Efficacy of a single high oxfendazole dose against gastrointestinal nematodes in naturally infected pigs

Abstract

The goal of the current experiment was to assess the clinical efficacy of oxfendazole (OFZ) administered as a single oral dose (30 mg/kg) to pigs naturally parasitized with Ascaris suum, Oesophagostomum spp., Metastrongylus spp. and Trichuris suis. Thirty-six local ecotype piglets were divided into three independent experiments, named I, II and III (n = 12 each), respectively. Each experiment involved two different groups (n = 6): Untreated Control and OFZ treated. Animals were naturally parasitized with A. suum (Experiments I, II and III), Oesophagostomum spp. (Experiments I and II), T. suis (Experiments II and III) and Metastrongylus spp. (Experiment I). Pigs in the treated group received OFZ (Synanthic^®, Merial Ltd., 9.06% suspension) orally at 30 mg/kg dose. At five (5) days post-treatment, animals were sacrificed and the clinical efficacy of the OFZ treatment was established following the currently available WAAVP guidelines for a controlled efficacy test. None of the animals involved in this experiment showed any adverse events during the study. OFZ treatment given as a single 30 mg/kg oral dose showed a 100% efficacy against all the nematode parasites present in the three experiments. In conclusion, under the current experimental conditions, OFZ orally administered to naturally parasitized piglets at a single dose of 30 mg/kg was safe and highly efficacious (100%) against adult stages of A. suum, Oesophagostomum spp., T. suis and Metastrongylus spp.

Introduction

Oxfendazole (OFZ), a benzimidazole (BZD) methyl-carbamate compound, has demonstrated activity against Taenia solium cysticercus in pigs after its single oral administration at 30 mg/kg (Gonzalez et al., 1996). OFZ treatment of T. solium-infected pigs has been proposed as a tool to interrupt the transmission cycle of this parasite, protecting people from neurocysticercosis, the most common parasitic infection of the human nervous system and the most frequent preventable cause of epilepsy in the developing world and endemic in many countries of Latin America, Africa and Asia (Gonzalez et al., 1996). The WHO estimated that globally, the parasite is estimated to cause 50 million human cases of taeniasis (infection with adult tapeworms) and cysticercosis, and 50,000 human deaths a year in Africa, Asia and Latin America (WHO, 2012).

Even if OFZ has proven efficacious against cysticercosis, many of the poorest livestock keepers whose pigs are affected are not aware of the problem, and hence reluctant to treat the pigs. The objective of this project was to demonstrate the efficacy against other parasites relevant in rural settings for pigs, making the use of OFZ more attractive to the poorest livestock keepers. OFZ was first marketed to be used in cattle, sheep and horses. An oral single dose is recommended in those species for the removal and control of tapeworms (heads and segments), abomasal and intestinal nematodes (adults and 4th stage larvae) and lungworms (adults and larval stages; Lanusse et al., 2009). Additionally, the anthelmintic activity of OFZ against Trichuris vulpis in dogs has been assessed (Dorchies and Arnaud, 1995), after its oral administration at a dose of 11.3 mg/kg/day for three consecutive days. However, OFZ has not been approved for use in pigs. Helminth parasite infections occur frequently in domestic pigs in different production systems worldwide (Roepstorff et al., 2011). The major helminth species include Ascaris suum, Trichuris suis and Oesophagostomum spp. (Roepstorff et al., 2011). A high prevalence of helminth infections has been found in organic pig farms (Carstensen et al., 2002). Despite the common subclinical course of infections, pigs infected with one or more of the above mentioned nematode species have shown reduced food utilisation and growth rates (Hale and Stewart, 1979, Hale et al., 1981, Hale et al., 1985).

Flubendazole (FLBZ; Bradley et al., 1983, Vanparijs et al., 1988), oxibendazole (OBZ; Muirhead and Alexander, 1997, Taylor, 2006) and fenbendazole (FBZ) (Corwin et al., 1984, Marchiondo and Szanto, 1987, Praslicka et al., 1997) are among the methyl-carbamate BZD compounds known to be effective in pigs. However, anthelmintic treatments in pigs with those drugs are commonly performed by mixing the drug into feed for 3 to 10 days. The potential of OFZ for use at the 30 mg/kg dose rate against helminth parasites in pigs should be investigated to prove a broader therapeutic indication for this anthelmintic compound when used at a single dose as indicated for the treatment of porcine cysticercosis. The goal of the current work was to assess the clinical efficacy of a 9.06% OFZ suspension administered as a single oral dose (30 mg/kg) in pigs naturally parasitized with A. suum, Oesophagostomum spp., T. suis and Metastrongylus spp.