Haemosporidian prevalence, parasitaemia and aggregation in relation to avian assemblage life history traits at different elevations.

The transmission of vector-borne protozoa such as parasites of the Order Haemosporida is dependent on both biotic and abiotic factors such as host life history traits and environmental conditions. This study aimed to identify the variables that determine haemosporidian prevalence, parasitaemia and aggregation within the context of elevation and avian life history traits in Central Veracruz, Mexico. We sampled 607 birds from 88 species; we used microscopy and the mtDNA cytochrome b gene to detect parasites. We found an overall prevalence of 32.3%. Haemosporidian prevalence was 21.6% in tropical sub-deciduous forest (at sea level), 38% in tropical deciduous forest (265 m above sea level (asl)), 19.4% in montane cloud forest (1630 m asl), and 51.7% in pine-oak forest (2790 m asl). The prevalence of each parasite genus was strongly influenced by elevation (a proxy of habitat type). Plasmodium showed the highest prevalence at low elevation. Haemoproteus increased in prevalence with elevation. Leucocytozoon displayed the highest prevalence at the highest elevation (pine-oak forest). Haemoproteus spp. and Leucocytozoon spp. prevalences were higher in open cup than in closed nests. Haemoproteus prevalence and haemosporidian parasitaemia were lower in solitary birds than birds with pairing and gregarious behavior. Haemosporidian aggregation decreased with elevation, yielding the significantly lowest values at the pine-oak forest. Elevation distribution patterns of prevalence for each genus were similar to those previously reported in other geographical areas (e.g., South America, Europe).

Insights into the Host Specificity of Mosquito-Borne Flaviviruses Infecting Wild Mammals.

Mosquito-borne flaviviruses (MBFVs) are of public and animal health concern because they cause millions of human deaths annually and impact domestic animals and wildlife globally. MBFVs are phylogenetically divided into two clades, one is transmitted by Aedes mosquitoes (Ae-MBFVs) associated with mammals and the other by Culex mosquitoes (Cx-MBFVs) associated with birds. However, this assumption has not been evaluated. Here, we synthesized 79 published reports of MBFVs from wild mammals, estimating their host. Then, we tested whether the host specificity was biased to sampling and investigation efforts or to phylogenetic relationships using a viral phylogenetic tree drawn from analyzing whole flavivirus genomes obtained in GenBank. We found in total 18 flaviviruses, nine related to Aedes spp. and nine to Culex spp. infecting 129 mammal species. Thus, this supports that vectors are transmitting MBFV across available host clades and that ornithophilic mosquitoes are readily infecting mammals. Although most of the mosquito species are generalists in their host-feeding preferences, we also found a certain degree of MBFV's specificity, as most of them infect closely related mammal species. The present study integrates knowledge regarding MBFVs, and it may help to understand their transmission dynamics between viruses, vectors, and mammal hosts.

Potential Sympatric Vectors and Mammalian Hosts of Venezuelan Equine Encephalitis Virus in Southern Mexico.

Arboviruses are important zoonotic agents with complex transmission cycles and are not well understood because they may involve many vectors and hosts. We studied sympatric wild mammals and hematophagous mosquitoes having the potential to act as hosts and vectors in two areas of southern Mexico. Mosquitoes, bats, and rodents were captured in Calakmul (Campeche) and Montes Azules (Chiapas), between November 2010 and August 2011. Spleen samples from 146 bats and 14 rodents were tested for molecular evidence of Venezuelan equine encephalitis virus (VEEV), eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV), and West Nile virus (WNV) using PCR protocols. Bat ( Artibeus lituratus , Carollia sowelli , Glossophaga soricina , and Sturnira parvidens) and rodent ( Sigmodon hispidus and Oryzomys alfaroi ) species were positive for VEEV. No individuals were positive for WNV, EEEV, or WEEV. A total of 1,298 mosquitoes were collected at the same sites, and five of the mosquito species collected were known VEEV vectors (Aedes fulvus, Mansonia indubitans, Psorophora ferox, Psorophora cilipes, and Psorophora confinnis). This survey simultaneously presents the first molecular evidence, to our knowledge, of VEEV in bats and rodents from southern Mexico and the identification of potential sympatric vectors. Studies investigating sympatric nonhuman hosts, vectors, and arboviruses must be expanded to determine arboviral dynamics in complex systems in which outbreaks of emerging and reemerging zoonoses are continuously occurring.