New cytotype in the Simulium metallicum complex (Diptera: Simuliidae) from Cundinamarca, Colombia.

Polytene chromosomes (n = 108) and morphology (n = 22) of Simulium metallicum Bellardi were described from larvae collected in different localities in Cundinamarca, Colombia, and compared with the standard polytene chromosome banding patterns of S. metallicum A. Polytene chromosomes of S. metallicum from Cundinamarca were characterized by a fixed inversion on the IIL chromosome arm (IIL-22), by 2 sex-linked inversions (IIL-24 and IIL-25), 6 floating inversions, and a heteroband in the IIIS chromosome arm. This taxon was considered to be a cytotype distinct from the 11 members of the S. metallicum complex from Central and South America, and we propose here the name S. metallicum L, following the convention for naming cytotypes in this species complex. There were slight larval morphological differences between S. metallicum from Cundinamarca and S. metallicum A and S. horacioi Okazawa & Onishi (or S. metallicum H).

Current status of onchocerciasis in Colombia.

To assess the current epidemiologic status of onchocerciasis in Colombia two surveys were undertaken in 1995 in a suspected new focus on the border between Colombia and Ecuador and in the known focus located on the Micay River. No new focus was found along the Colombia-Ecuador border. In the known focus, communities along the upper Micay River and its tributaries were surveyed; 655 adults underwent physical examinations and skin biopsies. Infected individuals were found almost exclusively in the community of Naiciona, where prevalence of infection was 40% (36 of 91). Polymerase chain reaction detection of onchocercal DNA in skin snips correlated with the skin-snip biopsy results. The prevalence of punctate keratitis, the only ocular manifestation found, was 33%. A rapid entomologic assessment demonstrated Simulium exiguum infected with Onchocerca volvulus. This is the first finding in Colombia of naturally infected black flies and confirms S. exiguum as a vector species. These data will be used for implementing a control program using periodic ivermectin distribution.

Development of Mansonella ozzardi in a black fly species of the Simulium sanguineum group from Eastern Vaupés, Colombia.

Development of the microfilaria of Mansonella ozzardi to the infective stage in a species of the Simulium sanguineum group from the Mitú area, Comisaría del Vaupés, Colombia is described. Development was synchronous, and by day 6 third-stage larvae were observed in the head of flies which had fed on two naturally infected volunteers. Simulium biting activity was high from January-March, during the dry season. Only 261 blood-fed Culicoides were collected from an infected volunteer; 40% of 43 dissected on day 0 had ingested microfilariae. However, only one of 129 C. caprilesi specimens dissected after day 2 was positive, containing a second-stage larva thought to be M. ozzardi. It is concluded that Simulium, rather than Culicoides are the principal vectors of mansonelliasis in the Mitú area.