Description of four new species of Heligmosome Nematodes parasites of the gut of Trichys lipura: --Heligmonella limbooliati n. sp. has a synlophe of Heligmonella-type and a bursa related to Cordicauda. --Cordicauda trichysi n. sp. is characterized by the relatively small dorsal lobe of the bursa, numerous cuticular ridges and the origin of the 8th rib at the distal third of the dorsal rib. --C. malayensis is closely related to C. trichysi (the female of the two species are morphologically identical but the two species can be separated by the larger dorsal lobe of the bursa and the longer spicula of C. malayensis). --C. magnabursa n. sp. is separated from the other species of the genus by the peculiar morphology of the bursa and the female's tail, dorsally bent. The fauna of Trichys is compared to that of Atherurss africanus, which is parasitized by 8 coparasites species: One Heligmonella and seven Paraheligmonina. From a phyletic as well as an ecological point of view (relative abundance and species location in the gut) the two fauna seem to have evolved in a parallel way, one in Africa, one in Asia, from a single Heligmonella type Nematode, after the host's partition.
In Armigeres subalbatus, 60% and 3% of the ingested Brugia pahangi microfilariae (mf) respectively migrated into the haemocoel and the thorax within 5 minutes post ingestion (p.i.). Most of the mf had migrated from the gut into the haemocoel within the first 10 minutes p.i. There was no correlation between the number of mf ingested and the migration rate though those in mosquitoes with a low mf burden tend to migrate earlier. At 24 hours p.i., 5-30% of the mf were still in the gut; 19% of these mf were immobile. At 48 hours p.i. only 2% of the mf were mobile. B. pahangi mf isolated from blood meals at 24 hours p.i., failed to develop when inoculated into Armigeres subalbatus. 54% and 73% of the mf isolated from a 24 hour old clotted blood of a B. pahangi-infected cat and fresh peripheral cat blood respectively developed into stage-1 larva. Probably mf left in the midgut at 24 hours p.i. are the young and immature worms and are physiologically incapable of penetrating the gut.
The filaria vector competence of Anopheles stephensi was compared with Brugia-susceptible Aedes aegypti Liverpool strain, An. gambiae Badagry Lagos strain and An. dirus Perlis Malaysia strain. An. stephensi ingested more Brugia pahangi microfilariae, had the highest infectivity rate and yielded more infective mosquitoes than the other two anopheline species. The overall vector competence of An. stephensi was 0.13 times that of Ae. aegypti, 0.62 times that of An. gambiae and 2.17 times that of An. dirus. However, heavy mortality among infected An. stephensi in the present investigation indicates that the filaria vectorial capacity of the mosquito might be limited epidemiologically. The relationship between filaria vector competence and mosquito foregut armature is discussed. It was observed that the relative vector competence of the three anopheline species tested was in the same order as their relative degrees of armature elaboration. The converse would be expected if foregut armatures really give partial protection to the mosquitoes against filarial infection. It is suggested that high host microfilariae density favours larval survival proportional to the degree of armature development in Anopheles (Cellia) species.