Browsing by Author "Ganehiarachchi, G. A. S. M."

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Distribution of leishmaniasis cases and some demographic characters of patients recorded in the Medirigiriya medical officer of health (MOH) area, Polonnaruwa district of Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Karunarathna, D. M. N. P.; Udayanga, N. W. B. A. L.; Ranathunge, R. M. T. B.; Kumarawansha, W. K. W. S.; Ganehiarachchi, G. A. S. M.
Leishmaniasis has been recognized as one of the major challenges to the health sector of many countries. In the Sri Lankan context also, leishmaniasis infections are increasing within the past few years. Evaluation of the spatio-temporal trends in leishmaniasis incidence strongly facilitates the management of leishmaniasis. Therefore, the current study was conducted to identify recent spatial and temporal trends in leishmaniasis distribution, while assessing the characteristics of susceptible population to leishmaniasis infection in the Medirigiriya Medical Officers of Health (MOH) area in the District of Polonnaruwa, which reported the highest number of Leishmaniasis cases over the period from 2015 to 2022. Monthly records of reported leishmaniasis cases in Medirigiriya MOH area were obtained at monthly intervals from Epidemiology Unit, Sri Lanka from January, 2018 to June, 2022. Spatial maps of the recorded leishmaniasis case distribution in each Public Health Inspector (PHI) area were developed using ArcGIS (version 10.8). The paired-Chi square was used to investigate the impact of gender and age on the infection. The Medirigiriya MOH area had reported a total of 418 cases within the study period. Among the five PHI areas, Medirigiriya (34.7%) and Diulankadawala (33.8%) PHI areas reported the highest incidence of leishmaniasis cases, emerging as the high-risk areas. Meanwhile, Ambagaswewa PHI area denoted the lowest susceptibility (7.6%). As suggested by the results of the paired-Chi square test, emergence of leishmaniasis was characterized with significant spatial and temporal trends (P<0.05). The Percentage Infected Male: Female Ratio (PIMFR) suggested that the, males had a relatively high susceptibility for leishmaniasis infection than females, with an average PIMFER of 62.4:37.6. Significant shifts in the age of leishmaniasis patients were identified throughout the study period (P<0.05). Population belonging to the age group of 40 to 60 years (44%) and 21 to 40 years (25.2%) were identified as the most vulnerable age group for the incidence of leishmaniasis. On the contrary, age groups of > 60 years reported the lowest vulnerability (9.2%) for leishmaniasis infection. The identification of the potential high risk PHI areas with high susceptibility to leishmaniasis, along with the vulnerable age groups in the community would assist the relevant vector controlling agencies to concentrate their efforts, ensuring the effective controlling of leishmaniasis outbreak occurrence within the Medirigiriya MOH.
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 ABO and Rh blood groups on the egg viability and the morphometrics of laboratory-reared Aedes aegypti
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Jayakody, J. A. D. D.; Ganehiarachchi, G. A. S. M.
Dengue, a prevalent vector-borne disease in Sri Lanka, is primarily transmitted by Aedes aegypti, whose desiccation-resistant eggs contribute to its persistence. This study investigated the impact of human ABO and Rh blood groups on Ae. aegypti egg viability and morphometrics to facilitate effective vector control strategies. Eight mosquito colonies were established in the insectary at the Department of Zoology and Environmental Management, University of Kelaniya, with each colony (30 mosquitoes; 1:1 sex ratio) fed a different blood group (A+, A-, B+, B-, AB+, AB-, O+, and O-) using an artificial membrane feeder. Although Ae. aegypti eggs typically hatch sooner, this study employed a 100-day observation period to investigate whether hatching rates differed among blood groups over an extended timeframe. No special desiccation conditions were applied; eggs were kept under standard laboratory conditions to assess viability over time. Egg viability was evaluated by measuring the hatching percentage of 30 randomly selected eggs at eight intervals (4th, 10th, 25th, 40th, 55th, 70th, 85th, and 100th days) after egg laying, with three experimental replicates. Morphometrics of eggs, larvae, pupae, and adults of F1 generation were examined from 10 individuals randomly selected from each blood group. Analysis of Covariance (ANCOVA) followed by Tukey's test revealed a significant effect of ABO and Rh blood groups on egg viability (F 7,183 = 7.76; p < 0.05). The B- blood group showed the highest egg viability, while the B+ group showed the lowest during the study period. One-way analysis of variance (ANOVA) followed by Tukey's test was used to determine the effect of ABO and Rh blood groups on the egg volume and morphometrics of Ae. aegypti larvae, pupae, and adults. Egg volume was also significantly affected by blood group (F 7,72 = 2.84; p < 0.05), with B- eggs exhibiting the largest volume. B- larvae were considered the smallest because they were consistently the smallest across thoracic length (F 7,72 = 5.49; p < 0.05), abdominal length (F 7,72 = 18.20; p < 0.05), and total length (F 7,72 = 18.04; p < 0.05). Pupal cephalothorax length and width also varied significantly across blood groups (male length: F 7,32 = 3.42; p < 0.05, width: F 7,32 = 3.70; p < 0.05; female length: F 7,32 = 11.99; p < 0.05, width: F 7,32 = 9.75; p < 0.05), with B- pupae being the smallest and B+ the largest. This pattern is likely due to individuals hatching from more desiccation-resistant eggs exhibiting smaller larval and pupal sizes. Adult morphometrics, however, were unaffected by blood type. These findings suggest that variations in egg viability, egg volume, larval morphometrics, and pupal morphometrics may be linked to the nutritional composition of different blood groups, particularly the levels of triglycerides and other key metabolites such as glutamine, phenylalanine, and tyrosine that influence Ae. aegypti egg development. Further research is required to investigate these relationships and their implications for dengue vector control.
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 fresh leaves and aqueous leaf extracts of five medicinal plant specieson survival, oviposition and adult emergence of Cowpea bruchid Callosobruchus maculatus (Fab.)
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Jayasundara, S. M. J. C. K.; Ganehiarachchi, G. A. S. M.
The Cowpea bruchid, Callosobruchus maculatus, (F.) is a major storage pest of cowpea (Vigna unguiculata L.) seeds in Sri Lanka. The present study was carried out to study the effect of fresh leaves and aqueous leaf extracts of five medicinal plants namely, Pandanus amaryllifolius, Murraya koenigii, Vitex negundo, Pavetta indica and Croton aromaticus on survival, oviposition and adult emergence of Cowpea bruchid Callosobruchus maculatus at 28 ± 20C and 70 ± 5% relative humidity (RH) under the laboratory conditions. The fresh leaves were applied separately at rates of 0.0 g/20 g (control), 2 g/20 g and 5.0 g/20 g of cowpea seeds providing direct contact with the insect pest to assess contact toxicity while the effect of five different concentrations (10%, 30%, 50%, 70% and 90%) of aqueous extract of these plants were tested against oviposition and adult emergence of C . maculatus. For each treatment four containers were prepared. Five pairs of adult C . maculatus were introduced in to each container. Aqueous extract of these plants were prepared according to a reported method. Briefly, 300 g of each powdered plant material was taken into a 2 L capacity conical flask. Then 1000 mL of distilled water was added to it. It was shaken for 24 hrs using a mechanical shaker and kept for 48 hrs. The extract was separated using fine muslin cloth and volume was made up to 1000 mL. Results of contact toxicity assay showed that among the five plant species, C . aromaticus were most effective against the adult C . maculatus causing 65.45% (F 5, 18, = 9.01; P=0.00) and 83.25% (F 5, 18 = 24.33, P=0.00) mortality at 2 g and 5 g/20 g of cowpea seeds, respectively, four days after exposure to the leaves. The minimum number of eggs laid 33.5 (F 5, 18, =909.93, P=0.00) were observed in the samples treated with fresh leaves of C . aromaticus at rate 5 g/20 g of cowpea seeds while the minimum percentage progeny development 19.35% (F5, 18 =111.18, P=0.00) were observed in the samples treated with fresh leaves of C . aromaticus at rate 5 g/20 g of cowpea seeds. Maximum oviposition deterrent activity was observed in C . aromaticus at 90% concentration (55.02%) (F 4, 15, = 133.15, P=0.00). Minimum F1 adult emergence was higher in C . maculatus seeds treated with C . aromaticus at 90% concentration 46.00 (F 5, 18, =327.43, P=0.00). Results of this study clearly indicated that C. aromaticus “Wel Keppetiya”, had the highest effect on C . maculatus thus has a potential to be used as a grain protectant against C . maculatus.
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.
Infestation and emergence of Bactrocera dorsalis (Diptera: Tephritidae) on two varieties of Mangifera indica from selected locations in the wet and dry zones of Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Wijekoon, W. M. C. D.; Ganehiarachchi, G. A. S. M.; Wegiriya, H. C. E.; Vidanage, S. P.
Bactrocera dorsalis Hendel, (Diptera: Tephritidae) is one of the most serious fruit pests in Sri Lanka. There has been a dearth of documented records of infestation and damages of fruit flies on commercially important fruit varieties in the country. Hence, the present study aims to estimate the percentages of infestations and emergence of B. dorsalis on two commercially important mango varieties grown in the wet zone and dry zone in Sri Lanka. The study was conducted from September 2020 to February 2021 in Ratnapura and Embilipitiya. Ratnapura was selected as the study site in the wet zone and Embilipitiya was selected as the study site in the dry zone. In each site, two sub sampling sites were selected. Twenty ripened fruits (per variety) of Willard (Wld) and Karutha kolomban (Kc) were collected randomly from selected trees. Sampling was done once a month and fruits which have already fallen to the ground were collected. Collected fruits were observed for signs of fruit fly infestations by examining fresh oviposition marks visually using a hand lens. Fruits with confirmed infestations were placed in plastic containers with pre- sterilized sand and muslin cloth cover (storing four fruits; same variety, ≈ weight, temperature: 250 C, RH: 75-85 %) until the emergence of adults. After fifteen days, the average number of adults that emerged per fruit per location was calculated. Two indices; percentage infestations and adult fly emergence were calculated. Mean weight (g) (mean ± SE) of mango fruits used for the study were (127.47 ± 9.05) g and (203.65 ± 9.5) g for Wld and Kc respectively. The percentages of average infestation were 35% for Wld in dry zone and 30% in wet zone, and for Kc, 24% in dry zone and 20% in wet zone. For both varieties, comparatively high percentage infestations recorded from the dry zone site than that of the wet zone site (p> 0.05). The slightly high infestations for both Wld and Kc observed from dry zone site were in October 2020 and February in 2021 (during the season). The average number of adults that emerged per variety was (3.33 ±0.73) for Wld and (3.83 ±0.93) for Kc. The average adult emergence significantly varied between dry zone (4.25± 1.0) and wet zone (2.92±0.57) sites (p< 0.05). This study provides baseline information of infestation and emergence of B. dorsalis adults on two commercially important mango varieties in Sri Lanka.
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.
Oviposition attraction and larval performances of Aedes aegypti and Aedes albopictus under different leaf concentrations of invasive flora
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Chathurangi, N. E.; Weerakoon, S. N.; Ganehiarachchi, G. A. S. M.
Aedes aegypti and Aedes albopictus (Diptera: Culicidae) are the vectors of dengue and dengue hemorrhagic fever. The survival and population density of Aedes mosquitoes depend on the characteristics of the oviposition media. Thus, the objective of the present study was to evaluate the attraction and larval development of Ae. aegypti and Ae. albopictus to different oviposition media prepared using alien invasive flora in rubber plantations. Three oviposition media, each having 25%, 50%, 75% and 100% concentrations, were prepared by the selected invasive flora namely, Guinea grass (Megathyrsus maximus), Alligator weed (Alternanthera philoxeroides) and Austroeupatorium (Austroeupatorium inulifolium) to evaluate the attraction of mosquito populations in a rubber plantation at Palmadulla (6°36'50.5"N 80°33'03.3"E). Forty-five ovitraps (four concentrations from each infusion with three blanks were placed on the identified sites for vector breeding in a completely randomized manner for four days. The experimental setup was replicated three times. The number of eggs at each concentration of leaf extracts was enumerated and reared under laboratory conditions until adults. The emerged mosquitoes were identified using morphological taxonomic keys. The highest number of Aedes eggs (n=32) were found in ovitraps with 25% concentration of M. maximus. At 25% concentration, the highest hatch rate (65%) was obtained from A. philoxeroides and at 50% of concentration, the highest hatch rate (75%) was obtained from M. maximus infusion. At 75% of concentration, the highest hatch rate (75%) was obtained from M. maximus infusion during the second day of rearing. But at 100% of concentration, the highest hatch rate (50%) was obtained by M. maximus within the first day of rearing. The highest ovitrap positivity index (number of positive ovitraps/number of ovitraps placed X 100) value of 100, was obtained by A. philoxeroides at concentrations of 25%, 50%, and 75%, by M. maximus at concentrations of 25, 50, and 100%, and by A. inulifolium at concentrations of 25% and 75%. A. philoxeroides achieved the lowest value 33.3 at 100% concentration. The maximum Egg Density Index (Total number of eggs/Total number of positive traps) value 22.0 was obtained by M. maximus at 25% concentration and the minimum value 2.5 was obtained by A. inulifolium at 100% concentration. The larval density shows a significant difference with the different plant infusions. (F=12.90, df =2, P<0.05) and also in different concentration (F=13.81, df=3, P<0.05). The interaction of plant infusion type and their concentrations showed a significant effect on the larval densities (Two-Way ANOVA, F=6.57, df =6, P<0.05). The leaf infusions attracted gravid females of both Ae. aegypti and Ae. albopictus. The mosquitoes exhibit a vastly different response to each plant species. The present study demonstrates the potential of plant infusions in stimulating oviposition by Aedes mosquitoes using ovitraps in mosquito surveillance. These findings confirm the critical importance of the plant species that are used to make leaf concentrations.
Preparation and laboratory evaluation of herbal stick formulations using mosquito repellent plant materials against Aedes aegypti and Aedes albopictus
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Fernando, M. U. D.; Jayasooriya, G. A. J. S. K.; Samaraweera, S. A. P. T.; Ganehiarachchi, G. A. S. M.
Dengue, caused by Aedes mosquitoes, remains a significant public health issue. Current vector control methods have been unable to effectively reduce the Aedes populations, thereby failing to control dengue transmission rates. This study has attempted to develop an effective and practical tool for the control of dengue transmission by dengue vectors, Aedes aegypti and Aedes albopictus by reducing vector population and human-vector contact using mosquito repellent plant materials. In the current study, to prepare the incense herbal sticks Ocimum Basilicum, Tagetes erecta, Mentha piperita, Syzygium aromaticum, Cinnamomum verum, Salvia rosmarinus, Laurus nobilis and Cymbopogon nardus were used as herbal materials while saw dust, charcoal powder and “Patta” powders were used as inactive ingredients. The final weight of the herbal stick was 1.5 g and three different herbal formulas were prepared. Adult mosquitoes were reared in the laboratory from eggs collected via ovitraps deployed in various locations. F1 generation of mosquitoes were used and, their age of exposure was 2 weeks. Ytube experiments (n = 21) were conducted to assess the repellent activity of incense sticks impregnated with different herbal extracts. Additionally, smoke toxicity tests were performed on adult female mosquitoes. Statistical analyses were conducted using JMP 5.01 (SAS Institute Inc., 2002). Data were initially tested for homogeneity of variances using O’Brien’s test (p < 0.05). For homogenous variances, ANOVA was applied; if variances were heteroscedastic, data transformation was attempted to rectify the issue. Persistent heteroscedasticity led to the use of Welch ANOVA. Significant treatment effects were further analyzed using the Tukey-Kramer HSD test (p < 0.05) to compare the mean values. Test results clearly indicated that all three treatments resulted in significant reductions in attraction of both A. aegypti (F2,6 = 10.23, p < 0.05); and A. albopictus (F2,6 = 13.07, p < 0.05). Among the three formulations, incense stick that contains 45 % of active ingredients acted as the best repellent to Aedes species. The smoke toxicity test results depicted that both Aedes species showed significant toxicity to three treatments i.e. 5%, 25% and 45%, p < 0.01). The highest mortality was obtained with 45% of active ingredients, followed by moderate toxicity at 25%, and the lowest mortality at 15%, demonstrating a dose-response relationship. Therefore, incense sticks that contain 45 % herbal ingredients could be recommended as supplementary method to reduce human-vector contact to both A. aegypti and A. albopictus mosquito species. For further improvement, long-term monitoring procedures should be established to evaluate the long-term effectiveness and user acceptability of these mosquito repellent formulations.
Seasonal forecasting of Bactrocera dorsalis Hendel, 1912 (Diptera: Tephritidae) in bioclimatic zones of Sri Lanka using the SARIMA model
(CABI Agriculture and Bioscience, 2024) Wijekoon, W. M. C. D.; Ganehiarachchi, G. A. S. M.; Wegiriya, H. C. E.; Vidanage, S. P.
Bactrocera dorsalis Hendel is a severe fruit pest that causes significant economic losses globally. Despite B. dorsalis having been distributed mostly across Asia, studies on its current and future density variation in Sri Lanka are sparse to date. The present study was thus carried out to assess the contemporary density variation (2020–2022) and future density fluctuation (2023–2025) of B. dorsalis in bioclimatic zones of Sri Lanka. The density was assessed using the monthly-based fruit fly trap collection method from randomly selected 40 locations in all bioclimatic zones (wet, intermediate, dry, and arid). The SARIMA modelling technique was applied for delineating the best-fit model and for density forecasting in each bioclimatic zone. The density variations were depicted for the year and for the bioclimatic zone (2020–2025) by colour intensity maps using QGIS. According to the findings, B. dorsalis shows a seasonal component to its year-round density variation and an ascending trend in its density from 2020 to 2025. Density forecasting records a 20%, 30%, 26%, and 37% density increase in the wet, intermediate, dry, and arid zones, respectively, in 2025. In 2025, the highest predicted B. dorsalis density from the arid zone and the lowest predicted density from the wet zone were recorded. This study contains the first forecasting attempt for B. dorsalis density using the SARIMA approach as well as the application of colour-intensity depiction for its density variation in Sri Lanka, which leads decision makers and stakeholders in economic agriculture to plan the scientific management of B. dorsalis to avoid its current and potential future threat to the country’s fruit industry.