Zoophilia

ZOOPHILIA (from Greek zoon-animal and philia-love), the tendency of mosquitoes (particularly Anopheles) to preferentially or exclusively feed on animal blood rather than human blood, was generally noted for mammals by Grassi. Roubaud found in 14.2% of cases in Vendée (France) that Anopheles maculipennis contained human blood in their stomachs, and in more than 90% cases, blood of domestic animals. The most important feeding animals for Anopheles (according to Roubaud) are cows, horses, and mules; less attractive to Anopheles are pigs, goats, sheep, and dogs and chickens have very little significance. These circumstances may be the cause of anophelesism without malaria, since livestock diverts Anopheles, which ignores humans, including gametocyte carriers. Wesenberg-Lund reached similar conclusions for Denmark. Roubaud attempted to link the ability of Anopheles to feed on livestock (resp. on humans) with the formation of 'zoophilic races of Anopheles' in natural conditions, to which he tried to give morphological characteristics. Thus, in malarial areas, Anopheles are characterized by lower jaws whose terminal piliform appendage has about 13 teeth (they suck human blood), while in northern, non-malarial areas, Anopheles with 15 teeth are common (they feed exclusively on livestock). However (according to data from Ed. Sergent, Et. Sergent, Parrot, Foley), the number of teeth in both lower jaws of the same Anopheles can differ by three. Martini also does not recognize the existence of zoophilic races of Anopheles and attributes the differences in size of northern and southern specimens to the effect of temperature: at lower temperatures, mosquitoes are larger. Wesenberg-Lund believes that north of the Alps live larger Anopheles that feed on animals and ignore humans. South of the Alps, where domestic animals are kept outside the yards for most of the year, Anopheles feed on human blood, and malaria is present here. But in all such cases, it is not a matter of Anopheles race, but of a certain population with special physiological inclinations. Further study of the question has shown that the matter is not so simple. In Algeria, with a large number of livestock, Anopheles also uses humans, and malaria is widespread. Similar observations were made in Albania, Macedonia, and elsewhere. On the other hand, in India Cragg established a dependence between the decrease in livestock, famine, and the intensification of malaria. Different animals to varying degrees feed Anopheles. King and Bull by the precipitation method determined that Anopheles quadrimaculatus, taken from the dwellings of blacks on plantations, contained human blood in 2-7.2%, horse blood in 27-40%, cow blood in 24-47%, pig blood in 13-21%, and blood of other animals in 11%. However, these figures alone do not fully reflect the relationship between Anopheles and its hosts. In an experiment of choice between a sleeping person covered with a blanket, a horse, or a cow, a certain percentage of Anopheles suck the person, despite the fact that the area of his exposed body is very small compared to the surface of a cow or horse. Furthermore, different individuals of the same animal species to varying degrees divert Anopheles from another animal. The question of zoophilic Anopheles and the role of livestock in malaria prevention has been raised in the USSR. All data so far can be formulated by the following provisions: 1) there are no zoophilic races of An. maculipennis; 2) Anopheles maculipennis, in the presence of livestock, can partially or completely switch to feeding on their blood, which in itself leads to weakening (or disappearance) of malaria; 3) the factors determining the feeding regime of Anopheles are still elusive, and therefore there are as yet no practical possibilities of using livestock with certainty for the purposes of malaria prevention.