Anne Peasey

Guidelines for the microbiological quality of treated wastewater used in agriculture: recommendations for revising WHO guidelines.

Three different approaches for establishing guidelines for the microbiological quality of treated wastewater that is reused for agriculture are reviewed. These approaches have different objectives as their outcomes: the absence of faecal indicator organisms in the wastewater, the absence of a measurable excess of cases of enteric disease in the exposed population and a model-generated estimated risk below a defined acceptable risk. If the second approach (using empirical epidemiological studies supplemented by microbiological studies of the transmission of pathogens) is used in conjunction with the third approach (using a model-based quantitative risk assessment for selected pathogens) a powerful tool is produced that aids the development of regulations. This combined approach is more cost-effective than the first approach and adequately protects public health. The guideline limit for faecal coliform bacteria in unrestricted irrigation (< or = 1000 faecal coliform bacteria/ 100 ml) is valid, but for restricted irrigation < or = 10(5) faecal coliform bacteria/100 ml is recommended when adult farmworkers are exposed to spray irrigation. A limit of < or = 10(3) faecal coliform bacteria/100 ml is recommended if flood irrigation is used or children are exposed. The guideline limit for nematode eggs for both types of irrigation is adequate except when conditions favour the survival of nematode eggs and where children are exposed; in these cases it should be reduced from < or = 1 egg/l to < or = 0.1 egg/l.

Seroepidemiology and Risk Factors for Sporadic Norovirus/Mexico Strain.

Risk factors associated with transmission of sporadic norovirus (NV; formerly Norwalk-like virus)/Mexico strain were identified in a seroepidemiological study conducted in rural Mexico. Acquisition of Mexico strain IgA antibodies was age-related; 34% of 1-4-year-olds were seropositive, compared with 81% of adults (P<.001). After 12 months, 42% of 1-4-year-olds showed a seroresponse to Mexico strain, compared with 27% of adults (P<.01). Personal and domestic hygiene measures, such as hand washing, general cleanliness of the mothers clothing, and the type of room assigned for cooking were significantly associated with odds of a seroresponse. For infants, having a dog in or near the home was a risk factor for seroresponse (P<.01), whereas, for older children, the mothers involvement in agricultural activities was a risk factor (P<.001). This study provides initial evidence of risk factors associated with sporadic NV infection. Data indicate some similarities to risk factors associated with outbreaks of NV infection.