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. IntroductionMansonella ozzardi (Nematoda: Onchocercidae) is one of the several filarial nematodes that infect humans. This relatively unknown parasite has a patchy geographic distribution across Latin America and the Caribbean, from southern Mexico to northwestern Argentina. Most infected people, regardless of the parasite density, are asymptomatic or have few symptoms. As a consequence, infections with M. ozzardi usually remain undiagnosed and untreated. Ill-defined and unspecific symptoms such as fever, arthralgia, headache, cold lower extremities, and itchy cutaneous rashes are occasionally reported by patients, but whether they are caused by M. ozzardi infection remains to be determined. Nevertheless, ocular manifestations potentially associated with mansonelliasis, especially keratitis, have attracted substantial interest from ophthalmologists in recent years. Here, we summarize key biological, epidemiological, and clinical aspects of M. ozzardi infection. We explore recent developments in pathogenesis, laboratory diagnosis, and chemotherapy and discuss the potential public health impact of this highly prevalent but largely neglected New World parasite. Biological featuresThree filarial nematodes of the genus Mansonella are known to cause human mansonelliasis: Mansonella streptocerca, which is endemic to Africa; Mansonella perstans, which is commonly found in Africa but also occurs in South America; and M. ozzardi, which is found exclusively in the Americas and the Caribbean islands.1 Only humans appear to be naturally infected with M. ozzardi; African patas monkeys (Erythrocebus patas), but not chimpanzees, rhesus, capuchin, or squirrel monkeys, are susceptible to experimental infection with this nematode. 4 Several decades later, Orihel and Eberhard described the elusive adult male and female worms recovered from experimentally infected patas monkeys. 2Natural infection with M. ...

Review of Mansonella ozzardi and its Vectors in the Neotropical Region with Emphasis on the Current Situation in Haiti

“…In the South, the focus straddling Southern Bolivia and Northern Argentina is still active, as illustred by recent publications [51][52][53][54].…”

World Wide Epidemiology of Helminths Infection

“…Mansonella ozzardi is a rare nematode but mainly present in The Americas from southern Mexico to northwestern Argentina with prevalence rate (0-46%) [16].…”

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

“…Mansonellosis, also known as Mansonelliasis, is a poorly understood human filarial infection caused by nematodes of the genus Mansonella ( Mansonella ozzardi , Mansonella perstans and Mansonella streptocerca ) . The individual Mansonella species are diagnosed based on their morphological characteristics and geographic distributions .…”

“…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 .…”

“…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 . These ocular manifestations indicate that human mansonellosis may not be completely innocuous infections, however, due to its apparently harmless nature, most infections probably remain undiagnosed and untreated …”