Susceptibility of geographically distinct Aedes aegypti L. from Florida to Dirofilaria immitis (Leidy) infection.
In the present study, five geographically distinct populations of Aedes aegypti L. from various regions of Florida were compared for their susceptibilities to Dirofilaria immitis (Leidy) infection. The populations were from Gainesville (North Central), Jacksonville (North Eastern), Naples (South Western), Sarasota (West Central), and Vero Beach (East Central). Mosquitoes of all the populations had fewer parasites in their Malpighian tubules 6 and 13 days after blood feeding compared to the number of microfilariae initially ingested. There was no significant difference in the mean number of the total parasites per female 6 and 13 days after taking an infectious blood meal. In comparison, significantly larger numbers of the microfilariae completed development in the laboratory-selected Vero Beach susceptible strain. Females excreted microfilariae within 72 hr. of engorgement on an infected dog and the Gainesville, Jacksonville, Naples, and Sarasota populations had 20-23% females that lacked ovarian development six days after blood feeding. Out of these, in 16-22% of the females from the Jacksonville, Naples, and Sarasota populations, parasite development was arrested mostly as moribund prelarvae and only few developing larvae were observed. All females of the Gainesville population that did not develop eggs (20%) also lacked parasites. In the Jacksonville population, 23% of the females that matured eggs had no infection. Eight percent of the females from the Sarasota population exhibited a similar response. Low survivorship was observed at 6 and 13 days after imbibing an infectious blood meal. Females showed melanization of microfilariae in the Malpighian tubules, on the midgut wall, and in the hemocoel. Cellular melanization response was observed in the hemocoel, whereas, a humoral melanization response was observed in the Malpighian tubules. The Vero Beach susceptible strain showed maximum vector efficiency and lowest survival at 13 days post-blood meal compared to the Jacksonville and the Gainesville populations.
Institute of Food and Agricultural Sciences, University of Florida, Florida Medical Entomology Laboratory, Vero Beach 32962, USA.
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Mahmood
D000330:Aedes / Q000469:parasitology* / Q000502:physiology; D000818:Animals; D004183:Dirofilaria immitis / Q000472:pathogenicity / Q000502:physiology*; D004285:Dogs; D005260:Female; D005431:Florida; D005843:Geography; D008317:Malpighian Tubules / Q000469:parasitology*