Fixed and stained blood smears of over 3000 birds resident in Algonquin Park, Canada, have been examined for blood parasites. Sixty per cent of the adults and 40% of the immature birds harbored one or more blood parasites. Leucocytozoon occurred in 60%, Trypanosoma in 48%, Haemoproteus in 26%, Microfilaria in 7%, and Plasmodium in 2% of the infected birds. High incidence and high parasitaemia of Leucocytozoon, Trypanosoma, and Haemoproteus coincided with the occurrence of large numbers of ornithophilic simuliids and Culicoides and preceded the time when most hippoboscids were recovered. Differences in incidence of parasites and the level of parasitaemia in different birds when considered in relation to the occurrence and feeding behavior of various ornithophilic flies suggest that simuliids are the vectors of Trypanosoma, and Culicoides transmit Haemoproteus in this area.
Attraction of Simulium euryadminiculum to the common loon is confirmed and attraction of this fly to an ether extract of the tail of the loon is demonstrated. S. rugglesi is attracted a t the lakeshore to a combination of an ether extract of the uropygial glands of ducks and C02, and to a lesser extent to COz alone, but not to the extract alone. S. aureum, S. latipes, S. quebecense, S. croxtonz, and Prosimulium decemarticulatum are attracted to a source of CO? placed in the forest canopy.
Ducks exposed outdoors in Algonquin Park during the summer became infected with Leucocytozoon simondi and many of them died from the infection in June and July when black flies were abundant. The minimum prepatent period was five and a half days. Young parasites were observed in erythrocytes and lymphocytes; mature gametocytes, as shown by exflagellation of microgametocytes, occurred in round and elongated host cells. Asexual development was observed in the spleen, liver, heart, brain, lung, lymphoid tissue, and pancreas. The schizonts were large and contained, at maturity, more than a million merozoites about 1 μ in diameter. Sexual development of the parasites within two species of black flies was completed in three days at summer temperature. Ookinetes were present in the stomach of black flies about four to six hours after the flies had ingested blood containing gametocytes. Developing oocysts were found free among the stomach contents of flies 40–48 hr. after the blood meal. Sporozoites were observed between 60–70 hr. after the flies had ingested gametocytes. Artificial infections were produced in ducks following the injection of macerated black flies that had fed two and one-half to seven days previously on infected ducks. The resulting infections were less severe than those that resulted from natural infections, although the pattern was similar and a minimum prepatent period of eight days was observed. The asexual cycle was completed in fewer than six days although some asynchronicity was apparent. Artificial infections were produced following the injections of blood, spleen, liver, lung, and bone marrow that were taken from ducks at various intervals following their exposure to natural infection. The minimum prepatent period in these infections was eight days and low parasitemias were produced. Gametocytes survived for at least one week in peripheral blood. Ducks developed some resistance following repeated infections but single infections did not protect ducks that were exposed to infection six weeks later. Heavy infections developed in ducks that were splenectomized. The leucocytosis and anemia associated with infections were measured and recorded.
Blood smears from 43 species of bird, mainly from the South Island of New Zealand, were examined for haematozoon parasites. An undescribed species of Leucocytozoon was discovered in the Fiordland crested penguin, Eudyptes pachyrhynchus. It is assigned the name Leucocytozoon tawaki, and the gametocytes are described. Preliminary observations of its development in Austrosimulium australense, A. dumbletoni, and A. ungulatum are discussed, and the ookinete, oocyst, and sporozoite stages within these hosts are briefly described.
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