Differential Serologic Response to Mycoplasma Ovipneumoniae and Mycoplasma Arginini in Lambs Affected with Chronic Respiratory Disease

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniaeand M. arginini in lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniaeand M. arginini whole cells and a crude capsular extract of M. ovipneumoniae as the antigens. There were low levels of antibody to M. ovipneumoniae in flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently re- covered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniae were confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. arginini were more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae. Mycoplasma ovipneumoniae (MO) is one of the most commonly isolated microorganisms from sheep with respiratory disease worldwide. 4 Recently in this laboratory, this microorganism and M. arginini (MA) have been routinely recovered from young lambs with a respiratory disease that has been termed the ''cough- ing syndrome.'' The condition is associated with a se- vere paroxysmal cough, leading to rectal prolapses. This syndrome is widespread in the midwestern states of the USA, with morbidity and severity variable among flocks. The disease is chronic and persists for several weeks in most affected lambs. There is some evidence that the extended persistence of the MO or- ganism in the respiratory tract of these lambs and the chronic nature of the disease may be due to failure of the immune system to generate protective immunity. 10