[
Tropenmed Parasitol,
1980]
Two species of Nearctic black fly, Simulium decorum and S. pictipes, exhibit partial susceptibility to infection with the bovine parasite, Onchocerca lienalis, when inoculated intrathoracically with microfilariae. In addition, a proportion of S. decorum females will support the development of the human parasite, O. volvulus, to the third larvae stage. Infection rates with second- or third-stage larvae seven or more days after varied among geographic strains of S. decorum, ranging from 6.5% in a strain from northern New York State to 48.7% in a strain from Georgia. The average number of larvae per infected female ranged from 1.00 to 1.78 in the three strains examined. Partial susceptibility to O. lienalis was found to persist in colonized strains of s. decorum, and cryopreserved microfilariae of this parasite retained their infectivity. Seven or more days after inoculation with microfilariae of the Guatemalan strain of O. volvulus, 16.7% of the females of S. decorum harbored second- or third-stage larvae. Development of O. lienalis and O. volvulus proceeded normally in these black flies, and moderate increases in susceptibility rate and number of infective larvae were noted in response to increased microfilarial dosages.
[
Water Res,
2009]
Nematodes, which occur abundantly in granular media filters of drinking water treatment plants and in distribution systems, can ingest and transport pathogenic bacteria and provide them protection against chemical disinfectants. However, protection against UV disinfection had not been investigated to date. In this study, Caenorhabditis elegans nematodes (wild-type strain N2) were allowed to feed on Escherichia coli OP50 and Bacillus subtilis spores before being exposed to 5 and 40 mJ/cm(2) UV fluences, using a collimated beam apparatus (LP, 254 nm). Sonication (15 W, 60s) was used to extract bacteria from nematode guts following UV exposure in order to assess the amount of ingested bacteria that resisted the UV treatment using a standard culture method. Bacteria located inside the gut of C. elegans were shown to benefit from a significant protection against UV. Approximately 15% of the applied UV fluence of 40 mJ/cm(2) (as typically used in WTP) was found to reach the bacteria located inside nematode guts based on the inactivation of recovered bacteria (2.7 log reduction of E. coli bacteria and 0.7 log reduction of B. subtilis spores at 40 mJ/cm(2)). To our knowledge, this study is the first demonstration of the protection effect of bacterial internalization by higher organisms against UV treatment, using the specific case of E. coli and B. subtilis spores ingested by C. elegans.
[
Science,
1986]
Ivermectin, given to onchocerciasis patients as a single oral dose of 200 micrograms per kilogram of body weight, substantially reduced the uptake of Onchocerca volvulus microfilariae by Simulium yahense, an efficient black fly vector of the parasite in the tropical rain forests of West Africa. Three months after treatment, patients given ivermectin infected flies at a significantly lower rate than those who had received diethylcarbamazine or placebo, thereby reducing the number of developing larvae in the vector population. This diminished rate of infectiousness was also evident 6 months after treatment. These results strongly suggest that ivermectin could be effective in interrupting transmission of Onchocerca volvulus for epidemiologically important periods of time.