Question

What are some examples on how over-dispersion relates to to the regulation of parasites and their hosts. (Need specific examples of parasites).

Answer 1

Over dispersion or clumped distribution of parasites means, parasites are distributing among hosts where few hosts harbor the majority of parasites and majority hosts are infected by few parasites. In other words the chances of infection differ.

For example overdispersed distribution of the tape worm (Hymenolepis citelli) in deer mice (Peromyscus maniculatus) is controlled by a gene locus.

75% of natural population of deer mice possessses resistence to the tape worm based on a single gene locus.

Due to this, the tape worm will get rejected from host's(mice) intestine before the tape worm mature.

Another example is infection of malarial parasites, Plasmodium species on leucocytes(WBC) of human. Here also each parasites has the same chance to occupy in any WBC, but blood smear indicates these parasites are clumped.

In these cases the regulation of parasites happens through over dispersion .