Mansonella ozzardi: a neglected New World filarial nematode

Abstract

Mansonella ozzardi (Nematoda: Onchocercidae) is an understudied filarial nematode, originally described by Patrick Manson in 1897, that can be transmitted by two families of dipteran vectors, biting midges (most of them members of the genus Culicoides) and black flies (genus Simulium). With a patchy geographic distribution from southern Mexico to northwestern Argentina, human infection with M. ozzardi is highly prevalent in some of the Caribbean islands, along riverine communities in the Amazon Basin, and on both sides of the border between Bolivia and Argentina. There is no clinical entity unequivocally associated with M. ozzardi infection, although fever, arthralgia, headache, cold lower extremities, and itchy cutaneous rashes are occasionally mentioned in case report series. More recently, ocular manifestations (especially keratitis) have been associated with mansonelliasis, opening an important area of investigation. Here, we briefly review the biology, epidemiology, pathogenesis, and clinical aspects of M. ozzardi infection and point to some existing knowledge gaps, aiming to stimulate a research agenda to help filling them.

Keywords: Amazon; Diagnosis; Mansonella ozzardi; Microfilariae; Nematode; Pathogenesis.

Figure 1

Schematic representation of the life cycle of Mansonella ozzardi. Modified from: Centers for Disease Control and Prevention. DPDx – Laboratory Identification of Parasitic Diseases of Public Health Concern. Mansonellosis. 2013. Available at: http://www.cdc.gov/dpdx/mansonellosis/index.html.

Figure 2

Presumed geographic distribution of Mansonella ozzardi across the Americas. Regions where this parasite has been reported (either in population-based surveys or case reports) and those that are contiguous with known endemic areas are shaded, but within each shaded region the transmission tends to be focal, with high-prevalence pockets surrounded with areas with no transmission. See main text and Table 2 for details.