Combating Kala-azar: Strategies and Achievements

Kala-azar, also known as visceral leishmaniasis, has plagued the Indian subcontinent for nearly two centuries. This life-threatening parasitic disease, transmitted through the bite of infected sandflies, was once responsible for devastating epidemics claiming hundreds of thousands of lives. However, through systematic efforts and strategic interventions, India has made remarkable progress in combating this disease, particularly in the highly endemic states of Bihar and West Bengal.

Understanding the kala-azar burden in India 🔗

Kala-azar is caused by the parasite Leishmania donovani and transmitted by the sandfly Phlebotomus argentipes. The disease manifests with prolonged fever, weight loss, and enlargement of the liver and spleen-and proves fatal in over 95% of cases if left untreated. India has historically carried the majority of the global burden of this neglected tropical disease, with the state of Bihar alone accounting for most cases in the country.

In 2005, when elimination initiatives began, approximately 165.4 million people in India were at risk of infection, with active cases reported from 633 public health center blocks across four endemic states: Bihar, Jharkhand, West Bengal, and Uttar Pradesh. The disease predominantly affects the poorest populations living in rural areas with limited access to healthcare.

The three-pillar control strategy 🔗

India’s approach to eliminating kala-azar rests on three fundamental pillars: vector control through indoor residual spraying, early diagnosis and complete treatment, and community health education. This comprehensive strategy was formalized in 2005 when India launched the National Kala-azar Elimination Programme jointly with Nepal and Bangladesh, aiming to reduce the annual incidence to less than one case per 10,000 population at the block level.

Indoor residual spraying (IRS) 🔗

Indoor residual spraying is the primary vector control intervention for kala-azar in India. The sandfly’s habit of resting indoors makes it an ideal target for this method. Initially, DDT was used for spraying operations, which had shown effectiveness during the National Malaria Eradication Program in the 1950s when kala-azar cases declined dramatically as a corollary benefit.

However, studies revealed widespread sandfly resistance to DDT, prompting the program to switch to synthetic pyrethroids like alpha-cypermethrin. Research demonstrated that effective IRS could reduce indoor sandfly abundance by over 70%, which is crucial since models predict that reducing sandfly densities by 67% can achieve elimination. Studies have confirmed that IRS has substantially contributed to reducing both sandfly abundance and disease incidence in India.

The program conducts two rounds of annual spraying-the first in February-March and the second in June-July-targeting endemic blocks across Bihar, Jharkhand, West Bengal, and Uttar Pradesh. Improvements in spray quality, including the shift to hand compression pumps and better monitoring protocols, have enhanced the effectiveness of these operations.

Early diagnosis and treatment 🔗

The introduction of the rK39 rapid diagnostic test transformed kala-azar detection. This simple immunochromatographic test can confirm diagnosis within 10-20 minutes using a capillary blood sample, enabling point-of-care testing even in remote health facilities. Patients presenting with fever lasting more than two weeks along with enlarged spleen and liver in endemic areas are tested and treated promptly upon confirmation.

Treatment protocols have evolved significantly. Single-dose liposomal amphotericin B (AmBisome) at 10 mg/kg body weight has become the drug of choice, demonstrating cure rates exceeding 95%. This advancement was transformative because it reduced hospitalization from weeks to just 24 hours while maintaining excellent efficacy and safety. The treatment is provided free at primary health centers and community health centers across endemic blocks.

For patients who cannot receive liposomal amphotericin B, alternative regimens include combination therapy with paromomycin and miltefosine. The availability of oral miltefosine, the first oral antileishmanial drug approved in India in 2002, added another important tool to the treatment arsenal.

Health education and community awareness 🔗

Community mobilization and behavioral change communication form the third essential component of the elimination strategy. The program emphasizes educating communities about disease symptoms, the importance of early treatment-seeking, and vector control measures. Accredited Social Health Activists (ASHAs) play a crucial role, receiving incentives for case identification, ensuring complete treatment, and conducting follow-up visits.

Financial support mechanisms have been established to encourage patient compliance. States like Bihar and Jharkhand provide compensation of Rs. 6,600 to patients towards wage loss, while West Bengal offers nutritional support worth Rs. 6,000 for six months. These measures address the socioeconomic barriers that often prevent poor patients from completing treatment.

Focused support to Bihar and West Bengal 🔗

Bihar has historically been the epicenter of kala-azar in India, accounting for over 90% of cases. In 2019, Bihar reported 2,416 cases, followed by Jharkhand with 541 cases, Uttar Pradesh with 97 cases, and West Bengal with 87 cases. Recognizing this burden, the central government has provided substantial assistance to these states.

The National Centre for Vector Borne Diseases Control deploys Vector Borne Disease Technical Supervisors at the block level across 33 districts of Bihar, 4 districts of Jharkhand, and 11 districts of West Bengal for strengthening program monitoring and supervision. Twenty-two medical colleges across the four endemic states have been engaged to enhance surveillance and service delivery.

Centres of Excellence have been established by refurbishing laboratories and leishmaniasis wards in public hospitals in Bihar, strengthening the capacity of the elimination program and bringing advanced care closer to at-risk populations. These centers have trained thousands of ASHA workers and ensure access to appropriate diagnostics and treatment for complicated cases.

Remarkable achievements in case reduction 🔗

The results of India’s sustained efforts have been remarkable. From 34,803 cases reported in 2005, the number declined to 8,243 in 2015, and further dropped to just 524 cases in 2023-representing a reduction of nearly 98.5%. The number of endemic blocks not meeting the elimination target decreased from 633 in 2005 to zero by 2023.

By the end of 2023, all 633 endemic blocks across India achieved the elimination target of less than one case per 10,000 population. This milestone was reached across Bihar, Jharkhand, West Bengal, and Uttar Pradesh. The last block to achieve the target was in Pakur district, Jharkhand.

India has achieved a 98% reduction in kala-azar cases since 1992, marking significant progress toward WHO validation for elimination. Bangladesh became the first country in the WHO South-East Asia Region to receive validation for elimination as a public health problem in 2023, and India is now in the consolidation phase to maintain elimination for three consecutive years before seeking similar validation.

Challenges in sustaining elimination 🔗

While India has achieved the elimination threshold, sustaining these gains presents ongoing challenges. Post kala-azar dermal leishmaniasis (PKDL), which develops in 5-15% of treated patients, represents a significant threat as these individuals serve as human reservoirs for the parasite. Between 2014 and 2023, over 9,100 PKDL cases were reported in India, with many patients remaining untreated for years due to prolonged and toxic treatment regimens.

HIV-VL co-infection has emerged as another concern, with prevalence among kala-azar patients increasing to 5-7% in some areas. These co-infected patients are highly infectious to sandflies and prone to relapses, making their detection and treatment crucial for maintaining elimination status.

The program must also contend with potential insecticide resistance, the need for continued vector surveillance, and ensuring the availability of diagnostics and treatment at all health facilities in endemic regions even as case numbers decline. Active case detection, particularly house-to-house surveys conducted by trained health workers, remains essential for identifying residual transmission.

The path forward 🔗

India’s success in controlling kala-azar demonstrates what can be achieved through sustained political commitment, effective partnerships, and evidence-based strategies. The integration of simple diagnostic tools, highly effective single-dose treatment, and systematic vector control has transformed what was once a devastating public health crisis.

Maintaining these achievements will require continued vigilance, adequate resource allocation, and strengthening of primary health care systems. The lessons learned from India’s kala-azar elimination program offer valuable insights for addressing other neglected tropical diseases affecting vulnerable populations.

What do you think? How can communities in endemic regions continue to stay engaged in disease surveillance after cases have declined significantly? What role should healthcare workers at the grassroots level play in preventing the re-emergence of kala-azar?

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