Blood parasites of Nearctic-Neotropical migrant passerine birds during spring trans-Gulf migration: impact on host body condition

To test the hypothesis that migrants infected with blood parasites arrive on the northern coast of the Gulf of Mexico in poorer condition than uninfected birds, we examined 1705 migrant passerine birds representing 54 species of 11 families from 2 Gulf Coast sites for blood parasites. Three hundred and sixty (21.1%) were infected with 1 or more species of 4 genera of blood parasites. The prevalence of parasites was as follows: Haemoproteus spp. (11.7%), Plasmodium spp. (6.7%), Leucocytozoon spp. (1.3%), and Trypanosoma spp. (1.2%). Both prevalence and density of Haemoproteus spp. infection varied among species. We found no relationship of gender or age with the prevalence of Haemoproteus spp. infection or Plasmodium spp. infection, with the exception of the orchard oriole (Icterus spurius) for which older birds were more likely to be infected with Haemoproteus spp. than younger birds. We also found that scarlet tanagers and summer tanagers infected with species of Haemoproteus have lower fat scores than uninfected individuals and that rose-breasted grosbeaks and Baltimore orioles infected with Haemoproteus spp. have a smaller mean body mass than uninfected individuals. Blood parasites do seem to pose a physiological cost for Neotropical migrant passerines and may be important components of the ecology of these species.     

Paucity of hematozoa in Colombian birds

Sixty-four birds of 43 species were caught at six localities in Colombia during the dry season in March 1998 and investigated for hematozoa by microscopic examination of stained blood films. Haemoproteus coatneyi, Plasmodium vaughani, Leucocytozoon sp., and microfilariae were identified. The overall prevalence of infection was 8%. Prevalences of infection for Haemoproteus spp., Plasmodium spp., Leucocytozoon spp., and microfilariae were 3%, 2%, 2%, and 3%, respectively. All hemosporidian infections encountered were of low intensity (< 1% of infected erythrocytes). The low prevalences and intensities of hemosporidian parasites in this study are in accord with other records from the Neotropics.     

Avian hemosporidian parasites from northern California oak woodland and chaparral habitats

During spring-summer 2003-2004, the avian community was surveyed for hemosporidian parasites in an oak (Quercus spp.) and madrone (Arbutus spp.) woodland bordering grassland and chaparral habitats at a site in northern California, a geographic location and in habitat types not previously sampled for these parasites. Of 324 birds from 46 species (21 families) sampled (including four species not previously examined for hemosporidians), 126 (39%) were infected with parasites identified as species of one or more of the genera Plasmodium (3% of birds sampled), Haemoproteus (30%), and Leucocytozoon (11%). Species of parasite were identified by morphology in stained blood smears and were consistent with one species of Plasmodium, 11 species of Haemoproteus, and four species of Leucocytozoon. We document the presence of one of the parasite genera in seven new host species and discovered 12 new parasite species-host species associations. Hatching-year birds were found infected with parasites of all three genera. Prevalence of parasites for each genus differed significantly for the entire sample, and prevalence of parasites for the most common genus, Haemoproteus, differed significantly among bird families. Among families with substantial sample sizes, the Vireonidae (63%) and Emberizidae (70%) were most often infected with Haemoproteus spp. No evidence for parasite between-genus interaction, either positive or negative, was found. Overall prevalence of hemosporidians at the northern California sites and predominance of Haemoproteus spp. was similar to that reported in most other surveys for the USA, Canada, and the Caribbean islands.     

A comparison of the blood parasites in three subspecies of the yellow wagtail Motacilla flava

One-hundred and eighty yellow wagtails Motacilla flava belonging to 3 subspecies (Motacilla flava feldegg, Motacilla flava flava, Motacilla flava thunbergi) were caught during the spring migration in south Kazakhstan and investigated by microscopic examination of stained blood smears. Haemoproteus anthi, Haemoproteus motacillae, Leucocytozoon fringillinarum, Leucocytozoon majoris, Plasmodium relictum, Plasmodium polare, Atoxoplasma sp., Trypanosoma sp., and microfilariae were identified. The overall prevalence of infection was 47.8%. Prevalences of Haemoproteus spp. (27.2%), Plasmodium spp. (25.0%), Leucocytozoon spp. (8.9%), Atoxoplasma spp. (4.4%), Trypanosoma spp. (1.1%), and microfilariae (0.6%) were recorded. No differences were discernible in parasite fauna or intensities of infection between males and females or between different subspecies. However, prevalence of infection of Haemoproteus, Leucocytozoon, and Plasmodium spp. was different in different host subspecies. These differences can be explained by differences in geographical location of breeding areas of these birds.     

Prevalence and diversity patterns of avian blood parasites in degraded African rainforest habitats

Land use changes including deforestation, road construction and agricultural encroachments have been linked to the increased prevalence of several infectious diseases. In order to better understand how deforestation affects the prevalence of vector-borne infectious diseases in wildlife, nine paired sites were sampled (disturbed vs. undisturbed habitats) in Southern Cameroon. We studied the diversity, prevalence and distribution of avian malaria parasites ( Plasmodium spp.) and other related haemosporidians (species of Haemoproteus and Leucocytozoon ) from these sites in two widespread species of African rainforest birds, the yellow-whiskered greenbul ( Andropadus latirostris , Pycnonotidae) and the olive sunbird ( Cyanomitra olivacea , Nectariniidae). Twenty-six mitochondrial cytochrome b lineages were identified: 20 Plasmodium lineages and 6 Haemoproteus lineages. These lineages showed no geographic specificity, nor significant differences in lineage diversity between habitat types. However, we found that the prevalence of Leucocytozoon and Haemoproteus infections were significantly higher in undisturbed than in deforested habitats ( Leucocytozoon spp. 50.3% vs. 35.8%, Haemoproteus spp. 16.3% vs. 10.8%). We also found higher prevalence for all haemosporidian parasites in C. olivacea than in A. latirostris species (70.2% vs. 58.2%). Interestingly, we found one morphospecies of Plasmodium in C. olivacea , as represented by a clade of related lineages, showed increased prevalence at disturbed sites, while another showed a decrease, testifying to different patterns of transmission, even among closely related lineages of avian malaria, in relation to deforestation. Our work demonstrates that anthropogenic habitat change can affect host–parasite systems and result in opposing trends in prevalence of haemosporidian parasites in wild bird populations.     

Hematozoa from the spotted owl

One hundred five spotted owls (Strix occidentalis) from seven populations and three subspecies were examined for hematozoa. Haemoproteus noctuae, H. syrnii, Leucocytozoon ziemanni, Trypanosoma avium, Atoxoplasma sp. and unidentified microfilariae were recorded. All northern (S. occidentalis caurina), California (S. occidentalis occidentalis) and Mexican (S. occidentalis lucida) spotted owls were infected with at least one hematozoan; 79% had multiple infections. Twenty-two percent of the owls were infected with as many as four species of parasites. There were significant differences in the prevalence of these species of parasites occurring among the five populations of northern and California spotted owls sampled in California. Haemoproteus noctuae, H. syrnii and Atoxoplasma sp. represented new host records for this host species.     

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.     

Interspecific differences in hematozoan infection in Sonoran desert Aimophila sparrows

Numerous studies have identified factors that control avian hematozoan infections, but the mechanisms that account for host differences in parasitemia remain largely speculative. To address this issue, we compared the prevalence of these parasites in stained blood smears from four conspecific Sonoran desert Aimophila sparrow species sampled during their breeding season: rufous-winged (Aimophila carpalis; RWSP), rufous-crowned (Aimophila ruficeps; RCSP), Cassin's (Aimophila cassinii, CASP), and Botteri's (Aimophila botterii; BOSP) sparrows. Blood smears contained Haemoproteus fringillae (RWSP), Trypanosoma everetti (RWSP, RCSP, BOSP), Trypanosoma avium (CASP), and microfilariae (all species). Most (92.5%) RWSP (n=40) were infected with Haemoproteus, but this parasite was not detected in RCSP (n=20) or BOSP (n=20) and was found only in one (2.5%) CASP (n=40). Trypanosoma spp. and microfilariae were detected in all species, but prevalence differed between these four sparrow species. Species differences in parasite prevalence were not due to difference in sex, age, adult body mass, incubation period, breeding habitat, or plumage colorfulness. However, differences in Haemoproteus sp. prevalence correlated with preferred nesting height, as RWSP generally nest above ground, whereas the other species nest on or close to the ground. Elevated H. fringillae prevalence in breeding-condition RWSP presumably does not result from a seasonal relapse associated with breeding or require new infection because 1) this prevalence did not differ in males sampled during and outside (n=21) the breeding season, and 2) all male RWSP (n=25) that we held in captivity and shielded from new infections and influence of natural photoperiod for 1 yr had viable blood H. fringillae gametocytes. H. fringillae prevalence in fall-sampled hatch-year male RWSP (n=11) was 63.6%, demonstrating that this parasite can be transmitted on the breeding grounds and during the first months of life. T. everetti prevalence in RWSP was lower in winter than in summer and also in long-term captive than in free-ranging adults. Presence of this parasite in the blood of breeding males may depend on recrudescence of existing infections or new infections.     

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.     

Haemoproteus spp. and Leukocytozoon spp. in a captive raptor population

Raptors are commonly infected with two blood parasites of the family Haemoproteidae, Haemoproteus spp. and Leukocytozoon spp. To determine if age or length of time in captivity influence prevalence of Haemoproteus spp. and Leukocytozoon spp. infection in captive raptors, blood samples were collected from 55 birds from April 1999 to May 2000. Blood smears were examined for parasitemia and influence of age and length of time in captivity at the time of sample collection were compared. We found juvenile and adult birds were more likely to be infected with Leukocytozoon spp. than were nestlings (P = 0.006) and birds present for > 365 days were more likely to be infected with Haemoproteus spp. and/or Leukocytozoon spp. than were birds captive for < 365 days.     

New avian Haemoproteus species (Haemosporida: Haemoproteidae) from African birds, with a critique of the use of host taxonomic information in hemoproteid classification

Haemoproteus (Parahaemoproteus) micronuclearis n. sp., Haemoproteus (Parahaemoproteus) nucleofascialis n. sp., Haemoproteus (Parahaemoproteus) paranucleophilus n. sp., and Haemoproteus (Parahaemoproteus) homobelopolskyi n. sp. (Haemosporida, Haemoproteidae) are described from African passeriform birds based on the morphology of their blood stages and segments of the mitochondrial cytochrome b gene. Red-billed quelea (Quelea quelea), red-headed malimbe (Malimbus rubricollis), and black-headed weaver (Ploceus melanocephalus) are the type vertebrate hosts of new hemoproteids. It is probable that new species have wide distribution in weavers in sub-Saharan Africa. Both H. micronuclearis and H. nucleofascialis can be readily distinguished from other avian hemoproteids by tiny, compact microgametocyte nuclei that are significantly smaller than macrogametocyte nuclei and are a rare character of hemosporidian parasites. Gametocytes of H. paranucleophilus are closely appressed to the erythrocyte nuclei and do not touch the erythrocyte envelope along their entire margin at all stages of their development, including fully grown gametocytes. A particularly distinctive feature of H. homobelopolskyi development is the presence of circumnuclear dumbbell-shaped macrogametocytes. Illustrations of blood stages of the new species are given, and morphological and phylogenetic analyses identify the DNA lineages that are associated with these parasites. Numerous recent studies show that some lineages of hemoproteids are often present in birds belonging to different families. As a result, the use of the host family as a taxonomic character should be questioned and preferably discouraged in hemoproteid taxonomy, particularly with regard to the parasites of passerine birds. Microscopic identification of avian hemoproteids requires comparison of Haemoproteus species described from birds of different families, as is an established practice with avian Plasmodium spp. Development of bar-coding techniques remains essential in taxonomic and field studies of hemosporidian parasites.     

Presence of Plasmodium and Haemoproteus in breeding prothonotary warblers (Protonotaria citrea: Parulidae): temporal and spatial trends in infection prevalence

Prothonotary warbler (Protonotaria citrea) has shown a long-term decline in abundance in the United States. As a long-range migrant, these warblers are exposed to parasites in both tropical and temperate regions. The focus of this study was to use molecular techniques to examine the temporal prevalence patterns of heamosopridian parasites Plasmodium and Haemoproteus in breeding prothonotary warblers. The prevalence (presence or absence) of Plasmodium and Haemoproteus species was assayed using primer sets for the cytochrome b gene of the mitochondrial DNA. Blood samples were obtained from 187 adult prothonotary warblers collected at 3 central Virginia, U.S.A., breeding sites. The relationship between haemosporidian parasite infections and reproductive success also was examined. We found that 71% of captured prothonotary warblers were infected with haemosporidian parasites, specifically, with 36% prevalence for Haemoproteus spp. and 44% prevalence for Plasmodium spp., during the 2008 breeding season; for both parasites, prevalence increased throughout the season. We found significant variation in haemosporidian parasite prevalence across the breeding season that was strongly site specific. Conversely, we found no significant effects of haemosporidian parasite infections on the reproductive success of prothonotary warblers. This is in sharp contrast to recent reports suggesting considerable effects of these parasites on the reproductive success of wild birds.     

Variation in host specificity between species of avian hemosporidian parasites: evidence from parasite morphology and cytochrome B gene sequences

A parasite's shift to a new host may have serious evolutionary consequences, since host switching usually is associated with a change in virulence and may lead to the evolution of emerging diseases. This phenomenon remains insufficiently studied in wildlife. Here, we combine microscopic examination of blood films and PCR-based methods to investigate the natural host specificity of Haemoproteus and Plasmodium spp. in birds of 4 families of the Passeriformes within a small geographic area. The material was collected on the Curonian Spit in the Baltic Sea between May and July in 2003-2004. A nested-PCR protocol was used for amplifying and sequencing a fragment of 480 nucleotides of the cytochrome b gene of the mtDNA of these parasites. Blood samples from 282 birds, which were positive both by microscopic examination of blood films and mtDNA amplification, were used in this study. We found that Haemoproteus majoris (lineages hPARUS1, hCCF5, hWW2, and hPHSIB1), Haemoproteus sp. (hWW1), Plasmodium (Haemamoeba) sp. (pSGS1), and Plasmodium (Haemamoeba) sp. (pGRW11) are capable of infecting birds belonging to different families of passeriform birds. Some species of Haemoproteus are less specific than have been traditionally believed. Haemoproteus majoris appears to have a genetic predisposition to have a broad host range. The level of host specificity varies markedly among different species of hemosporidian parasites of birds. The natural host range is thus not a reliable taxonomic character in the systematics of these parasites in the form in which it is still accepted in some recent taxonomic studies.     

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.     

The occurrence of haemosporidian parasites in the Fennoscandian bluethroat ( Luscinia svecica) population

A total of 86 adult bluethroats (Luscinia svecica) from nine different localities, covering the full length of the Fennoscandian mountain range, were screened for blood parasites of the three genera Haemoproteus, Plasmodium and Leucocytozoon using a recently developed polymerase chain reaction method. The overall occurrence of infection was 59.3%. Prevalence of Leucocytozoon spp. (47.7%), Plasmodium spp. (23.3%) and Haemoproteus spp. (1.2%) was detected. Of the infected birds, 15.1% carried mixed infections. Five different mitochondrial DNA-lineages of Leucocytozoon spp., eight lineages of Plasmodium spp. and one lineage of Haemoproteus spp. were found. Due to large sequence divergence these corresponded to at least five different species, but with the possibility of all 14 being independent evolutionary units with the potential of evolving different effects on the host. Of the lineages of Leucocytozoon spp., the most common was found throughout the range. The occurrence of the second most common lineage of Leucocytozoon spp. showed significant variation in prevalence between sites. The data also showed molecular evidence of one lineage of Leucocytozoon sp. existing in more than one species of avian host, thus challenging the use of host taxon as a taxonomic character when distinguishing between different species leucocytozoids.Communicated by F. Bairlein     

Prevalence and lineage diversity of avian haemosporidians from three distinct cerrado habitats in Brazil

Habitat alteration can disrupt host-parasite interactions and lead to the emergence of new diseases in wild populations. The cerrado habitat of Brazil is being fragmented and degraded rapidly by agriculture and urbanization. We screened 676 wild birds from three habitats (intact cerrado, disturbed cerrado and transition area Amazonian rainforest-cerrado) for the presence of haemosporidian parasites (Plasmodium and Haemoproteus) to determine whether different habitats were associated with differences in the prevalence and diversity of infectious diseases in natural populations. Twenty one mitochondrial lineages, including 11 from Plasmodium and 10 from Haemoproteus were identified. Neither prevalence nor diversity of infections by Plasmodium spp. or Haemoproteus spp. differed significantly among the three habitats. However, 15 of the parasite lineages had not been previously described and might be restricted to these habitats or to the region. Six haemosporidian lineages previously known from other regions, particularly the Caribbean Basin, comprised 50-80% of the infections in each of the samples, indicating a regional relationship between parasite distribution and abundance.     

Blood parasites of birds in Cameroon

Birds from south-central Cameroon, western Africa, were surveyed for blood parasites from August to October 1986. Of 331 birds examined, representing 65 species of 15 families and 6 orders (mostly passerines), 55 (17%) were found to be infected with 1 or more genera of hemotropic parasites. These included: Haemoproteus spp. (11% prevalence), Leucocytozoon spp. (3%), Plasmodium spp. (2%), Trypanosoma spp. (1%), and microfilariae of filariid nematodes (1%). Several new host-parasite associations were identified.     

A cautionary note on the use of nested PCR for parasite screening--an example from avian blood parasites

The use of new powerful nested polymerase chain reaction (PCR) techniques to identify and screen for prevalence of parasites has a huge potential. It allows for the detection and identification of low-intensity infections, but its high sensitivity and technical setup may also induce problems. Here, we report a cautionary note regarding misleading amplification of avian malaria species (Haemoproteus and Plasmodium) during Leucocytozoon spp. detection. We used a previously described nested PCR method for the molecular detection of avian malaria and Leucocytozoon spp. In the first step of the PCR protocol, these parasites are detected simultaneously; in the second PCR, Haemoproteus and Plasmodium spp. are separated from Leucocytozoon spp. However, in certain cases when a bird was infected with avian malaria, we obtained a slightly longer PCR product during the detection of Leucocytozoon spp. Our data imply that these "false" Leucocytozoon fragments are the consequences of strong amplification of certain malaria lineages in the first PCR, which can also be detected after the second PCR amplification that is specific to Leucocytozoon spp. parasites. Because these "false" Leucocytozoon fragments are slightly longer than the normal Leucocytozoon fragments, we suggest the use of well-separating agarose gels, several positive controls, and molecular standards to facilitate their separation. If one obtains a fragment that differs in length from the one expected for Leucocytozoon spp., sequencing is essential. More generally, in order to limit this type of problem with nested PCR protocols, we suggest that the first and the second primer pair be chosen so that they have different annealing temperatures.     

A new PCR assay for simultaneous studies of Leucocytozoon, Plasmodium, and Haemoproteus from avian blood

Many bird species host several lineages of apicomplexan blood parasites (Protista spp., Haemosporida spp.), some of which are shared across different host species. To understand such complex systems, it is essential to consider the fact that different lineages, species, and families of parasites can occur in the same population, as well as in the same individual bird, and that these parasites may compete or interact with each other. In this study, we present a new polymerase chain reaction (PCR) protocol that, for the first time, enables simultaneous typing of species from the 3 most common avian blood parasite genera (Haemoproteus, Plasmodium, and Leucocytozoon). By combining the high detection rate of a nested PCR with another PCR step to separate species of Plasmodium and Haemoproteus from Leucocytozoon, this procedure provides an easy, rapid, and accurate method to separate and investigate these parasites within a blood sample. We have applied this method to bird species with known infections of Leucocytozoon spp., Plasmodium spp., and Haemoproteus spp. To obtain a higher number of parasite lineages and to test the repeatability of the method, we also applied it to blood samples from bluethroats (Luscinia svecica), for which we had no prior knowledge regarding the blood parasite infections. Although only a small number of different bird species were investigated (6 passerine species), we found 22 different parasite species lineages (4 Haemoproteus, 8 Plasmodium, and 10 Leucocytozoon).