Examination of Antibody Responses as a Measure of Exposure to Malaria in the Indigenous Batwa and Their Non-Indigenous Neighbors in Southwestern Uganda

Abstract

Abstract. Understanding variations in malaria transmission and exposure is critical to identify populations at risk and enable better targeting of interventions. The indigenous Batwa of southwestern Uganda have a disproportionate burden of malaria infection compared with their non-indigenous neighbors. To better understand the individual-and community-level determinants of malaria exposure, a seroepidemiological study was conducted in 10 local council cells in Kanungu District, Uganda, in April 2014. The Batwa had twice the odds of being seropositive to two Plasmodium falciparum-specific antigens, apical membrane antigen-1 and merozoite surface protein-1 19 , compared with the non-indigenous Bakiga (odds ratio = 2.08, 95% confidence interval = 1.51-2.88). This trend was found irrespective of altitude level and after controlling for cell location. Seroconversion rates in the Batwa were more than twice those observed in the Bakiga. For the Batwa, multiple factors may be associated with higher exposure to malaria and antibody levels relative to their non-indigenous neighbors.Considerable heterogeneity in malaria transmission levels and disease burden can be found within and between populations in endemic areas, due to variations in local vector populations, socioeconomic factors, and individual susceptibility.1,2 Understanding this variation is important to enable better deployment of interventions to reach the populations most at risk.Malaria transmission intensity is commonly measured using the entomological inoculation rate (EIR; the number of infectious bites per person per year) and/or parasite rate (the number of infected individuals per population). However, in low-transmission settings, these metrics lack sensitivity due to low numbers of infected mosquitos and humans. Serological techniques are increasingly used in the assessment of malaria transmission intensity and provide credible estimates of transmission that correlate well with EIR. 4 At an individual level, antibody responses can provide an alternative measure against which to assess risk of exposure to infection. 5,6 This study presents the results of a seroepidemiological study investigating exposure to malaria in the indigenous Batwa and neighboring non-indigenous populations in Kanungu District, located in southwestern Uganda, bordering the Democratic Republic of Congo. The district is largely rural and is characterized by mesoendemic malaria transmission with intermittent epidemics of disease. 7,8 Rainfall is bimodal with peaks in April and October.The Batwa are traditional hunter-gatherers from Uganda, Burundi, Rwanda, and eastern Congo.9 There are approximately 6,700 Batwa individuals residing in southwestern Uganda, comprising the easternmost population of central Africa's pygmy population. 10 In 1992, the Batwa in Uganda were evicted from their traditional forest homelands due to the formation of Bwindi Impenetrable National Park. 11 The dominant non-indigenous ethnic group in the region, the Bakiga, are traditional agriculturalists, origin...

Do socio-demographic factors modify the effect of weather on malaria in Kanungu District, Uganda?

“…1 ), where they relied on subsistence hunting and gathering; eviction from the park forced them into settlement in agrarian communities outside the park boundaries (19). There are currently approximately 6700 Batwa individuals living in southwestern Uganda [ 20 ], 900 of whom live within Kanungu District. There are no notable ecological or geographic differences in the areas where the Batwa or Bakiga live that would increase risk of malaria in either population (Fig.…”

Malaria Prevalence and Associated Risk Factors among Batwa Indigenous People of Kanungu District in Southwestern Uganda: Does “Place” Matter?

“…Some of the underlying risk factors for this high prevalence among Batwa have been linked to relative poverty, not owning a bed net, iron sheet roofing with openings for mosquito entry, not avoiding mosquito bites, malnutrition, stagnant water and bushy environment around homesteads [16] [17] [23] [48]. Relatedly, [43] strongly suggested that indigenous Batwa in Kanungu are a population at heightened risk of malaria exposure and infection. After adjusting for age, infection status, elevation, and clustering by villages, [43] found that the Batwa had two-fold higher odds of being malaria seropositive compared with the Bakiga (OR = 2.08, 95% CI = 1.51 -2.88).…”

“…Relatedly, [43] strongly suggested that indigenous Batwa in Kanungu are a population at heightened risk of malaria exposure and infection. After adjusting for age, infection status, elevation, and clustering by villages, [43] found that the Batwa had two-fold higher odds of being malaria seropositive compared with the Bakiga (OR = 2.08, 95% CI = 1.51 -2.88). In line with this study, it was discovered that majority of Batwa 76.6% (n = 408) did not sleep under any net, and 58% did not sleep under an ITN the night prior to the survey.…”

“…January 2014 (n = 572) and April 2014 (n = 541). January and April represent two different seasons in the area, namely January the dry and April rainy seasons respectively [43]. Prior to the first survey in January a group of surveyors was trained and the survey questionnaire pre-tested to ensure consistency and flow of the questions.…”

Developing an online food composition database for an Indigenous population in south-western Uganda

“…The Batwa community, self-identified as Indigenous, lives in south-western Uganda and represents a minority group in Kanungu District (14) . The Bakiga community resides in the same area and constitutes the majority population in the district (15,16) . The Batwa were originally hunter-gathers until their displacement in 1991 from the forest, now known as Bwindi Impenetrable National Park (17) .…”