In Sub Saharan Africa where most of the malaria cases and deaths occur, members of the
Anopheles
gambiae
species complex and
Anopheles funestus
species group are the important malaria vectors. Control efforts
against these vectors in Tanzania like in most other Sub Saharan countries have failed to achieve the set objectives of
eliminating transmission due to scarcity of information about the enormous diversity of
Anopheles
mosquito species
and their susceptibility status to insecticides used for malaria vector control. Understanding the diversity and
insecticide susceptibility status of these vectors and other factors relating to their importance as vectors (such as
malaria transmission dynamics, vector biology, ecology, behaviour and population genetics) is crucial to developing a
better and sound intervention strategies that will reduce man-vector contact and also manage the emergency of
insecticide resistance early and hence a success in malaria control. The objective of this review was therefore to
obtain the information from published and unpublished documents on spatial distribution and composition of malaria
vectors, key features of their behaviour, transmission indices and susceptibility status to insecticides in Tanzania. All
data available were collated into a database. Details recorded for each data source were the locality,
latitude/longitude, time/period of study, species, abundance, sampling/collection methods, species identification
methods, insecticide resistance status, including evidence of the kdr allele, and
Plasmodium falciparum
sporozoite
rate. This collation resulted in a total of 368 publications, encompassing 806,273 Anopheles mosquitoes from 157 georeferenced
locations being collected and identified across Tanzania from 1950s to 2010. Overall, the vector species
most often reported included
An. gambiae complex (66.8%),
An. funestus complex (21.8%),
An. gambiae s.s. (2.1%) and
An. arabiensis
(9%). A variety of sampling/collection and species identification methods were used with an increase in
molecular techniques in recent decades. Only 32.2% and 8.4% of the data sets reported on sporozoite analysis and
entomological inoculation rate (EIR), respectively which highlights the paucity of such important information in the
country. Studies demonstrated efficacy of all four major classes of insecticides against malaria vectors in Tanzania
with focal points showing phenotypic resistance. About 95% of malaria entomological data was obtained from northeastern
Tanzania. This shows the disproportionate nature of the available information with the western part of the
country having none. Therefore it is important for the country to establish entomological surveillance system with
state of the art to capture all vitally important entomological indices including vector bionomics in areas of Tanzania
where very few or no studies have been done. This is vital in planning and implementing evidence based malaria
vector control programmes as well as in monitoring the current malaria control interventions.
