Incidence of Blood Parasites in Birds Collected in Southwestern Georgia

Abstract

In connection with studies of the susceptibility of Anopheles mosquitoes to avian malarias, surveys were made to determine the incidence of blood parasites of birds in southwestern Georgia. This work was undertaken after the report of high sporozoite rates in A. crucians and A. quadrimaculatus from an area in South Carolina where human malaria was declining (Sabrosky, McDaniel, and Reider, 1946). Sporozoite rates in that area have remained consistently high, although human malaria has not been demonstrable in the area for more than three years (Atchley, 1952). Since the obvious possibility exists that the sporozoites found in these surveys were not of human origin, it is desirable to determine the available sources of infection. Until the unknown sporozoites are related to specific species, no surveys of plasmodia in Anopheles can be evaluated properly. Investigations designed to provide information on this problem have been reported by Hart (1949), Hunninen and Young (1950), and Hunninen, Young, and Burgess (1950). The purpose of the work in the Georgia area was to determine the susceptibility of local Anopheles to various malarial parasites in lower animals of the area and to determine if sporozoites were present in wild-caught Anopheles in a locality where human malaria had been undetected for longer than in the South Carolina area (Goodwin, 1950). Data on the incidence of blood parasites in various species of birds are presented in this report. Most birds were obtained by trapping in the vicinity of the station in Baker County, Georgia. During a survey of summer birds of the area, Norris (1951) provided specimens from several adjoining counties: Decatur, Seminole, Early, Clay, Dougherty, Calhoun, Tift, and Macon. Blood films were obtained from 65 mourning doves during the course of a special study of this species by Hopkins and Odum (1952). From June through September 1948 birds were shot as well as trapped when special attempts were made to collect several specimens of species known to be infected with specific parasites and to obtain insectivorous birds that were not taken with grain-baited traps. Blood was obtained from a leg or toe vein of living birds and from birds that were shot if films could be prepared immediately. Films were made from blood obtained from the heart in other instances. During the special survey for insectivorous species, birds were shot and the thorax opened as quickly as possible. Incisions were made into the heart and lungs, and the thoracic cavity was then washed with about 5 cc. of heparinized saline. The fluid in the cavity was then aspirated into a syringe and expelled into a sterile rubber-capped vaccine vial. A blood film was made from the residual material in the syringe. The vial was kept refrigerated until it was returned to the laboratory where inoculations into Plasmnodium-free canary birds were made. Periodic checks were made on the viability of parasites handled