An Overview of Anthelmintic Resistance in Domestic Ruminants in Brazil

Macedo, Lucia Oliveira; Silva, Samuel Souza; Alves, Leucio Câmara; Carvalho, Gílcia Aparecida; Ramos, Rafael Antonio Nascimento

doi:10.3390/ruminants3030020

Cited by 4 publications

(2 citation statements)

References 138 publications

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“…These findings on the occurrence of ivermectin resistance in goats in South Darfur corroborate reports from many regions of the world, and H. contortus is involved in most regions. In South America, the status of ivermectin resistance is critical, particularly in Brazil [48, 49]. Remarkably, in Europe occurrence of ivermectin resistance in goats has been described from regions such as Czech Republic, Germany, Romania and United Kingdom [12, 50–52].…”

Section: Discussionmentioning

confidence: 99%

First evaluation and detection of ivermectin resistance in gastrointestinal nematodes of sheep and goats in South Darfur, Sudan

Mohammedsalih,

Ibrahim,

Juma

et al. 2024

Preprint

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In Sudan, resistance to benzimidazoles has been reported recently in cattle and goats from South Darfur. Herein, ivermectin efficacy against gastrointestinal nematodes (GINs) was evaluated in sheep and goats in three study areas in South Darfur. The faecal egg count reduction test (FECRT) was used to evaluate the efficacy of ivermectin in sheep and goats naturally infected with GINs in the region of Bulbul (goats: n=106), Kass (goats: n=40) and Nyala (Domaia (sheep: n=47, goats: n=77) and the University farm (goats: n=52)), using different treatment plans, and the efficacy was evaluated 12 days after treatment. Ivermectin efficacy was also evaluated in goats experimentally infected using local Haemonchus contortus isolates from Kass and Nyala. Nematodes surviving ivermectin treatment in goats in Bulbul and Nyala were harvested and larvae used to infect worm-free male sheep (n=6, ≤ 6 months old). Infected sheep were dosed subcutaneously with ivermectin every eight days with increasing doses from 0.2 mg/kg to 1.6 mg/kg bodyweight (bw). Reduced ivermectin efficacy was identified in sheep and goats in the four study locations. Using a paired statistic, the efficacy of a therapeutic dose in sheep was 75.6% (90% upper credible limit (UCrL): 77.5%), while twice the recommended dose led to a reduction of 92.6% (90% UCrL: 93.3%). In goats, the FECRs of a therapeutic dose were 72.9 – 95.3% (90% UCrL range: 73.6 – 95.7%) in Bulbul, Nyala Domaia, Nyala University farm and Kass. Twice the dose recommended for goats in Bulbul revealed a 90% UCrL of 87.6%. All post-treatment faecal cultures contained only Haemonchus spp. larvae. The experimental infection trials in sheep and goats supported our findings from field trials and calculated upper 90% CrL of below 98.9%. For the first time highly ivermectin resistant H. contortus populations have been identified in sheep and goats in Sudan, and resistance was experimentally confirmed.

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Section: Discussionmentioning

confidence: 99%

First evaluation and detection of ivermectin resistance in gastrointestinal nematodes of sheep and goats in South Darfur, Sudan

Mohammedsalih,

Ibrahim,

Juma

et al. 2024

Preprint

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“…contortus is involved in most regions. In South America, the status of ivermectin resistance is critical, particularly in Brazil [ 50 , 51 ]. Remarkably, in Europe occurrence of ivermectin resistance in goats has been described from regions such as Czech Republic, Germany, Romania and United Kingdom [ 13 , 52 – 54 ].…”

Section: Discussionmentioning

confidence: 99%

First evaluation and detection of ivermectin resistance in gastrointestinal nematodes of sheep and goats in South Darfur, Sudan

Mohammedsalih,

Ibrahim,

Juma

et al. 2024

PLoS ONE

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In Sudan, resistance to benzimidazoles has been reported recently in cattle and goats from South Darfur. Herein, ivermectin efficacy against gastrointestinal nematodes (GINs) was evaluated in sheep and goats in three study areas in South Darfur. The faecal egg count reduction test (FECRT) was used to evaluate the efficacy of ivermectin in sheep and goats naturally infected with GINs in the region of Bulbul (goats: n = 106), Kass (goats: n = 40) and Nyala (Domaia (sheep: n = 47, goats: n = 77) and the University farm (goats: n = 52)), using different treatment plans, and the efficacy was evaluated 12 days after treatment. Ivermectin efficacy was also evaluated in goats experimentally infected using local Haemonchus contortus isolates from Kass and Nyala. Nematodes surviving ivermectin treatment in goats in Bulbul and Nyala were harvested and larvae used to infect worm-free male sheep (n = 6, ≤6 months old). Infected sheep were dosed subcutaneously with ivermectin every eight days with increasing doses from 0.2 mg/kg to 1.6 mg/kg bodyweight (bw). Reduced ivermectin efficacy was identified in sheep and goats in the four study locations. Using a paired statistic, the efficacy of a therapeutic dose in sheep was 75.6% (90% upper credible limit (UCrL): 77.5%), while twice the recommended dose led to a reduction of 92.6% (90% UCrL: 93.3%). In goats, the FECRs of a therapeutic dose were 72.9–95.3% (90% UCrL range: 73.6–95.7%) in Bulbul, Nyala Domaia, Nyala University farm and Kass. Twice the dose recommended for goats in Bulbul revealed a 90% UCrL of 87.6%. All post-treatment faecal cultures contained only Haemonchus spp. larvae. The experimental infection trials in sheep and goats supported our findings from field trials and calculated upper 90% CrL of below 98.9%. For the first time highly ivermectin resistant H. contortus populations have been identified in sheep and goats in Sudan, and resistance was experimentally confirmed.

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