stages-the microfilaria-that can be easily found into the peripheral blood of infected individuals. Unlike M. ozzardi, Onchocerca volvulus has pathogenicity and distribution well established and human infections by this parasite are found among Yanomami Indians from border region with Venezuela in the States of Amazonas and Roraima (Shelley 2002). Adult stages of O. volvulus may be found and extracted from subcutaneous nodules where they are dwelling and its larval stages lyes in to the skin but it was demonstrated that the parasite may be found in the peripheral blood of up one third of infected people in hyperendemic communities (WHO 1987). M. ozzardi presence have been reported to occur in samples of the skin (Moraes et al. 1983), and this was already cause of some misunderstandings in the past. The standard methods employed for detecting M. ozzardi and O. volvulus infections in humans are, thus, based on the detection of the microfilarias in blood and skin samples, respectively, and the morphological discrimination of them. The characteristics of a typical microfilaria are well described (Orihel and Eberhard 1982) and some anatomic markers such as body length, cephalic space, shape of body nucleation, nerve ring, terminal nucleation of the tail, and tail space can be discerned through light microscopy studies (Kozek et al. 1983). During a malaria survey conducted in some communities along Acre River, serum samples were collected and sent to our laboratory in order to evaluate its reactivity in an enzyme-linked immunosorbent assay test with Ov10, Ov11, and Ov16 recombinant proteins from O. volvulus. Surprisingly, 40% of the samples from a community named Vila Antimary (a non endemic area for O. volvulus) had positive reactions. Although these tests cannot be used to define the presence and level of infection, they are effective as an epidemiological tool to provide information about incidence of exposure and, therefore, transmission of the parasite (Bradley and Unnasch 1996). The possibility of O. volvulus presence along Acre River was subsequently investigated by Marilza Maia-Herzog and Anthony J. Shelley in the area and they found microfilarias in skin snips from human volunteers morphologically similar to M. ozzardi and with some characteristics movements of O. volvulus (personal communication). Unfortunately, some difficulties were faced in the field mainly due to the precarious conditions in the area and this material was lost during the process of fixation. However, some part of the collected skin snip was sent to Dr. Rory Post at the Natural History Museum in London for polymerase chain reaction examination, and parasite DNA studies showed only M. ozzardi in the area (Shelley 2002). The present report involves an active filarial epidemiological survey carried out on the border of Amazonas and Acre States along the Antimary, Acre, and Purus Rivers and a light microscopy study of the microfilarias found in the area. Material and methods Study Area: Mapinguari (92408 S 680851.6 W), Andarai (91729.8 S 674544.0 W), Porto Acre (93542.8 S 673235.9 W), Vila Antimary (90401.0 S 672350.1 W), and the Kamikua Indian Village in Boca do Acre (84507 S 672352 W) were the selected communities along Antimary, Acre, and