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The effect of aliphatic carboxylic acids on olfaction-based host-seeking of the malaria mosquito Anopheles gambiae sensu stricto.

ABSTRACT: The role of aliphatic carboxylic acids in host-seeking response of the malaria mosquito Anopheles gambiae sensu stricto was examined both in a dual-choice olfactometer and with indoor traps. A basic attractive blend of ammonia + lactic acid served as internal standard odor. Single carboxylic acids were tested in a tripartite blend with ammonia + lactic acid. Four different airflow stream rates (0.5, 5, 50, and 100 ml/min) carrying the compounds were tested for their effect on trap entry response in the olfactometer. In the olfactometer, propanoic acid, butanoic acid, 3-methylbutanoic acid, pentanoic acid, heptanoic acid, octanoic acid, and tetradecanoic acid increased attraction relative to the basic blend. While several carboxylic acids were attractive only at one or two flow rates, tetradecanoic acid was attractive at all flow rates tested. Heptanoic acid was attractive at the lowest flow rate (0.5 ml/min), but repellent at 5 and 50 ml/min. Mixing the air stream laden with these 7 carboxylic acids together with the headspace of the basic blend increased attraction in two quantitative compositions. Subtraction of single acids from the most attractive blend revealed that 3-methylbutanoic acid had a negative effect on trap entry response. In the absence of tetradecanoic acid, the blend was repellent. In assays with MM-X traps, both a blend of 7 carboxylic acids + ammonia + lactic acid (all applied from low density polyethylene-sachets) and a simple blend of ammonia + lactic acid + tetradecanoic acid were attractive. The results show that carboxylic acids play an essential role in the host-seeking behavior of An. gambiae, and that the contribution to blend attractiveness depends on the specific compound studied.

SUBMITTER: Smallegange RC

PROVIDER: S-EPMC2746306 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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The effect of aliphatic carboxylic acids on olfaction-based host-seeking of the malaria mosquito Anopheles gambiae sensu stricto.

Smallegange Renate C RC Qiu Yu Tong YT Bukovinszkiné-Kiss Gabriella G Van Loon Joop J A JJ Takken Willem W

Journal of chemical ecology 20090723 8

The role of aliphatic carboxylic acids in host-seeking response of the malaria mosquito Anopheles gambiae sensu stricto was examined both in a dual-choice olfactometer and with indoor traps. A basic attractive blend of ammonia + lactic acid served as internal standard odor. Single carboxylic acids were tested in a tripartite blend with ammonia + lactic acid. Four different airflow stream rates (0.5, 5, 50, and 100 ml/min) carrying the compounds were tested for their effect on trap entry response ...[more]

PMID: 19626371

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Project description:BackgroundInsect growth regulators (IGRs) can control insect vector populations by disrupting growth and development in juvenile stages of the vectors. We previously identified and described the curry tree (Murraya koenigii (L.) Spreng) phytochemical leaf extract composition (neplanocin A, 3-(1-naphthyl)-L-alanine, lumiflavine, terezine C, agelaspongin and murrayazolinol), which disrupted growth and development in Anopheles gambiae sensu stricto mosquito larvae by inducing morphogenetic abnormalities, reducing locomotion and delaying pupation in the mosquito. Here, we attempted to establish the transcriptional process in the larvae that underpins these phenotypes in the mosquito.MethodsWe first exposed third-fourth instar larvae of the mosquito to the leaf extract and consequently the inherent phytochemicals (and corresponding non-exposed controls) in two independent biological replicates. We collected the larvae for our experiments sampled 24 h before peak pupation, which was 7 and 18 days post-exposure for controls and exposed larvae, respectively. The differences in duration to peak pupation were due to extract-induced growth delay in the larvae. The two study groups (exposed vs control) were consequently not age-matched. We then sequentially (i) isolated RNA (whole larvae) from each replicate treatment, (ii) sequenced the RNA on Illumina HiSeq platform, (iii) performed differential bioinformatics analyses between libraries (exposed vs control) and (iv) independently validated the transcriptome expression profiles through RT-qPCR.ResultsOur analyses revealed significant induction of transcripts predominantly associated with hard cuticular proteins, juvenile hormone esterases, immunity and detoxification in the larvae samples exposed to the extract relative to the non-exposed control samples. Our analysis also revealed alteration of pathways functionally associated with putrescine metabolism and structural constituents of the cuticle in the extract-exposed larvae relative to the non-exposed control, putatively linked to the exoskeleton and immune response in the larvae. The extract-exposed larvae also appeared to have suppressed pathways functionally associated with molting, cell division and growth in the larvae. However, given the age mismatch between the extract-exposed and non-exposed larvae, we can attribute the modulation of innate immune, detoxification, cuticular and associated transcripts and pathways we observed to effects of age differences among the larvae samples (exposed vs control) and to exposures of the larvae to the extract.ConclusionsThe exposure treatment appears to disrupt cuticular development, immune response and oxidative stress pathways in Anopheles gambiae s.s larvae. These pathways can potentially be targeted in development of more efficacious curry tree phytochemical-based IGRs against An. gambiae s.s mosquito larvae.

Project description:BackgroundThe demonstration that the recently discovered Anopheles symbiont Microsporidia MB blocks malaria transmission in Anopheles arabiensis and undergoes vertical and horizontal transmission suggests that it is a promising candidate for the development of a symbiont-based malaria transmission-blocking strategy. The infection prevalence and characteristics of Microsporidia MB in Anopheles gambiae sensu stricto (s.s.), another primary vector species of malaria in Kenya, were investigated.MethodsField-collected females were confirmed to be Microsporidia MB-positive after oviposition. Egg counts of Microsporidia MB-infected and non-infected individuals were used to infer the effects of Microsporidia MB on fecundity. The time to pupation, adult sex ratio and survival were used to determine if Microsporidia MB infection has similar characteristics in the host mosquitoes An. gambiae and An. arabiensis. The intensity of Microsporidia MB infection in tissues of the midgut and gonads, and in carcasses, was determined by quantitative polymerase chain reaction. To investigate horizontal transmission, virgin males and females that were either Microsporidia MB-infected or non-infected were placed in standard cages for 48 h and allowed to mate; transmission was confirmed by quantitative polymerase chain reaction targeting Microsporidia MB genes.ResultsMicrosporidia MB was found to naturally occur at a low prevalence in An. gambiae s.s. collected in western Kenya. Microsporidia MB shortened the development time from larva to pupa, but other fitness parameters such as fecundity, sex ratio, and adult survival did not differ between Microsporidia MB-infected and non-infected hosts. Microsporidia MB intensities were high in the male gonadal tissues. Transmission experiments indicated that Microsporidia MB undergoes both maternal and horizontal transmission in An. gambiae s.s.ConclusionsThe findings that Microsporidia MB naturally infects, undergoes maternal and horizontal transmission, and is avirulent in An. gambiae s.s. indicate that many of the characteristics of its infection in An. arabiensis hold true for the former. The results of the present study indicate that Microsporidia MB could be developed as a tool for the transmission-blocking of malaria across different Anopheles species.

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Project description:BackgroundUnderstanding the ecology and behaviour of disease vectors, including the olfactory cues used to orient and select hosts and egg-laying sites, are essential for the development of novel, insecticide-free control tools. Selected graminoid plants have been shown to release volatile chemicals attracting malaria vectors; however, whether the attraction is selective to individual plants or more general across genera and families is still unclear.MethodsTo contribute to the current evidence, we implemented bioassays in two-port airflow olfactometers and in large field cages with four live graminoid plant species commonly found associated with malaria vector breeding sites in western Kenya: Cyperus rotundus and C. exaltatus of the Cyperaceae family, and Panicum repens and Cynodon dactylon of the Poaceae family. Additionally, we tested one Poaceae species, Cenchrus setaceus, not usually associated with water. The volatile compounds released in the headspace of the plants were identified using gas chromatography/mass spectrometry.ResultsAll five plants attracted gravid vectors, with the odds of a mosquito orienting towards the choice-chamber with the plant in an olfactometer being 2-5 times higher than when no plant was present. This attraction was maintained when tested with free-flying mosquitoes over a longer distance in large field cages, though at lower strength, with the odds of attracting a female 1.5-2.5 times higher when live plants were present than when only water was present in the trap. Cyperus rotundus, previously implicated in connection with an oviposition attractant, consistently elicited the strongest response from gravid vectors. Volatiles regularly detected were limonene, β-pinene, β-elemene and β-caryophyllene, among other common plant compounds previously described in association with odour-orientation of gravid and unfed malaria vectors.ConclusionsThe present study confirms that gravid Anopheles gambiae sensu stricto use chemical cues released from graminoid plants to orientate. These cues are released from a variety of graminoid plant species in both the Cyperaceae and Poaceae family. Given the general nature of these cues, it appears unlikely that they are exclusively used for the location of suitable oviposition sites. The utilization of these chemical cues for attract-and-kill trapping strategies must be explored under natural conditions to investigate their efficiency when in competition with complex interacting natural cues.

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The effect of aliphatic carboxylic acids on olfaction-based host-seeking of the malaria mosquito Anopheles gambiae sensu stricto.

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The effect of aliphatic carboxylic acids on olfaction-based host-seeking of the malaria mosquito Anopheles gambiae sensu stricto.

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