An examination of the prepatent period and the absence of a crowding effect in Angiostrongylus cantonensis in laboratory rats.

The effects of the size of the infective inoculum on the prepatent period and the effect of crowding on body volume were examined in populations of Angiostrongylus cantonensis (Metastrongyloidea: Angiostrongylidae) in the laboratory rat. Groups of five rats were infected with 5, 10, 20 and 40 L3 of A. cantonensis, respectively. The prepatent period was determined by examination of faeces using a modified Baermann technique. The prepatent period ranged from 37 to 45 days and was best described by a negative logarithmic curve (y = 51.21 + x-3.838). Based on developmental data in the literature, it is suggested that 37 days represents the minimum prepatent period for A. cantonensis in this host. Worm population showed a significant, positive increase with inoculum size, yet there was no relationship between worm volume and population size in females and a slight, but significant, increase in worm volume and population size in males from rats necropsied 76-84 days post-infection. It is concluded that crowding is likely to have little effect on worm size in rats naturally infected with A. cantonensis.