Duration of Anthelmintic Effect of Three Formulations of Ivermectin (Oral, Injectable and Pour-on) Against Multiple Anthelmintic-Resistant Haemonchus contortus in Sheep

Abstract

We report the results of investigations that were conducted in a sheep flock in Uttaranchal, India where repeated failure of anthelmintic medication was noted. The study revealed that Haemonchus contortus in sheep had developed resistance to benzimidazoles (fenbendazole, mebendazole and albendazole), imidazothiazole (levamisole) and salicylanide (rafoxanide), while it was fully susceptible to avermectins (ivermectin). Further, the suppression of nematode egg output in faeces of sheep naturally infected with multiple anthelmintic-resistant H. contortus following treatment with ivermectin tablet (0.4 mg/kg body weight (bw), orally), ivermectin injection (1% w/v, 0.2 mg/kg bw, subcutaneously) and ivermectin pour-on (0.5 w/v, 0.5 mg/kg bw) was also studied over a period of 10 weeks post treatment. It was noted that ivermectin tablet after initial clearance of infection (faecal egg count reduction 100%), could not prevent establishment of new patent natural infection for even a single day, while ivermectin pour-on and injection prevented the establishment of new infection for 7 and 14 days post treatment, respectively. Maximum protection period (duration for which mean faecal egg count of sheep reaches 500 eggs per gram of faeces or more) of 68 days was recorded in sheep treated with injectable ivermectin, followed by pour-on (60 days) and oral (53 days) preparations.

Genotyping of benzimidazole susceptible and resistant alleles in different populations of Haemonchus contortus from Himalayan and sub-Himalayan regions of North-West India

“…High allelic frequency of resistance (r) in adult worms collected from extensively managed sheep and in larvae from intensively managed sheep at Pantnagar, as revealed in the present study (Tables 1 and 2), correlates with our earlier findings at the same place where we tested 3 benzimidazole drugs i.e., fenbendazole, mebendazole and albendazole, and found their efficacies to be 52.3%, 37.3% and 72.3%, respectively using FECRT (Garg et al 2007). The high prevalence of resistant alleles in and around Pantnagar may be attributed to frequent and indiscriminate use of benzimidazole anthelmintics in the area which may have resulted in development of resistance.…”

Emergence of Anthelmintic Resistance in Haemonchus contortus on Organized Sheep and Goat Farms of Sub-Himalayan Region of Northern India

“…Similar observation has also been reported by Uppal et al, (1992), Laha et al, (1999) and Garg et al, (2007). However, Makvana andSingh (2009) andJaiswal et al, (2013) observed ivermectin resistant gastrointestinal nematodes in sheep and goats, respectively from Gujrat and Uttar Pradesh, India, respectively.…”

“…The prevalence of FBZ and TMS resistance might be due to frequent use of same anthelmintic for a long period (Maingi et al, 1996). In India, this type of resistant H. contortus associated with frequent use of different anthelmintics has also been reported by Uppal et al, (1992), Yadav and Uppal (1993) and Garg et al, (2007).…”

“…In India, the first report of anthelmintic resistance in H. contortus to phenothiazine and thiabendazole has been reported by Varshney and Singh (1976) (Yadav, 1990;Laha et al, 1999;Garg et al, 2007;Jaiswal et al, 2013;Rialch et al, 2013;Pandey and Vatsya, 2013). However, there is scanty information on the prevalence of anthelmintic resistance from organized sheep and goat farms of sub-Himalayan region of northern India.…”

Comparison of Two Pour-On Formulations of Ivermectin against Gastrointestinal Worms, Fleas and Lice in Naturally Infected Stray Dogs

“…However, even though investigations with ivermectins on internal and external parasites in ruminants and horses are widely documented [18]- [22], the research on the efficacy of pour-on ivermectin formulations in dogs is somewhat scarce [3]- [23]. In Mexico, where disease-carrying IP, fleas and lice in dogs are abundant, no controlled test on the impact of pour-on ivermectin has been carried out, either on the weight differences of treated animals or on the specific identification of the parasites present before and after treatment of the dogs.…”