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Could climate change spread kala-azar?

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While kala-azar is endemic in pastoralist areas, scientists fear climate change and migration might see the disease spread to other unaffected regions © Photo: David Gough/IRIN

KISUMU/NAIROBI, 8 May 2014 (IRIN) - Climate change and increased population movements could see the spread of kala-azar (also known as visceral leishmaniasis or black fever) to hitherto unaffected locations, scientists warn.

While kala-azar is endemic in 98 countries, putting some 350 million people at risk of infection globally, just seven (Bangladesh, Brazil, India, Ethiopia, Kenya, Nepal, and South Sudan) account for over 90 percent of new cases.

According to Médecins Sans Frontières (MSF), “of the estimated 500,000 people in the world infected each year, many are thought to live in Bangladesh, Nepal and India.”

The disease is normally spread to humans through the bite of an infected female sand fly. It attacks the immune system and has a mortality rate of up to 95 percent if not treated within two weeks to one month. Globally, children make up 70 percent of those who die from the disease annually.

“We are worried that with the changing climate - increased rainfall, temperature and humidity - the [sand] fly could either move or expand its range of habitation,” Solomon Mpoke, director of the Kenya Medical Research Institute (KEMRI), told IRIN.

In Kenya, an estimated 4,000 cases of kala-azar are reported annually to the Ministry of Health.

In Ethiopia, where 5,000-7,000 cases of the disease are recorded each year, Tamrat Abebe, head of the Department of Microbiology at Addis Ababa University’s Tikur Anbessa Hospital, attributed recent outbreaks in lowland areas of Metema and Humera in the country’s northwest to climate change and human migration. The two regions lie at altitudes of 500-700 metres above sea level.

“Kala-azar epidemics [have] emerged in areas like Libo Kemekem [Amara Region of northwestern Ethiopia]. The new cases are worrying, since these areas were previously non endemic and no interventions were planned,” Abebe, told IRIN.

Migration/displacement can cause disease’s spread

Scientists say movements of populations from endemic regions could also lead to the spread of the disease. Poor countries which exhibit the highest burden of neglected tropical diseases, including kala-azar, are particularly vulnerable to climate change.

“Most of the new cases [in Ethiopia] have been reported among daily labourers who were travelling to endemic regions for crop harvesting,” Aysheshm Kassahun, a researcher at Addis Ababa University, told IRIN.

Koert Ritmeijer, kala-azar adviser with MSF, told IRIN: “Labourers who are moving from industrial towns back to their rural homes during holidays have always carried the disease home. And should their homes [be] conducive for vector flies, the disease will likely emerge in the village. We have seen this in Ethiopia where new cases have been recorded.”

In South Sudan, there are fears of a possible outbreak of the disease and a spike in infections as a result of the current displacement and lack of access to treatment for those affected. When heavy fighting broke out in South Sudan in mid-December, MSF reported that it was unable to reach 49 kala-azar patients in Malakal.

“For two days, the MSF team was unable to safely access Malakal State Hospital and tend [to] 49 existing patients with kala-azar… The MSF team returned to the hospital despite ongoing clashes and found that 30 of the kala-azar patients had fled,” the charity said in a statement.

How to control/treat the disease

Experts believe that early detection and treatment and also the distribution of mosquito nets in endemic regions are critical in controlling the disease.

“Active case detection through surveillance, development of protective and therapeutic vaccine against the disease remains fundamental in tackling the disease,” said Addis Ababa University’s Abebe.

In 2012, the Infectious Diseases Research Institute, IRDI, a non-profit organization, launched clinical trials for a visceral leishmaniasis/kala-azar vaccine.

The emergence of drug resistance is also a concern. According to IRDI, “the emergence of drug-resistant visceral leishmaniasis has increased the urgency of developing improved therapeutic strategies.”

In Kenya, guidelines launched by the government in 2012 call for, among other things, the use of rapid diagnostic test kits, mobile test centres and the distribution of insecticide-treated mosquito nets in areas where the disease is most prevalent.

Treatment usually consists of a 30-day course of injections of sodium stibogluconate. In Kenya this costs US$256.

In 2010, the World Health Organization’s Expert Committee on the Control of Leishmaniasis recommended Sodium Stibogluconate and aromomycin (SSG&PM) as first-line treatment for kala-azar in East Africa. While the combination therapy almost halves the length of treatment and is relatively cheap, most countries are yet to start using it.

Infected persons exhibit prolonged fever, an enlarged spleen and liver, substantial weight loss, and progressive anaemia.