M

alaria vivax should no longer be considered as being less severe than malaria falciparum as a study reveals that incompletely eradicated Plasmodium vivax parasites that invade the liver can cause malignant malaria.

A study commissioned by the Indonesian Army’s directorate of health (Ditkesad) shows that excluding primaquine, a frequently used drug for treating the dormant liver stage of infection, in treating patients with Plasmodium vivax parasites can lead to higher probability of relapses and even death.

Bagus Tjahjono, a physician at Ditkesad, said that eradicating the liver-stage malaria parasites, commonly called the “radical cure”, was the key to protecting Plasmodium vivax-infected patients against infection relapses.

“Unlike in Plasmodium falciparum infection, parasites in Plasmodium vivax infection can remain dormant in the liver for months and even up to three or four years. Without eradicating the liver stage of infection, relapses of latent infections may occur,” said Bagus on the sidelines of the signing of an agreement between Ditkesad and the Eijkman Institute for Molecular Biology last week.

In research conducted under the partnership, the safety and efficacy of primaquine combined with dihydro-artemisinin plus piperaquine as a radical cure for vivax malaria in Indonesia is being studied.

The study, supported by Oxford University, involves 600 field soldiers from Batalyon 527 Lumajang, East Java, on duty in Papua, a malaria-endemic area.

Screenings conducted on 600 soldiers returning from Papua revealed that 152 of them had malaria, comprising 143 soldiers with malaria vivax and nine with malaria falciparum. Only 116 soldiers with malaria vivax were deemed eligible to participate in the study.

During the one-year research project, researchers are studying the effectiveness of primaquine in preventing relapses in people with Plasmodium vivax infection.

Eijkman Institute chairman Sangkot Marzuki said the project was not merely to protect soldiers deployed in malaria-endemic areas such as Papua but also to meet the country’s 2015 free malaria target.

“We have put too little attention on coping with vivax malaria infections whereas such negligence may derail the target to rid our country of malaria by 2015,” he said.

In preliminary results of the study, of the 36 soldiers treated with primaquine combined with dihydro-artemisinin (DHA) plus piperaquine, only two have had relapses. Meanwhile, infections in seven of 36 soldiers treated with primaquine combined with quinine have had relapsed, whereas about 85 percent of 41 soldiers treated only with artesunate, a commonly used antimalarial drug derived from artemisinin, have had relapses.

“Plasmodium vivax infection is not a benign infection anymore but a malignant one in which the main problem of vivax malaria is its relapse potential,” Bagus said.

The study results, he said, indicated that primaquine combined with dihydro-artemisinin plus piperaquine was the most effective therapy for preventing relapses in people with Plasmodium vivax infection.

The study, which ends in April 2012, will also examine whether primaquine is really effective in preventing relapses of Plasmodium vivax infection as two soldiers involved in the study still experienced relapses.

Din Syafruddin, a senior research fellow of malaria at the Eijkman Institute, said that primaquine, an antiprotozoal medicine, was the only drug that could prevent relapses of Plasmodium vivax infection.