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Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India?
BACKGROUND: Bluetongue virus (BTV) is transmitted by Culicoides biting midges and causes bluetongue (BT), a clinical disease observed primarily in sheep. BT has a detrimental effect on subsistence farmers in India, where hyperendemic outbreaks impact on smallholdings in the southern states of the co...
Autores principales: | , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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BioMed Central
2017
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5286563/ https://www.ncbi.nlm.nih.gov/pubmed/28143560 http://dx.doi.org/10.1186/s13071-017-1992-0 |
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author | De Keyser, Rien Cassidy, Clare Laban, Swathi Gopal, Prakash Pickett, John A. Reddy, Yarabolu K. Prasad, Minakshi Prasad, Gaya Chirukandoth, Sreekumar Senthilven, Kandasamy Carpenter, Simon Logan, James G. |
author_facet | De Keyser, Rien Cassidy, Clare Laban, Swathi Gopal, Prakash Pickett, John A. Reddy, Yarabolu K. Prasad, Minakshi Prasad, Gaya Chirukandoth, Sreekumar Senthilven, Kandasamy Carpenter, Simon Logan, James G. |
author_sort | De Keyser, Rien |
collection | PubMed |
description | BACKGROUND: Bluetongue virus (BTV) is transmitted by Culicoides biting midges and causes bluetongue (BT), a clinical disease observed primarily in sheep. BT has a detrimental effect on subsistence farmers in India, where hyperendemic outbreaks impact on smallholdings in the southern states of the country. In this study, we establish a reliable method for testing the toxic effects of deltamethrin on Culicoides and then compare deltamethrin with traditional control methods used by farmers in India. RESULTS: Effects of deltamethrin were initially tested using a colonised strain of Culicoides nubeculosus Meigen and a modified World Health Organisation exposure assay. This method was then applied to field populations of Culicoides spp. in India. The field population of C. oxystoma in India had a greater LC(50) (0.012 ± 0.009%) for deltamethrin than laboratory-reared C.nubeculosus (0.0013 ± 0.0002%). Exposure of C. nubeculosus to deltamethrin at higher ambient temperatures resulted in greater rates of knockdown but a lower mortality rate at 24 h post-exposure. Behavioural assays with C. nubeculosus in WHO tubes provided evidence for contact irritancy and spatial repellence caused by deltamethrin. The field experiments in India, however, provided no evidence for repellent or toxic effects of deltamethrin. Traditional methods such as the application of neem oil and burning of neem leaves also provided no protection. CONCLUSIONS: Our study demonstrates that field-collected Culicoides in India are less susceptible to deltamethrin exposure than laboratory-bred C. nubeculosus and traditional methods of insect control do not provide protection to sheep. These low levels of susceptibility to deltamethrin have not been recorded before in field populations of Culicoides and suggest resistance to synthetic pyrethrioids. Alternative insect control methods, in addition to vaccination, may be needed to protect Indian livestock from BTV transmission. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-017-1992-0) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-5286563 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2017 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-52865632017-02-03 Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? De Keyser, Rien Cassidy, Clare Laban, Swathi Gopal, Prakash Pickett, John A. Reddy, Yarabolu K. Prasad, Minakshi Prasad, Gaya Chirukandoth, Sreekumar Senthilven, Kandasamy Carpenter, Simon Logan, James G. Parasit Vectors Research BACKGROUND: Bluetongue virus (BTV) is transmitted by Culicoides biting midges and causes bluetongue (BT), a clinical disease observed primarily in sheep. BT has a detrimental effect on subsistence farmers in India, where hyperendemic outbreaks impact on smallholdings in the southern states of the country. In this study, we establish a reliable method for testing the toxic effects of deltamethrin on Culicoides and then compare deltamethrin with traditional control methods used by farmers in India. RESULTS: Effects of deltamethrin were initially tested using a colonised strain of Culicoides nubeculosus Meigen and a modified World Health Organisation exposure assay. This method was then applied to field populations of Culicoides spp. in India. The field population of C. oxystoma in India had a greater LC(50) (0.012 ± 0.009%) for deltamethrin than laboratory-reared C.nubeculosus (0.0013 ± 0.0002%). Exposure of C. nubeculosus to deltamethrin at higher ambient temperatures resulted in greater rates of knockdown but a lower mortality rate at 24 h post-exposure. Behavioural assays with C. nubeculosus in WHO tubes provided evidence for contact irritancy and spatial repellence caused by deltamethrin. The field experiments in India, however, provided no evidence for repellent or toxic effects of deltamethrin. Traditional methods such as the application of neem oil and burning of neem leaves also provided no protection. CONCLUSIONS: Our study demonstrates that field-collected Culicoides in India are less susceptible to deltamethrin exposure than laboratory-bred C. nubeculosus and traditional methods of insect control do not provide protection to sheep. These low levels of susceptibility to deltamethrin have not been recorded before in field populations of Culicoides and suggest resistance to synthetic pyrethrioids. Alternative insect control methods, in addition to vaccination, may be needed to protect Indian livestock from BTV transmission. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-017-1992-0) contains supplementary material, which is available to authorized users. BioMed Central 2017-01-31 /pmc/articles/PMC5286563/ /pubmed/28143560 http://dx.doi.org/10.1186/s13071-017-1992-0 Text en © The Author(s). 2017 Open AccessThis 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. |
spellingShingle | Research De Keyser, Rien Cassidy, Clare Laban, Swathi Gopal, Prakash Pickett, John A. Reddy, Yarabolu K. Prasad, Minakshi Prasad, Gaya Chirukandoth, Sreekumar Senthilven, Kandasamy Carpenter, Simon Logan, James G. Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title | Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title_full | Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title_fullStr | Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title_full_unstemmed | Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title_short | Insecticidal effects of deltamethrin in laboratory and field populations of Culicoides species: how effective are host-contact reduction methods in India? |
title_sort | insecticidal effects of deltamethrin in laboratory and field populations of culicoides species: how effective are host-contact reduction methods in india? |
topic | Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5286563/ https://www.ncbi.nlm.nih.gov/pubmed/28143560 http://dx.doi.org/10.1186/s13071-017-1992-0 |
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