Browsing by Author "Nayakarathna, N.M.N.G."

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Effect of The Domestic Characteristic on Colonization of Phlebotomine Sand Flies: A Case Study in Anuradhapura District, Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Ganehiarachchi, G.A.S.M.; Rajapakse, R.P.V.J.; Jayanetti, S.R.
Cutaneous Leishmaniasis (CL)is an endemic vector-borne disease in Sri Lanka.It is caused by protozoan parasite Leishmania species and transmitted via infective bite of female Phlebotomine sand flies (Diptera: Psychodidae). The public health importance of this disease is positively increasing due to inadequate knowledge of vector biology. The current study is an attempt to uncover the vector biological aspects, focusing on the successful vector control interventions. This study was carried out in Anuradhapura district, Sri Lanka; a district with high disease prevalence of CL. Three sampling localities were selected; Thalawa, Padawiya and Wijayapura. A questioner and field studies were carried out in the sampling areas among CL patients to assess the effect of domestic environment characteristics on colonization of phlebotomine sand flies. Presence of decaying garbage, termite hills, manna grass (Glyceria sp.), water streams, unclear areas, wet soil areas, scrub jungles and gardening areas are the concerned characteristics for the present study. Field studies were conducted every month for seven months continuously. In every visit, Phlebotomine sand fly samples were collected from the study sites mentioned above using yellow sticky trap method. Increment of the mean number of sand fly population alongwith the increment of the number of domestic characteristics was tested with the regression analysis.With the increment of supportive environmental characteristics, sand fly populations were increased linearly (P = 0.000) in each site. This relationship revealed that the maximum sand fly populations were recorded in the places with all the tested characteristics stated above. Accordingly, the surrounding characteristics of the domestic environment have a significant effect on the colonization of sand fly populations. Domestic characteristics such as decaying organic matter, wet soil, unclear areas and water streams around the living environment show higher contribution to the colonization of sand flies. In conclusion, characteristics of the domestic environments have effect on the colonization of sand flies. Increment of the supportive domestic characters intensifies the colonization of sand flies.
Gape size of wild guppy (Poecilia reticulata): Does it matter in mosquito larval control?
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Weerakoon, S.N.; Ganehiarachchi, G.A.S.M.
Larvivorous fish is very important tool in controlling disease transmitting vector mosquitoes in many parts of the world. However, there is a lacuna of knowledge about the vector control potency in relation to the gape size of these fish. Since the wild guppy, Poecilia reticulata; is a topmost larvivorous fish, the current study was performed to study the effect of gape size of guppy in controlling mosquito larvae. For the current study, wild guppies were collected from their own natural habitats located around the Kelaniya area. In the laboratory, measurements of total length (TL) and Gape Size (GS) of individual specimens were obtained. These fish were then grouped in to ten length classes of 0.2 cm intervals ranging from 0.8 to 2.8 cm. For each length class of fish, 5L capacity glass tank was assigned. Accordingly, there were 10 experimental tanks for 10 size classes of fish, and for each tank assigned for a particular size class, 10 fishes were introduced. After acclimatization, fish were kept without food for 24 hours. In the meantime, laboratory reared mosquito larvae were collected and separated according to their instar level. Four instar stages of larval and the pupal stage were used for investigating of prey selection by P. reticulata. The rationale used here was that all the immature stages of mosquitoes were separately exposed to each length class of fish to determine the mosquito larval/pupal mortalities. Ten mosquito larvae/pupa form a particular instar were introduced to a fish tank at a time. Subsequently, the mortality rates of mosquito larvae/pupa in each tank were determined after 24 hours. All the fish were kept under 24 hour fasting period prior to each experimental cycle. In the next experimental cycle, ten mosquito larvae/pupa form a particular instar were introduced to another fish tank. This procedure was continued until all the instar/pupal stages expose to all the fish tanks. Relationship between TL and GS was tested with a Pearson correlation and with linear regression analysis. One way – ANOVA was performed to analyse the significance of the mortality of different instars along in different length classes. The results revealed that the relationship between TL and GS is best fitted for liner regression model (R2 = 0.80) with the equation; GS = 0.1 TL – 0.02. The 24 hour percentage mortality of different mosquito instars indicated that the 1st and 2nd mosquito larval instars were vulnerable to all the length classes tested for these instars (GS range = 0.06 – 0.26 cm). Fishes of 0.8 – 1.0 cm length class (GS range = 0.06 – 0.08 cm) were unable to consume 3rd instar mosquito larvae. Fishes of 0.8 – 1.2 cm length range (GS range = 0.06 – 0.1 cm) were unable to consume 4th instar larvae. Pupae were consumed by the fishes whose length range was 1.4 – 2.8 cm (GS range = 0.12 – 0.26 cm). Hence, the gape size of the guppy fish has a significant effect on the mosquito larval controlling and the fishes with GS > 0.12 cm (TL > 1.4 cm) are excellent in controlling the pupae and all the instars of mosquito larvae.
Influence of humidity and temperature variation of natural breeding sites on abundance of Leishmaniasis vector Phlebotomus argentipes population in Anuradhapura District
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Ganehiarachchi, G.A.S.M.; Rajapakse, R.P.V.J.; Jayanetti, S.R.
Cutaneous leishmaniasis (CL) is an endemic public health problem in Sri Lanka. Leishmania donovani is the suspected causative agent of the disease and this parasite is transmitted by a dipteran fly species; Phlebotomus argentipes. Studies on vector behavioral and ecological aspects, although important for better understanding of disease transmission, are still limited. The present study is an attempt to uncover the vector ecological aspects focusing on the successful vector control interventions. This study is being carried out in Anuradhapura district, Sri Lanka; where there is a high disease prevalence of CL. Three sampling sites; Thalawa, Wijayapura and Padawiya were selected. Adult sand flies were collected monthly over a six months duration using CDC light traps (5) and yellow sticky traps (30). In the meantime, relative humidity and air temperature were measured using hygrometer and thermometer in each site. The collected sand flies were identified up to the species level using standard keys. Percentage composition of each of the species was calculated. Temporal variations of primary vector, Phlebotomus argentipes along with the dynamics of temperature and relative humidity was determined using regression analysis. Phlebotomus argentipes was the dominant sand fly species found in the study sites. The percentage composition of the primary vector exhibited a variation during the study period and maximum percentage composition was recorded during May and June, 2016. The relationship between percentage composition of Ph.argentipes versus mean temperature was significant (P = 0.000, R2 = 97.7%) and elevated percentage composition were recorded under lower temperature. Further, percentage composition of Ph.argentipes exhibited an increasing trend with higher humidity levels (P = 0.000, R2= 98.4%). In conclusion, the primary vector populations of leishmaniasis are increased with lower temperature and higher humidity. As such, this relationship will helpful to predict the variation of vector population with the changes of ecological parameters and finally a successful vector management strategy can be implemented with the thorough knowledge of its life history parameters and behavioral pattern.
Leishmaniasis: a vector- born disease in Sri Lanka: past, current and future
(Gloria Scientiam – Golden Jubilee Commemorative Volume, Faculty of Science, University of Kelaniya, 2017) Ganehiarachchi, G.A.S.M; Nayakarathna, N.M.N.G.; Rajapakse, R.P.V.J.
Leishmaniasis is caused by a protozoan parasite Leishmania species and is transmitted to humans by the bite of infected female phlebotomine (Diptera: Psychodidae) sand flies. There are three main forms of Leishmaniasis; Cutaneous Leishmaniasis, Muco-Cutaneous Leishmaniasis and Visceral Leishmaniasis. At present, Cutaneous Leishmaniasis is established in Sri Lanka. The parasite in this country is Leishmania donovani MON 37 and the prevalent vector is Phlebotomus argentipes. Environmental factors including temperature, humidity and rainfall influence the abundance and distribution of sand flies. Socio-economic conditions, population mobility, environmental and climate changes are the main risk factors of the spread of Leishmaniasis. Early detection of the disease and treatment, vector management and health education are the main control strategies for the control of the disease. It is a timely need to control the disease transmission before more virulent strains are established in the country. To resolve the epidemiology of Leishmaniasis further studies on the parasitic aspects and entomological studies of vector aspects are most important. Harmonizing with these biological phenomena, continuous surveillance, improving case detection programs at the community level and implementing management protocols and control activities are necessary to eliminate Leishmanisis in Sri Lanka
Socio-economic and ecological impacts on dispersal of cutaneous leishmaniasis in North Central Province, Sri Lanka
(International Journal of Tropical Insect Science, 2022) Nayakarathna, N.M.N.G.; Jayatunga, D.P.W.; Ganehiarachchi, G.A.S.M.
Leishmaniasis is a fatal disease caused by a parasitic protist of the genus Leishmania through the infected primary vectors, Phlebotomine (Diptera: Psychodidae) female sand flies. In Sri Lanka, cutaneous leishmaniasis (CL) is established in Anuradhapura district. The present study was carried out to determine the socio-economic and environmental factors on the distribution of CL. A survey was conducted among CL patients on selected demographic and socio-economic factors and environmental characteristics at three study localities throughout a year. Phlebotomine sand flies were collected using sticky traps and Centers for Disease Control (CDC) light traps around residences of CL patients. Significant differences were shown between mean abundance of primary vectors and different environmental characteristics. The sand flies were reported to gather in shrubs, jungle areas, gardening areas, wet soil areas, leaf litter and around termite hills. The data obtained showed poor knowledge and lack of awareness about leishmaniasis among the local communities. Therefore, it is paramount to conduct awareness programs on leishmaniasis transmission, potential risk factors, sand fly vector of the disease, preventing the sand fly bites and how domestic surrounding areas must be managed for reducing vector populations to prevent disease spreading among local community.