Edwin C. Lippy

An outbreak of waterborne giardiasis associated with heavy water runoff due to warm weather and volcanic ashfall

From mid-June through early August 1980, an outbreak of gastrointestinal illness in Red Lodge, Montana affected approximately 780 persons, as estimated from attack rates of 33 per cent and 15 per cent in urban and rural residents, respectively. Giardia lamblia was identified in stool specimens from 51 per cent of 47 persons with a history of untreated gastrointestinal illness and in 13 per cent of 24 specimens from asymptomatic persons (p = .00045, Fishers Exact Test). The epidemic curve was bimodal with peaks in mid-June and mid-July. Each peak occurred about three weeks after an episode of very heavy water runoff resulting from warm sunny weather and snow darkened by ashfall from the Mt. St. Helens volcanic eruption of May 18, 1980. Unfiltered and inadequately chlorinated surface water was supplied by the city water system, which was implicated as the vehicle of transmission in the outbreak. Water systems providing unfiltered surface water are more likely to become contaminated during periods of heavy water runoff.

Endotoxins, algae and Limulus amoebocyte lysate test in drinking water

Abstract Field and laboratory studies were conducted to determine the distribution of algae and bacteria, and investigate sources of endotoxins (lipopolysaccharides) in drinking water. The field survey was performed on five drinking water systems located in Allegheny County, Pennsylvania during the spring and summer of 1978. The highest concentrations of phytoplankton were found in uncovered finished water reservoirs. The major source of “endotoxic” response as measured by the Limulus amoebocyte lysate (LAL) gelation test was a non-specific reaction caused by algae. This was documented by a highly positive correlation of phytoplankton concentrations occurring in the reservoirs with respective LAL titers. Chlorella vulgaris (Chlorophyta) was the most common alga, whereas Schizothrix calcicola was the most dominant Cyanobacterium found in the five water systems. LAL gelation test with C. vulgaris grown in the laboratory verified the phenomenon observed on samples collected in the field and indicated a non-specific reaction, whereas S. calcicola cultures under identical conditions produced a specific response. Alkali and lysozyme treatments were successful in distinguishing specific and non-specific LAL reactions. These two techniques in conjunction with LAL test are recommended for drinking water quality assessment.