Insights Into Resting Behavior of Malaria Vector Mosquitoes in Mutare and Mutasa Districts of Manicaland Province, Zimbabwe.

A study was conducted to investigate the current resting behavior of malaria vectors in Mutare and Mutasa districts, Zimbabwe. Mosquitoes were captured using pyrethrum spray collection, prokopac aspirator, pit shelter, and exit trap methods. Mosquitoes were sorted and identified using morphological key and polymerase chain reaction (PCR) techniques. The Anopheles funestus group constituted 97%, whereas Anopheles gambiae complex mosquitoes were few (3%). Endophilic collections in both species were five times greater than exophilic catches. The endophilic trait was further demonstrated by gravid to fed index (gravid/fed) of constantly more than 1. Nearly 90% endophilic An. funestus populations were collected on sprayable and 10% collected on unsprayable surfaces. Of the sprayable surfaces, 56% were collected on the roofs, with 44% on the walls. Of those on the walls, 44, 22, and 34% were caught on wall heights >1, 1.0-1.5, <1.5 m from the ground, respectively. Of the gravid An. funestus caught, nearly two-thirds were collected exiting pyrethroid-treated structures, with a 24-h mortality of less than 10%. The PCR analysis of 120 specimens taken randomly from the An. funestus group was all An. funestus s.s. The present work indicates that for effective malaria control in Mutare and Mutasa districts using indoor residual spraying, both walls and roofs must be sprayed.

Urban malaria transmission in Mutare City; an unlikely phenomenon.

OBJECTIVE: With an average altitude of 1,113 m above sea level and a mean maximum temperature of 28.6 degrees C, malaria transmission is possible in Mutare. Against transmission is the regular occurrence of ground frost. We reviewed epidemiological data and undertook a survey for the Anopheles vector. DESIGN: The Anopheles survey used standard techniques for sampling larvae and adult mosquitoes. Species identification was done by the polymerase chain reaction (PCR) technique. A random sample of blood slides was examined at the Blair Laboratory. Patient residence was determined from the outpatient register. Daily maximum and minimum temperatures monitored from the Mutare Fire Station, were obtained from the Meteorology Office in Harare. SETTING: Mutare city and suburbs. RESULTS: There was no evidence of rising temperatures in Mutare. Only non-vector Anopheles mosquitoes were identified (An. quadriannulatus and An. pretoriensis). One slide positive case had gametocytes present. Mapping generally showed no clustering, but there were two possible transmission foci. CONCLUSION: Temperatures are high enough, but winter lows (< 18 degrees C) do not support malaria transmission in Mutare. The Anopheles survey did not find the vector. Two suggestive clusters were mapped. While present data do not support ongoing malaria transmission within Mutare, in the past, An. gambiae, An. fenestus and An. pretoriensis were recorded. Careful monitoring will be needed.

Laboratory colonization of Anopheles quadriannulatus from sympatry with other sibling species of the Anopheles gambiae complex in Zimbabwe.

A laboratory colony of the mosquito Anopheles quadriannulatus was established from a wild population occurring sympatrically with An.arabiensis in Zimbabwe. These sibling species are members of the An.gambiae Giles complex and were distinguished primarily by means of their specific polytene chromosome banding patterns. By using an ox-baited trap, we sampled selectively for the more zoophilic An.quadriannulatus. It was confirmed that An.quadriannulatus has the diagnostic slow allozyme of aspartate aminotransferase (AAT95/95). In a mixed population under laboratory conditions, An.arabiensis displaced An.quadriannulatus within eight generations, without introgression. Colonization of An.quadriannulatus was facilitated by pooling the progeny from wild-caught mothers of confirmed identity and by using a specially adapted cage to promote mating.