Excess Mortality Associated With Loiasis: Confirmation by a New Retrospective Cohort Study Conducted in the Republic of Congo

Abstract

Background Loiasis (Loa loa filariasis) is considered a benign disease and is currently not included in the WHO’s list of Neglected Tropical Diseases, despite mounting evidence suggesting significant disease burden in endemic areas. We conducted a retrospective cohort study to assess the mortality associated with L. loa microfilaremia in southwestern Republic of Congo. Methods The cohort included 3329 individuals from 53 villages screened for loiasis in 2004. We compared mortality rates in 2021 for individuals initially diagnosed as with or without L. loa microfilariae 17 years earlier. Data were analysed at the community level to calculate crude mortality rates. Survival models were used to estimate the effect of L. loa microfilaremia on mortality in the population. Results At baseline, prevalence of microfilaremia was 16.2%. During 17.62 years of cohort follow-up, 751 deaths were recorded, representing a crude mortality rate of 15.36 (95% Confidence interval [CI], 14.28-16.50) per 1000 person-years. Median survival time were 58.5 years (95% CI, 49.7-67.3) and 39.2 (95% CI, 32.6-45.8), for amicrofilaremic and microfilaremic indiviudals, respectively. Conclusion A significant reduction in life expectancy was associated with L. loa microfilaremia, confirming previous observations from Cameroon. This adds to the evidence that loiasis is not a benign disease and deserves to be included in the WHO’s list of Neglected Tropical Diseases.

Association between arterial stiffness and Loa loa microfilaremia in a rural area of the Republic of Congo: A population-based cross-sectional study (the MorLo project)

“…loa mfs in the blood is associated with excess mortality and the risk of premature death is proportionally associated with the L . loa MFD, but the causes of this excess mortality remain unidentified [ 4 , 5 ]. The possible development of arterial stiffness as a consequence of L .…”

“…In addition, two retrospective population-based cohort studies demonstrated that people with high L . loa MFD have a significantly reduced life expectancy and that the risk of premature death is proportional to an individual’s MFD [ 4 , 5 ]. Reasons for this excess mortality are still unknown and are probably multifactorial but cardiovascular diseases (CVD) could be one of the causes.…”

Analysis of diagnostic test outcomes in a large loiasis cohort from an endemic region: Serological tests are often false negative in hyper-microfilaremic infections

“…Yet some individuals may still have been misclassified as amicrofilaremic. Importantly, excess mortality and morbidity have been associated with any detectable L. loa microfilaremia [3,6,13,32]. Thus, identification of all microfilaremic patients is an important objective of loiasis diagnostics.…”

“…However, health care professionals working on loiasis have repeatedly advocated for loiasis-centered research. This call to action is supported by recent estimates indicating significant morbidity and mortality directly attributable to loiasis [2][3][4][5][6]. A better understanding of the disease, as well as development of adequate diagnostics and appropriate treatment leading to improved patient care is needed [2][3][4][5][7][8][9][10][11][12].…”

Loa loa and Mansonella perstans microfilaremia in the department of Lékoumou, Republic of Congo

“…A subsequent study involving adult Bantu from two villages in the same region indicated microfilaremia prevalences of 27.7 and 29.5% [ 3 ]. Furthermore, a survey conducted in 2004 revealed Loa loa microfilaremia prevalences ranging from 7.5 to 50.8% across 15 villages [ 6 ].…”