Angiostrongylus cantonensis, a.k.a. the rat lungworm, is a parasitic nematode and the major etiological agent of human eosinophilic meningitis. The nematode’s natural transmission cycle includes rats and gastropods as definitive and intermediate hosts, respectively. Humans and wildlife are susceptible to accidental infection by ingestion of an infected intermediate host. While many parasitic nematodes infect a narrow range of host species, A. cantonensis is a broad parasite and potentially any snail or slug can harbor A. cantonensis larvae. However, both prevalence (proportion of the population infected) and intensity (density of worms in host tissue) vary among gastropod species. We studied the impact of host traits (species, size) and environment (rainfall) on A. cantonensis prevalence and intensity among and within intermediate host species. We collected 960 individuals representing 16 gastropod species from 39 sites located across a rainfall gradient (566 – 3861 mm) on the island of Oahu, Hawaii. Gastropods were weighed and screened for detection of A. cantonensis by qPCR. We employed a model selection approach using AICc and fit the data to candidate sets of nested mixed models to estimate the influence of gastropod species, size, and rainfall on the probability and intensity of A. cantonensis infection.
Results/Conclusions
182 individuals (19%) of 14 of the 16 species tested positive for A. cantonensis. After controlling for location and time of collection, probability of infection varied across species (30% - 0.4%). Within species, we found a positive relationship between prevalence and size; larger individuals of a species had a higher probability of infection. Additionally, species weighing >200 mg at maturity were 8.3 times more likely to be infected than smaller species. Nematode burden was unrelated to host size either within or across species, but varied across host species. Prevalence was positively correlated with rainfall (AICc = 8.7), although the slope of this relationship varied among species. Nematode burden was positively correlated with rainfall (AICc = 3.7), this relationship homogeneous across all species. These results suggest that variation in A. cantonensis infection is associated with a combination of demographic structure and composition of gastropod communities and regional precipitation, which could underlie heterogeneity in the risk of angiostrongyliasis in humans and wildlife across landscapes. Parasites are integral components of an ecosystem and shifts in their abundance and prevalence can influence the fitness, reproduction and behavior of host species, which has implications for the surrounding ecosystem and resident communities.