We present filaria-nested polymerase chain reaction (PCR)

Mansonella ozzardi, a relatively non pathogenic filarial parasite of man in Latin America

In this paper we investigate the utility of the COI DNA barcoding region for species identification and for revealing hidden diversity within the subgenus Trichodagmia and related taxa in the New World. In total, 24 morphospecies within the current expanded taxonomic concept of Trichodagmia were analyzed. Three species in the subgenus Aspathia and 10 species in the subgenus Simulium s.str. were also included in the analysis because of their putative phylogenetic relationship with Trichodagmia. In the Neighbour Joining analysis tree (NJ) derived from the DNA barcodes most of the specimens grouped together according to species or species groups as recognized by other morphotaxonomic studies. The interspecific genetic divergence averaged 11.2% (range 2.8–19.5%), whereas intraspecific genetic divergence within morphologically distinct species averaged 0.5% (range 0–1.2%). Higher values of genetic divergence (3.2–3.7%) in species complexes suggest the presence of cryptic diversity. The existence of well defined groups within S. piperi, S. duodenicornium, S. canadense and S. rostratum indicate the possible presence of cryptic species within these taxa. Also, the suspected presence of a sibling species in S. tarsatum and S. paynei is supported. DNA barcodes also showed that specimens from species that were taxonomically difficult to delimit such as S. hippovorum, S. rubrithorax, S. paynei, and other related taxa (S. solarii), grouped together in the NJ analysis, confirming the validity of their species status. The recovery of partial barcodes from specimens in collections was time consuming and PCR success was low from specimens more than 10 years old. However, when a sequence was obtained, it provided good resolution for species identification. Larvae preserved in ‘weak’ Carnoy’s solution (9:1 ethanol:acetic acid) provided full DNA barcodes. Adding legs directly to the PCR mix from recently collected and preserved adults was an inexpensive, fast methodology to obtain full barcodes. In summary, DNA barcoding combined with a sound morphotaxonomic framework provides an effective approach for the delineation of species and for the discovery of hidden diversity in the subgenus Trichodagmia.

No abstract

SUMMARYA previous paper reported that the intake of Onchocerca volvulus microfilariae (mff) by different species of Simulium is essentially proportional to the parasite load in the skin of infected carriers. This paper examines the fate of the ingested mff in susceptible vectors to assess the relationship between parasite intake and infective larval output in blackfly species with and without well-developed cibarial armatures. Analysis is based on data from 3 onchocerciasis endemic areas: /S. sirbanum) and the Amazonian focus between South Venezuela and Northern Brazil (S. guianense and S. oyapockense s.L).The data, which include published and unedited information collected in the field, record experimental studies of parasite uptake by wild flies maintained in captivity until the completion of the extrinsic incubation period. The relationship between L3 output (measured as the mean number of successful larvae/fly or, as the proportion of flies with infective larvae) and average microfilarial intake, was strongly non-linear. This non-linearity was best represented by a sigmoid function in case of armed simuliids (S. ochraceum s.L, S. oyapockense s.L), or by a hyperbolic expression in that of unarmed flies (S. damnosum s.L, S. guianense). These results are compatible, respectively, with the patterns of 'initial facilitation' and 'limitation' described in culicid vectors of lymphatic filariases. A maximum mean number of 1-3 L3/fly was observed in all 4 vectors. It is concluded that O. volvulus larval development to the infective stage is regulated by density-dependent mechanisms acting at the early phase of microfilarial migration out of the blackfly's bloodmeal. Damage by the bucco-pharyngeal armature may also be density dependent. A hypothesis, based on this density dependence is forwarded to explain initial facilitation, so far only recorded in vectors with well-developed cibarial teeth. Our results provide quantitative support for the conjecture that chemotherapy alone is likely to have a greater impact on reducing onchocerciasis transmission in endemic areas where the main vector has a toothed fore-gut than in foci where the vectors have unarmed cibaria.

Simulium (Trichodagmia) guianense is an important Amazonian vector of onchocerciasis. Examination of the polytene chromosome banding patterns of larvae from five sites in Brazil revealed the occurrence of four cytotypes, designated A, B, C and D. The chromosomal standard, Simulium guianense A, occurred at two localities in Goias State (on the Rio Tocantins and Rio Mucambão) where it was the only cytotype. The other three sites examined yielded one different cytotype from each: B from Rio Oyapoque in Amapa State, C from Rio Tocantins in Maranhão State, and D from Rio Xingu in Para State. All cytotypes differed by at least two fixed inversions, but a sex determining system was not evident in any cytotype. As the cytotypes have been found allopatrically it is not certain that they represent sibling species; sampling of sympatric populations would resolve this. During certain times of the year, voracious anthropophagy by S.guianense sensu lato occurs at the localities sampled for cytotypes A, C and D (biting data are not available for the cytotype B locality). In some other areas, however, S.guianense s.l. is entirely zoophilic. Further studies are needed, therefore, to elucidate the biting habits, vectorial capacity, geographic distribution and taxonomic status of these four, and perhaps additional, cytotypes comprising the S.guianense complex.

Human onchocerciasis was recently discovered in Brazil among Yanomámi Indians living along the border region with Venezuela in the States of Amazonas and Roraima. The article reports on the history of the disease's discovery, its distribution, and incrimination of vector simuliid species. The literature that has been generated on the parasite, its vectors, and control of the disease is critically analyzed as well as the organization of epidemiological surveys and the control program developed by the Brazilian government and an international agency. Suggestions for future work are made.

Experimental infection with Mansonella ozzardi of common haematophagous Diptera collected at a Ticuna Indian village on the upper reaches of the Solimões river in the Brazilian Amazon, showed that Simulium amazonicum and Simulium n.sp. are capable of supporting full development of the parasite. Natural infections with this filaria were found in both species including infective larvae in Simulium n.sp. No development of M. ozzardi occurred in Mansonia amazonensis, Culicoides insinuatus or Lepiselaga crassipes (Tabanidae). The dimensions of developing larvae of M. ozzardi in both species of black-fly were recorded. Infective larvae of this species may easily be distinguished from those of Onchocerca volvulus, also transmitted in the Amazon by a species closely resembling S. amazonicum, by the presence of a bifid tail and higher anal ratio in M. ozzardi.