As recently as 2014, thousands of people across India were affected by a brutal disease called visceral leishmaniasis (VL). Known locally as kala azar and globally as black fever, VL is caused by a parasite that is transmitted by sandfly bites, after which the parasite attacks the spleen, liver, or bone marrow. Left untreated, 95% of VL cases are fatal. In 2014 alone, the country recorded over 9,200 cases.
In 2023, provisional government data showed just under 500 cases nationwide, putting India on the cusp of eliminating VL as a public health problem. What made such a remarkable turnaround possible? And what can global health leaders learn from the successful efforts to reduce visceral leishmaniasis in India?
Bhupendra Tripathi leads the foundation’s work on infectious diseases in India and has dedicated his public health career to ridding the world of preventable and treatable diseases. In the following Q&A, Bhupendra explains how this milestone reflects India’s persistent efforts and is a success story that can be emulated by other countries in their fight to eliminate neglected tropical diseases (NTDs) like VL. He also shares a warning: The sooner we act, the better we’ll be able to reduce the threat of NTDs in India and beyond as they spread to nontropical locations due to climate change.
It looks like eliminating visceral leishmaniasis (VL) in India as a public health problem is within striking distance. Why is this an exciting moment for reducing cases of neglected tropical diseases?
Bhupendra Tripathi: It’s evidence that if a disease receives sufficient attention, we have a fighting chance to eliminate it. There are many challenges when it comes to eliminating a disease. For example, it’s difficult to treat VL because it’s chronic, which means symptoms that indicate a person is infected may not appear for up to two years. During that time, the parasite is traveling inside the person’s body and that person can unknowingly become a source of transmission if clinical signs and symptoms appear.
But the biggest challenge in eliminating VL in India—and other NTDs—hasn’t been about the disease itself. It’s been a lack of attention. I have worked to eliminate other diseases like polio and measles. When I shifted to NTDs, the level of attention that something like polio received compared to kala azar, a disease not found in developed countries, was almost immediately apparent. Kala azar received little funding and was overlooked by international players.
In the 1990s, the government of India created a formal program to eliminate VL in response to a resurgence of infections. A push from the health ministry in the early 2000s gave the program even more muscle. The government committed more funding, forged new partnerships, green-lit innovative research and treatments, and engaged in cross-border collaboration. VL has been around for centuries, but once we rallied the resources, we made great strides toward eliminating it. This moment is a testament to how even the most entrenched and neglected diseases can be overcome if there is a will to do so.
What were the novel or innovative approaches that helped reduce cases of visceral leishmaniasis in India so dramatically?
Bhupendra Tripathi: It takes diligence and perseverance to defeat an infectious disease. It entails a multipronged approach that allows us to identify where the kala azar cases are, and then take steps to reduce spread. India’s system is effective because it’s incredibly thorough, from the case detection system all the way through the follow-up.
In India, anybody suffering from long-term fever or weakness is tested for kala azar. When a positive case is confirmed, every person in that village—usually about 250 families—is tested whether they display symptoms or not. The villagers continue to be surveyed about two to three times a year for the next three years. Anyone who might be infected is referred to the nearest government health facility. In 2021, 21 million people were routinely tested for VL as part of the active case search. These surveillance practices increase the likelihood of catching and treating the disease before it can spread to more people.
At the same time, in endemic areas, the inside of every room in every house and other places where sandflies like to breed, such as cattle sheds, is sprayed with insecticide twice a year to reduce the density of the sandfly population and mitigate spread. This is called indoor residual spraying. It is conducted for three years following the last known case in the area.
A new online real-time data system known as the Kala-Azar Management Information System has also enabled health officials to identify potential hotspots and dedicate extra surveillance and community engagement efforts to those locations. And support for research and development has spurred new treatments and rapid diagnostic tests.
In addition, the government implemented wage-loss compensation policies that incentivized people to seek medical help. For example, a kala azar patient in Bihar receives 6,500 rupees (US$78) as compensation for losing the ability to work because of the illness. The government dispersed US$2.4 million in wage loss compensation for kala azar between 2015 and 2021.
When we zoom out, what does the big picture for visceral leishmaniasis epidemiology in India look like right now?
Bhupendra Tripathi: We are currently in a very sweet spot. The number of VL cases in India has dropped 94% since 2014. In 2022, 632 out of 633 kala azar endemic blocks—subdistrict communities where VL has historically occurred—achieved elimination status. The data for 2023 is still provisional, but it looks likely that all 633 blocks have achieved kala azar elimination as a public health problem. This milestone will be officially recognized once the government of India and the World Health Organization review and confirm the data.
But we must not become complacent, or it could rebound. This means continuing to actively detect cases, religiously using indoor residual spraying, and supporting innovative research that helps us better understand the disease and develop more effective drugs that safely counter it. For example, research and development led by the Indian Council of Medical Research, the government of India’s research arm, revealed that people infected with HIV or who were extremely malnourished were more prone to experience VL relapses six to eight months after treatment. This finding resulted in tailored antiretroviral treatments to reduce development of the disease and prevent relapses.
What will it take for India to completely eliminate visceral leishmaniasis?
Bhupendra Tripathi: The next level is reaching zero cases of transmission. To achieve this, India must improve housing and sanitary conditions in endemic areas to make it less appealing for sandflies to breed there. Private and rural health providers need to be educated on how to diagnose VL so infected patients can receive prompt treatment.
India, Nepal, and Bangladesh’s cross-border collaboration significantly helped all three countries reduce their number of VL cases. Last year, Bangladesh became the first country to eliminate VL as a public health problem. India is nearly there, and Nepal is not far behind. The countries should continue their cross-border collaboration to monitor progress and transmission potential across the region.
However, eliminating VL is complicated by post-kala-azar dermal leishmaniasis (PKDL). It’s considered a sequel to VL in which a person who has been treated for VL can again transmit the disease if they are bitten by a sandfly. That’s because the parasite sometimes migrates from the internal organs to the patient’s skin after treatment. PKDL is particularly tricky because it’s not well known which patients might develop it or when. PKDL can appear six months to several years after the person is cured of VL. In addition, most PKDL patients delay seeking treatment because they have no noticeable symptoms besides some lesions or slightly elevated skin patches. All of this works in the parasite’s favor to spread more easily.
Many NTDs and other diseases continue to cause human suffering. Why focus on visceral leishmaniasis, and why is it so critical that this disease be eliminated now?
Bhupendra Tripathi: Climate change is making the fight against VL more urgent. VL is currently confined to tropical areas, but it will spread to other parts of the world because of climate change. We have already seen cases of VL emerge high up in the mountains of Nepal—places that used to be too cold for the parasite to thrive just a few years ago. The longer it takes to eliminate VL, the harder it will become to do so.
VL also affects the lowest-income communities and can throw families into cycles of poverty due to its debilitating effects. Overcrowded houses and communities with poor sanitation are attractive breeding grounds for the sandfly. The disease’s prevalence usually indicates that other problems, such as inadequate nutrition, housing, and education, are not being well addressed.
You’ve spent your career working to eliminate various infectious diseases, some of which reached elimination status. What have you taken away from your experience?
Bhupendra Tripathi: Progress can be slow, but with hard work goals can be achieved.
India has been polio free since 2011, and we are making good progress against tuberculosis, malaria, and even lymphatic filariasis (another neglected tropical disease in India over 40 other countries). That VL is on track to reach its target is especially inspiring, and it serves as an important case study for other countries looking to eliminate NTDs.
Once elimination is achieved, countries never have to spend as much money on these diseases ever again. Funds that are currently being spent on VL active case detection, diagnostic tests, drug purchases, insecticide use, and follow-up consultations, among other expenditures, can be steered to other priorities such as access to education or modernizing infrastructure. Health care workers can focus their energies on other diseases, and families can be spared the financial burden.
My goal is to get to a point where this terrible disease is no longer a burden—physically, emotionally, or financially. To me, that’s when we can declare victory.
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