Transmission of Fowl-Pox by Mosquitoes.

Abstract

The mode of transmission of certain virus diseases of chickens is still obscure. Fowl-pox as well as fowl plague are common diseases of the barnyard, both, according to reports, occurring during the spring and fall months. Many workers 1 , 2 state that attempts to infect by contact or by ingestion of infected foodstuffs usually fail. These facts suggested the possibility of insect transmission.

Since fowl plague is not prevalent in this country our experiments were conducted with fowl-pox. Using Culex and Aëdes mosquitoes it was possible to transfer the disease from infected to healthy fowls with considerable regularity by interrupting the mosquitoes after they began feeding on infected areas of the diseased chicken and allowing them to complete their meal on the comb or wattles of healthy ones. Positive transmission of the disease was obtained even when the interval between feedings was 2 hours. As a rule, 7 days after the feeding, typical minute vesicles appeared on the normal fowl wherever the proboscis of the insect had been inserted.

In one experiment transmission was obtained under conditions approximating those existing in nature. Two healthy and one infected chickens were placed in a box covered with fine-mesh copper screen. Four freshly hatched Culex mosquitoes were released in this box. After 7 days 2 typical discrete lesions appeared on the left wattle of one of the healthy fowls. In a control group without mosquitoes none of the chickens showed evidences of infection after a period of 17 days.

It seems, therefore, that where the lesions are superficial, as in fowl-pox, interrupted feedings by mosquitoes and possibly also by blood-sucking flies may play an important, if not the most important rôle in the dissemination of the disease. Our experiments thus far indicate that transmission of this kind is a mechanical transference of the virus; consequently it is not essential that the infectious agent be able to establish itself in the insect.