BLUETONGUE VIRUS STUDIES* JI. COMPLEMENT FIXING ANTIBODY RESPONSE IN EXPERIMENTALLY 

 INFECTED CATTLE, SHEEP AND DEER Carbrey, E. A., Gustafson, G. A. and Lee, L. R. (Project Report) 



Summary 



Two sheep and three cattle were infected with bluetongue (BT) virus and the complement-fixing antibod\ 

 titers were determined at weekly intervals for 719 and 594 days, respectively. Peak titers of 1-80 and 1-160 were 

 detected in both sheep and cattle at 40 to 50 days postinoculation (DPI). At the termination of the experiment the 

 sheep had persistent titers of 1-40 while the titers of the cattle had fallen to 1-5 and 1-10. 



Serums from deer infected with epizootic hemorrhagic disease (EHD) were, tested against BT mouse brain 

 antigen using the complement fixation test. The tests were negative indicating a lack of identity between BT and 

 EHD virus. However, a consistent 20 percent fixation of complement was detected at the 1-5 dilution. This was 

 considered evidence for a slight degree of antigenic relationship between the two viruses. 



Introduction 



The export of cattle and sheep to foreign countries provides an important source of income to livestock 

 breeders. Other countries are concerned that these animals do not introduce new disease agents into their livestock 

 populations. Bluetongue (BT) is a disease not found in many countries of the world, for instance, Canada, Great 

 Britain, Australia, New Zealand and Brazil. Before our cattle and sheep are permitted to enter these countries, thev 

 must be certified as free of BT infection. The development of a reliable test for the detection of complement fixing 

 antibodies against BT virus (1, 2, 3) 1 provided a serologic method for detecting previously infected animals. Some of 

 the countries that were anxious to import our cattle and sheep agreed to accept those that were negative to the 

 complement-fixation (CF) test. 



Although the complement fixing antibody response to BT infection was well documented, information was 

 not available on the duration of the titers detected or their relationship to a persistent viremia. This paper will 

 describe experiments performed on experimentally infected sheep and cattle which were maintained in strict 

 isolation for 719 and 594 days, respectively. During these periods the complement-fixing titers of these animals were 

 determined at weekly intervals. 



Serums from deer previously infected with BT and epizootic hemorrhagic disease (EHD) 2 were tested for 

 complement fixing antibodies against BT to determine the degree of cross reaction produced by these closely related 

 viruses. 



Materials and Methods 



Virus Strains.— Bluetongue virus strain California BT8, 10th sheep passage was obtained by bleeding an 

 infected sheep 6 days postinoculation (DPI). It was supplied 3 in an anticoagulant preservative solution, OPG. 

 California (type 10) BT virus mouse brain passage was obtained as freeze dried mouse brain. 5 



Experimental Animals.— Sheep were obtained from two closed flocks located in Iowa that had been tested and 

 found negative for BT by the CF test. All sheep were tested before inoculation and found negative. 



Cattle were obtained from the laboratory herd that has been tested regularly and found free of BT infection. 



All animals were maintained in strict isolation. Sheep used for virus isolation were maintained in plastic 

 isolation cages provided with a negative air pressure. 



Complement Fixation Test.— The test was performed according to the method of Boulanger, ef al. as 

 previously described. (2) 



Numbers in parentheses refer to References at the end of this report. 



Supplied by Dr. F. C. Thomas, University of Wisconsin. Madison, Wis. 



Supplied by Dr. M. M. Jochim. Animal Disease Research Laboratory, ARS, USDA. Federal Center, Denver. Colo. 80225. 

 OPG solution: potassium oxalate, 5 gm., phenol 5 gm., glycerin. 500 ml. and distilled water. 500 ml. 



Supplied by Dr. Paul Boulanger, Animal Pathology Division. Health of Animals Branch, Animal Diseases Research Institute. 

 Hull, Quebec, Canada. 



