International border malaria transmission in the Ethiopian district of Lare, Gambella region: implications for malaria spread into South Sudan

Abstract

Background Despite notable progress in the control and prevention of malaria in the Horn of Africa, the disease continues to cause significant morbidity and mortality in various regions of Ethiopia, and elsewhere in the region. The transmission of malaria is affected by genetic, sociocultural, and ecological factors. Lare is an Ethiopian district adjacent to the Ethio-South Sudan border, in Gambella region. The region currently has the highest prevalence of malaria in Ethiopia. This study assesses the burden and spatiotemporal patterns of disease transmission, including the effect of climatic factors on the occurrence of malaria, across an international border crossing. This understanding can assist in crafting informed programmatic and policy decisions for interventions. Methods This study was conducted in Lare district, Southwest Ethiopia, a temperate zone. A retrospective descriptive analysis was conducted using clinical service data collected between 2011 and 2021 from the 9 health facilities of the district. Both clinically diagnosed patients and those identified using microscopy and rapid diagnostic testing (RDT) were included in the study. Additionally, climate data was incorporated into analyses. Examples of analyses include malaria burden, positivity rate, incidence, species frequency, and an ANOVA to assess inter-annual case number and meteorological factor variation. Results Between 2011 and 2021, a total of 96,616 suspected malaria cases were tested by microscopy or RDT, and 39,428 (40.8%) of these cases were reported as positive. There were 1276 patients admitted with 22 deaths recorded. There were further more significant fluctuations in positivity rates across years, the highest being 74.5% in 2021. Incidence varied from 18.0% in 2011 to 151.6% in 2016. The malaria parasite species most detected was Plasmodium falciparum, followed by a smaller proportion of Plasmodium vivax. The greatest proportions of P. falciparum cases were observed in 2018 and 2019, at 97.4% and 97.0% prevalence, respectively. There was significant seasonal variation in case number, the highest observed in July through September of each year. Climatic conditions of annual rainfall, temperature and humidity favored the increment of malaria cases from June until October. Conclusion The study shows that the burden, i.e. morbidity and mortality (with fluctuating patterns) of malaria are still significant public health problems and can pose serious consequences in the district. This has implication for cross-border malaria transmission risk due to considerable border crossings. The predominant cause of the disease is P. falciparum, which causes severe complications in patients. The district has to prepare to deal with such complications for better patient care and outcomes.

Trend analysis of malaria surveillance data in West Wallaga, West Oromia, Ethiopia: a framework for planning and elimination

“…The transmission of P. vivax was also high in May (1903 cases, 2.4%) followed by July (2352 cases, 3.0%). Similar findings were reported from other studies [ 9 , 16 , 18 , 27 ]. Evidence suggested that in most parts of the country the season from September to November is noted as the peak period of malaria transmission (following the main rainy seasons) and also from May to June (following the short rainy season) [ 14 , 28 ].…”

“…Increasingly, it was declined substantially from 2014 to 2018. The finding from this study is lower than the study conducted in Gambella (85.5 cases/1000) [ 16 ], West Gonder in Amhara (273 cases/1000) [ 9 ]. This reduction might be due to national malaria elimination programmes and strategies that have been initiated by the Federal Ministry of Health of the Federal Republic of Ethiopia to scale-up and intensification of anti-malaria interventions.…”

“…In contrast, evidence shows that higher positivity rate ranged up to 41.53% was reported from the studies conducted in Welkait District, three zones (Central, North and West Gonder) of Amhara region, Gambella region and South Omo zone [ 8 , 9 , 16 , 23 ]. The existence of such variation may be explained by differences in ecology, climatic, and sociocultural conditions.…”

“…The reduction of malaria case could be due to the implementation of high impact interventions including the scale up of ACT and the use of RDTs [ 10 , 13 ]. Moreover, provision of education that increased the community awareness concerning how to use vector control tools such as insecticide-treated bed nets (ITNs), and IRS [ 16 , 23 – 25 ].…”

Bionomics, seasonal abundance and insecticide susceptibility of Anopheles (Diptera: Culicidae) in low and high malaria transmission settings in Ethiopia

“…Gambella is one of the malarious areas of Ethiopia with high malarial endemicity [18] and Lare is one of the districts in Gambella Regional State that shares border with South Sudan having high social cohesion between the border communities. Such considerable international cross-border mobility may also contribute to the region to have the highest prevalence of malaria in Ethiopia [30,31]. There is also significant seasonal variation in case number with the highest reported to occur in July through September of each year from the district and partly favored by rainfall, temperature and humidity that result in increment in malaria cases from June-October [31].…”