Effect of bacillus thuringiensis ssp. israelensis on the development of Plasmodium gallinaceum in Aedes aegypti (Diptera: Culicidae).
Adult, female Aedes aegypti, some of which had survived a sublethal dose (LC50) of Bacillus thuringiensis ssp. israelensis (Bti) as larvae, were fed on chickens with gametocytaemia of Plasmodium gallinaceum. Parasite development was monitored by dissecting samples of the mosquitoes immediately after the feed and on days 1, 7 and 9 post-feed, to check for the presence of gametocytes, ookinetes, oocysts and sporozoites, respectively. As the proportions of batches of fed mosquitoes found positive for gametocytes and ookinetes and the density of these parasite stages in the infected flies did not differ significantly between Bti-treated and untreated mosquitoes, ingestion of gametocytes and development of ookinetes did not appear to be affected by Bti exposure. However, the Bti-treated mosquitoes were significantly less likely to carry oocysts and those that were oocyst-positive carried significantly fewer oocysts than the untreated controls, indicating Bti-induced parasite loss during development of oocysts. Consequently, the proportion of mosquitoes with sporozoites was also significantly lower in the treated group. The study shows that mosquitoes surviving Bti treatment did not fully support parasite development. The implication of this effect is discussed in terms of malaria transmission.
Kala
M K
MK
Vector Control Research Centre (ICMR), Indira Nagar, Pondicherry, India.
Gunasekaran
K
K
D000330:Aedes / Q000382:microbiology / Q000469:parasitology*; D000818:Animals; D001413:Bacillus thuringiensis / Q000302:isolation & purification; D002645:Chickens; D005260:Female; D008288:Malaria / Q000635:transmission; D010572:Pest Control, Biological; D010964:Plasmodium gallinaceum / Q000166:cytology / Q000254:growth & development*; D013997:Time Factors