Reconsideration of Anopheles rivulorum as a vector of Plasmodium falciparum in western Kenya: some evidence from biting time, blood preference, sporozoite positive rate, and pyrethroid resistance

Kawada, Hiroyuki; Dida, Gabriel O.; Sonye, George; Njenga, Sammy M.; Mwandawiro, Charles; Minakawa, Noboru

doi:10.1186/1756-3305-5-230

Cited by 54 publications

(61 citation statements)

References 28 publications

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“…arabiensis from the study area was documented with the WHO tube bioassays, where mortality was less than 90%. Recent publications also report growing pyrethroid resistance in a number of the malaria vector species in the study area [35, 47, 48]. This might have also contributed to the limited effect of the field intervention.…”

Section: Discussionmentioning

confidence: 92%

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Exploring the potential of using cattle for malaria vector surveillance and control: a pilot study in western Kenya

et al. 2017

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BackgroundMalaria vector mosquitoes with exophilic and zoophilic tendencies, or with a high acceptance of alternative blood meal sources when preferred human blood-hosts are unavailable, may help maintain low but constant malaria transmission in areas where indoor vector control has been scaled up. This residual transmission might be addressed by targeting vectors outside the house. Here we investigated the potential of insecticide-treated cattle, as routinely used for control of tsetse and ticks in East Africa, for mosquito control.MethodsThe malaria vector population in the study area was investigated weekly for 8 months using two different trapping tools: light traps indoors and cattle-baited traps (CBTs) outdoors. The effect of the application of the insecticide deltamethrin and the acaricide amitraz on cattle on host-seeking Anopheles arabiensis was tested experimentally in field-cages and the impact of deltamethrin-treated cattle explored under field conditions on mosquito densities on household level.ResultsCBTs collected on average 2.8 (95% CI: 1.8–4.2) primary [Anopheles gambiae (s.s.), An. arabiensis and An. funestus (s.s.)] and 6.3 (95% CI: 3.6–11.3) secondary malaria vectors [An. ivulorum and An. coustani (s.l.)] per trap night and revealed a distinct, complementary seasonality. At the same time on average only 1.4 (95% CI: 0.8–2.3) primary and 1.1 (95% CI: 0.6–2.0) secondary malaria vectors were collected per trap night with light traps indoors. Amitraz had no effect on survival of host-seeking An. arabiensis under experimental conditions but deltamethrin increased mosquito mortality (OR 19, 95% CI: 7–50), but only for 1 week. In the field, vector mortality in association with deltamethrin treatment was detected only with CBTs and only immediately after the treatment (OR 0.25, 95% CI: 0.13–0.52).ConclusionsEntomological sampling with CBTs highlights that targeting cattle for mosquito control has potential since it would not only target naturally zoophilic malaria vectors but also opportunistic feeders that lack access to human hosts as is expected in residual malaria transmission settings. However, the deltamethrin formulation tested here although used widely to treat cattle for tsetse and tick control, is not suitable for the control of malaria vectors since it causes only moderate initial mortality and has little residual activity.

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Section: Discussionmentioning

confidence: 92%

“…arabiensis , a more exophilic vector, has increased. Furthermore, secondary vectors have been suggested to be playing an increasingly important role in malaria transmission [35]. The objectives of this study were three fold: (i) To determine the knockdown and mortality of An.…”

Section: Introductionmentioning

confidence: 99%

Exploring the potential of using cattle for malaria vector surveillance and control: a pilot study in western Kenya

et al. 2017

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“…Therefore, the extensive use of ITNs and LLINs in the study area is thought to be a major factor causing high pyrethroid resistance [21, 28]. …”

Section: Discussionmentioning

confidence: 99%

Preventive effect of permethrin-impregnated long-lasting insecticidal nets on the blood feeding of three major pyrethroid-resistant malaria vectors in western Kenya

et al. 2014

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BackgroundSince the World Health Organization (WHO) adopted the use of long-lasting insecticidal nets (LLINs) as a principal strategy for effective malaria prevention and control, pyrethroids have been the only class of insecticides used for LLINs. The dramatic success of insecticide-treated nets (ITNs) and LLINs in African countries, however, has been threatened by the rapid development of pyrethroid resistance in vector mosquitoes. ITNs and LLINs are still used as effective self-protection measures, but there have been few studies on the effectiveness of ITNs and LLINs in areas where vector mosquitoes are pyrethroid-resistant.MethodsTo investigate the behavioral pattern of mosquitoes in the houses where LLINs were used, indoor mosquito trappings of Anopheles gambiae s.s., An. arabiensis, and An. funestus s.s. were performed with Centers for Disease Control and Prevention (CDC) miniature light trap equipped with a collection bottle rotator at 2-hour intervals between 4:00 pm and 8:00 am. The trapped female mosquitoes were identified and classified as unfed, blood fed, and gravid. The abdominal contents of fed female mosquitoes were used for DNA extractions to identify the blood source.ResultsA large proportion of human blood feeding of An. arabiensis and An. funestus s.s. (but not An. gambiae s.s.) took place during the time people were active outside LLINs. However, during the hours when people were beneath LLINs, these provided protective efficacy as indicated by reduced human blood feeding rates.ConclusionLLINs provided effective protection against pyrethroid-resistant malaria vector populations during bedtime hours. However, protection of LLINs was insufficient during the hours when people were active outside of the bed nets. Such limitation of LLINs will need to be intensively addressed in African countries in the near future.

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“…The specific behaviors of Anopheles species A, one of the most abundant species in our study sites with a P. falciparum infection rate comparable to that previously published for An. funestus in western Kenya, 58,59 are currently being characterized. This study emphasizes the importance of combining molecular tools with morphological identifications, particularly in areas with diverse species.…”

Section: Discussionmentioning

confidence: 99%

Molecular Characterization Reveals Diverse and Unknown Malaria Vectors in the Western Kenyan Highlands

Laurent¹,

Cooke²,

Krishnankutty³

et al. 2016

The American Society of Tropical Medicine and Hygiene

120

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Abstract. The success of mosquito-based malaria control is dependent upon susceptible bionomic traits in local malaria vectors. It is crucial to have accurate and reliable methods to determine mosquito species composition in areas subject to malaria. An unexpectedly diverse set of Anopheles species was collected in the western Kenyan highlands, including unidentified and potentially new species carrying the malaria parasite Plasmodium falciparum. This study identified 2,340 anopheline specimens using both ribosomal DNA internal transcribed spacer region 2 and mitochondrial DNA cytochrome oxidase subunit 1 loci. Seventeen distinct sequence groups were identified. Of these, only eight could be molecularly identified through comparison to published and voucher sequences. Of the unidentified species, four were found to carry P. falciparum by circumsporozoite enzyme-linked immunosorbent assay and polymerase chain reaction, the most abundant of which had infection rates comparable to a primary vector in the area, Anopheles funestus. High-quality adult specimens of these unidentified species could not be matched to museum voucher specimens or conclusively identified using multiple keys, suggesting that they may have not been previously described. These unidentified vectors were captured outdoors. Diverse and unknown species have been incriminated in malaria transmission in the western Kenya highlands using molecular identification of unusual morphological variants of field specimens. This study demonstrates the value of using molecular methods to compliment vector identifications and highlights the need for accurate characterization of mosquito species and their associated behaviors for effective malaria control.

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Reconsideration of Anopheles rivulorum as a vector of Plasmodium falciparum in western Kenya: some evidence from biting time, blood preference, sporozoite positive rate, and pyrethroid resistance

Cited by 54 publications

References 28 publications

Exploring the potential of using cattle for malaria vector surveillance and control: a pilot study in western Kenya

Exploring the potential of using cattle for malaria vector surveillance and control: a pilot study in western Kenya

Preventive effect of permethrin-impregnated long-lasting insecticidal nets on the blood feeding of three major pyrethroid-resistant malaria vectors in western Kenya

Molecular Characterization Reveals Diverse and Unknown Malaria Vectors in the Western Kenyan Highlands

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