Population genetics of Parascaris equorum based on DNA fingerprinting

The large roundworm of horses, Parascaris equorum is considered ubiquitous in breeding operations, and is regarded as a most important helminth pathogen of foalsOver the past decade, this parasite has been reported increasingly resistant to anthelmintic drugs worldwideThis paper reports analysis of the population genetic structure of PequorumAdult parasites (n=194) collected from Sweden, Norway, Iceland, Germany, Brazil and the USA were investigated by amplified restriction fragment length polymorphism (AFLP) analysisThe genetic variation was low (Hj=0.12-0.4), for the global population of wormsThis was accompanied by a weak degree of population structure (Fst=0.2), low gene flow (Nm=1.0) and low mutation rate (4Nμ=0.07)Thus, the low genetic diversity is probably a result of a low mutation rate in DNA, although the gene flow (due to global movement of horses) is large enough to allow the spread of novel mutationsSurprisingly, isolates from Icelandic horses were not found to be different from other isolates, in spite of the fact that these have been isolated for thousands of yearsThe study indicates that the global Pequorum population is essentially homogenous, and continents do not appear to be strong barriers for the population structure of this speciesConsequently, the potential spread of rare anthelmintic resistance genes may be rapid in a homogenous population.