Achieving high coverage of larval-stage mosquito surveillance: challenges for a community-based mosquito control programme in urban Dar es Salaam, Tanzania
Source: BioMed Central, 30 Dec 2009
Background – Preventing malaria by controlling mosquitoes in their larval stages requires regular sensitive monitoring of vector populations and intervention coverage. The study assessed the effectiveness of operational, community-based larval habitat surveillance systems within the Urban Malaria Control Programme (UMCP) in urban Dar es Salaam, Tanzania.
Methods – Cross-sectional surveys were carried out to assess the ability of community-owned resource persons (CORPs) to detect mosquito breeding sites and larvae in areas with and without larviciding. Potential environmental and programmatic determinants of habitat detection coverage and detection sensitivity of mosquito larvae were recorded during guided walks with 64 different CORPs to assess the accuracy of data each had collected the previous day.
Results – CORPs reported the presence of 66.2% of all aquatic habitats (1,963/2,965), but only detected Anopheles larvae in 12.6% (29/230) of habitats that contained them. Detection sensitivity was particularly low for late-stage Anopheles (2.7%, 3/111), the most direct programmatic indicator of malaria vector productivity. Whether a CORP found a wet habitat or not was associated with his/her unfamiliarity with the area (Odds Ratio (OR) [95% confidence interval (CI)] = 0.16 [0.130, 0.203], P<0.001), the habitat type (P<0.001) or a fence around the compound (OR [95%CI] = 0.50 [0.386, 0.646], P<0.001). The majority of mosquito larvae (Anophelines 57.8 % (133/230) and Culicines 55.9% (461/825) were not reported because their habitats were not found. The only factor affecting detection of Anopheline larvae in habitats that were reported by CORPs was larviciding, which reduced sensitivity (OR [95%CI] = 0.37 [0.142, 0.965], P=0.042).
Conclusions – Accessibility of habitats in urban settings presents a major challenge because the majority of compounds are fenced for security reasons. Furthermore, CORPs under-reported larvae especially where larvicides were applied. This UMCP system for larval surveillance in cities must be urgently revised to improve access to enclosed compounds and the sensitivity with which habitats are searched for larvae.
There is no malaria in Nairobi, say experts – City residents may have been taking expensive malaria drugs for years when the disease is negligible, if not non-existent, in Nairobi.
Research carried out in 2008 by reputable organisations indicates there is no malaria in the city. The firms that conducted the study include the Kenya Medical Research Institute, the UK’s Oxford and Southampton universities, London School of Tropical Medicine and the African Population and Health Research Centre in Nairobi.
Despite evidence that there could be no malaria in Nairobi, patients especially children with fever were treated for the disease and with the wrong drugs in most instances, says the study, which was prepared for an international conference on health.
Some 983 people in Korogocho, Nairobi were tested and only three indicated they could be having the parasite. Further testing, however, found them to be negative.
“Microscopic examination showed zero prevalence,” says the study titled Malaria Infection in an Urban Informal Settlement in Nairobi: A myth or reality.
Of the group, 170 had run a fever in the last 14 days with more than half being treated for malaria with drugs that are not recommended by the government.
“Only four cases were treated using the recommended first-line treatment,” says the study. The findings contradict the perception of a rising incidence of malaria in Nairobi attributed to warm climate that is more habitable for mosquitoes that carry the disease.
If the findings are validated, malaria may be one problem less to worry about for people in Nairobi. However a more emerging and potent threat will be outlined at the conference on Thursday.
Mr J. O. Ogendo of Maseno University says the biggest danger to city residents, after muggers and robbers, are road accidents targeting pedestrians and cyclists. The researcher recommends that city planners consider pedestrian-friendly policies for Nairobi.
MANGALORE Sept 8: Health officials identified 830 cases of malaria infection within the city corporation limits in last month. In addition, 71 cases of affliction have been reported from rural areas. This is said to be the highest number of cases recorded in the district this year.District health officer H. Jagannath said that the rural-urban divide was a historical feature of the district.
“The urban centres are always ahead of rural areas in the prevalence of the disease because there are more sources for mosquito breeding in the city. The female Anopheles mosquito thrives on filthy conditions,” he said.
He said that 7,976 blood samples were collected from within the corporation limits, compared to over 18,000 collected in the rural areas. “It cannot be concluded that the cases reported from rural areas are less because our diagnostic machinery is lacking,” he said, in response to a query.
A majority of the malaria cases identified in the city had been caused by the less deadly parasite Plasmodium viviax (PV).