Trends in Parasitology
Volume 25, Issue 10, October 2009, Pages 458-463
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Opinion
Leishmania donovani causing cutaneous leishmaniasis in Sri Lanka: a wolf in sheep's clothing?

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Research involving leishmaniasis, a newly established disease in Sri Lanka, has focused mostly on parasitological and clinical factors, with inadequate understanding of other aspects, including its epidemiology and vector. The escalation in the spread of cutaneous leishmaniasis cases within Sri Lanka and the close resemblance (genotypic and phenotypic) between the local parasite Leishmania donovani MON-37 and the parasite causing visceral leishmaniasis in India (L. donovani MON-2), underscored by the more recent case reports of autochthonous cases of visceral and mucocutaneous-like disease, are clear warnings to the health authorities, scientists and policy makers. An effective control strategy is needed to contain further spread of cutaneous disease and avert a more-virulent form of leishmaniasis becoming endemic in Sri Lanka.

Section snippets

Leishmaniasis: a global perspective

The leishmaniases are a group of vector-borne parasitic diseases that are counted among the least studied and most neglected of tropical diseases 1, 2, and come under Category 1: emerging or uncontrolled diseases, according to World Health Organization/Tropical Disease Research (WHO/TDR) classification of infectious diseases (see http://www.who.int/tdrold/publications/publications/swg_leish.htm). The astounding degree of neglect of this disease for so many years is due largely to the poor

Leishmaniasis in Sri Lanka: then and now

Leishmaniasis used to be considered as an exotic disease in Sri Lanka, linked with foreign travel and seen particularly among returnees from the Middle East or African region [11]. Local transmission was considered nonexistent, although the disease was prevalent in parts of other South Asian countries such as India, Bangladesh and Nepal, where it remains a major public health problem, with case burden as high as 21 cases per 10,000 population [10]. In Sri Lanka, the first autochthonous case of

Clinical management

The classical presentations of Sri Lankan CL are non-tender, non-itchy papules, scaling nodules or ulcers (Figure 3) affecting exposed areas of body, mainly on the extensor surfaces of limbs and the face 14, 15, 16. The lag period between the appearance of symptoms and the time of presentation of the patient at a health care centre (that enable diagnosis and treatment) can vary from a few months to a few years [14]. This latency is likely to be due to the lack of knowledge and awareness among

Causative agent

The aetiological agent of CL was isolated and propagated in the Department of Parasitology, UCFM 20, 21, 22 and confirmed as L. donovani, MON-37 both by isoenzyme characterization [23] and molecular typing methods [24]. This zymodeme has been previously reported to cause human VL in countries such as India (G. Moreno, PhD thesis, University of Montpellier, 1989), Kenya [25], Israel (L.F. Schnur et al. Abstract)1

Vector studies in Sri Lanka

Information regarding the vector of leishmaniasis in Sri Lanka dates back to 1938 [31], although the quantity of information published since then is rather limited. The presence of Phlebotomus argentipes, the established vector of the visceral form of leishmaniasis caused by L. donovani in the Indian subcontinent, has been well documented in Sri Lanka 32, 33, 34, 35. The studies carried out so far support the anthropophagic nature of the local vector 34, 35 and the environmental conditions that

Prevention and control

There are no organized efforts yet in place for the control of this disease in Sri Lanka, although the case numbers have increased since the year 2001 and the cases have been reported from almost all districts of the country 14, 15, 16 (Table 1 and Figure 2). Because notification of leishmaniasis cases to the central disease monitoring unit of the country was not a mandatory requirement within the national health sector until September 2008, the true disease burden is not known. Furthermore,

The future of leishmaniasis in Sri Lanka

The facts accrued point towards the possibility of the cutaneous form of the disease spreading further in Sri Lanka, and, more dangerously, of it mutating into a more-virulent form, with serious consequences. A recent report of a fatal case of VL [19], and hospital records that indicate two other autochthonous visceral cases and a patient with extensive mucosal tissue destruction during the period 2007–2008 could be considered as further proof for the potential of the prevalent species to

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgements

I thank Yamuna Siriwardane, Randeewari Gunaratna, Charani Abayaweera and Chandima Weligamage, Faculty of Medicine, Colombo, for their invaluable help in preparation of the figures and table. Helpful comments and suggestions on the manuscript made by Professor Jean Pierre Dedet, National Reference Centre for Leishmania, Montpellier, France is also gratefully acknowledged. Financial support for local studies on leishmaniasis was provided by the National Science Foundation of Sri Lanka.

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