Persistently high proportions of plasmodium-infected Anopheles funestus mosquitoes in two villages in the Kilombero valley, South-Eastern Tanzania

Mapua, Salum A.; Hape, Emmanuel E.; Kihonda, Japhet; Bwanary, Hamis; Kifungo, Khamis; Kilalangongono, Masoud; Kaindoa, Emmanuel W.; Ngowo, Halfan S.; Okumu, Fredros O.

doi:10.1016/j.parepi.2022.e00264

Cited by 35 publications

(46 citation statements)

References 50 publications

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“…This high implication of An. funestus s.l mosquitoes in malaria transmission corroborates with results obtained recently in Tanzania by Mapua et al [31] and Kaindoa et al [56] where An. funestus contributed for 97.7 and 86.26% of all malaria transmission respectively.…”

Section: An Funestus Sustains a Very High Entomological Inoculation R...supporting

confidence: 92%

“…funestus s.l mosquitoes. This infection rate was similar to some reports across Cameroon in the same mosquito species by Nkemngo et al [27], Ndo et al [52], Mieguim et al [53] and was higher than recent reports across Africa by Osse et al [35] in Benin, Mapua et al [31] in Tanzania, Wolie et al [54] in Côte D'Ivoire and Bamou et al [49] in Kenya and in Ethiopia. The variations between these rates could be attributed to the differences in the detection methods used (TaqMan, ELISA and Nested-PCR).…”

Section: An Funestus Sustains a Very High Entomological Inoculation R...supporting

confidence: 90%

“…High abundance of An. funestus s.l was reported in other locations in Cameroon [17,27,29], in Kenya [30], Tanzania [31] and could be linked to the presence of permanent large pools of water in both sites known to be their favourite breeding site. The high predominance of An.…”

Section: Discussionmentioning

confidence: 66%

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Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

F.,

Tchouakui,

Menze

et al. 2023

Preprint

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Background The impact of metabolic resistance to insecticide on malaria transmission remains poorly characterised notably through application of entomological parameters. The lack of resistance markers has been one of the limiting factors preventing robust assessment of such impact. To this end, the present study sought to investigate how L119F-Gste2 metabolic gene influences entomological parameters underpinning mosquitos’ propensity to transmit Plasmodium species. Methods Longitudinal studies were carried out in Mibellon and Elende, two different eco-climatic settings in Cameroon and mosquitoes were collected using Human Landing Catch (HLC), Centre for Disease Control Light Trap (CDC-LT) and Pyrethrum Spray Catch (PSC) technics. Plasmodium sporozoite parasites were detected by TaqMan and Nested PCR, and blood meal origin with ELISA. The allele-specific PCR (AS-PCR) method was used to genotype the L119F-GSTe2 marker and association with malaria transmission was established by comparing key transmission parameters such as the Entomologic Inoculation Rate (EIR) between individuals with different L119F-GSTe2 genotypes. Results An. funestus s.l was the predominant malaria vector collected during the entomological survey in both sites (86.6% and 96.4% in Elende and Mibellon respectively) followed by An. gambiae s.l (7.5% and 2.4%). Sporozoite infection rates were very high in both collection sites (8.7% and 11% respectively in Elende and Mibellon). An. funestus s.s exhibited a very high entomological inoculation rate (EIR) (66 ib/h/month and 792 ib/h/year) and was responsible for 98.6% of all malaria transmission events occurring in both sites. Human Blood Index was also high in both locations (HBI = 94%). An. funestus s.s. mosquitoes with both 119F/F (RR) and L119F (RS) genotypes had a significantly higher transmission intensity than their susceptible L/L119 (SS) counterparts (IRR = 2.2, 95%CI (1.1–5.2), p = 0.03; IRR = 2.5, 95% CI (1.2–5.8), p = 0.01 respectively). Conclusion This study highlights the major role that An. funestus s.s plays in malaria transmission in Cameroon with an aggravation from GSTe2-based metabolic resistance.

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Section: An Funestus Sustains a Very High Entomological Inoculation R...supporting

confidence: 92%

Section: An Funestus Sustains a Very High Entomological Inoculation R...supporting

confidence: 90%

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Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

F.,

Tchouakui,

Menze

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…arabiensis and Anopheles funestus sensu stricto both of which are resistant to pyrethroids [ 29 , 30 ]. Anopheles funestus mediates most of the transmission [ 31 – 33 ]. ITNs are the main vector control tool in the region, and are mass distributed by the Government [ 34 ].…”

Section: Methodsmentioning

confidence: 99%

CDC light traps underestimate the protective efficacy of an indoor spatial repellent against bites from wild Anopheles arabiensis mosquitoes in Tanzania

Swai

Kibondo

Ntabaliba

et al. 2023

Malar J

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Background Methods for evaluating efficacy of core malaria interventions in experimental and operational settings are well established but gaps exist for spatial repellents (SR). The objective of this study was to compare three different techniques: (1) collection of blood-fed mosquitoes (feeding), (2) human landing catch (HLC), and (3) CDC light trap (CDC-LT) collections for measuring the indoor protective efficacy (PE) of the volatile pyrethroid SR product Mosquito Shield™ Methods The PE of Mosquito Shield™ against a wild population of pyrethroid-resistant Anopheles arabiensis mosquitoes was determined via feeding, HLC, or CDC-LT using four simultaneous 3 by 3 Latin squares (LS) run using 12 experimental huts in Tanzania. On any given night each technique was assigned to two huts with control and two huts with treatment. The LS were run twice over 18 nights to give a sample size of 72 replicates for each technique. Data were analysed by negative binomial regression. Results The PE of Mosquito Shield™ measured as feeding inhibition was 84% (95% confidence interval (CI) 58–94% [Incidence Rate Ratio (IRR) 0.16 (0.06–0.42), p < 0.001]; landing inhibition 77% [64–86%, (IRR 0.23 (0.14–0.36) p < 0.001]; and reduction in numbers collected by CDC-LT 30% (0–56%) [IRR 0.70 (0.44–1.0) p = 0.160]. Analysis of the agreement of the PE measured by each technique relative to HLC indicated no statistical difference in PE measured by feeding inhibition and landing inhibition [IRR 0.73 (0.25–2.12) p = 0.568], but a significant difference in PE measured by CDC-LT and landing inhibition [IRR 3.13 (1.57–6.26) p = 0.001]. Conclusion HLC gave a similar estimate of PE of Mosquito Shield™ against An. arabiensis mosquitoes when compared to measuring blood-feeding directly, while CDC-LT underestimated PE relative to the other techniques. The results of this study indicate that CDC-LT could not effectively estimate PE of the indoor spatial repellent in this setting. It is critical to first evaluate the use of CDC-LT (and other tools) in local settings prior to their use in entomological studies when evaluating the impact of indoor SR to ensure that they reflect the true PE of the intervention.

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“…In these areas, the dominant vector species is An. funestus , which mediates over 80% of all malaria transmission events [ 25 , 26 ]. In particular, there has not been any detailed analysis that integrates observations of the environmental factors (e.g.…”

Section: Introductionmentioning

confidence: 99%

Relationships between biological age, distance from aquatic habitats and pyrethroid resistance status of Anopheles funestus mosquitoes in south-eastern Tanzania

Pinda

Msaky

Muyaga

et al. 2022

Malar J

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Background Malaria transmission can be highly heterogeneous between and within localities, and is influenced by factors such as survival and biting frequencies of Anopheles mosquitoes. This study investigated the relationships between the biological age, distance from aquatic habitats and pyrethroid resistance status of Anopheles funestus mosquitoes, which currently dominate malaria transmission in south-east Tanzania. The study also examined how such relationships may influence malaria transmission and control. Methods Female An. funestus were collected in houses located 50–100 m, 150–200 m or over 200 m from the nearest known aquatic habitats. The mosquitoes were exposed to 1×, 5× and 10× the diagnostic doses of deltamethrin or permethrin, or to the synergist, piperonyl butoxide (PBO) followed by the pyrethroids, then monitored for 24 h-mortality. Ovaries of exposed and non-exposed mosquitoes were dissected to assess parity as a proxy for biological age. Adults emerging from larval collections in the same villages were tested against the same insecticides at 3–5, 8–11 or 17–20 days old. Findings Mosquitoes collected nearest to the aquatic habitats (50-100 m) had the lowest mortalities compared to other distances, with a maximum of 51% mortality at 10× permethrin. For the age-synchronized mosquitoes collected as larvae, the insecticide-induced mortality assessed at both the diagnostic and multiplicative doses (1×, 5× and 10×) increased with mosquito age. The highest mortalities at 1× doses were observed among the oldest mosquitoes (17–20 days). At 10× doses, mortalities were 99% (permethrin) and 76% (deltamethrin) among 8–11 day-olds compared to 80% (permethrin) and 58% (deltamethrin) among 3–5 day-olds. Pre-exposure to PBO increased the potency of both pyrethroids. The proportion of parous females was highest among mosquitoes collected farthest from the habitats. Conclusion In this specific setting, older An. funestus and those collected farthest from the aquatic habitats (near the centre of the village) were more susceptible to pyrethroids than the younger ones and those caught nearest to the habitats. These findings suggest that pyrethroid-based interventions may remain at least moderately effective despite widespread pyrethroid-resistance, by killing the older, less-resistant and potentially-infective mosquitoes. Further studies should investigate how and whether these observations could be exploited to optimize malaria control in different settings.

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Persistently high proportions of plasmodium-infected Anopheles funestus mosquitoes in two villages in the Kilombero valley, South-Eastern Tanzania

Cited by 35 publications

References 50 publications

Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

CDC light traps underestimate the protective efficacy of an indoor spatial repellent against bites from wild Anopheles arabiensis mosquitoes in Tanzania

Relationships between biological age, distance from aquatic habitats and pyrethroid resistance status of Anopheles funestus mosquitoes in south-eastern Tanzania

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