INVESTIGATION OF SHEEP-ASSOCIATED MALIGNANT CATARRHAL FEVER VIRUS-INFECTION IN RUMINANTS BY PCR AND COMPETITIVE-INHIBITION ENZYME-LINKED-IMMUNOSORBENT-ASSAY

Development of control measures for the gammaherpesviral disease of ca ttle known as sheep-associated malignant catarrhal fever (SA-MCF) has been hampered by a lack of accurate diagnostic tests either for the ca usative virus or for antibody against that virus. A recently developed competitive-inhibition enzyme-linked immunosorbent assay (CI-ELISA) f or the detection of antibody to malignant catarrhal fever (MCF) virus (MCFV) in ruminants based on a monoclonal antibody to a widely conserv ed epitope of MCFV (H. Li, D, T, Shen, D. P, Knowles, J, R Gorham, and T. B. Crawford, J. Clin, Microbiol, 32:1674-1679, 1994) and a PCR ass ay based on previously reported primers (S, I, F, Baxter, I, Pow, A Br idgen, and H, W. Reid, Arch. Virol. 132:145-159, 1993) were used to de tect anti-MCFV antibody and SA-MCFV DNA in sheep and other ruminants, The PCR amplified a specific 238-bp SA-MCFV genomic DNA fragment from peripheral blood lymphocytes of adult sheep and other ruminants with c linical MCF, Of 144 samples from randomly selected healthy adult sheep , 143 (99%) were positive by PCR and 136 (94%) were positive by CI-ELI SA, The agreement between the two assays exceeded 95%. Of nine samples collected from cattle and deer with clinical MCF of apparent sheep or igin, seven were CI-ELISA positive and all 9 were PCR positive. Among 59 serum samples from presuckling lambs, none contained antibody detec table by CI-ELISA, After suckling maternal anti-MCFV antibody was dete ctable for about 10 +/- 3 weeks, Although all colostrum and milk sampl es from infected ewes were strongly PCR positive, the appearance of de tectable SA-MCFV DNA in lambs was correlated generally with antibody p atterns, which suggests that the natural infection event in sheep may not occur during the perinatal period hut occurs sometime later in lif e.