Parasites have found a way to bypass drug
India's preferred therapy to fight a common and deadly strain of malaria is showing early signs of efficacy loss, raising public health concerns that may be more visible a few years down the line.
The preferred treatment option for malaria cases by Plasmodium falciparum parasite is artemisinin-based combination therapy (ACT) in which anti-malarial drug artemisinin is used in combination with another medicine for enhanced efficacy.
Efficiency of this second drug in the standard therapy – known as sulfadoxine pyrimethamine (SP) – is on the wane, according to a group of Indian researchers, who claimed parasites had found a way to bypass the drug.
Though there is no therapeutic failure as yet, the standard therapy has been found to lose its efficacy in Odisha, which has one of the highest number of malaria cases in India. Last year, similar trend was seen in tea gardens of north Bengal where, too, malaria continues to be a major killer.
“It’s an early warning sign for policy-makers. After a few years, wide-spread consequences will be seen clinically,” Manoranjan Ranjit, a scientist at Regional Medical Research Centre, Bhubaneswar, who led a team of researchers from RMRC and North Orissa University, Baripada to study the efficacy of medicines used in the ACT, told Deccan Herald.
The findings have been published in a recent issue of the journal Acta Tropica.Every year, more than 15 lakh Indians get infected by malaria parasites, close to 50 per cent of which are caused by the deadly Plasmodium falciparum parasite. In Odisha, 85 per cent of malaria-related deaths are caused by this parasite.
The WHO favoured the combination therapy instead of using artemisinin alone to delay the development of drug resistance. India's malaria drug policy (released in 2010) too recommended the ACT.
“Having two drugs in the standard therapy means the parasite has to find out two keys for a lock. That will be time-consuming for the parasite. The report of SP resistance from India, therefore, is a matter of concern because so far there is only a little data from India,” commented Ramanan Laxminarayan, vice president for research at the Public Health Foundation of India, who is not associated with the study.
The Odisha researchers collected 200 odd samples from 8 districts to find out molecular signatures of the parasites becoming resistant to SP drug by genetic mutations. The mutations, Ranjit said, was spreading fast among parasites. Inclusion of SP as a partner drug in the combination therapy, therefore, made the standard therapy virtually a mono-therapy, which was prohibited in the national policy.
“These findings together with an earlier observation (from Bengal tea estates) provide early warning on the lifespan of artemisinin and SP combination and its consequence, which challenges the existing therapeutic strategy of malaria control,” the RMRC team reported.
With artemisinin-resistance widely seen in Cambodia, Vietnam, Myanmar and Thailand over the last 15 years, the WHO is all set to launch an emergency response to artemisinin resistance in the Greater Mekong Subregion.