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Background: Loiasis is a disease of relevance in endemic populations and there has been advocacy for its inclusion on the World Health Organization's neglected tropical diseases list. As loiasis-related healthcare-seeking behaviors and related costs are unknown, we aimed to evaluate these aspects in a population residing in an endemic region in Gabon. Methods: Data were collected during a community-based, cross-sectional study assessing the disease burden due to loiasis. Diagnostics for microfilaremia were performed and a history of eyeworm was obtained. In addition, a standardized questionnaire about type of healthcare resources and frequency of use, as well as respective associated costs was administered to each participant. Loiasis related healthcare-seeking behaviors were evaluated, and the associated monetary burden was estimated as a secondary outcome of the study. Findings: Individuals diagnosed with loiasis more frequently reported any healthcare-seeking (OR 1.52 (95%CI: 1.21–1.91)), self-medicating (OR 1.62 (1.26–2.08)), inability to work (OR 1.86 (1.47–2.35)), and consulting with traditional healers (logOdds 1.03 (0.52–1.53)), compared to loiasis negative individuals. The most frequently reported treatment for the eyeworm was traditional herbs. The estimated healthcare associated costs, per positive individual, was US-$ 58 (95% CI: 21–101) per year, which would correspond to 3.5% of the reported mean household income. Extrapolation to the rural population of Gabon (n = 204,000), resulted in an annual monetary burden estimate of US-$ 3,206,000 (1,150,000–5,577,000). Interpretation: Loiasis patients have demonstrated healthcare needs, often consulted traditional healers, and used traditional treatments for disease specific symptoms. Further, loiasis seems to be associated with substantial direct and indirect costs for individuals and thus may cause a relevant economic burden for endemic populations and economies of affected countries. Author summary: Loiasis has long been considered a negligible infection, however disease perception is changing as more data on significant disease-associated morbidity and mortality are being published. Still, many important aspects of the disease, such as the socioeconomic impact, are unknown. This study was part of a larger project on loiasis associated disease burden and aimed to evaluate healthcare seeking behaviors and estimate associated costs in individuals with loiasis living in a highly endemic region. We found that loiasis is associated with healthcare consultation, self-medicating, and sick leave. Self-medicating for treatment of disease specific symptoms was frequent. Traditional treatments and pain medication were most frequently used. Based on these data, we estimated loiasis related direct healthcare costs and indirect costs due to sickness, resulting in a monetary burden of US-$ 58 (95% CI: 21–101) per loiasis positive individual per year. Extrapolating these numbers to the rural population of Gabon (n = 204,000) would correspond to a monetary burden of US-$ 3,206,000 (95% CI: 1,150,000–5,577,000). Thus, loiasis is not only associated with morbidity and mortality but also with healthcare-seeking and may cause a relevant socioeconomic burden on affected populations. Therefore, considering loiasis a negligible disease is not appropriate anymore. [ABSTRACT FROM AUTHOR]

Background: Chronic infection by Loa loa remains an unsolved immunological paradox. Despite harboring subcutaneously migrating adult worms and often high densities of microfilariae, most patients experience only relatively mild symptoms, yet microfilaricidal treatment can trigger life-threatening inflammation. Here, we investigated innate cell populations hypothesized to play a role in these two faces of the disease, in an endemic population in Gabon. Methodology/Principal findings: We analyzed numbers and activation of eosinophils and basophils, as well as myeloid-derived suppressor cell (MDSC) subsets and associated circulating cytokine levels by flow cytometry in sex- and age-matched L. loa-uninfected (LL-), -amicrofilaraemic (MF-) and -microfilaraemic (MF+) individuals (n = 42), as well as microfilaraemic individuals treated with albendazole (n = 26). The percentage of eosinophils was lower in LL- (3.0%) than in the combined L. loa-infected population, but was similar in MF+ (13.1%) and MF- (12.3%). Upon treatment of MF+, eosinophilia increased from day 0 (17.2%) to day 14 (24.8%) and had decreased below baseline at day 168 (6.3%). Expression of the eosinophil activation marker CD123 followed the same pattern as the percentage of eosinophils, while the inverse was observed for CD193 and to some extent CD125. Circulating IL-5 levels after treatment followed the same pattern as eosinophil dynamics. Basophil numbers did not differ between infection states but increased after treatment of MF+. We did not observe differences in MDSC numbers between infection states or upon treatment. Conclusions/Significance: We demonstrate that both chronic infection and treatment of L. loa microfilaraemia are associated with eosinophil circulation and distinct phenotypical activation markers that might contribute to inflammatory pathways in this setting. In this first ever investigation into MDSC in L. loa infection, we found no evidence for their increased presence in chronic loiasis, suggesting that immunomodulation by L. loa is induced through other pathways. Author summary: Loiasis–also called African eye worm for its most pathognomonic feature–is a disease caused by the helminth Loa loa, affecting over ten million people in Central and West Africa. While L. loa seems to successfully evade an effective immune response in chronic infection, treatment can lead to severe inflammation upon rapid death of L. loa larvae in the blood. Here, we investigated different subsets of immune cells hypothesized to play a role in L. loa-mediated immune modulation in chronically infected individuals and upon treatment of individuals with circulating larvae. We found that eosinophils–an important cell population in the immune response to helminths–increase in numbers and are activated in both L. loa-infection and its treatment. Myeloid-derived suppressor cells can suppress immune responses in cancer and some other infectious diseases but have never been investigated in loiasis. We hypothesized that they are involved in immunosuppression by L. loa but found no evidence thereof. Better understanding of immunomodulation in chronic loiasis may ultimately improve the management of this neglected disease. [ABSTRACT FROM AUTHOR]

Background: Chronic schistosomiasis is associated with T cell hypo-responsiveness and immunoregulatory mechanisms, including induction of regulatory T cells (Tregs). However, little is known about Treg functional capacity during human Schistosoma haematobium infection. Methodology: CD4+CD25hiFOXP3+ cells were characterized by flow cytometry and their function assessed by analysing total and Treg-depleted PBMC responses to schistosomal adult worm antigen (AWA), soluable egg antigen (SEA) and Bacillus Calmette-Guérin (BCG) in S. haematobium-infected Gabonese children before and 6 weeks after anthelmintic treatment. Cytokines responses (IFN-γ, IL-5, IL-10, IL-13, IL-17 and TNF) were integrated using Principal Component Analysis (PCA). Proliferation was measured by CFSE. Principal Findings: S. haematobium infection was associated with increased Treg frequencies, which decreased post-treatment. Cytokine responses clustered into two principal components reflecting regulatory and Th2-polarized (PC1) and pro-inflammatory and Th1-polarized (PC2) cytokine responses; both components increased post-treatment. Treg depletion resulted in increased PC1 and PC2 at both time-points. Proliferation on the other hand, showed no significant difference from pre- to post-treatment. Treg depletion resulted mostly in increased proliferative responses at the pre-treatment time-point only. Conclusions: Schistosoma-associated CD4+CD25hiFOXP3+Tregs exert a suppressive effect on both proliferation and cytokine production. Although Treg frequency decreases after praziquantel treatment, their suppressive capacity remains unaltered when considering cytokine production whereas their influence on proliferation weakens with treatment. [ABSTRACT FROM AUTHOR]