Host selection of potential West Nile virus vectors in Puerto Barrios, Guatemala, 2007.

The selection of vertebrate hosts by Culex mosquitoes relative to West Nile virus (WNV) transmission in neotropical countries such as Guatemala is not described. This study determined the feeding patterns of Cx. quinquefasciatus and Cx. nigripalpus and estimated the relative contribution of two common and frequently infected wild bird species, Turdus grayi and Quiscalus mexicanus, to WNV transmission. Engorged mosquitoes were collected from rural and urban habitats after the dry and wet seasons in the Department of Izabal in 2007. Host selection by Cx. nigripalpus varied significantly between urban and rural habitats. Both Cx. quinquefasciatus and Cx. nigripalpus fed predominantly on chickens and other domestic animals. Blood meals from wild birds were rare, accounting for 1.1% of blood meals identified from Cx. quinquefasciatus and 6.5% of blood meals from Cx. nigripalpus. Transmission of WNV by these two mosquito species may be dampened by extensive feeding on reservoir-incompetent hosts.

Comparison of engorged Culex quinquefasciatus collection and blood-feeding pattern among four mosquito collection methods in Puerto Barrios, Guatemala, 2007.

Investigators have used a variety of techniques to sample resting, engorged mosquitoes for the purposes of studying mosquito blood-feeding behavior. However, evidence exists that mosquito blood-feeding patterns may vary according to collection method. Engorged mosquitoes were collected from rural and urban habitats after the 2007 dry (July) and wet (December) seasons in the Department of Izabal, Guatemala, with the use of Centers for Disease Control and Prevention (CDC) light traps, gravid traps, and aspiration from plastic pots and vegetation. We evaluated the utility of plastic pots as sampling tools for engorged Culex mosquitoes and compared Cx. quinquefasciatus blood host identities among collection methods. The array of vertebrate hosts supplying blood to Cx. quinquefasciatus did not differ significantly by method of collection. The density of engorged Cx. quinquefasciatus per trap-night was not significantly different between CDC light traps, gravid traps, and plastic pots; however, there was a significantly higher proportion of total mosquitoes that were engorged collected from pots than from either CDC light traps or gravid traps.

Detection of West Nile viral RNA from field-collected mosquitoes in tropical regions by conventional and real-time RT-PCR.

West Nile virus (WNV) is an emerging mosquito-borne flavivirus, which has rapidly spread and is currently widely distributed. Therefore, efforts for WNV early detection and ecological surveillance of this disease agent have been increased around the world. Although virus isolation is known to be the standard method for detection and identification of viruses, the use of RT-PCR assays as routine laboratory tests provides a rapid alterative suitable for the detection of viral RNA on field-collected samples. A method for WNV RNA genome detection in field-collected mosquitoes is presented in this chapter. This method has been designed for virus surveillance in tropical regions endemic for other flaviviruses. Reverse Transcriptase-PCR (RT-PCR) assays, both standard and real time, to detect WNV and other flaviviruses are described. A first screening for flavivirus RNA detection is performed using a conventional RT-PCR with two different sets of flavivirus consensus primers. Mosquito samples are then tested for WNV RNA by a real-time (TaqMan) RT-PCR assay. Sample preparation and RNA extraction procedures are also described.

Blood typing in Saimiri sciureus monkeys: influence of anti-red blood cell alloantibodies on Plasmodium falciparum parasitaemia in vivo.

The Saimiri sciureus monkey is a well-established host for experimental studies with human malaria parasites. During the course of iterative inoculations with Plasmodium falciparum parasitised red blood cells (RBC), anti-RBC alloantibodies were detected in the sera of two of eight Saimiri monkeys. These anti-RBC antibodies were further used to investigate RBC phenotypes in 35 colony-reared Saimiri monkeys by flow cytometry. Three RBC phenotypes (named I-III) were observed. Their distribution was I (86%), II (11%) and III (3%). Using the Palo Alto FUP-2 strain, a variant P. falciparum line insensitive to hyperimmune serum and the passive transfer of anti-RBC alloantibodies, a dramatic drop in parasite growth was documented in an incompatible monkey.