Dermotropic Leishmania donovani in Sri Lanka: visceralizing potential in clinical and preclinical studies.

The visceralizing potential of apparently dermotropic Leishmania donovani in Sri Lanka (L. donovani-SL) was investigated through long-term follow-up of cutaneous leishmaniasis (CL) patients and in vivo and in vitro experimental infection models. CL patients (n = 250) treated effectively with intra-lesional antimony therapy were followed-up six monthly for 4 years. There was no clinical evidence of visceralization of infection (VL) during this period. Infection of BALB/c mice with L. donovani-SL (test) through intra-dermal route led to the development of cutaneous lesions at the site of inoculation with no signs of systemic dissemination, in contrast to the observations made in animals similarly infected with a visceralizing strain of L. donovani-1S (control). Cytokine (IL-10, IFN-γ) release patterns of splenocytes and lymph node cell cultures derived from mice primed with experimental infections (with either test or control parasites) revealed significantly high IFN-γ response associated with test mice with CL, while prominent IL-10 levels were observed in association with control mice with VL. Furthermore, diminished infection efficiency, intracellular growth and survival of L. donovani-SL parasites compared with L. donovani-1S were evident through in vitro macrophage infection experiments. These studies confirm, for the first time, the essential dermotropic nature of L. donovani-SL suggesting natural attenuation of virulence of local parasite strains.

Clinical and epidemiological studies on the cutaneous leishmaniasis caused by Leishmania (Leishmania) donovani in Sri Lanka.

Sri Lanka is the newest reported focus of human leishmaniasis within the Indian subcontinent. Over the last 8 years, more than 2000 cases of cutaneous leishmaniasis (CL), apparently caused by Leishmania donovani (a species usually associated with the visceral form of the disease), have been passively identified in the country. The clinical profiles of 401 suspected cases of CL in Sri Lanka were recently explored and some of the cases' immunological responses were investigated, in antibody-detection assays based on the rk39 antigen. These studies were followed by cross-sectional surveys, involving active case detection, in three areas of Sri Lanka, two of them known to be at relatively high risk for CL, with the aims of estimating the local prevalences of the disease and identifying the main risk factors for its acquisition. This appears to be the first detailed report on the prevalence, risk factors and human serological response associated with human leishmaniasis in Sri Lanka. Although the data collected indicated that the transmission of the parasite causing CL was mostly outdoor (and possibly zoonotic) in the north of the country, most of the transmission in the south seemed to be peridomestic. The CL was found to affect a wide age range, in both male and female subjects. Curiously, the 24 cases of CL that were investigated in the rk39 assays gave negative results whereas the single cases of mucosal or visceral leishmaniasis that were studied were found positive for antibodies reacting with the rk39 antigen. More programmes of active case detection need to be launched across Sri Lanka before the true national burden posed by human leishmaniasis can be accurately evaluated. General awareness of leishmaniasis needs to be raised. Hopefully, continued research and disease monitoring will allow the effective control of leishmaniasis in Sri Lanka.

Emergence of visceral leishmaniasis in Sri Lanka: a newly established health threat.

BACKGROUND: Sri Lanka is a new focus of human cutaneous leishmaniasis caused by a genetic variant of usually visceralizing parasite Leishmania donovani. Over 3000 cases have been reported to our institution alone, during the past two decades. Recent emergence of visceral leishmaniasis is of concern. METHODS: Patients suspected of having visceral leishmaniasis (n = 120) fulfilling at least two of six criteria (fever > 2 weeks, weight loss, tiredness affecting daily functions, splenomegaly, hepatomegaly and anemia) were studied using clinic-epidemiological, immunological and haematological parameters. Seven cases (four progressive, treated (group A) and 3 non- progressive, potentially asymptomatic and observed (group B) were identified. Clinical cases were treated with systemic sodium stibogluconate or amphotericin B and all were followed up at the leishmaniasis clinic of University of Colombo for 3 years with one case followed up for 9 years. RESULTS: All treated cases responded well to anti leishmanial treatment. Relapses were not noticed. Clinical features subsided in all non-progressive cases and did not develop suggestive clinical features or change of laboratory parameters. Visceral leishmaniasis cases have been originated from different districts within the country. Majority had a travel history to identified local foci of cutaneous leishmaniasis. CONCLUSION: Visceral leishmaniasis is recognized as an emerging health threat in Sri Lanka. At least a proportion of locally identified strains of L. donovani possess the ability to visceralize. Apparent anti leishmanial sensitivity is encouraging. Timely efforts in disease containment will be important in which accurate understanding of transmission characteristics, increased professional and community awareness, improved diagnostics and availability of appropriate treatment regimens.

Use of a clinical tool for screening and diagnosis of cutaneous leishmaniasis in Sri Lanka.

Cutaneous leishmaniasis (CL) was first detected in Sri Lanka in 1992.Local disease is caused by a genetically different variant of Leishmania donovani. Early case detection and management is the mainstay of L. donovani control. High degree of clinical suspicion is critical but a clinical diagnostic tool is not available for leishmaniasis. Current study described, for the first time, a two-staged clinical algorhythm that facilitates screening of CL in Sri Lanka by primary health care worker in stage 1 and management by medical professional in stage 2.Selected clinical markers of 400 patients suspected of CL were analysed retrospectively with laboratory confirmation of leishmaniasis. Ten clinical markers predicted CL with a over 90% accuracy. Subsets of markers showed high levels of sensitivities (60-97.2%) and/or significant association with positive laboratory results as compared to negative lesions [typical onset (acne-form, painless non-itchy), (P = 0.026), size up to 2 cm (P = 0.046), well-defined edges (P = 0.002), regular edges (P = 0.018), rounded shape (P = 0.030), and lesions at 5-8 months (P = 0.052)]. Five of them (typical onset, number up to 2, small size, rounded edges, and rounded shape) also had > 70% sensitivity levels as compared to laboratory findings. Typical onset had the highest sensitivity of 97% and a PPV of 72%. Lesions at 5-8 months duration having defined edges (P = 0.013, specificity 89.7%, PPV 83.1) or having regular edges (P = 0.006, specificity 86.2%, PPV 82.4%) were also predictive of CL. Most of early laboratory-confirmed ( < 12 months) lesions remained < 3 cm (sensitivity > 67%, PPV > 70%) and had defined edges (sensitivity of 52-71%, specificity 46.7-68.8%), (PPV 75.1-86%). Four clinical markers served as good diagnostic markers in both early ( ≤ 4) and late (>12 months) lesions, viz. typical onset (91.3-98.4%), presence of ≤ 2 lesions (sensitivity 82.6-94.7%), size ≤ 2 cm (66.9-73.7%), and regular edges (68.6-76.3%). Reliability of clinical markers generally declined in chronic lesions. However, small lesions of over 12 months were highly indicative of CL (sensitivity of 66%, specificity 66.7%). None of the single/combination markers, however, were 100% sensitive or specific, highlighting the undeniable usefulness of laboratory confirmation, in diagnosis. Decision-making algorithm used 10 basic clinical features for screening and seven specific clinical markers for clinical handling and referral for investigations.

Characterisation of cutaneous leishmaniasis in Matara district, southern Sri Lanka: evidence for case clustering.

Leishmaniasis is a neglected tropical disease transmitted by Phlebotomus spp. sand flies. Cutaneous leishmaniasis (CL) in Sri Lanka is caused by Leishmania donovani. Transmission patterns are different in Southern and Northern Sri Lanka. Current study examined the prevalence, risk factors and distribution of CL in Matara District, Southern Sri Lanka. Total of 2260 individuals from four District Secretariat divisions (DSDs) were screened by house to house surveys using an interviewer administered questionnaire. The study population had an age range of 1-90 years (median = 43 ± 17.31), low monthly income ( < 20 000 LKR, 52.8%) and a male to female ratio of 1 : 2. Thirty eight patients were diagnosed by light microscopy, culture and/or PCR with a disease prevalence of 1.68%. Spatial mapping provided evidence for significant case clustering, which tended to be more prominent with proximity to forest areas. The risk factors identified were un-plastered brick walls, absence or low usage of protective measures against insect bites, low income and excessive time (>4 hours/day) spent outdoors. However, exposure of limbs while outdoors, unawareness about the disease, type of occupation, common water source as the mode of water supply and presence of animal shelters within 200 m were not associated with the risk of acquiring the disease. Peri-domestic transmission is likely to contribute to the observed case clustering with all age groups at risk of acquiring the infection. Human behavioural habits coinciding with that of the vector, sand fly are likely to enable host-vector contact promoting its spread. Appropriate vector control measures, improvement of housing conditions, public education regarding preventive measures are required to contain the spread of disease.

First successful in vitro culture of autochthonous Leishmania sp. in Sri Lanka.

Since the first autochthonous case of cutaneous leishmaniasis in Sri Lanka was reported in 1992 (1) attempts to culture the causative organisms have been unsuccessful. We report the first successful isolation of the local Leishmania sp. by in vitro culture, which would pave the way for species and strain indentification.

Some sociological aspects of cutaneous leishmaniasis in patients attending a tertiary referral centre in Colombo, Sri Lanka.

Over 1800 clinically suspected cases of cutaneous leishmaniasis have been referred to the Department of Parasitology, Faculty of Medicine, Colombo, Sri Lanka for investigation since 2001. This study analyses some sociological aspects of 120 patients with laboratory confirmed cutaneous leishmaniasis. This information is important to design and implement control programmes. The disease was predominant among males. In females lesions occurred mainly on the face, while in men they were seen mainly on the limbs. Immediate medical advice was sought by 13% of the population; the others sought treatment when the skin lesion grew or failed to heal. Females delayed seeking treatment as they probably misinterpreted the lesion as a pimple. Only 39% were referred to a Consultant Dermatologist by a medical officer during the first visit. The mean duration of time from the detection of the lesion to referral was approximately eight months. Psychologically, the presence of the lesion affected less than 20% of individuals. Costs related to treatment were relatively low in Sri Lanka. Late presentation and diagnostic delay was related to lack of awareness. Educational programmes should be carried out, aimed both at health care workers and the community to ensure early diagnosis and treatment for cutaneous leishmaniasis.