Sri Lanka’s main malaria vector, the Anopheles culicifacies mosquito, long thought to prefer nesting in rural areas, has been found in war-affected peri-urban areas in the country’s east, according to a new medical survey.
Medical researchers were only able to study parts of the north and a single district in the east - both closed off to epidemiological surveillance during the country's 26-year-long civil war - after fighting ended in 2009.
A 2010 survey in the eastern district of Trincomalee, published recently, showed the country’s main malaria vector in wastewater drains, upending a commonly held belief that malaria vectors prefer to breed in clear, clean water more commonly found in rural areas.
Lead researcher, Nayana Gunathilaka of the molecular medicine unit at Kelaniya University, in the country’s capital, Colombo, told IRIN there is now an “urgent” need for detailed entomological surveillance in urban areas, especially war-affected ones, to detect the potential re-emergence of malaria in a country that has primarily dealt with it in the countryside.
Conflict and malaria
The researcher said massive destruction and displacement during conflict generally increases vulnerability to vector-borne diseases.
Dissanayaka Mudiyanselage Amarabandu, 61, a farmer from Trincomalee District, told IRIN that staff from the health ministry's anti-malaria campaign began conducting community awareness programmes in Padavi Siripura and Kantale villages following the war.
“They said we have to be [prepared for malaria] even though the country is concentrating on dengue eradication.”
The health ministry conducted a nationwide dengue-prevention week from 7 to 13 October. The number of dengue cases reported in 2013, as of the end of September, was near 23,500, about 10,000 fewer infections than were reported for the same period last year.
Gunathilaka says the new finding is an “early warning”, noting that the country’s North and North Central provinces are particularly vulnerable due to revived paddy farms and large-scale post-war construction, which has created pits, drains, irrigation waterways, lakes, ponds and rain water reservoirs - all fertile breeding grounds for mosquitoes.
“The country remains unprepared to face urban malaria, especially as new settlements are created in the former conflict zones to facilitate resettlement.” He added that there has also been an uptick in reports of imported cases of malaria from visitors.
As of December 2012, when the UN Refugee Agency stopped compiling statistics on internally displaced persons in Sri Lanka , almost 470,000 people had returned to the former conflict zone, joining new settlers in the north and east, including migrant workers from other parts of the country and visiting members of the diaspora, Gunathilaka observed.
Health officials are looking to replicate the 2010 malaria surveillance elsewhere, especially in former conflict zones that have had scant surveillance; the next is planned to take place in Northern Province.
The recent study in Trincomalee District acknowledges there is an absence of systematic research, particularly in the former conflict zones of the north and the east, about the link between changing ecological and weather patterns and mosquitoes’ breeding grounds. Its authors told IRIN peri-urban areas outside the former conflict zone may be at risk.
Only 15 percent of the island’s 21 million people are estimated to be living in cities or peri-urban areas, places where the population is growing at 2 percent annually.
“Sri Lanka was previously not considered vulnerable to urban malaria,” Sarath Deniyage, director of the health ministry's anti-malaria campaign, told IRIN. But now it appears Sri Lanka, like its neighbours, is increasingly facing the threat of malaria in its cities, he said.
A 2012 review of factors contributing to urban malaria transmission in sub-Saharan Africa - the world’s most malaria-affected region - also went against the “general consensus” that urbanization decreased malaria transmission. It had previously been believed that improved infrastructure, “mosquito-proof” housing, increased access to healthcare and reduced breeding sites would reduce malaria incidence in cities.
Medical research from 2008 had said that “malaria vectors are known to prefer clean water for breeding, which is difficult to come by in polluted urban areas…” But last year's review, which covered some 1,200 published articles on urbanization and malaria dating back to 1984, concluded the disease persisted in a number of African cities, in some cases more than nearby rural areas.
Poor housing, rural-to-urban migration, unpaved roads and pockets of poor healthcare access were considered factors in the spread of malaria in cities.
The Sri Lankan government declared the island malaria-free in 2012; after going three years without local (as opposed to imported) malaria infections, countries can request malaria-free certification from the World Health Organization.
That year, the government reported its lowest level of reported malaria infections - 23, near all deemed to be infections from outside the country - since 1963. Thus far in 2013, three infections have been reported, all imported cases.
There have been no recorded deaths linked to the disease since 1999.
The country had nearly eliminated malaria once before. In 1963, during the era of global eradication efforts, the country achieved a low of only 17 cases, down from 92,000 cases in 1953. But with funding declines and reduced spraying and surveillance, the country saw a resurgence to 1.5 million reported infections in 1967-1968.