SummaryThe feasibility of using unskilled workers at the district or village level to perform mollusciciding activities in arid regions of northern Cameroon was investigated. A simplified procedure for application to temporary ponds, the principal sites of schistosomiasis transmission in that region, was tested. This consisted of mixing the required quantitity of niclosamide (Bayluscide, Bayer AG, Leverkusen) with pond water in a plastic watering can and applying the mixture around the circumference. To aid dispersion, the can was repeatedly swept from the perimeter toward the centre of the pond. Two ponds each were treated once near the end of the rainy season at I of 3 concentrations: 0.5, 1.0 and 1.5 p.p.m. Following treatment, 100% snail mortality was recorded at all concentrations. A simple, rapid method for determining the quantity of niclosamide needed to treat temporary ponds was also devised. Physical characteristics were determined for 16 potential schistosomiasis transmission sites in the region. An integration of those characteristics was used to develop a simplified scale indicating the quantity of niclosamide needed to treat ponds based on their circumference. The operational feasibility of a village based mollusciciding programme using those simplified procedures was then evaluated in 2 villages. Village health workers demonstrated a high accuracy (87%) in identifying potential schistosomiasis transmission foci and snail host populations were virtually eliminated from treated sites.keywords village-based mollusciciding, S. haematobium, niclosamide
We investigated the acute toxicity of arsenic trioxide and atrazine, singly and in combination, to Japanese medaka embryos, and the cytotoxicity of these chemicals to human liver carcinoma cell lines (HepG2). Two day-old embryos were exposed to serial concentrations of arsenic, atrazine, and a mixture of the two, following a 96-hrs static renewal test protocol. The in vitro bioassay was performed by exposing HepG2 cells to arsenic and atrazine, and measuring the activity of lactate dehydrogenase using a spectrophotometer at 340 nm, after 48 hrs of incubation at 37°C and 5% CO2. Results of the embryo bioassay indicated a concentration-response relationship with respect to chemical toxicity. Upon 96 hrs of exposure, the NOAEL, LOAEL, LC50 and LC95 of arsenic were 0.07 (0.04–0.09), 0.15 (0.10–0.18), 0.23 (0.21–0.26), and 0.32 (0.28–0.41) mg/L, respectively. No significant differences (p > 0.05) in LC50 values were found between 24 and 96 hrs of exposure, indicating that arsenic is a fast acting chemical, with most acute poisoning occurring within 24 hrs of exposure. Within the range of concentrations tested, atrazine was found to be non-toxic to embryos, even at its maximum solubility of 200 mg/L in 2% DMSO. The mixture of arsenic with 100 mg/L atrazine resulted in a 96hrs-LC50 of 0.28 (0.26–0.31) mg/L, indicating a combined toxic effect that is simply additive or slightly antagonistic. The cytotoxicity assay yielded a LC50 value of 11.94 (8.8–15.1) mg/L for arsenic. Under the test conditions, the LC50 of atrazine was greater than 100 mg/L, and could not be computed with certainty due to its poor solubility in the test medium.
A longitudinal study was conducted to assess the impact of pollution by a Sugar-Mill Company, and the effects of domestic wastes on the water quality of the Mingoala River in Mbandjock, Cameroon. Over a period of twelve months, bimonthly field samples were collected and analyzed for a number of physico-chemical and bacteriological parameters. Study results indicated that the Mingoala River is the subject of an industrial pollution which is essentially organic in nature. Except for ammonia-N, chloride, nitrite and temperature, statistical analysis revealed significant differences between the mean values of all physical and chemical parameters studied downstream of the point of confluence between the wastestream and the river, as compared to data collected upstream. Such differences were also recorded in bacteriological assessments, with significantly higher counts of bacteria downstream, indicating a microbial contamination associated with poor sanitary conditions. The consequences of this pollution are numerous and include: 1) Degradation of downstream water quality; 2) Disappearance of fish, and appearance of disease vectors; 3) Public health impact associated with nocuous odor, and waterborne illnesses. In order to prevent future ecological damage, appropriate steps should be taken to treat the plant effluents before their discharge into receiving streams, and to educate the Mbandjock population on the cost-effectiveness of sanitation in disease prevention. In this regard, practical recommendations are made on specific pollution-prevention strategies for this community.
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