Seasonal dynamics in mosquito abundance and temperature do not influence avian malaria prevalence in the Himalayan foothills

We examined seasonal prevalence in avian haemosporidians (Plasmodium and Haemoproteus) in migrant and resident birds in western Himalaya, India. We investigated how infection with haemosporidians in avian hosts is associated with temporal changes in temperature and mosquito abundance along with host abundance and life‐history traits (body mass). Using molecular methods for parasite detection and sequencing partial cytochrome b gene, 12 Plasmodium and 27 Haemoproteus lineages were isolated. Our 1‐year study from December 2008 to December 2009 in tropical Himalayan foothills revealed a lack of seasonal variation in Plasmodium spp. prevalence in birds despite a strong correlation between mosquito abundance and temperature. The probability of infection with Plasmodium decreased with increase in temperature. Total parasite prevalence and specifically Plasmodium prevalence showed an increase with average avian body mass. In addition, total prevalence exhibited a U‐shaped relationship with avian host abundance. There was no difference in prevalence of Plasmodium spp. or Haemoproteus spp. across altitudes; parasite prevalence in high‐altitude locations was mainly driven by the seasonal migrants. One Haemoproteus lineage showed cross‐species infections between migrant and resident birds. This is the first molecular study in the tropical Himalayan bird community that emphasizes the importance of studying seasonal variation in parasite prevalence. Our study provides a basis for further evolutionary study on the epidemiology of avian malaria and spread of disease across Himalayan bird communities, which may not have been exposed to vectors and parasites throughout the year, with consequential implications to the risk of infection to naïve resident birds in high altitude.     

Patterns of haemosporidian prevalence along a range expansion in introduced Kenyan house sparrows Passer domesticus

Avian haemosporidian infections (of the genera Haemoproteus, Plasmodium and Leucocytozoon) can regulate passerine populations. Thus, reduction in the number of avian haemosporidian infections in a population, for example in recently introduced hosts, may facilitate host establishment or spread (i.e. enemy release). Alternatively, colonizers could decrease competitive ability of native individuals in the novel range by increasing the prevalence of avian haemosporidians in that native passerine community (i.e. novel weapons). However, whether either or both of these phenomena will occur is difficult to predict because infection risk can be highly heterogeneous and dependent upon the interaction of biotic and abiotic factors at the microclimate level, especially because of the important role of vectors for these parasites. Here, we describe which factors best predicted avian haemosporidian prevalence in populations of house sparrows Passer domesticus introduced to Kenya. House sparrows inhabit an invasion gradient in Kenya; they were introduced via the eastern port city of Mombasa in ? 1950 and have since spread west‐ward across the country. This range expansion gave us the opportunity to examine how parasite prevalence changes over small spatiotemporal scales and what role is played by environmental and individual traits. Among all individuals, body mass was the strongest predictor of infection, with larger house sparrows being more likely to be infected. At the population level, capture month, precipitation (higher prevalence with more rainfall), and population age (increasing prevalence with increasing time since introduction) were important risk factors. Overall, haemosporidian prevalence in Kenyan house sparrows appears to be more strongly associated with individual characteristics rather than with time since introduction as was predicted, though this does not necessarily rule out a role for enemy release or novel weapons in this system.     

Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges

Aim To use a comparative approach to understand parasite demographic patterns in native versus introduced populations, evaluating the potential roles of host invasion history and parasite life history. Location North American east and west coasts with a focus on San Francisco Bay (SFB). Methods Species richness and prevalence of trematode parasites were examined in the native and introduced ranges of two gastropod host species, Ilyanassa obsoleta and Littorina saxatilis. We divided the native range into the putative source area for introduction and areas to the north and south; we also sampled the overlapping introduced range in SFB. We dissected 14,781 snails from 103 populations and recorded the prevalence and identity of trematode parasites. We compared trematode species richness and prevalence across the hosts’ introduced and native ranges, and evaluated the influence of host availability on observed patterns. Results Relative to the native range, both I. obsoleta and L. saxatilis have escaped (lost) parasites in SFB, and L. saxatilis demonstrated a greater reduction of trematode diversity and infection prevalence than I. obsoleta. This was not due to sampling inequalities between the hosts. Instead, rarefaction curves suggested complete capture of trematode species in native source and SFB subregions, except for L. saxatilis in SFB, where infection was extremely rare. For I. obsoleta, infection prevalence of trematodes using fish definitive hosts was significantly lower in SFB compared to the native range, unlike those using bird hosts. Host availability partly explained the presence of introduced trematodes in SFB. Main conclusions Differential losses of parasite richness and prevalence for the two gastropod host species in their introduced range is probably the result of several mechanistic factors: time since introduction, propagule pressure, vector of introduction, and host availability. Moreover, the recent occurrence of L. saxatilis’ invasion and its active introduction vector suggest that its parasite diversity and distribution will probably increase over time. Our study suggests that host invasion history and parasite life history play key roles in the extent and diversity of trematodes transferred to introduced populations. Our results also provide vital information for understanding community‐level influences of parasite introductions, as well as for disease ecology in general.     

Haemosporidian infections in skylarks (<Emphasis Type="Italic">Alauda arvensis</Emphasis>): a comparative PCR-based and microscopy study on the parasite diversity and prevalence in southern Italy and the Netherlands

Changes in agricultural management have been identified as the most probable cause for the decline of Skylark (Alauda arvensis) populations in Europe. However, parasitic infections have not been considered as a possible factor influencing this process. Four hundred and thirty-four Skylarks from the Southern Italy and the Netherlands were screened for haemosporidian parasites (Haemosporida) using the microscopy and polymerase chain reaction (PCR)-based methods. The overall prevalence of infection was 19.5%; it was 41.8% in Italian birds and 8.3% in Dutch birds. The prevalence of Plasmodium spp. was 34.1% and 6.5% in Skylarks from Italy and Netherlands, respectively. Approximately 15% of all recorded haemosporidian infections were simultaneous infections both in Italian and Dutch populations. Six different mitochondrial cytochrome b (cyt b) lineages of Plasmodium spp. and three lineages of Haemoproteus tartakovskyi were found. The lineage SGS1 of Plasmodium relictum was the most prevalent at both study sites; it was recorded in 24.7% of birds in Italy and 5.5% in the Netherlands. The lineages SYAT05 of Plasmodium vaughani and GRW11 of P. relictum were also identified with a prevalence of <2% at both study sites. Two Plasmodium spp. lineages (SW2 and DELURB4) and three H. tartakovskyi lineages have been found only in Skylarks from Italy. Mitochondrial cyt b lineages SYAT05 are suggested for molecular identification of P. vaughani, a cosmopolitan malaria parasite of birds. This study reports the greatest overall prevalence of malaria infection in Skylarks during the last 100 years and shows that both Plasmodium and Haemoproteus spp. haemosporidian infections are expanding in Skylarks so it might contribute to a decrease of these bird populations in Europe.     

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.     

Haematozoa in forest birds from southern Chile: Latitudinal gradients in prevalence and parasite lineage richness

Abstract The existence of latitudinal gradients in species richness and their abundance is known for many free living organisms but few cases have been reported for parasitic diseases. In addition, asymmetries between the Northern and Southern Hemispheres in several characteristics may affect the distribution and diversity of species at all ecological levels. In this respect, we study the distribution of several genera of blood parasites infecting birds along a latitudinal gradient that includes the world's southernmost forests ecosystems. Birds were mist‐netted and sampled for blood in localities across Chile ranging from 33°S to 55°S during the years 2003–06. Overall, 26 bird species were sampled and 27 parasite lineages were identified. The latter belonged to three genera: Plasmodium (8), Haemoproteus (8) and Leucocytozoon (11). We found a positive significant relationship between prevalence and latitude for Leucocytozoon lineages and a negative relationship for Haemoproteus, Plasmodium and mixed infections. However, we did not find a significant relationship between parasite diversity and latitude. We found 18 lineages infecting only one species of host, and 19 lineages appear in only one of the localities of sampling. This pattern implies that some parasite lineages may evolve in isolation in some species/localities. In addition, specificity at the host‐family level was only found for Haemoproteus lineages infecting birds in the family Emberizidae. Individuals of the long distance migrant bird white‐crested elaenia (Elaenia albiceps), were found infected by the same parasite lineages in localities separated by 20° of latitude. Infections by these lineages were detected in other sedentary birds including juveniles and nestlings of different bird species. Therefore, long distance migrants are able to distort the presence of latitudinal gradients of diseases due to the potential role of migrants in spreading infections. Geographical gradients in prevalence of avian haematozoa differ between parasite genera and hemispheres, probably in relation to the existence of appropriate vector–parasite–host interactions.     

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown‐headed cowbirds Molothrus ater, and other co‐occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown‐headed cowbirds. The other Galapagos‐bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown‐headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non‐Galapagos haemosporidian lineages detected in bobolinks, brown‐headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites.     

Climate change increases the risk of malaria in birds

Malaria caused by Plasmodium parasites is one of the worst scourges of mankind and threatens wild animal populations. Therefore, identifying mechanisms that mediate the spread of the disease is crucial for both human health and conservation. Human‐induced climate change has been hypothesized to alter the geographic distribution of malaria pathogens. As the earth warms, arthropod vectors may display a general range expansion or may enjoy longer breeding season, both of which can enhance parasite transmission. Moreover, Plasmodium species may directly benefit for elevating temperatures, which provide stimulating conditions for parasite reproduction. To test for the link between climate change and malaria prevalence on a global scale for the first time, I used long‐term records on avian malaria, which is a key model for studying the dynamics of naturally occurring malarial infections. Following the variation in parasite prevalence in more than 3000 bird species over seven decades, I show that the infection rate by Plasmodium is strongly associated with temperature anomalies and has been augmented with accelerating tendency during the last 20 years. The impact of climate change on malaria prevalence varies across continents, with the strongest effects found for Europe and Africa. Migration habit did not predict susceptibility to the escalating parasite pressure by Plasmodium. Consequently, wild birds are at an increasing risk of malaria infection due to recent climate change, which can endanger both naïve bird populations and domesticated animals. The prevailing avian example may provide useful lessons for understanding the effect of climate change on malaria in humans.     

Prevalence and evolutionary relationships of haematozoan parasites in native versus introduced populations of common myna Acridotheres tristis

The success of introduced species is frequently explained by their escape from natural enemies in the introduced region. We tested the enemy release hypothesis with respect to two well studied blood parasite genera (Plasmodium and Haemoproteus) in native and six introduced populations of the common myna Acridotheres tristis. Not all comparisons of introduced populations to the native population were consistent with expectations of the enemy release hypothesis. Native populations show greater overall parasite prevalence than introduced populations, but the lower prevalence in introduced populations is driven by low prevalence in two populations on oceanic islands (Fiji and Hawaii). When these are excluded, prevalence does not differ significantly. We found a similar number of parasite lineages in native populations compared to all introduced populations. Although there is some evidence that common mynas may have carried parasite lineages from native to introduced locations, and also that introduced populations may have become infected with novel parasite lineages, it may be difficult to differentiate between parasites that are native and introduced, because malarial parasite lineages often do not show regional or host specificity.     

Exploring the Diversity and Distribution of Neotropical Avian Malaria Parasites – A Molecular Survey from Southeast Brazil

Southeast Brazil is a neotropical region composed of a mosaic of different tropical habitats and mountain chains, which allowed for the formation of bird-rich communities with distinct ecological niches. Although this region has the potential to harbor a remarkable variety of avian parasites, there is a lack of information about the diversity of malarial parasites. We used molecular approaches to characterize the lineage diversity of Plasmodium and Haemoproteus in bird communities from three different habitats in southeast Brazil based on the prevalence, richness and composition of lineages. We observed an overall prevalence of 35.3%, with a local prevalence ranging from 17.2% to 54.8%. Moreover, no significant association between prevalence and habitat type could be verified (p>0.05). We identified 89 Plasmodium and 22 Haemoproteus lineages, with 86% of them described for the first time here, including an unusual infection of a non-columbiform host by a Haemoproteus (Haemoproteus) parasite. The composition analyses of the parasite communities showed that the lineage composition from Brazilian savannah and tropical dry forest was similar, but it was different from the lineage composition of Atlantic rainforest, reflecting the greater likeness of the former habitats with respect to seasonality and forest density. No significant effects of habitat type on lineage richness were observed based on GLM analyses. We also found that sites whose samples had a greater diversity of bird species showed a greater diversity of parasite lineages, providing evidence that areas with high bird richness also have high parasite richness. Our findings point to the importance of the neotropical region (southeast Brazil) as a major reservoir of new haemosporidian lineages.     

Migrant birds disperse haemosporidian parasites and affect their transmission in avian communities

Migration has an important impact on the transmission of pathogens. Migratory birds disperse parasites through their routes and may consequently introduce them to new areas and hosts. Hence, haemosporidian parasites, which are among the most prevalent, diverse and important bird pathogens, are potentially dispersed when infecting migrant hosts. Further, migrant hosts could enhance local parasite prevalence and richness by transporting new parasite strains to new areas. Here, we hypothesize and aim to evaluate if 1) migratory birds spread parasite lineages along their routes, and 2) localities crossed by more migratory birds have greater prevalence and richness of haemosporidians. For the first hypothesis, we tested whether parasite lineages found 1) in both migrants and residents, and 2) only in residents, differ in their frequencies of occurrence among localities. For the second hypothesis, we tested for a relationship among localities between the overall local haemosporidian parasite richness and prevalence, and the proportion of migratory bird individuals present in a locality. We combined a dataset on 13 200 bird samples with additional data from the MalAvi database (total: ~2800 sequenced parasites comprising 675 distinct lineages, from 506 host species and 156 localities) from South America, and used Bayesian multi-level models to test our hypotheses. We demonstrate that parasites shared between resident and migratory species are the most spatially widespread, highlighting the potential of migrants to carry and transmit haemosporidians. Further, the presence of migrants in a locality was negatively related to local parasite richness, but not associated with local prevalence. Here, we confirm that migrants can contribute to parasite dispersal and visiting migrants are present in regions with lower Plasmodium prevalence. Also, we observed their presence might raise Haemoproteus community prevalence. Therefore, we demonstrate migrants enhance pathogens spread and their presence may influence parasite community transmission.     

Broad-scale latitudinal patterns of genetic diversity among native European and introduced house sparrow (Passer domesticus) populations

Introduced species offer unique opportunities to study evolution in new environments, and some provide opportunities for understanding the mechanisms underlying macroecological patterns. We sought to determine how introduction history impacted genetic diversity and differentiation of the house sparrow (Passer domesticus), one of the most broadly distributed bird species. We screened eight microsatellite loci in 316 individuals from 16 locations in the native and introduced ranges. Significant population structure occurred between native than introduced house sparrows. Introduced house sparrows were distinguished into one North American group and a highly differentiated Kenyan group. Genetic differentiation estimates identified a high magnitude of differentiation between Kenya and all other populations, but demonstrated that European and North American samples were differentiated too. Our results support previous claims that introduced North American populations likely had few source populations, and indicate house sparrows established populations after introduction. Genetic diversity also differed among native, introduced North American, and Kenyan populations with Kenyan birds being least diverse. In some cases, house sparrow populations appeared to maintain or recover genetic diversity relatively rapidly after range expansion (<50 years; Mexico and Panama), but in others (Kenya) the effect of introduction persisted over the same period. In both native and introduced populations, genetic diversity exhibited large-scale geographic patterns, increasing towards the equator. Such patterns of genetic diversity are concordant with two previously described models of genetic diversity, the latitudinal model and the species diversity model.     

Implications of Plasmodium parasite infected mosquitoes on an insular avifauna: the case of Socorro Island,México

Avian malaria (Plasmodium spp.) has been implicated in the decline of avian populations in the Hawaiian Islands and it is generally agreed that geographically isolated and immunologically naïve bird populations are particularly vulnerable to the pathogenic effects of invasive malaria parasites. In order to assess the potential disease risk of malaria to the avifauna of Socorro Island, México, we surveyed for Plasmodium isolates from 1,300 resident field‐caught mosquitoes. Most of them were identified as Aedes (Ochlerotatus) taeniorhynchus (Wiedemann, 1821), which were abundant in the salt marshes. We also collected Culex quinquefasciatus Say, 1823 close to human dwellings. Mitochondrial ND5 and COII gene sequences of Ae. taeniorhynchus were analyzed and compared to corresponding sequences of mosquitoes of the Galápagos Islands, Latin America, and the North American mainland. Aedes lineages from Socorro Island clustered most closely with a lineage from the continental U.S. Plasmodium spp. DNA was isolated from both species of mosquitoes. From 38 positive pools, we isolated 11 distinct mitochondrial Cytb lineages of Plasmodium spp. Seven of the Plasmodium lineages represent previously documented avian infective strains while four were new lineages. Our results confirm a potential risk for the spread of avian malaria and underscore the need to monitor both the mosquito and avian populations as a necessary conservation measure to protect endangered bird species on Socorro Island.     

Avian Plasmodium infection in field‐collected mosquitoes during 2012–2013 in Tarlac,Philippines

Global warming threatens to increase the spread and prevalence of mosquito‐transmitted diseases. Certain pathogens may be carried by migratory birds and transmitted to local mosquito populations. Mosquitoes were collected in the northern Philippines during bird migration seasons to detect avian malaria parasites as well as for the identification of potential vector species and the estimation of infections among local mosquito populations. We used the nested PCR to detect the avian malaria species. Culex vishnui (47.6%) was the most abundant species collected and Cx. tritaeniorhynchus (13.8%) was the second most abundant. Avian Plasmodium parasites were found in eight mosquito species, for which the infection rates were between 0.5% and 6.2%. The six Plasmodium genetic lineages found in this study included P. juxtanucleare ‐GALLUS02, Tacy7 (Donana04), CXBIT01, Plasmodium species LIN2 New Zealand, and two unclassified lineages. The potential mosquito vectors for avian Plasmodium parasites in the Philippines were Cq. crassipes, Cx. fuscocephala, Cx. quinquefasciatus, Cx. sitiens, Cx. vishnui, and Ma. Uniformis; two major genetic lineages, P. juxtanucleare and Tacy7, were identified.     

Distribution anomalies in avian haemosporidian parasites in the southern Lesser Antilles

We compared the haemosporidian parasite faunas (Plasmodium and Haemoproteus) of small land birds on the islands of St Lucia, St Vincent and Grenada in the southern Lesser Antilles. The islands differ in distance from the South American source of colonists, proximity to each other, and similarity of their avifaunas. On each island, we obtained 419–572 blood samples from 22–25 of the 34–41 resident species. We detected parasite infection by PCR and identified parasite lineages by sequencing a portion of the mitochondrial cytochrome b gene. Parasite prevalence varied from 31% on St Lucia to 22% on St Vincent and 18% on Grenada. Abundant parasite lineages differed between the three islands in spite of the similarity in host species. As in other studies, the geographic distributions of the individual parasite lineages varied widely between local endemism and broad distribution within the West Indies, including cases of long‐distance disjunction. St Vincent was unusual in the near absence of Plasmodium parasites, which accorded with low numbers of suitable mosquito vectors reported from the island. Parasites on St Vincent also tended to be host specialists compared to those on St Lucia and Grenada. Similarity in parasite assemblages among the three islands varied in parallel with host assemblage similarity (but not similarity of infected hosts) and with geographic proximity. Parasite prevalence increased with host abundance on both St Lucia and St Vincent, but not on Grenada; prevalence did not vary between endemic and more widespread host species. In addition, the endemic host species harbored parasites that were recovered from a variety of non‐endemic species as well. These results support the individualistic nature of haemosporidian parasite assemblages in evolutionarily independent host populations.     

Biogeographical patterns of blood parasite lineage diversity in avian hosts from southern Melanesian islands

Aim (1) To describe the species–area relationships among communities of Plasmodium and Haemoproteus parasites in different island populations of the same host genus (Aves: Zosterops). (2) To compare distance–decay relationships (turnover) between parasite communities and those with potential avian and dipteran hosts, which differ with respect to their movement and potential to disperse parasite species over large distances. Location Two archipelagos in the south‐west Pacific, Vanuatu and New Caledonia (c. 250 km west of Vanuatu) and its Loyalty Islands, with samples collected from a total of 16 islands of varying sizes (328–16,648 km²). Methods We characterized parasite diversity and distribution via polymerase chain reaction (PCR) from avian (Zosterops) blood samples. Bayesian methods were used to reconstruct the parasite phylogeny. In accordance with recent molecular evidence, we treat distinct mitochondrial DNA lineages as equivalent to species in this study. Path analysis and parasite lineage accumulation curves were used to assess the confounding effect of inadequate sampling on the estimation of parasite richness. Species–area and species–distance relationships were assessed using linear regression: distance–decay relationships were assessed using Mantel tests. Results Birds and mosquito species and Plasmodium lineages exhibited significant species–area relationships. However, Plasmodium lineages showed the weakest ‘species–area’ relationship; no relationship was found for Haemoproteus lineages. Avian species richness influenced parasite lineage richness more than mosquito species richness did. Within individual avian host species, the species–area relationship of parasites showed differing patterns. Path analysis indicated that sampling effort was unlikely to have a confounding effect on parasite richness. Distance from mainland (isolation effect) showed no effect on parasite richness. Community similarity decayed significantly with distance for avifauna, mosquito fauna and Plasmodium lineages but not for Haemoproteus lineages. Main conclusions Plasmodium lineages and mosquito species fit the power‐law model with steeper slopes than found for the avian hosts. The lack of species–distance relationship in parasites suggests that other factors, such as the competence of specific vectors and habitat features, may be more important than distance. The decay in similarity with distance suggests that the sampled Plasmodium lineages and their potential hosts were not randomly distributed, but rather exhibited spatially predictable patterns. We discuss these results in the context of the effects that parasite generality may have on distribution patterns.     

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.     

Avian Plasmodium lineages found in spot surveys of mosquitoes from 2007 to 2010 at Sakata wetland,Japan: do dominant lineages persist for multiple years?

The ecology and geographical distribution of disease vectors are major determinants of spatial and temporal variations in the transmission dynamics of vector‐borne pathogens. However, there are limited studies on the ecology of vectors that contribute to the natural transmission of most vector‐borne pathogens. Avian Plasmodium parasites are multihost mosquito‐borne pathogens transmitted by multiple mosquito species, which might regulate the diversity and persistence of these parasites. From 2007 to 2010, we conducted entomological surveys at Sakata wetland in central Japan, to investigate temporal variation in mosquito occurrence and prevalence of avian Plasmodium lineages in the mosquito populations. A polymerase chain reaction (PCR)‐based method was used to detect Plasmodium parasites and identify the blood sources of mosquitoes. Culex inatomii and C. pipiens pallens represented 60.0% and 34.8% of 11 mosquito species collected, respectively. Our results showed that the two dominant mosquito species most likely serve as principal vectors of avian Plasmodium parasites during June, which coincides with the breeding season of bird species nesting in the wetland reed beds. Fourteen animal species were identified as blood sources of mosquitoes, with the oriental reed warbler (Acrocephalus orientalis) being the commonest blood source. Although there was significant temporal variation in the occurrence of mosquitoes and prevalence of Plasmodium lineages in the mosquitoes, the dominant Plasmodium lineages shared by the two dominant mosquito species were consistently found at the same time during transmission seasons. Because vector competence cannot be confirmed solely by PCR approaches, experimental demonstration is required to provide definitive evidence of transmission suggested in this study.     

Blood and Tissue Protozoa of the English Sparrow (Passer domesticus domesticus) in Galveston,Texas*

SYNOPSIS. The 42% incidence of Plasmodium in blood films of English sparrows reported here is the highest on record for surveys of blood parasites of birds in the United States. The only Plasmodium species identified in the sparrows was P. relictum. Adult birds were almost universally infected and tended to experience the highest degree of parasitemia in the spring months, while young birds had a higher blood positivity in the summer months. The lowest incidence of Plasmodium positive blood films occurred in fall and winter in the Galveston area. Overwintering birds had a decrease in parasitemia corresponding to reported minimal gonadal activity in sparrows. The 20% incidence of Lankesterella (avian Toxoplasma) in the blood of these sparrows was also higher than has been reported in other blood film surveys in this country. Incidence of this parasite in blood films was highest in the summer months, corresponding with highest average temperature for the year. Lankesterella could be found in 95% of sparrows whose tissues were examined after autopsy. Ducks and pigeons in the immediate vicinity of the survey sparrows had neither Plasmodium nor Lankesterella in blood films. Resident wild birds from adjacent rural areas, including redwinged blackbirds, boat-tailed grackles, laughing gulls and meadowlarks, had fewer Plasmodium and Lankesterella than the sparrows. A few Lankesterella were found in the liver or spleen of young redwinged blackbirds, and only 2 of 79 wild birds had the organisms in their heart blood. Plasmodium was found only in meadowlarks and included P. hexamerium and elongatum as well as relictum.     

Climate,host phylogeny and the connectivity of host communities govern regional parasite assembly

Aim

Identifying barriers that govern parasite community assembly and parasite invasion risk is critical to understand how shifting host ranges impact disease emergence. We studied regional variation in the phylogenetic compositions of bird species and their blood parasites (Plasmodium and Haemoproteus spp.) to identify barriers that shape parasite community assembly.

Location

Australasia and Oceania.

Methods

We used a data set of parasite infections from >10,000 host individuals sampled across 29 bioregions. Hierarchical models and matrix regressions were used to assess the relative influences of interspecies (host community connectivity and local phylogenetic distinctiveness), climate and geographic barriers on parasite local distinctiveness and composition.

Results

Parasites were more locally distinct (co‐occurred with distantly related parasites) when infecting locally distinct hosts, but less distinct (co‐occurred with closely related parasites) in areas with increased host diversity and community connectivity (a proxy for parasite dispersal potential). Turnover and the phylogenetic symmetry of parasite communities were jointly driven by host turnover, climate similarity and geographic distance.

Main conclusions

Interspecies barriers linked to host phylogeny and dispersal shape parasite assembly, perhaps by limiting parasite establishment or local diversification. Infecting hosts that co‐occur with few related species decreases a parasite's likelihood of encountering related competitors, perhaps increasing invasion potential but decreasing diversification opportunity. While climate partially constrains parasite distributions, future host range expansions that spread distinct parasites and diminish barriers to host shifting will likely be key drivers of parasite invasions.