Incidence of black fever (called ‘kala-azar’) in the Indian subcontinent is declining fast — and dropping below the tipping point — thanks to the interventions of World Health Organization (WHO) and the combined efforts of governments. However, fears of its resurgence are haunting the establishments.
From 33,187 cases in 2011, incidence of kala-azar in India has come down to 8,500 in 2015. But it is still prevalent in 54 districts in four states, Bihar, Jharkhand, West Bengal and UP, said Dr RK Das Gupta, joint director, National Vector Borne Disease Control Program, at a recent expert consultation meet held in the southern Indian city of Chennai.
WHO organised this “Expert Consultation on Kala-azar Vector Control” to draw vector-control experts from India, Nepal and Bangladesh and frame a set of recommendations to eliminate kala-azar as a public health concern in these countries. Central University of Tamil Nadu coordinated this two-day event that was conducted from August 19.
Officials from the WHO offices in Geneva and New Delhi and experts from the London School of Hygiene and Tropical Medicine and Spain were in Chennai to take stock of the kala-azar situation in Asia and frame control strategies. Black fever had killed thousands in the first half of last century but was curtailed during the anti-malarial blitzkrieg when each household was sprayed with insecticide.
Like malaria and dengue, it is a vector-borne disease spread by sand flies affecting the victim’s liver, spleen and bone marrow, and is fatal if left untreated. Its vector or carrier, sand flies need moisture to thrive and the poorest of poor people turn out to be soft targets. During the malarial mission, sand flies got killed but the disease resurfaced in the 1980s. Now, it is the second-largest parasitic killer in the world after malaria, responsible for an estimated 200,000 to 400,000 infections each year worldwide. Annually, over 20,000 deaths occur worldwide. India accounts for about half of these figures.
Poonam Khetrapal Singh, regional director of WHO’s South-East Asia Region, had initiated an agreement in 2014 involving the governments of India, Nepal and Bangladesh to eliminate this health menace. Through insecticide spray campaigns within households, identification of breeding areas and distribution of insecticide-treated bed nets to people with poor housing conditions, the incidence of this disease has been brought down to a considerable extent.
Prof Dr Shireen Akhter, former Director of the National Institute of Preventive and Social Medicine, Bangladesh, noted that in 2006 about 10,000 black fever cases were diagnosed in the country and an elimination drive was launched in 2008 in 100 endemic sub-districts (upazilas) to bring down the incidence levels to below one-per-ten thousand people at the upazila-level.
Dr. Dinesh Mondal, Senior Scientist at the International Centre for Diarrhoeal Diseases and Research, said their national program achieved its target in 98 of the 100 upazilas where integrated vector-control measures were executed. Dr. Mondal is confident that all those upazilas will reach the target by 2017-end. Dr Murari Lal Das, Professor at BP Koirala Institute of Health Sciences, Dharan, Nepal, presented the picture of kala-azar in Nepal and said the disease was endemic in 12 Nepalese districts, where vector-control measures were adopted.
Based on the presentations of the experts, a set of recommendations was submitted to the endemic countries to achieve the target of bringing down the incidence of black fever below the one-per-ten thousand people threshold. After reaching that target, the aim is to ensure zero transmission of the disease through targeted sprays to avoid its resurgence.
WHO recommends indoor sprays
Darting out a list of recommendations to the affected countries, WHO observed that indoor residual spray (IRS) of insecticide was the most-effective method available to control black fever. It also suggested rotation of insecticides as sand flies are developing resistance to the insecticides used. It advocated collaborations among these countries to facilitate knowledge exchange and synchronize the choice of insecticides and spray frequencies.
India has started using synthetic pyrethroids to kill sand flies instead of DDT (dichlorodiphenyltrichloroethane), which is still in use in other countries as an insecticide.
WHO wants the countries to continue routine sprays of insecticide twice a year until there are no traces of the disease. This apart, it encourages countries to distribute insecticide-treated bed-nets to people without proper housing facilities.