The attraction of mosquitos by human or animal baits in relation to the transmission of disease

Abstract

Experiments were made at three different sites in Malaya between 1952 and 1957 to compare the numbers of mosquitos attracted to man, calf or goat under the same conditions. The baits being compared (either two men and one calf or two men and two goats) were exposed simultaneously in two net traps placed about 50 yd. apart. This procedure is referred to as comparative trapping.The total number of mosquitos caught with each bait showed calf to be much the most attractive, followed by goats and then men. However, there were three species, the dark-winged form of Anopheles barbirostris Wulp, Aëdes albo-pictus (Skuse) and Culex pipiens fatigans Wied. that were attracted in larger numbers to man than to calf, and six species attracted in larger numbers to man than to goat.To compare the host preferences of the different species as between man and calf, the numbers of each caught with man and with calf have been expressed as a ratio (the man: calf attraction ratio). For most species the ratios from the different sites were much the same, showing that the method produced repeatable results. The data from the three sites were therefore combined.On the combined data the ratios range from 3·4:1 in favour of man for the dark-winged form of Anopheles barbirostris to 1:82 in favour of calf for A. vagus Dön.As might be expected, the ratios show that the vectors of malaria, filariasis and virus diseases are among the more anthropophilous species.Attraction ratios have been calculated from suitable data published by various authors for ten different species in five countries. The ratios obtained place the Anophelines in an order that agrees well with their status as vectors of malaria.It appears that if the results of comparative trapping are expressed as attraction ratios, this offers a method of comparing the host preferences of mosquitos of the same or different species, at different times and places in a country, or even in different countries.