Disability and quality of life assessment using WHODAS-12 items 2.0 and EQ-5D-5L in a rural area endemic for loiasis in the Republic of Congo: A population-based cross-sectional study (the MorLo project).

Background: Loa loa filariasis, a parasitic infection endemic to Central Africa, is a common cause of medical consultation in this region.

Methods: To evaluate the quality of life (QoL) of individuals living in loiasis-endemic areas, we enrolled 991 subjects (one-third being microfilaremic) from the general population of a rural area in the Republic of Congo. QoL and disability were assessed using WHODAS 2.0 12-items and EQ-5D-5L questionnaires. We collected data on the number of eye worm (Ew) and Calabar swelling episodes experienced throughout their lives, as well as individual L. loa microfilarial densities and information on infections with soil-transmitted helminthiasis.

Principal findings: Individuals with a history of Ew had a nearly doubled risk of experiencing at least moderate disability (score >25/100) (adjusted Odds-Ratio = 1.77 (95%CI [1.05-2.99], p = 0.033), compared to those without such a history. Those with more than 10 episodes of Ew during their lifetime had a 28% increase in overall disability as measured by WHODAS. No other variable related to loiasis (Calabar swelling frequency, L. loa microfilarial density and positivity to L. loa antibody rapid test) was associated with the various scores. Additionally, infection with Trichuris trichiura was associated with worse anxiety score (adjusted incidence risk ratio = 1.22 (95% CI [1.06-1.39], p = 0.004)).

Conclusions: The impact of loiasis on daily QoL appears to be primarily due to adult worms rather than microfilarial density. Indeed, our findings strongly suggest that the number of Ew episodes, likely reflecting the cumulative burden of adult worms, is the main correlate of worse QoL scores. These episodes seem to affect multiple dimensions of functioning, with notable impact on mobility, pain, anxiety, and daily activities. In contrast, microfilariae would primarily induce organ dysfunction. Further studies are needed to better understand the respective clinical impacts of adult worms and L. loa microfilariae.