Filariasis transmission potential of mosquitoes to humans of different age groups.

Age-specific levels of Wuchereria bancrofti infection determined by microfilaremia in filarious 10 to 60 years old males from endemic village revealed that microfilaria intensity was higher in younger age, presumably because of increased vector biting rate of younger individuals. Out of 1334 Cx. pipiens captured while attempting to bite 51 child-adult bait pairs, 54.0% selected a host in the 10-15 age group. Biting preference towards children was more evaluated (79.2%) later than earlier in the night. Frequency distribution of age-specific biting collections indicated that 62.7% recorded exceeding numbers of bites on children, 21.6% adult biting, and 15.7% equal biting of one of the baits in the pair. Furthermore, 21.6% of the children were exposed to nightly bites ranging from 21 to 64 and only 7.8% of the adults experienced from 21 to 85 bites. Mosquito biting intensity averaged 14.2 and 11.6 bites/night for children and adults respectively. Children experienced 22.4% more bites per night than adults. Thus, children are more exposed to filaria infection and seem to represent an important source of infection. It is concluded that attempts at widespread control of filariasis in the densely populated Nile Delta, where youngsters may account for an immense proportion of the local population, should concentrate on immatures.