BackgroundDirofilariasis is a vector-borne parasitic infection caused by filarial nematodes belonging to the genus Dirofilaria. Sri Lanka has reported the highest prevalence of human dirofilariasis cases in Asia. Molecular-based detection of Dirofilaria vector species has not yet been conducted in Sri Lanka, which could provide more sensitive information by directly detecting and analyzing genetic material. The present study aimed to analyze the distribution of canine dirofilariasis and to determine the Dirofilaria vector species in Gampaha district, Sri Lanka, using molecular-based techniques.MethodsMosquito sampling (n=300) was performed from October to December 2024 from different sites in Gampaha district. The gut of the mosquitoes was dissected. Genomic DNA extraction followed by PCR was performed with specific primers for Dirofilaria species. The blood samples of different dog breeds (n=500) were also collected from the Gampaha district, and they were subjected to DNA extraction, PCR amplification, and sequencing. The data were analyzed by bioinformatics tools.ResultsAnalysis of the sequence data confirmed the first molecular detection of the dirofilariasis vector in Sri Lanka; Armigeres subalbatus as the potential vector mosquito for Dirofilaria repens and Dirofilaria asiatica n. sp. The sequence of D. repens recorded from Sri Lanka is not available in the literature/or any database, and the sequence of D. repens was also determined. Further, in different dog breeds, the infection rate of microfilariae was found to be different, and the Rottweiler breed was recorded with the highest infection rate. D. repens and D. asiatica n. sp. were found in dog blood samples. The phylogenetic analysis revealed that the query sequence of the D.repens parasites isolated from the present study showed considerable homology and proximity to the D. repens recorded from India.ConclusionArmigeres subalbatus is the vector mosquito for D.repens and D.asiatica n. sp., which caused canine dirofilariasis in the Gampaha district of Sri Lanka. No other mosquito species were identified as potential vectors of Dirofilaria species in the study area. This is, to our knowledge, the first D. repens sequence found in the Gampaha district, Sri Lanka. The present study findings provide very important insights for targeted vector control programs for Dirofilaria parasites in Sri Lanka.

Devising a natural and an effective repellent system is the challenge that needs to be addressed to meet the current demand among the people, despite the progress made in the mosquito control. The effort towards this goal should constitute; natural repellent, biodegradability, higher repellent loading, sustained release of the repellent. In this work, natural, biodegradable, eco-friendly and long-lasting mosquito repellent has been prepared with higher loading of citronella oil (1 %) in Polyvinyl alcohol (PVA) nanofibers. Uniaxial (CP-U) and coaxial (CP-C) nanofiber-composites were electrospun using non-toxic, biodegradable PVA at 10 % w/w and citronella oil. It was found that maintaining the outer:inner flow rate ratio at 5:2 in coaxial process is imperative to produce good fibers. Average fiber diameter of CP-U fibers was 138.5 +/- 62.5 nm and for CP-C fibers it was 367.3 +/- 160.1 nm. TEM analysis confirmed the core-shell structure formed in CP-C fibers by coaxial electrospinning. FTIR analysis indicated CEO incorporation in both composites and thermal analyses showed mass losses corresponding to CEO decomposition, with CP-U fibers exhibiting better thermal stability due to stronger interactions between the oil and polymer. Encapsulation efficiency and loading capacity were 20.19 % +/- 0.34 and 1.83 % +/- 0.03 for CP-U, and 50.25 % +/- 0.32 and 14.85 % +/- 0.09 for CP-C, respectively. Further, release patterns and release kinetics were studied. CP-C fibers can effectively release 94.14 % of the encapsulated oil providing an extended protection window compared to matrix encapsulation (68.75 %) after 168 hours. Release kinetics followed the Korsmeyer-Peppas model, with CP-U exhibiting Fickian diffusion (n < 0.5) and CP-C showing non-Fickian diffusion (0.5

Dengue fever remains a significant public health concern in Sri Lanka, leading to recurrent epidemics and imposing substantial socio-economic burdens. This study aimed to assess the efficacy of the Sterile Insect Technique (SIT) against Aedes albopictus (Skuse), the predominant dengue vector in the country, through a pilot field trial of an Integrated Vector Management (IVM) strategy including the SIT. The pilot trial was conducted in the Gampaha district, which reports the second-highest number of dengue cases in the country. A total of 3,300,000 sterile males, exposed to a 50 Gy radiation dose, were released over 33 weeks (100,000/week) within a 30-hectare release area. Entomological assessments were conducted at 115 trapping stations over a period of 71 weeks (October 2020–August 2022). Induced sterility of 98.16% in mosquito eggs was reached within the release area as compared to the control area (binomial generalized linear mixed model, deviance 2.408, df = 2, p = 0.016), indicating a notable impact of the SIT. The trial achieved nearly 98% suppression of adult vector mosquitoes, with a sustained suppression effect for 13 weeks post cessation of releases. These findings suggest that SIT can be effectively integrated as a potential additional tool into the future IVM strategy in Sri Lanka.

Objective: To confirm the presence of Culex (Cx.) (Lophoceraomyia) cinctellus in Sri Lanka using morphological and molecular evidence. Methods: From October 2019 to April 2020, mosquito surveillance was conducted fort-nightly in the Banduragoda Public Health Inspector area. Larvae were collected using standard siphoning methods, while adults were sampled using Cattle Baited Trap, Gravid Traps, Light Traps, Bird-Baited Traps, Dog Baited Traps, and diurnal human landing collections. Specimens were transported to the Entomology Laboratory at the Medical Research Institute for identification. Morphological identification was performed using standard taxonomic keys. Molecular confirmation was achieved through DNA sequencing of mosquito head and thoracic regions, followed by sequence analysis using NCBI BLAST and Geneious software (version 7.1.3). Results: Adults of Cx. cinctellus were identified in Bird-Baited Traps and human bait collections. Unique morphological characteristics, including well-developed pulvilli, wing vein 1A ending before the apex of cross vein mcu, basal transverse pale bands on abdominal terga, and two labial basal setae on the proboscis, confirmed species identity. Morphometric measurements included mean thoracic length (0.58±0.02) mm, thoracic width (0.63±0.02) mm, abdominal length (2.15±0.03) mm, abdominal width (0.61±0.01) mm, and wing length (2.91±0.02) mm. Molecular analysis corroborated the morphological identification, affirming the species as Cx. cinctellus. COI sequences of the collected specimen (452 bp) were confirmed as Cx. cinctellus for sequence identity by BLAST and BOLD analysis. These sequences were subsequently deposited in GenBank under the accession number OR225623.1. Conclusions: This study documents the first occurrence of Cx. cinctellus in Sri Lanka, highlighting the need to enhance entomological surveillance to monitor its dispersal and population dynamics.

The melon fly, Bactrocera cucurbitae, poses a severe threat to the country’s agricultural productivity, particularly in the cultivation of cucurbitaceous crops. This study was conducted to determine the ideal irradiation dose to be used to set up a Sterile Insect Technique (SIT)-based strategy to control B. cucurbitae outbreaks in Sri Lanka. A B. cucurbitae colony was established and maintained under standard laboratory conditions. Male pupae (100 pupae per treatment) were exposed to different radiation doses, namely 0 (control), 50, 60, 70, 80, 90, 100, and 110 Gy. The effect of irradiation on selected performance parameters such as survival, flight ability, fecundity, fertility, and adult longevity was evaluated under laboratory conditions. In addition, mating competitiveness was evaluated for irradiated male B. cucurbitae. Significant differences were observed in percentage pupal survival, flight ability, and fertility rates (p < 0.05) at a 95% level of confidence. Further, the 50% and 75% adult longevity periods of irradiated B. cucurbitae males significantly decreased with the increasing irradiation dosage (p < 0.05). B. cucurbitae exposed to 70 Gy radiation reported a mean pupal survival rate of 94.0 ± 1.25, flight ability of 93.3 ± 1.88, and fertility 0.2 ± 0.05%, along with a mean longevity of 38 ± 1.5 days until 50% reduction in the population. The competitiveness of B. cucurbitae exposed to 70 Gy with respect to wild males was 0.56 under laboratory conditions, which reduced up to 0.5 in semi-field settings. The 70 Gy dose could be recommended as the optimal radiation dose for the production of sterile B. cucurbitae males with an acceptable level of fitness and sterility to be used in SIT-based melon fly control programmes in Sri Lanka.

Dengue is an important mosquito-borne disease in Sri Lanka. The Sterile Insect Technique (SIT) is an environment-friendly and novel method that can suppress dengue vector mosquitoes in Sri Lanka. This study aimed to evaluate the field performance of sterile males and the density of wild male Aedes albopictus (Skuse) using a Mark–Release–Recapture (MRR) assay. Laboratory-colonized male pupae were exposed to 50 Gy gamma using a Co60 source. Sterile males (approx. 10,000) marked with fluorescent dust were released weekly for 4 consecutive weeks (January–February 2021) in a geographically isolated 30 ha site in Gampaha. Results show sterile males could disperse up to 543.8 m with a mean distance of 255.1 ± 44.6 m and survive up to 6 days with a mean life expectancy of 3.55 ± 2.32 days. A high field mating competitiveness of sterile males based on a Fried value of 0.47 ± 0.007 and significant induced sterility in the wild eggs in the second generation were found. The mean wild male mosquito population density was 163 males/ha. The data generated will be useful for designing future trials in Sri Lanka and other countries with similar situations.

BackgroundDespite the increasing usage of personal care products among young adolescents in Sri Lanka, limited studies have been conducted to understand the behaviour of cosmetic users and associated health complications. Therefore, the current study was conducted to evaluate the cosmetic consumption related behaviour of the undergraduate community in Sri Lanka and to identify the driving factors behind the incidences of cosmetic related adverse health effects.MethodAn analytical cross-sectional study was conducted by recruiting 421 undergraduates from five state universities in Sri Lanka through stratified random sampling, as the study population. Information on socio-demographic factors and cosmetic consumption behaviour of the participants were acquired through a self-administrated structured questionnaire, along with Knowledge, Attitudes and Practices (KAP) relevant for cosmetic usage. The Binary Logistic Regression model was used to determine the significant socio-demographic driving factors on cosmetic usage among the undergraduate community in Sri Lanka at a confidence level of 95%.ResultsAround 96.4% of the study population used one or more cosmetic products (77%) out of which, 75.3% experienced cosmetic related adverse health effects. Skin dryness (24%), acne (21%), allergies (20.5%) and rashes (19.8%), were identified as the most dominant adverse health effects, related to cosmetic usage. Perfumes (65.6%), face cream (63.2%) and body lotion/hand cream (60.6%), were the mostly used cosmetic products. Even though half of the study population exhibited higher levels of good practices during purchase (54.9%) and application (52%) of cosmetics, around 47.5% were characterized with a low level of knowledge on cosmetics. Gender, academic year, knowledge on cosmetics, monthly expenditure on cosmetics, source of recommendation for cosmetics, practices related to purchase and consumption of cosmetics and preference to receive medical care in case of cosmetic related emergency were recognized as significant risk factors (p < 0.05) associated with the incidence of cosmetic related adverse health effects among undergraduate students.ConclusionGiven the high prevalence of cosmetic related adverse health effects, the health authorities of Sri Lanka should pay more attention towards the wellbeing and responsible cosmetic usage among undergraduates. Designing of effective tools and regulations to monitor the cosmetic market and improving the knowledge on cosmetics are recommended to ensure safe cosmetic usage within the country in general and of adolescent users in particular.

BackgroundProper Healthcare Waste (HW) management is directly influenced by the knowledge and attitudes of Healthcare Professionals (HCP). However, studies that characterize the knowledge and practices of HCP on HW management are limited in Sri Lanka. This study was conducted to characterize the knowledge, perceptions and practices of HCP on the management of HW and to determine the risk factors influencing HW related occupational health hazards in the Colombo District of Sri Lanka.MethodsA total of 407 HCP were recruited as the study population from selected hospitals in the Colombo District. Information on socio-demographic factors, knowledge, attitudes and practices on HW management were gathered using an interviewer-administrated questionnaire. The Binary Logistic Regression (BLR) was used to determine the socio-economic risk factors associated with the occurrence of HW related health issues among the respondents.ResultsThe majority of respondents were characterized with a high knowledge level (76.9%) and positive attitudes (53.8%) on HW management. Incineration (82.6%) was recognized as the most widely used HW treatment method. Personal Protective Equipment (PPE) was used at a satisfactory level (85.5%), while liquid waste treatment was limited (57.5%). The occupational designation, level of training received in HW management, professional experience, vaccination status for tetanus, degree of knowledge and attitudes on HW management were recognized as significant risk factors (p < 0.05) associated with the occurrence of HW related occupational hazards.ConclusionEven though, the treatment of HW was satisfactory, strengthening the existing mechanisms for monitoring of HW management, provisioning more resources and organizing training and awareness programmes on HW management for HCP are recommended.

Dengue is recognized as one of the most common and rapidly spreading mosquito-borne viral disease, causing approximately 100 million infections annually around the world, also making a major challenge to the health sectors of Sri Lanka, due to the absence of a specific treatment or a vaccine. Hence health entities around the world rely upon vector control as the primary management strategy for dengue prevention. Regardless of the availability of diverse vector control strategies, unintentional ill effects on the environment and the fast development of insecticide resistance have hindered their success. Biological control of larval and adult stages of Aedes vector mosquitoes using locally available natural predators provides a cost-effective, sustainable, and environmentally friendly strategy for dengue vector control. The remarkable ecosystem diversity in Sri Lanka harbors a wide range of natural predators of Aedes , which range from microscopic copepods ( Mesocyclops leuckarti and Mesocyclops scrassus ) to macroscopic dragonflies ( Pantala flavescens and Anax indicus ) and fish ( Aplocheilus dayi, Aplocheilus parvus , and Puntius bimaculatus ). Ongoing research recommends aforementioned native species as excellent biological control agents of Aedes over some exotic species introduced for the same purpose, as a major contributing aspect in integrated vector management for dengue.

Dengue is a mosquito-borne viral disease mainly transmitted by Aedes aegypti and disease control is primarily reliant on mosquito vector control strategies. In the failure of conventional vector control strategies, new strategies are being developed which specifically require the maintenance of mosquito colonies in the laboratories. Blood-feeding is an essential part of the routine colony maintenance of Ae. aegypti. Therefore, the current study was focused on developing a simplified artificial membrane-feeding device, “Hemocup” feeder out of affordable material. viz., plastic cups, styrofoam insulation system, parafilm-M, and preheated water to facilitate the Ae. aegypti artificial blood feeding. The performance of the device was compared to that of a commercially available blood-feeding device, “Hemotek”, by assessing the blood-feeding rate, fecundity, and egg hatchability. Similar blood feeding rates were observed for Hemocup and Hemotek methods (91.8 ± 1.6 and 94.3 ± 1.6 respectively>0.05) as well as comparable fecundity between the two methods (20.8 ± 0.7 and 22.0 ± 1.5 respectively; p > 0.05). Furthermore, there was no statistically significant difference in egg hatchability between the two methods (91.9 ± 1.4 and 93.8 ± 1.4, respectively; p > 0.05). The results indicate that this simple Hemocup blood-feeding system can be used for routine colonization of laboratory strains of Ae. aegypti and for mass-rearing purposes.

Background The Sterile Insect Technique (SIT) is presently being tested to control dengue in several countries. SIT aims to cause the decline of the target insect population through the release of a sufficient number of sterilized male insects. This induces sterility in the female population, as females that mate with sterilized males produce no offspring. Male insects are sterilized through the use of ionizing irradiation. This study aimed to evaluate variable parameters that may affect irradiation in mosquito pupae. Methods An Ae. aegypti colony was maintained under standard laboratory conditions. Male and female Ae. aegypti pupae were separated using a Fay and Morlan glass sorter and exposed to different doses of gamma radiation (40, 50, 60, 70 and 80 Gy) using a Co60 source. The effects of radiation on survival, flight ability and the reproductive capacity of Ae. aegypti were evaluated under laboratory conditions. In addition, mating competitiveness was evaluated for irradiated male Ae. aegypti mosquitoes to be used for future SIT programmes in Sri Lanka. Results Survival of irradiated pupae was reduced by irradiation in a dose-dependent manner but it was invariably greater than 90% in control, 40, 50, 60, 70 Gy in both male and female Ae. aegypti. Irradiation didn’t show any significant adverse effects on flight ability of male and female mosquitoes, which consistently exceeded 90%. A similar number of eggs per female was observed between the non-irradiated groups and the irradiated groups for both irradiated males and females. Egg hatch rates were significantly lower when an irradiation dose above 50 Gy was used as compared to 40 Gy in both males and females. Irradiation at higher doses significantly reduced male and female survival when compared to the non-irradiated Ae. aegypti mosquitoes. Competitiveness index (C) scores of sterile and non-sterile males compared with non-irradiated male mosquitoes under laboratory and semi-field conditions were 0.56 and 0.51 respectively at 50 Gy. Signification Based on the results obtained from the current study, a 50 Gy dose was selected as the optimal radiation dose for the production of sterile Ae. aegypti males for future SIT-based dengue control programmes aiming at the suppression of Ae. aegypti populations in Sri Lanka.

This study was conducted to evaluate the potential of six locally abundant fish species to control Aedes mosquito larvae and thereby manage dengue epidemics in a sustainable, cost-effective and environmentally friendly manner. The biocontrol efficacy of six larvivorous fish species, namely, Poecilia reticulata, Rasbora daniconius, Aplocheilus dayi, Oriochromis mossambicus, O. niloticus and Puntius bimaculatus, was evaluated under laboratory and field conditions. Five size-matched fish (of the same species) were introduced into separate tanks (replicates) containing 2 L of dechlorinated water and 200 third instar larvae of Aedes aegypti (L.). The number of larvae consumed by each fish species was recorded at three-hour intervals for 24 h. Acclimatized fish were introduced into a total of eighteen artificial breeding habitats located in the Gampola Medical Officer of Health (MOH) area at the species level with three replications. In addition, three breeding sites without fish were monitored as controls. Aedes larvae were monitored by dipping and siphoning methods in each breeding habitat at weekly intervals for three months and the number of fish surviving in each habitat was tallied. Over 24 h under laboratory conditions, O. mossambicus showed the highest predation rate, consuming 320.2 +/- 14.5 larvae per day, with a predatory efficiency of 87.5 +/- 3.5%. In comparison, O. niloticus consumed 264.6 +/- 12.2 larvae per day with consumption efficiciency of 78.1 +/- 3.7%, whereas R. daniconius had the lowest larval consumption (33.2 +/- 2.7 larvae per day) and predatory efficiency (33.2 +/- 3.2%). Over 12 weeks of observation under field conditions, breeding sites with Ap. dayi had the lowest Aedes larval counts, followed by Po. reticulata. Considering predation efficiency and survival under field conditions, Ap. dayi and Po. reticulata were considered to be the best potential candidates for biological control of Ae. aegypti. Further studies under field settings are warranted to evaluate the survival and predatory potential of the selected candidates under more varied environmental conditions.

Background. Pyrethroid insecticides are widely used in many countries for chemical-based control of Ae. aegypti. Regardless of their efficacy, the constant use of insecticides has induced insecticide resistance mechanisms, such as knockdown resistance (kdr) in mosquitoes. Sri Lankan Vector Controlling Entities (VCE) have been using a variety of pyrethroid insecticides as the primary approach for dengue control. However, development of any resistance among the Aedes mosquitoes has been limitedly studied in the country. Therefore, the current study was conducted to evaluate the prevalence of F1534C, V1016G, and S989P mutations among Ae. aegypti mosquito populations in three dengue endemic high-risk regions of Sri Lanka. Methodology. Immature (both pupae and larvae) stages of Ae. aegypti mosquitoes were collected from Colombo, Gampaha, and Kandy districts of Sri Lanka from February 2018 to December 2019. Polymerase Chain Reaction- (PCR-) based assay for molecular genotyping of mutations was performed to identify the prevalence of kdr mutations in collected Ae. aegypti populations, separately. The frequencies of the resistant and susceptible kdr alleles were determined by using the Hardy-Weinberg equilibrium. Results. The Ae. aegypti populations from Colombo, Gampaha, and Kandy districts showed 46%, 42%, and 22% of F1534C mutation allele frequencies, along with 15%, 12%, and 6% of V1016G mutation allele frequencies, respectively. The mutation allele frequencies of S989 in Colombo, Gampaha, and Kandy districts were 9.5%, 8.5%, and 4.5%, respectively. The wild-type (PP) genotype remained predominant within all the three districts, whereas the homogenous (QQ) mutation genotype occurred only in minority. The abundance of Q allele frequency in Ae. aegypti mosquitoes was relatively higher for all the three mutations in Colombo. Conclusions. The findings clearly indicate that long-term insecticide applications and multiple use of pyrethroids have led to the acquisition of kdr mutations, leading to the development of insecticide resistance among local Ae. aegypti populations, especially in the Colombo and Gampaha districts. Therefore, evaluation of the prevalence levels of these kdr mutations highlights the necessity for shifting towards novel vector control strategies.

Background: Mosquitoes borne diseases have become a major health issue in Sri Lanka. Regardless of the high diversity of medically important mosquitoes, in depth studies that attempt to investigate their diversity and abundance are limited in Sri Lanka. Lentic water bodies that are largely associated with lotic aquatic systems such as rock pools, sand pools, mud pools, provide ideal breeding grounds for such mosquitoes, aggravating the risk imposed by such vectors. Therefore, the current study evaluated the diversity and abundance of medically important mosquitoes, which is of paramount importance for successful vector control programs. Methods and materials: The present study was conducted at 20 sentinel sites located in the Daduru Oya river basin located in the District of Kurunagala from November, 2018 to April, 2019. Different medically important mosquitoes present in potential lentic water habitats were collected using standard dipping and siphoning methods at monthly intervals. Collected larvae were microscopically identified using taxonomic keys. Results: A total of 158 rock pools and sand pools were monitored along the river basins. A total of 542 larvae belonging to four genera, namely, Aedes (10.68%), Anopheles (53.84%), Culex (34.33%) and Aedeomyia (1.15%) were found in the river basin. An. culicifacies (35.60%), the primary vector malaria in Sri Lanka, was the most prominent mosquito species, followed by Cu. gelidus (23.80%), a major vector of Japanese encephalitis. Cu. quinquefasciatus (9.04%), the vector of Filarisis and Cu. tritaeniorhynchus (2.76%), Cu. pseudovishnui (2.58%) and Cu. vishnui (4.42%) which are considered as major vectors of Japanese encephalitis were also found as medically important vectors. Relatively lower levels of Aedes vittatus (1.29%) and Aedeomyia catasticta (35.60%) were recorded from rock pools, which are not of any proven medical importance in Sri Lanka. The abundance of mosquito species differed significantly throughout the study period (p < 0.05 at 95% level of confidence) as suggested by the statistics of Chi square test. Conclusion: A higher abundance level of medically important vector mosquitoes were found during the study, suggesting that routine entomological surveillance is important especially since the primary vectors of malaria, Japanese encephalitis and Filarisis were recorded.

Background. Aedes aegypti is a major vector of arboviruses that may be controlled on an area-wide basis, using novel approaches such as Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT). Larval diet is a critical factor to be considered in mass rearing of Aedes mosquitoes for SIT and IIT programs. Therefore, the current study is aimed at evaluating the effects of two novel diets developed from dry fish powder on the growth and development of immature stages and adult fitness-related characteristics of Ae. aegypti in Sri Lanka. Method. Three batches of the first instar Ae. aegypti larva, each containing 250 larvae, were exposed to three different larval diets as standard dry fish powder (D1), dry fish powder meal and brewer’s yeast (D2), and International Atomic Energy Agency- (IAEA-) recommended diet (D3), separately. Morphometric and developmental parameters of the 4th instar larvae, pupae, and adult mosquitoes reared under different dietary treatments were measured. The entire experimental setup was replicated thrice. A General Linear Model (GLM) in the form of two-way ANOVA was used for the statistical analysis. Results. Significant diet-based variations were observed in the head length, head width, thoracic length, thoracic width, abdominal length, abdominal width, and total length ( F2,87>4.811 ; P<0.05 ) of Ae. aegypti larvae. The highest pupation success and the larval size were observed from the larvae fed the D2 diet, while the lowest was reported from D1. All adult morphometric parameters of adult male and female Ae. aegypti mosquitoes also denoted significant dietary variations, reporting the best-sized adults from the D2 diet ( F2,87>3.54 ; P<0.05 ). Further, significantly higher fecundity and male longevity were also shown by the adult Ae. aegypti ( F2,6>7.897 ; P<0.01 ) mosquitoes reared under diet D2. Conclusion. Based on all the growth and developmental parameters, the D2 diet tends to perform similar to the IAEA-recommended diet in mass rearing of Ae. aegypti mosquitoes, while being more inexpensive. Therefore, larval diet D2 could be suggested as the ideal diet for mass rearing of Ae. aegypti for IIT and SIT-based vector control in Sri Lanka.

Background & objectives: Understanding the effect of biotic and abiotic factors on the biology and ecology of immature stages of anopheline larvae is very important in controlling malaria vector mosquitoes. Therefore, this study was focused on the monitoring of ecological factors affecting the distribution, dynamics, and density of malaria vector mosquitoes in the District of Trincomalee, Sri Lanka. Methods: Permanent and temporary breeding habitats were identified and selected from five possible malaria sensitive sites in the district of Trincomalee. Anopheles larvae and macro-invertebrates were collected using standard methods for 16 months (from October 2013 to January 2015) and they were identified microscopically. Eight physico-chemical parameters of the breeding habitats were measured. Results: Overall, a total of 4815 anopheline larvae belonging to 13 species were collected from 3,12,764 dips from 18 permanent and temporary breeding habitats. The abundance of anopheline larvae showed a significant positive correlation (p <0.05) with physico-chemical parameters in breeding habitats, such as temperature, dissolved oxygen, and turbidity. A total of 35 macro-invertebrate taxa were collected from the anopheline mosquito breeding habitats. Interpretation & conclusion: This study represents the first systematic update of water quality parameters, macro-invertebrate communities associated with Anopheles mosquito oviposition sites in the District of Trincomalee, Sri Lanka. Rainfall intensity and wind speed are critical meteorological factors for the distribution and abundance of malaria vectors. Knowledge generated on the ecology of Anopheles mosquitoes will help to eliminate malaria vectors in the country.

Many countries are in search of more effective and sustainable methods for controlling dengue vectors, due to undeniable inefficiencies in chemical and mechanical vector control methods. Bio-control of vectors by copepods is an ideal method of using interactions in the natural ecosystem for vector management, with minimum consequences on the environment. Current study determined the predatory efficacy of five locally abundant copepod species on, Aedes larvae under laboratory conditions. Copepods were collected from the pre-identified locations within the districts of Gampaha and Kandy, and identified morphologically. Individual species of copepods were maintained as separate colonies with Paramecium culture and wheat grain as supplementary food. Five adult copepods of each species was introduced into separate containers with 200 larvae (1st instar) of Aedes aegypti. Number of larvae survived in containers were enumerated at 3 hour intervals within a duration of 24 hours. Each experiment was repeated five times. The same procedure was followed for Ae. albopictus. Significance in the variations among predation rates was evaluated with General Linear Modelling (GLM) followed by Tukey’s pair-wise comparison in SPSS (version 23). Significant variations in predation rates of studied copepod species were reported (p<0.05), whereby M. leuckarti indicated the highest followed by M. scrassus, while C. languides indicated the lowest predatory efficacy. The effect of different Aedes larval species on the predation rates of copepods remained significant (p<0.05), even though the effect on predatory efficiency was not significant. Based on the findings, both M. leuckarti and M. scrassus, with the highest predatory efficiencies, could be recommended as potential candidates for biological controlling of Aedes vectors in Sri Lanka.

[This corrects the article DOI: 10.1155/2018/8759459.].

BackgroundSex separation of mosquitoes at different stages is currently being attempted to ensure the successful release of male mosquitoes in novel vector control approaches. Mechanical and behavioral techniques have been tried most frequently.MethodsBatches of (n=300) Aedes aegypti and Ae. albopictus pupae were used for standard sieving (using sieves with 1.12, 1.25, 1.40 and 1.60mm mesh sizes) and the Fay-Morlan glass plate separation methods. Male and female separation by each method was calculated. For behavioral separation, a spiked blood meal with different concentrations (0, 2, 4, 6, 8 and 10ppm) of ivermectin and spinosad (spinosyn, 12%w/v), were provided to a batch (n=300) of adult Ae. aegypti and Ae. albopictus (1:1 sex ratio) followed by observation of mortality. An additional double feeding method involved provision of a further blood meal after 24h, with the same concentrations of ivermectin and spinosad as the initial feeding, followed by a 48-h observation of mortality. All experiments were repeated five times.ResultsIn the standard sieving method, the percentage of males and females separated at different pore sizes differed significantly (P<0.05). The majority of the male pupae were collected in the 1.12 mm pore sized sieve for both Ae. aegypti (73%) and Ae. albopictus (69%) while females were retained mainly in the sieve with the pore size of 1.25mm. In the Fay-Morlan glass plate separation, 99.0% of the Ae. aegypti and 99.2% of the Ae. albopictus introduced male pupae could be separated, but with female contaminations of 16 and 12%, respectively. Provision of a blood meal spiked with 8ppm of ivermectin under the double feeding was identified as the most effective way of achieving 100% female elimination for both Aedes species.ConclusionsWith 100% separation, use of a spiked blood meal is a more effective method of sex separation than the mechanical methods. Application of the spiked blood meal approach as a second separation level for sexes, after applying the Fay-Morlan glass plate method, could achieve 100% sex separation of sexes whilst allowing a reduction in the amount of toxicants required.

Background & objectives: Although malaria is eliminated from Sri Lanka, there is a possible risk of spread from infected persons coming from malaria endemic countries. The presence of major and potential vectors in several parts of the country along with drug resistance, necessitates the identification of effective and novel control methods. The present study focused on identifying effective biological control agents for anopheline larvae using carnivorous copepods under laboratory and field conditions to prevent re-introduction of malaria in the country. Methods: Three copepod species, namely Mesocyclops scrassus, Cyclops varicans and C. languides collected from different areas in the country were cultured by adding supplementary food, and their predatory efficacy was evaluated under laboratory and field conditions. Results: Significant variation (p <0.05) was observed in predation rates of studied copepod species. The species M. scrassus showed the highest predacious efficiency, and consumed the highest number of anopheline larvae under laboratory and field conditions. Further, M. scrassus had higher survival rate than C. varicans and C. languides. Interpretation & conclusion: The results of the study suggest that the predatory copepod M. scrassus can be used as a bio-control agent for the control of Anopheles mosquitoes to prevent re-emergence of malaria in the country. Additional research is suggested to identify naturally available copepod species and their predatory efficacy.