Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/1995
Publication Date: N/A
Interpretive Summary: Malignant Catarrhal Fever (MCF) is a fatal disease of cattle and some other ruminants such as deer and bison. MCF is caused by a herpesvirus. In Africa, the wildebeest is playing a major role of harboring the virus in nature. In other parts of the world, sheep are believed to be the source of infection. Wildebeest and sheep can be infected with the virus, but never exhibit symptoms. When the infection comes from sheep, it is referred to as sheep-associated MCF (SA-MCF). In the US, most MCF outbreaks were caused by a SA-MCF virus, as a result of sheep and cattle being together. Study of MCF has been hampered by the lack of accurate diagnostic tests. Recently, we have developed a test (CI-ELISA) to detect MCF antibody in cattle and sheep (published). In this publication, we report the development of a polymerase chain reaction (PCR) technique to detect SA-MCF virus DNA in sheep. The tests accurately identify infected sheep and confirm SA-MCF in cattle or deer. With these two tests, we have surveyed a large number of sheep from 8 states and found high percentages (94-99%) of adult sheep are infected with the virus. We also found the virus is readily detectable by PCR in the colostrum and milk of infected ewes. These data are extremely useful for the study of transmission of the virus, which is currently underway.
Technical Abstract: In this communication, a recently developed competitive-inhibition ELISA and a PCR were used to detect anti-MCF virus antibody and SA-MCV DNA in sheep and other ruminants. of 144 samples from randomly-selected normal adult sheep, 143 (99%) were positive by PCR and 136 (94%) were positive by CI-ELISA. The agreement between the two assays exceeded 95%. Of 9 samples scollected from cattle and deer with clinical MCF of apparent sheep origin, 7 were CI-ELISA-positive and all 9 were PCR-positive. Among 59 presuckle lamb sera, none contained antibody detectable by CI-ELISA. After suckling, maternal and anti-MCFV antibody was detectable for about 10 (+/-3) weeks. Although all colostrum and mink samples from infected ewes were strongly PCR-positive, the appearance of detectable SA-MCFV DNA in lambs was correlated generally with antibody patterns, which suggest that the natural infection event in sheep may not occur during the peri-natal period, but sometime later in life.