Onchocerca ochengi is a nodule-forming filarial nematode parasite of cattle. It is the closest known relative of the human parasite Onchocerca volvulus, with which it shares the black fly vector Simulium damnosum. Onchocerca sp. BSiisa^ was described in black flies and in cattle and, based on limited mitochondrial sequence information, appeared to be about equally phylogenetically distant from O. ochengi and O. volvulus. Based on molecular genetic markers and apparent interbreeding, we later proposed that O. sp. BSiisa^ belongs to the species O. ochengi. However, we did not demonstrate directly that the hybrids were fertile, and we were still unable to resolve the phylogenetic relationship of O. ochengi, O. sp. BSiisa,^ and O. volvulus, leaving some concerns with the conclusion mentioned above. Here, we present fully assembled, manually curated mitochondrial genomes of O. ochengi and O. sp. BSiisa,^ and we compare multiple individuals of these two taxa with respect to their whole mitochondrial and nuclear genomes. Based on the mitochondrial genomes, O. ochengi and O. sp. BSiisa^ are phylogenetically much closer to each other than to O. volvulus. The differences between them are well within the range of what is expected for within-species variation. The nuclear genome comparison provided no indication of genetic separation of O. ochengi and O. sp. BSiisa.^ From this, in combination with the earlier literature, we conclude that O. ochengi and O. sp. BSiisa^ should be considered one species.

mainly investigated, although other parts of the country were visited to a lesser extent. Onchocerciasis was found only in villages along the former two rivers. No infected individuals were recorded from 987 people sampled at thirty-five localities in the regions of Cacheu, Oio and Tombali outside the known foci. Of 516 people examined in six villages along the Geba river 102 (19 %) were infected with the disease. The data show that the disease was more prevalent in the older age groups. Skin densities were relatively low with the majority of infected individuals having less than 15 mff/mg. Investigations in villages along the Corubal river showed that 316 (37 %) of 833 individuals examined were infected. An analysis of the disease in relation to age and sex shows that although larger numbers of older people were infected the disease was also significant in younger males. Skin densities were also higher than for individuals from villages along the Geba river. Typical symptoms of onchocerciasis were seen in infected individuals and 48 of the infected people were blind (31 males and 17 females). In most cases this was due to the presence of microfilariae in the eye. The data presented indicate that the more important of the two foci is that of the Corubal river. Irrigation schemes along the upper reaches of the Geba river have drastically reduced water flow and transmission is believed to be only sporadic or even absent because of the paucity of S. damnosum s.l. in this area.

In 26 villages (1987 population 12,302), hyperendemic for savanna onchocerciasis in North Cameroon, ivermectin was distributed annually between 1987/89 and 1995. Each year until 1992, ophthalmologic examinations were performed before treatment. A final examination was made in 1995. The effects of ivermectin on ocular onchocerciasis were assessed by following (a) the ophthalmologic indices in three cohorts of males recruited before treatment in 1987, 1988 and 1989, who were treated and examined annually, and (b) the indices recorded yearly in the cross-section of males aged 15-19 years. The indices in 1995 from patients who had received up to eight doses were compared with those calculated before treatment in individuals of similar age. In the cohorts, the prevalences of microfilariae in the anterior chamber (MFAC) and of punctate keratitis (PK) recorded in 1995 were markedly reduced; there was a non-significant decrease in sclerosing keratitis (SK), and a significant worsening in the fundus indices in the cohorts. The cross-sectional analysis showed significant decreases in the prevalences of MFAC, PK and SK, and a significant increase in the mean visual acuity; there was no significant change in any fundus index. The findings suggest that repeated ivermectin treatment does not prevent the appearance of initial retinal lesions or the worsening of existing retinal lesions.

No abstract

No abstract