On a mechanistic process of macroparasite aggregation

Parasite aggregation, a recurring pattern in macroparasite infections, is considered one of the “laws” in parasite ecology. Few hosts have a large number of parasites while most hosts have a low number of parasites. This pattern has been widely studied using phenomenological models, by using the negative binomial distribution. However, to infer the mechanisms of aggregation, a mechanistic model is essential. Here we formulate such a mechanistic model of parasite aggregation in hosts without initially assuming a negative binomial distribution. Our results show that a simple model of parasite accumulation still results in an aggregated pattern, as shown by the derived mean and variance of the parasite distribution. By incorporating the derived mean and variance to the host-parasite interaction, we can predict how aggregation affects the population dynamics of the hosts and parasites through time. Thus, our results can directly be applied to observed data as well as can be utilised in designing statistical sampling procedures. Overall, we have shown how a plausible mechanistic process can result in the often observed phenomenon of parasite aggregation occurring in numerous ecological scenarios. Key Findings Parasite aggregation is considered one of the “laws” in parasite ecology – few hosts harbouring a large number of parasites. While examples abound, there is lack of mechanistic models available to explain the phenomenon Taking a bottom up approach we construct a simple model of host-parasite population dynamics which naturally results in parasite aggregation – negative binomial distribution of parasites in the host population While providing a plausible mechanism our model can be readily deployed in field work when designing sampling methodology or analysis of available data.