Diversity Of Haemosporidian Parasites Research Articles

Individual variation in feather corticosterone levels and its influence on haemosporidian infection in a Neotropical bird

Corticosterone (CORT) is the main glucocorticoid hormone of amphibians, reptiles, birds and some mammals. This hormone may have evolved as an adaptive metabolic mechanism, in part because increased concentrations ofCORTare essential for individuals to manage energy resources and thus cope with negative perturbations such as predation and storms. The benefits ofCORTare offset by costs, because elevated levels can suppress inflammatory responses of individuals, making them more susceptible to parasites and pathogens. In this study, we investigated the relationships between featherCORTlevels, infection status and diversity of haemosporidian parasites in the Blue‐crowned ManakinLepidothrix coronata, considering possible effects related to the sex and age of individuals. We predicted higher levels of featherCORTin infected individuals. We observed that featherCORTlevels were similar among individuals of different sexes and ages. Although haemosporidian infection status did not vary among sexes, occurrence probability was higher among younger individuals, which may indicate that the less developed immune system of these individuals makes them more susceptible to avian malaria. Contrary to expectations, we found that featherCORTlevels were not associated with the infection status and diversity of haemosporidian parasites. That haemosporidian occurrence probability does not increase with elevated featherCORTlevels suggests that individuals are not immunosuppressed by elevated levels of this hormone, at least to the extent that featherCORTtruly reflects individual differences in the level of this hormone.

Spatial distribution, prevalence and diversity of haemosporidians in the rufous-collared sparrow, Zonotrichia capensis

BackgroundParasite prevalence and diversity are determined by the distribution of hosts and vectors and by the interplay among a suite of environmental factors. Distributions of parasite lineages vary based on host susceptibility and geographical barriers. Hemoparasites of the genera Haemoproteus and Plasmodium have wide distributions, and high prevalence and genetic diversity within perching birds (Order Passeriformes). The rufous-collared sparrow (Zonotrichia capensis) is widely distributed in Central and South America across an immense diversity of environments from sea level to more than 4000 meters above sea level. It therefore provides an excellent model to investigate whether altitudinal and latitudinal gradients influence the distribution, prevalence and diversity of haemosporidian parasites, their population structure and the biogeographical boundaries of distinct parasite lineages.ResultsWe assembled samples from 1317 rufous-collared sparrows spanning 75 locales from across Central and South America (between 9.5°N and 54°S; 10–4655 meters above sea level). We used DNA sequence data from a fragment of the mitochondrial cytochrome b gene (cytb) of Haemoproteus and Plasmodium from 325 positive samples and found prevalences of 22 and 3%, respectively. Haemoproteus exhibited a higher prevalence than Plasmodium but with comparatively lower genetic diversity. We detected a relationship of Plasmodium and Haemoproteus prevalence with altitude and latitude; however, altitude and latitude did not influence parasite diversity.ConclusionsParasite lineages showed a phylogeographical boundary coincident with the Andes Mountains, although we also observed a north-south disjunction in Peru for Haemoproteus. Haemosporidian distribution was not homogeneous but differed based on latitude and altitude. This is most probably due to environmental factors that have influenced both vector distribution and abundance, as well as parasite development. Our study provides key insights on the distribution of haemoparasite lineages and parasite dynamics within hosts.

High prevalence and narrow host range of haemosporidian parasites in Godlewski's bunting (Emberiza godlewskii) in northern China

Avian haemosporidian parasites are highly diverse, have a wide range of host specificity, and reveal diverse compatibility with regard to host range and geographical distribution. Therefore, understanding haemosporidian parasite diversity in different host species and different regions is crucial. A survey of the haemosporidian parasite in 186 Godlewski's buntings in Beijing was conducted to compare infection patterns between Godlewski's bunting, local passerines and the global avian host. High prevalence (88.7%) was found in the bunting and displayed annual stability during the research period. Most of the infections were caused by four dominant lineages, three of which were clustered with lineages of morphological species. In comparison with other lineages in local passerines, the dominant lineages were relative specialists. The findings suggest that the compatibility of dominant lineages in the bunting hosts may play important roles in high haemosporidian prevalence, and the narrow host range of the dominant lineages may be due to coevolution between the parasites and host species.

Prevalence and diversity of haemosporidian parasites in the yellow-rumped warbler hybrid zone.

Parasites can play a role in speciation, by exerting different selection pressures on different host lineages, leading to reproductive barriers in regions of possible interbreeding. Hybrid zones therefore offer an ideal system to study the effect of parasites on speciation. Here, we study a hybrid zone in the foothills of the Rocky Mountains where two yellow‐rumped warbler subspecies, Setophaga coronata coronata and S. c. auduboni, interbreed. There is partial reproductive isolation between them, but no evidence of strong assortative mating within the hybrid zone, suggesting the existence of a postzygotic selection against hybrids. Here, we test whether haemosporidian parasites might play a role in selecting against hybrids between S. c. coronata and S. c. auduboni. We screened birds from five transects across the hybrid zone for three phylogenetic groupings of avian haemosporidians Plasmodium, Haemoproteus and Leucocytozoon parasites and quantified intensity of infection. Contrary to our prediction, hybrids did not have higher haemosporidian parasite prevalence. Variation in Haemoproteus prevalence was best explained by an interaction between a birds’ hybrid index and elevation, while the probability of infection with Leucocytozoon parasites was only influenced by elevation. We also found no significant difference in the diversity of haemosporidian lineages between the warbler subspecies and their hybrids. Finally, intensity of infection by Haemoproteus increased significantly with elevation, but was not significantly linked to birds’ hybrid index. In conclusion, our data suggest that haemosporidian parasites do not seem to play a major role in selecting against hybrids in this system.

Variation in malaria infection and immune defence in invasive and endemic house sparrows

AbstractBiological invasions by exotic species impose substantial ecological, economic and social costs worldwide, being a major threat to biodiversity conservation. Because not all individuals introduced in the new environments become successful invaders, the identification of factors underlying variation in invasion success would be essential for evaluating invasion risk. Here, we test several host–parasite hypotheses accounting for invasion success of house sparrows Passer domesticus in Peru. According to the Enemy Release Hypothesis, invasive house sparrows from Peru showed lower prevalence and genetic diversity of haemosporidian parasites than sparrows from their natural range (Spain), indicating that the release from their natural parasites may have favoured the spread of sparrows in the new area of occurrence. We also showed that Peruvian sparrows had larger uropygial glands and higher anti‐bacterial activity in its secretion than sparrows from Spain, suggesting selection in defensive mechanisms driven by pathogens when colonizing new environments. Finally, we showed that uninfected sparrows had larger uropygial glands and higher anti‐bacterial activity than malaria‐infected house sparrows, implying that uropygial gland secretions may act as a defensive mechanism against haemosporidian infections. Alternatively, a condition‐dependent trade‐off exists between synthesis of uropygial secretion and immune response. These outcomes provide essential information for identifying potential invaders and designing interventions.

Host species, and not environment, predicts variation in blood parasite prevalence, distribution, and diversity along a humidity gradient in northern South America.

Environmental factors strongly influence the ecology and evolution of vector‐borne infectious diseases. However, our understanding of the influence of climatic variation on host–parasite interactions in tropical systems is rudimentary. We studied five species of birds and their haemosporidian parasites (Plasmodium and Haemoproteus) at 16 sampling sites to understand how environmental heterogeneity influences patterns of parasite prevalence, distribution, and diversity across a marked gradient in water availability in northern South America. We used molecular methods to screen for parasite infections and to identify parasite lineages. To characterize spatial heterogeneity in water availability, we used weather‐station and remotely sensed climate data. We estimated parasite prevalence while accounting for spatial autocorrelation, and used a model selection approach to determine the effect of variables related to water availability and host species on prevalence. The prevalence, distribution, and lineage diversity of haemosporidian parasites varied among localities and host species, but we found no support for the hypothesis that the prevalence and diversity of parasites increase with increasing water availability. Host species and host × climate interactions had stronger effects on infection prevalence, and parasite lineages were strongly associated with particular host species. Because climatic variables had little effect on the overall prevalence and lineage diversity of haemosporidian parasites across study sites, our results suggest that independent host–parasite dynamics may influence patterns in parasitism in environmentally heterogeneous landscapes.

First Record of Leucocytozoon (Haemosporida: Leucocytozoidae) in Amazonia: Evidence for Rarity in Neotropical Lowlands or Lack of Sampling for This Parasite Genus?

Birds harbor an astonishing diversity of haemosporidian parasites belonging to the genera Haemoproteus, Leucocytozoon, and Plasmodium. Currently there are more than 250 morphologically described avian haemosporidian species and 2,828 unique lineages found in virtually all avian clades and zoogeographic regions, except for Antarctica. Our report is based on PCR and microscopic screening of 1,302 individual avian samples from Brazil to detect the underrepresented genus Leucocytozoon. This survey primarily focuses on passerine birds collected from Amazonia, the Atlantic Rain Forest, and Pantanal. We also summarize studies conducted in Brazil that report haemosporidian prevalence using both microscopy and molecular tools and present for the first time a record of Leucocytozoon infecting an avian host population in Amazonia. Based on our findings, we suggest that high average temperatures may be constraining both the distribution and diversity of Leucocytozoon in lowland tropical South America.

Carrion crows (Corvus corone) of southwest Germany: important hosts for haemosporidian parasites

BackgroundAvian malaria parasites (Plasmodium spp.) and other Haemosporida (Haemoproteus and Leucocytozoon spp.) form a diverse group of vector-transmitted blood parasites that are abundant in many bird families. Recent studies have suggested that corvids may be an important host for Plasmodium spp. and Leucocytozoon spp.MethodsTo investigate the diversity of Haemosporida of resident carrion crows (Corvus corone) and Eurasian Magpies (Pica pica) in southwest Germany, 100 liver samples of corvids were examined using a nested PCR method to amplify a 1063 bp fragment of the haemosporidian mitochondrial cytochrome b gene. The phylogenetic relationship of parasite lineages obtained from these birds was inferred.ResultsHaemosporidian DNA was detected in 85 carrion crows (89.5%) and in all five Eurasian Magpies. The most abundant parasite genus was Leucocytozoon with a prevalence of 85.3% (n = 95). 65.3% of the samples (n = 62) contained multiple infections. Thirteen haemosporidian lineages were isolated from the corvid samples. Female carrion crows were more likely infected with haemosporidian parasites than males.DiscussionThis study provides the first insight into the diversity of haemosporidian parasites of corvids in Germany. Very high prevalences were found and based on the applied diagnostic method also a high amount of multiple infections could be detected. Due to the high diversity of haemosporidian parasites found in corvids, they seem to be excellent model organisms to test species deliminations in haemosporidian parasites.

Diversity and prevalence of hemoparasites of wading birds in southern Florida, USA.

Relatively few studies on hemoparasites have been conducted on wading birds in the families Ardeidae and Threskiornithidae (order Pelecaniformes), especially in the United States. In this study, we obtained baseline data on the prevalence and genetic diversity of haemosporidian parasites in wading birds opportunistically sampled from southern Florida, USA. We detected blood parasites in White Ibis (Eudocimus albus), Glossy Ibis (Plegadis falcinellus), Green Heron (Butorides virescens), and Roseate Spoonbill (Platalea ajaja) with several novel host-parasite relationships. Infected birds had low parasitemias (average 0.77%, range 0–4%) suggesting that infections were chronic. Despite the low sample sizes for several of our sampled species, these data highlight the diversity of parasites in this understudied group of birds and suggest that additional studies are needed to investigate the potential impacts of these parasites on their health, especially since southern Florida is becoming increasingly urbanized which can alter parasite transmission or host susceptibility.

Haemosporidian Parasites of Reptiles and Birds from Gabon, Central Africa.

Haemosporidian parasites are protozoans that infect many different vertebrate hosts. Re-examination of the diversity of haemosporidian parasites, using molecular tools, has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting some species of reptile and birds living in the forests of Gabon, Central Africa, by analyzing a collection of 128 samples of reptiles and birds. We found that samples from 2 tortoise species (Pelusios castaneus and Kinixys erosa) and 3 bird species (Turtur afer, Ceratogymna atrata, and Agelastes niger) were infected by Haemocystidium spp. and Parahaemoproteus spp., respectively. From an ecological point of view, these lineages of parasites do not show host specificity because we have found them in several host species (2 tortoise and 3 bird species) that come from different areas of Gabon forest which are infected with these parasites. Also, our phylogenetic analyses revealed that the obtained lineages are related to isolates from other continents found in the same groups of vertebrates. Thus, our results show that haemosporidian parasites are also infecting central African vertebrates and that new lineages of these parasites are circulating in wild animals of the Gabon forest.

Estimating prevalence of avian haemosporidians in natural populations: a comparative study on screening protocols

BackgroundBirds harbour an astonishing diversity of haemosporidian parasites. Renewed interest in avian haemosporidians as a model system has placed a greater emphasis on the development of screening protocols to estimate parasite prevalence and diversity. Prevalence estimates are often based on the molecular or blood-smear microscopy techniques. However, variation in diagnostic sensitivity among screening methodologies represents a potential source of bias that may lead to erroneous inference in comparisons of prevalence across studies. Here, we analyzed a suite of blood samples for the presence of parasites using four diagnostic tools and compared method-specific estimates of detection probability to assess the relative performance of screening strategies.MethodsWe screened a total of 394 bird blood samples collected in India (n = 203) and Sweden (n = 191) for the combined presence of Plasmodium, Haemoproteus and Leucocytozoon with three PCR assays: (i) qPCR; (ii) restriction enzyme-based assay; and (iii) nested protocol. In addition, we examined blood smears for estimates of parasite intensity which was further screened using qPCR method to evaluate if parasite intensity shows a relationship with qPCR (Ct values). Furthermore, we used single infected samples from parasite intensities: low, medium, high, very high to establish the reproducibility in qPCR.ResultsFor the combined data sets from India and Sweden, detection probability for submicroscopic and low intensity infections was highest for the qPCR method, followed by the nested protocol and the restriction enzyme-based assay. For high parasite intensities, the qPCR had high PCR reproducibility, with three out of three PCR replicates being positive and with consistent Ct values across all tenfold dilution series. For parasite intensities at very low and submicroscopic samples, the qPCR was reproducible in one out of the three replicates. The intensity of parasitemia estimated from smears showed inverse relationship with Ct values in both the Indian and Swedish data sets.ConclusionsOur study highlights the importance of accounting for methodological issues to better estimate infection in parasitological studies and illustrates how a wider deployment of diagnostic tools combined with statistical approaches is needed for each study, in order to provide adequate insight into the most appropriate approach to avoid erroneous inferences.

Haemosporidian blood parasite diversity and prevalence in the semi-collared flycatcher (Ficedula semitorquata) from the eastern Balkans

We present the first survey on prevalence and diversity of haemosporidian parasites of the genera Plasmodium and Haemoproteus in a poorly studied migratory passerine, the semi-collared flycatcher (Ficedula semitorquata). In total, 110 individuals were sampled during two breeding seasons in Eastern Bulgaria. We collected both blood samples for PCR identification and blood films for microscopic identification of haemosporidians. We found six distinctive parasite cyt b lineages present in the blood of the semi-collared flycatcher (three Haemoproteus and three Plasmodium). Two of the lineages, i.e. pWW3 of Plasmodium sp. and hCCF2 of Haemoproteus sp., are recorded for the first time in the family Muscicapidae. The overall prevalence ranged between 12.2 and 15.9% and we did not find co-infections. We hypothesize that the low prevalence of haemosporidians in this species might be linked to its small population size and relatively restricted geographical range.

Haemosporidian parasite infections in grouse and ptarmigan: Prevalence and genetic diversity of blood parasites in resident Alaskan birds.

Projections related to future climate warming indicate the potential for an increase in the distribution and prevalence of blood parasites in northern regions. However, baseline data are lacking for resident avian host species in Alaska. Grouse and ptarmigan occupy a diverse range of habitat types throughout the northern hemisphere and are among the most well-known and important native game birds in North America. Information regarding the prevalence and diversity of haemosporidian parasites in tetraonid species is limited, with few recent studies and an almost complete lack of genetic data. To better understand the genetic diversity of haemosporidian parasites in Alaskan tetraonids and to determine current patterns of geographic range and host specificity, we used molecular methods to screen 459 tissue samples collected from grouse and ptarmigan species across multiple regions of Alaska for infection by Leucocytozoon, Haemoproteus, and Plasmodium blood parasites. Infections were detected in 342 individuals, with overall apparent prevalence of 53% for Leucocytozoon, 21% for Haemoproteus, and 9% for Plasmodium. Parasite prevalence varied by region, with different patterns observed between species groups (grouse versus ptarmigan). Leucocytozoon was more common in ptarmigan, whereas Haemoproteus was more common in grouse. We detected Plasmodium infections in grouse only. Analysis of haemosporidian mitochondrial DNA cytochrome b sequences revealed 23 unique parasite haplotypes, several of which were identical to lineages previously detected in other avian hosts. Phylogenetic analysis showed close relationships between haplotypes from our study and those identified in Alaskan waterfowl for Haemoproteus and Plasmodium parasites. In contrast, Leucocytozoon lineages were structured strongly by host family. Our results provide some of the first genetic data for haemosporidians in grouse and ptarmigan species, and provide an initial baseline on the prevalence and diversity of blood parasites in a group of northern host species.

Differential prevalence and diversity of haemosporidian parasites in two sympatric closely related non-migratory passerines.

Haemosporidian parasites infecting birds show distinct heterogeneity in their distribution among host species. However, despite numerous studies on the prevalence and diversity of parasite communities across species, very little is known on patterns of differences between them. Such data is lacking because up to date the majority of studies explored the patterns of variation in infections in different years, different time of sampling within a year or a breeding cycle, different study sites or was based on a small sample size, all of which may affect the estimates of prevalence and parasite diversity. Here, the prevalence, richness and diversity of haemosporidian parasites from the genera Plasmodium and Haemoproteus were studied in two closely related non-migratory hole-nesting passerines: Great Tits and Blue Tits. Birds were sampled in sympatrically breeding populations during two seasons at the same stage of their breeding cycle - late nestling care. Great Tits were more prevalently infected with Plasmodium and Haemoproteus parasites (97·1 vs 71·2%), harboured a higher proportion of multiple infections (26·2 vs 3·2%) and had a more diverse parasite community (11 vs 5 parasite lineages) than Blue Tits. Observed differences between two host species are discussed with reference to their breeding densities and immunological and behavioural characteristics.

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon, Central Africa.

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.

Genetic diversity of avian haemosporidians in Malaysia: Cytochrome b lineages of the genera Plasmodium and Haemoproteus (Haemosporida) from Selangor

The knowledge of the diversity of haemosporidian parasites is of primary importance as their representatives include agents of bird malaria. We investigated the occurrence of Haemoproteus spp. and Plasmodium spp. in bird populations from a single locality in the State of Selangor, Peninsular Malaysia, and report on the parasite prevalence of the two genera. A combination of methods (molecular and morphological) was used for detecting these parasites. Seventy-nine bird individuals were caught using mist-nets in July and August 2010 at Gombak Field Station of the University of Malaya, Kuala Lumpur. In total, 23 birds were identified as positive for Haemoproteus or Plasmodium infection and one individual was recognized as carrying mixed infection. The total prevalence of haemosporidians in the collected samples was 30.3%. Infections with parasites of the genus Haemoproteus were predominant compared to those of the genus Plasmodium. In total, 10 new cyt b lineages of Haemoproteus spp. and 3 new cyt b lineages of Plasmodium spp. were recorded in this study. From all recorded haemosporidian lineages (16 in total), 3 were known from previous studies – hCOLL2, hYWT2 and pNILSUN1. Two of them are linked with their corresponding morphospecies – Haemoproteus pallidus (COLL2) and Haemoproteus motacillae (YWT2). The morphological analysis in the present study confirmed the results obtained by the PCR method relative to prevalence, with 25.3% total prevalence of Haemoproteus and Plasmodium parasites. The intensities of infection varied between 0.01% and 19%. Most infections were light, with intensities below 0.1%. The present study is the first molecular survey of the protozoan blood parasites of the order Haemosporida recorded in Malaysia.

Description of the first cryptic avian malaria parasite, Plasmodium homocircumflexum n. sp., with experimental data on its virulence and development in avian hosts and mosquitoes

For over 100years studies on avian haemosporidian parasite species have relied on similarities in their morphology to establish a species concept. Some exceptional cases have also included information about the life cycle and sporogonic development. More than 50 avian Plasmodium spp. have now been described. However, PCR-based studies show a much broader diversity of haemosporidian parasites, indicating the possible existence of a diverse group of cryptic species. In the present study, using both similarity and phylogenetic species definition concepts, we believe that we report the first characterised cryptic speciation case of an avian Plasmodium parasite. We used sequence information on the mitochondrial cytochrome b gene and constructed phylogenies of identified Plasmodium spp. to define their position in the phylogenetic tree. After analysis of blood stages, the morphology of the parasite was shown to be identical to Plasmodium circumflexum. However, the geographic distribution of the new parasite, the phylogenetic information, as well as patterns of development of infection, indicate that this parasite differs from P. circumflexum. Plasmodium homocircumflexum n. sp. was described based on information about genetic differences from described lineages, phylogenetic position and biological characters. This parasite develops parasitemia in experimentally infected birds – the domestic canary Serinus canaria domestica, siskin Carduelis spinus and crossbill Loxia curvirostra. Anaemia caused by high parasitemia, as well as cerebral paralysis caused by exoerythrocytic stages in the brain, are the main reasons for mortality. Exoerythrocytic stages also form in other organs (heart, kidneys, liver, lungs, spleen, intestines and pectoral muscles). DNA amplification was unsuccessful from faecal samples of heavily infected birds. The sporogonic development initiates, but is abortive, at the oocyst stage in two common European mosquito species, Culex pipiens pipiens (forms pipiens and molestus) and Aedes vexans. Vectors of this Plasmodium sp. remain unknown.

Diversity of avian haemosporidians in arid zones of northern Venezuela

Arid zones of northern Venezuela are represented by isolated areas, important from an ornithological and ecological perspective due to the occurrence of restricted-range species of birds. We analysed the prevalence and molecular diversity of haemosporidian parasites of wild birds in this region by screening 527 individuals (11 families and 20 species) for parasite mitochondrial DNA. The overall prevalence of parasites was 41%, representing 17 mitochondrial lineages: 7 of Plasmodium and 10 of Haemoproteus. Two parasite lineages occurred in both the eastern and western regions infecting a single host species, Mimus gilvus. These lineages are also present throughout northern and central Venezuela in a variety of arid and mesic habitats. Some lineages found in this study in northern Venezuela have also been observed in different localities in the Americas, including the West Indies. In spite of the widespread distributions of some of the parasite lineages found in northern Venezuela, several, including some that are relatively common (e.g. Ven05 and Ven06), have not been reported from elsewhere. Additional studies are needed to characterize the host and geographical distribution of avian malaria parasite lineages, which will provide a better understanding of the influence of landscape, vector abundance and diversity, and host identity on haemosporidian parasite diversity and prevalence.

Diversity, Loss, and Gain of Malaria Parasites in a Globally Invasive Bird

Invasive species can displace natives, and thus identifying the traits that make aliens successful is crucial for predicting and preventing biodiversity loss. Pathogens may play an important role in the invasive process, facilitating colonization of their hosts in new continents and islands. According to the Novel Weapon Hypothesis, colonizers may out-compete local native species by bringing with them novel pathogens to which native species are not adapted. In contrast, the Enemy Release Hypothesis suggests that flourishing colonizers are successful because they have left their pathogens behind. To assess the role of avian malaria and related haemosporidian parasites in the global spread of a common invasive bird, we examined the prevalence and genetic diversity of haemosporidian parasites (order Haemosporida, genera Plasmodium and Haemoproteus) infecting house sparrows (Passer domesticus). We sampled house sparrows (N = 1820) from 58 locations on 6 continents. All the samples were tested using PCR-based methods; blood films from the PCR-positive birds were examined microscopically to identify parasite species. The results show that haemosporidian parasites in the house sparrows' native range are replaced by species from local host-generalist parasite fauna in the alien environments of North and South America. Furthermore, sparrows in colonized regions displayed a lower diversity and prevalence of parasite infections. Because the house sparrow lost its native parasites when colonizing the American continents, the release from these natural enemies may have facilitated its invasion in the last two centuries. Our findings therefore reject the Novel Weapon Hypothesis and are concordant with the Enemy Release Hypothesis.

Spatial Variation of Haemosporidian Parasite Infection in African Rainforest Bird Species

Spatial heterogeneity influences the distribution, prevalence, and diversity of haemosporidian parasites. Previous studies have found complex patterns of prevalence with respect to habitat characteristics and parasite genotype, and their interactions, but there is little information regarding how parasitemia intensity and the prevalence of co-infections may vary in space. Here, using both molecular methods and microscopy, we report an analysis of the variation of parasitemia intensity and co-infections of avian haemosporidian parasites ( Plasmodium and Haemoproteus species) in 2 common African birds species, the yellow-whiskered greenbul ( Andropadus latirostris ) and the olive sunbird ( Cyanomitra olivacea ), at 3 sites with distinct habitat characteristics in Ghana. First, we found an interaction between the site and host species for the prevalence of Plasmodium spp. and Haemoproteus spp. For the olive sunbird, the prevalence of Plasmodium spp., as well as the number of individuals with co-infections, varied significantly among the sites, but these measures remained constant for the yellow-whiskered greenbul. In addition, yellow-whiskered greenbuls infected with Haemoproteus spp. were found only at 1 site. Furthermore, for both bird species, the parasitemia intensity of Plasmodium spp. varied significantly among the 3 sites, but with opposing trends. These results suggest that spatial heterogeneity differently affects haemosporidian infection parameters in these vertebrate-hosts. Environmental conditions here can either favor or reduce parasite infection. We discuss the implications of these discrepancies for conservation and ecological studies of infectious diseases in natural populations.