Dna Profiling of Human Blood in Anophelines From Lowland and Highland Sites in Western Kenya

Abstract

We used polymerase chain reaction (PCR)-based DNA profiling to determine the person from whom Anopheles funestus and An. gambiae collected in natural human habitations obtained their blood meals. Less than 20% of human hosts contributed to > 50% of all blood meals, and 42% were not bitten at all, including people in the age group bitten most often. As expected, bites were unevenly distributed by age (young adults > older adults > children). Use of untreated bed nets by adults, but not children, seemed to redirect bites to children. Multiple blood meals in a single gonotrophic cycle occurred frequently enough to be epidemiologically important (14% for An. funestus and 11% for An. gambiae). Mosquitoes that did not bite a person who slept in the collection house can affect estimation of entomological risk. Mosquito-human interactions did not differ across ecologically and epidemiologically distinct highland and lowland sites.

Frequency of Multiple Blood Meals Taken in a Single Gonotrophic Cycle by Anopheles arabiensis Mosquitoes in Macha, Zambia

“…This rate is much higher than the 0-11% rate reported for An. gambiae s.s. in Kenya, 13 or the 14% rate reported for An. funestus in Tanzania.…”

“…Primers fluorescently tagged with HEX and FAM were used to amplify DNA at the CTT (CSF1PO and TPOX) and Silver STR (D7S and D13S) loci. 13,25 Each 20-μL reaction contained 10 mM Tris, pH 8.3, 50 mM KCl, 1.5 mM MgCl 2 , 0.01% gelatin, 0.8 mM dNTPs, 3.2 units Taq polymerase, 25 pmol each forward and reverse primer, and 1 μL template DNA. PCR conditions consisted of a two-minute initial denaturation at 96°C, followed by 30 cycles for 1 minute at 94°C, 1 minute at 60°C, 1.5 minutes at 70°C, and a 45-minute final extension at 70°C.…”

“…Previous DNA fingerprinting studies have estimated the multiple blood meal frequency in An. gambiae (0-11%), 13,14 An. funestus (3-14%), 15 and Aedes aegypti (18%).…”

“…gambiae possibly by increasing the blood meal volume at which a mosquito stops hostseeking behavior, or by decreasing apyrase activity. 13 We therefore investigated whether P. falciparum infection correlates with multiple blood feeding in An. arabiensis .…”

“…However, if infected female mosquitoes take more than one human blood meal per gonotrophic cycle, the effective biting rate is increased, increasing the EIR and malaria transmission risk to humans. 13 Therefore, accurate estimation of the multiple human feeding rate is critical to determining and understanding the intensity of Plasmodium transmission.…”