Malaria transmission after five years of vector control on Bioko Island, Equatorial Guinea

Overgaard, Hans J.; Reddy, Vamsi P; Abaga, Simón; Matías, Abrahán; Reddy, M. Rami; Kulkarni, Vani S.; Schwabe, Christopher; Segura, Luís; Kleinschmidt, Immo; Slotman, Michel A.

doi:10.1186/1756-3305-5-253

Cited by 65 publications

(76 citation statements)

References 31 publications

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“…This finding is consistent with the absence of ace-1 R in samples from Equatorial Guinea analyzed by Ridl and others, 12 and the absence of the allele on Bioko Island, where carbamates have been used as part of an ongoing IRS campaign since 2005. 58 The level of resistance provided by ace-1 R to various carabamate insecticides is high and therefore has the potential to greatly undermine IRS efficacy. 59 In addition, a duplicated allele, ace-1 D was recently identified and found to reach frequencies 65% in Cô te d'Ivoire and Burkina Faso, and is likely present in Benin.…”

Section: Discussionmentioning

confidence: 99%

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

Reddy¹,

Godoy²,

Dion³

et al. 2013

The American Society of Tropical Medicine and Hygiene

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Section: Discussionmentioning

confidence: 99%

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

Reddy¹,

Godoy²,

Dion³

et al. 2013

The American Society of Tropical Medicine and Hygiene

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“…The use of these methods is substantially increasing in endemic countries [5] in the framework of malaria elimination programmes [6]. Evidence of malaria burden reduction through full coverage of LLINs or coupled with IRS are reported in some African countries [7-9]. …”

Section: Introductionmentioning

confidence: 99%

Multiple insecticide resistance mechanisms in Anopheles gambiae s.l. populations from Cameroon, Central Africa

et al. 2013

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BackgroundIncreasing incidence of DDT and pyrethroid resistance in Anopheles mosquitoes is seen as a limiting factor for malaria vector control. The current study aimed at an in-depth characterization of An. gambiae s.l. resistance to insecticides in Cameroon, in order to guide malaria vector control interventions.MethodsAnopheles gambiae s.l. mosquitoes were collected as larvae and pupae from six localities spread throughout the four main biogeographical domains of Cameroon and reared to adults in insectaries. Standard WHO insecticide susceptibility tests were carried out with 4% DDT, 0.75% permethrin and 0.05% deltamethrin. Mortality rates and knockdown times (kdt50 and kdt95) were determined and the effect of pre-exposure to the synergists DEF, DEM and PBO was assessed. Tested mosquitoes were identified to species and molecular forms (M or S) using PCR-RFLP. The hot ligation method was used to depict kdr mutations and biochemical assays were conducted to assess detoxifying enzyme activities.ResultsThe An. arabiensis population from Pitoa was fully susceptible to DDT and permethrin (mortality rates > 98%) and showed reduced susceptibility to deltamethrin. Resistance to DDT was widespread in An. gambiae s.s. populations and heterogeneous levels of susceptibility to permethrin and deltamethrin were observed. In many cases, prior exposure to synergists partially restored insecticide knockdown effect and increased mortality rates, suggesting a role of detoxifying enzymes in increasing mosquito survival upon challenge by pyrethroids and, to a lower extent DDT. The distribution of kdr alleles suggested a major role of kdr-based resistance in the S form of An. gambiae. In biochemical tests, all but one mosquito population overexpressed P450 activity, whereas baseline GST activity was low and similar in all field mosquito populations and in the control.ConclusionIn Cameroon, multiple resistance mechanisms segregate in the S form of An. gambiae resulting in heterogeneous resistance profiles, whereas in the M form and An. arabiensis insecticide tolerance seems to be essentially mediated by enzyme-based detoxification. Synergists partially restored susceptibility to pyrethroid insecticides, and might help mitigate the impact of vector resistance in the field. However, additional vector control tools are needed to further impact on malaria transmission in such settings.

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“…melas feeds readily on humans, both indoors and outdoors [5], and together with An. gambiae s.s. is responsible for malaria transmission [6], [7]. Besides the Anopheles gambiae complex, various other species contribute to transmission as well, and in the equatorial rainforests of Central Africa the anthropophilic and endophilic Anopheles moucheti is an important vector [4].…”

Section: Introductionmentioning

confidence: 99%

The Effective Population Size of Malaria Mosquitoes: Large Impact of Vector Control

et al. 2012

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Malaria vectors in sub-Saharan Africa have proven themselves very difficult adversaries in the global struggle against malaria. Decades of anti-vector interventions have yielded mixed results—with successful reductions in transmission in some areas and limited impacts in others. These varying successes can be ascribed to a lack of universally effective vector control tools, as well as the development of insecticide resistance in mosquito populations. Understanding the impact of vector control on mosquito populations is crucial for planning new interventions and evaluating existing ones. However, estimates of population size changes in response to control efforts are often inaccurate because of limitations and biases in collection methods. Attempts to evaluate the impact of vector control on mosquito effective population size (Ne) have produced inconclusive results thus far. Therefore, we obtained data for 13–15 microsatellite markers for more than 1,500 mosquitoes representing multiple time points for seven populations of three important vector species—Anopheles gambiae, An. melas, and An. moucheti—in Equatorial Guinea. These populations were exposed to indoor residual spraying or long-lasting insecticidal nets in recent years. For comparison, we also analyzed data from two populations that have no history of organized vector control. We used Approximate Bayesian Computation to reconstruct their demographic history, allowing us to evaluate the impact of these interventions on the effective population size. In six of the seven study populations, vector control had a dramatic impact on the effective population size, reducing Ne between 55%–87%, the exception being a single An. melas population. In contrast, the two negative control populations did not experience a reduction in effective population size. This study is the first to conclusively link anti-vector intervention programs in Africa to sharply reduced effective population sizes of malaria vectors.

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Malaria transmission after five years of vector control on Bioko Island, Equatorial Guinea

Cited by 65 publications

References 31 publications

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

Multiple insecticide resistance mechanisms in Anopheles gambiae s.l. populations from Cameroon, Central Africa

The Effective Population Size of Malaria Mosquitoes: Large Impact of Vector Control

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