Molecular epidemiological survey of rotaviruses in sewage by reverse transcriptase seminested PCR and restriction fragment length polymorphism assay

Rotavirus double-stranded RNA was detected directly in sewage treatment plant samples over a 1-year period by reverse transcription followed by PCR amplification of the VP7 gene and Southern blot hybridization. The presence of naturally occurring rotaviruses was demonstrated in 42% of raw sewage samples and in 67% of treated effluent samples, Amplified viral sequences were analyzed bg restriction enzymes. Ten different restriction profiles were characterized, most of which were found in treated effluent samples. A mixture of restriction profiles was observed in 75% of contaminated effluent samples, The profiles were compared with those obtained from human rotavirus isolates involved in infections in children from the same area (six different profiles were detected), Five identical viral sequences were detected in both environmental and clinical samples, Restriction profiles sere also compared io profiles from known genomic sequences of human and animal viruses. Both human and animal origins of rotavirus contamination of water seemed likely.

Sampling design optimization for EROD measurements in fish

Activity of 7-ethoxyresorufin-O-deethylase (EROD) in fish is certainly the best-studied biomarker of exposure applied in the field to evaluate biological effects of contamination in the marine environment. Since 1991, a feasibility study for a monitoring network using this biomarker of exposure has been conducted along French coasts. Using data obtained during several cruises, this study aims to determine the number of fish required to detect a given difference between 2 mean EROD activities, i.e. to achieve an a priori fixed statistical power (l-beta) given significance level (alpha), variance estimations and projected ratio of unequal sample sizes (k). Mean EROD activity and standard error were estimated at each of 82 sampling stations. The inter-individual variance component was dominant in estimating the variance of mean EROD activity. Influences of alpha, beta, k and variability on sample sizes are illustrated and discussed in terms of costs. In particular, sample sizes do not have to be equal, especially if such a requirement would lead to a significant cost in sampling extra material. Finally, the feasibility of longterm monitoring is discussed.