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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty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 A 58-year-old woman from Sri Lanka with fever, deafness and confusion: scrub typhus(Saunders Ltd, 2014) Premaratna, R.No abstract availableItem Scrub typhus in Sri Lanka - beyond the stethoscope(Ceylon College of Physicians, 2017) Premaratna, R.No Abstract AvailableItem Scrub typhus in an urban and semi-urban population(Sri Lanka Medical Association, 2001) Hirimuthugoda, L.; Dassanayake, A.S.; Fonseka, M.M.D.; Tillakeratne, Y.; Gunatilake, S.B.; de Silva, H.J.OBJECTIVE: Though it had been suggested that scrub typhus could be occurring in Sri Lanka, there are no properly documented case series. We document our experience with 17 cases of scrub typhus. METHODS: All patients were admitted to the University Medical Unit in North Colombo Teaching Hospital over a period of 18 months. Diagnosis of scrub typhus was made in febrile patients by the presence of an eschar, raised antibody titres to Proteus OX-K in the Weil-Felix test and the dramatic response to specific treatment with tetracycline. RESULTS: All patients presented with high fever and the duration of the fever before diagnosis varied from three days to 21 days with a mean of 9 days. Headache and myalgia were common to all. Sixteen patients were from urban and semi-urban surroundings. All patients had the eschar and in most it was in the groin and axilla. Generalised or regional lymphadenopathy was present in all patients. In nine patients the Weil-Felix test showed raised titres to Proteus OX-K antigen. Sixteen patients were treated with tetracycline and one pregnant patient with chloramphenicol. All patients responded dramatically with fever settling within 24,hours. CONCLUSIONS: Scrub typhus seems to be commoner than thought and occurs even in urban areas. This condition has to be considered in the differential diagnosis of any patient with fever and especially when the fever is not settling early. Eschar is the most useful diagnostic sign that should be looked for.Item Scrub typhus in Sri Lanka(2007) Premaratna, R.Rickettsial infections are prevalent worldwide but are seen mainly in the Asia Pacific region. These infections include epidemic typhus, endemic (murine) typhus, scrub typhus, and spotted fever group (SFG) rickettsial infections. The incidence of different rickettsial infections depends on the presence of specific vectors and their hosts. Scrub typhus is caused by Orientia tsutsugamushi. Transmission of scrub typhus requires the presence of trombiculid mites and rodents. Although scrub typhus is considered to be rural in their distribution, urbanization per se has not contributed to the decline of these infections. Recent reports from South East Asia suggest the re-emergence of rickettsial infections including scrub typhus. In Sri Lanka, we have experienced several outbreaks of suspected scrub typhus infections over the past few years. These outbreaks were in addition to year-round sporadic cases (personal experience). Many of the sporadic cases were from urban or semi-urban areas. In both clinical practice and epidemiological surveys, the main difficulty in the diagnosis and management of rickettsial infections including scrub typhus is the lack of facilities for definitive diagnosis. The available test, the Weil Felix test, is now considered obsolete, but better diagnostic techniques, such as indirect fluorescent antibody assays (IFA), are only available at reference centres. The clinical diagnosis, and therefore notification, of scrub typhus is based mainly on clinical features, such as the presence of an eschar, lymphadenopathy and hepato-splenomegaly in a patient with high intermittent fever. This is further supported by rapid defeverance with anti-rickettsial medication such as tetracycline. Although clinical manifestations of rickettsial infections are well documented, recent studies from Asian countries have reported new complications, such as gastrointestinal manifestations and hepatitis syndromes. Awareness of the different clinical presentations of these infections may assist early diagnosis, especially in areas where no diagnostic facilities are available. In the Western province, which represents the low country wet zone of Sri Lanka, the main rickettsial species causing infection seems to be O. tsutsugamushi. Delay in diagnosis seems to result in complications, such as pneumonitis, myocarditis, deafness or tinnitus, and encephalitis. All species seems to respond well to treatment with doxycycline.Item Scrub typhus mimicking Parkinson's disease(Biomed Central, 2015) Premaratna, R.; Wijayalath, S.H.N.C.; Miththinda, J.K.N.D.; Bandara, N.K.B.K.R.G.W.; de Silva, H.J.Background Scrub typhus is a re-emerging infection in Sri Lanka. It often poses a diagnostic challenge and tends to present as a febrile illness of uncertain origin. Undiagnosed illness may progress to serious multi-systemic complications. Here we report a case of scrub typhus presenting with features of Parkinsonism. Case presentation A 62-year-old previously healthy Sri Lankan native male from the Western province of Sri Lanka presented with high fever with malaise, myalgia and arthralgia for 17 days. On the 5th day of illness he developed intermittent resting tremor in his right arm and leg associated with stiffness, difficulty in carrying out normal work and difficulty in smiling. He denied similar previous episodes. There were no other associated neurological manifestations. Clinical examination revealed a high amplitude low frequency resting tremor in his right hand, a mask-like face and increased muscle tone limited to the right side with normal reflexes. The rest of the system examination was normal except for an eschar over the abdomen. His investigations revealed lymphocytic leukocytosis, high erythrocyte sedimentation rate and immunofluorescence assay-IgM and IgG against Orientia tsutsugamushi Karp antigen were positive with rising titers. With oral doxycycline and azithromycin his fever settled within 48 h and a complete recovery of Parkinson’s features was observed within 2 weeks. Conclusion Doctors practicing in endemic regions should be familiar with delayed clinical manifestations of scrub typhus and should carefully look for an eschar in order to avoid delay in the diagnosis.