Detection of complement fixing antibodies against foot-and-mouth disease in cattle serum.

Abstract

The complement fixation test has become of considerable value in the early diagnosis of foot-and-mouth disease (F and M) in cattle and in typing the virus from this disease. However, this method is less useful in later stages of the disease when infected tissue can no longer be obtained for antigen. Furthermore, it is difficult to detect complement fixing antibodies in serums from convalescent cattle when using conventional procedures. Therefore, many attempts have been made to improve the sensivitity of the test. These modifications of the complement fixation test have included the use of unheated serum (Fredericks, 1949) or performance of the entire test at higher salt concentration (Serra and Guarini, 1951). None of these have proved to be successful. An indirect method for demonstrating antibodies in late convalescent F and M serums has been suggested by Rice and Brooksby (1953). The indirect complement fixation test had earlier been applied by Rice (1948) in detecting antibodies in anti-pullorum serums, by Wolfe (1949) in anti-Newcastle disease serums, by Karrer et al (1950) and Hilleman et al (1951) in anti-ornithosispsittacosis, and by Downie et al (1950) in anti-variola serums from chickens. Rice and Boulanger (1953) have also used it to demonstrate antibodies against vesicular viruses in cattle, and Rice and McKercher (1954) in studies of vesicular stomatitis in horses, cattle and swine. The difficulty with the indirect test is its relative complexity, and it is time consuming. A simple modification of the F and M complement fixation test was described by Nordberg and Schjerning-Thiesen (1953) in a preliminary report. These workers were able to demonstrate antibodies against F and M in the serums of three hyperimmunized and seven convalescent cattle when a conventional test was employed but with temporary hypertonization of the serum component alone. The present report describes studies on a larger series of convalescent and vaccinated cows and presents the procedure in greater detail.