Paragonimus and paragonimiasis in West and Central Africa: unresolved questions

Paragonimiasis, human lung fluke disease, is a foodborne anthropozoonosis caused by the trematodes assigned to Paragonimus and is regarded by the World Health Organization as a Neglected Tropical Disease (NTD). The life cycle of this medically important parasite centres on a complex freshwater biological community that includes two intermediate hosts: a mollusc and a decapod, usually a brachyuran. Although there is a perception that the biology, symptoms, diagnosis and treatment of Paragonimus is well understood, in reality, this is not the case, especially in Africa. Much remains unknown concerning the life-cycle of the parasite, its transmission, the current epidemiology of the disease, diagnosis and the effectiveness of treatment. Furthermore, cases of paragonimiasis may be misdiagnosed as resistant tuberculosis (TB) because of the similar pulmonary symptoms and no remission after anti TB therapy. The endemic foci of human paragonimiasis in Africa have been reported mainly in the forest zones of Upper Guinea (Liberia, Guinea and Ivory Coast) and Lower Guinea (Nigeria, Cameroon, Equatorial Guinea and Gabon). Despite the perceived medical importance of paragonimiasis, relatively little attention has been paid to this NTD since its discovery in Africa in the 1960s. This review focuses on the current understanding of the life cycle and transmission of Paragonimus in Africa, discusses its diagnosis and public health importance and highlights many outstanding gaps in the knowledge that still exist for this NTD.