Inactivation of encysted muscle larvae of Trichinella spiralis in pigs using Mebendazole

Authors: FREDERICKS, JORRELL - Former ARS Employee; HILL, DOLORES - Retired ARS Employee; ZARLENGA, DANTE - Retired ARS Employee; Fournet, Valsin; HAWKINS-COOPER, DIANE - Retired ARS Employee; URBAN, JOSEPH - Retired ARS Employee; Kramer, Matthew

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2024
Publication Date: 1/26/2024
Citation: Fredericks, J., Hill, D.E., Zarlenga, D.S., Fournet, V.M., Hawkins-Cooper, D.S., Urban, J.F., Kramer, M.H. 2024. Inactivation of encysted muscle larvae of Trichinella spiralis in pigs using Mebendazole. Veterinary Parasitology. 327: Article e110140. https://doi.org/10.1016/j.vetpar.2024.110140.
DOI: https://doi.org/10.1016/j.vetpar.2024.110140

Interpretive Summary: Trichinellosis a disease that people can get by eating raw or undercooked meat from animals infected with the microscopic parasite Trichinella. While the production of safe and healthy products is one of the main objectives of the food industry worldwide, food products continue to be responsible for important outbreaks of disease in consumers. For example, trichinellosis has historically been linked to the consumption of raw or undercook pork. Trichinellosis a disease that people can get by eating raw or undercooked meat from animals infected with the microscopic parasite Trichinella. In this study, we evaluated the effect of 4 anthelmintic treatments on the viability of Trichinella spiralis encysted muscle larvae (ML) 55 days post infection in pigs. This study identified mebendazole, at 250mg/kg administered over a 3-5 day period as an anthelmintic which renders encysted Trichinella spiralis ML from pig tissues non-infective.

Technical Abstract: We evaluated the effect of 4 anthelmintic treatments on the viability of Trichinella spiralis encysted muscle larvae (ML) 55 days post infection (PI) in experimentally infected pigs. Muscle larvae were isolated from pig muscle by artificial digestion after oral treatment of pigs with Levamisole (8 mg/kg, daily for 5 days) and Mebendazole (50 mg/kg, daily for 5 days); Doramectin (0.3 mg/kg, single IM injection), and Moxidectin (0.5 mg/kg, single pour on). Isolated larvae from treated pigs were orally inoculated into mice to assess viability of ML from each treatment. Only Mebendazole treatment of pigs significantly reduced ML viability in mice. The effect of timing of the effective Mebendazole treatment on ML from a longer term infection was then examined in a second experiment. Analysis revealed that Mebendazole treatment of pigs with 250 mg/kg over 3 days (83 mg/kg/day) or 5 days (50 mg/kg/day) reduced numbers of ML recovered from pig tissues compared to untreated, infected controls, and rendered ML non-infective to mice; Mebendazole treatment of pigs with 250 mg/kg in a single dose was not effective in reducing ML numbers recovered from pigs or in impacting ML infectivity to mice. An examination of the lowest effective dose of Mebendazole on encysted ML was determined in a third experiment. Mebendazole of pigs with 5, 50, or 100 mg/kg over 3 days demonstrated that 5 or 50 mg/kg over 3 days insufficient to reduce infectivity in recovered ML, while 100 mg/kg (and 83 g from experiment 2) over 3 days significantly reduces infectivity of ML. This procedure provides a means to evaluate the efficacy of various anthelmintic treatments on the viability of Trichinella spiralis ML in pig tissues, and identified Mebendazole, at 83–100 mg/kg administered over a 3–5 day period as an anthelmintic which renders encysted Trichinella spiralis ML from pig tissues non-infective. As risk from Trichinella significantly impacts acceptance of pork from pasture-raised pigs, these data provide a method, especially for producers of these high-risk pigs, to eliminate the potential of Trichinella transmission from infected pork.