The potential health impact of ivermectin mass drug administration for malaria control on swine in Mozambique
Assenga, Alphonce Alexander
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BACKGROUND: Both endo- and ectoparasites pose a great challenge to the health of pigs worldwide, placing a significant burden on low-resource countries where veterinary care is minimal. As part of a larger clinical trial assessing the use of ivermectin (IVM) mass drug administration to humans and pigs for the control of malaria vectors in the Mopeia district in Mozambique, a longitudinal study to assess the impact of IVM administration on pig health was performed. METHODS: Beginning in March 2022, IVM was administered to pigs in the intervention area once a month for three consecutive months. Seventy pigs from the treatment group and 70 pigs from the control group were randomly selected for inclusion in the study. Fecal samples were collected monthly for three months and analyzed for the presence of strongyle eggs, strongyle eggs in the larval stage (strongyles – larval) and Ascaris suum using the modified McMaster test. Fecal samples were also collected two weeks after each dose of IVM was given to pigs in the treatment group for determination of a fecal egg reduction count. Juvenile pigs were measured twice a month for the first 3 months of the study, then once monthly for another three months. Visual exam for ectoparasites was performed on all pigs for the presence of ticks, lice or scabies at the same time points. RESULTS: Overall, 55% [95% CI: 48-62%] of pigs were positive for Ascaris suum, 95.2% [95% CI: 91-98%] were positive for strongyle eggs, and 72.5% [95% CI: 65.5-79%] were positive for strongyle – larval. A significant difference in the ivermectin treatment group was only seen one month after the second dose of ivermectin was administered: pigs in the treatment group had a 23.6% lower prevalence of strongyles (p = 0.003) and 18% lower prevalence of strongyles – larval (p = 0.03). Pigs in the treatment group also had lower EPG for Ascaris suum (diff = 102 EPG; p = 0.006), strongyles (diff = 642 EPG; p < 0.001), and strongyles - larval (diff = 217 EPG; p < 0.001). Analysis of covariance regression found no significant difference(P>0.05) in average daily weight gain (ADG) between the treatment and control groups. CONCLUSION: IVM delivered once monthly for three months has a small impact on pig health. To counteract the multiple health challenges pigs face in these settings, different dosing schedules along with education on husbandry issues related to nutrition and sanitation should be investigated in order to maximize impact on pig health.
General Audience Abstract
A study was conducted in rural Mozambique in the district of Mopeia to determine the effectiveness of ivermectin against common parasites of swine when administered to pigs. The study began in March of 2022, at the beginning of rainy season, and ivermectin was given to pigs once a month for three months. Pigs were visited twice a month for the first three months, and then once a month for another three months. At various time points, fecal samples were collected, pigs were examined for evidence of ectoparasites (ticks, lice and scabies infestation), and young pigs were measured to determine their rate of growth. Fecal samples were analyzed for the presence of common internal parasites (endoparasites) affecting pigs in the area. The burden of endo and ectoparasites was estimated before any ivermectin was administered, and then compared in treated and untreated pigs over the course of the study. Similarly, the effect of ivermectin on growth rates in young animals was determined. The results of this study found that there was a high burden of common endoparasites in pigs in the Mopeia district, which was only minimally affected by the use of ivermectin delivered once a month. Among the treated pigs, a fecal egg count reduction test suggests that these parasites are potentially resistant to ivermectin, although other issues may be responsible for these results. The burden of ectoparasites was generally low (<10%), with ivermectin only significantly reducing the prevalence of ticks. Young animals that received ivermectin had a 15% increase in their growth rate, but this was not statistically significant. In conclusion, the use of ivermectin once a month for three months in pigs, as part of a malaria intervention, has some minimal positive health effects on treated pigs. Given the poor management practices, poor nutrition and lack of veterinary care in these pigs, it is likely that to have a greater impact on pig health, ivermectin will need to be delivered under a different dosing schedule and alongside owner education on pig management practices.
- Masters Theses