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Recent genetic evidence suggests that parasitic protozoa often reproduce by "selfing," defined as sexual stages from a single, clonal lineage fertilizing each other. Selfing favors production of an excess of female over male progeny. We tested whether the proportion of male gametocytes of blood parasites of the genus Haemoproteus was affected by variables that could influence the probability of selfing. Proportions of male Haemoproteus gametocytes from 11 passerine host populations were not affected by the age of the parasites' avian hosts, date in season, sex of host, intensity of host's infection, or prevalence of parasites within host populations.

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Hemograms were determined for 26 Cooper's (Accipiter cooperii) and 55 sharp-shinned hawks (Accipiter striatus) captured during spring migration (27 March to 12 May 1987) on the south shore of Lake Ontario, New York (USA). No significant differences were noted in packed cell volume and estimated total solids between the species. However, Cooper's hawks had significantly higher total white blood cells counts and higher concentrations of heterophils, monocytes, and eosinophils. Proportionally, lymphocytes made up a smaller percentage of the differential count in the Cooper's hawk. Eosinophil concentrations and percentages of the differential count were significantly higher in the females of both species. Both species had a high prevalence of Leucocytozoon toddi and Haemoproteus spp. infection. Haemoproteus nisi and H. elani were identified in both hawks. Trypanosoma avium was identified in a single Cooper's hawk and Plasmodium circumflexum was identified in a sharp-shinned hawk. Prevalence of Leucocytozoon toddi and Haemoproteus spp. infections were significantly higher in the birds caught late in the spring as compared to those caught earlier in the spring; this was evidence for a spring recrudescence of patent parasite infections.

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Linear measurements and derived indices from striated trypanosomes in nine species of sub-Saharan birds representing seven families of the Passeriformes, were compared. The dimensions of the striated trypomastigotes from the Carduelinae, Estrildidae, Nectarinidae, Passeridae, Pycnonotidae, Turdinae and Zosteropidae were similar to each other as well as to those of the striated trypanosomes from the boreal owl (Strigidae). All these trypanosomes were considered to be Trypanosoma avium Danilewsky, 1885. A further 20 avian species were considered to harbour T. avium, thus greatly extending the reported host range of this trypanosome. Non-striated trypanosomes from the estrildid Uraeginthus angolensis closely resembled Trypanosoma bouffardi Leger & Blanchard, 1911 in appearance and dimensions, and were considered to be of this species. Additional host records for T. bouffardi from an additional nine avian species have been reported. The uniquely small and stumpy Trypanosoma everetti Molyneux, 1973 was reported from an additional 18 avian species. A large non-striated trypanosome from the laughing dove, Streptopelia senegalensis, was identified as Trypanosoma hannae Pittaluga, 1905 and this species was re-described. An infection of this parasite was also found in a single Streptopelia capicola and a single Streptopelia semitorquata. Two trypanosomes seen in the francolin, Francolinus natalensis, were identified as Trypanosoma calmettei Mathis & Léger, 1909.

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Blood smears were examined from 935 individuals of 19 migrant and resident bird species collected in Louisiana. Of these, 320 (34.2%) harbored hematozoa. The prevalences of parasites were as follows: Haemoproteus spp. 22.8%, Trypanosoma spp. 6.9%, unidentified microfilariae 5.0%, Plasmodium spp. 3.4%, and Leucocytozoon spp. 1.3%. These data are consistent with other reports from the region. Infections were observed in 33% of the individuals in the 13 migrant species sampled and 33% of the individuals in the 6 resident species.

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Two doves from the same aviary died following heavy infections with Haemoproteus columbae. Histopathological examination of various organs revealed numerous schizonts and megaloschizonts. There seemed to be two cycles of schizogony, one within the muscles and another in a wide range of tissues. The shape and size of the schizonts appeared to be a function of the site of formation. The rupture of megaloschizonts, especially in the striated muscles caused extensive fibre necrosis and the resultant muscle damage, is believed to be the major cause of mortality.

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Four species of Leucocytozoon, L. caprimulgi of the Caprimulgidae (nightjars), L. marchouxi of the Columbidae (pigeons and doves), L. grusi of the Gruidae (cranes) and L. tawaki of the Spheniscidae (penguins) are re-described. Leucocytozoon turtur is declared a synonym of L. marchouxi.

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The leucocytozoids of ten families of Passeriformes--Estrildidae, Fringillidae, Laniidae, Nectariniidae, Passeridae, Ploceidae, Promeropidae, Pycnonotidae, Sturnidae and Zosteropidae--are reviewed. Leucocytozoon roubaudi from the Estrildidae, L. fringillinarum from the Fringillidae, L. balmorali from the Laniidae, L. gentili from the Passeridae, L. bouffardi from the Ploceidae, L. brimonti from the Pycnonotidae and L. zosteropis from the Zosteropidae are re-described. Leucocytozoon dutoiti, L. nectariniae, L. deswardti, L. pycnonoti and L. sturni are new species described from the Fringillidae (Carduelinae), Nectariniidae, Promeropidae, Pycnonotidae and Sturnidae respectively while L. monardi is considered to be a synonym of L. gentili and L. molpastis is considered to be a synonym of L. brimonti.

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The prevalence of avian haematozoa in 826 species of birds representing 73 families of sub-Saharan birds as recorded in the literature or in the files of the International Reference Centre for Avian Haematozoa and the Veterinary Research Institute is presented. The most commonly occurring blood parasites were members of the genus Haemoproteus which were represented by 63 species which occurred in 19.1% of the sample. Twenty-five species of Leucocytozoon were recorded in 8.3% of the birds and represented the second most frequently encountered group of haematozoa. Species of Plasmodium, Trypanosoma, and filarioids (as microfilariae) occurred in 3.5%, 2.5% and 2.8% respectively of the birds sampled; species of Aegyptianella, Atoxoplasma, Babesia and Hepatozoon were infrequently seen. An annotated list of the birds examined for haematozoa is presented and brief descriptions of the species of Haemoproteus and Leucocytozoon in birds of the sub-Saharan zone are included.

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Bloodsmears were taken from separate groups of five helmeted guineafowls, Numida meleagris, shot at approximately monthly intervals at Skukuza and near Lower Sabie in the Kruger National Park during the period August 1988 to August 1990. Ninety-eight (86%) of 114 guineafowls had single or multiple infections of Aegyptianella sp., Haemoproteus pratasi, Hepatozoon sp., Leucocytozoon neavei, Plasmodium circumflexum and Trypanosoma numidae. The apparent seasonal prevalence of Aegyptianella sp., H. pratasi and L. neavei, the three most commonly occurring parasites (42%, 49% and 56% of birds infected respectively), is probably dependent on the presence of their respective vectors.

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A total of 641 birds representing 135 species of 25 families from Noel Kempff Mercado National Park in west-central Bolivia was examined for hematozoa; only 33 (5.1%) harbored blood parasites. Microfilariae were the most commonly encountered hematozoans, followed, in numerical sequence, by species of Haemoproteus and Plasmodium; Trypanosoma, Atoxoplasma, and Hepatozoon were seen infrequently. The survey included 13 new host-parasite records, and 58 species of birds were examined for blood parasites for the first time; 43 were parasite-free. The low prevalence of parasitism recorded in this survey is compared to other areas in the Neotropical region and to prevalence of blood parasites in the avifauna of other major land masses.

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A total of 196 birds of 31 species from 15 families from northeastern Mexico was examined for blood parasites; 25 birds (12.8%) of 11 species harbored 1 or more species of hematozoans. Species of Haemoproteus accounted for half of the total infections encountered. Leucocytozoon simondi was found in 2 Mexico ducks (Anas diazi) and this represents the first record of the transmission of this parasite in Mexico. The results of this survey were compared with those obtained nearly 50 yr ago from a survey of birds from the same general area; prevalence in both samples was similar, despite the change to a more agricultural environment over this period.

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The blood parasites of 15,574 birds representing 266 species of 43 families from primarily three areas in Säo Paulo State, Brazil were examined for haematozoa. Only 1240 (8.0% of 121 species fo 32 families were infected with blood parasites. This prevalence was similar to that reported in a previous study. Species of Haemoproteus were the most commonly encountered haematozoans (38.9%), followed by microfilaria (30.7%), Trypanosoma (13.7%), Plasmodium (7.5%) and Leucocytozoon (0.8%). Prevalence of parasitism was significantly different between the three major areas sampled. It was shown that this was due in part to differences in the avifaunas at both the familial and species levels. Prevalence varied markedly in only one of the 10 years of the study. Monthly fluctuations in prevalence were largely due to changes in relative proportions of highlytion of both. Prevalences of both microfilaria and Trypanosoma were higher than reported for any other similar survey in the world

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Examination of the hapantotype of Spirogregarina fusiformis Wood and Herman, 1943, indicates that this organism is not an avian haematozoon as described but is the diatom Cylindrotheca gracilis (Brebbison) Grunow.

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Body masses of 3,739 birds representing immature and adult males and females of 15 species of passeriforms (both uninfected and infected with Haemoproteus spp. and Leucocytozoon spp.) were compared. There was some interaction among year, month and area of capture for several host species, but there was no discernible effect of either parasite genus on body mass. There were no effects due to high intensity parasitemia for eight host species examined. Either parasitism does not cause loss of body mass, or the techniques used were too insensitive to separate effects of parasitism from other natural causes.

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A total of 222 birds, captive or free-flying in the Oklahoma City Zoo, were examined for blood parasites; 31 (14%) harbored Haemoproteus and/or Leucocytozoon. While 21% of the indigenous avifauna were infected, only 8% of the exotic bird species harbored haemoproteids and these parasites were also exotic to North America. There was no evidence to indicate that exotic infections were transmitted to native birds or vice versa.

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Information on the blood parasites occurring in 3,866 anatids of 14 species collected from five locations in Alberta and Saskatchewan during 1976-80 is summarized. An overall prevalence of 26% with avian hematozoa was recorded. Leucocytozoon simondi was the most frequently encountered parasite, occurring in 17% of the ducks; Haemoproteus nettionis was observed in 11% of the birds while Plasmodium circumflexum and microfilariae (probably of Splendidofilaria fallisensis) occurred in only 2% and less than 1% of the sample respectively. Overall prevalence of infection in both immatures and adults was similar, although the sample was heavily biased in favor of the immature age class. While the overall prevalence of L. simondi was similar in both age classes, H. nettionis occurred twice as frequently in the adult birds. Infection prevalences of birds in the five geographic areas sampled were different and these differences are discussed. Prevalences also differed from year to year in birds from the various areas and these differences are attributed, in part, to the water levels encountered each year. Leucocytozoon simondi is considered a potentially limiting factor for waterfowl production in some areas of northern Alberta and Saskatchewan.

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A total of 1650 birds of 56 species representing 21 families (primarily Passeriformes), was examined for blood parasites in the Lorraine region of France. Only 120 (7.3%) birds were infected, with members of the Paridae, Sylviidae and Turdidae the most frequently parasitized. Haemoproteids were the most commonly encountered parasites followed by the leucocytozoids. Other avian hematozoon genera were uncommon. Prevalence of parasitism was closely similar each year over a three-year period. Immature birds were first noted to be infected with Leucocytozoon in mid-June, suggesting transmission in late May to early June. Haemoproteids were first noted in immature birds in early July, suggesting transmission in mid-June. A review of the literature indicates that the prevalence of parasitism by avian blood parasites has decreased in western Europe since the turn of the century and is currently much lower than the prevalence encountered in Scandinavia, central Russia and eastern North America.

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