Browsing by Author "Gunathilaka, R. A. K. M."

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Effect of ABO and Rh blood groups on host preference, oviposition success, and development of laboratory‑reared Aedes aegypti
(International Journal of Tropical Insect Science, 2022) Galhena, G. K. D. N.; Ganehiarachchi, G. A. S. M.; Gunathilaka, R. A. K. M.; Jayatunga, D. P. W.
Aedes aegypti is the primary dengue vector in Sri Lanka that causes the massive public health problem of Dengue Fever (DF) and Dengue Hemorrhagic Fever (DHF) on the island. It is an anthropophilic mosquito that shows preferential feeding depending on the host blood type. Hence, the study was conducted to investigate the effects of human ABO and Rh blood groups on host attractiveness, feeding, oviposition and other life-history traits of Aedes aegypti. Data of DF and DHF patients were collected from some selected hospitals in the Western province. Subsequently, mated female Ae. aegypti mosquitoes were exposed to eight blood groups (A − , A + , B − , B + , AB − , AB + , O − , O + ) using human volunteers to investigate the land- ing and feeding preferences. Furthermore, oviposition success, adult longevity, progeny longevity, larval duration, larval mortality, pupal duration, and adult fecundity were examined. Accordingly, people with the O + blood group were the most typical group infected with DF and DHF in 2017 and 2018. However, the peak landing and feeding preferences were observed for O − . Besides, the current findings indicated that human ABO and Rh blood types did not significantly affect life-history parameters including oviposition success, larval duration, pupal duration, larval mortality, adult longevity, progeny longevity, and fecundity of Ae. aegypti. Eventually, it can be concluded that dengue infection risk varies with the ABO and Rh blood groups depending on their unequal prevalence in the community as well as their association with mosquito performance.
Effect of ABO and Rh blood groups on host preference, oviposition success, and development of laboratory‑reared Aedes aegypti
(African Association of Insect Scientists, 2023) Galhena, G. K. D. N.; Ganehiarachchi, G. A. S. M.; Gunathilaka, R. A. K. M.; Jayatunga, D. P. W.
(DF) and Dengue Hemorrhagic Fever (DHF) on the island. It is an anthropophilic mosquito that shows preferential feeding depending on the host blood type. Hence, the study was conducted to investigate the effects of human ABO and Rh blood groups on host attractiveness, feeding, oviposition and other life-history traits of Aedes aegypti. Data of DF and DHF patients were collected from some selected hospitals in the Western province. Subsequently, mated female Ae. aegypti mosquitoes were exposed to eight blood groups (A−, A+,B−,B+,AB−,AB+,O−,O+) using human volunteers to investigate the landing and feeding preferences. Furthermore, oviposition success, adult longevity, progeny longevity, larval duration, larval mortality, pupal duration, and adult fecundity were examined. Accordingly, people with the O+ blood group were the most typical group infected with DF and DHF in 2017 and 2018. However, the peak landing and feeding preferences were observed for O−. Besides, the current findings indicated that human ABO and Rh blood types did not significantly affect life-history parameters including oviposition success, larval duration, pupal duration, larval mortality, adult longevity, progeny longevity, and fecundity of Ae. aegypti. Eventually, it can be concluded that dengue infection risk varies with the ABO and Rh blood groups depending on their unequal prevalence in the community as well as their association with mosquito performance.
Effect of delayed mating on reproductive performance and life-history parameters of dengue vector Aedes aegypti
(Cambridge University Press, 2022) Gunathilaka, R. A. K. M.; Jayatunga, D. P. W.; Ganehiarachchi, G. A. S. M.
Dengue is a fast-spreading mosquito-borne viral disease in the world. The primary vector of the disease is Aedes aegypti of the family Culicidae. It is a container breeder. Since a vaccine or a drug has not been developed against dengue, vector control appears to be the best method so far to control dengue. The current study was conducted to determine the effect of delayed mating on fecundity, fertility, life-history parameters, and longevity of Ae. aegypti, because such information can help formulate integrated vector control strategies involving the release of sub-fertile males into the environment. During this study, mating was delayed by 0, 2, 5, and 8 days after emergence. Males and females were separated by hand at the pupal stage using the apparent size difference of the sexes. The separated pupae were kept in separate cages until emergence. When mating was delayed for 8 days, the number of eggs laid by the female declined by 38%, and the percentage number of eggs that hatched reduced by 24%. However, the percentage of larval mortality, duration of the larval and pupal periods, and adult longevity were not significantly affected. The current results indicate that delayed mating has a negative effect on the reproductive performance of vector mosquitoes.
Effect of delayed mating on reproductive performance and life-history parameters of dengue vector Aedes aegypti
(Bulletin of Entomological Research, 2022) Gunathilaka, R. A. K. M.; Jayatunga, D. P. W.; Ganehiarachchi, G. A. S. M.
Dengue is a fast-spreading mosquito-borne viral disease in the world. The primary vector of the disease is Aedes aegypti of the family Culicidae. It is a container breeder. Since a vaccine or a drug has not been developed against dengue, vector control appears to be the best method so far to control dengue. The current study was conducted to determine the effect of delayed mating on fecundity, fertility, life-history parameters, and longevity of Ae. aegypti, because such information can help formulate integrated vector control strategies involving the release of sub-fertile males into the environment. During this study, mating was delayed by 0, 2, 5, and 8 days after emergence. Males and females were separated by hand at the pupal stage using the apparent size difference of the sexes. The separated pupae were kept in separate cages until emergence. When mating was delayed for 8 days, the number of eggs laid by the female declined by 38%, and the percentage number of eggs that hatched reduced by 24%. However, the percentage of larval mortality, duration of the larval and pupal periods, and adult longevity were not significantly affected. The current results indicate that delayed mating has a negative effect on the reproductive performance of vector mosquitoes.
Effect of oviposition-site deprivation on reproductive performance and life history parameters of dengue vector Aedes aegypti
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Gunathilaka, R. A. K. M.; Ganehiarachchi, G. A. S. M.
Dengue and dengue hemorrhagic fever is the most important arthropod-borne viral disease that occurs in tropical and subtropical regions in the world. Annually 390 million new dengue cases are being reported from the 128 dengue-endemic countries. Aedes aegypti belonging to the family Culicidae is the primary vector that transmits the disease. Since there is no vaccine or a drug to prevent the disease, controlling programs are mainly focused on the vector controlling strategies. The primary vector is a container breeder and the widely used control method, source reduction, interrupts the oviposition of females. This will prevent or delay the oviposition of females leading to oviposition-site deprivation. Therefore, it is hypothesized that oviposition-site deprivation may affect the reproductive performance, life history parameters and longevity of Ae. aegypti. Thus, the objective of the study was to determine the effect of oviposition-site deprivation on fecundity, fertility, larval mortality, total larval duration, pupal duration and longevity of Ae. aegypti. Oviposition-site deprivation was done by blocking the access to the oviposition substrate. Mosquito batches were allowed to access an oviposition substrate separately on the day of blood feeding, 2, 4, 6 and 8 days after blood feeding. They were regularly fed with a 10 % sugar solution as the energy source. According to the results the mean number of eggs laid by the females subjected to different egg retention periods varied significantly. The highest number of eggs (99.53 ± 5.02) were laid by the females subjected to 8-day egg retention period and it was a 69% increase compared with the females who were not subjected to oviposition-site deprivation. However, the fertility (84.93 ± 0.47), percentage larval mortality (14.33 ± 1.16), total larval duration (105.60 ± 2.40 hours), pupal duration (41.60 ± 0.98 hours) and longevity (19.40 ± 0.29 days) did not show any significant difference (One-Way ANOVA, DF = 4, P > 0.05) with the oviposition-site deprivation. Increase of fecundity leads to an increase of vector population. Therefore, an increase of fecundity will act opposite to the desired goal of source reduction. However, the effect of the oviposition-site deprivation driven increased fecundity to the next gonotrophic cycle is not known. Alternatively, complete elimination of breeding sites in an area may support the mosquitoes to develop adaptations to use alternative breeding habitats such as estuaries. So, from the scientific viewpoint, complete elimination of breeding sites through source reduction may be disadvantageous. Also, oviposition-site deprivation through source reduction alone may not be an effective way to control vector populations of Ae. aegypti. Thus, it is important to have a clear knowledge on the effect of oviposition-site deprivation on mosquito physiology, reproductive performance, life history parameters and the longevity of the vector mosquitoes when adopting vector controlling strategies.
Insights into the effects of interspecific larval competition on Aedes aegypti (L.) and Aedes albopictus (Skuse) mosquitoes and dengue transmission
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Shalinda, K. A. N.; Jayasooriya, G. A. J. S. K.; Gunathilaka, R. A. K. M.; Samaraweera, S. A. P. T.; Ganehiarachchi, G. A. S. M.
In Sri Lanka, both Aedes aegypti and Aedes albopictus mosquitoes are prevalent and contribute to the transmission of dengue, a significant public health concern with high morbidity and mortality rates. Ae. aegypti predominates in urban environments and is a primary driver of dengue outbreaks, whereas Ae. albopictus, adaptable and found in both urban and rural areas, poses a persistent threat. While the effects on their life history and morphometrics when reared in isolation have been well investigated, the effects of their coexistence, which more closely reflect real-life scenarios in many parts of Sri Lanka, have not been thoroughly explored. Thus, this study addresses this gap by investigating the effects of interspecific larval competition on key biological parameters of both Ae. aegypti and Ae. albopictus, specifically focusing on larval duration, survival rates, and body size, particularly wing length. The study was conducted in the School of Entomology at the Medical Research Institute (MRI) in Colombo 08, Sri Lanka. The experimental design involved controlled laboratory settings where Ae. aegypti and Ae. albopictus larvae were reared either in isolation or in mixed-species groups. Eggs of both species, obtained from laboratory cultures, were hatched using the vacuum method to synchronize hatching times. Larvae were reared in 100 mL transparent plastic containers, with fifty larvae of each species reared separately and twenty-five larvae of each species reared together in mixed-species containers, each filled with 50 mL of distilled water. Larvae were fed with finely ground commercial fish food (Apex©), and feeding amounts were increased daily according to larval instar needs. Wing length was determined by mounting the separated wings on slides and measuring the radius vein length using a scale-mounted light microscope. Statistical analyses, including two-sample t-tests, were conducted using MINITAB 14 (Minitab Inc., 2004) to assess the effects of interspecific competition. Results indicate that both Ae. aegypti and Ae. albopictus exhibited longer larval durations when reared in mixedspecies conditions. Survival rates were not statistically significant for Ae. aegypti (p > 0.05) but increased in mixed-species environments, whereas survival of Ae. albopictus was significantly reduced in mixed-species conditions (p < 0.05). Morphometric analyses revealed significant differences in wing length between males and females of both species (p < 0.05). In males, wing length differences were not statistically significant (p > 0.05), but Ae. aegypti tended to have longer wings compared to Ae. albopictus in mixed-species environments. However, in females, wing length was significantly higher in Ae. aegypti and lower in Ae. albopictus (p < 0.05) when reared in mixed-species environments. In conclusion, interspecific competition between Ae. aegypti and Ae. albopictus influences larval development, survival rates, and body size differently for each species. Mixed-species conditions result in prolonged larval stages, altered survival rates, and distinct morphometric changes (i.e. wing length), with Ae. aegypti demonstrating characteristics suggestive of relative strength or competitive advantage compared to Ae. albopictus. The findings highlight the intricate dynamics of interspecific competition among Aedes mosquito species, emphasizing the need to consider these ecological interactions in strategies for controlling mosquito populations and mitigating dengue transmission, leading to more effective disease prevention efforts.