Omar Oyarzabal, Donald Conner, James Barbaree, and Irene Wesley

AAES researchers, working with the U.S. Department of Agriculture's National Animal Disease Center (USDA-NADC) in Ames, Iowa, have developed a rapid, specific procedure for the diagnosis of Campylobacter fetus, a bacterium that infects humans and cattle and poses risks to human health and can cause severe economic loses for cattle producers.

C. fetus has been divided into two subspecies: C.fetus subsp.fetus and C. fetus subsp. venerealis. Although infrequent, human foodborne outbreaks of C. fetus subsp. fetus have resulted from the consumption of raw beef, raw milk, and cottage cheese. In a two-year surveillance study, from 1987 to 1989, the Centers for Disease Control and Prevention (CDC) reported 122 human cases of C. fetus subsp. fetus. In cattle and sheep, C. fetus subsp. fetus is transmitted orally. The organism disrupts the placenta, induces abortion, and produces infertility.

There is no report of human infection due to C. fetus subsp. venerealis. This microorganism is regarded exclusively as a venereal pathogen of cattle.

Trade restrictions prohibit the export of bulls carrying C. fetus subsp. venerealis. Typically, diagnosis of C. fetus subsp. venerealis is accomplished by observing clinical signs of infection or by examining samples of cervical mucus, preputial washings, or intestinal contents of aborted fetuses under a highpowered microscope. Unfortunately, it is easy to confuse C. fetus subsp. venerealis with similar nonpathogenic bacteria. Biochemical testing also can be used to detect C. fetus, but this method is time consuming and imprecise. Finding a more specific and rapid method to detect C. fetus would speed up testing for the bacterium and also help laboratories avoid potential confusion of dangerous organisms with harmless organisms.

AAES scientists joined forces with researchers at USDA-NADC to develop such a test, which uses a polymerase chain reaction (PCR) technique and amplifies DNA to detect both subspecies of C. fetus. The PCR technique separates the DNA from Campylobacter-like bacteria. These samples can be used immediately for testing or can be frozen for several weeks for later evaluation. The PCR technique can yield reliable identification of C. fetus within three hours after isolation of suspicious colonies on agar plates.
This work provides a powerful tool to investigate a disease that results in both a loss in animal production and a risk in human health. This technique can help expand knowledge of the transmission and epidemiology of this bacterial pathogen.