Explained: Kala Azar or Black fever disease detected in West Bengal

What is kala-azar or black fever disease?

Kala-azar or Visceral Leishmaniasis is a protozoan parasitic disease, spread by sandfly bites. Sandflies are brown in colour and have hairs on their bodies. The flies are infected with the parasite called ‘leishmania donovani’.

The vector sandfly is known to live in cracks and crevices of muddy houses, especially in dark and humid corners. According to the WHO, there are 3 main forms of leishmaniases of which kala-azar is the most serious form.

The disease affects some of the poorest people and is linked to malnutrition, population displacement, poor housing, a weak immune system and a lack of financial resources. Leishmaniasis is also linked to environmental changes such as deforestation, and urbanisation, according to WHO.

In 2020, more than 90 per cent of new cases reported to WHO occurred in 10 countries: Brazil, China, Ethiopia, Eritrea, India, Kenya, Somalia, South Sudan, Sudan and Yemen.

Where has kala-azar been detected in India?

In West Bengal, the districts where the maximum number of cases were registered include Darjeeling, Malda, Uttar Dinajpur, Dakshin Dinajpur and Kalimpong. The districts of Birbhum, Bankura, Purulia, and Murshidabad have also reported a few cases, while none have been detected in Kolkata yet.

“It was found that the disease was mostly prevalent in people who have spent a considerable amount of time in Bihar, Jharkhand and in Uttar Pradesh. Some individuals from Bangladesh, too, have been showing symptoms of kala-azar,” the official said. A top bureaucrat at the state secretariat claimed that the government would treat all people diagnosed with the disease “free of cost”.

The disease is endemic in Bihar, Jharkhand, Uttar Pradesh and West Bengal. An estimated 165.4 million people are at risk, according to data from the National Centre for Vector Borne Disease Control Programme (NCVBDC). In the country as a whole, there has been a significant decline in cases over the years. In 2014, around 9,200 cases were reported while in 2021 the number fell to 1,276 cases.

What are the symptoms of kala-azar?

Irregular bouts of fever over many days, weight loss, enlargement of the spleen and liver, and anaemia are known symptoms. The skin may become dry, thin and scaly in patches and hair may be lost. In people with a light skin tone, greyish discolouration of the skin of hands, feet, abdomen and face may be seen, that is why the disease is also called “Black fever”, as per the NCVBDC.

Leishmaniasis is a treatable and curable disease, which requires an immunocompetent system and thus those having a weak immune system are prone to get severely affected. All patients diagnosed require prompt and complete treatment.

What does the treatment include?

Anti-leishmanial medicines are available for treatment. Vector control is also recommended by the WHO, which means reducing or interrupting the transmission of disease by decreasing the number of sandflies in surroundings through insecticide spray, use of insecticide-treated nets, etc.

The government aimed to eliminate the disease in India by 2015, but that deadline was missed. However, the number of cases has been brought down significantly through the National Kala-Azar Elimination Programme.

Medicines, insecticides and technical support were given by the central government, while state governments provided for costs involved in implementation. The program was implemented through State/District Malaria Control Offices and the primary health care system.