Parasite mediated mortality and host immune response explain age-related differences in blood parasitism in birds

Pleiotropic effects of melanin pigmentation: haemoparasite infection intensity but not telomere length is associated with plumage morph in black sparrowhawks

There is increasing recognition of the potential pleiotropic effects of melanin pigmentation, particularly on immunity, with reports of variation in haemoparasite infection intensity and immune responses between the morphs of colour-polymorphic bird species. In a population of the black sparrowhawk (Accipiter melanoleucus) in western South Africa, light morphs have a higher haemoparasite infection intensity, but no physiological effects of this are apparent. Here, we investigate the possible effects of haemoparasite infection on telomere length in this species and explore whether relative telomere length is associated with either plumage morph or sex. Using quantitative polymerase chain reaction analysis, we confirmed that dark morphs had a lower haemoparasite infection intensity than light morphs. However, we found no differences in telomere length associated with either the haemoparasite infection status or morph in adults, although males have longer telomeres than females. While differences in haemoparasite intensity between morphs are consistent with pleiotropic effects of melanin pigmentation in the black sparrowhawk, we found no evidence that telomere length was associated with haemoparasite infection. Further work is needed to investigate the implications of possible pleiotropic effects of plumage morph and their potential role in the maintenance of colour polymorphism in this species.

Higher body condition with infection by Haemoproteus parasites in Bananaquits (Coereba flaveola)

Parasite transmission is a heterogenous process in host-parasite interactions. This heterogeneity is particularly apparent in vector-borne parasite transmission where the vector adds an additional level of complexity. Haemosporidian parasites, a widespread protist, cause a malaria-like disease in birds globally, but we still have much to learn about the consequences of infection to hosts' health. In the Caribbean, where malarial parasites are endemic, studying host-parasites interactions may give us important insights about energetic trade-offs involved in malarial parasites infections in birds. In this study, we tested the consequences of Haemoproteus infection on the Bananaquit, a resident species of Puerto Rico. We also tested for potential sources of individual heterogeneity in the consequences of infection such as host age and sex. To quantify the consequences of infection to hosts' health we compared three complementary body condition indices between infected and uninfected individuals. Our results showed that Bananaquits infected by Haemoproteus had higher body condition than uninfected individuals. This result was consistent among the three body condition indices. Still, we found no clear evidence that this effect was mediated by host age or sex. We discuss a set of non-mutually exclusive hypotheses that may explain this pattern including metabolic syndrome, immunological responses leading to host tolerance or resistance to infection, and potential changes in consumption rates. Overall, our results suggest that other mechanisms, may drive the consequences of avian malarial infection.

Seasonal variations of intensity of avian malaria infection in the Thousand Island Lake System, China

BACKGROUND

Migratory birds play an important part in the spread of parasites, with more or less impact on resident birds. Previous studies focus on the prevalence of parasites, but changes in infection intensity over time have rarely been studied. As infection intensity can be quantified by qPCR, we measured infection intensity during different seasons, which is important for our understanding of parasite transmission mechanisms.

METHODS

Wild birds were captured at the Thousand Island Lake with mist nets and tested for avian hemosporidiosis infections using nested PCR. Parasites were identified using the MalAvi database. Then, we used qPCR to quantify the infection intensity. We analyzed the monthly trends of intensity for all species and for different migratory status, parasite genera and sexes.

RESULTS

Of 1101 individuals, 407 were infected (37.0%) of which 95 were newly identified and mainly from the genus Leucocytozoon. The total intensity trend shows peaks at the start of summer, during the breeding season of hosts and during the over-winter season. Different parasite genera show different monthly trends. Plasmodium causes high prevalence and infection intensity of winter visitors. Female hosts show significant seasonal trends of infection intensity.

CONCLUSIONS

The seasonal changes of infection intensity is consistent with the prevalence. Peaks occur early and during the breeding season and then there is a downward trend. Spring relapses and avian immunity are possible reasons that could explain this phenomenon. In our study, winter visitors have a higher prevalence and infection intensity, but they rarely share parasites with resident birds. This shows that they were infected with Plasmodium during their departure or migration and rarely transmit the disease to resident birds. The different infection patterns of different parasite species may be due to vectors or other ecological properties.

Haemosporidian Parasites of White-Breasted Waterhens (Amaurornis phoenicurus), with a Report and Molecular Characterization of Haemoproteus gallinulae in Thailand

Haemosporidian parasites are vector-borne parasites infecting terrestrial vertebrates as well as avian species, such as the White-breasted Waterhen, a Gruiformes waterbird found in lowlands near wetlands and distributed throughout Thailand. However, information regarding haemosporidia infection in this species is lacking. To establish regional information, 17 blood samples were collected from White-breasted Waterhens. Four haemoparasite lineages were identified in six blood samples: Haemoproteus gallinulae, Plasmodium collidatum, Plasmodium elongatum, and an unidentified Plasmodium species. H. gallinulae was characterized with morphological features in White-breasted Waterhens for the first time; the morphological characteristics were consistent with previous descriptions. H. gallinulae was more closely related to Haemoproteus species of Passeriformes birds than to those of Gruiformes birds. The Plasmodium parasites infecting these White-breasted Waterhens previously caused severe avian malaria in other host species. The unidentified Plasmodium species had rarely been documented, although it was reported in the Culex vector and was possibly associated with specialist parasites either as host or habitat. Our findings reveal multiple haemosporidian species reflecting the role of this avian host as a carrier of haemosporidians. This study offers species records and molecular materials that may provide critical information for further targeted research into these haemosporidia.

Variation in the parasite communities of three co-occurring herbivorous coral reef fishes

Parasites are important, diverse, and abundant components of natural ecosystems and can influence the behaviour and health of their hosts, inter- and intraspecific interactions, and ultimately community structure. Coral reefs are one of the world's most biodiverse ecosystems, yet our understanding of the abundance, diversity, and composition of parasite communities of coral reef fishes is limited. Here, the authors aimed to compare the abundance, richness and composition of parasite communities among three co-occurring herbivorous coral reef fishes (the barred rabbitfish Siganus doliatus, Ward's damsel Pomacentrus wardi and the obscure damsel Pomacentrus adelus) from an inshore reef of the Great Barrier Reef (GBR). In total, 3978 parasites (3869 endoparasites and 109 ectoparasites) from 17 families were recovered from 30 individuals of each of the three fish species (mean = 44 ± 22 s.e. parasites per fish; range = 0-1947 parasites per fish). The parasite communities of P. wardi and P. adelus were characterised by pennellid copepods, derogenid and lecithasterid digeneans and were distinct from those of S. doliatus that were characterised by a higher abundance of atractotrematid and gyliauchenid digeneans. The abundance and family richness of all parasites were greatest in S. doliatus (abundance: 22.1 ± 5.0 parasites per fish; richness: 3.2 ± 0.3 families per fish), intermediate in P. wardi (abundance: 4.8 ± 1.1 parasites per fish; richness: 2.3 ± 0.3 families per fish) and lowest in P. adelus (abundance: 1.4 ± 0.4 parasites per fish; richness: 0.9 ± 0.2 families per fish). Similarly, the abundance of endoparasites was greatest in S. doliatus (19.7 ± 5.1 endoparasites per fish), intermediate in P. wardi (2.6 ± 0.7 endoparasites per fish) and lowest in P. adelus (1.2 ± 0.4 endoparasites per fish). Ectoparasite abundances were also lowest for P. adelus (0.2 ± 0.1 ectoparasites per fish), and S. doliatus and P. wardi had comparable abundances of ectoparasites (1.3 ± 0.3 and 2.1 ± 0.5 parasites per fish, respectively). Similarities between the parasite assemblages of the two pomacentrids may be related to their similar behaviours and/or diets vs. those of the larger-bodied and more mobile rabbitfish. Investigating the causes and consequences of variation in parasite communities across a broader range of fish species will be critical to understand the potential role of parasites in coral reef ecosystems.

Haemosporidian parasites in the ash-breasted Sierra finch (Geospizopsis plebejus): insights from an Andean dry forest population

Haemosporidian genera Plasmodium, Haemoproteus and Leucocytozoon, responsible for avian malarial infections, are highly diverse and have a wide range of health effects and predictors, depending on the host and its environmental context. Here, we present, for the first time, detailed information on the identity, prevalence and parasitaemia of haemosporidians and other haemoparasites that infect the ash-breasted Sierra finch, Geospizopsis plebejus, in an Andean dry forest. We study the consequences of infection in the host body and health conditions and explore the environmental and intrinsic factors that influence infection status and parasitaemia. We conducted diagnoses by cytochrome b (cytb) sequencing and morphological identification, and estimated the levels of parasitaemia based on microscopy. We identified 6 cytb lineages infecting G. plebejus. Two of them were new lineages: Haemoproteus sp. GEPLE01 and GEPLE02. We also detected Haemoproteus sp. ZOCAP08, Haemoproteus sp. AMAVIR01, Plasmodium homopolare BAEBIC02 and Plasmodium cathemerium ZONCAP15. By microscopy, we detected Haemoproteus coatneyi, Haemoproteus erythrogravidus, P. homopolare and other unidentified species of Haemoproteus, Plasmodium, Babesia sp. and 1 microfilaria. We found no evidence of Leucocytozoon. Additionally, we detected several coinfections by sequencing and microscopy. The prevalence of haemosporidian infections was high (87.7%), and the mean parasitaemia was 61.65 infected cells per 10 000 erythrocytes examined. Prevalence and parasitaemia were higher for Haemoproteus than for Plasmodium. Haemoproteus sp. AMAVIR01 showed the highest prevalence (43.1%) and mean parasitaemia (94.39/10 000 erythrocytes) and might be associated with H. coatneyi. Immature individuals showed a lower prevalence than adults, supporting previous findings.

Prevalence of Haemosporidian Parasites in an Arctic Breeding Seabird Species-The Red-Throated Diver (Gavia stellata)

Haemosporida, vector-transmitted blood parasites, can have various effects and may also exert selection pressures on their hosts. In this study we analyse the presence of Haemosporida in a previously unstudied migratory seabird species, the red-throated diver Gavia stellata. Red-throated divers were sampled during winter and spring in the eastern German Bight (North Sea). We used molecular methods and data from a related tracking study to reveal (i) if red-throated divers are infected with Haemosporida of the genera Leucocytozoon, Plasmodium and Haemoproteus, and (ii) how infection and prevalence are linked with the breeding regions of infected individuals. Divers in this study were assigned to western Palearctic breeding grounds, namely Greenland, Svalbard, Norway and Arctic Russia. We found a prevalence of Leucocytozoon of 11.0% in all birds sampled (n = 45), of 33.0% in birds breeding in Norway (n = 3) and of 8.3% in birds breeding in Arctic Russia (n = 25). For two birds that were infected no breeding regions could be assigned. We identified two previously unknown lineages, one each of Plasmodium and Leucocytozoon. Haemosporida have not been detected in birds from Greenland (n = 2) and Svalbard (n = 2). In summary, this study presents the first record of Haemosporida in red-throated divers and reports a new lineage of each, Plasmodium and Leucocytozoon GAVSTE01 and GAVSTE02, respectively.

No strong associations between temperature and the host-parasite interaction in wild stickleback

As climate change progresses, thermal stress is expected to alter the way that host organisms respond to infections by pathogens and parasites, with consequences for the fitness and therefore population processes of both host and parasite. The authors used a correlational natural experiment to examine how temperature differences shape the impact of the cestode parasite Schistocephalus solidus on its host, the three-spined stickleback (Gasterosteus aculeatus). Previous laboratory work has found that high temperatures benefit S. solidus while being detrimental to the stickleback. The present study sought to emulate this design in the wild, repeatedly sampling naturally infected and uninfected fish at matched warmer and cooler locations in the Baltic Sea. In this wild study, the authors found little evidence that temperature was associated with the host-parasite interaction. Although infection reduced host condition and reproductive status overall, these effects did not vary with temperature. Host fitness indicators correlated to some extent with temperature, with cooler capture sites associated with larger size but warmer sites with improved reproductive potential. Parasite fitness (prevalence or size) was not correlated with temperature at the capture site. These mismatches between laboratory and field outcomes illustrate how findings from well-controlled laboratory experiments may not fully reflect processes in more variable natural settings. Nonetheless, the findings of this study indicate that temperature can influence host fitness regardless of infection, with potential consequences for both host demography and parasite transmission dynamics in this complex system.

A novel one-step multiplex PCR protocol to detect avian haemosporidian parasites in the subgenus Haemoproteus (Kruse, 1890) used to quantify parasite prevalence in domestic pigeons (Columba livia) in Turkey

Infections of avian haemosporidian parasites are regularly identified by molecular methods including multiplex PCR, which allows researchers to distinguish mixed infections of parasites from multiple genera. Here we extend the utility of a previously designed multiplex PCR by designing a primer set specific to parasites of the subgenus Haemoproteus (genus: Haemoproteus). The updated one-step multiplex PCR protocol we describe here allows for the detection of the genera Plasmodium and Leucocytozoon and the two subgenera (Haemoproteus and Parahaemoproteus) of the genus Haemoproteus. A sensitivity analysis showed that the multiplex PCR could amplify DNA of parasites in the subgenus Haemoproteus at very low levels of infection. We used this multiplex PCR to identify haemosporidian infections in 250 adult domestic pigeons (Columba livia) in Turkey. All samples were also screened by microscopy and a widely used nested PCR to compare with the results of multiplex PCR, to detect low levels of parasitemia, and to identify possible abortive infections. In total, 71 pigeons (28.4%) were found to be infected by all three methods. The multiplex PCR protocol successfully detected and discriminated both subgenera Haemoproteus and Parahaemoproteus infections. We compared our results with previous host species records to assess the host specificity of the parasite lineages we found. Our findings provide novel data on the prevalence of avian haemosporidians in domestic pigeons and demonstrate the utility of the new one-step multiplex PCR protocol for the determination of mixed avian haemosporidian infections. We expect that this protocol will contribute to a better understanding of the distribution, epizootiology, and ecology of avian haemosporidians.

Longitudinal dynamics and health impact of Hepatozoon procyonis (Apicomplexa: Hepatozoidae) on naturally infected ring-tailed coatis Nasua nasua (Carnivora: Procyonidae) from Midwestern Brazil

This study aimed to morphologically and molecularly detect Hepatozoon procyonis in ring-tailed coatis' (Nasua nasua) blood and associated ticks from central-western Brazil, Campo Grande, Mato Grosso do Sul state and also evaluate the impact of the protozoa in blood parameters and coati´s health. Samplings were performed in a conservation area Parque Estadual do Prosa (PEP) and in a Brazilian Air Force Private Area namely Vila da Base Aérea (VBA), between March 2018 and April 2019. We collected 165 blood samples, 61 from recaptured coatis. Peripheral blood smears were stained with Romanovsky-type stain for H. procyonis parasitemia assessment. DNA extracted from blood samples and ticks (Amblyomma spp.) were submitted to a nested PCR (nPCR) assay based on the 18S rRNA gene for Hepatozoon spp. Out of 104 individuals sampled, 80 (77%) were positive for H. procyonis in at least one capture. Overall, 67/165 (40.6%) blood smears showed H. procyonis gametocytes (PEP: 41/63 - 65%; VBA: 26/102 - 25.5%). Parasitemia based on 500 assessed leucocytes ranged from 1 (0.2%) to 50 (10%) and 1 (0.2%) to 25 (5%), from animals sampled in PEP and VBA, respectively. Fluctuation on the parasitemia was observed during recaptures. nPCR results showed higher positivity when compared to blood smears, i.e. 112/165 (68%) positive blood samples [PEP: 41/63 (65%), VBA: 26/102 (25.5%)]. In total, 63/248 (25.4%) tick DNA samples were positive at nPCR for Hepatozoon sp., including 32/87 (37%) pools (1 to 10 larvae) of Amblyomma larvae, 21/105 (20%) pools (1 to 5 nymphs) of Amblyomma sculptum nymphs, 9/43 (21%) pools (1 to 5 nymphs) of Amblyomma dubitatumnymphs, and 1/12 (8%) A. sculptum adult female. The partial 18S rRNA sequence from one coati's blood sample and one representative of each positive tick species randomly selected from each area for sequencing (1,000 bp) showed 100% identity with sequences of H. procyonis from GenBank previously detected in coatis. Regarding H. procyonis infection, no statistical differences were obtained when comparing males vs. females (p-value 0.67), immature animals vs. adults (p-value 0.31), rainy vs. dry season (p-value 0.51) and sampling location (p-value 0.42). No noticeable alteration in blood parameters or heath status was observed in parasite animals. H. procyonis circulates in a high prevalence in coatis from central-western Brazil. Parasitemia fluctuates among different coatis' recaptures and apparently the infection has no influence in coatis' hematological and clinical parameters.

The influence of age on the occurrence of internal parasites in perch (Perca fluviatilis L.) from Lake Góreckie in Wielkopolski National Park

The European perch (Perca fluviatilis L.) is a common freshwater fish which is widely distributed in Europe and Asia and has been successfully introduced to New Zealand and Australia. It is the intermediate and definitive host of many parasites, especially endoparasites, such as trematodes, cestodes and nematodes (Bikhovskaya-Pavlovskaya and Kulakova,1987; Carney and Dick, 1999; Behrmann-Godel and Brinker, 2005; Wierzbicka et al., 2005; Kuchta et al., 2009). Information concerning the parasites of perch can be found in widely published literature (Rolbiecki, 2006; Halmetoja et al., 2000), but still little is known about aspects such as the age dynamics of infections with endoparasites. Parasites provide a great deal of biological information about their host, regarding migration, differences in diet, and food web structure (Williams et al., 1992; MacKenzie et al., 1995; Marcogliese et al., 2006). On the other hand, parasitism may influence the behaviour of fish (hosts), resulting in changes in their habitat and increasing vulnerability to predators (Seppälä et al., 2008). Infection with parasites increases the relative risk of mortality in the host (Behrmann-Godel and Brinker, 2005). In this paper we determined the occurrence of parasites in perch from Lake Góreckie, Wielkopolski National Park. Perch is common in water bodies and has a diverse diet, and for these reasons it is the definitive or intermediate host of many parasite species. Therefore, this fish species was selected for our study. The influence of age on the occurrence of parasites in perch has not yet been examined in detail. <br>The aim of this study was to answer the following questions: </br><br>• What parasites occur in perch in Lake Góreckie? </br><br>• Which species of endoparasites are more frequently observed in perch in Lake Góreckie? </br><br>• Is there a correlation between the occurrence of the endoparasite and the age of perch? </br>

Seasonal Dynamics and Diversity of Haemosporidians in a Natural Woodland Bird Community in Slovakia

Despite the ubiquity of disease seasonality, mechanisms behind the fluctuations in seasonal diseases are still poorly understood. Avian hemosporidiosis is increasingly used as a model for ecological and evolutionary studies on disease dynamics, but the results are complex, depending on the focus (hosts, parasites, vectors) and scale (individuals, community, populations) of the study. Here, we examine the local diversity of haemosporidian parasites and the seasonal patterns of infections, parasite richness, and diversity in a natural woodland bird community in Slovakia. In 35 avian species, we detected 111, including 19 novel, haemosporidian cytochrome b lineages. The highest numbers of lineages were detected during spring and autumn, corresponding with higher avian species richness and infection prevalence in the avian community during these periods of time. Nevertheless, the haemosporidian community in the local breeders in summer was relatively stable, Haemoproteus lineages dominated in the local avian haemosporidian community, and only few parasite lineages were abundant within each genus. While prevailing Leucocytozoon infections in spring suggest that the majority of sampled birds wintered in the Mediterranean region, Plasmodium infections in spring can be due to relapses in reproductively active short-distance migrants. Multiple haemosporidian infections, both intra- and inter-generic ones, were common in the local avian community. Infection intensity peaked during summer and tended to be higher in older birds, pointing to the role of supressed immunity in reproductively active birds.

Studies on parasitic prevalence in pet birds from Punjab, Pakistan

During this one year study, blood and fecal samples of doves (Zenaida asiatica), ducks (Anas platyrhynchos), pigeons (Columba livia), partridges (Alectoris chukar), turkeys (Meleagris gallopavo) and goose (Chen caerulescens) were collected to assess the parasitic prevalence in these birds. The birds were kept at Avian Conservation and Research Center, Department of Wildlife and Ecology, University of Veterinary and Animal Sciences, Lahore. All these avian species were kept in separate cages and their entire body was inspected on regularly basis to record external parasites. For internal parasites, 100 blood and 100 fecal samples for each species were analyzed. During present study, two species of ectoparasites i.e. fowl ticks (Args persicus) and mite (Dermanyssus gallinae) while 17 species of endoparasites; three from blood and 14 from fecal samples were identified. Prevalence of blood parasites was Plasmodium juxtanucleare 29.3%, Aegyptinella pullorum 15% and Leucoctoyzoon simond 13%. Parasitic species recorded from fecal samples included 6 species of nematodes viz. Syngamus trachea with parasitic prevalence of 50%, Capillaria anatis 40%, Capillaria annulata 37.5%, Heterakis gallinarum 28.3%, Ascardia galli 24% and Allodpa suctoria 2%. Similarly, two species of trematodes viz. Prosthogonimus ovatus having parasitic prevalence of 12.1% and Prosthogonimus macrorchis 9.1% were also recorded from fecal samples of the birds. Single cestode species Raillietina echinobothrida having parasitic prevalence of 27% and 3 protozoan species i.e. Eimeria maxima having prevalence 20.1%, Histomonas meleagridis 8% and Giardia lamblia 5.3% were recorded. In our recommendation, proper medication and sanitation of the bird's houses and cages is recommended to avoid parasites.

First records of prevalence and diversity of avian haemosporidia in snipe species (genus Gallinago) of Japan

Migratory birds are important carriers of pathogens such as viruses, bacteria and protozoa. Avian haemosporidia have been detected from many wild birds of Japan, but the infection status of migratory birds and transmission area are still largely unknown. Gallinago snipes are long-distance migratory shorebirds, and five species migrate to or through Japan, including Latham's snipe which is near threatened. Haemosporidian parasites in four snipe species were investigated to understand the role of migratory birds in the transmission of avian haemosporidia. Namely, this study aimed: i) to investigate differences in parasite prevalence and related factors explaining infection likelihood among these migratory species, ii) to explore the diversity in haemosporidian lineages and possible transmission areas, and iii) to assess the possibility of morphological effects of infection. Blood samples were collected from snipes caught in central and southwest Japan during migration. Parasites cytb gene DNA were detected via PCR-based testing, and detected lineages were phylogenetically analyzed. Additionally, factors related to prevalence and morphological effects of infection were statistically tested. 383 birds from four Gallinago snipe species were caught, showing higher overall prevalence of avian haemosporidia (17.8 %) than reported in other wader species in previous studies. This high infection rate is presumably due to increased contact with vector insects, resultant of environmental preferences. The prevalence of Plasmodium spp. Was higher in Swinhoe's snipes, while Haemoproteus spp. Was higher in Latham's snipes. These differences are thought to be related to ecological factors including habitat use, distribution and migratory route. Six lineages detected from juveniles indicate transmission between the breeding and sampling area. Contrary to expectations, a direct link between morphological features and haemosporidian parasite infection were not detected. These findings provide valuable information for conservation of this endangered migratory bird group. Further studies linking biological and parasitological research are anticipated to contribute to conservational actions.

Ectoparasite Load Is Reduced in Side-Blotched Lizards (Uta stansburiana) at Wind Farms: Implications for Oxidative Stress

AbstractWind-generated power is one of the fastest growing alternative energy strategies worldwide and will likely account for 20% of US energy production by 2030. The installation and maintenance of wind farms are associated with increased human activity and can generate noise pollution, disturb and fragment habitat, and even alter community composition and structure. These environmental and ecological changes can increase physiological stress for vertebrates and affect important life-history attributes, such as immune function. However, little is known about how wind farms influence physiology and disease or parasite resistance in nonvolant wildlife. Here, we test the notion that renewable wind farms increase physiological stress and correlated aspects of disease resistance (parasite load) in a common desert vertebrate, the side-blotched lizard (Uta stansburiana). We captured lizards from three wind farms and three undisturbed reference sites in the San Gorgonio Pass wind resource area in the Mojave Desert, California. We quantified individual external parasite loads and measured plasma antioxidant capacity and concentrations of reactive oxygen metabolites as a combined metric of oxidative stress. Contrary to our expectations, individuals at wind farm sites had significantly fewer external parasites than at undeveloped sites. Additionally, we found a slight positive correlation between parasite load and oxidative stress for individuals at wind farm sites but not at reference sites. Our results demonstrate a complex, potentially context-dependent relationship between stress physiology and disease resistance for lizards in anthropogenically disturbed environments. Understanding how wind farms affect the physiology and ecoimmunology of terrestrial fauna is necessary to mitigate the ecological costs of alternative energy development.

Interactive effects of biological, human and environmental factors on tick loads in Boran cattle in tropical drylands

Background

Tick-borne diseases (TBDs) are a serious threat to humans, wildlife and livestock, and cause severe economic losses in many tropical drylands. The effective control of TBDs has been constrained by limited understanding of what determines tick loads in animals. We tested interactive effects of several biological factors (sex, age and body condition), one environmental factor (rainfall) and one human factor (management type) on tick loads in animals.

Methods

We collected ticks on animals at four sampling sites in the semi-arid savanna area of Laikipia County, Kenya, of which two are commercial ranches and the other two are open pastoral grazing areas. From 2017 to 2019, we collected a total of 2038 ticks from 619 domestic animals from various cattle and camel herds and from 79 tranquilised wild animals.

Results

Generally, wild herbivores (zebras, rhinos and elephants) had higher tick loads than domestic animals. As 83% of the tick samples were taken from Boran cattle, we analysed tick load in these cattle in more detail. Boran cattle had high tick loads in the wet season, especially those animals in poor condition. No differences were found between female and male cattle, regardless of season. The calves had high tick loads during both the wet and dry seasons, whereas the sub-adult and adult cattle had less ticks during the dry season. Cattle on the intensively managed ranches had lower tick load than those in the transhumant management system.

Conclusion

These findings highlight the importance of establishing effective control of ticks on domestic animals in transhumant management systems as tick loads were high on these animals in both the wet and dry season.

Graphic abstract

Determinants of prevalence and co-infestation by ecto- and endoparasites in the Atlas day gecko, Quedenfeldtia trachyblepharus, an endemic species of Morocco

The present work was undertaken to investigate the occurrence of ectoparasites (mites and ticks) and endoparasites (haemogregarines and helminths) in the Atlas day gecko, Quedenfeldtia trachyblepharus (Boettger, 1874), a high-altitude Moroccan endemic lizard. The study examinated also the effect of some host parameters (age, sex, size, body condition), in addition to the season and altitude on the prevalence and intensity of parasite infestations. The study was conducted in three localities from May to September 2019. The results indicated that 35% of juvenile geckos were found to be parasited by one type of parasite. Contrarily, up to three types of parasites were detected in the adults. The prevalence of mite infestations was 48.02%, with a mean intensity of 11.80 ± 15.69. The patterns of mite infestations was found to be mainly related to the altitude, while the prevalence and intensity of infestations were linked to the host size, and to the sex and season, respectively. Larvae and nymphs of Ixodes ricinus (Linnaeus, 1758) were the only life stages infesting geckos, with a prevalence and mean intensity of infestations of 4.41% and 2.2 ± 1.48, respectively. The tick infestations observed were mainly related to the season. The prevalence and intensity of haemogregarine infections were, respectively, 7.92% and 0.24 ± 0.15. The altitude was found to be the only factor associated with this infection. This study also revealed the presence of one helminth genus, Spauligodon sp., with a prevalence and mean intensity of 12.33% and 1.46 ± 0.88, respectively. Spauligodon infestations was significantly associated with age, host size and altitude. This finding represents the first citation of this parasite in Quedenfeldtia genus. Our study indicated that there was no significant relationship between parasite load and geckos body condition, which suggested a stable interaction between the gecko and its parasites. However, it showed a difference of infection between the localities, which could be in relation with habitat conditions.

Prevalence and genetic diversity of avian haemosporidian parasites in wild bird species of the order Columbiformes

Diseases can play a role in species decline. Among them, haemosporidian parasites, vector-transmitted protozoan parasites, are known to constitute a risk for different avian species. However, the magnitude of haemosporidian infection in wild columbiform birds, including strongly decreasing European turtle doves, is largely unknown. We examined the prevalence and diversity of haemosporidian parasites Plasmodium, Leucocytozoon and subgenera Haemoproteus and Parahaemoproteus in six species of the order Columbiformes during breeding season and migration by applying nested PCR, one-step multiplex PCR assay and microscopy. We detected infections in 109 of the 259 screened individuals (42%), including 15 distinct haemosporidian mitochondrial cytochrome b lineages, representing five H. (Haemoproteus), two H. (Parahaemoproteus), five Leucocytozoon and three Plasmodium lineages. Five of these lineages have never been described before. We discriminated between single and mixed infections and determined host species-specific prevalence for each parasite genus. Observed differences among sampled host species are discussed with reference to behavioural characteristics, including nesting and migration strategy. Our results support previous suggestions that migratory birds have a higher prevalence and diversity of blood parasites than resident or short-distance migratory species. A phylogenetic reconstruction provided evidence for H. (Haemoproteus) as well as H. (Parahaemoproteus) infections in columbiform birds. Based on microscopic examination, we quantified parasitemia, indicating the probability of negative effects on the host. This study provides a large-scale baseline description of haemosporidian infections of wild birds belonging to the order Columbiformes sampled in the northern hemisphere. The results enable the monitoring of future changes in parasite transmission areas, distribution and diversity associated with global change, posing a potential risk for declining avian species as the European turtle dove.

Fatal avian malaria in captive Atlantic puffins (Fratercula arctica) in Switzerland

Avian malaria is a vector-borne disease caused by Plasmodium species, which may affect a broad spectrum of bird families worldwide. In most endemic and migratory birds, Plasmodium infections seem not to cause severe harm; however, non-indigenous species kept in human care such as penguins may experience high morbidity and mortality rates. Fatal avian malaria may also occur in other non-native seabirds such as puffins (Fratercula spp.), but reported cases are scarce. The aim of this study was to analyze seven cases of sudden death in captive Atlantic puffins (Fratercula arctica) at Berne Animal Park in Switzerland between 2010 and 2020, and to determine the involvement of haemosporidian parasites in the fatal outcome. In all cases, lymphoplasmacytic inflammation, necrotic lesions in several organs and presence of protozoan stages within tissues/erythrocytes or accumulation of iron-based pigment were observed histologically. A one-step multiplex PCR designed to simultaneously detect and discriminate haemosporidia belonging to the genera Plasmodium, Haemoproteus and Leucocytozoon, and a nested PCR detecting Plasmodium and Haemoproteus infections were performed on DNA extracted from formalin-fixed and paraffin-embedded (FFPE) or fresh liver and spleen tissues from five and two birds, respectively. Plasmodium spp. DNA was detected in the tissues from six of seven birds by the one-step multiplex PCR and in five of seven individuals by the nested PCR protocol. Direct sequencing of the amplification products allowed the molecular identification of Plasmodium relictum SGS1 as the involved species in three individuals and Plasmodium matutinum LINN1 in two of these fatal cases. In one bird, no haemosporidian DNA could be amplified from FFPE tissues despite of suggestive histopathological findings. These results indicate that avian malaria represents an important cause of death in captive puffins and it should be considered as a differential diagnosis in unclear or fatal cases in this threatened bird species.

Direct and indirect effects of multiple environmental stressors on fish health in human-altered rivers

Freshwater fish face multiple challenges in human-altered rivers such as trace metal contamination, temperature increase and parasitism. These multiple stressors could have unexpected interactive effects on fish health due to shared physiological pathways, but few studies investigated this question in wild fish populations. In this study, we compared 16 populations of gudgeon (Gobio occitaniae) distributed along perturbation gradients in human-altered rivers in the South of France. We tested the effects of single and combined stressors (i.e., metal contamination, temperature, parasitism) on key traits linked to fish health across different biological levels using a Structural Equation Modelling approach. Parasitism and temperature alone had limited deleterious effects on fish health. In contrast, fish living in metal-contaminated sites had higher metal bioaccumulation and higher levels of cellular damage in the liver through the induction of an inflammatory response. In addition, temperature and contamination had interactive negative effects on growth. These results suggest that trace metal contamination has deleterious effects on fish health at environmentally realistic concentrations and that temperature can modulate the effects of trace metals on fish growth. With this study, we hope to encourage integrative approaches in realistic field conditions to better predict the effects of natural and anthropogenic stressors on aquatic organisms.

Keds, the enigmatic flies and their role as vectors of pathogens

Hippoboscid flies (Diptera: Hippoboscidae), commonly known as keds or louse flies, have been for long time overlooked by the scientific community, and their vector role of infectious agents to humans and domestic animals has been scantly investigated. This is partly due to the fact that the host range for most species is primarily restricted to wildlife, being rarely reported on domestic animals and humans. This led to a scarce scientific knowledge about their biology, ecology, behaviour, epidemiology as well as vector competence. However, the life history of some hippoboscid species, e.g., Melophagus ovinus, Lipoptena cervi and Hippobosca equina, suggests that these ectoparasites are important candidates to vector infectious disease agents (e.g., Rickettsia spp., Borrelia spp., Bartonella spp., Anaplasma phagocytophilum, Theileria ovis). Indeed, the peculiar biological and behavioural traits (i.e., obligatory blood sucking and reproductive physiology) of many ked species make them a suitable pabulum for pathogen's multiplication and for their transmission to receptive hosts. Therefore, studies focusing on the ked bio-ecological aspects as well as on their vector role are advocated along with the control of keds affecting different animal species. This review discusses current information on keds, highlighting their importance as vectors of pathogens of medical and veterinary concern to all animal species, with a special focus on mammals.

Physiological and morphological correlates of blood parasite infection in urban and non-urban house sparrow populations

In the last decade, house sparrow populations have shown a general decline, especially in cities. Avian malaria has been recently suggested as one of the potential causes of this decline, and its detrimental effects could be exacerbated in urban habitats. It was initially thought that avian malaria parasites would not have large negative effects on wild birds because of their long co-evolution with their hosts. However, it is now well-documented that they can have detrimental effects at both the primo- and chronical infection stages. In this study, we examined avian malaria infection and its physiological and morphological consequences in four populations of wild house sparrows (2 urban and 2 rural). We did not find any relationship between the proportions of infected individuals and the urbanisation score calculated for our populations. However, we observed that the proportion of infected individuals increased during the course of the season, and that juveniles were less infected than adults. We did not detect a strong effect of malaria infection on physiological, morphological and condition indexes. Complex parasite dynamics and the presence of confounding factors could have masked the potential effects of infection. Thus, longitudinal and experimental studies are needed to understand the evolutionary ecology of this very common, but still poorly understood, wild bird parasite.

Persistence of avian haemosporidians in the wild: a case study to illustrate seasonal infection patterns in relation to host life stages

Infection patterns of avian haemosporidians result from the evolution of their associations with hosts, and can be shaped by multiple biotic factors. However, at the level of parasite species, few studies have investigated the details of the temporal dynamics of infection patterns in wild bird communities. We hereby studied a wild bird community in southern Sweden to investigate two generalist parasites (cyt b lineages PARUS1 and WW2) of the morphological species Haemoproteus majoris in their main host species (tits and warblers, respectively) to look for seasonal (spring to autumn) and age class related variation in infection patterns. For both lineages, we detected a similar temporal pattern in prevalence and infection intensity, with peak levels during the main nesting season in adults and a few weeks later in juveniles. Infections in juveniles were detected as soon as they started to be caught by mist nets, implying that they became infected when still in the nest or during the first weeks post-fledging. The initially high intensities in juveniles were followed by a significant decrease during the hatching year, emphasising the importance of studying haemosporidian infections in nestlings and fledglings. Both prevalence and infection intensity in adults increased from spring to early summer, either due to spring relapses or new infections. Both prevalence and infection intensity declined in adults at the time when independent juveniles of the respective species started to appear, suggesting that the rate of parasite withdrawal from blood exceeded the rates of new infections gained and relapses of previous infections. Prevalence in both juveniles and adults approached zero towards the end of the summer.

Demographic and reproductive associations with nematode infection in a long-lived mammal

Infection by macroparasites, such as nematodes, varies within vertebrate host systems; elevated infection is commonly observed in juveniles and males, and, for females, with different reproductive states. However, while such patterns are widely recognized in short-lived model systems, how they apply to long-lived hosts is comparatively understudied. Here, we investigated how infection varies with host age, sex, and female reproduction in a semi-captive population of individually marked Asian elephants Elephas maximus. We carried out 1,977 faecal egg counts (FECs) across five years to estimate nematode loads for 324 hosts. Infection patterns followed an established age-infection curve, whereby calves (5 years) exhibited the highest FECs and adults (45 years) the lowest. However, males and females had similar FECs across their long lifespan, despite distinct differences in life-history strategy and clear sexual dimorphism. Additionally, although mothers invest two years in pregnancy and a further three to five years into lactation, nematode load did not vary with four different measures of female reproduction. Our results provide a much-needed insight into the host-parasite dynamics of a long-lived host; determining host-specific associations with infection in such systems is important for broadening our knowledge of parasite ecology and provides practical applications for wildlife medicine and management.

Age-Related Brood Parasitism and Egg Rejection in Magpie Hosts

When the strength or nature of a host-parasite interaction changes over the host life cycle, the consequences of parasitism can depend on host population age structure. Avian brood parasites reduce hosts' breeding success, and host age may play a role in this interaction if younger hosts are more likely parasitized and/or less able to defend themselves. We analyzed whether the age of female magpie (Pica pica) hosts is associated with parasite attack or their ability to reject foreign eggs. We recorded parasitism and model egg rejection of known-age individuals over their lifetime and established whether the likelihood of parasitism or egg rejection changed with age or longevity. Parasitism probability did not change with female age, and there was a trend toward longer-lived females being less likely to be parasitized. However, model egg rejection probability increased with age for each individual female, and longer-lived females were more prone to reject model eggs. Most females in the population were young, and the majority of them accepted model eggs, suggesting that brood parasites exploiting younger host individuals are benefitting from a lower defense level of their hosts. Our results stress that the intensity of selection by brood parasites may be mediated by the age structure of host populations, a to-date neglected aspect in brood parasite-host research.

Transcriptome-wide analysis reveals different categories of response to a standardised immune challenge in a wild rodent

Individuals vary in their immune response and, as a result, some are more susceptible to infectious disease than others. Little is known about the nature of this individual variation in natural populations, or which components of immune pathways are most responsible, but defining this underlying landscape of variation is an essential first step to understanding the drivers of this variation and, ultimately, predicting the outcome of infection. We describe transcriptome-wide variation in response to a standardised immune challenge in wild field voles. We find that genes (hereafter 'markers') can be categorised into a limited number of types. For the majority of markers, the response of an individual is dependent on its baseline expression level, with significant enrichment in this category for conventional immune pathways. Another, moderately sized, category contains markers for which the responses of different individuals are also variable but independent of their baseline expression levels. This category lacks any enrichment for conventional immune pathways. We further identify markers which display particularly high individual variability in response, and could be used as markers of immune response in larger studies. Our work shows how a standardised challenge performed on a natural population can reveal the patterns of natural variation in immune response.

High prevalence and genetic diversity of Haemoproteus columbae (Haemosporida: Haemoproteidae) in feral pigeons Columba livia in Cape Town, South Africa

In this study, we explore blood parasite prevalence, infection intensity, and co-infection levels in an urban population of feral pigeons Columba livia in Cape Town. We analyze the effect of blood parasites on host body condition and the association between melanin expression in the host's plumage and parasite infection intensity and co-infection levels. Relating to the haemosporidian parasite itself, we study their genetic diversity by means of DNA barcoding (cytochrome b) and show the geographic and host distribution of related parasite lineages in pigeons worldwide. Blood from 195 C. livia individuals was collected from April to June 2018. Morphometric measurements and plumage melanism were recorded from every captured bird. Haemosporidian prevalence and infection intensity were determined by screening blood smears and parasite lineages by DNA sequencing. Prevalence of Haemoproteus spp. was high at 96.9%. The body condition of the hosts was negatively associated with infection intensity. However, infection intensity was unrelated to plumage melanism. The cytochrome b sequences revealed the presence of four Haemoproteus lineages in our population of pigeons, which show high levels of co-occurrence within individual birds. Three lineages (HAECOL1, COLIV03, COQUI05) belong to Haemoproteus columbae and differ only by 0.1% to 0.8% in the cytochrome b gene. Another lineage (COLIV06) differs by 8.3% from the latter ones and is not linked to a morphospecies, yet. No parasites of the genera Leucocytozoon and Plasmodium were detected.

Elucidating cryptic dynamics of Theileria communities in African buffalo using a high-throughput sequencing informatics approach

Increasing access to next-generation sequencing (NGS) technologies is revolutionizing the life sciences. In disease ecology, NGS-based methods have the potential to provide higher-resolution data on communities of parasites found in individual hosts as well as host populations.Here, we demonstrate how a novel analytical method, utilizing high-throughput sequencing of PCR amplicons, can be used to explore variation in blood-borne parasite (Theileria-Apicomplexa: Piroplasmida) communities of African buffalo at higher resolutions than has been obtained with conventional molecular tools.Results reveal temporal patterns of synchronized and opposite fluctuations of prevalence and relative abundance of Theileria spp. within the host population, suggesting heterogeneous transmission across taxa. Furthermore, we show that the community composition of Theileria spp. and their subtypes varies considerably between buffalo, with differences in composition reflected in mean and variance of overall parasitemia, thereby showing potential to elucidate previously unexplained contrasts in infection outcomes for host individuals.Importantly, our methods are generalizable as they can be utilized to describe blood-borne parasite communities in any host species. Furthermore, our methodological framework can be adapted to any parasite system given the appropriate genetic marker.The findings of this study demonstrate how a novel NGS-based analytical approach can provide fine-scale, quantitative data, unlocking opportunities for discovery in disease ecology.

Do ectoparasites affect survival of three species of lizards of the genus Sceloporus?

The short-term effects that ectoparasites cause to their hosts, such as local wounds and secondary infections that occur within a few hours or days after infection, are well documented in a wide variety of taxa, whereas long-term negative effects on the fitness of hosts, which result from chronic infections and are evident after several months, are less understood. Lizards are hosts of distinct species of mites and ticks that cause short-term negative effects such as ulcers, sores and local inflammation. However, the negative effects that these ectoparasites may have on the long-term survival of lizards have not been evaluated. In this study, we collected two years of capture-mark-recapture data and implemented a multi-model inference framework to examine if high ectoparasite loads have negative effects on the long-term survival probability of three lizard species of the genus Sceloporus (S. grammicus, S. megalepidurus, and S. torquatus). In addition, we considered that the potential negative effect of ectoparasites on survival may vary depending on sex, body condition, reproductive season, or climatic season. Contrary to our expectations, our results did not support the hypothesis that high ectoparasite loads reduce the survival probability of these lizards. In S. grammicus and S. megalepidurus we found no evidence of an effect of ectoparasite load on host survival. In S. torquatus ectoparasites influenced survival probability, but the effect was opposite to what we predicted: survival increased substantially as ectoparasite load increased. This unexpected result might be explained by mites discriminating between hosts and attaching more frequently to lizards in better health status, or by high-quality lizards having greater chances of contracting ectoparasites, because these individuals move around large areas and frequently engage in social interactions.

The evolution of stage-specific virulence: Differential selection of parasites in juveniles

The impact of infectious disease is often very different in juveniles and adults, but theory has focused on the drivers of stage-dependent defense in hosts rather than the potential for stage-dependent virulence evolution in parasites. Stage structure has the potential to be important to the evolution of pathogens because it exposes parasites to heterogeneous environments in terms of both host characteristics and transmission pathways. We develop a stage-structured (juvenile-adult) epidemiological model and examine the evolutionary outcomes of stage-specific virulence under the classic assumption of a transmission-virulence trade-off. We show that selection on virulence against adults remains consistent with the classic theory. However, the evolution of juvenile virulence is sensitive to both demography and transmission pathway with higher virulence against juveniles being favored either when the transmission pathway is assortative (juveniles preferentially interact together) and the juvenile stage is long, or in contrast when the transmission pathway is disassortative and the juvenile stage is short. These results highlight the potentially profound effects of host stage structure on determining parasite virulence in nature. This new perspective may have broad implications for both understanding and managing disease severity.

Blood parasites in Passeriformes in central Germany: prevalence and lineage diversity of Haemosporida (Haemoproteus, Plasmodium and Leucocytozoon) in six common songbirds

Background

Avian Haemosporida are vector-borne parasites that commonly infect Passeriformes. Molecular analyses revealed a high number of different lineages and lineage specific traits like prevalence and host-specificity, but knowledge of parasite prevalence and lineage diversity in wild birds in Central Germany is still lacking.

Results

Blood samples from a total of 238 adult and 122 nestling songbirds belonging to six species were investigated for infections with avian haemosporidian genera and lineages (Haemoproteus spp., Plasmodium spp., Leucocytozoon spp.) and Trypanosoma avium using PCR, targeting the parasite mitochondrial cytochrome b gene and 18S ribosomal RNA. In total, the prevalence in adult birds was 31.3% infected with Haemoproteus, 12.5% with Plasmodium and 71.0% with Leucocytozoon (nestlings excluded). None of the tested birds was infected with Trypanosoma avium. Only in two nestling birds, aged 12–17 days, a Leucocytozoon spp. infection was proven. Among 225 successfully sequenced samples, we found four Haemoproteus, three Plasmodium and 19 Leucocytozoon lineages, including two new Leucocytozoon lineages. Furthermore, we report two new host-lineage associations.

Conclusions

As first study investigating avian haemosporidian parasites in Central Germany, we provide new information on genetic diversity of Haemosporida infecting Passeriformes. We show that even with a small sample size new lineages as well as previously unknown linkages between certain lineages and host species can be detected. This may help to elucidate the diversity of lineages as well as lineage-host-connections of avian Haemosporida.

Age and infection history are revealed by different ornaments in a warbler

Female preference for older or more disease-resistant males are both possible outcomes of parasite-mediated sexual selection, but the extent to which infection alters the development of ornaments to yield signals of male age and health has rarely been explored. In a longitudinal study of 61 male common yellowthroats (Geothlypis trichas), age-related increases in the size of the melanin-based mask and carotenoid-based bib were not correlated among young males, likely owing to differences in how blood parasites affect ornament development. Infection with trypanosomes and hemosporidians in a male's first breeding season was associated with slower growth of the mask; uninfected males attained large masks in their second breeding season, while infected males attained large masks in their third breeding season. In contrast, the bib size of males increased every year regardless of infection. As a consequence, different populations of males are identified by the largest ornaments-older males in the case of bib and a combination of older males and young, uninfected males in the case of mask. Although mask is thus the more informative trait with respect to male health, females prefer large bibs in our population. If infection is opportunistic, young, uninfected males may not possess good genes for parasite resistance but simply good luck, and it may benefit females to prefer older males who are more likely to have withstood prior episodes of selection. A "pure" signal of age may be a more reliable signal of resistance to parasites than an ornament whose expression is modulated by infection.

Effects of breeding center, age and parasite burden on fecal triiodothyronine levels in forest musk deer

The objective of this study was to evaluate the effects of sex, breeding center and age on fecal triiodothyronine levels in captive forest musk deer Moschus berezovskii, and to explore the age-intensity model of gastrointestinal parasites. Furthermore, the association between fecal triiodothyronine levels and parasite egg shedding was also analyzed. We collected musk deer fecal samples from two breeding centers located in Shaanxi and Sichuan province, China. Enzyme-linked immunosorbent assays were utilized to estimate the fecal triiodothyronine concentrations and profiles, and fecal parasite eggs or oocysts were counted using the McMaster technique. Female deer from both breeding centers consistently showed higher triiodothyronine concentrations than those observed in males, which indicates that a distinct physiology pattern occurs by sex. The triiodothyronine concentration in Sichuan breeding center was significantly higher than that in Shaanxi center for both sexes, suggesting that differences in environment, diet and management practices are likely to affect the metabolism. In addition, a negative relationship between triiodothyronine concentrations and age was found (r = - 0.75, p < 0.001), and parasite egg shedding was also negatively associated with age (r = - 0.51, p < 0.001), by which we can infer that older animals evolves a more developed immune system. Finally, a positive association between parasite egg shedding and triiodothyronine levels was found, which could be explained by the additional energy metabolism resulting from parasitic infection. Results from this study might suggest metabolic and immunological adaptations in forest musk deer. These baseline data could be used to unveil metabolic status and establish parasite control strategies, which has great potential in captive population management as well as their general health evaluations.

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.

Links between blood parasites, blood chemistry, and the survival of nestling American crows

Many studies have used the avian hemosporidians (Leucocytozoon, Plasmodium, and Hemoproteus) to test hypotheses of host-parasite co-evolution, yet documented health and survival consequences of these blood parasites vary among studies and generalizations about their pathogenicity are debatable. In general, the negative effects of the hemosporidians are likely to be greatest during acute infections of young birds, yet most previous studies in wild passerines have examined chronic effects in adults. Here, we evaluated responses of nestling American crows (Corvus brachyrhynchos) to acute infection (prevalence and burden), as well as its short- and long-term survival consequences. We used panel of nine hematological and biochemical parameters that are regularly used to evaluate the health of domestic animals, including leukocyte profiles, hematocrit, and plasma proteins. We assessed the effects of infection on survival in a mark-recapture framework. Overall, 56% of crows (n = 321 samples) were infected by at least one of the three genera. Infections by all genera were associated with elevated plasma proteins and globulins, which could indicate an adaptive immune response. However, only Plasmodium infections were associated with low hematocrit (anemia) and lower fledging success, possibly mediated by the negative effect of low hematocrit values on body condition. Moreover, early Plasmodium infection (<40 days of age) had long-term survival implications: it was associated with lower apparent survival probability within 3 years after fledging. These results suggest that young crows mounted an adaptive immune response to all three genera. Short- and long-term pathological effects, however, were only apparent with Plasmodium infections.

Ecological drivers of Hepacivirus infection in a neotropical rodent inhabiting landscapes with various degrees of human environmental change

Anthropogenic environmental change can impact community and population traits such as species diversity and population densities, which have been shown to influence the prevalence of viruses in wildlife reservoirs. In particular, host species resilient to changes in their natural habitat may increase in numbers, which in turn can affect the prevalence of directly transmitted viruses. We have carried out a survey of small mammal communities in three tropical landscapes differing in their degree of environmental change in Central Panama and investigated the effects of community changes on Hepacivirus prevalence. The modification of continuous habitat into partly connected or isolated habitat patches during the past century was linked to changes in species diversity and species assemblages, which was further associated with shifts in the abundance of generalist marsupial (Didelphis marsupialis, Philander opossum) and rodent (Proechimys semispinosus) species. The latter has become dominant in isolated habitat patches and was the only identified Hepacivirus host in our study system. Our analyses suggest that, in addition to the effects of host age and sex, host population density in interaction with sex ratio is a crucial predictor of infection probability. Although we found no significant relationships between species diversity per se and infection probability, the lowest prevalence detected in the landscape with the highest species diversity indicates that shifts in species assemblages (e.g. changes in the presence and abundance of marsupial predators) impact the host's intraspecific contact rates, the probability of virus transmission and, thus, the virus prevalence. Our study additionally provides important data on the influence of human-induced landscape changes on infection probability and, therefore, on virus prevalence in wildlife and emphasizes the importance of a landscape-scale approach with concomitant consideration of the complex interactions between ecological factors.

Can the intake of antiparasitic secondary metabolites explain the low prevalence of hemoparasites among wild Psittaciformes?

Background

Parasites can exert selection pressure on their hosts through effects on survival, on reproductive success, on sexually selected ornament, with important ecological and evolutionary consequences, such as changes in population viability. Consequently, hemoparasites have become the focus of recent avian studies. Infection varies significantly among taxa. Various factors might explain the differences in infection among taxa, including habitat, climate, host density, the presence of vectors, life history and immune defence. Feeding behaviour can also be relevant both through increased exposure to vectors and consumption of secondary metabolites with preventative or therapeutic effects that can reduce parasite load. However, the latter has been little investigated. Psittaciformes (parrots and cockatoos) are a good model to investigate these topics, as they are known to use biological control against ectoparasites and to feed on toxic food. We investigated the presence of avian malaria parasites (Plasmodium), intracellular haemosporidians (Haemoproteus, Leucocytozoon), unicellular flagellate protozoans (Trypanosoma) and microfilariae in 19 Psittaciformes species from a range of habitats in the Indo-Malayan, Australasian and Neotropical regions. We gathered additional data on hemoparasites in wild Psittaciformes from the literature. We considered factors that may control the presence of hemoparasites in the Psittaciformes, compiling information on diet, habitat, and climate. Furthermore, we investigated the role of diet in providing antiparasitic secondary metabolites that could be used as self-medication to reduce parasite load.

Results

We found hemoparasites in only two of 19 species sampled. Among them, all species that consume at least one food item known for its secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, were free from hemoparasites. In contrast, the infected parrots do not consume food items with antimalarial or even general antiparasitic properties. We found that the two infected species in this study consumed omnivorous diets. When we combined our data with data from studies previously investigating blood parasites in wild parrots, the positive relationship between omnivorous diets and hemoparasite infestation was confirmed. Individuals from open habitats were less infected than those from forests.

Conclusions

The consumption of food items known for their secondary metabolites with antimalarial, trypanocidal or general antiparasitic properties, as well as the higher proportion of infected species among omnivorous parrots, could explain the low prevalence of hemoparasites reported in many vertebrates.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2940-3) contains supplementary material, which is available to authorized users.

Molecular characterization of avian malaria in the spotless starling (Sturnus unicolor)

We studied the prevalence and genetic diversity of malaria parasites in the poorly investigated spotless starling (Sturnus unicolor) breeding in central Spain, aiming to describe the phylogenetic relationships among them and with other haemosporidians infecting the genus Sturnus. A total of 180 nestlings and 180 adult individuals from four different breeding seasons were screened for haemosporidian parasites using a nested PCR approach for the genera Plasmodium and Haemoproteus. Although the malaria prevalence ranged between years, the overall prevalence was 6.94%. Adults had a higher prevalence than chicks: 12.77 vs. 1.11%, respectively. We molecularly characterized avian malaria isolated in peripheral blood samples taken from malaria-infected individuals. Sequence analyses revealed four unique Plasmodium lineages of avian malaria (STURUNI01, STURUNI02, SYAT05, SGS1) in our spotless starling population. The phylogenetic analysis showed a well-supported clade comprised by STURUNI01, STURUNI02, and SYAT05. The most common lineage (SYAT05) has been previously found in 26 other avian host species, including populations of spotless starling in Portugal. Because this sedentary species is widely distributed throughout the Iberian Peninsula, we suggest that the local transmission of these lineages might place migratory birds at infection risk.

How do seasonality and host traits influence the distribution patterns of parasites on juveniles and adults of Columba livia?

Parasites may influence host fitness and consequently exert a selective pressure on distinct phenotypes of the host population. This pressure can result in an evolutionary response, maintaining only individuals with certain traits in the population. The present study was aimed at identifying the morphological characteristics of juveniles and adults of Columba livia that may influence the distribution patterns of lice, Pseudolynchia canariensis and Haemoproteus columbae and how the populations of these parasites vary throughout the seasons of the year. Between July 2012 and July 2014, 377 specimens of C. livia were captured. We observed a significant increase in the mean intensities of infestation by pigeon flies and lice, as well as in species richness of ectoparasites during the warmest seasons, suggesting a reproductive synchrony between ectoparasites and host species. Bill length, body mass, and body length did not affect the infestation levels of ectoparasites on adults and juveniles of C. livia with three distinct plumage colors. In juveniles, plumage color affected only the mean intensity of infestation by lice, with Spread individuals as the most infested. This indicates that melanin in feathers was not an effective barrier against ectoparasites.

Parasite-associated mortality in a long-lived mammal: Variation with host age, sex, and reproduction

Parasites can cause severe host morbidity and threaten survival. As parasites are generally aggregated within certain host demographics, they are likely to affect a small proportion of the entire population, with specific hosts being at particular risk. However, little is known as to whether increased host mortality from parasitic causes is experienced by specific host demographics. Outside of theoretical studies, there is a paucity of literature concerning dynamics of parasite-associated host mortality. Empirical evidence mainly focuses on short-lived hosts or model systems, with data lacking from long-lived wild or semi-wild vertebrate populations. We investigated parasite-associated mortality utilizing a multigenerational database of mortality, health, and reproductive data for over 4,000 semi-captive timber elephants (Elephas maximus), with known causes of death for mortality events. We determined variation in mortality according to a number of host traits that are commonly associated with variation in parasitism within mammals: age, sex, and reproductive investment in females. We found that potentially parasite-associated mortality varied significantly across elephant ages, with individuals at extremes of lifespan (young and old) at highest risk. Mortality probability was significantly higher for males across all ages. Female reproducers experienced a lower probability of potentially parasite-associated mortality than females who did not reproduce at any investigated time frame. Our results demonstrate increased potentially parasite-associated mortality within particular demographic groups. These groups (males, juveniles, elderly adults) have been identified in other studies as susceptible to parasitism, stressing the need for further work investigating links between infection and mortality. Furthermore, we show variation between reproductive and non-reproductive females, with mothers being less at risk of potentially parasite mortality than nonreproducers.

Temporal and demographic blood parasite dynamics in two free-ranging neotropical primates

Parasite-host relationships are influenced by several factors intrinsic to hosts, such as social standing, group membership, sex, and age. However, in wild populations, temporal variation in parasite distributions and concomitant infections can alter these patterns. We used microscropy and molecular methods to screen for naturally occurring haemoparasitic infections in two Neotropical primate host populations, the saddleback (Leontocebus weddelli) and emperor (Saguinus imperator) tamarin, in the lowland tropical rainforests of southeastern Peru. Repeat sampling was conducted from known individuals over a three-year period to test for parasite-host and parasite-parasite associations. Three parasites were detected in L. weddelli including Trypanosoma minasense, Mansonella mariae, and Dipetalonema spp., while S. imperator only hosted the latter two. Temporal variation in prevalence was observed in T. minasense and Dipetalonema spp., confirming the necessity of a multi-year study to evaluate parasite-host relationships in this system. Although callitrichids display a distinct reproductive dominance hierarchy, characterized by single breeding females that typically mate polyandrously and can suppress the reproduction of subdominant females, logistic models did not identify sex or breeding status as determining factors in the presence of these parasites. However, age class had a positive effect on infection with M. mariae and T. minasense, and adults demonstrated higher parasite species richness than juveniles or sub-adults across both species. Body weight had a positive effect on the presence of Dipetalonema spp. The inclusion of co-infection variables in statistical models of parasite presence/absence data improved model fit for two of three parasites. This study verifies the importance and need for broad spectrum and long-term screening of parasite assemblages of natural host populations.

Haemosporidian infections affect antioxidant defences in great tits Parus major but are not related to exposure to aerial pollutants

Haemosporidian parasites are widespread in avian species and modulate their ecology, behaviour, life-history and fitness. The prevalence of these vector-transmitted parasites varies with host intrinsic and extrinsic factors, such as host resistance and behaviour, and habitat-related characteristics. In this study, we evaluated the prevalence of avian haemosporidians in great tit Parus major populations inhabiting two areas with different degrees of exposure to aerial emissions from pulp mills, to assess if this type of pollution impacted parasite prevalence. We also compared the physiological condition of infected and uninfected individuals. Haemosporidian infection prevalence was high (58%), varied seasonally, but was not associated with air pollution exposure. Fledged birds presented higher infection rates than nestlings and infected fledged birds had higher levels of blood glutathione peroxidase activity. These results allow us to infer that infection by blood parasites may activate antioxidant defences, possibly to protect the organism from the negative oxidative stress side-effects of immune activation against parasites. Because oxidative stress is one of the mechanisms responsible for ageing and senescence and may affect fitness, the relationship between parasitism and oxidative stress markers should be further investigated through studies that include experimental manipulation of infection in model organisms.

Presence of Vaccine-Derived Newcastle Disease Viruses in Wild Birds

Our study demonstrates the repeated isolation of vaccine-derived Newcastle disease viruses from different species of wild birds across four continents from 1997 through 2014. The data indicate that at least 17 species from ten avian orders occupying different habitats excrete vaccine-derived Newcastle disease viruses. The most frequently reported isolates were detected among individuals in the order Columbiformes (n = 23), followed in frequency by the order Anseriformes (n = 13). Samples were isolated from both free-ranging (n = 47) and wild birds kept in captivity (n = 7). The number of recovered vaccine-derived viruses corresponded with the most widely utilized vaccines, LaSota (n = 28) and Hitchner B1 (n = 19). Other detected vaccine-derived viruses resembled the PHY-LMV2 and V4 vaccines, with five and two cases, respectively. These results and the ubiquitous and synanthropic nature of wild pigeons highlight their potential role as indicator species for the presence of Newcastle disease virus of low virulence in the environment. The reverse spillover of live agents from domestic animals to wildlife as a result of the expansion of livestock industries employing massive amounts of live virus vaccines represent an underappreciated and poorly studied effect of human activity on wildlife.

Sex-dependent differences in avian malaria prevalence and consequences of infections on nestling growth and adult condition in the Tawny pipit, Anthus campestris

BACKGROUND

Parasites play pivotal roles in host population dynamics and can have strong ecological impacts on hosts. Knowledge of the effects of parasites on hosts is often limited by the general observation of a fraction of individuals (mostly adults) within a population. The aim of this study was to assess the prevalence of malaria parasites in adult (≥ 1 year old) and nestling (7-11 day old) Tawny pipits Anthus campestris, to evaluate the influence of the host sex on parasite prevalence in both groups of age, and explore the association between infections and body condition (adults) and growth (nestlings).

METHODS

Two hundred Tawny pipits (105 adults and 95 nestlings) from one Spanish population were screened for avian malaria parasites (Haemoproteus and Plasmodium) using the polymerase chain reaction (PCR)-based methods. Body condition (body mass against a linear measure of size) was measured in adults and growth rate (daily mass gain) was calculated for nestlings.

RESULTS

The overall prevalence of infection was 46%. Sixteen different mitochondrial cytochrome b haplotypes of Plasmodium spp. and one Haemoproteus spp. haplotype were found. Malaria parasites were equally prevalent in nestlings and adults (45 and 46%, respectively). Males were more likely to be infected by parasites than females, and this sex-bias parasitism was evident in both adults and nestlings. Furthermore, a lower daily mass gain during nestling growth in males than in females following infections were found, whereas the effect of infections on body condition of adults was detrimental for females but not for males.

CONCLUSIONS

Age-specific differences in physiological trade-offs and ecological factors, such as nest predation would explain, at least in part, the observed host sex and age-related patterns in Tawny pipits.

Genetic diversity, temporal dynamics, and host specificity in blood parasites of passerines in north China

Avian blood parasites have been preliminarily studied in East Asia, but no data are available from long-term monitoring. The aim of this study was to evaluate the prevalence, genetic diversity, and temporal dynamics of Plasmodium, Haemoproteus, and Leucocytozoon in two passerine communities (one forest and one urban) in north China from 2008 to 2013, as well as the association between infected lineages and host specificities. Out of 633 birds from 40 species, 157 individuals (24.8 %) were infected; overall prevalence was 26.7 % and 16.8 % in two sites, respectively. The dominant avian blood parasite genus in the forest park changed yearly between Plasmodium and Haemoproteus, while the Leucocytozoon maintained a low infection level. Forty-four haplotypes were identified by sequencing a 432-bp fragment of the cytochrome b (cyt b) gene; more than 70 % were novel (six Plasmodium lineages, 16 Haemoproteus lineages, and nine Leucocytozoon lineages). Based on our data gathered over consecutive years, we found that the highly observed lineages of Haemoproteus showed higher host diversities than those of Plasmodium, and the most infected lineage EMEL01 (100 % identity with SGS1) take on the highest host diversity but low temporal diversity of the two genera, implying that this lineage infected a great diversity of species in certain years, but maintained a lower infection level or even disappeared in other years. The results suggest that genetic diversity of avian blood parasites in East Asia is high and provides scope for further research. In addition, compared with overall analysis, yearly prevalence monitoring is important in uncovering the temporal dynamic and host specificity variations over time.

Biogeography of Parasitic Nematode Communities in the Galápagos Giant Tortoise: Implications for Conservation Management

The Galápagos giant tortoise is an icon of the unique, endemic biodiversity of Galápagos, but little is known of its parasitic fauna. We assessed the diversity of parasitic nematode communities and their spatial distributions within four wild tortoise populations comprising three species across three Galápagos islands, and consider their implication for Galápagos tortoise conservation programmes. Coprological examinations revealed nematode eggs to be common, with more than 80% of tortoises infected within each wild population. Faecal samples from tortoises within captive breeding centres on Santa Cruz, Isabela and San Cristobal islands also were examined. Five different nematode egg types were identified: oxyuroid, ascarid, trichurid and two types of strongyle. Sequencing of the 18S small-subunit ribosomal RNA gene from adult nematodes passed with faeces identified novel sequences indicative of rhabditid and ascaridid species. In the wild, the composition of nematode communities varied according to tortoise species, which co-varied with island, but nematode diversity and abundance were reduced or altered in captive-reared animals. Evolutionary and ecological factors are likely responsible for the variation in nematode distributions in the wild. This possible species/island-parasite co-evolution has not been considered previously for Galápagos tortoises. We recommend that conservation efforts, such as the current Galápagos tortoise captive breeding/rearing and release programme, be managed with respect to parasite biogeography and host-parasite co-evolutionary processes in addition to the biogeography of the host.