Increased Threat of Urban Malaria from <i>Anopheles stephensi</i> Mosquitoes, Africa

The use of semiochemicals in odour-based traps for surveillance and control of vector mosquitoes is deemed a new and viable component for integrated vector management programmes. Over 114 semiochemicals have been identified, yet implementation of these for management of infectious diseases such as malaria, dengue, chikungunya and Rift Valley fever is still a major challenge. The difficulties arise due to variation in how different mosquito species respond to not only single chemical compounds but also complex chemical blends. Additionally, mosquitoes respond to different volatile blends when they are looking for a mating partner, oviposition sites or a meal. Analytically the challenge lies not only in correctly identifying these semiochemical signals and cues but also in developing formulations that effectively mimic blend ratios that different mosquito species respond to. Only then can the formulations be used to enhance the selectivity and efficacy of odour-based traps. Understanding how mosquitoes use semiochemical cues and signals to survive may be key to unravelling these complex interactions. An overview of the current studies of these chemical messages and the chemical ecology involved in complex behavioural patterns is given. This includes an updated list of the semiochemicals which can be used for integrated vector control management programmes. A thorough understanding of these semiochemical cues is of importance for the development of new vector control methods that can be integrated into established control strategies.

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“…coluzzii and An. funestus being the predominant malaria vector species [4]. However, some minor species are also cause for concern.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the Asian native mosquito An. stephensi is now established in Ethiopia [4] and An. arabiensis is deemed a major cause of residual malaria transmission due to the species' insecticide avoidance behaviours [2].…”

Section: Introductionmentioning

confidence: 99%

Controlling mosquitoes with semiochemicals: a review

et al. 2020

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“…Many important mosquito species contribute to parasite transmission, increasing the complexity of both surveillance and control efforts. Our focus is Anopheles stephensi, the Indian malaria mosquito, an aggressive malaria vector mosquito that has invaded and become established in Sri Lanka, Djibouti, and Ethiopia, with significant risk for range expansion into Somalia, Eritrea and Sudan (Faulde et al, 2014;Surendran et al, 2018;Seyfarth et al, 2019;Takken and Lindsay, 2019). In Djibouti, A. stephensi has been linked to a resurgence of severe infection with the human malaria parasite Plasmodium falciparum (Seyfarth et al, 2019), so increased focus on this species is relevant and timely for control.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive and Durable Modulation of Growth, Development, Lifespan and Fecundity in Anopheles stephensi Following Larval Treatment With the Stress Signaling Molecule and Novel Antimalarial Abscisic Acid

et al. 2020

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The larval environment of holometabolous insects determines many adult life history traits including, but not limited to, rate and success of development and adult lifespan and fecundity. The ancient stress signaling hormone abscisic acid (ABA), released by plants inundated with water and by leaf and root fragments in water, is likely ubiquitous in the mosquito larval environment and is well known for its wide ranging effects on invertebrate biology. Accordingly, ABA is a relevant stimulus and signal for mosquito development. In our studies, the addition of ABA at biologically relevant levels to larval rearing containers accelerated the time to pupation and increased death of A. stephensi pupae. We could not attribute these effects, however, to ABA-dependent changes in JH biosynthesis-associated gene expression, 20E titers or transcript patterns of insulin-like peptide genes. Adult females derived from ABA-treated larvae had reduced total protein content and significantly reduced post blood meal transcript expression of vitellogenin, effects that were consistent with variably reduced egg clutch sizes and oviposition success from the first through the third gonotrophic cycles. Adult female A. stephensi derived from ABA-treated larvae also exhibited reduced lifespans relative to controls. Collectively, these effects of ABA on A. stephensi life history traits are robust, durable and predictive of multiple impacts of an important malaria vector spreading to new malaria endemic regions.

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“…The current presence and the possible spread of An. stephensi to African countries poses a potential health risk since it is a malaria vector well adapted to urban centers and it could cause malaria outbreaks of unprecedented sizes (Balkew et al, 2019;Takken and Lindsay, 2019). Our model indicates that the breadth of temperature range for An.…”

Section: Discussionmentioning

confidence: 91%

“…stephensi is a native mosquito of Asia (Sinka et al, 2010), recent research has reported that An. stephensi mosquitoes are already present in Africa, for example in Djibouti (Faulde et al, 2014), Ethiopia (Balkew et al, 2019;Carter et al, 2018), Sudan, and probably in neighboring countries (Takken and Lindsay, 2019;World Health Organization, 2019). The current presence and the possible spread of An.…”

Section: Discussionmentioning

confidence: 99%

Temperature impacts the transmission of malaria parasites byAnopheles gambiaeandAnopheles stephensimosquitoes

Villena

Ryan

Murdock

et al. 2020

Preprint

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Transmission of malaria and other vector-borne diseases (VBDs) is greatly influenced by environmental factors, especially temperature, due to the ectothermic nature of insect and arthropod vectors. However, the response of transmission to temperature and other drivers is complex, as thermal traits of ectotherms are typically non-linear, and they interact to determine transmission constraints. In this study, we assess and compare the effect of temperature on the transmission of two malaria parasites, Plasmodium falciparum and Plasmodium vivax, by two malaria vector species, Anopheles gambiae and Anopheles stephensi. We model the non-linear responses of temperature dependent mosquito and parasite traits (mosquito development rate, bite rate, fecundity, egg to adult survival, vector competence, mortality rate, and parasite development rate) and incorporate these traits into a suitability metric based on a model for the basic reproductive number across temperatures. Our model predicts that the optimum temperature for transmission suitability is similar for the four mosquito-parasite combinations assessed in this study. The main differences are found at the thermal limits. More specifically, we found significant differences in the upper thermal limit between parasites spread by the same mosquito (An. stephensi) and between mosquitoes carrying P. falciparum. In contrast, at the lower thermal limit the significant differences were primarily between the mosquito species that both carried the same pathogen (e.g., An. stephensi and An. gambiae both with P. falciparum). Using prevalence data from Africa and Asia, we show that the transmission suitability metric S(T) calculated from our mechanistic model is an important predictor of malaria prevalence. We mapped risk to illustrate the areas in Africa and Asia that are suitable for malaria transmission year-round based temperature. The wider thermal range of transmission by An. stephensi for both malaria parasites allows for a greater geographic potential for malaria spread. This study could be useful in planing preventive strategies for areas where malaria outbreaks might occur.

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Increased Threat of Urban Malaria from Anopheles stephensi Mosquitoes, Africa

Cited by 86 publications

References 9 publications

Controlling mosquitoes with semiochemicals: a review

Controlling mosquitoes with semiochemicals: a review

Comprehensive and Durable Modulation of Growth, Development, Lifespan and Fecundity in Anopheles stephensi Following Larval Treatment With the Stress Signaling Molecule and Novel Antimalarial Abscisic Acid

Temperature impacts the transmission of malaria parasites byAnopheles gambiaeandAnopheles stephensimosquitoes

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