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Fourteen strains of Yersinia species isolated from apparently healthy pigs and cattle in Nigeria were screened for four virulence markers using six test systems. These were two in vitro assays, namely, calcium dependency and autoagglutination, both at 37 degrees C, the Serény test in guinea-pigs and the detection of heat-stable enterotoxin (ST) by the rabbit ileal loop test, the ligated intestine test in pigs and the infant mouse system. Seven of the 14 strains of Yersinia were positive for one or more of these tests. Six of nine strains of Y. enterocolitica and one of four Y. intermedia were positive in one or more tests. The only strain of Y. frederiksenii isolated was negative in all six test systems. All three strains of Y. enterocolitica, serotype 0:8 and the only serotype 0:3 isolated were positive in one or more tests. However, only two of five strains of Y. enterocolitica serotype 0:12, 26, the most frequently encountered, were positive. A good correlation was observed between test results of calcium dependency, autoagglutination and Serény assays. The results indicate that cattle and pigs have the potential to transmit virulent strains of Y. enterocolitica to human beings in Nigeria.

Water samples obtained from 250 wells, 118 ponds and 34 streams around Zaria, Nigeria were cultured for Yersinia enterocolitica. All samples tested were negative for the microorganism. Water samples from the three sources experimentally inoculated with three strains of Yersinia enterocolitica allowed an initial multiplication followed by a progressive decline in population with increase in population paralleling increase in ambient temperature. Well water was most supportive of the organism but strain variability in survival was observed in water from the three sources. Stream, pond and well water may not be important in the epidemiology of Y. enterocolitica infections in animals and human beings in Northern Nigeria.