| decreasing prevalence of q fever in illinois. | there were 858 (37.7 percent) q fever-infected dairy herds among the 2,277 tested in illinois in 1963. the percentage decreased to 19.2 percent (380 of 1,975) in 1967. reaction rates (complement-fixation test titer of 1:8 or greater) in serum samples from veterinarians decreased from 13.3 percent in 1956 to 3.9 percent in 1964 and from 3.6 percent in 1966 to 0 percent in 1968, 1970, 1972. there were 14 (2.7 percent) reactive serum samples among 526 abattoir workers tested in 1966; reaction rates ... | 1982 | 7063599 |