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Hot on the Tail of Poultry KillerBy Jill Lee
February 25, 1999
Not all forms of Salmonella make people sick. Some kindsnot harmful to humansstrike poultry flocks and damage farm profits. For years, scientists have misunderstood one poultry-killing strain of Salmonella. Now a U.S. Department of Agriculture researcher has found a way to track this bacteria more effectivelyand in the process has overturned 60 years of accepted research about the microbe.
For years, scientists said Salmonella pullorum lacked the ability to propel itself through blood and other fluids because it lacked whip-like tail fibers known as flagella. A special growth medium helped a scientist with USDAs Agricultural Research Service discover that the microbe did, indeed, have flagella.
Most strains of salmonella have thick, strong flagella. But pullorum has fine, feather-like flagella. A new growth medium made the pullorum grow flagella to detectable levels. Adapted staining procedures also made them more visible. The discovery was confirmed with an electron microscope.
Knowing pullorum possesses these propelling tails will lead to better detection methods. When a chickens body recognizes foreign invaders like pullorum, it starts making antibodies--special proteins that fight the infection. Flagella cause the body to react by releasing more and different kinds of antibodies, making detection easier. Early detection means an outbreak is more easily contained.
Pullorum devastated the U.S. poultry industry shortly after the turn of the century. USDA has been part of a successful national control effort since the 1930s, although serious and expensive outbreaks still occur sporadically in the U.S. In developing countries, pullorum disease remains a widespread problem and exacts a heavy economic toll on the poultry industry. The disease is passed from hens to eggs. It kills chicks in the first weeks of life.
ARS is the USDAs chief scientific agency.