Oestrosis: Parasitism by Oestrus ovis

Efficacy of eprinomectin 5 mg/mL topical solution administered pour on at 1 mg per kg body weight against Oestrus ovis myiasis in sheep and goats

The larvae of the nasal bot, Oestrus ovis, mainly parasitize sheep and goats and some species of wild Caprinae but other mammals and humans are also vulnerable to infestation. Eprinomectin 5 mg/mL topical solution (EPRINEX® Multi, Boehringer Ingelheim) administered at 1 mg eprinomectin per kg body weight pour on was recently authorized as an anthelmintic for sheep and goats with zero hours milk withdrawal in several countries in Europe. As the product in cattle has claims against a broad range of parasites including insect parasites and activity against O. ovis has previously been reported following extra-label use in sheep, its therapeutic efficacy against ovine and caprine O. ovis myiasis was evaluated in three regulatory compliant, masked clinical studies. Pre-study recovery of O. ovis larvae from five or six of six randomly selected animals per study site (Bulgaria, one site, sheep; Greece, two sites, sheep or goats) supported the inclusion of the animals from those sites into the studies. The study animals (34 animals per study) were ranked based on bodyweight and allocated randomly to remain untreated (control) or to be treated with eprinomectin 5 mg/mL topical solution at 1 mL per 5 kg body weight pour on. Treatment efficacy was determined based on O. ovis larval counts of eprinomectin 5 mg/mL topical solution-treated vs. untreated animals three weeks after treatment administration. Live O. ovis larvae, including all three instars in each study, were recovered from 13 or 16 of the 17 control animals in the sheep studies (range, 1 to 14 or 5 to 18 larvae, respectively) and from all 17 controls in the goat study (range, 7 to 18 larvae). In each study, eprinomectin 5 mg/mL topical solution-treated animals had significantly (p < 0.001) fewer live O. ovis larvae than the controls. Efficacy of the treatment was 100% and 91.3% against the combined parasitic O. ovis larval stages in sheep and in goats, respectively. The treatment was well accepted by all animals and no health problems were observed throughout the studies. The results of these studies demonstrated eprinomectin 5 mg/mL topical solution administered pour on at 1 mL per 5 kg body weight to be an efficacious and safe treatment of ovine and caprine oestrosis.

Prevalence of Oestrus ovis in small ruminants from the eastern Iberian Peninsula. A long-term study

Oestrus ovis is an obligate parasite that causes myiasis in domestic ruminants, being commonly found in the Mediterranean area. From 2009 to 2019 a total of 3476 heads of culling sheep and goats from the Mediterranean coast of Spain were examined for the presence of O. ovis. The total prevalence was 56.3%, significantly higher in sheep than in goats (61.2% and 43%, respectively). Differences were found in the mean annual prevalence, with the highest value being registered in 2018 (61.7%) and the lowest in 2012 (50.3%). Autumn, for sheep, and winter, for goats, were the seasons with the highest number of infested specimens. Temperature, but not rainfall, was found to be associated with prevalence (p < 0.05). Most L1 were found in the anatomic region I (septum, meatus, and ventral conchae), while L2 and L3 were mainly located in regions II (nasopharynx, ethmoid labyrinth, and dorsal conchae), and III (sinuses). The overall intensity was 12.8 larvae per head, significantly higher in sheep (13.3) than in goats (3.5). Our results confirm the high prevalence of O. ovis in sheep and goats in this geographic area over the last decade, with the trend increasing in recent years in association with higher mean temperatures.