The role of lipid content in the infectivity of third-stage larvae of Heligmosomoides polygyrus.

The concurrent effects of aging on the lipid content of third-stage larvae (L3) of H.p. polygyrus and H.p. bakeri were described experimentally. It was shown that larval age was closely correlated with their infectivity. The infectivity of H. polygyrus in field and laboratory mice, as indicated by mean worm recovery, was significantly higher for one week old compared with 16 weeks old larvae. Image analysis has been used for the first time to quantify the lipid content of L3 of H. polygyrus with age. The proportion of lipid within infective larvae was reduced and their infectivity declined with age. It has also been found that larvae of H.p. polygyrus possess more lipid than H.p. bakeri suggesting that L3 larvae of H.p. polygyrus are physiologically different from those of H.p. bakeri and the additional lipid reserves assist in extending their survival time in the extremes of climatic conditions in the field.