Survenue d’hémorragies rétiniennes lors du traitement de l’onchocercose par l’ivermectine chez une patiente co-infectée par la loase

The African eye worm: current understanding of the epidemiology, clinical disease, and treatment of loiasis

Loa loa, the African eye worm, is a filarial pathogen transmitted by blood-sucking flies of the genus Chrysops. Loiasis primarily affects rural populations residing in the forest and adjacent savannah regions of central and west Africa, where more than 20 million patients are chronically infected in medium and high transmission regions. For a long time, loiasis has been regarded as a relatively benign condition. However, morbidity as measured by disability-adjusted life-years lost might be as high as 400 per 100 000 residents, and the population attributable fraction of death is estimated at 14·5% in highly endemic regions, providing unequivocal evidence for the substantial disease burden that loiasis exerts on affected communities. The clinical penetrance of loiasis is variable and might present with the classic signs of eye worm migration or transient Calabar swellings, but might include common, unspecific symptoms or rare but potentially life-threatening complications. Although adult worm migration seems most closely linked to symptomatic disease, high levels of microfilaraemia are associated with clinically important complications and death. Loiasis remains difficult to diagnose, treat, and control due to an absence of reliable point-of-care diagnostic assays, safe and efficacious drugs, and cost-effective prevention strategies. This Review summarises the major advances in our understanding of loiasis made over the past decade and highlights the many gaps that await to be addressed urgently.

Loa loa infection detection using biomarkers: current perspectives

Loa loa is originally a restricted filarial worm from central Africa and some west African countries. However, numerous imported cases are being reported throughout the world due to human movement. Traditionally, its diagnosis is based on identification of microfilariae in the peripheral blood or the passage of the adult worm under the conjunctiva. However, few patients have microfilariae in their peripheral blood, while the majority of infected people are amicrofilaremic (without microfilariae in their blood), despite clinical symptoms suggesting L. loa infection. This situation suggests that diagnoses based on the presence of microfilariae in the blood or the ocular passage of an adult worm, are not sensitive. Therefore, it seems necessary to search for biomarkers to remedy this situation. Furthermore, L. loa is a major obstacle in the control of other filarial worms in areas where these filariae are co-endemic. To develop a diagnostic tool based on a biomarker, several approaches have been considered using antibodies, antigens or nucleic acid detection. However, none of the diagnostic techniques in loiasis based on biomarkers has reached the point of care as have microscopic detection of microfilariae or observation of ocular passage of a worm.

Anthelmintic activity of phenolic acids from the axlewood tree Anogeissus leiocarpus on the filarial nematode Onchocerca ochengi and drug-resistant strains of the free-living nematode Caenorhabditis elegans

The effect of three phenols (ellagic, gentisic and gallic acids) from the axlewood tree Anogeissus leiocarpus on Onchocerca ochengi and drug-resistant strains of Caenorhabditis elegans, a model organism for research on nematode parasites, is investigated. Worms were incubated in different concentrations of phenols and their survival was monitored after 48 h. Among the three acids, ellagic acid strongly affected the survival of O. ochengi microfilariae, O. ochengi adults, a wild-type C. elegans and anthelmintic-resistant strains of C. elegans, namely albendazole (CB3474), levamisole (CB211, ZZ16) and ivermectin (VC722, DA1316), with LC50 values ranging from 0.03 mm to 0.96 mm. These results indicate that the binding of ellagic acid in the worm differs from that of resistant strains of C. elegans. The efficacy of both gallic and gentisic acids was not significantly changed in resistant strains of C. elegans treated with levamisole (ZZ16, LC50= 9.98 mm, with gallic acid), albendazole (CB3474, LC50= 7.81 mm, with gentisic acid) and ivermectin (DA1316, LC50= 10.62 mm, with gentisic acid). The efficacy of these three pure compounds is in accordance with the use of A. leiocarpus from its locality of origin. The in vivo toxicity data reveal that the thresholds are up to 200 times higher than the determined LC50 values. Thus, ellagic acid could be a potential option for the treatment of nematode infections, even in cases of drug resistance towards established anthelmintic drugs.

Natural products as a source for treating neglected parasitic diseases

Infectious diseases caused by parasites are a major threat for the entire mankind, especially in the tropics. More than 1 billion people world-wide are directly exposed to tropical parasites such as the causative agents of trypanosomiasis, leishmaniasis, schistosomiasis, lymphatic filariasis and onchocerciasis, which represent a major health problem, particularly in impecunious areas. Unlike most antibiotics, there is no "general" antiparasitic drug available. Here, the selection of antiparasitic drugs varies between different organisms. Some of the currently available drugs are chemically de novo synthesized, however, the majority of drugs are derived from natural sources such as plants which have subsequently been chemically modified to warrant higher potency against these human pathogens. In this review article we will provide an overview of the current status of plant derived pharmaceuticals and their chemical modifications to target parasite-specific peculiarities in order to interfere with their proliferation in the human host.