Post-Kala-azar Dermal Leishmaniasis (PKDL) is a skin disease that follows kala-azar and can occur even in fully treated cases. The entity was first identified by Dr. U. N. Brahmachari, who established its causation and from then onwards, researchers have contributed to the understanding of this enigmatic disease. It can manifest as light-colored skin patches or lumps/bumps on the skin, which mostly start from the face and gradually involve the trunk and extremities.

At times the manifestations are similar to that of leprosy, another disease that is common in the same geographical distribution. Unlike leprosy, PKDL doesn’t cause any loss of sensation, nor does it damage the nerves. The patches/lumps/bumps are asymptomatic in nature and apart from the unsightly look, they do not cause any problem. This is one reason that PKDL patients do not seek treatment and the disease goes on progressing.

Interestingly for PKDL, it occurs in two major geographical pockets; one in the Indian subcontinent and another in eastern Africa (Sudan, Ethiopia, and Kenya). Data obtained in 2018 revealed that PKDL is distributed primarily in 6 countries, namely India contributing 75%, Sudan 9%, South Sudan 8%, Bangladesh 7%, Ethiopia 1%, and Nepal less than 1%. In India, PKDL cases are mainly found in 54 districts, whereas it is found in 45 districts in Bangladesh and 12 districts in Nepal.

In India, the affected districts are 33 are in Bihar, 11 in West Bengal, 4 in Jharkhand, and 6 in Uttar Pradesh. In West Bengal, the districts reporting PKDL cases are Darjeeling, Uttar Dinajpur, Dakshin Dinajpur, Malda, Murshidabad, South 24 Parganas, North 24 Parganas, Hooghly, Nadia, Birbhum, and Burdwan.

Though the disease is the same there are subtle differences between the two groups. In the Indian subcontinent, it develops at least 6 months beyond (usually 2-3 years) the cure of kala-azar in 5-10% of cases, whereas, in eastern Africa, it may develop simultaneously or within 6 months in 50% of cases; Sudanese PKDL shows spontaneous cure but the Indian counterpart always needs treatment.

Leishmania donovani is the agent responsible for both PKDL and Kala-azar and ‘sandflies’ are the vectors that transmit the infection. An environment conducive to the survival of sandflies favors the spread of the disease. Sandflies breed in the crevices in soil and prefer indoor temperatures of 29⁰-32⁰C during peak season and 20⁰-24⁰C in the lean season. The presence of water bodies, alluvial soil, moist fallow area, weeds favors sandfly survival. Livestock kept close to human dwellings, houses with mud walls and earthen floors, not using bednets or sleeping outside or on the ground are prominent risk-factors that play an important role in disease propagation in the Indian subcontinent.

The agent (Leishmania donovani) seeks shelter in the skin lesions of the patients of PKDL and retains the potential of being transmitted by the sand-fly bite and triggering kala-azar in another person. Thus PKDL is the reservoir of infection in the inter-epidemic period of kala-azar and to eliminate kala-azar, it is imperative to get rid of PKDL. Otherwise, all effort will go in vain. It is identified as a disease of utmost epidemiological significance in recent times when the Government of India has framed an ‘accelerated plan for the elimination of Kala-azar’ as part of the ‘National kala-azar elimination program’ and PKDL has been identified as one of the epidemiological markers of the elimination program.

The year 2020 is an important landmark in the elimination of kala-azar, with the pharmaceutical companies, donors, endemic countries and non-government organizations have come forward to support WHO’s efforts in eliminating kala-azar by sustaining, expanding, and extending drug access to ensure the necessary supply of drugs and other interventions to help control kala-azar by 2020 (London declaration on Neglected Tropical Diseases).

Since PKDL cases act as reservoirs of infection, early identification (and treatment) of PKDL cases plays a pivotal role in kala-azar control programs. Both passive and active methods of case detection are recommended by authorities. As it is evident that individuals are least concerned about the mild skin patch and lumps, passive surveillance suffers from the limitation of under-reporting. Thus, active surveillance is extremely important to eliminate the reservoir and can be arranged by various methods including house-to-house searches, arranging camps, searching the neighborhood of index case, etc.

Integrated vector control adopted under the National Vector Borne Disease Control Program (NVBDCP) is one of the strategies to bring down the vector and thereby reduce the disease burden. Indoor residual spraying is the mainstay of vector control and synthetic pyrethroids are the primary choice and if not available, then DDT is the last resort.

Coming to the treatment of the disease, the choice of drug in endemic countries is decided by the national drug policy which is developed on the basis of benefit-risk ratio, availability of anti-leishmanial medicines, and other considerations like drug resistance, health service setting, etc. In East Africa, Pentavalent antimonials (20 mg Sb⁵⁺/kg per day intramuscularly or intravenously for 30–60 days) or Liposomal amphotericin B (2.5 mg/kg per day by infusion for 20 days) are the drugs of choice; whereas in the Indian subcontinent, Amphotericin B deoxycholate (Intermittent amphotericin B deoxycholate, 1 mg/kg per day by infusion, up to 60–80 doses over 4 months with 20 days on and 20 days off) or Miltefosine (Orally for 12 weeks at a dosage of 2.5 mg/kg per day for children, 50 mg/day for people aged ≥ 12 years and < 25 kg, 100 mg/day if 25–50 kg, 150 mg/day  If > 50 kg body weight) are being used. Miltefosine has the advantage of having an oral dose is the first-line medicine in the treatment of PKDL in India.

With gathering evidence, Liposomal amphotericin B is also being used in India. The medicines are supplied free of cost and to ensure completion of therapy, the economic benefit is also offered to the patients. The participation of multipurpose health workers (MPW) and Accredited social health activists (ASHA) has brought a positive impact on case-finding and ensuring patient compliance.

Elimination of kala-azar can only be achieved if PKDL is also eliminated from society. With governmental prioritization of health effort and community participation, the target is achievable and it is possible to have a world free of kala-azar.

About the author- Dr. Nilay Kant Das, Professor, Department of Dermatology, Bankura Sammilani Medical College