Treatment and diagnosis of Loa loa and Schistosoma haematobium infections in Gabon

Abstract

Control of helminth infections, including schistosomiasis and loiasis, remains a challenge in many sub-Sahara African (SSA) countries. Schistosomiasis and malaria co-infect the same patients in many endemic rural areas, and antimalarial drugs used to treat uncomplicated malaria has been shown to have some activity against Schistosoma haematobium. For loiasis, the control of Loa loa infection is currently limited by the few drugs with not well characterized efficacy and the risk of serious adverse effects in patients with high microfilarial loads. Current adapted and safe treatment regimens to reduce microfilaraemia in endemic areas have not been established in endemic areas. In addition, the choice of treatment regimen for treatment against Loa loa depends on the level of microfilaraemia. The aim of this work was therefore to evaluate the effect of antimalarial drugs administered for uncomplicated malaria in adults and children on concomitant urogenital schistosomiasis, to evaluate the effectiveness of different therapeutic regimens to reduce Loa loa microfilaraemia and, for the first time, to evaluate different diagnostic methods for the detection and quantification of L. loa microfilaraemia and then to summarize our understanding on loiasis disease. Two therapeutics clinical trials, two cross-sectional studies (diagnostic studies) have been conducted in Gabon and a review of literature on loiasis was performed at the end. 38 malaria participants with concomitant urogenital schistosomiasis were treated with antimalarial drug combinations (artesunate-pyronaridine and artemether-lumefantrine) and were followed for 6 weeks for detection of Schistosoma eggs excretion. 39 participants with L. loa microfilaraemia were treated with albendazole based regimen or placebo and then followed for 6 months. Antimalarial treatments with artesunate-pyronaridine and artemether-lumefantrine were able to reduce S. haematobium eggs excretion by 65%. The 5-week regimen of albendazole or a 3-week regimen of albendazole followed by ivermectin were most efficacious to reduce microfilaraemia at 90% following administration of drug. For diagnostic studies, either a thick smear of 10 microliters of capillary and venous blood was prepared, or each participant`s capillary thick smears were stained in parallel with Field`s stain as a rapid staining technique and conventional Giemsa stain. Qualitative and quantitative comparison of microfilaraemia was made in sample stained with field`s stain and Giemsa staining. 713 and 175 participants respectively were included in the respective studies. The average levels of microfilaraemia of L. loa was significantly higher in capillary blood samples than in venous blood samples. Field’s stain shows excellent diagnostic performance characteristics for L. loa microfilariae compared with Giemsa staining. ACTs use for the traitment of uncomplicated malaria shown a collateral benefit on schistosoma haematobium egg reduction, and can be use as complementary tool for schistosomiasis control. Albendazole based treatment regimens may be used in control programs for loiasis. The higher levels of L. loa microfilaraemia detected in capillary blood compared to venous blood may have an implication for treatment algorithms of loiasis, for which accurate quantification of L. loa microfilaraemia is important. Field's stain offers a rapid alternative to Giemsa stain for detection of L. loa microfilariae in thick blood smears. Loiasis is a complex infectious disease which causes important morbidity and reduce life expentancy. Clinical features of loiasis are variable; inadequate diagnostic tools and unsatisfactory treatment options complicate clinical management. Importantly, we still have no tool to control and eventually eliminate loiasis from high transmission regions safely.