Cross-sectional survey of asymptomatic malaria in Dak Nong province in the Central Highlands of Vietnam for the malaria elimination roadmap

Abstract

Asymptomatic parasite carriers represent a “silent” infective reservoir for malaria transmission and contributes to malaria persistence. However, limited data are available on asymptomatic malaria in Vietnam. Between November 2018 and March 2019, we conducted a malaria epidemiological survey of asymptomatic people (children ≥ 10 years old and adults ≥18 years old, n = 2,809) residing in three communes in Tuy Duc district, Dak Nong province in the Central Highlands of Vietnam. Based on the national stratification of malaria risk, Dak Buk So, Dak Ngo and Quang Truc communes were classified by the National Malaria Control Programme as low, moderate and high malaria endemic areas, respectively. Using participants’ finger prick blood samples, malaria parasites were detected by one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The median age (Interquartile Range) for adults and children were 35 years (26–50) and 12 years (11–14), respectively. The prevalence of asymptomatic malaria was 1.7% (22/1,328), 3.5% (31/890) and 12.2% (72/591) for participants from Dak Buk So, Dak Ngo and Quang Truc, respectively. The prevalence of asymptomatic malaria was lower in children compared to adults: 2.6% (9/352) versus 4.7% (116/2,457) (Odds Ratio 0.53, 95% Confidence Interval 0.28 to1.02). Ownership of long-lasting insecticide-treated bed nets and hammocks was 97.1%, 99.0% and 94.7% for participants in Dak Buk So, Dak Ngo and Quang Truc, respectively, however, only 66.0%, 57.3% and 42.8% of the participants reported using bed nets every night. Of the several risk factors examined, going to the forest two weeks prior to enrolment into the study and sleeping in the forest had a significant association with participants being infected with asymptomatic malaria in Quang Truc, but not in the other two communes. Knowledge of the prevalence and distribution of asymptomatic malaria will help design and evaluate future intervention strategies for malaria elimination in Vietnam.

The Prevalence of Asymptomatic Malaria Amongst Nursery and Primary School Pupils in Bui, Northwest Cameroon: A Cross-Sectional Study

“…Our results were higher than those reported elsewhere in Africa and Asia; 2.8 -9.5% for mother-to-child transmissions in Burkina Faso [44], 2.6% asymptomatic malaria amongst Dak Nong children in Vietnam [56], 3.9 -8.7%% among Sherkole refugee camp and Wogera district U5C in Ethiopia [15,57], 5.2% reported in Thailand-Myanmar [22], 6.4% among U5C in endemic prone Marani -Western Kenya [48], and 6.8% reported among school children in Northwest Ethiopia [43].…”

Malaria prevalence in Commune 5 in Tumaco (Nariño, Colombia)

“…Recent studies in areas with high and low malaria transmission rates have revealed that asymptomatic infections contribute to malaria transmission. 53 Furthermore, asymptomatic malaria may precede symptomatic disease, and may confer partial immunity against infection. 54 In this study, participants were sampled at a single point in time.…”

Why using bed nets is a challenge among minority populations in Central Vietnam

“…High bed net coverage, however, does not necessarily equate with effective use, and the sub-optimal use of freely distributed bed nets has been reported in different settings, particularly among ethnic minority populations [ 15 , 16 ]. In Vietnam, the main risk groups for malaria are ethnic minorities and migrant workers whose varied demographic characteristics, forest work and mobility have been a challenge for standardized vector control interventions [ 17 – 22 ]. This paper reports the results of a mixed-methods study assessing factors limiting the uptake of ITNs in an ethnic minority setting in a remote forested area of Central Vietnam.…”