Declining Burden of Plasmodium vivax in a Population in Northwestern Thailand from 1995 to 2016 before Comprehensive Primaquine Prescription for Radical Cure

Abstract

All Plasmodium cases have declined over the last decade in northwestern Thailand along the Myanmar border. During this time, Plasmodium vivax has replaced Plasmodium falciparum as the dominant species. The decline in P. falciparum has been shadowed by a coincidental but delayed decline in P. vivax cases. This may be due to early detection and artemisinin-based therapy, species-specific diagnostics, and bed net usage all of which reduce malaria transmission but not P. vivax relapse. In the absence of widespread primaquine use for radical cure against P. vivax hypnozoites, the decline in P. vivax may be explained by decreased hypnozoite activation of P. vivax relapses triggered by P. falciparum. The observed trends in this region suggest a beneficial effect of decreased P. falciparum transmission on P. vivax incidence, but elimination of P. vivax in a timely manner likely requires radical cure.

Burden of soil-transmitted helminth infection in pregnant refugees and migrants on the Thailand-Myanmar border: Results from a retrospective cohort

“…vivax to P . falciparum in this study is similar to the ratio found in the general population [ 34 ]. While the problem of malaria in pregnancy as an independent risk factor for adverse pregnancy outcome is well described [ 35 , 36 ], the role of STH infections has been largely neglected [ 37 ].…”

Towards the elimination of Plasmodium vivax malaria: Implementing the radical cure

“…falciparum than P . vivax malaria ( Fig 1 ) [ 2 ]. Similarly, successful control of falciparum malaria concomitant with delays in the reduction of P .…”

Distance matters: barriers to antenatal care and safe childbirth in a migrant population on the Thailand-Myanmar border from 2007-2015, a pregnancy cohort study

“…Treatment of malaria in pregnancy has been a major priority for preventing poor pregnancy outcomes worldwide, but the Thai/Myanmar border region faces unique challenges due to high rates of P. falciparum multi drug resistance 27 and the lack of a safe, radical cure that eliminates dormant P. vivax from the liver in pregnancy. 28 Recent initiatives have made progress by bringing curative P. falciparum treatments to rural villages 21 , but P. vivax now accounts for the majority of malaria infections in this region. 28 Since the current P. vivax treatments indicated in pregnancy only treat the blood stage of the infection, public health campaigns must focus on population-wide P. vivax screening and treatment of all non-pregnant residents, which is arguably the most effective tool to decrease the prevalence of P. vivax malaria in pregnancy in this region.…”

“…28 Recent initiatives have made progress by bringing curative P. falciparum treatments to rural villages 21 , but P. vivax now accounts for the majority of malaria infections in this region. 28 Since the current P. vivax treatments indicated in pregnancy only treat the blood stage of the infection, public health campaigns must focus on population-wide P. vivax screening and treatment of all non-pregnant residents, which is arguably the most effective tool to decrease the prevalence of P. vivax malaria in pregnancy in this region. 2…”