Medicine
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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
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Item Abundance and taxonomic characterization of chigger mites (Acari: Trombiculidae and Walchiidae) associated with rodents in selected scrub typhus-prone areas in Southern and Western provinces of Sri Lanka(University of Kelaniya, 2024) Liyanage, A.; Gunathilaka, N.; Premarathne, R.; Chandrasena, N.; Jacinavicius, F.D.C.; Silva, R.B.Larval trombiculid mites (chiggers) are the vectors and reservoirs of the potentially lethal infectious disease, scrub typhus (ST) caused by Orientia tsutsugamushi. Small rodents are natural hosts of parasitic larval stage of the chigger mites. This study focused on determining the abundance of chigger mites associated with rodents in Sri Lanka and the taxonomic characterization of field-caught chiggers. Field sampling was conducted in the districts of Galle, and Hambantota of the Southern Province, and Gampaha of the Western Province, in 2019 and 2020. Sampling sites were selected according to the patient distribution. Rodents were captured using baited traps (7.62 cm x 7.62 cm x 25.4 cm) set up just before sunset at peri-domestic or work premises of ST fever patients. A total of 422 traps were placed at identified possible exposure locations in Galle (n=122), Hambantota (n=120) and Gampaha (n=178). A total of 58 small mammals were captured [Galle (n=19), Hambantota (n=7), and Gampaha (n=32)] under three small rodent species, namely; Rattus rattus (Black rat), Rattus norvegicus (Brown rat), Tatera indica (Indian gerbil), Gollunda ellioti (Indian bush rat) and Suncus murinus (Asian house shrew). The trapped rodents were anaesthetized with ketamine (75 mg/kg) /xylazine (10 mg/kg) and examined for larval mites. Mites detected were removed carefully with a brush, collected, and washed individually with 10% PBS and slidemounted in Hoyer’s medium. Chiggers were speciated morphologically by visual inspection and morphometry using a camera-mounted light microscope (x100). A total of 394 life stages of mites were collected. Three different genera were identified, including Leptotrombidium, Schoengastiella, and Microtrombicula. Leptotrombidium imphalum (72.59%; n=286) was the predominant species, followed by Schoengastiella punctata (8.12%; n=32). Some specimens were identifiable only up to genus level, Leptotrombidium sp. (3.55%; n=14) and Microtrombicula sp. (4.82%; n= 19). Some (7.11%; n=28) were not trombiculid mites, while 3.81%; n=15 was damaged beyond identification. Leptotrombidium imphalum was detected for the first time parasitizing the murids - Rattus novergicus and Tatera indica in the district of Galle, a new locality. In addition, S. punctata was recorded in a new locality in the Gampaha district, Western province with a new host association, Golunda ellioti. This study emphasizes the need for further entomological surveys in ST disease-endemic areas. Developing a morphological identification key for chigger mites in Sri Lanka is a top priority to facilitate field surveys.Item Public knowledge, practices and perceptions on typhus fevers in Southern Sri Lanka(Wolters Kluwer Medknow Publications, 2022) Liyanage, A.; Chandrasena, N.; Gunathilaka, N.; Sanjeewa, R.; Premaratna, R.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: χ2=15.713, P<0.001; headache: χ2=19.447, P<0.001; lymphadenopathy: Fisher’s exact test, P=0.023; eschar: χ2=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.