New research reported by Kim Cook, a microbiologist at the Agricultural Research Servicein Bowling Green, Kentucky, shows the best way to prevent the spread of Johne’s disease on dairy farms is to use stainless steel water troughs and add chlorine to the water.
Johne’s disease is caused by Mycobacterium paratuberculosis and can cause losses of as much as $200,000 per year in a herd of 1,000 dairy cows. The losses are mostly from a drop in milk production and the need to isolate infected animals. The continued increase in the prevalence of Johne’s disease among dairy cattle prompted Dr. Cook’s investigation.
In an effort to find the source of the infection, Dr. Cook’s team examined water troughs as potentialbreeding environments for bacteria. Cook and her researchers counted the mycobacteria in the water on the sides of the most commonly used troughs: concrete, plastic, stainless steel, and galvanized steel. They wanted to see if bacteria would adhere to and survive on the surfaces of different materials for varying lengths of time.
Within three days of inoculating the water, Cook found high concentrations of the bacteria on all troughs, and they survived for more than 149 days. But the bacterial survival rate was lowest on the stainless steel.
When the researchers added three tablespoons of chlorine bleach per 100 gallons of trough water a week, they found that less than one percent of the bacteria remained on stainless and galvanized steel troughs by the end of the third week. In contrast, 20 percent of the bacteria remained on the plastic troughs, while 34 percent of the bacteria remained on the concrete troughs.
Historically, U.S. drinking water was first chlorinated in 1908 when engineer George A. Johnson added chlorine to polluted livestock feed water in Chicago’s Union Stockyards.Bacterial counts plummeted immediately and it was noted that the quality of the livestock water surpassed that of city water. Later that year, Jersey City became the first U.S. city to chlorinate its drinking water, with the result that deaths due to typhoid fever and other waterborne diseases declined dramatically. By the 1920s, chlorination was well-established as the primary means of disinfecting drinking water and it had been adopted by most American cities to the great benefit of public health. Chlorination is by far the most common method of disinfecting public water supplies today.
(Joan Rose, PhD, is the Homer Nowlin Chair in Water Research at Michigan State University and a member of the Water Quality & Health Council.)