The impact of multiple infections on wild animal hosts: a review

Bordes, Frédéric; Morand, Serge

This criticism may be enhanced as most of the field studies focusing on host genetics have mainly considered parasite loads using faecal eggs counts (FEC), a technique which consists of detecting both the number of helminth morphotypes and the number of eggs (supposed to be correlated to the number of intestinal worms) in faecal samples (60, 63, 64, 69, 73, 74) . Despite the great interest (and its increasing popularity) of such methodology due to its non-invasive nature for wildlife populations and the interesting information extracted from these data, there are important limits related to FEC. First, they allow detection mostly of helminths and coccidians. Ecologists may therefore underestimate helminth diversity per se due to low fecundity, low infestation levels or intermittent egg excretions in helminth parasitism. Second, egg counts do not always correlate with the number of adult worms within the intestinal tracts of the animals (94) . The relationship between indirect measures and actual worm burden is then very complex, stressing that egg counts are not always a reliable method for estimating the numbers of parasites within the gastrointestinal tract and also parasite loads. These serious difficulties will probably be solved, at least to identify the full diversity of parasites with new molecular tools (such as new generation of sequencing technologies).