Mansonellosis: current perspectives

Abstract

Mansonellosis is a filarial disease caused by three species of filarial (nematode) parasites (Mansonella perstans, Mansonella streptocerca, and Mansonella ozzardi) that use humans as their main definitive hosts. These parasites are transmitted from person to person by bloodsucking females from two families of flies (Diptera). Biting midges (Ceratopogonidae) transmit all three species of Mansonella, but blackflies (Simuliidae) are also known to play a role in the transmission of M. ozzardi in parts of Latin America. M. perstans and M. streptocerca are endemic in western, eastern, and central Africa, and M. perstans is also present in the neotropical region from equatorial Brazil to the Caribbean coast. M. ozzardi has a patchy distribution in Latin America and the Caribbean. Mansonellosis infections are thought to have little pathogenicity and to be almost always asymptomatic, but occasionally causing itching, joint pains, enlarged lymph glands, and vague abdominal symptoms. In Brazil, M. ozzardi infections are also associated with corneal lesions. Diagnosis is usually performed by detecting microfilariae in peripheral blood or skin without any periodicity. There is no standard treatment at present for mansonellosis. The combination therapy of diethylcarbamazine plus mebendazole for M. perstans microfilaremia is presently one of the most widely used, but the use of ivermectin has also been proven to be very effective against microfilariae. Recently, doxycycline has shown excellent efficacy and safety when used as an antimicrobial against endosymbiotic Wolbachia bacteria harbored by some strains of M. perstans and M. ozzardi. Diethylcarbamazine and ivermectin have been used effectively to treat M. streptocerca infection. There are at present no estimates of the disease burden caused by mansonellosis, and thus its importance to many global health professionals and policy makers is presently limited to how it can interfere with diagnostic tools used in modern filarial disease control and elimination programs aimed at other species of filariae.

Mansonellosis, the most neglected human filariasis

“…M. ozzardi is evenly distributed in tropical regions of North and South America, from Mexico to Argentina [9] , [10] . A recent study reported a prevalence of ∼35% in Brazilian Amazon autochthons [11] , but prevalence may reach 61% in endemic regions [9] .…”

Detection of Mansonella ozzardi among blood donors from highly endemic interior cities of Amazonas state, northern Brazil

“…The individual Mansonella species are diagnosed based on their morphological characteristics and geographic distributions . Human infections with M. ozzardi are only found in the Americas, including Brazil and in the Caribbean Islands . Most human mansonellosis is asymptomatic but occasional unspecific manifestations as fever, arthralgia, headache, cold lower extremities, lymphadenopathy, and itchy cutaneous rashes can occur .…”

“…Adult female worms produce larvae called microfilariae in the mammalian host which reach the bloodstream, where they can be detected throughout the day . Microfilariae are the infectious form for vectors, but when transmitted by blood transfusion they are not infective to recipients . Although transfusion of M. ozzardi microfilariae does not establish new infections, they can survive in transfusion‐recipients for longer than 2 years; risk of any pathology is as yet unknown .…”

“…Human infections with M. ozzardi are only found in the Americas, including Brazil and in the Caribbean Islands. 2 Most human mansonellosis is asymptomatic but occasional unspecific manifestations as fever, arthralgia, headache, cold lower extremities, lymphadenopathy, and itchy cutaneous rashes can occur. 3,4 Since the late 1990's there has been a new concern regarding M. ozzardi pathogenicity due to reports of associated ocular corneal lesions, especially keratitis and eventually blindness in patients from Amazonas State.…”

“…21 Microfilariae are the infectious form for vectors, but when transmitted by blood transfusion they are not infective to recipients. 2 Although transfusion of M. ozzardi microfilariae does not establish new infections, they can survive in transfusion-recipients for longer than 2 years; risk of any pathology is as yet unknown. 22 Data on transfusiontransmitted filariasis are lacking.…”