Avian malaria on Madagascar: bird hosts and putative vector mosquitoes of different Plasmodium lineages

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.

Raising the bar: genus-specific nested PCR improves detection and lineage identification of avian haemosporidian parasites

Avian haemosporidian parasites are useful model organisms to study the ecology and evolution of parasite-host interactions due to their global distribution and extensive biodiversity. Detection of these parasites has evolved from microscopic examination to PCR-based methods, with the mitochondrial cytochrome b gene serving as barcoding region. However, standard PCR protocols used for screening and identification purposes have limitations in detecting mixed infections and generating phylogenetically informative data due to short amplicon lengths. To address these issues, we developed a novel genus-specific nested PCR protocol targeting avian haemosporidian parasites. The protocol underwent rigorous testing utilizing a large dataset comprising blood samples from Malagasy birds of three distinct Passeriformes families. Furthermore, validation was done by examining smaller datasets in two other laboratories employing divergent master mixes and different bird species. Comparative analyses were conducted between the outcomes of the novel PCR protocol and those obtained through the widely used standard nested PCR method. The novel protocol enables specific identification of Plasmodium, Haemoproteus (Parahaemoproteus), and Leucocytozoon parasites. The analyses demonstrated comparable sensitivity to the standard nested PCR with notable improvements in detecting mixed infections. In addition, phylogenetic resolution is improved by amplification of longer fragments, leading to a better understanding of the haemosporidian biodiversity and evolution. Overall, the novel protocol represents a valuable addition to avian haemosporidian detection methodologies, facilitating comprehensive studies on parasite ecology, epidemiology, and evolution.

Prevalence of co-infection and genetic diversity of avian haemosporidian parasites in two rehabilitation facilities in Iran: implications for the conservation of captive raptors

Background

Various haemosporidian parasites infect raptors, especially captive hosts who may be more exposed. Diagnosis of threatening factors such as infectious diseases indirectly has a significant role in protecting endangered or threatened species that may boost the mortality or extinction resulting from declined reproduction. Few investigations have been performed in captive hosts to detect the prevalence of haemosporidian parasites and define genetic diversity in west Asia. For the first time, the current study was designed to determine the prevalence and genetic diversity of haemosporidian parasites in captive raptors by molecular methods in two rehabilitation facilities in North and North-east Iran and to define phylogenetic relationships of detected lineages circulating in raptors.

Results

Molecular characterization of the haemosporidian parasite was accomplished by PCR-based method and DNA sequencing in 62 captive raptors. The overall prevalence was ~ 36% with higher infection of Haemoproteus spp. than Leucocytozoon spp. Plasmodium infection was not detected in any host. Results showed that 22 individuals (of 10 species) were infected with unique lineages. Genus Haemoproteus was detected in 26.66% of examined individuals (of eight species) and Leucocytozoon was found in 10% of individuals (of four species). The molecular analysis could detect ten lineages (nine Haemoproteus spp. and one Leucocytozoon spp.) which were categorizes as new and six lineages which have been previously detected in the other investigations.

Conclusions

The Bayesian phylogenetic analysis derived from obtained data in the present study and published lineages in previous investigations indicated the probable host specificity of Haemoproteus and Leucocytozoon parasites in several sub-clades at hosts’ order and genus level. As monitoring the parasite loads of captive birds when admitted reduce the risk of infecting hosts in captivity at those locations, we designed this study to determine infection prevalence and genetic diversity of blood parasites in raptors examined in Iran. These results allow mapping of haemosporidian distribution and shed light on the depth of their diversity in Iran to protect species by identification of risk in rehabilitation facilities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-02068-9.

Efficacy of Trapping Methods in the Collection of Eretmapodites (Diptera: Culicidae) Mosquitoes in an Afrotropical Rainforest Region, South western Cameroon

Very little data exist on the biology of an afrotropical rainforest mosquito Eretmapodites (Er.) in a world undergoing dramatic changes due to deforestation. The aim was to assess the efficacy of different trapping methods in the collection of Er. mosquito in forested area. This was a longitudinal study involving collection of mosquitoes for over two years. Multiple collection methods (grouped into two categories), were used; i) net baited and un-baited traps to collect adults, ii) techniques that target immature stages subsequently reared to adults. All males were identified by genitalia dissection. Five thousand seven hundred and four mosquitoes representing 11 genera among which 2,334 Er. were identified. Mosquito abundance was highest in the net traps (n = 1276 (56.4%)) and sweep nets (n = 393(17.4%)) respectively. The abundance was highest in green colored net traps (435(34.09%)) with significant value of χ2= 40.000, P < 0.001 and in pigeons baited traps (473 (37.06%)) with significant value of χ2= 42.000, P = 0.003. The diversity ranges from H' = 2.65; DS = 0.84; SR = 24; ACE = 24.77 in sweep net to H' = 0; DS = 0; SR = 1; ACE = 1 in rock pool among males mosquitoes. While for females, H = 1.14; DS = 0.71; SR = 5; ACE = 5.16, in sweep net to H = 0; DS = 0; SR = 1; ACE = 1 in rock pool, tarpaulin, resting cage. Net traps, bamboo pot, and sweep netting are efficient in collecting high abundance of forest mosquitoes in the Talanagaye rainforest.

Mosquito species associated with horses in Madagascar: a review of their vector status with regard to the epidemiology of West Nile fever

In Madagascar, the high West Nile virus (WNV) antibody prevalence reported in horse populations suggests a high level of vector-horse contact. This study aims to characterize the mosquito species usually involved in WNV transmission in horse stables in Madagascar. Five horse stables were investigated in October and November 2016 in five distinct inland areas. Mosquitoes were collected using double net traps baited with human, poultry or horse as well as light traps. Blood meal identification from engorged females was performed using host-specific PCRs. A total of 2898 adult mosquitoes were collected with Culex (Culex) antennatus (Becker) (40.7%), and Cx. (Cux.) quinquefasciatus Say (14.9%), being the most abundant species. The mosquito abundance varied between horse stables (P < 10^-7 ) and depending on the bait used in the double net traps (P < 0.003). Among the 190 tested blood meals, 119 consisted of single blood meals with 85 from horse, 17 from human, 16 from chicken, one from cattle and 71 consisted of mixed blood meals. The mosquito species collected during this study exhibited a generalist feeding behaviour allowing them to act as bridge vectors between different vertebrate hosts involved in WNV transmission cycle. Their vector status with regard to West Nile fever epidemiology is reviewed.

Seasonal population dynamics and a role as natural vector of Leucocytozoon of black fly, Simulium chumpornense Takaoka & Kuvangkadilok

The black fly, Simulium chumpornense Takaoka & Kuvangkadilok, is suspected to be a natural vector of Leucocytozoon. In this study, seasonal variation in abundance of the adult fly and molecular detection of Leucocytozoon in S. chumpornense and in domestic chicken was investigated in northeastern Thailand. A total of 10,416 female adults were obtained by monthly collection for one year at six sampling sites. There was a peak of abundance in the dry season (March - May) when more than 74% of the specimens were collected. An increased number of suitable habitats for immature stages during the dry season is potentially a factor driving dry season abundance. Molecular genetic investigations revealed that S. chumpornense harbored the infectious stage of Leucocytozoon sp. indicating that it is a natural vector of this parasite. Blood smear screening for the parasite in domestic chickens found a considerable prevalence (52%) of Leucocytozoon spp. infections. The cytochrome b sequences of this parasite in domestic chickens comprised two lineages. One lineage was closely related to Leucocytozoon sp. found in S. chumpornense and another matched with L. schoutedeni. Therefore, S. chumpornense is a vector of Leucocytozoon sp. while L. schoutedeni is possibly transmitted by other ornithophilic black fly species.

Cattle-induced eutrophication favours disease-vector mosquitoes

Free-range cattle rearing in arid landscapes contributes profoundly to ecosystem degradation. Cattle dung nutrification in aquatic habitats potentially shapes species diversity and abundance due to resource availability. These nutrient-enriched environments may increase oviposition by mosquitoes and influence proliferation of disease vectors. Here, we examined mosquito larval abundance of Culex pipiens pipiens (culicine) and an unidentified Anopheles (anopheline) species across different concentration treatments of nutrient (cattle dung) loadings (T1-T4; 1 g L^-1, 2 g L^-1, 4 g L^-1 and 8 g L^-1, respectively) in a randomised outdoor mesocosm experiment. The experiment was run for two weeks post-dung inoculation (Day 7 to 21), with mosquito larvae collected (Day 14 and 21), identified and quantified. Higher dung nutrient concentrations significantly increased mosquito larval abundance relative to dung-free controls. Culicine larvae were 26-times more abundant than anopheline on average. Higher dung concentrations also tended to promote more rapid development in larval mosquitoes. With no colonisation by mosquito larvae in the control treatments, we conclude that the input of dung in aquatic ecosystems promotes vector development and abundance with the potential to increase risk of mosquito-borne infections. We therefore recommend sustainable management policies that tackle likely ecological disservices attributable to free-ranging livestock communities.

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.

Impact of deforestation on the abundance, diversity, and richness of Culex mosquitoes in a southwest Cameroon tropical rainforest

Deforestation is a major threat to biodiversity but little data exist on how deforestation in real-time affects the overall mosquito species community despite its known role in the transmission of diseases. We compared the abundance and diversity of Culex mosquitoes before and after deforestation along a gradient of three different anthropogenic disturbance levels in a tropical rainforest in southwestern Cameroon. The collections were conducted in unlogged forest (January, 2016), selectively logged forest (January, 2017), and within a young palm plantation (October, 2017) using net traps, sweep nets, resting traps, and dipping for immature stages in water bodies. Mosquitoes were morphologically identified to subspecies, groups, and species. A total of 2,556 mosquitoes was collected of which 1,663 (65.06%) belong to the genus Culex, (n=427 (25.68%) in the unlogged forest; n=900 (54.12%) in the selectively logged forest; and n=336 (20.2%) in the young palm plantation) with a significant difference among the habitats. Diversity and richness of mosquitoes varied significantly among habitats with the highest values found in the selectively logged forest (H=2.4; DS=0.87; S=33) and the lowest value in the unlogged forest (H=1.37; DS=0.68; S=13). The results of this study showed that deforestation affects the abundance and diversity of Culex mosquitoes and favors the invasion of anthropophilic mosquitoes. Higher mosquito abundance and diversity in the selectively logged forest than in the pristine forest is notable and some explanations for these differences are discussed.

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.

Protozoan parasites in Culex pipiens mosquitoes in Vienna

Avian malaria (Plasmodium spp.) and kinetoplastid (Trypanosoma spp.) parasites are common vector-borne pathogens in birds worldwide; however, knowledge about vector competence of different mosquito species is currently lacking. For a pilot project examining vector competence of mosquitoes of the Culex pipiens complex and Culex torrentium for protozoan parasites in the city of Vienna, 316 individual mosquitoes were sampled in the months June–August 2017 around the campus of the Veterinary University of Vienna. Since vector competence for avian Plasmodium can only be ascertained by finding infectious sporozoites in mosquito salivary glands, special emphasis was on examining these, or at least insect thoraxes, which contain the salivary glands. After species identification, the mosquitoes were processed in three different ways to determine the best method of visually detecting protozoan parasites in salivary glands: (1) microscopic examination of individual, fixed and Giemsa-stained salivary glands, (2) microscopic examination of stained sections of individually fixed and embedded mosquito thoraxes and (3) stained sections of individual whole insects. Material from all three groups was also subjected to PCR to detect avian haemosporidian and trypanosomatid parasite DNA. PCR was performed on all 316 collected mosquitoes, with 37 pools (n = 2–10) of 263 individuals and 53 single individuals in all together 90 PCR reactions. Avian Plasmodium was found in 18 (20%) and trypanosomatid parasites were found in 10 (11.1%) of the examined samples and pools yielded a higher proportion of positives than did individual samples. Six different species of protozoan parasites were identified, namely Plasmodium vaughani SYAT05 which was the most common, P. elongatum GRW6, P. relictum SGS1, Trypanosoma avium, T. culicavium and Crithidia dedva. Seventy-seven mosquito salivary glands were dissected and stained with Giemsa solution. Of these, one (1.3%) featured sporozoites and one (1.3%) trypanosomatid parasites. While the trypanosomes were identified as T. avium, the avian Plasmodium species were present in a mixed infection with P. vaughani SYAT05 as the dominant species. In conclusion, mosquitoes of the Culex pipiens complex are very likely vectors of different avian Plasmodium and Trypanosoma species and PCR was the most successful and reliable method for parasite detection in mosquito samples, delivering higher rates and more accurate results. The visual detection of parasite stages in the salivary glands was more difficult and only a few specimens were detected using Giemsa stain and chromogenic in situ hybridization. For further studies on vector competence of different protozoan parasites in mosquitoes, the use of PCR-based methods would be preferable.

Avian malaria on Madagascar: prevalence, biodiversity and specialization of haemosporidian parasites

Previous studies about geographic patterns of species diversity of avian malaria parasites and others in the Order Haemosporida did not include the avian biodiversity hotspot Madagascar. Since there are few data available on avian malaria parasites on Madagascar, we conducted the first known large-scale molecular-based study to investigate their biodiversity. Samples (1067) from 55 bird species were examined by a PCR method amplifying nearly the whole haemosporidian cytochrome b gene (1063 bp). The parasite lineages found were further characterized phylogenetically and the degree of specialization was determined with a newly introduced host diversity index (Hd). Our results demonstrate that Madagascar indeed represents a biodiversity hotspot for avian malaria parasites as we detected 71 genetically distinct parasite lineages of the genera Plasmodium and Haemoproteus. Furthermore, by using a phylogenetic approach and including the sequence divergence we suspect that the detected haemosporidian lineages represent at least 29 groups i.e. proposed species. The here presented Hd values for each parasite regarding host species, genus and family strongly support previous works demonstrating the elastic host ranges of some avian parsites of the Order Haemosporida. Representatives of the avian parasite genera Plasmodium and Leucocytozoon tend to more often be generalists than those of the genus Haemoproteus. However, as demonstrated in various examples, there is a large overlap and single parasite lineages frequently deviate from this rule.

Avian haemosporidians from rain forests in Madagascar: Molecular and morphological data of the genera Plasmodium, Haemoproteus and Leucocytozoon

The diversity of the haemosporidian genera Plasmodium, Haemoproteus and Leucocytozoon in birds from rain forests in Madagascar is characterized combining techniques of PCR and microscopy and based on the examination of 72 host individuals of 23 species in 15 families. High total prevalence of haemosporidians (68%) is detected, with Leucocytozoon infections being predominant (59.7%) and lower comparable prevalence of Plasmodium (18.0%) and Haemoproteus (23.6%) infections. Using mitochondrial cytochrome b (cytb) marker, 23 genetically distinct lineages are identified: 9 of Plasmodium spp., 6 of Haemoproteus spp. and 8 of Leucocytozoon spp. Fifteen of all lineages have not been reported by previous studies. This study provides the first data on haemosporidian morphological and molecular diversity found in the endemic families Vangidae and Bernieriidae. Two haemoproteid species, Haemoproteus fuscae Mello and Fonseca, 1937 and H. killangoi Bennett and Peirce, 1981, are redescribed based on the present samples and linked to the cytb lineages hCELEC01 and hZOSMAD01, respectively. Phylogenetic analysis is performed to test the relationship of the discovered new lineages with parasites from closely related avian hosts suggesting that multiple colonisation of hosts by haemosporidian parasites has occurred on the island.

Extremely low Plasmodium prevalence in wild plovers and coursers from Cape Verde and Madagascar

Background

Relatively little is known about the prevalence of blood parasites in shorebirds, especially those breeding in the tropics. The prevalence of blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon was assessed in blood samples from Kentish plovers and cream-coloured coursers in Cape Verde, and samples of Kittlitz’s plovers, Madagascar plovers and white-fronted plovers in Madagascar.

Results

Only two of these samples were positive for Plasmodium: a Kittlitz’s plover was infected by a generalist lineage of Plasmodium that has already been reported in Europe and Africa, while in a white-fronted plover direct sequencing revealed a previously un-described Plasmodium lineage.

Conclusion

Potential explanations for the low prevalence of blood parasites include the scarcity of vectors in habitats used by these bird species and their resistance to parasitic infections.