Entomological Evaluation of Malaria Vectors at Different Altitudes in Hai District, Northeastern Tanzania

Kulkarni, Manisha A.; Kweka, Eliningaya J.; Nyale, E.; Lyatuu, Ester E; Mosha, Franklin W.; Chandramohan, Daniel; Rau, Manfred E.; Drakeley, Chris

doi:10.1603/0022-2585(2006)43[580:eeomva]2.0.co;2

Cited by 30 publications

(19 citation statements)

References 30 publications

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“…Similarly, densities of both immature and adult stages of the vector were observed to decrease significantly with increasing altitude in the area during the period [15,16] and so was the risk of acquiring P. falciparum and Plasmodium vivax malaria [16,21,22]. Density of vectors generally decreases with increasing altitude in highland areas [23]. …”

Section: Discussionmentioning

confidence: 99%

Impact of housing condition on indoor-biting and indoor-resting Anopheles arabiensis density in a highland area, central Ethiopia

Animut

Balkew

Lindtjørn

2013

Malar J

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BackgroundExposure of individuals to malaria infection may depend on their housing conditions as houses serve as biting and resting places of vectors. This study describes the association of housing conditions with densities of indoor-biting and indoor-resting Anopheles arabiensis in Hobe, Dirama and Wurib villages of a highland area in central Ethiopia.MethodsData on housing conditions, including presence of house apertures, number of occupants and number and the type of domestic animal tethered inside, were collected. Indoor-biting mosquitoes were sampled using Centers for Disease Control (CDC) light traps and indoor-resting mosquitoes sampled with pyrethrum spray catches (PSCs) monthly for two years (July 2008 to June 2010). Female anophelines were identified to species and processed. Univariate and general linear estimating equation allowing for repeated measures were used to assess the contribution of housing conditions for indoor-biting and indoor-resting An. arabiensis.ResultsAbout 96% (4,597/4,788) of anophelines were caught inside residential houses. Nine anopheline species were identified, among which An. arabiensis was most prevalent (2,489; 52%). Vectors entering houses were higher in those situated at low (β = 4.475; 95% CI = 3.475-5.476; p <0.001; β = strength of the association) and medium (β = 2.850; 95% CI = 1.975-3.724; p <0.001) altitudes compared to high altitude, and where houses have no windows (β = -0.570; 95% CI = -1.047-0.094; p = 0.019) compared with those that have. Numbers of indoor-resting vectors were higher in those situated at low (β = 6.100; 95% CI = 4.571-7.629; p <0.001) and medium (β = 4.411; 95% CI = 2.284-6.537; p <0.001) altitudes compared to high altitudes, and where houses had open eaves (β =1.201; 95% CI = 0.704-1.698; p <0.001) compared with those that had closed eaves.ConclusionHousing conditions such as presence of open eaves, absence of window, location at low and mid altitudes, were strong predictors of indoor exposure to An. arabiensis bite in a highland area of south-central Ethiopia.

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Section: Discussionmentioning

confidence: 99%

Impact of housing condition on indoor-biting and indoor-resting Anopheles arabiensis density in a highland area, central Ethiopia

Animut

Balkew

Lindtjørn

2013

Malar J

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“…However, densities of samples from PSC followed a more regular decreasing slope of about 3.5-fold along the transect. This spatial evolution of the densities indicated a moderate decline rate compared to the 50% per 86 m rise in altitude observed in Mount Kilimanjaro [26]. …”

Section: Discussionmentioning

confidence: 99%

“…This duration was assessed by mark-release-recapture technique, a method feasible only in localities of high biting rate [48,49]; which is not the case in highlands. An attempt to estimate this entomological factor was carried out by a different method, successfully used before in Tanzania [26]. The duration of gonotrophic cycle was consistently found to be one day shorter for An.…”

Section: Discussionmentioning

confidence: 99%

“…Determination of the duration of gonotrophic cycle was based on the assumption that mortality rate is constant throughout the ovarian cycle. In this case, the fed/gravid ratio is approximately 1:1 for a gonotrophic cycle of 2-days, whereas it would be 1:2 for a 3-days cycle, because of an additional inserted day for half-gravid status [26]. The daily survival rate ( p ) of anopheles was then determined for each altitudinal site of the transect, using Davidson's formula [27]:…”

Section: Methodsmentioning

confidence: 99%

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Bionomics of Anopheline species and malaria transmission dynamics along an altitudinal transect in Western Cameroon

et al. 2010

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BackgroundHighland areas of Africa are mostly malaria hypoendemic, due to climate which is not appropriate for anophelines development and their reproductive fitness. In view of designing a malaria control strategy in Western Cameroon highlands, baseline data on anopheline species bionomics were collected.MethodsLongitudinal entomological surveys were conducted in three localities at different altitudinal levels. Mosquitoes were captured when landing on human volunteers and by pyrethrum spray catches. Sampled Anopheles were tested for the presence of Plasmodium circumsporozoite proteins and their blood meal origin with ELISA. Entomological parameters of malaria epidemiology were assessed using Mac Donald's formula.ResultsAnopheline species diversity and density decreased globally from lowland to highland. The most aggressive species along the altitudinal transect was Anopheles gambiae s.s. of S molecular form, followed in the lowland and on the plateau by An. funestus, but uphill by An. hancocki. An. gambiae and An. ziemanni exhibited similar seasonal biting patterns at the different levels, whereas different features were observed for An. funestus. Only indoor resting species could be captured uphill; it is therefore likely that endophilic behaviour is necessary for anophelines to climb above a certain threshold. Of the ten species collected along the transect, only An. gambiae and An. funestus were responsible for malaria transmission, with entomological inoculation rates (EIR) of 90.5, 62.8 and zero infective bites/human/year in the lowland, on the plateau and uphill respectively. The duration of gonotrophic cycle was consistently one day shorter for An. gambiae as compared to An. funestus at equal altitude. Altitudinal climate variations had no effect on the survivorship and the subsequent life expectancy of the adult stage of these malaria vectors, but most probably on aquatic stages. On the contrary increasing altitude significantly extended the duration of gonotrophic cycle and reduced: the EIR, their preference to human blood and consequently the malaria stability index.ConclusionMalaria epidemiological rooting in the outskirts of Western Cameroon highlands evolves with increasing altitude, gradually from stable to unstable settings. This suggests a potential risk of malaria epidemic in highlands, and the need for a continuous epidemiological surveillance.

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“…Sample of resting mosquitoes for blood meal analyses are therefore important for selecting appropriate control strategies, particularly as vector population composition may become dominated by zoophagic species once high coverage by insecticide-treated nets [36-38] or indoor residual spraying [39-41] is achieved. ITT and HLC both primarily sample host-seeking mosquitoes [22-24] so either resting collection techniques [42-44] or window exit traps (WET) [44] are required to effectively characterize the feeding behaviours of vector mosquitoes that are relevant to intervention efficacy and selection.…”

Section: Introductionmentioning

confidence: 99%

Monitoring mosquitoes in urban Dar es Salaam: Evaluation of resting boxes, window exit traps, CDC light traps, Ifakara tent traps and human landing catches

et al. 2011

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BackgroundIfakara tent traps (ITT) are currently the only sufficiently sensitive, safe, affordable and practical method for routine monitoring host-seeking mosquito densities in Dar es Salaam. However, it is not clear whether ITT catches represent indoors or outdoors biting densities. ITT do not yield samples of resting, fed mosquitoes for blood meal analysis.MethodsOutdoors mosquito sampling methods, namely human landing catch (HLC), ITT (Design B) and resting boxes (RB) were conducted in parallel with indoors sampling using HLC, Centers for Disease Control and Prevention miniature light traps (LT) and RB as well as window exit traps (WET) in urban Dar es Salaam, rotating them thirteen times through a 3 × 3 Latin Square experimental design replicated in four blocks of three houses. This study was conducted between 6th May and 2rd July 2008, during the main rainy season when mosquito biting densities reach their annual peak.ResultsThe mean sensitivities of indoor RB, outdoor RB, WET, LT, ITT (Design B) and HLC placed outdoor relative to HLC placed indoor were 0.01, 0.005, 0.036, 0.052, 0.374, and 1.294 for Anopheles gambiae sensu lato (96% An. gambiae s.s and 4% An. arabiensis), respectively, and 0.017, 0.053, 0.125, 0.423, 0.372 and 1.140 for Culex spp, respectively. The ITT (Design B) catches correlated slightly better to indoor HLC (r2 = 0.619, P < 0.001, r2 = 0.231, P = 0.001) than outdoor HLC (r2 = 0.423, P < 0.001, r2 = 0.228, P = 0.001) for An. gambiae s.l. and Culex spp respectively but the taxonomic composition of mosquitoes caught by ITT does not match those of the indoor HLC (χ2 = 607.408, degrees of freedom = 18, P < 0.001). The proportion of An. gambiae caught indoors was unaffected by the use of an LLIN in that house.ConclusionThe RB, WET and LT are poor methods for surveillance of malaria vector densities in urban Dar es Salaam compared to ITT and HLC but there is still uncertainty over whether the ITT best reflects indoor or outdoor biting densities. The particular LLIN evaluated here failed to significantly reduce house entry by An. gambiae s.l. suggesting a negligible repellence effect.

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Entomological Evaluation of Malaria Vectors at Different Altitudes in Hai District, Northeastern Tanzania

Cited by 30 publications

References 30 publications

Impact of housing condition on indoor-biting and indoor-resting Anopheles arabiensis density in a highland area, central Ethiopia

Impact of housing condition on indoor-biting and indoor-resting Anopheles arabiensis density in a highland area, central Ethiopia

Bionomics of Anopheline species and malaria transmission dynamics along an altitudinal transect in Western Cameroon

Monitoring mosquitoes in urban Dar es Salaam: Evaluation of resting boxes, window exit traps, CDC light traps, Ifakara tent traps and human landing catches

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