High prevalence and diversity of blood parasites of passerine birds in Southern Turkmenistan

Thirty nine specimens of passerine birds belonging to 19 species and eight families were investigated by blood smear technique in four localities of Southern Turkmenistan in 3-18 August 1991. The overall prevalence of infection was 59%. Protists from the orders Haemosporida (genera Haemoproteus, Plasmodium, Leucocytozoon), Kinetoplastida (Trypanosoma), and Adeleida (Hepatozoon), as well as Microfilaria were found. Haemoproteids (the prevalence of infection is 44%), leucocytozoids (23%), malarial parasites (13%) and trypanosomes (13%) were most frequently recorded. Only low chronic infections (< 1% of infected cells for the great majority of intracellular parasites, and a few trypanosomes and Microfilaria in each blood smear) were seen. Haemoproteus belopolskyi, H. balmorali, H. dolniki, H. magnus, H. minutus, H. fringillae, H. majoris, Leucocytozoon dubreuili, and Trypanosoma avium were recorded for the first time in Turkmenistan. The former five above-mentioned species of haemoproteids are new records for the fauna of Middle Asia. Gametocytes of leucocytozoids in fusiform host cells were found for the first time in passerine birds in the Holarctic. The host is Parus bokharensis. Due to the wide distribution and the opportunity to collect a large parasitological material using harmless for hosts methods, bird haemosporidian parasites can be used as convenient models for ecological and evolutionary biology studies in South Turkmenistan. The heavily infected Orphean Warbler Sylvia hortensis is an especially convenient host for such purposes.     

Haematozoa of East African birds: III. Three years' observations on the blood parasites of birds from Ngulia

A survey of blood parasites of birds from Ngulia in Kenya was carried out during the period November-December for the years 1973–1975. A total of 468 birds was examined of which 179 (38.2%) were infected with one or more parasites. Together with a re-examination of material from previous surveys for taxonomic purposes, the following species were identified; Haemoproteus anthi, H. centropi, H. columbae, H. coraciae, H. fallisi, H. fringillae, H. lanii, H. morneti, H. orizivorae, H. sanguinis, H. tendeiroi, H. zosteropsi, Leucocytozoon brimonti, L. coccyzus, L. dinizi, L. dub-reuili, L. eurystomi, L. fringillinarum, L. marchouxi, Plasmodium relictum, P. rouxi, P. vaughani, Trypanosoma everetti, T. mayae, T. pycnonoti and Babesiu rustica. Unidentified species of haemogregarines, Aegyptianella, Rickettsia and microfilaria were also observed. The significance of migrant birds as reservoirs of infection, together with the probable seasonality of patent infections in the resident population is discussed.     

Interspecific variability of prevalence in blood parasites of adult passerine birds during the breeding season in Alaska

Blood parasite prevalence based on microscopic examination of stained blood smears was determined in adults of 11 passerine bird species sampled during their breeding season (May and June 1997-98) in interior Alaska (USA). These species included primarily Nearctic migratory species such as the dark-eyed junco (Junco hyemalis) and neotropical migratory species such as the blackpoll warbler (Dendroica striata), alder flycatcher (Empidonax alnorum), Swainson's thrush (Catharus ustulatus), northern waterthrush (Seiurus noveboracensis), and bank swallow (Riparia riparia) as well as one long-distance palearctic migrant, the arctic warbler (Phylloscopus borealis). The more prevalent parasites were Leucocytozoon dubreuili (73% of the sampled turdinids), L. fringillinarum (42% of the sampled fringillids and parulids), and Trypanosoma avium (39% of the sampled hosts). Other parasites (H. fallisi: 18% of the sampled turdinids; Haemoproteus paruli: 14% of the sampled parulids; H. fringillae: 5% of the sampled fringillids; microfilariae: 4% of the sampled hosts) were observed less frequently. Plasmodium vaughani was found only in two yellow warblers (Dendroica petechia). Overall parasite prevalence varied between 0% in the alder flycatcher to >80% in Swainson's thrush, arctic warbler, and Townsend's warbler (Dendroica townsendi). Prevalence of various hematozoa also was bird species-dependent. No relationship was observed between prevalence and either foraging (aerial versus trees/shrubs) or nesting habits (ground versus arboreal) or general location of the wintering area of the different species examined. Prevalence also was unrelated to average dates of arrival on breeding grounds and, therefore, to potential duration of exposure to local insect vectors before capture. Differences in blood parasite prevalence among species breeding in a same region and in the same type of habitat may result from differences in host specificity such as immunological resistance to infection or blood meal preference by potential vectors and/or in behavioral adjustments/physiological traits that alter exposure to vectors.     

The sensitivity of microscopy and PCR-based detection methods affecting estimates of prevalence of blood parasites in birds

Inferences about the evolution of host-parasitic relationships are often made based on the prevalence of avian malaria, which is usually estimated in a large sample of birds using either microscopic or molecular screening of blood samples. However, different techniques often have variable accuracy; thus, screening methodology can raise issues about statistical bias if method sensitivity varies systematically across parasites or hosts. To examine this possibility, published information was collected on the prevalence of species in 4 genera of avian blood parasites ( Plasmodium, Haemoproteus, Leucocytozoon, and Trypanosoma) from various sources that used different tools. The data were tested to determine if the application of different methods provided different estimates for the same hosts. In these comparisons between the main methodologies, the PCR-based molecular methods were generally found to provide higher estimates for Plasmodium spp. prevalence than microscopic tools, while there was no significant tendency for such a trend in species of Haemoproteus and Leucocytozoon. When analyzing intraspecific variance of prevalence within molecular studies, some studies provided consistently higher estimates for Haemoproteus spp. prevalence than others, indicating that differences between studies can affect detected estimates. Within microscopic studies, surveys that examined more microscopic fields were more likely to report higher prevalence for Plasmodium spp. than those relying on fewer microscopic fields. Consequently, studies making comparisons across parasite genera and/or host species from different sources need to consider several types of bias originating from variation in method sensitivity.     

Prevalence of blood parasites in European passeriform birds

Variation in the prevalence of blood parasites among species of birds has been used to test hypotheses about the effects of sexual selection and parental investment on disease resistance, and how vector abundance influences infection. However, the factors causing this variation are still poorly understood. We assessed the statistical effects of biogeographic, plumage-related and life-history traits on the prevalence of the blood parasites Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma in European passerine birds. Most of the variation in parasite prevalence occurred at low taxonomic levels. Brighter male plumage and greater host body mass were associated with higher prevalence, explaining 32% of the total variation. Male plumage brightness remained a significant factor when we controlled for phylogenetic effects. These relationships were driven primarily by simuliid-transmitted parasites (Leucocytozoon, Trypanosoma), which were more frequent in species with northern distributions. Host species with greater maximum longevity and shorter nestling periods had higher prevalences of Plasmodium; however, the effect was not stable after controlling for phylogeny using pairwise contrasts. Coevolution between hosts and parasites appears to create temporal and spatial variation that disconnects haematozoan prevalence from evolutionarily conservative life-history traits while creating some positive associations with traits that are phylogenetically labile. Clearly, ecologists should be cautious in relating patterns of variation in haematozoan prevalence to particular host traits.     

State and evolution of the African rainforests between 1990 and 2010

This paper presents a map of Africa''s rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images—imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr⁻¹ for the period 1990–2000 and 0.14% yr⁻¹ for the period 2000–2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are also identified as strong underlying causes of deforestation in this study.     

Further observations on the blood parasites of birds in Uganda

Birds from three National Parks (Bwindi Impenetrable, Kibale, and Queen Elizabeth) in western Uganda were surveyed during the dry season in July 2003 and investigated for hematozoa by microscopic examination of stained blood films. Of 307 birds examined, representing 68 species of 15 families and four orders, 61.9% were found to be infected with blood parasites. Species of Haemoproteus (15.3% prevalence), Plasmodium (20.5%), Leucocytozoon (40.1%), Trypanosoma (11.4%), Hepatozoon (2.6%), Atoxoplasma (0.3%), and microfilariae (3.9%) were recorded. Except for Haemoproteus spp. infections, the overall prevalence of hematozoa belonging to all genera was significantly higher in this study than was previously reported in Uganda. Thirty-six species of birds were examined for blood parasites for the first time and 112 new host-parasite associations were identified. Eighty-one were at the generic and 31 at the specific level of the hematozoa. Hepatozoon and Atoxoplasma spp. were detected for the first time in Uganda.     

Haemosporidian blood parasites in European birds of prey and owls

Avian blood parasites have been intensively studied using morphological methods with limited information on their host specificity and species taxonomic status. Now the analysis of gene sequences, especially the mitochondrial cytochrome b gene of the avian haemosporidian species of Haemoproteus, Plasmodium, and Leucocytozoon, offers a new tool to review the parasite specificity and status. By comparing morphological and genetic techniques, we observed nearly the same overall prevalence of haemosporidian parasites by microscopy (19.8%) and polymerase chain reaction (PCR) (21.8%) analyses. However, in contrast to the single valid Leucocytozoon species (L. toddi) in the Falconiformes we detected 4 clearly distinctive strains by PCR screening. In the Strigiformes, where the only valid Leucocytozoon species is L. danilewskyi, we detected 3 genetically different strains of Leucocytozoon spp. Two strains of Haemoproteus spp. were detected in the birds of prey and owls examined, whereas the strain found in the tawny owl belonged to the morphospecies Haemoproteus noctuae. Three Plasmodium spp. strains that had already been found in Passeriformes were also detected in the birds of prey and owls examined here, supporting previous findings indicating a broad and nonspecific host spectrum bridging different bird orders.     

Additional observations on the blood parasites of Ugandan birds.

One thousand and seventy-six birds of 26 families and 127 species were examined for hemoprotozoa; 404 birds (37%) of 41 species representing 17 families harbored one or more blood parasites. Most parasites were species of Haemoproteus which represented 95% of all parasitic infections detected. Prevalence of blood parasites in birds collected from four areas over a period of six years was relatively stable.     

Additional observations on blood parasites of birds in Costa Rica

Birds from the Area de Conservacion Guanacaste in northwestern Costa Rica were surveyed for blood parasites in June 2001 and December 2001-January 2002. Of 354 birds examined, representing 141 species of 35 families and 15 orders, 44 (12.4%) were infected with blood parasites. Species of Haemoproteus (4.8% prevalence), Plasmodium (0.6%), Leucocytozoon (0.3%), Trypanosoma (2.0%), and microfilariae (7.6%) were recorded. Twelve species of birds in this survey were examined for blood parasites for the first time. Several new host-parasite associations were identified.     

Influence of blood parasites on the body mass of passeriform birds

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.     

Migratory birds have higher prevalence and richness of avian haemosporidian parasites than residents

Individuals of migratory species may be more likely to become infected by parasites because they cross different regions along their route, thereby being exposed to a wider range of parasites during their annual cycle. Conversely, migration may have a protective effect since migratory behaviour allows hosts to escape environments presenting a high risk of infection. Haemosporidians are one of the best studied, most prevalent and diverse groups of avian parasites, however the impact of avian host migration on infection by these parasites remains controversial. We tested whether migratory behaviour influenced the prevalence and richness of avian haemosporidian parasites among South American birds. We used a dataset comprising ~ 11,000 bird blood samples representing 260 bird species from 63 localities and Bayesian multi-level models to test the impact of migratory behaviour on prevalence and lineage richness of two avian haemosporidian genera (Plasmodium and Haemoproteus). We found that fully migratory species present higher parasite prevalence and higher richness of haemosporidian lineages. However, we found no difference between migratory and non-migratory species when evaluating prevalence separately for Plasmodium and Haemoproteus, or for the richness of Plasmodium lineages. Nevertheless, our results indicate that migratory behaviour is associated with an infection cost, namely a higher prevalence and greater variety of haemosporidian parasites.     

Migratory behavior of birds affects their coevolutionary relationship with blood parasites

Host traits, such as migratory behavior, could facilitate the dispersal of disease-causing parasites, potentially leading to the transfer of infections both across geographic areas and between host species. There is, however, little quantitative information on whether variation in such host attributes does indeed affect the evolutionary outcome of host-parasite associations. Here, we employ Leucocytozoon blood parasites of birds, a group of parasites closely related to avian malaria, to study host-parasite coevolution in relation to host behavior using a phylogenetic comparative approach. We reconstruct the molecular phylogenies of both the hosts and parasites and use cophylogenetic tools to assess whether each host-parasite association contributes significantly to the overall congruence between the two phylogenies. We find evidence for a significant fit between host and parasite phylogenies in this system, but show that this is due only to associations between nonmigrant parasites and their hosts. We also show that migrant bird species harbor a greater genetic diversity of parasites compared with nonmigrant species. Taken together, these results suggest that the migratory habits of birds could influence their coevolutionary relationship with their parasites, and that consideration of host traits is important in predicting the outcome of coevolutionary interactions.