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Impact of Non-Pyrethroid Insecticide Treated Durable Wall Lining on Age

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Impact of Non-Pyrethroid Insecticide Treated Durable Wall Lining on Age Emidi et al. BMC Res Notes (2017) 10:744 https://doi.org/10.1186/s13104-017-3078-7 BMC Research Notes RESEARCH NOTE Open Access Impact of non‑pyrethroid insecticide treated durable wall lining on age structure of malaria vectors in Muheza, Tanzania Basiliana Emidi1,2*, William N. Kisinza3 and Franklin W. Mosha1 Abstract Objective: Malaria vectors control interventions are designed to cause immediate killing or shorten mosquito lives, therefore does not allow enough time for the development of the parasites to infective stage. The wall lining is new malaria vectors control intervention in Tanzania where its impact on age structure is not well known. Therefore this study aimed at determining the impact of non-pyrethroid durable wall lining on the age structure of malaria vectors. Results: Higher proportions of An. gambiae sensu lato (57.1%, z 2.66, P 0.0077) and An. funestus (64.8%, z 3.38, P 0.001) were collected in the control clusters. Unexpectedly, signifcantly= = higher proportion of parous An. gambiae= s. =l. were collected in the intervention clusters (z 2.78, P 0.0054). The wall lining intervention has demonstrated low impact on age structure of An. gambiae s. l., this= − call for further= studies on the efcacy of the intervention. Keywords: Non-pyrethroid treated durable wall liners, Age structure, Parous, Nulliparous, An. funestus, An. gambiae s. l., Malaria vectors, Muheza, Tanzania Introduction would also be accompanied by feeding more outdoors Mosquito biting behaviour changes have been reported at dusk or dawn rather than indoors at mid-night [4, 7, to be induced by vector control interventions, particu- 8]. Outdoor biting mosquitoes remain as secondary larly when excito-repellent insecticides are used [1]. sources of malaria transmission as they respond poorly to Spraying the walls and ceiling of houses with residual indoors insecticidal interventions [9–11]. insecticides tends to reduce the survival of mosquito vec- Age grading technique is applied for establishing the tors, therefore reduce malaria transmission [2]. Tis is parous rate of mosquito populations in order to esti- because, insecticides irritancy cause high proportion of mate longevity [12]. Normally, mosquitoes are dissected mosquitoes to exit from treated houses. However, treated to observe ovarian dilations in order to determine the walls also contribute to decreased feeding rate and rest- proportions that are nulliparous (have not laid eggs) or ing behaviour of indoor biting mosquitoes [3]. An. gam- young mosquito and parous (have laid eggs) or old mos- biae s. s. and An. funestus, which are the malaria vectors, quitoes [12, 13]. Parous mosquitoes are those that have naturally prefer to feed and rests indoors [3–5]. Tis is taken a blood meal and oviposited at least once [14]. Age in contrast to the strongly exophilic and exophagic; An. grading in malaria vector is important in estimating the arabiensis [6, 7]. Nevertheless, the use of indoor chemical risk of malaria in a particular area [15], with respect to interventions such as long lasting insecticide treated nets the presence of interventions [16]. Currently, a novel (LLINs) and indoor residue spray (IRS) have reported to non-pyrethroid insecticide treated durable wall liner drive malaria vectors to feed and rest outdoors resulting (ITWL) which works similar to IRS has been developed. in a reproductive advantage for them [4]. Such shifting It consists of a thin sheet of cloth made from high-density polypropylene treated with a mixture of two non-pyre- throid insecticides namely; abamectin and fenpyroximate *Correspondence: [email protected] 1 Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania [17, 18]. Te impact of ITWL intervention on age struc- Full list of author information is available at the end of the article ture of malaria vectors is not well known in Tanzania. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Emidi et al. BMC Res Notes (2017) 10:744 Page 2 of 5 Terefore, the present study aimed at determining its durable wall liners installation and they were provided impact on age structure of malaria vectors under feld with LLINs while control clusters were the ones which conditions in the study area. were provided with LLINs alone. Te core area of each cluster had a minimum of 124 households [18]. In each Main text cluster, four houses with open eaves and unscreened Materials and methods windows were selected. In each selected house only one Study area window of the sleeping room was chosen for setting exit Tis cross-sectional study was conducted for the dura- traps as described in the WHO [12] in order to collect tion of 7 months from November, 2015 to May, 2016 in mosquitoes (Figs. 1, 2). 18 clusters in Muheza district, North-eastern coast of Tanzania. In recent years, there have been fuctuations Data analysis in the rainfall patterns with long drought periods in the Data were entered in excel database and transferred to study area. During implementation of this study, there Stata version 13 statistical software where a Two-sample were long dry seasons which accompanied with dryness test for proportions (z) was performed. Te outcomes of of the mosquito breeding sites [19]. Te district covers a interest were the proportions of parous and nulliparous geographical area of 4922 km2, lying between 5°S latitude among the malaria vector species and intervention arms. and 39°E longitude. Te climate is tropical, with dense In all analysis a P value of < 0.05 was considered statisti- rainforest over the Usambara mountain ranges and has cally signifcant. an annual rainfall of 1000–2000 mm. Muheza district is mainly inhabited by subsistence farmers. Adminis- Mosquito identifcation and dissection tratively, Muheza district is divided into six divisions Adult mosquitoes were identifed morphologically using comprised of 35 wards with 175 villages [20]. Te area identifcation keys [25] for Anopheles, Culicines [26] and is endemic for malaria and lymphatic flariasis whereby Zootaxa 700 key was used for Aedes mosquitoes [27]. All An. gambiae s. l. and An. funestus are the main vectors Culicines collected were recorded after identifcation and of these diseases [21, 22]. An. gambiae s. l. in this area then discarded. All fresh unfed An. gambiae s. l. and An. has also been documented to be resistant to pyrethroid funestus were dissected to observe ovarian dilations [12, insecticides [23, 24]. 13]. Based on tracheolar skeins, dissected mosquitoes were categorized as parous and nulliparous [12]. Site selection and mosquito collection A total of 18 clusters were selected; nine in control clus- An. gambiae s. l. and An. funestus sibling species ters and nine in intervention clusters from clusters in a identifcation randomized feld trial [18]. Intervention clusters were An. gambiae s. l. was identifed to sibling species by real- those with high percentage (over 80%) coverage of time polymerase chain reaction (PCR) as described by Fig. 1 Mosquito trapping. a House type. b Exit trap set on the window Emidi et al. BMC Res Notes (2017) 10:744 Page 3 of 5 Fig. 2 Exit trap on a window with ITWL, b collecting mosquitoes in exit trap Bass et al. [28]. An. funestus sibling species were identi- Regarding An. funestus, the proportion of parous was fed by PCR based on species-specifc primers. Electro- higher in the control clusters while that of nulliparous phoresis was performed there after and amplicons were were higher in intervention clusters although not statisti- then visualized under uv-light for scoring DNA band cally signifcant (Table 1). lengths in relation to positive controls as described by Koekemoer et al. [29]. An. gambiae s. l. and An. funestus group sibling species composition and circumsporozoite ELISA positivity Malaria sporozoites determination A total of 302 An. gambiae s. l. and An. funestus group Malaria sporozoites determination in An. gambiae s. mosquitoes were identifed to sibling species. Among l. and An. funestus was done by using enzyme linked- these, An. gambiae s. l. accounted for 60% (n = 181) and immunosorbent assay (ELISA) technique according to An. funestus group were 40% (n = 121). PCR results has Witz et al. [30] whereby mosquito head and thorax were shown that, An. gambiae s. l. consisted of An. gambiae s. used. s. (74%, n = 134) and An. arabiensis (26%, n = 47). Within the An. funestus group, four sibling species were identi- Results fed; these included; An. funestus s. s. (95%, n = 115), An. Mosquito collected leesoni (2.5%, n = 3), An. rivulorum (1.7%, n = 2) and A total of 1757 mosquitoes were collected. Majority of An. parensis (0.8%, n = 1). Te circumsporozoite (CSP) mosquitoes collected were Cx. quinquefasciatus followed ELISA results revealed that, sporozoite positive among by An. gambiae s. l. and An. funestus. Malaria vectors An. gambiae s. s. was 5.6% while that of An. funestus s. s. (An. gambiae s. l. and An. funestus) accounted for 28.5% was 2.0% with two individuals from each of the species. (n = 501). Majority of An. gambiae s. l. (57.1%, n = 205) Te overall CSP positive among An. gambiae s. s and An. were collected in the control clusters than in the inter- funestus s. s. was 2.9%. vention clusters and the diferent was statistically signif- Discussion cant (z = 2.66, P = 0.0077).
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