ON THE EPIZOOTIOLOGY OF INFECTIONS CAUSED BY LEUCOCYTOZOON SIMONDI IN ALGONQUIN PARK, CANADA

Abstract

Transmission of Leucocytozoon simondi in ducks is initiated by Simulium anatinum in May and this fly is the vector for 2–3 weeks. Simulium rugglesi is the vector in June and July and sporadically until September in some years. Epizootics are related to the feeding and habitat specificity of the flies, their longevity, their flight range, the length of the life cycle of the parasite, and its specificity for ducks. Flies were marked with 32P to determine their flight range. Specificity was assessed by injecting birds with sporozoites from simuliids that fed on birds infected with different species of Leucocytozoon. All ducks exposed to the flies in May, June, and July, along a lakeshore, became infected and many died. Transmission of the parasite, although most pronounced on the lakeshore and along a river that harbored the larval stages of the simuliids, did occur over the water 100 yd from shore and in the woods. Transmission occurred only occasionally 15 ft above water or ground level.