Efficiency of anthelmintic treatment and its effect on microparasite dynamics in wild Mastomys natalensis

Abstract

Co-infections between helminths and microparasites can modulate the host immune response and alter disease dynamics, with potential implications for public health. However, identifying causal relationships in natural populations is challenging due to the complexity of ecological interactions. Perturbation experiments, where a specific parasite is selectively reduced, offers a powerful framework to directly test such interactions under natural conditions. In this study, we investigated potential helminth-microparasite interactions in the multimammate mouse (Mastomys natalensis) in Tanzania by experimentally reducing helminth infections in both captive and wild populations. We first confirmed that two anthelmintic treatments, ivermectin and pyrantel pamoate, effectively reduced gastrointestinal nematode burdens in wild-caught individuals. We then assessed whether helminth reduction influenced the prevalence of viral and bacterial infections in free-living populations. Our results revealed no significant short-term effect of anthelmintic treatment on microparasitic infections. These findings suggest that helminth-microparasite interactions in M. natalensis may be subtle, context-dependent, or require longer timescales to become apparent.

Keywords: Bartonella; Co-infection; Helminth-microparasite interaction; Ivermectin; Morogoro virus; Pyrantel pamoate; Wild rodent population.

Graphical abstract

Fig. 1

(A) Prevalence of nematodes and cestodes, and (B) predicted probability of Trichuris mastomysi infection in Mastomys natalensis across treatment groups (control, ivermectin and pyrantel pamoate), with 95 % confidence intervals.

Fig. 2

(A) Predicted probability of Morogoro virus (MORV) seroconversion by treatment group and (B)Bartonella infection over time (weeks) for each treatment group (control, ivermectin and pyrantel pamoate) in a wild Mastomys natalensis population. Error bars represent 95 % confidence intervals and dashed lines indicate linear trends.

Fig. 3

Phylogenetic relationship of Bartonella sequences identified in this study. A Neighbor-Joining tree was constructed using the Tamura-Nei model based on ITS gene sequences, with reference sequences from previously identified Bartonella isolates in rodents and recognized Bartonella species. Bootstrap support values above 70 % are shown (1000 replicates). Subgroups were defined based on a 93.9 % similarity cut-off (La Scola et al., 2003). The scale bar represents 0.1 nucleotide substitutions per site. The representative sequences of each genogroup have been submitted to GenBank under the following accession numbers: Genogroup A – PV788829, B – PV788832, C – PV788831, D1 – PV788828, D2 – PV788830, D3 – PV788833, and D4 – PV788834.

Fig. 4

Visualization of individual Bartonella infection patterns across 10 sampling time points for each treatment group (control, ivermectin and pyrantel pamoate) in wild Mastomys natalensis populations. Rasters display the infection status (positive with respective genogroup, negative or no sample) for each individual at each time point.