LEV, imidazothiazole, IMZ). Allele-specific PCR (AS-PCR) confirmed polymorphisms at codon 200 of isotype 1 of the β-tubulin gene of Haemonchus placei. The results showed 32% IVM toxicity by FECRT, indicating problems of AR in the GIN population. In contrast, BZ and LEV showed 95 and 100% toxicity, respectively, against GIN from infected beef calves. The infective larvae (L3) of Cooperia, Haemonchus and Oesophagostomum were identified before anthelmintic treatment, and Cooperia L3 larvae were identified after treatment with IVM. The IEH assays had lethal dose 50 (LD50) of 187nM to BZ, confirming the ovicidal effect of BZ. In contrast, the LD50 for LEV and IVM were 3.3 and 0.4mM, respectively. The results obtained by AS-PCR confirmed two DNA fragments of 250 and 550bp, corresponding to the resistant and susceptible alleles in the H. placei population. The nematode Cooperia showed AR against IVM, while the toxicity effect of BZ against GIN with both FECRT and IEH was confirmed.

ABSTRACTBackground and Aim:Gastrointestinal nematodes (GINs) such as Haemonchus contortus and Trichostrongylus colubriformis are major health threats in goats, exacerbated by growing anthelmintic resistance (AR). Despite the widespread use of albendazole and ivermectin in Nakhon Si Thammarat, Southern Thailand, data on AR status in goats remain scarce. This study aimed to evaluate the resistance of GINs to albendazole and ivermectin using fecal egg count reduction (FECR) tests and to determine benzimidazole (BZ) resistance through molecular detection of the F200Y mutation in the β-tubulin isotype 1 gene.Materials and Methods:A total of 192 meat goats from six farms were randomly divided into four groups: untreated control, albendazole-treated, ivermectin-treated, and combination-treated. FECR was assessed on day 14 post-treatment. Larval cultures and semi-nested polymerase chain reaction (PCR) were used to identify nematode genera. BZ resistance was determined through allele-specific PCR on H. contortus and T. colubriformis third-stage larvae, pre- and post-albendazole treatment.Results:FECR revealed confirmed resistance (FECR < 95%) to albendazole (−35.48%–62.5%), ivermectin (−2.41%–51.47%), and their combination (−25%–48.36%) across all farms. Haemonchus and Trichostrongylus were the predominant genera post-treatment. Molecular analysis showed high pre-treatment frequencies of the F200Y resistance allele in H. contortus (75.0%–80.6%) and T. colubriformis (88.6%–100%), which reached 100% post-treatment. Susceptible genotypes were entirely eliminated following albendazole treatment.Conclusion:This is the first comprehensive study confirming widespread AR to albendazole and ivermectin in meat goats in southern Thailand. The fixation of the BZ resistance allele in both nematode species highlights the urgency for revising current deworming practices. Immediate adoption of integrated parasite management strategies, including drug rotation, targeted selective treatment, and exploration of alternative anthelmintics, is critical to mitigate economic losses and protect public health.

Comparative use of faecal egg count reduction test, egg hatch assay and beta-tubulin codon 200 genotyping in small strongyles (cyathostominae) before and after benzimidazole treatment

Anthelmintic resistance in hair sheep farms in a sub-humid tropical climate, in the Huasteca Potosina, Mexico.

Multiple anthelmintic resistance in gastrointestinal nematodes of small ruminants in Bangladesh

Efficacy of fenbendazole against gastrointestinal nematodes in naturally infected goats in Maputo Province, Mozambique using in vivo, in vitro and molecular assessment.

Status of benzimidazole resistance in Haemonchus contortus of goats from different geographic regions of Uttar Pradesh, India

First report of Benzimidazole resistance in equid intestinal strongyles from Kashmir valley, India.

The relationship between faecal egg count reduction and the lethal dose 50% in the egg hatch assay and larval development assay

BackgroundThis study aimed to evaluate the efficacy of anthelmintics in goats raised under mountain farming conditions in northern Italy. On 8 goat farms (n = 143 animals), a faecal egg count reduction (FECR) test was done after farmers conducted their routine anthelmintic treatments. Furthermore, on 5 goat farms (n = 135 animals) a FECR test was done under controlled conditions applying oral formulations of a macrocyclic lactone (ML), benzimidazole (BZ) (partly in combination with salicylanilide (SA)) or a combination of imidazothiazole (IT) and SA on the same farm. AR was assumed if FECR and the upper confidence interval (CI) was < 95% and the lower 95% CI was < 90%.ResultsUnderdosing was found in 6 of the 8 farms tested after routine treatments. Out of the 6 routinely ML-treated goat flocks, only three were found where ML showed adequate efficacy. FECR in all others ranged between 64 and 93%. In one flock Trichostrongylus spp. and in one Haemonchus spp. larvae were identified after treatment. BZ-treated flocks had an efficacy of 99 and 37%. Larvae identified after treatment were Trichostrongylus spp. in one and Haemonchus spp. in the other flock. Under controlled conditions, ML had an adequate efficacy on 4 farms and a FECR of 88% on another one. BZ was effective on all farms. The combination of BZ and SA had a FECR of 99% on the farm it was tested. IT + SA in combination was effective on 2 farms and had a FECR of 91% on a third farm. Larvae identified after treatment were composed of Haemonchus spp. (ML and BZ), Trichostrongylus spp. (BZ) and Teladorsagia spp. (BZ and SA).ConclusionsThis first report on the prevalence of AR in goats in the mountainous region of South Tyrol reveals a low efficacy of the most commonly used anthelmintics after routine treatments. This might be explained by a high level of underdosing as observed in the farms. However, results from the controlled FECR tests suggest that the observed level of AR was lower but cannot be solely explained by underdosing.

The detection of anthelmintic resistance in nematodes of veterinary importance

The aim of this study was to evaluate the aqueous and ethanolic leaf extracts of Vitex negundo for their anthelmintic potential against the benzimidazole-resistant Haemonchus contortus of sheep. The organized sheep farms in the various districts of Tamil Nadu viz., Thiruvallur, Kancheepuram, Salem, Karur and Kanniyakumari were randomly selected for sampling. 560 faecal samples were collected from organized sheep farms from the above districts before and after deworming with benzimidazole (BZ). The faecal egg count reduction test (FECRT) revealed the development of anthelmintic resistance to BZ in Thiruvallur and Kancheepuram districts. The allele-specific polymerase chain reaction (AS-PCR), the molecular technique employed to amplify the 250bp BZ-resistant gene fragments, had also revealed the BZ resistance. This study evaluated the anthelmintic potential of Vitex negundo leaves against BZ-resistant H. contortus in sheep. The aqueous leaf extracts (ALE) and ethanolic leaf extracts (ELE) of V. negundo were prepared in various concentrations, viz., 5, 10, 20, and 50 mg/mL. The in vitro methods viz., egg hatch assay (EHA) and larval paralysis assay (LPA) were performed to assess the anthelmintic efficacy of the above extracts. EHA revealed maximum efficacy (%) of 11.67±1.67% and 5.00±0.91% in 50 mg/mL concentration of ALE and ELE, respectively. LPA revealed 13.44±1.41% and 7.23±0.55% efficacy in 50 mg/mL concentrations of ALE and ELE, respectively. The results of this study with V. negundo indicated a dose-dependent effect of ALE and ELE in EHA and LPA. It is concluded that V. negundo could be a futuristic phytomedicine for an alternate control strategy to combat the anthelmintic resistance against BZ-resistant strongyle nematodes of sheep.