According to the WHO, the parasite is spreading fast in the Indian cities of Ahmedabad, Bikaner and Mumbai. It still kills fewer people than its relation P. falciparum, but is harder to prevent and treat.
“P. vivax is harder to eliminate than P. falciparum due to its relapsing nature.”
Ramesh Dhiman, India’s National Institute of Malaria Research
Poonam Khetrapal Singh, director of WHO’s South-East Asia Region, said in a statement that more work should be done on combatting vivax malaria, which contributes “a large proportion of global malaria burden”.
But traditionally, most malaria research funding has gone to P. falciparum, says a 2011 paper in PLOS Neglected Tropical Diseases.
On 28 July, the WHO released a report on P. vivax that says more than a third of the world’s population, mostly in Asia and Latin America, remain at risk of the parasite. It says that P. vivax malaria may cause up to 15 per cent of malaria deaths outside Africa.
In a statement accompanying the report, the WHO said that, of the 18.9 million cases reported in 2012, nearly 13 million were from countries in South-East Asia, mostly India.
But according to A. C. Dhariwal, director of the National Vector Borne Disease Control Programme, P. vivax control is already part of India’s Malaria Control Programme and no changes will be made to the initiative.
One complication with this form of malaria is that it can reoccur throughout an infected person’s life, making long-term treatment expensive and eradication difficult.
“P. vivax is harder to eliminate than P. falciparum due to its relapsing nature,” says Ramesh Dhiman, a scientist at India’s National Institute of Malaria Research. Moreover, treatment with the drug primaquine to prevent relapses is hard as patients have to comply with a long-term drug regimen, he says. To eradicate this form of the disease, scientists face several further challenges, including parasite resistance to drug treatment and the resistance to insecticides of the mosquitoes that transmit the disease, the WHO report says.
References Jane M. Carlton and others Why Is Plasmodium vivax a neglected tropical disease? (PLOS Neglected Tropical Diseases, 28 June 2011)
 Control and elimination of Plasmodium vivax malaria: a technical brief (WHO, July 2015)