Leishmaniasis in Sri Lanka: a decade old story

Visceral leishmaniasis is a vector-borne protozoan disease targeted for elimination from the Indian subcontinent by year 2020. Sri Lanka is a new focus of human leishmaniasis caused by a genetically distinct variant of Leishmania donovani, which is the species more widely known to cause visceral leishmaniasis (VL). The clinical entity that is most frequent in Sri Lanka is cutaneous leishmaniasis (CL), though a few cases of muco-cutaneous (MCL) and VL have also been reported in the recent past. In CL, papules, nodules, ulcerating nodules and ulcers occur mainly as single lesions on exposed body areas of affected individuals. A wide age range is affected including both sexes. The potential for visceralization in the cutaneous variant of L. donovani in Sri Lanka is not known. There is no evidence for a serological response in CL patients who have demonstrated negative for rK 39 antibodies in sera, (rk39 test being the recommended test for VL detection), while MCL and VL cases have been rK39 positive.Phlebotomus argentipes, the vector of L. donovani in other parts of the world is a widely prevalent insect in almost all parts of Sri Lanka. Studies are underway for vector identification. L. donovani is transmitted between this vector and the human host, the only known host for this species. However, domestic dogs have shown the presence of Leishmania parasites and also the presence of anti - L. donovani antibodies in their sera, providing primary evidence for the likely presence of an animal reservoir in Sri Lanka. Field-based risk factor studies have shown that there is peri-domestic as well as zoonotic/outdoor transmission cycles in different parts of the country.At present patients are detected mainly passively based on self referrals. Only a proportion of these patients proceed for pre-treatment laboratory confirmation due to the lack of freely available investigation facilities. Leishmaniasis was made a notifiable disease in Sri Lanka in 2008. Action plan for its control was drawn up with primary involvement of the Ministry of Health and other stake holders in 2008. Preventive and control activities are required to be put in place sooner rather than later. Enhanced case detection and active treatment are of prime value in controlling L. donovani infections. Availability of cost effective and field friendly diagnostic services in a decentralized manner, timely case management and vector control using appropriate protocols are necessary. To achieve this, a considerable amount of information is already available, and further research is needed to fill in the essential gaps.DOI: http://dx.doi.org/10.4038/sljid.v2i2.4420 Sri Lankan Journal of Infectious Diseases Vol.2(2) 2012:2-12