Sodium Chlorate, A Potential Treatment of Salmonella in Pigs?

By Wayne Du, Swine Advisory Team, OMAFRA - Salmonella is one of the main foodborne pathogens associated with meat and meat products. A recent study conducted by USDA scientists showed that when fed in low doses, sodium chlorate kills Salmonella typhimurium and E. coli O157:H7 in pigs and cows.
calendar icon 26 June 2001
clock icon 5 minute read
From the
May/June 2001
News & Views

Pork News and Views is prepared by the Swine Advisory Team of the Ontario Ministry of Agri- culture, Food and Rural Affairs

Editor: John Bancroft
Clinton OMAFRA,
Salmonella are very important bacteria to study because they cause Salmonellosis in animals and poultry, and are one of the main foodborne pathogens associated with meat and meat products.

In the U.S., there are approximately 1.4 million cases of human Salmonellosis and 600 deaths are reported due to Salmonella-related food poisoning each year. In swine, clinical Salmonellosis is common and it causes great economic losses to the pork industry.

An American study showed that two thirds of swine operations in some states are Salmonella positive. Salmonella typhimurium DT 104 is the type of Salmonella that causes human sickness or even death. Data from the Animal Health Laboratory of the University of Guelph showed that from January to September 1999, there were 19 swine herds that were diagnosed with Salmonella typhimurium DT 104 in Ontario. Gut and affiliated lymph tissues are the primary reservoirs for Salmonella in pigs.

The bacteria can be passed onto carcasses at the packing plants due to fecal spillage during evisceration. Since the gut is a major reservoir for Salmonella, to reduce their concentration in pigs at the farm level and before processing is one of the very critical control steps that should be taken. Fewer Salmonella in the gut and feces can significantly reduce the chance of carcass contamination at packing plants and, therefore, result in safer pork.

A recent laboratory study (Journal of Food Protection, 2001), conducted by USDA scientists in Texas, demonstrated that when fed in low doses, sodium chlorate kills Salmonella typhimurium and E. coli O157:H7 in pigs and cows.

This finding provides a potential practical approach for reducing on farm concentrations of these pathogens. How does sodium chlorate work to kill the bugs? Salmonella and E. coli O157:H7 contain an enzyme known as a respiratory nitrate reductase.

This enzyme coincidentally converts the chlorate (ClO3-), an analog of nitrate, to chlorite (ClO2-), which will, in turn, kill Salmonella and E. coli.

Since beneficial bacteria in the intestinal tract don’t have respiratory nitrate reductase, they are not affected by the addition of chlorate. In two separate experiments, a total of 45 of the 26 to 29 day old weaned pigs were infected orally with 8 x 107 CFU of Salmonella typhimurium. The pigs were randomly placed into respective treatment groups and kept in separated pens. The pigs in each treatment group were then fed up to 0.04 grams sodium chlorate per kilogram of body weight at 8 and again 16 h later after Salmonella infection.

The pigs were put down at 8-h intervals (five per group) after receiving the last treatment of sodium chlorate and fecal samples collected by necropsy were cultured qualitatively and quantitatively for Salmonella and other bacteria.Results from the experiments showed that a significant chlorate treatment effect on fecal Salmonella concentration occurred with the largest reduction observed 16 h after receiving the last chlorate treatment.

Within 16 h, sodium chlorate treatment produced a 150-fold reduction in the number of Salmonella in the intestines. There was also a treatment by time interaction observed suggesting that the chlorate effect was concentration dependent. The research is still in the early stage and this new approach needs to be approved by FDA before it can be widely used by the livestock industry in the U.S. Possible applications include feeding chlorate to animals before they are transported to slaughter or adding it to drinking water before loading or at lairage.

Further reading in the May/June 2001 Pork News and Views:

Pork News & Views

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