Survey of Anopheles mosquitoes (Diptera:Culicidae) in West Sumba District, Indonesia.

In August 2007, mosquitoes were collected using four different collection methods at 2 upland interior and 2 coastal villages in West Sumba District, East Nusa Tenggara Province, Indonesia. Methods included human-baited and unbaited tent and malaise traps, human-landing collections (HLC), and unbaited CDC light traps. Mosquitoes were identified to species by morphological characters and all anophelines were tested for malaria circumsporozoite protein (CSP) using an enzyme-linked immunosorbent assay (ELISA). During six trap nights, 4,174 Anopheles mosquitoes belonging to 13 species were captured and identified: An. aconitus, An. annularis, An. barbirostris, An. flavirostris, Hyrcanus Group species, An. indefinitus, An. kochi, An. leucosphyrus group, An. maculatus s.l., An. subpictus s.l., An. sundaicus s.l., An. tessellatus, and An. vagus. Of potential disease vectors, An. annularis, An. subpictus, and An. vagus were the most frequently collected species in the upland interior sites, whereas An. sundaicus, An. subpictus, and An. vagus were most commonly found along the coast. The predominant species from evening human-landing collections (mosquitoes per human) were An. subpictus and An. vagus in the upland interior and An. sundaicus along the coast. All mosquitoes were non-reactive for Plasmodium CSP. One specimen of the An. leucosphyrus group was captured from indoor HLC in Tenateke Village, an upland interior location. This finding appears to represent a new collection record for Sumba Island.

Evaluation of a dipstick malaria sporozoite panel assay for detection of naturally infected mosquitoes.

The determination of the presence or absence of malaria sporozoites in wild-caught Anopheles mosquitoes remains an integral component to the understanding of the transmission dynamics in endemic areas. To improve that capability, there has been on-going development of a new device using dipstick immunochromatographic technology for simplifying the testing procedure and reducing the time required to obtain results. As part of a larger multi-center effort, we evaluated the sensitivity and specificity of a prototype malaria sporozoite antigen panel assay (Medical Analysis Systems, Camarillo, CA) against three human Plasmodium species/polymorphs. The wicking (dipstick) assay was compared against a standard parasite antigen capture enzyme-linked immunosorbent assay (ELISA) for the detection of human circumsporozoite protein (CSP) in wild-caught mosquitoes. Over 6,800 Anopheles mosquitoes, representing 20 species collected from malaria endemic areas of Indonesia were tested either individually or in pools of up to 10 mosquitoes each. From 1,442 pooled test strip assays and ELISA formats, nine mosquito pools were found reactive for P.falciparum, P. vivax 210, or P. vivax 247 CSP. There was complete concordance between test strip results and ELISA results. Sensitivity was 100% and given some minor problems with false positives or negatives, specificity (n = 488) was 97%. Most strips judged as false positive produced very weak signals compared with negative control blank strips and paired ELISA-negative samples. The dipstick test proved technically simpler to perform and interpret than the ELISA and results were obtained within 15 min of exposure to mosquito suspension. This qualitative assay appears an attractive alternative to the CSP ELISA for detection of sporozoites in fresh or dried mosquitoes.

Laboratory and field testing of bednet traps for mosquito (Diptera: Culicidae) sampling in West Java, Indonesia.

Surveillance of medically important mosquitoes is critical to determine the risk of mosquito-borne disease transmission. The purpose of this research was to test self-supporting, exposure-free bednet traps to survey mosquitoes. In the laboratory we tested human-baited and unbaited CDC light trap/cot bednet (CDCBN) combinations against three types of traps: the Mbita Trap (MIBITA), a Tent Trap (TENT), and a modified Townes style Malaise trap (TSM). In the laboratory, 16 runs comparing MBITA, TSM, and TENT to the CDCBN were conducted for a total of 48 runs of the experiment using 13,600 mosquitoes. The TENT trap collected significantly more mosquitoes than the CDCBN. The CDCBN collected significantly more than the MBITA and there was no difference between the TSM and the CDCBN. Two field trials were conducted in Cibuntu, Sukabumi, West Java, Indonesia. The first test compared human-baited and unbaited CDCBN, TENT, and TSM traps during six nights over two consecutive weeks per month from January, 2007 to September, 2007 for a total of 54 trapnights. A total of 8,474 mosquitoes representing 33 species were collected using the six trapping methods. The TENT-baited trap collected significantly more mosquitoes than both the CDCBN and the TSM. The second field trial was a comparison of the baited and unbaited TENT and CDCBN traps and Human Landing Collections (HLCs). The trial was carried out from January, 2008 to May, 2008 for a total of 30 trap nights. A total of 11,923 mosquitoes were collected representing 24 species. Human Landing Collections captured significantly more mosquitoes than either the TENT or the CDCBN. The baited and unbaited TENT collected significantly more mosquitoes than the CDCBN. The TENT trap was found to be an effective, light-weight substitute for the CDC light-trap, bednet combination in the field and should be considered for use in surveys of mosquito-borne diseases such as malaria, arboviruses, and filariasis.

Bionomics of Anopheles spp. (Diptera: Culicidae) in a malaria endemic region of Sukabumi, West Java, Indonesia.

A 15-month bionomic study of Anopheles species was conducted in two ecologically distinct villages (coastal and upland) of Sukabumi District, West Java, Indonesia from June 2006 to September 2007. Mosquitoes were captured using human-landing collections at both sites. During the study, a total of 17,100 Anopheles mosquitoes comprising 13 Anopheles species were caught: 9,151 at the coastal site and 7,949 at the upland site. Anopheles barbirostris, Anopheles maculatus, and Anopheles vagus were the predominant species caught at the coastal site, and Anopheles aconitus, Anopheles barbirostris, and An. maculatus predominated in the upland site. Overall, species were exophagic at both sites, but there was variation between species. Anopheles aconitus was endophagic at the coastal site, exophagic at the upland site, collected most often in April 2007 and had a peak landing time between 22:00 and 23:00. Anopheles sundaicus was only collected at the coastal site, exophagic, collected most often in October 2006, and had a peak landing time between 19:00 and 20:00. Potential malaria vector species such An. aconitus, An. maculatus, and An. sundaicus were present throughout the year. None of the 7,770 Anopheles tested using CSP-ELISA were positive for malaria, although the risk for malaria outbreaks in Sukabumi district remains high.