The Effects of Helminth Removal on Coccidia Superspreaders in a Wild Peromyscus Population

Abstract

Most living organisms are coinfected with multiple parasites that interact with each other and the host in complex, dynamic relationships. One way to explore these types of coinfected ecosystems is to selectively remove a dominant parasite from a host. This study explored the consequences of intestinal nematode removal on coccidia populations residing in the gut of wild Peromyscus mice in order to better understand macroparasite-microparasite relationships. It specifically focused on treatment effects in superspreaders of coccidia. These superspreaders were found to be sub-adult reproductive male mice (+10 log eggs/g, p = 2e-5). Hosts with characteristics of these superspreaders responded best to treatment: there was a significant decrease in coccidia burden and increase in parasite aggregation for males (-4.23 log eggs/g, p = 0.01; k < 0.10, p = 0.04) and sub-adults (-4.84 log eggs/g, p = 0.02; k < 0.17, p = 0.07). Furthermore, females showed a bipolar response to treatment, with 76% segregating into either a high infection category (38%; log 3-4 eggs/g) or a low infection category (38%; log 0-1 eggs/g). These categories are hypothesized to represent normal and pregnant female mice, respectively. Lastly, there was a trend towards decreasing prevalence of coccidia in the treated population (p = 0.11). These findings reveal notable heterogeneity in population responses to treatment and support a direct, immune-mediated interaction between nematodes and coccidia. It also highlights the benefits of targeting superspreaders to halt coccidia transmission, as these mice showed most pronounced decrease in coccidia burden and increase in parasite aggregation, predictive of more probable disease extinction within a population. The treatment outcomes described here are also applicable to human health, as deworming is a widely used practice in developing countries. Relationships drawn between the response of immune compromised mice to anthelmintics and the response of HIV positive patients to these drugs can be useful in predicting the outcome of health interventions and in informing global health policy.