Studies show a variation in thefrequency of adhesins and differ in interpretation regardingthe relationship between the adhesin and the disease. Ewerset al.observed a variation between 7 and 100% of pfhAaccording to the host species and related its presence to theoccurrence of pasteurellosis in cattle. Similarly, Bethe et al.connected pfhA with the occurrence of respiratory disease inswine. However, Shayegh et al.detected a low frequency(18%) of the gene among ovine strains and did not relate itwith pasteurellosis in this species.