ABSTRACT
To assess the larvicidal activity of mangosteen (Garcinia mangostana) against larval stages of Aedes aegypti mosquitoes. Methods: A crude extract was prepared in ethanol from powdered mangosteen pericarps. A concentration gradient (0.01-4.92 g/ L) was prepared from the stock solution. Seven batches of 25 third instar larvae of Aedes aegypti were used for larval bioassays. Larval mortality rates were observed after one and 24 hours. Cholesterol and total lipid contents in 20 randomly selected dead larvae at each trial were assessed by colorimetric method. The experimental setup was repeated five times. The General Linear Model and Probit analysis were used to evaluate the relationship of mortality with cholesterol level, total lipid level and cholesterol to total lipid ratio. Results: The percentage mortalities significantly varied with different concentrations (F7,32=385.737; P<0.001). The LC50 and LC99 values were (0.041 0.006) g/L and (10.616 1.758) g/ L, respectively after 24 hours. There was no mortality recorded within the one-hour exposure time. Only the cholesterol content (F5,24=173.245; P<0.001) in larvae exposed to different concentrations denoted a significantly decreasing trend within 24- hour exposure. Larvae that were exposed to the lowest concentration (0.55 g/L) showed a higher cholesterol level (22.67 1.33) g. Conclusions: The Garcinia mangostana extract acts as an effective sterol carrier protein inhibitor that inhibits cholesterol uptake in Aedes aegypti mosquitoes. Hence, it could be explored for use as a key source for the development of an environment-friendly plantbased larvicide.
ABSTRACT
Objective: To assess public knowledge, practices and perceptions on typhus fevers in Sri Lanka. Methods: A descriptive study was done in four selected typhus-prone areas in Southern Sri Lanka. A mixed-method was employed using face-to-face interviews and questionnaire-based surveys among confirmed cases of typhus and at-risk populations, respectively. Frequencies, percentages, and means were used to characterize socio-demography and evaluate disease awareness. Results: The lay terms for typhus fevers reported in the studied region were 'peacock fever', 'tick fever' and 'bird fever'. A total of 499 subjects participated [mean±SD, (45±16) years] in the questionnaire-based survey, and 13.6% (n=68) reported past experience of typhus fever, 1.2% (n=6) identified the disease as 'typhus' while 58.7% (n=293) and 11.8% (n=59) knew it as 'peacock fever' and 'tick fever', respectively. The etiological agent was unknown to 95.2% (n=475), but 53.5% ((n=267) were aware that it was vector-borne. Fever (57.3%, n=286), eschar (35.7%, n=178), headache (22.0%, n=267) and myalgia (19.2%, n=96) were identified as key symptoms. Past disease experience was significantly associated with higher awareness of the main disease symptoms (fever: χ 2 =15.713, P<0.001; headache: χ 2 =19.447, P<0.001; lymphadenopathy: Fisher's exact test, P=0.023; eschar: χ 2 =12.049, P<0.001). None knew of any disease prevention methods. Participants with a past history of typhus fever had sought treatment at state hospitals (55.9%, 38/68) and private sector hospitals (5.9%, 4/68). Conclusions: Public awareness on preventive practices for typhus fevers was rare among the participants though vector-borne aspect was known to many. Clinical disease awareness was deficient among those without past experience of typhus fever. Community sensitization on vector avoidance strategies is highly recommended.
ABSTRACT
To assess the larvicidal activity of mangosteen (Garcinia mangostana) against larval stages of Aedes aegypti mosquitoes. Methods: A crude extract was prepared in ethanol from powdered mangosteen pericarps. A concentration gradient (0.01-4.92 g/ L) was prepared from the stock solution. Seven batches of 25 third instar larvae of Aedes aegypti were used for larval bioassays. Larval mortality rates were observed after one and 24 hours. Cholesterol and total lipid contents in 20 randomly selected dead larvae at each trial were assessed by colorimetric method. The experimental setup was repeated five times. The General Linear Model and Probit analysis were used to evaluate the relationship of mortality with cholesterol level, total lipid level and cholesterol to total lipid ratio. Results: The percentage mortalities significantly varied with different concentrations (F7,32=385.737; P<0.001). The LC50 and LC99 values were (0.041 0.006) g/L and (10.616 1.758) g/ L, respectively after 24 hours. There was no mortality recorded within the one-hour exposure time. Only the cholesterol content (F5,24=173.245; P<0.001) in larvae exposed to different concentrations denoted a significantly decreasing trend within 24- hour exposure. Larvae that were exposed to the lowest concentration (0.55 g/L) showed a higher cholesterol level (22.67 1.33) g. Conclusions: The Garcinia mangostana extract acts as an effective sterol carrier protein inhibitor that inhibits cholesterol uptake in Aedes aegypti mosquitoes. Hence, it could be explored for use as a key source for the development of an environment-friendly plantbased larvicide.
ABSTRACT
Objective: To assess public knowledge, practices and perceptions on typhus fevers in Sri Lanka. Methods: A descriptive study was done in four selected typhus-prone areas in Southern Sri Lanka. A mixed-method was employed using face-to-face interviews and questionnaire-based surveys among confirmed cases of typhus and at-risk populations, respectively. Frequencies, percentages, and means were used to characterize socio-demography and evaluate disease awareness. Results: The lay terms for typhus fevers reported in the studied region were 'peacock fever', 'tick fever' and 'bird fever'. A total of 499 subjects participated [mean±SD, (45±16) years] in the questionnaire-based survey, and 13.6% (n=68) reported past experience of typhus fever, 1.2% (n=6) identified the disease as 'typhus' while 58.7% (n=293) and 11.8% (n=59) knew it as 'peacock fever' and 'tick fever', respectively. The etiological agent was unknown to 95.2% (n=475), but 53.5% ((n=267) were aware that it was vector-borne. Fever (57.3%, n=286), eschar (35.7%, n=178), headache (22.0%, n=267) and myalgia (19.2%, n=96) were identified as key symptoms. Past disease experience was significantly associated with higher awareness of the main disease symptoms (fever: χ 2 =15.713, P<0.001; headache: χ 2 =19.447, P<0.001; lymphadenopathy: Fisher's exact test, P=0.023; eschar: χ 2 =12.049, P<0.001). None knew of any disease prevention methods. Participants with a past history of typhus fever had sought treatment at state hospitals (55.9%, 38/68) and private sector hospitals (5.9%, 4/68). Conclusions: Public awareness on preventive practices for typhus fevers was rare among the participants though vector-borne aspect was known to many. Clinical disease awareness was deficient among those without past experience of typhus fever. Community sensitization on vector avoidance strategies is highly recommended.
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Objective: To identity the variation of sand flies in the Gampaha and Kurunegala districts of Sri Lanka and to assess DNA barcoding as a complementing method for morphological identification. Methods: A total of 38 441 sand flies were collected from selected localities in Gampaha and Kurunegala districts using standard entomological techniques from May 2017 to December 2018. Specimens were identified using morphological features and compared with mitochondrial cytochrome C oxidase subunit I gene- based DNA barcoding as an alternative tool. Results: Morphological and molecular identification confirmed the presence of four species under two genera (Phlebotomus and Sergentomyia). Phlebotomus argentipes was the predominant species, followed by Sergentomyia (S.) punjabensis, S. babu insularis, and an unidentified Sergentomyia sp. Phlebotomus argentipes showed a clear genetic differentiation from other species. S. babu insularis and S. punjabensis showed a higher genetic affinity to each other than the unidentified species. The unidentified Sergentomyia species is morphologically similar to S. zeylanica, but differs only in clavate gonostyle. Conclusions: DNA barcoding is an effective technique for the identification of sand flies. Further studies using molecular techniques will improve the knowledge of the cryptic diversity of Sri Lankan sand fly fauna. Establishing a reliable and standardized identification system for sand fly species in Sri Lanka is recommended.
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Objective: To compare the DNA sequences of Leishmania (L.)donovani isolated from individuals in two districts of the Northern Province with other parts of Sri Lanka and neighboring countries. Methods: Samples were collected from military personnel at the Army Hospital, Narahenpita, Sri Lanka from November 2018 to March 2020. A portion of the samples was fixed, stained with Giemsa and observed under the light microscope. The genomic The DNA was extracted from the remaining portion of the samples using DNEasy blood tissue kit (Qiagen, Germany) and amplified using Leishmania genus-specific primers for molecular diagnosis initially. DNA was amplified using L. donovani species-specific primers by PCR and the amplified product was sequenced for comparison of nucleotide sequences. Results: Out of 76 suspected patients, at least one biological sample of 45 (59.2%) was positive for L. amastigotes upon microscopy. Overall, 33 (43.4%) were positive in Leishmania genus-specific PCR, but only 23 (30.3%) were positive in L. donovani specific PCR. The dendrogram indicates that the current sequences clustered together with those from Nepal and Gampaha districts (Western Province), Sri Lanka, while the Indian and Eastern African sequences clustered separately. Conclusions: The genetic diversity was low among the isolates, indicating a single and possibly a local point of origin. However, the similarity of Sri Lankan and Nepal strains indicate a possibility of a shared point of origin, which needs more extensive evidence to confirm.
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Objective: To revise morphological identification keys to the anophelines in Sri Lanka.Method:country. Stage III and IV larvae were identified under a light microscope with an objective (í10) using standard larval keys developed for Sri Lankan anophelines. Key larval characters were recorded for each species based on original observations and previous usage in literature.Results:Samples were collected from selected entomological sites in different districts in the which are currently recognized as local anopheline species in Sri Lanka, as a guide to workers engaged in malaria surveillance and control in the country.Conclusions:Revised morphological keys to the larval of these species may be helpful in easy This manuscript describes an illustrated key for the identification of 22 of 23 mosquitoes and accurate identification at the field level.
ABSTRACT
<p><b>OBJECTIVE</b>To revise morphological identification keys to the anophelines in Sri Lanka.</p><p><b>METHOD</b>Samples were collected from selected entomological sites in different districts in the country. Stage III and IV larvae were identified under a light microscope with an objective (×10) using standard larval keys developed for Sri Lankan anophelines. Key larval characters were recorded for each species based on original observations and previous usage in literature.</p><p><b>RESULTS</b>This manuscript describes an illustrated key for the identification of 22 of 23 mosquitoes which are currently recognized as local anopheline species in Sri Lanka, as a guide to workers engaged in malaria surveillance and control in the country.</p><p><b>CONCLUSIONS</b>Revised morphological keys to the larval of these species may be helpful in easy and accurate identification at the field level.</p>