Serodiagnosis in Q fever with special emphasis on the radioisotope precipitation test.

Abstract

A study of persons associated with dairy herds serologically positive for Q fever was carried out in seven counties of central Ontario in 1964–65 to determine the extent of exposure of such persons to Q fever rickettsiae. Milk samples from 2206 dairy herds (= premises) were first tested by the capillary tube agglutination (CA) technique and 639 (29%) were found positive. This is double the herd incidence of Q fever found in a survey carried out in this area 5 years earlier.Of these 639 positive premises, 406 were visited in 1965 and blood obtained from 371 volunteers (contact population). Random serum samples of 862 adult persons from the seven counties were obtained from specimens submitted to the Peterborough laboratory for syphilis serology (general population). All human sera were tested and 43.1%found positive by the radioisotope precipitation (RIP) test, 34.6% by the complement fixation (CF) test, and only 3% by the capillary tube agglutination (CA) test. In contrast, the RIP test was positive in 2% of the sera of the general population, the CF test in 1.4%, and the CA test in only 0.4%.These results show that subclinical infection is common among persons having frequent contact with dairy cattle infected with Q fever. The study also demonstrated the high degree of sensitivity of the RIP test.