Behavioral Responses of Malaria Vectors, <I>Anopheles minimus</I> Complex, to Three Classes of Agrochemicals in Thailand

Information on factors influencing the behavioral responses of mosquitoes to repellents is lacking and poorly understood, especially in the Anopheles species, night-biting mosquitoes. Our goal was to investigate the impact of different time periods on circadian activity and behavioral responses of two malaria vectors, Anopheles minimus and An. dirus, to 5% DEET using an excito-repellency test system. Each mosquito species was exposed to the repellent during the daytime (06.00–18.00) and nighttime (18.00–06.00), and time of observation was further divided into four 3-h intervals. Significant escape responses were observed between daytime and nighttime for An. minimus in both noncontact and contact tests. An. dirus showed statistical differences in contact irritancy escape response, whereas no significant difference was found in noncontact repellency tests. Both mosquito species showed more significantly higher escape responses when exposed to DEET during the afternoon and late in the night. This finding indicates that the time of testing may affect the behavioral responses of mosquitoes to repellents, especially in An. minimus and An. dirus. A better understanding of nocturnally active mosquito behavioral responses spanning from dusk to dawn would assist in optimizing product development, screening, and effective evaluation.

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The impact of transfluthrin on the spatial repellency of the primary malaria mosquito vectors in Vietnam: Anopheles dirus and Anopheles minimus

Malaria Journal ◽

10.1186/s12936-019-3092-4 ◽

2020 ◽

Vol 19 (1) ◽

Cited By ~ 1

Author(s):

Nicholas J. Martin ◽

Vu S. Nam ◽

Andrew A. Lover ◽

Tran V. Phong ◽

Tran C. Tu ◽

...

Keyword(s):

Vector Control ◽

Large Scale ◽

Limit Of Detection ◽

Malaria Vectors ◽

Adult Mosquito ◽

Anopheles Dirus ◽

Anopheles Minimus ◽

Control Programmes ◽

The Impact ◽

Spatial Repellency

Abstract Background The complexity of mosquito-borne diseases poses a major challenge to global health efforts to mitigate their impact on people residing in sub-tropical and tropical regions, to travellers and deployed military personnel. To supplement drug- and vaccine-based disease control programmes, other strategies are urgently needed, including the direct control of disease vectors. Modern vector control research generally focuses on identifying novel active ingredients and/or innovative methods to reduce human-mosquito interactions. These efforts include the evaluation of spatial repellents, which are compounds capable of altering mosquito feeding behaviour without direct contact with the chemical source. Methods This project examined the impact of airborne transfluthrin from impregnated textile materials on two important malaria vectors, Anopheles dirus and Anopheles minimus. Repellency was measured by movement within taxis cages within a semi-field environment at the National Institute of Hygiene and Epidemiology in Hanoi, Vietnam. Knockdown and mortality were measured in adult mosquito bioassay cages. Metered-volume air samples were collected at a sub-set of points in the mosquito exposure trial. Results Significant differences in knockdown/mortality were observed along a gradient from the exposure source with higher rates of knockdown/mortality at 2 m and 4 m when compared with the furthest distance (16 m). Knockdown/mortality was also greater at floor level and 1.5 m when compared to 3 m above the floor. Repellency was not significantly different except when comparing 2 m and 16 m taxis cages. Importantly, the two species reacted differently to transfluthrin, with An. minimus being more susceptible to knockdown and mortality. The measured concentrations of airborne transfluthrin ranged from below the limit of detection to 1.32 ng/L, however there were a limited number of evaluable samples complicating interpretation of these results. Conclusions This study, measuring repellency, knockdown and mortality in two malaria vectors in Vietnam demonstrates that both species are sensitive to airborne transfluthrin. The differences in magnitude of response between the two species requires further study before use in large-scale vector control programmes to delineate how spatial repellency would impact the development of insecticide resistance and the disruption of biting behaviour.

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Molecular Identification of Anopheles minimus sensu lato and Anopheles dirus sensu lato (Diptera: Culicidae) from Kampong Spoe Province, Cambodia

Zootaxa ◽

10.11646/zootaxa.1028.1.3 ◽

2005 ◽

Vol 1028 (1) ◽

pp. 37 ◽

Cited By ~ 2

Author(s):

YAJUN MA ◽

SOK VANNE ◽

SHIZHU LI ◽

PIN YANG

Keyword(s):

Internal Transcribed Spacer ◽

Malaria Vectors ◽

Sequence Variant ◽

Sequence Variants ◽

Anopheles Dirus ◽

Anopheles Minimus ◽

The Third ◽

Species Complexes ◽

Second Internal Transcribed Spacer ◽

First Time

Anopheles dirus and An. minimus are primary malaria vectors in Cambodia. Both are species complexes and can be confused on the basis of adult morphology. The second internal transcribed spacer (ITS2) and the third domain (D3) in 28S of ribosomal DNA (rDNA) of An. minimus sensu lato and An. dirus s. l. were sequenced and analyzed. Three species (An. minimus A, An. sawadwongporni, and An. pampanai) and three sequence variants (MYJ-1, MYJ-2 and MYJ-3) were identified in An. minimus s. l. Two species (An. dirus A, An. pampanai) and one sequence variant (MYJ-1) were identified in An. dirus s. l. Anopheles sawadwongporni is recorded for the first time in Cambodia.

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BIOEKOLOGI VEKTOR MALARIA PADA BERBAGAI EKOSISTEM DI KABUPATEN DONGGALA, PROVINSI SULAWESI TENGAH

Vektora Jurnal Vektor dan Reservoir Penyakit ◽

10.22435/vk.v11i1.1139 ◽

2019 ◽

Vol 11 (1) ◽

pp. 1-10

Author(s):

Riyani Setiyaningsih ◽

Lasmiati Lasmiati ◽

Mujiyono Mujiyono ◽

Mega Tyas Prihatin ◽

Heru Priyanto ◽

...

Keyword(s):

Forest Ecosystems ◽

Light Trap ◽

Malaria Vectors ◽

Fish Farms ◽

Anopheles Subpictus ◽

Breeding Sites ◽

Anopheles Minimus ◽

Survey Results ◽

Central Sulawesi ◽

Anopheles Barbirostris

Central Sulawesi is one of the malaria-endemic areas in Indonesia. Anopheles nigerrimus, Anopheles barbirostris, Anopheles subpictus, Anopheles parangensis, Anopheles flavirostris and Anopheles minimus were confirmed as malaria vectors. Researchers believed that there might have a distinctly different distribution and diversity of the vectors in different ecosystems. The purpose of the current study was to investigate and analyze the distribution and diversity of suspected malaria vectors (Anopheles spp.) in various ecosystems. Adult mosquitoes were collected using some methods e.g. human man landing method, animal baited trap, mosquito caught around the cage, using sweep net and the light trap. The sporozoites of Plasmodium infecting the caught mosquitoes were identified and examined using PCR. In addition, a survey on potential breeding sites of the mosquitoes. Based on the survey results, the mosquitoes species caught in the non-forest ecosystems near the settlements and positively infected by Plasmodium were An. ludlowae, An. flavirostris, and An. vagus. Meanwhile, the malaria vectors caught in the non-forest ecosystems far from the settlements were An. maculatus and An. subpictus. The results also demonstrated that An. barbirostris was detected as a malaria vector in the coastal area near the settlement. The ponds, rivers and fish farms were potential breeding sites for the mosquitoes. The suspected malaria vectors (Anopheles spp) spread throughout ecosystems e.g. forests, non-forests and coasts. The high risk of ecosystems for malaria transmission was the non-forest ecosystems near the settlements, the non-forest far away from the settlements, and the coasts near the settlements.

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