Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era
Abstract Background Sri Lanka has been malaria-free since 2012, yet the risk of malaria re-introduction is high during the post-malaria elimination phase due to influx of infected individuals from endemic countries, the presence of competent Anopheles vectors, and suitable climatic conditions for ve...
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2025-08-01
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| Series: | Malaria Journal |
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| Online Access: | https://doi.org/10.1186/s12936-025-05497-1 |
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| author | Mihirini Hewavitharane Gaya Ranawaka M. D. J. S. Saparamadu Risintha Premaratne H. T. R. Jayasooriya |
| author_facet | Mihirini Hewavitharane Gaya Ranawaka M. D. J. S. Saparamadu Risintha Premaratne H. T. R. Jayasooriya |
| author_sort | Mihirini Hewavitharane |
| collection | DOAJ |
| description | Abstract Background Sri Lanka has been malaria-free since 2012, yet the risk of malaria re-introduction is high during the post-malaria elimination phase due to influx of infected individuals from endemic countries, the presence of competent Anopheles vectors, and suitable climatic conditions for vectors across Sri Lanka. This may lead to the re-emergence of autochthonous malaria in areas beyond the historically affected dry and intermediate zones. To sustain the malaria-free status, a better understanding of Anopheles species across Sri Lanka’s climatic zones is essential. This information will support the existing receptivity monitoring system. Methods Female adults of Anopheles mosquitoes were sampled monthly for two years using cattle baited trap collections (CBTC), indoor and outdoor human landing catches (HLC) and indoor hand collections (IHC), from five districts covering the dry, intermediate, and wet zones. Rainfall, temperature, and relative humidity data for the sentinel sites were obtained from the Department of Meteorology in Colombo. The study assessed Anopheles species occurrence, distribution, abundance, and densities. Spatial distribution and seasonality were analyzed using box plots, while the effects of climatic factors and collection site on malaria vectors were evaluated using negative binomial regression. Results Fifteen Anopheles mosquito species were identified, with varying abundance and densities across sites. The primary malaria vector mosquitoes were predominantly captured by HLC at all sites, except the dry zone coastal site, while secondary vectors were more common in CBTC. An. culicifacies exhibited the highest mean adult density at the intermediate zone site, with population peaks observed during the second inter-monsoon and southwest monsoon seasons at most sites, and during the northeast monsoon in the wet zone. Vector abundance was significantly influenced by climatic factors and collection site (p < 0.05); An. culicifacies densities increased with humidity, while secondary vectors showed species-specific responses to temperature, rainfall, and collection site conditions. Conclusions The spatial distribution and seasonality of Anopheles vectors provide insights on malaria vectorial efficiency in receptive areas. The intermediate zone of the island has the highest receptivity. Ongoing malaria entomological surveillance in the context of changing environmental conditions is critical for mitigating potential malaria reintroduction risks. |
| format | Article |
| id | doaj-art-8d55b6c74ec4406983690cbaeec04ce2 |
| institution | Kabale University |
| issn | 1475-2875 |
| language | English |
| publishDate | 2025-08-01 |
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| series | Malaria Journal |
| spelling | doaj-art-8d55b6c74ec4406983690cbaeec04ce22025-08-20T04:01:47ZengBMCMalaria Journal1475-28752025-08-0124111510.1186/s12936-025-05497-1Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination eraMihirini Hewavitharane0Gaya Ranawaka1M. D. J. S. Saparamadu2Risintha Premaratne3H. T. R. Jayasooriya4Anti Malaria Campaign Head Quarters, Ministry of HealthDepartment of Zoology, Faculty of Natural Sciences, The Open University of Sri LankaDepartment of Chemistry, Faculty of Natural Sciences, The Open University of Sri LankaWorld Health Organization Regional Office for South-East AsiaDepartment of Zoology, Faculty of Natural Sciences, The Open University of Sri LankaAbstract Background Sri Lanka has been malaria-free since 2012, yet the risk of malaria re-introduction is high during the post-malaria elimination phase due to influx of infected individuals from endemic countries, the presence of competent Anopheles vectors, and suitable climatic conditions for vectors across Sri Lanka. This may lead to the re-emergence of autochthonous malaria in areas beyond the historically affected dry and intermediate zones. To sustain the malaria-free status, a better understanding of Anopheles species across Sri Lanka’s climatic zones is essential. This information will support the existing receptivity monitoring system. Methods Female adults of Anopheles mosquitoes were sampled monthly for two years using cattle baited trap collections (CBTC), indoor and outdoor human landing catches (HLC) and indoor hand collections (IHC), from five districts covering the dry, intermediate, and wet zones. Rainfall, temperature, and relative humidity data for the sentinel sites were obtained from the Department of Meteorology in Colombo. The study assessed Anopheles species occurrence, distribution, abundance, and densities. Spatial distribution and seasonality were analyzed using box plots, while the effects of climatic factors and collection site on malaria vectors were evaluated using negative binomial regression. Results Fifteen Anopheles mosquito species were identified, with varying abundance and densities across sites. The primary malaria vector mosquitoes were predominantly captured by HLC at all sites, except the dry zone coastal site, while secondary vectors were more common in CBTC. An. culicifacies exhibited the highest mean adult density at the intermediate zone site, with population peaks observed during the second inter-monsoon and southwest monsoon seasons at most sites, and during the northeast monsoon in the wet zone. Vector abundance was significantly influenced by climatic factors and collection site (p < 0.05); An. culicifacies densities increased with humidity, while secondary vectors showed species-specific responses to temperature, rainfall, and collection site conditions. Conclusions The spatial distribution and seasonality of Anopheles vectors provide insights on malaria vectorial efficiency in receptive areas. The intermediate zone of the island has the highest receptivity. Ongoing malaria entomological surveillance in the context of changing environmental conditions is critical for mitigating potential malaria reintroduction risks.https://doi.org/10.1186/s12936-025-05497-1AnophelesClimatic zonesReceptivityMalariaSri Lanka |
| spellingShingle | Mihirini Hewavitharane Gaya Ranawaka M. D. J. S. Saparamadu Risintha Premaratne H. T. R. Jayasooriya Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era Malaria Journal Anopheles Climatic zones Receptivity Malaria Sri Lanka |
| title | Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era |
| title_full | Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era |
| title_fullStr | Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era |
| title_full_unstemmed | Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era |
| title_short | Seasonal abundance and climatic determinants of Anopheles vectors in Sri Lanka: its implications in the malaria post-elimination era |
| title_sort | seasonal abundance and climatic determinants of anopheles vectors in sri lanka its implications in the malaria post elimination era |
| topic | Anopheles Climatic zones Receptivity Malaria Sri Lanka |
| url | https://doi.org/10.1186/s12936-025-05497-1 |
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