Avian malaria parasites of the genus Plasmodium (Haemosporida, Plasmodiidae), are cosmopolitan mosquito-transmitted haematozoa [1, 2]. In contrast to human malaria, avian malaria has a worldwide distribution and is caused by approximately 50 species of Plasmodium [3, 4]. The widespread geographic distribution of avian malaria parasites and their broad range of avian hosts make them excellent models for exploring the ecological and evolutionary dynamics of vector-host-parasite associations.
Although some 50 species of avian Plasmodium have been identified using phenotypic characters [2, 4], molecular data reveal remarkable genetic diversity of these parasites, indicating that the number of avian Plasmodium species and their taxonomic diversity may be greater than is accepted in the current classifications . Avian Plasmodium are transmitted wherever the mosquitoes, susceptible birds and minimum temperature and humidity requirements are available. Many species of avian Plasmodium appear to have evolved with their hosts and do not typically cause lethal disease , although there are numerous reported cases of pathology and even high mortalities when naïve birds are exposed for the first time [6–8].
Although general patterns of the epizootiology of avian malaria have been well studied [9–11], little is known about the vectors and the parasites diversity within the vectors, an essential step in the avian malaria transmission cycle. Species within multiple mosquito genera (Culex, Aedes, Culiseta, Anopheles, Mansonia and Aedeomyia) have been implicated in the transmission of different species of avian Plasmodium [2, 12–16]. Despite the presence of numerous ornithophilic species within the genus Coquillettidia only one report was found relating presence of sporozoites of Plasmodium gallinaceum and an unidentified Plasmodium sp. in the salivary glands of Coquillettidia crassipes . Recently, DNA of a Haemoproteus species was isolated from 1/77 Coquillettidia xanthogaster collected in Vanuatu ; however, it is unclear if this parasite completes its life cycle in this mosquito.
In this study, the role of Coquillettidia spp. (Diptera, Culicidae) collected in the lowland forests of Cameroon as potential vectors of avian malarial parasites was explored. Coquillettidia is treated as a genus [19–21], rather than a subgenus of Mansonia [22–25]. Worldwide there are 57 described Coquillettidia species  with twenty-two from Africa. Coquillettidia spp. adults are medium in size and can easily be confused with Aedes and Culex mosquitoes, but all species (shared only with the genus Mansonia) have the unusual larval behaviour of attaching to air cells of aquatic plants to obtain oxygen for respiration . Immature stages are mostly found in permanent bodies of water and only float to the surface as pupae just prior to eclosion. The integuments of most of the African species are bright yellow or have a yellow to greenish hue, which readily distinguishes them from other African mosquitoes . Only one species, Coquillettidia metallica, has a dark body and legs .
During recent surveys of the lowland forests of Cameroon four species from the genus, (Coquillettidia aurites, Coquillettidia pseudoconopas, C. metallica and Coquillettidia maculipennis) were collected. These four species are endemic to Africa with known distributions in West, Central and East Africa [27, 28]. They all are crepuscular [29, 30], rarely bite man or other mammals  and prefer birds as hosts [32, 33]. West Nile, Middleberg and Sindbis viruses have been isolated from C. metallica; while Tataguine, Simbu and Usutu viruses, closely related to West Nile and formerly recorded as this pathogen, have been isolated from C. aurites [32, 34]. The viruses associated with C. pseudoconopas are not yet known . Prior to this study, none of these species were implicated as vectors of malaria.
The avifauna of Cameroon is relatively well-studied and prior studies for blood parasites have identified Plasmodium spp. in many of the avian hosts [2, 4, 35–37], but little is known of the vectors.
The objectives of this paper were to: 1) use high throughput molecular genetic screening techniques of wild collected mosquito heads and thoraces to test for the presence of Plasmodium spp., 2) investigate the spatial distribution of the parasite mitochondrial cytochrome b (cyt b) sequence lineages found in Coquillettidia spp., 3) microscopically examine the salivary glands of the wild-caught mosquitoes for presence of sporozoites, which are the last stage of development of malaria parasites in vectors, and 4) compare the distribution and phylogenetic relationships of these lineages to published lineages found in other mosquito vectors and birds in Cameroon. This is the first molecular exploration of avian vector-avian host-malaria parasite relationships in Africa.