Avian Plasmodium in Culex and Ochlerotatus Mosquitoes from Southern Spain: Effects of Season and Host-Feeding Source on Parasite Dynamics

Molecular detection of parasites and host preference in wild-caught Culicoides biting midges (Diptera: Ceratopogonidae) in Chiang Mai and Nakhon Si Thammarat Provinces, Thailand

Culicoides biting midges (Diptera: Ceratopogonidae) have been reported as potential vectors for haemoparasites. Information about host-vector-parasite specificity is required to confirm their status. Here, molecular detection of haemosporidians, Leishmania, trypanosomatids, and filarial nematodes in biting midges was conducted to understand their potential role as vectors, and their host preference was determined. Wild-caught biting midges were collected from six different localities of Chiang Mai and Nakhon Si Thammarat provinces, Thailand. A total of 6,578 individual Culicoides (170 males, 6,408 females) comprising 15 species of six sub-genera and two groups were collected. Also, 738 parous females and 29 engorged females were examined for parasites and host blood meals, respectively. Culicoides arakawae, C. mahasarakhamense, C. peregrinus and C. innoxius in Chiang Mai province, and C. innoxius and C. peregrinus in Nakhon Si Thammarat province were the most dominant species. Leucocytozoon spp., Leucocytozoon caulleryi and Plasmodium juxtanucleare were identified in five Culicoides species including C. mahasarakhamense, C. arakawae, C. oxystoma, C. fulvus, and C. guttifer. This study is the first record of L. caulleryi in the biting midge C. arakawae in Thailand. Blood meal analysis revealed that Culicoides primarily fed on cattle (17/29, 58.6%), followed by chickens (10/29, 34.5%), and humans (2/29, 6.9%). Our findings confirmed the existence of several Culicoides species in Thailand, which might be potential vectors for transmission of haemosporidians (Leucocytozoon and Plasmodium). Information from host blood meal analyses underlined their preference for large mammals, followed by domestic chickens. More anthropophilic Culicoides species remain to be discovered.

Diversity and Host Specificity of Avian Haemosporidians in an Afrotropical Conservation Region

Afrotropical regions have high bird diversity, yet few studies have attempted to unravel the prevalence of avian haemosporidia in conservation areas. The diversity and host specificity of parasites in biodiversity hotspots is crucial to understanding parasite distribution and potential disease emergence. We test the hypothesis that biodiverse regions are associated with highly diverse parasites. By targeting the cytochrome b (Cytb) gene, we molecularly screened 1035 blood samples from 55 bird species for avian haemosporidia infections to determine its prevalence and diversity on sites inside and adjacent to the Kruger National Park. Overall infection prevalence was 28.41%. Haemoproteus, Leucocytozoon, and Plasmodium presented prevalences of 17.39%, 9.24%, and 4.64%, respectively. One hundred distinct parasite lineages were detected, of which 56 were new lineages. Haemoproteus also presented the highest diversity compared to Leucocytozoon and Plasmodium with varying levels of specificity. Haemoproteus lineages were found to be specialists while Plasmodium and Leucocytozoon lineages were generalists. We also found a positive relationship between avian host diversity and parasite diversity, supporting an amplification effect. These findings provide insight data for host-parasite and co-evolutionary relationship models.

Avian haemosporidian parasites from wild-caught mosquitoes with new evidence on vectors of Plasmodium matutinum

Avian haemosporidian parasites are spread worldwide and pose a threat to their hosts occasionally. A complete life cycle of these parasites requires two hosts: vertebrate and invertebrate (a blood-sucking insect that acts as a vector). In this study, we tested wild-caught mosquitoes for haemosporidian infections. Mosquitoes were collected (2021-2023) in several localities in Lithuania using a sweeping net and a CDC trap baited with CO2, morphologically identified, and preparations of salivary glands were prepared (from females collected in 2022-2023). 2093 DNA samples from either individual after dissection (1675) or pools (418 pools/1145 individuals) of female mosquito's abdomens were screened using PCR for the detection of haemosporidian parasite DNA. Salivary gland preparations were analyzed microscopically from each PCR-positive mosquito caught in 2022 and 2023. The average prevalence of haemosporidian parasites for all analyzed samples was 2.0 % and varied between 0.6 % (2021) and 3.5 % (2022). DNA of Plasmodium ashfordi (cytochrome b genetic lineage pGRW02), P. circumflexum (pTURDUS1), P. homonucleophilum (pSW2), P. matutinum (pLINN1), P. vaughani (pSYAT05), Haemoproteus brachiatus (hLK03), H. majoris (hWW2), and H. minutus (hTUPHI01) were detected in mosquitoes. Coquilletidia richiardii (3.5 %) and Culex pipiens (2.9 %) were mosquito species with the highest prevalence of haemosporidian parasite DNA detected. Mixed infections were detected in 16 mosquitoes. In one of the samples, sporozoites of P. matutinum (pLINN1) were found in the salivary gland preparation of Culex pipiens, confirming this mosquito species as a competent vector of Plasmodium matutinum and adding it to the list of the natural vectors of this avian parasite.

A Literature Review on the Role of the Invasive Aedes albopictus in the Transmission of Avian Malaria Parasites

The Asian tiger mosquito (Aedes albopictus) is an invasive mosquito species with a global distribution. This species has populations established in most continents, being considered one of the 100 most dangerous invasive species. Invasions of mosquitoes such as Ae. albopictus could facilitate local transmission of pathogens, impacting the epidemiology of some mosquito-borne diseases. Aedes albopictus is a vector of several pathogens affecting humans, including viruses such as dengue virus, Zika virus and Chikungunya virus, as well as parasites such as Dirofilaria. However, information about its competence for the transmission of parasites affecting wildlife, such as avian malaria parasites, is limited. In this literature review, we aim to explore the current knowledge about the relationships between Ae. albopictus and avian Plasmodium to understand the role of this mosquito species in avian malaria transmission. The prevalence of avian Plasmodium in field-collected Ae. albopictus is generally low, although studies have been conducted in a small proportion of the affected countries. In addition, the competence of Ae. albopictus for the transmission of avian malaria parasites has been only proved for certain Plasmodium morphospecies under laboratory conditions. Therefore, Ae. albopictus may play a minor role in avian Plasmodium transmission in the wild, likely due to its mammal-biased blood-feeding pattern and its reduced competence for the development of different avian Plasmodium. However, further studies considering other avian Plasmodium species and lineages circulating under natural conditions should be carried out to properly assess the vectorial role of Ae. albopictus for the Plasmodium species naturally circulating in its distribution range.

Host preference patterns in domestic and wild settings: Insights into Anopheles feeding behavior

The adaptation of Anopheles malaria vectors to domestic settings is directly linked to their ability to feed on humans. The strength of this species-habitat association is unequal across the species within the genus, with the major vectors being particularly dependent on humans. However, our understanding of how blood-feeding behavior interacts with and adapts to environmental settings, including the presence of humans, remains limited. Using a field-based approach, we first investigated Anopheles community structure and feeding behavior patterns in domestic and sylvatic settings in La Lopé National Park in Gabon, Central Africa. We characterized the preference indices using a dual-host choice sampling approach across mosquito species, habitats, and seasons. We then quantified the plastic biting behavior of mosquito species in each habitat. We collected individuals from 16 Anopheles species that exhibited significant differences in species composition and abundance between sylvatic and domestic settings. The host-seeking behavior also varied among the seven most abundant species. The general attractiveness to each host, human or animal, remained relatively constant for each species, but with significant variations between habitats across species. These variations, to more generalist and to more anthropophilic behavior, were related to seasonal changes and distance from the village, respectively. Finally, we pointed out that the host choice of major malaria vectors changed in the absence of humans, revealing a plastic feeding behavior of these species. This study highlights the effect of humans on Anopheles distribution and feeding evolution. The characterization of feeding behavior in wild and domestic settings provides opportunities to better understand the interplay between genetic determinants of host preference and ecological factors. Our findings suggest that protected areas may offer alternative thriving conditions to major malaria vectors.

New insight into avian malaria vectors in New Zealand

BACKGROUND

Mosquitoes (Culicidae) are vectors for most malaria parasites of the Plasmodium species and are required for Plasmodium spp. to complete their life cycle. Despite having 16 species of mosquitoes and the detection of many Plasmodium species in birds, little is known about the role of different mosquito species in the avian malaria life cycle in New Zealand.

METHODS

In this study, we used nested polymerase chain reaction (PCR) and real-time PCR to determine Plasmodium spp. prevalence and diversity of mitochondrial cytochrome b gene sequences in wild-caught mosquitoes sampled across ten sites on the North Island of New Zealand during 2012-2014. The mosquitoes were pooled by species and location collected, and the thorax and abdomens were examined separately for Plasmodium spp. DNA. Akaike information criterion (AIC) modeling was used to test whether location, year of sampling, and mosquito species were significant predictors of minimum infection rates (MIR).

RESULTS

We collected 788 unengorged mosquitoes of six species, both native and introduced. The most frequently caught mosquito species were the introduced Aedes notoscriptus and the native Culex pervigilans. Plasmodium sp DNA was detected in 37% of matched thorax and abdomen pools. When considered separately, 33% of abdomen and 23% of thorax pools tested positive by nested PCR. The MIR of the positive thorax pools from introduced mosquito species was 1.79% for Ae. notoscriptus and 0% for Cx. quinquefasciatus, while the MIR for the positive thorax pools of native mosquito species was 4.9% for Cx. pervigilans and 0% for Opifex fuscus. For the overall MIR, site and mosquito species were significant predictors of Plasmodium overall MIR. Aedes notoscriptus and Cx. pervigilans were positive for malaria DNA in the thorax samples, indicating that they may play a role as avian malaria vectors. Four different Plasmodium lineages (SYAT05, LINN1, GRW6, and a new lineage of P (Haemamoeba) sp. AENOT11) were identified in the pooled samples.

CONCLUSIONS

This is the first detection of avian Plasmodium DNA extracted from thoraxes of native Culex and introduced Aedes mosquito species in New Zealand and therefore the first study providing an indication of potential vectors in this country.

Landscape and mosquito community impact the avian Plasmodium infection in Culex pipiens

Avian malaria parasites provide an important model for studying host-pathogen interactions, yet understanding their dynamics in vectors under natural conditions is limited. We investigated the effect of vector abundance, species richness and diversity, and habitat characteristics on avian Plasmodium prevalence and lineage richness in Culex pipiens across 45 urban, natural, and rural localities in southern Spain. Analyzing 16,574 mosquitoes grouped in 768 mosquito pools, 32.7% exhibited parasite presence. 13 different Plasmodium lineages were identified, with the lineage SYAT05 being the most commonly found. Parasite prevalence positively correlated with the distance to saltmarshes and rivers, but negatively with the distance to total water source. Parasite lineage diversity was higher in natural than in rural areas and positively correlated with mosquito species richness. These results emphasize the complex dynamics of avian Plasmodium in the wild, with habitat characteristics and vector community driving the parasite transmission by mosquito vectors.

Implications of migratory and exotic birds and the mosquito community on West Nile virus transmission

BACKGROUND

Vector-borne diseases like West Nile virus (WNV) pose a global health challenge, with rising incidence and distribution. Culex mosquitoes are crucial WNV vectors. Avian species composition and bird community diversity, along with vector communities, influence WNV transmission patterns. However, limited knowledge exists on their impact in southwestern Spain, an area with active WNV circulation in wild birds, mosquitoes, and humans.

METHODS

To address this, we conducted a comprehensive study investigating the contributions of migratory and exotic bird species to WNV transmission and the influence of mosquito community composition.

RESULTS

Analysing 1194 serum samples from 44 avian species, we detected WNV antibodies in 32 samples from 11 species, four for the first time in Europe. Migratory birds had higher WNV exposure likelihood than native and exotic species, and higher phylogenetic diversity in bird communities correlated with lower exposure rates. Moreover, in 5859 female mosquitoes belonging to 12 species, we identified WNV competent vectors like Cx. pipiens s.l. and the Univittatus subgroup. Birds with WNV antibodies were positively associated with competent vector abundance, but negatively with overall mosquito species richness.

CONCLUSIONS

These findings highlight the complex interactions between bird species, their phylogenetics, and mosquito vectors in WNV transmission. Understanding these dynamics will help to implement effective disease control strategies in southwestern Spain.

Avian Plasmodium in invasive and native mosquitoes from southern Spain

BACKGROUND

The emergence of diseases of public health concern is enhanced by factors associated with global change, such as the introduction of invasive species. The Asian tiger mosquito (Aedes albopictus), considered a competent vector of different viruses and parasites, has been successfully introduced into Europe in recent decades. Molecular screening of parasites in mosquitoes (i.e. molecular xenomonitoring) is essential to understand the potential role of different native and invasive mosquito species in the local circulation of vector-borne parasites affecting both humans and wildlife.

METHODS

The presence of avian Plasmodium parasites was molecularly tested in mosquitoes trapped in five localities with different environmental characteristics in southern Spain from May to November 2022. The species analyzed included the native Culex pipiens and Culiseta longiareolata and the invasive Ae. albopictus.

RESULTS

Avian Plasmodium DNA was only found in Cx. pipiens with 31 positive out of 165 mosquito pools tested. None of the Ae. albopictus or Cs. longiareolata pools were positive for avian malaria parasites. Overall, eight Plasmodium lineages were identified, including a new lineage described here. No significant differences in parasite prevalence were found between localities or sampling sessions.

CONCLUSIONS

Unlike the invasive Ae. albopictus, Cx. pipiens plays a key role in the transmission of avian Plasmodium in southern Spain. However, due to the recent establishment of Ae. albopictus in the area, further research on the role of this species in the local transmission of vector-borne pathogens with different reservoirs is required.

An overview of the mosquitoes of Saudi Arabia (Diptera: Culicidae), with updated keys to the adult females

Despite the fact that mosquito-borne infections have considerable consequences for public health in Saudi Arabia, there is neither a thorough review of the species that occur in the country nor updated keys for the identification of the adult females. In this study, species accounts are given for 49 Saudi Arabian mosquito species, as well as Aedes albopictus (Skuse), which is not recorded in Saudi Arabia, but is medically important and is found in some countries of the Middle East and North Africa. Taxonomic notes provide additional information for certain taxa and/or aid their identification.

Unravelling the mosquito-haemosporidian parasite-bird host network in the southwestern Iberian Peninsula: insights into malaria infections, mosquito community and feeding preferences

BAKGROUND

Vector-borne diseases affecting humans, wildlife and livestock have significantly increased their incidence and distribution in the last decades. Because the interaction among vectors-parasite-vertebrate hosts plays a key role driving vector-borne disease transmission, the analyses of the diversity and structure of vector-parasite networks and host-feeding preference may help to assess disease risk. Also, the study of seasonal variations in the structure and composition of vector and parasite communities may elucidate the current patterns of parasite persistence and spread as well as facilitate prediction of how climate variations may impact vector-borne disease transmission. Avian malaria and related haemosporidian parasites constitute an exceptional model to understand the ecology and evolution of vector-borne diseases. However, the characterization of vector-haemosporidian parasite-bird host assemblages is largely unknown in many regions.

METHODS

Here, we analyzed 5859 female mosquitoes captured from May to November in five localities from southwestern Spain to explore the composition and seasonal variation of the vector-parasite-vertebrate host network.

RESULTS

We showed a gradual increase in mosquito abundance, peaking in July. A total of 16 different haemosporidian lineages were found infecting 13 mosquito species. Of these assemblages, more than 70% of these vector-parasite associations have not been described in previous studies. Moreover, three Haemoproteus lineages were reported for the first time in this study. The prevalence of avian malaria infections in mosquitoes varied significantly across the months, reaching a maximum in November. Mosquito blood-feeding preference was higher for mammals (62.5%), whereas 37.5% of vectors fed on birds, suggesting opportunistic feeding behavior.

CONCLUSION

These outcomes improve our understanding of disease transmission risk and help tovector control strategies.

Culex modestus: the overlooked mosquito vector

Culex (Barraudius) modestus (Ficalbi 1889) are found in temperate regions across Europe, Asia, and Northern Africa. These mosquitoes thrive during the summer and prefer to breed in permanent vegetative habitats such as rice paddies and marshes. Culex modestus feed on a wide range of bird species but are highly attracted to humans, which makes them a potential 'bridge' vector for enzootic pathogens. There is compelling evidence that Culex modestus is an efficient vector for West Nile virus, potentially capable of causing epidemics in humans and other mammals. This species is also a likely vector for Usutu virus, avian malaria (Plasmodium spp.), and parasitic heartworms (Dirofilaria spp.). Culex modestus can be morphologically identified at the larval and adult stages, and a distinctive phenotype of this species is their ability to overwinter. Despite the widespread establishment of this mosquito species and their role as vectors for human pathogens, we lack sufficient knowledge on this species to implement and evaluate targeted vector control measures. Since Culex modestus can be considered a potential public health threat, there is a need for a better understanding of this mosquito species.

Spatial distribution and temporal dynamics of invasive and native mosquitoes in a large Mediterranean city

Mosquitoes, including invasive species like the Asian tiger mosquito Aedes albopictus, alongside native species Culex pipiens s.l., pose a significant nuisance to humans and serve as vectors for mosquito-borne diseases in urban areas. Understanding the impact of water infrastructure characteristics, climatic conditions, and management strategies on mosquito occurrence and effectiveness of control measures to assess their implications on mosquito occurrence is crucial for effective vector control. In this study, we examined data collected during the local vector control program in Barcelona, Spain, focusing on 234,225 visits to 31,334 different sewers, as well as 1817 visits to 152 fountains between 2015 and 2019. We investigated both the colonization and recolonization processes of mosquito larvae within these water infrastructures. Our findings revealed higher larval presence in sandbox-sewers compared to siphonic or direct sewers, and the presence of vegetation and the use of naturalized water positively influenced larval occurrence in fountains. The application of larvicidal treatment significantly reduced larvae presence; however, recolonization rates were negatively affected by the time elapsed since treatment. Climatic conditions played a critical role in the colonization and recolonization of sewers and urban fountains, with mosquito occurrence exhibiting non-linear patterns and, generally, increasing at intermediate temperatures and accumulated rainfall levels. This study emphasizes the importance of considering sewers and fountains characteristics and climatic conditions when implementing vector control programs to optimize resources and effectively reduce mosquito populations.

Avian Plasmodium spp. and Haemoproteus spp. parasites in mosquitoes in Germany

BACKGROUND

Although haemosporidian parasites may cause considerable health and economic problems in aviaries, there is limited understanding of the vectors transmitting them. Mosquito-borne Plasmodium species are responsible for the deaths of numerous exotic (= immunologically naïve) birds in zoos every year, while native birds are adapted to the parasites and largely protected by an effective immune response.

METHODS

Mosquitoes were collected in bird/animal parks, wetlands and private gardens in various regions of Germany from 2020 to 2022. Females were pooled with up to 10 specimens according to taxon, location and date. Extracted DNA was screened for avian Haemosporida-specific mitochondrial rDNA using real-time polymerase chain reaction (PCR). Positive samples were amplified by a Plasmodium/Haemoproteus-specific nested PCR targeting the partial cytochrome b gene, followed by sequencing of the PCR product for species identification. Sequences were checked against GenBank and MalAvi databases.

RESULTS

PCR of 2633 pools with 8834 female mosquitoes signalled infection with Plasmodium in 46 pools and with Haemoproteus in one pool. Further amplification and sequencing demonstrated the occurrence of Haemoproteus majoris lineage PARUS1 (n = 1) as well as several Plasmodium species and lineages, including Plasmodium relictum SGS1 (n = 16) and GRW11 (n = 1), P. matutinum LINN1 (n = 13), P. vaughani SYAT05 (n = 10), P. circumflexum TURDUS01 (n = 3), P. cathemerium PADOM02 (n = 1) and Plasmodium sp. SYBOR02 (n = 1) and PLOPRI01 (n = 1). The infections were detected in Culex pipiens sensu lato (n = 40), Culiseta morsitans/fumipennis (n = 6) and Aedes cinereus/geminus (n = 1).

CONCLUSIONS

Although the overall Plasmodium minimum infection rate (5.2) appears to be low, the results demonstrated not only the ongoing circulation of Plasmodium parasites in the German mosquito population, but also the occurrence of eight distinct Plasmodium lineages, with three of them (PADOM02, SYBOR02, PLOPRI01) being detected in Germany for the first time. This study highlights the importance of conducting mosquito-borne pathogen surveillance studies simultaneously targeting vectors and vertebrate hosts, as certain species may be detected more readily in their vectors than in their vertebrate hosts, and vice versa.

First evidence for development of Plasmodium relictum (Grassi and Feletti, 1891) sporozoites in the salivary glands of Culex modestus Ficalbi, 1889

The competence of insect vectors to transmit diseases plays a key role in host-parasite interactions and in the dynamics of avian malaria and other haemosporidian infections (Apicomplexa, Haemosporida). However, the presence of parasite DNA in the body of blood-sucking insects does not always constitute evidence for their competence as vectors. In this study, we investigate the susceptibility of wild-caught mosquitoes (Culex spp.) to complete sporogony of Plasmodium relictum (cyt b lineage SGS1) isolated from great tits (Parus major L., 1758). Adult female mosquitoes were collected with a CO₂ bait trap overnight. A set of 50 mosquitoes was allowed to feed for 3 h at night on a single great tit infected with P. relictum. This trial was repeated on 6 different birds. The bloodfed mosquitoes that survived (n = 68) were dissected within 1-2 days (for ookinetes, n = 10) and 10-33 days post infection (for oocysts and sporozoites, n = 58) in order to confirm the respective parasite stages in their organs. The experiment confirmed the successful development of P. relictum (cyt b lineage SGS1) to the stage of sporozoites in Culex pipiens L., 1758 (n = 27) and in Culex modestus (n = 2). Our study provides the first evidence that C. modestus is a competent vector of P. relictum isolated from great tits, suggesting that this mosquito species could also play a role in the natural transmission of avian malaria.

Effect of Breeding Season on Haemosporidian Infections in Domestic Chickens

Reproduction is believed to contribute to the frequently observed seasonal cycles in parasite loads in many organisms, as an investment in reproduction by the host could result in a higher susceptibility to parasites. In this study, we examined the impact of breeding season on haemosporidian infection in free-range chickens (Gallus gallus domesticus). We sampled a total of 122 chickens (66 chickens during the breeding season of April 2017 and 56 chickens during the non-breeding season of January 2017) to test for haemosporidian infections. The result showed that 56 out of 66 chickens examined during the breeding season tested positive for parasites (84.8% parasite prevalence), whereas 39 out of 56 chickens tested positive for parasites during the non-breeding season (69.6% parasite prevalence). Moreover, among the 11 Leucocytozoon lineages and 2 Plasmodium lineages identified, the parasite lineages that infected chickens during the breeding season were more diversified than those that affected chickens during the non-breeding season. This study indicated that chickens have a higher incidence of haemosporidian infection and a greater diversity of haemosporidian parasite lineages during the breeding season relative to the non-breeding season.

Habitat-dependent Culicoides species composition and abundance in blue tit (Cyanistes caeruleus) nests

Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in 2 types of forests located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout 2 consecutive years. During the 3rd year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds' nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling's features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition.

High Blood Parasite Infection Rate and Low Fitness Suggest That Forest Water Bodies Comprise Ecological Traps for Pied Flycatchers

Blood parasites are considered to have strong negative effects on host fitness. Negative fitness consequences may be associated with proximity to areas where blood parasite vectors reproduce. This study tested for relationships between haemosporidian infection prevalence, parasitemia, and fitness parameters of breeding Pied Flycatchers (Ficedula hypoleuca) at different distances from forest water bodies. Prevalence and parasitemias (the intensity of infection) of haemosporidians and vector abundance generally decreased with increasing distance from forest lakes, streams, and bogs. Fledgling numbers were lower, and their condition was worse in the vicinity of water bodies, compared with those located one kilometer away from lakes and streams. At the beginning of the breeding season, adult body mass was not related to distance to the nearest water body, whereas at the end of the breeding season body mass was significantly lower closer to water bodies. Forest areas around water bodies may represent ecological traps for Pied Flycatchers. Installing nest boxes in the vicinity of forest water bodies creates unintended ecological traps that may have conservation implications.

The Impact of Temperature on the Sporogonic Development of the Tropical Avian Malaria Parasite Plasmodium relictum (Genetic Lineage pGRW4) in Culex pipiens Form molestus Mosquitoes

The avian malaria parasite Plasmodium relictum (genetic lineage pGRW4) is known to cause severe pathology in nonadapted vertebrate hosts. This parasite is prevalent in some bird species in Northern Europe, however the records obtained are only from adult long-distance migrant birds after their return from the wintering grounds. A recent experimental study showed that this parasite completes sporogonic development in the local European vector Culex pipiens at a controlled mean temperature of 19 °C. Thereby, temperature limits for the transmission of this parasite in Northern Europe remain unknown. In this study, we took a step further and tested the impact of different temperature conditions, including some extreme fluctuations between 23 °C down to 7 °C, on the sporogonic development of P. relictum (pGRW4) in the vector Culex pipiens form molestus. Mosquitoes were exposed to infection and kept under different air-temperature conditions: (i) constant warm temperature, (ii) natural outdoor temperatures and (iii) temporary exposure to low temperatures. Plasmodium relictum (pGRW4) completed sporogony in mosquitoes of all experimental groups, however different patterns of the sporogonic development depending on temperature conditions were observed. Based on these results, we conclude that the cool air temperature of Northern Europe in summer is not a limiting factor in successful development of the parasite. However, delayed sporogony caused by low summer temperatures may have a detrimental impact on the active transmission of this parasite in Northern Europe.

Assessment of Associations between Malaria Parasites and Avian Hosts-A Combination of Classic System and Modern Molecular Approach

Simple Summary

Throughout history, frequent outbreaks of diseases in humans have occurred following transmission from animals. While some diseases can jump between birds and mammals, others are stuck to closely related species. Understanding the mechanisms of host–parasite associations will enable us to predict the outbreaks of diseases and will therefore be important to society and ecological health. For decades, scientists have attempted to reveal how host–parasite associations are formed and persist. The key is to assess the ability of the parasite to infect and reproduce within the host without killing the host. Related studies have faced numerous challenges, but technical advances are providing solutions and are gradually broadening our understanding. In this review, I use bird malaria and related blood parasites as a model system and summarize the important advances in techniques and perspectives and how they provide new approaches for understanding the evolution of host–parasite associations to further predict disease outbreaks.

Abstract

Avian malaria and related haemosporidian parasites are responsible for fitness loss and mortality in susceptible bird species. This group of globally distributed parasites has long been used as a classical system for investigating host–parasite associations. The association between a parasite and its hosts can be assessed by the prevalence in the host population and infection intensity in a host individual, which, respectively, reflect the ability of the parasite to infect the host and reproduce within the host. However, the latter has long been poorly investigated due to numerous challenges, such as lack of general molecular markers and limited sensitivity of traditional methods, especially when analysing naturally infected birds. The recent development of genetic databases, together with novel molecular methodologies, has shed light on this long-standing problem. Real-time quantitative PCR has enabled more accurate quantification of avian haemosporidian parasites, and digital droplet PCR further improved experimental sensitivity and repeatability of quantification. In recent decades, parallel studies have been carried out all over the world, providing great opportunities for exploring the adaptation of haemosporidian parasites to different hosts and the variations across time and space, and further investigating the coevolutionary history between parasites and their hosts. I hereby review the most important milestones in diagnosis techniques of avian haemosporidian parasites and illustrate how they provide new insights for understanding host–parasite associations.

Ecological Effects on the Dynamics of West Nile Virus and Avian Plasmodium: The Importance of Mosquito Communities and Landscape

Humans and wildlife are at risk from certain vector-borne diseases such as malaria, dengue, and West Nile and yellow fevers. Factors linked to global change, including habitat alteration, land-use intensification, the spread of alien species, and climate change, are operating on a global scale and affect both the incidence and distribution of many vector-borne diseases. Hence, understanding the drivers that regulate the transmission of pathogens in the wild is of great importance for ecological, evolutionary, health, and economic reasons. In this literature review, we discuss the ecological factors potentially affecting the transmission of two mosquito-borne pathogens circulating naturally between birds and mosquitoes, namely, West Nile virus (WNV) and the avian malaria parasites of the genus Plasmodium. Traditionally, the study of pathogen transmission has focused only on vectors or hosts and the interactions between them, while the role of landscape has largely been ignored. However, from an ecological point of view, it is essential not only to study the interaction between each of these organisms but also to understand the environmental scenarios in which these processes take place. We describe here some of the similarities and differences in the transmission of these two pathogens and how research into both systems may facilitate a greater understanding of the dynamics of vector-borne pathogens in the wild.

Mosquito fauna in Extremadura (western Spain): Updated catalog with new records, distribution maps, and medical relevance

An important element of vector control and surveillance of mosquito-borne diseases is updated information on vector species distribution. The aim of this study was to collect available information about mosquito species reported in Extremadura between 1920 and 2020 and create a catalog that would combine both published data and our recent field identifications. An exhaustive list is hereby presented, including species status and detailed distribution maps at a municipal level as well as their importance for public health. A total of 33 species, classified into five genera: Anopheles (five species), Aedes (14), Culex (nine), Culiseta (four), and Orthopodomyia (one) has been recorded, including 31 autochthonous, one invasive, Aedes (Stegomyia) albopictus, and one disappeared since 1953, Aedes (Stegomyia) aegypti. For the first time in Extremadura, we report the presence of important vectors such as Aedes (Aedimorphus) vexans vexans and Culex (Culex) perexiguus, and the new record of six species in the province of Badajoz, namely: Aedes (Dahliana) echinus, Aedes (Fredwardsius) vittatus, Aedes (Ochlerotatus) berlandi, Aedes (Ochlerotatus) pulcritarsis, Culex (Culex) mimeticus, and Culiseta (Culiseta) subochrea. Nineteen of these species are potential vectors of medical and veterinary relevance.

Diversity and host assemblage of avian haemosporidians in different terrestrial ecoregions of Peru

Characterizing the diversity and structure of host–parasite communities is crucial to understanding their eco-evolutionary dynamics. Malaria and related haemosporidian parasites are responsible for fitness loss and mortality in bird species worldwide. However, despite exhibiting the greatest ornithological biodiversity, avian haemosporidians from Neotropical regions are quite unexplored. Here, we analyze the genetic diversity of bird haemosporidian parasites (Plasmodium and Haemoproteus) in 1,336 individuals belonging to 206 bird species to explore for differences in diversity of parasite lineages and bird species across 5 well-differentiated Peruvian ecoregions. We detected 70 different haemosporidian lineages infecting 74 bird species. We showed that 25 out of the 70 haplotypes had not been previously recorded. Moreover, we also identified 81 new host–parasite interactions representing new host records for these haemosporidian parasites. Our outcomes revealed that the effective diversity (as well as the richness, abundance, and Shannon–Weaver index) for both birds and parasite lineages was higher in Amazon basin ecoregions. Furthermore, we also showed that ecoregions with greater diversity of bird species also had high parasite richness, hence suggesting that host community is crucial in explaining parasite richness. Generalist parasites were found in ecoregions with lower bird diversity, implying that the abundance and richness of hosts may shape the exploitation strategy followed by haemosporidian parasites. These outcomes reveal that Neotropical region is a major reservoir of unidentified haemosporidian lineages. Further studies analyzing host distribution and specificity of these parasites in the tropics will provide important knowledge about phylogenetic relationships, phylogeography, and patterns of evolution and distribution of haemosporidian parasites.

Plasmodium matutinum Transmitted by Culex pipiens as a Cause of Avian Malaria in Captive African Penguins (Spheniscus demersus) in Italy

Avian malaria is a parasitic disease of birds caused by protozoa belonging to the genus Plasmodium, within the order Haemosporida. Penguins are considered particularly susceptible, and outbreaks in captive populations can lead to high mortality. We used a multidisciplinary approach to investigate the death due to avian malaria, occurred between 2015 and 2019, in eight African penguins (Spheniscus demersus) kept in two Italian zoos located in central Italy, and situated about 30 km apart. We also provided information about the presence and circulation of Plasmodium spp. in mosquitoes in central Italy by sampling mosquitoes in both zoos where penguin mortalities occurred. In the eight dead penguins, gross and histopathological lesions were consistent with those previously observed by other authors in avian malaria outbreaks. Organs from dead penguins and mosquitoes collected in both zoos were tested for avian malaria parasites by using a PCR assay targeting the partial mitochondrial conserved region of the cytochrome b gene. Identification at species level was performed by sequencing analysis. Plasmodium matutinum was detected in both dead penguins and in mosquitoes (Culex pipiens), while Plasmodium vaughani in Culex pipiens only. Parasites were not found in any of the PCR tested Aedes albopictus samples. Based on our phylogenetic analysis, we detected three previously characterized lineages: Plasmodium matutinum LINN1 and AFTRU5, P. vaughani SYAT05. In Culex pipiens we also identified two novel lineages, CXPIP32 (inferred morphospecies Plasmodium matutinum) and CXPIP33 (inferred morphospecies P. vaughani). Significantly, LINN1 and AFTRU5 were found to be associated to penguin deaths, although only LINN1 was detected both in penguins (along the years of the study) and in Culex pipiens, while AFTRU5 was detected in a single penguin dead in 2017. In conclusion, in our study Plasmodium matutinum was found to cause avian malaria in captive penguins kept in Europe, with Culex pipiens being its most probable vector. Our results are in agreement with previous studies suggesting that Culex pipiens is one of the main vectors of Plasmodium spp. in Europe and the Northern Hemisphere. Zoos maintaining captive penguins in temperate areas where Culex pipiens is abundant should be well aware of the risks of avian malaria, and should put every effort to prevent outbreaks, in particular during the periods when the number of vectors is higher.

Assessing Diversity, Plasmodium Infection and Blood Meal Sources in Mosquitoes (Diptera: Culicidae) from a Brazilian Zoological Park with Avian Malaria Transmission

Avian malaria parasites are widespread parasites transmitted by Culicidae insects belonging to different genera. Even though several studies have been conducted recently, there is still a lack of information about potential vectors of Plasmodium parasites, especially in Neotropical regions. Former studies with free-living and captive animals in São Paulo Zoo showed the presence of several Plasmodium and Haemoproteus species. In 2015, a pilot study was conducted at the zoo to collect mosquitoes in order to find out (i) which species of Culicidae are present in the study area, (ii) what are their blood meal sources, and (iii) to which Plasmodium species might they be potential vectors. Mosquitoes were morphologically and molecularly identified. Blood meal source and haemosporidian DNA were identified using molecular protocols. A total of 25 Culicidae species were identified, and 6 of them were positive for Plasmodium/Haemoproteus DNA. Ten mosquito species had their source of blood meal identified, which were mainly birds, including some species that were positive for haemosporidian parasites in the former study mentioned. This study allowed us to expand the list of potential vectors of avian malaria parasites and to improve our knowledge of the evolutionary and ecological relationships between the highly diverse communities of birds, parasites, and vectors present at São Paulo Zoo.

A Literature Review of Host Feeding Patterns of Invasive Aedes Mosquitoes in Europe

Aedes invasive mosquitoes (AIMs) play a key role as vectors of several pathogens of public health relevance. Four species have been established in Europe, including Aedes aegypti, Aedesalbopictus, Aedes japonicus and Aedes koreicus. In addition, Aedes atropalpus has been repeatedly recorded although it has not yet been established. In spite of their importance in the transmission of endemic (e.g., heartworms) and imported pathogens (e.g., dengue virus), basic information of parameters affecting their vectorial capacity is poorly investigated. The aim of this study is to review the blood feeding patterns of these invasive mosquito species in Europe, summarizing available information from their native and introduced distribution ranges. The feeding patterns of mosquitoes constitute a key parameter affecting the contact rates between infected and susceptible hosts, thus playing a central role in the epidemiology of mosquito-borne pathogens. Our results highlight that these mosquito species feed on the blood of different vertebrate groups from ectotherms to birds and mammals. However, humans represent the most important source of blood for these species, accounting for 36% and 93% of hosts identified for Ae. japonicus and Ae. aegypti, respectively. In spite of that, limited information has been obtained for some particular species, such as Ae. koreicus, or it is restricted to a few particular areas. Given the high vector competence of the four AIM species for the transmission of different emerging arboviruses such as dengue, Chikungunya, Zika or Yellow fever viruses and their high feeding rates on humans, these AIM species may have an important impact on the vectorial capacity for such pathogens on urban and periurban areas. Finally, we propose directions for future research lines based on identified knowledge gaps.

Mosquito identification and haemosporidian parasites detection in the enclosure of the African penguins (Spheniscus demersus) at the SANBI zoological garden

The National Zoological Gardens (NZG) is a facility of the South African National Biodiversity Institute (SANBI) and the largest zoo in southern Africa. Among the 9000 captive animals kept by the NZG, is the endangered African penguin (Spheniscus demersus). There have been several post-mortem reports on deaths of penguins in the NZG due to haemosporidian infections, however, the haemosporidian lineages involved and possible insect vector are unknown. Haemosporidians are apicomplexan parasites that infect vertebrates through blood-sucking dipteran insects. Therefore, the current study aimed to identify mosquitoes that are potential vectors found within the African penguin enclosure as well as to detect the haemosporidian parasites from these insects using nested-PCR and real-time PCR (qPCR) analyses. Mosquito samples were collected using an overnight UV-light trap setup for 3 months. From the 65 pooled samples representing 325 mosquitoes, morphological and molecular analysis showed that Culex pipiens (52.31%) was the dominant species followed by Cx. t heileri (30.77%) and Cx. quinquefasciatus (16.92%). Nested-PCR detected parasite DNA of Leucocytozoon sp. and Plasmodium sp. The Cx. pipiens had the highest minimum infection rate (MIR) of 5.88% by nested-PCR and 9.41% by qPCR whilst Cx. quinquefasciatus had MIR of 3.64% in both assays and no haemosporidian parasites were detected from Cx. t heileri. One Cx. pipiens sample had a co-infection of both Plasmodium sp. and Leucocytozoon sp. detected by nested-PCR. These findings suggest that effective control measures for blood-sucking dipteran insects is required at the NZG and more studies should be conducted to determine the actual prevalence of these haemosporidian parasites among other bird species within NZG.

Determinants of the current and future distribution of the West Nile virus mosquito vector Culex pipiens in Spain

Changes in environmental conditions, whether related or not to human activities, are continuously modifying the geographic distribution of vectors, which in turn affects the dynamics and distribution of vector-borne infectious diseases. Determining the main ecological drivers of vector distribution and how predicted changes in these drivers may alter their future distributions is therefore of major importance. However, the drivers of vector populations are largely specific to each vector species and region. Here, we identify the most important human-activity-related and bioclimatic predictors affecting the current distribution and habitat suitability of the mosquito Culex pipiens and potential future changes in its distribution in Spain. We determined the niche of occurrence (NOO) of the species, which considers only those areas lying within the range of suitable environmental conditions using presence data. Although almost ubiquitous, the distribution of Cx. pipiens is mostly explained by elevation and the degree of urbanization but also, to a lesser extent, by mean temperatures during the wettest season and temperature seasonality. The combination of these predictors highlights the existence of a heterogeneous pattern of habitat suitability, with most suitable areas located in the southern and northeastern coastal areas of Spain, and unsuitable areas located at higher altitude and in colder regions. Future climatic predictions indicate a net decrease in distribution of up to 29.55%, probably due to warming and greater temperature oscillations. Despite these predicted changes in vector distribution, their effects on the incidence of infectious diseases are, however, difficult to forecast since different processes such as local adaptation to temperature, vector-pathogen interactions, and human-derived changes in landscape may play important roles in shaping the future dynamics of pathogen transmission.

The role of different Culex mosquito species in the transmission of West Nile virus and avian malaria parasites in Mediterranean areas

Vector-borne diseases, especially those transmitted by mosquitoes, have severe impacts on public health and economy. West Nile virus (WNV) and avian malaria parasites of the genus Plasmodium are mosquito-borne pathogens that may produce severe disease and illness in humans and birds, respectively, and circulate in an endemic form in southern Europe. Here, we used field-collected data to identify the impact of Culex pipiens, Cx. perexiguus and Cx. modestus, on the circulation of both WNV and Plasmodium in Andalusia (SW Spain) using mathematical modelling of the basic reproduction number (R₀ ). Models were calibrated with field-collected data on WNV seroprevalence and Plasmodium infection in wild house sparrows, presence of WNV and Plasmodium in mosquito pools, and mosquito blood-feeding patterns. This approach allowed us to determine the contribution of each vector species to pathogen amplification. Overall, 0.7% and 29.6% of house sparrows were positive to WNV antibodies and Plasmodium infection, respectively. In addition, the prevalence of Plasmodium was higher in Cx. pipiens (2.0%), followed by Cx. perexiguus (1.8%) and Cx. modestus (0.7%). Three pools of Cx. perexiguus were positive to WVN. Models identified Cx. perexiguus as the most important species contributing to the amplification of WNV in southern Spain. For Plasmodium models, R₀ values were higher when Cx. pipiens was present in the population, either alone or in combination with the other mosquito species. These results suggest that the transmission of these vector-borne pathogens depends on different Culex species, and consequently, their transmission niches will present different spatial and temporal patterns. For WNV, targeted surveillance and control of Cx. perexiguus populations appear as the most effective measure to reduce WNV amplification. Also, preventing Culex populations near human settlements, or reducing the abundance of these species, are potential strategies to reduce WNV spillover into human populations in southern Spain.

Mosquitoes in an Urban Zoo: Identification of Blood Meals, Flight Distances of Engorged Females, and Avian Malaria Infections

Zoological gardens are home to a large number of vertebrate species and as such are suitable sites for both mosquito breeding and maintenance. They are excellent places for entomological studies of mosquito phenology, diversity, and blood-feeding patterns, as well as for xenomonitoring. During 2016, we sampled mosquitoes in Barcelona Zoo and used molecular methods to determine their blood-feeding patterns and the prevalence and diversity of avian malaria parasites. We also estimated the flight distance of engorged mosquitoes in the area. Overall, 1,384 adult Culex pipiens s.l., Culiseta longiareolata, and Aedes albopictus were captured. Birds dominated the diet of Cx. pipiens s.l. (n = 87) and Cs. longiareolata (n = 6), while humans were the only blood-meal source of Ae. albopictus (n = 3). Mosquitoes had a mean flight distance of 95.67 m after feeding on blood (range 38.71–168.51 m). Blood parasites were detected in the abdomen of 13 engorged Cx. pipiens s.l., eight of which had fed on magpies. Four Plasmodium lineages and a single lineage of the malaria-like parasite Haemoproteus were identified. These results suggest that Cx. pipiens s.l. is involved in the local transmission of avian Plasmodium, which potentially affects the circulation of parasites between and within wildlife and enclosed animals. Vigilance regarding possible mosquito breeding sites in this zoo is thus recommended.

Dynamics of prevalence and distribution pattern of avian Plasmodium species and its vectors in diverse zoogeographical areas - A review

Avian Plasmodium is of special interest to health care scientists and veterinarians due to the potency of causing avian malaria in non-adapted birds and their evolutionary phylogenetic relationship with human malaria species. This article aimed to provide a comprehensive list of the common avian Plasmodium parasites in the birds and mosquitoes, to specify the common Plasmodium species and lineages in the selected regions of West of Asia, East of Europe, and North of Africa/Middle East, and to determine the contribution of generalist and host-specific Plasmodium species and lineages. The final list of published infected birds includes 146 species, among which Passer domesticus was the most prevalent in the studied areas. The species of Acrocephalus arundinaceus and Sylvia atricapilla were reported as common infected hosts in the examined regions of three continents. The highest numbers of common species of infected birds between continent pairs were from Asia and Europe, and no common record was found from Europe and Africa. The species of Milvus migrans and Upupa epops were recorded as common species from Asia and Africa. The lineage of GRW11 and species of P. relictum were the most prevalent parasites among all the infection records in birds. The most prevalent genus of vectors of avian malaria belonged to Culex and species of Cx. pipiens. The lineage SGS1 with the highest number of occurrence has been found in various vectors comprising Cx. pipiens, Cx. modestus, Cx. theileri, Cx. sasai, Cx. perexiguus, Lutzia vorax, and Culicoides alazanicus. A total of 31 Plasmodium species and 59 Plasmodium lineages were recorded from these regions. SGS1, GRW04, and GRW11, and P. relictum and P. vaughani are specified as common generalist avian malaria parasites from these three geographic areas. The presence of avian Plasmodium parasites in distant geographic areas and various hosts may be explained by the movement of the infected birds through the migration routes. Although most recorded lineages were from Asia, investigating the distribution of lineages in some of the countries has not been done. Thus, the most important outcome of this review is the determination of the distribution pattern of parasite and vector species that shed light on gaps requiring further studies on the monitoring of avian Plasmodium and common vectors extension. This task could be achieved through scientific field and laboratory networking, performing active surveillance and designing regional/continental control programs of birds' malaria and other zoonotic diseases.

Plasmodium transmission differs between mosquito species and parasite lineages

Factors such as the particular combination of parasite-mosquito species, their co-evolutionary history and the host's parasite load greatly affect parasite transmission. However, the importance of these factors in the epidemiology of mosquito-borne parasites, such as avian malaria parasites, is largely unknown. Here, we assessed the competence of two mosquito species [Culex pipiens and Aedes (Ochlerotatus) caspius], for the transmission of four avian Plasmodium lineages (Plasmodium relictum SGS1 and GRW11 and Plasmodium cathemerium-related lineages COLL1 and PADOM01) naturally infecting wild house sparrows. We assessed the effects of parasite identity and parasite load on Plasmodium transmission risk through its effects on the transmission rate and mosquito survival. We found that Cx. pipiens was able to transmit the four Plasmodium lineages, while Ae. caspius was unable to transmit any of them. However, Cx. pipiens mosquitoes fed on birds infected by P. relictum showed a lower survival and transmission rate than those fed on birds infected by parasites related to P. cathemerium. Non-significant associations were found with the host-parasite load. Our results confirm the existence of inter- and intra-specific differences in the ability of Plasmodium lineages to develop in mosquito species and their effects on the survival of mosquitoes that result in important differences in the transmission risk of the different avian malaria parasite lineages studied.

From Africa to Europe: evidence of transmission of a tropical Plasmodium lineage in Spanish populations of house sparrows

Background

Avian malaria parasites are a highly diverse group that commonly infect birds and have deleterious effects on their hosts. Some parasite lineages are geographically widespread and infect many host species in many regions. Bird migration, natural dispersal, invasive species and human-mediated introductions into areas where competent insect vectors are present, are probably the main drivers of the current distribution of avian malaria parasites.

Methods

A total of 412 and 2588 wild house sparrows (Passer domesticus) were captured in 2012 and 2013 in two areas of the Iberian Peninsula (central and southern Spain, respectively). Genomic DNA was extracted from blood samples; parasite lineages were sequenced and identified by comparing with GenBank and/or MalAvi databases.

Results

Thirteen Plasmodium lineages were identified in house sparrows corresponding to three major clades. Five individuals were infected by the African Plasmodium lineage PAGRI02, which has been proposed to actively circulate only in Africa.

Conclusions

Despite the low prevalence of PAGRI02 in sparrows in Spain, our results suggest that the area of transmission of this parasite is more widespread than previously thought and covers both Africa and Europe. Further studies of the global distribution of Plasmodium lineages infecting wild birds are required to identify the current transmission areas of these parasites. This is vital given the current scenario of global change that is providing new opportunities for avian malaria transmission into areas where parasites were previously absent.

A detailed review of the mosquitoes (Diptera: Culicidae) of Iran and their medical and veterinary importance

Mosquitoes (Diptera: Culicidae) are the most significant arthropods of medical importance because of the burden of diseases, such as malaria, encephalitis and filariasis, which are caused by pathogens and parasites they transmit to humans. In 2007, the most recently published checklist of Iranian mosquitoes included 64 species representing seven genera. Public databases were searched to the end of August 2018 for publications concerning the diseases in Iran caused by mosquito-borne pathogens. Pertinent information was extracted and analyzed, and the checklist of Iranian mosquitoes was updated. Six arboviral diseases, two bacterial diseases, four helminthic diseases and two protozoal diseases occur in Iran. The agents of these diseases are biologically or mechanically known or assumed to be transmitted by mosquitoes. The updated checklist of Iranian mosquitoes includes 69 species representing seven or 11 genera depending on the generic classification of aedines. There is no published information about the role of mosquitoes in the transmission of the causal agents of avian malaria, avian pox, bovine ephemeral fever, dengue fever, Rift Valley fever, Sindbis fever, Deraiophoronema evansi infection, lymphatic filariasis, anthrax and tularemia in Iran. There is just one imported case of lymphatic filariasis, which is not endemic in the country. It seems arthropods do not play an important role in the epidemiology of anthrax and ixodid ticks are the main vectors of the tularemia bacterium. In view of the recent finding of only a few adults and larvae of Aedes albopictus in southeastern Iran and the absence of Ae. aegypti, it is not possible to infer the indigenous transmission of the dengue fever virus in Iran. Considering the importance of mosquito-borne diseases in the country, it is necessary to improve vector and vector-borne disease surveillance in order to apply the best integrated vector management interventions as a part of the One Health concept.

Effects of host sex, body mass and infection by avian Plasmodium on the biting rate of two mosquito species with different feeding preferences

BACKGROUND

The transmission of mosquito-borne pathogens is strongly influenced by the contact rates between mosquitoes and susceptible hosts. The biting rates of mosquitoes depend on different factors including the mosquito species and host-related traits (i.e. odour, heat and behaviour). However, host characteristics potentially affecting intraspecific differences in the biting rate of mosquitoes are poorly known. Here, we assessed the impact of three host-related traits on the biting rate of two mosquito species with different feeding preferences: the ornithophilic Culex pipiens and the mammophilic Ochlerotatus (Aedes) caspius. Seventy-two jackdaws Corvus monedula and 101 house sparrows Passer domesticus were individually exposed to mosquito bites to test the effect of host sex, body mass and infection status by the avian malaria parasite Plasmodium on biting rates.

RESULTS

Ochlerotatus caspius showed significantly higher biting rates than Cx. pipiens on jackdaws, but non-significant differences were found on house sparrows. In addition, more Oc. caspius fed on female than on male jackdaws, while no differences were found for Cx. pipiens. The biting rate of mosquitoes on house sparrows increased through the year. The bird infection status and body mass of both avian hosts were not related to the biting rate of both mosquito species.

CONCLUSIONS

Host sex was the only host-related trait potentially affecting the biting rate of mosquitoes, although its effect may differ between mosquito and host species.

Host-parasite interaction explains variation in the prevalence of avian haemosporidians at the community level

Parasites are a selective force that shape host community structure and dynamics, but host communities can also influence parasitism. Understanding the dual nature from host-parasite interactions can be facilitated by quantifying the variation in parasite prevalence among host species and then comparing that variation to other ecological factors that are known to also shape host communities. Avian haemosporidian parasites (e.g. Plasmodium and Haemoproteus) are abundant and widespread representing an excellent model for the study of host-parasite interactions. Several geographic and environmental factors have been suggested to determine prevalence of avian haemosporidians in bird communities. However, it remains unknown whether host and parasite traits, represented by phylogenetic distances among species and degree of specialization in host-parasite relationships, can influence infection status. The aims of this study were to analyze factors affecting infection status in a bird community and to test whether the degree of parasite specialization on their hosts is determined by host traits. Our statistical analyses suggest that infection status is mainly determined by the interaction between host species and parasite lineages where tolerance and/or susceptibility to parasites plays an essential role. Additionally, we found that although some of the parasite lineages infected a low number of bird individuals, the species they infected were distantly related and therefore the parasites themselves should not be considered typical host specialists. Infection status was higher for generalist than for specialist parasites in some, but not all, host species. These results suggest that detected prevalence in a species mainly results from the interaction between host immune defences and parasite exploitation strategies wherein the result of an association between particular parasite lineages and particular host species is idiosyncratic.

Low occurrence of hemosporidian parasites in the Neotropic cormorant (Phalacrocorax brasilianus) in Chile

Hemosporidian parasites rarely infect aquatic birds. Few studies have been conducted in South America identifying some lineages of the genera Plasmodium, Leucocytozoon, and Haemoproteus, but none has been done in the Neotropic cormorant (Phalacrocorax brasilianus). This species is widely distributed through the American continent, from Southern USA to Tierra del Fuego, using a wide range of aquatic habitats. We molecularly studied the occurrence and diversity of hemosporidian lineages infecting individuals of Neotropic cormorant across a broad latitudinal gradient in Chile (Arica to Tierra del Fuego). As expected, a very low occurrence of individuals infected by Plasmodium sp. (4/123, 3.3%) and Leucocytozoon sp. (2/123, 1.6%) was detected. We found no evidence of Haemoproteus sp. We identified one lineage of Plasmodium (ZEMAC01) and one new lineage of Leucocytozoon (PHABRA01) infecting cormorants. Individuals infected by Plasmodium sp. were birds from only one site (i.e., Chillán), whereas Leucocytozoon sp. was found in one bird from Valdivia and another one from Tierra del Fuego. Our results expand the known range of hemosporidian parasite lineages in aquatic birds providing an essential baseline data that contribute to a better understanding of the geographic range of hemosporidian parasites infecting Phalacrocoracidae in South America.

Using Bloodmeal Analysis to Assess Disease Risk to Wildlife at the New Northern Limit of a Mosquito Species

The historically southeastern mosquito species Culex erraticus has over the last 30 years undergone a marked expansion north. We evaluated this species' potential to participate in local disease cycles in the northeastern USA by identifying the vertebrate sources of blood in Cx. erraticus specimens from New Jersey. We found that the majority of bloodmeals (92.6%) were derived from birds, followed by 6.8% from mammals (of which half were human), and a single amphibian bloodmeal from a spring peeper (0.56%). Medium- and large-sized water birds from the order Pelecaniformes made up 60.4% of the bird species and 55.9% of all identified hosts. This group of birds is known enzootic hosts of arboviruses such as eastern equine encephalitis virus, for which Cx. erraticus is a competent vector. Additionally, we screened blooded mosquitoes for avian malaria parasites and identified three different lineages of Plasmodium, including what may represent a new Plasmodium species (likely a wetland bird specialist) in bloodmeals from Green Herons, a Great Egret, and a Double-Crested Cormorant. Our results support the utility of mosquito bloodmeals as sources of information about circulating wildlife pathogens and reveal the potential of range-expanding species to intensify local zoonoses and bridge enzootic pathogens to humans.

Do avian malaria parasites reduce vector longevity?

Avian Plasmodium and malaria-like parasites of the genus Haemoproteus are widespread vector-borne parasites commonly found infecting birds. These parasites impose deleterious effects on their vertebrate hosts compromising their survival. While the interaction between these parasites and their vertebrate hosts has received much attention, the study of those factors determining the consequences of parasite infections in the insect vectors has been traditionally neglected. Recent studies have shown that host's parasite load and the mosquito's nutritional status and microbiota modulate the impact of parasites on mosquito longevity. Here, we provide a critical review of these studies to identify gaps in current knowledge and propose future research directions. Further experimental studies are needed to reveal the impact of avian malaria parasites in mosquitoes using realistic conditions found in wild parasite-mosquito assemblages.

Ecological determinants of avian malaria infections: An integrative analysis at landscape, mosquito and vertebrate community levels

Vector and host communities, as well as habitat characteristics, may have important but different impacts on the prevalence, richness and evenness of vector-borne parasites. We investigated the relative importance of (1) the mosquito community composition, (2) the vertebrate community composition and (3) landscape characteristics on the prevalence, richness and evenness of avian Plasmodium. We hypothesized that parasite prevalence will be more affected by vector-related parameters, while host parameters should be also important to explain Plasmodium richness and evenness. We sampled 2,588 wild house sparrows (Passer domesticus) and 340,829 mosquitoes, and we performed vertebrate censuses at 45 localities in the Southwest of Spain. These localities included urban, rural and natural landscapes that were characterized by several habitat variables. Twelve Plasmodium lineages were identified in house sparrows corresponding to three major clades. Variation partitioning showed that landscape characteristics explained the highest fraction of variation in all response variables (21.0%-44.8%). Plasmodium prevalence was in addition explained by vector-related variables (5.4%) and its interaction with landscape (10.2%). Parasite richness and evenness were mostly explained by vertebrate community-related variables. The structuring role of landscape characteristics in vector and host communities was a key factor in determining parasite prevalence, richness and evenness, although the role of each factor differed according to the parasite parameters studied. These results show that the biotic and abiotic contexts are important to explain the transmission dynamics of mosquito-borne pathogens in the wild.

The Role of Culex pipiens L. (Diptera: Culicidae) in Virus Transmission in Europe

Over the past three decades, a range of mosquito-borne viruses that threaten public and veterinary health have emerged or re-emerged in Europe. Mosquito surveillance activities have highlighted the Culex pipiens species complex as being critical for the maintenance of a number of these viruses. This species complex contains morphologically similar forms that exhibit variation in phenotypes that can influence the probability of virus transmission. Critical amongst these is the choice of host on which to feed, with different forms showing different feeding preferences. This influences the ability of the mosquito to vector viruses and facilitate transmission of viruses to humans and domestic animals. Biases towards blood-feeding on avian or mammalian hosts have been demonstrated for different Cx. pipiens ecoforms and emerging evidence of hybrid populations across Europe adds another level of complexity to virus transmission. A range of molecular methods based on DNA have been developed to enable discrimination between morphologically indistinguishable forms, although this remains an active area of research. This review provides a comprehensive overview of developments in the understanding of the ecology, behaviour and genetics of Cx. pipiens in Europe, and how this influences arbovirus transmission.

Does bird metabolic rate influence mosquito feeding preference?

BACKGROUND

Host selection by mosquitoes plays a central role in the transmission of vector-borne infectious diseases. Although interspecific variation in mosquito attraction has often been reported, the mechanisms underlying intraspecific differences in hosts' attractiveness to mosquitoes are still poorly known. Metabolic rate is related to several physiological parameters used as location cues by mosquitoes, and so potentially affect host-vector contact rates. Therefore, individual hosts with higher metabolic rates should be more attractive to host-seeking mosquitoes. Here, we experimentally investigated the role of bird metabolic rate in the feeding preferences of Culex pipiens (Linnaeus), a widespread mosquito vector of many pathogens affecting human and wildlife health.

RESULTS

Passer domesticus (Linnaeus) pairs containing one bird treated with 2,4-dinitrophenol (DNP) and the other injected with phosphate-buffered saline solution (PBS) (i.e. control) were simultaneously exposed overnight to mosquitoes. The treatment did not affect the proportion of mosquitoes biting on each individual. However, mosquito feeding preference was negatively associated with bird resting metabolic rate but positively with bird body mass. These two variables explained up to 62.76% of the variations in mosquito feeding preference.

CONCLUSIONS

The relationships between mosquito feeding preferences and individual host characteristics could be explained by enhanced anti-mosquito behaviour associated with higher metabolic rates. The potential role of cues emitted by hosts is also discussed. Thus, individuals with high metabolism may actively avoid being bitten by mosquitoes, despite releasing more attractant cues. Since metabolic rates can be related to individual differences in personality and life history traits, differences in mosquitoes' feeding preferences may be related to intraspecific differences in exposure to vector-borne pathogens.

Mosquito community influences West Nile virus seroprevalence in wild birds: implications for the risk of spillover into human populations

Mosquito community composition plays a central role in the transmission of zoonotic vector-borne pathogens. We evaluated how the mosquito community affects the seroprevalence of West Nile virus (WNV) in house sparrows along an urbanisation gradient in an area with the endemic circulation of this virus. We sampled 2544 birds and 340829 mosquitoes in 45 localities, analysed in 15 groups, each containing one urban, one rural and one natural area. WNV seroprevalence was evaluated using an epitope-blocking ELISA kit and a micro virus-neutralization test (VNT). The presence of WNV antibodies was confirmed in 1.96% and 0.67% of birds by ELISA and VNT, respectively. The VNT-seropositive birds were captured in rural and natural areas, but not in urban areas. Human population density was zero in all the localities where VNT-positive birds were captured, which potentially explains the low incidence of human WNV cases in the area. The prevalence of neutralizing antibodies against WNV was positively correlated with the abundance of the ornithophilic Culex perexiguus but negatively associated with the abundance of the mammophilic Ochlerotatus caspius and Anopheles atroparvus. These results suggest that the enzootic circulation of WNV in Spain occurs in areas with larger populations of Cx. perexiguus and low human population densities.

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

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

Avian Plasmodium in Eastern Austrian mosquitoes

Background

Insect vectors, namely mosquitoes (Diptera: Culicidae), are compulsory for malaria parasites (Plasmodium spp.) to complete their life cycle. Despite this, little is known about vector competence of different mosquito species for the transmission of avian malaria parasites.

Methods

In this study, nested PCR was used to determine Plasmodium spp. occurrence in pools of whole individuals, as well as the diversity of mitochondrial cytochrome b gene sequences in wild-caught mosquitoes sampled across Eastern Austria in 2013–2015.

Results

A total of 45,749 mosquitoes in 2628 pools were collected, of which 169 pools (6.43%) comprising 9 mosquito species were positive for avian Plasmodium, with the majority of positives in mosquitoes of Culex pipiens s.l./Culex torrentium. Six different avian Plasmodium lineages were found, the most common were Plasmodium vaughani SYAT05, Plasmodium sp. Linn1 and Plasmodium relictum SGS1. In 2014, mosquitoes of the Culex pipiens complex were genetically identified and Culex pipiens f. pipiens presented with the highest number of avian Plasmodium positives (n = 37; 16.74%). Despite this, the minimum infection rate (MIR) was highest in Culex torrentium (5.36%) and Culex pipiens f. pipiens/f. molestus hybrids (5.26%). During 2014 and 2015, seasonal and annual changes in Plasmodium lineage distribution were also observed. In both years P. vaughani SYAT05 dominated at the beginning of the sampling period to be replaced later in the year by P. relictum SGS1 (2014) and Plasmodium sp. Linn1 (2015).

Conclusions

This is the first large-scale study of avian Plasmodium parasites in Austrian mosquitoes. These results are of special interest, because molecular identification of the taxa of the Cx. pipiens complex and Cx. torrentium enabled the determination of Plasmodium prevalence in the different mosquito taxa and hybrids of this complex. Since pools of whole insects were used, it is not possible to assert any vector competence in any of the examined mosquitoes, but the results are nonetheless valuable in providing an overview of avian Plasmodium species and lineages present in Austria.

Avian phenotypic traits related to feeding preferences in two Culex mosquitoes

Host choice by mosquitoes affects the transmission dynamics of vector-borne infectious diseases. Although asymmetries in mosquito attraction to vertebrate species have been reported, the relative importance of host characteristics in mosquito blood-feeding behavior is still poorly studied. Here, we investigate the relationship between avian phenotypic traits-in particular, morphometry, plumage coloration, and nesting and roosting behavior-and the blood-feeding patterns in two common Culex mosquito species on a North American avian community. Forage ratios of the mosquito species were unrelated to the phylogenetic relationships among bird species. Culex pipiens fed preferably on birds with lighter-colored plumage and longer tarsi; furthermore, solitary roosting avian species were both bitten by Cx. pipiens and Cx. restuans more often than expected. These associations may be explained by greater mosquito attraction towards larger birds with a greater color contrast against the background. Although communally roosting birds may release more cues and attract more mosquitoes, individuals may in fact receive fewer bites due to the encounter-dilution effect. Mosquito feeding behavior is a highly complex phenomenon, and our results may improve understanding of the non-random interaction between birds and mosquitoes in natural communities.