An atypical microfilaria in blood samples from inhabitants of Brazilian Amazon JournalParasitology Research PublisherSpringer Berlin / Heidelberg ISSN0932-0113 (Print) 1432-1955 (Online) CategoryOriginal Paper DOI10.1007/s00436-008-1164-4 Subject CollectionBiomedical and Life Sciences SpringerLink DateTuesday, September 09, 2008 Original Paper Parasitology ResearchFounded as Zeitschrift fur Parasitenkunde Springer-Verlag 2008 10.1007/s00436-008-1164-4 Original Paper An atypical microfilaria in blood samples from inhabitants of Brazilian Amazon Y. L. Adami1 , M. A. P. Moraes2, R. M. Lanfredi3 and M. Maia-Herzog1 (1) Laboratorio de Simulideos, Referencia Nacional em Simulideos, Oncocercose e Mansonelose, Pavilhao 108, sala 09, Instituto Oswaldo Cruz, FIOCRUZ, 21045-900 Rio de Janeiro, Brazil (2) Centro de Anatomia Patologica, Hospital Universitario de Brasilia, Via L2 Norte SGAN 604/605 Modulo C, 70840-050 Brasilia, Distrito Federal, Brazil (3) Laboratorio de Biologia de Helmintos Otto Wucherer, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro (UFRJ), 21949-902 Rio de Janeiro, Brazil Y. L. AdamiEmail: yaraadami@ioc.fiocruz.br Received: 25 June 2008 Accepted: 13 August 2008 Published online: 9 September 2008 Abstract An unindentified microfilaria sharing characteristics with Mansonella ozzardi and Onchocerca volvulus was detected in blood samples from seven human volunteers, inhabitants of a community in the border of Amazonas and Acre State. They were detected during epidemiological studies carried out in some communities along Antimary, Acre, and Purus Rivers in the Brazilian Amazon. The most striking difference was presented in the shape of the cephalic space from this microfilaria which was different from those of M. ozzardi and with similarities to O. volvulus in this region, but no remarkable differences were observed at the caudal region. More accurate studies are being carried out in order to provide additional data and supporting evidences before establishment of a new species can be done. Introduction Mansonella ozzardi is a filarial parasite autochthonous in the American Continent, and its distribution is reported in the Caribbean Islands, Central and South America. In Brazil, it was first detected in blood samples from inhabitants of Manaus (Amazonas State) by Maria Deane in 1949. Thereafter, further studies were carried out in order to provide data about distribution and prevalence of this filarial nematode in our country. Thus, human infections are frequently found in the State of Amazonas-along Solimoes, Purus, and Negro Rivers, its most important area of distribution (Batista et al. 1960). In this region, transmission is related to the blackflies Simulium amazonicum and Simulium argentiscutum whose distribution in the area frequently overlaps (Shelley et al. 1980; Moraes et al. 1985). Although the larval stages are found in blood samples of infected individuals, sometimes with high parasitic loads, the parasite is not considered of medical importance as its pathogenicity is still subject of controversy in the literature (Deane et al. 1953; Rachou 1957; Restrepo et al. 1962; Jorg 1983). Experimental infection in Erythrocebus patas has been successful in obtaining adult worms of M. ozzardi (Orihel et al. 1993), but these forms collected from human beings are not well described and its real localization in human tissues is still obscure. The difficulty to obtain adult worms from this parasite turns its diagnose based only in the morphology of the larval