Epidemiology of malaria among the Rohingya refugees in Cox’s Bazar of Bangladesh

Abstract

Background Investigating malaria occurrence in trans-border refugee settings of complex emergencies in any endemic area for malaria can offer valuable information to complement the peacetime experience and strategic plan of eliminating the mosquito borne disease across all transmission intensities by targeting appropriate interventions over time, space, and population. Migrated human population from one endemic country for malaria, here Myanmar to another endemic country, Bangladesh was thought to pose additional threats of spreading malaria further in the receptive country. In such, constructing the epidemiology of malaria among the Rohingya refugees in Bangladesh was the major aim in this work. Accordingly, in a prospective cross sectional study, the data of the results of rapid diagnostic test and microscopy based mass malaria survey (screening) in two refugee camps- Kutupalong registered camp (N= 18223, n= 1940) and Nayapara mega camp (N= 68274, n= 28520) in respectively Ukhiya and Teknaf upazilas of Cox’s Bazar were analyzed. The study period spanned over three years from March, 2017 to February, 2020.

Methodology The study included mostly passive detection (96%) approach in which malaria tests were done on self-presented febrile patients in the primary health care centres in the camps with a few active detection (4%) through collecting the sample bloods from door to door visits by the health workers. In both cases, plasmodial lactate dehydrogenase (pLDH) and histidine rich protein-2 (HRP-2) based Pv/Pf RDT and conventional light microscopy based malaria tests were done. The blood tests were done in the concerned PHCC in a camp and the data were recorded and preserved in malaria registers in written before creating electronic data base on MS-Excel. The various incidences of malaria in the two camps were compared by diagnostic technique, the host peoples’ age, sex, and pregnancy, plasmodial species, episodes of traveling to forests, using bed nets (insecticidal or not), and temporal resolution up to seasons as pre monsoon (dry season, March-June), monsoon (wet season, July-October), and post monsoon (cold season, November-February). Test positivity rate (TPR), proportion (%), average annual incidence (AAI), and annual parasite incidence (API) were used as the variables (parameters) of different incidence models of malaria occurrences. Besides, Chi-squared test and Odds Ratio (OR) were used as the tests of hypothesis or significance and measures of strength of associations in various distribution models and risk factor analyses of the incidences of the plasmodial infection.

Results During the whole study period, the overall occurrence of malaria in the two camps together (TPR, 0.16%) was considered to be actively new and uncomplicated with no case of mortality being caused by mono infections of Plasmodium falciparum (53%, TPR, 0.09%) and P. vivax (37%, TPR, 0.06%), and the mixed infections of P. falciparum and P. vivax (10%, TPR, 0.02%) that were statistically different, χ 2(2, n = 30460) = 13.76, P = .001. The AAI of malaria was 0.14% while the API stood 0.19 (per 1000 population at risk). The sum totaled malaria incidences in the two camps together in 2017-2020 as a whole were clustered in RDT as test method, χ 2 (1, n = 30460) = 19.87, p < .001, OR= 6, 95% CI, 2-13, temporally in the year, 2017-2018, χ 2(2, n = 30460) = 14.18, P < .001, demographically in people aged under 15-60 years, χ 2 (4, n = 30460), 11.86, p = .02, in males, χ 2 (1, n = 30460), 13.40, p < .001, OR, 3, 95% CI, 2-5.6, in forest travelers, χ 2 (1, n = 125) = 887.71, p < .001, OR= 120, 95% CI, 60-238, and in bed net non-users, χ 2 (1, n = 15500) =7, p = .01. Most of the camp specific annual malaria incidences were clustered in males but not in any specific age group other than that linked with forest traveling episodes. A camp specific spatial association of grand total incidence of malaria across 2017-2020 was found in favor of KRC, χ 2 (1, n = 30460) = 40.50, p = .01, OR, 6, 95% CI, 3-11. Besides, an extra ordinarily strong association prevailed between incidence of malaria and forest traveling episodes being independent of camps. The grand total seasonal malaria incidences in the two camps together were not statistically different to show seasonal biasness to monsoon in any of the three years within 2017-2020. All of the positive cases for malaria were cured by administering chloroquine-primaquine and artemether-lumefantrine (A-L) respectively for vivax and falciparum infections. There was no instance of malaria positive cases for second time after getting treatment for the first time during the whole study period.

Conclusion These findings represent an extensive observational study on malaria occurrences in the Rohingya camps in Bangladesh, first ever to build a basic epidemiology of the disease under a complex humanitarian emergency situation in the country. Overall, there remained mostly heterogeneity (unsteady, clustered) in the patterns of malaria occurrences regarding diagnostic method and most demographical characteristics while homogeneity (steady, non-clustered) in most spatiotemporal, and the pregnancy contexts. The study camps were considered to belong to very low transmission settings, whereas the forest traveling episodes emerged as an outstandingly high risk factor for malaria. A significant proportion of the positive cases was assumed to be of imported type of forest origin while very few locally transmitted malaria infections could be explained. The forests were deemed to be the infection reservoir in many occasions of malaria transmission. So, controlling human movement in and outside the camps, and mobilizing malaria resources into the forests could be one of the most effective interventions for combating malaria in the present study.