Experimental Procedure.— Two sheep and three calves were each inoculated i.m. with 4.0 ml. of 50 percent 

 sheep blood in OPG and maintained in isolation rooms for the duration of the experiment. Rectal temperatures were 

 determined during the acute phase of the disease at daily intervals. Serums for the CF test were collected at 

 approximately weekly intervals. Blood samples for packed cell volume (PCB) and white blood cell determinations 

 were obtained daily during the acute phase. 



Following the acute phase the animals remained in good health except for one calf that was severely injured 

 when it caught its foot under a gate. The sheep were maintained for 719 and the cattle for 594 days. At the 

 termination of the experiment and at periodic intervals, blood was collected and inoculated into susceptible sheep to 

 determine whether any of the animals had a persistent BT viremia. Usually 20 ml. of blood was collected; however, 

 at the termination of the experiments 500 ml. of blood was obtained from each sheep and 1000 ml. from each calf. 

 The test sheep were inoculated with the washed cells obtained from these samples. 



Serums were obtained from deer experimentally infected with BT virus, vaccine strain. Other deer were given 

 two inoculations of EHD virus subcutaneously with an interval of 2 weeks between inoculations. Serums were 

 collected 2 weeks after the second inoculation (4). 



Results 



Sheep.— Following exposure to BT virus the two sheep each had a marked increase in rectal temperatures to 

 41.2° C. (106.0° F.) and 40.6° C. (105.0° F.) on DPI, four and six. The only additional clinical sign detected was 

 edema of the lips. Complement fixation titers of 1-5 and 1-20 were first detected 20 DPI and titers of 1-80 and 

 1-160 were attained at 40 DPI. The titers gradually receded but remained well above the critical diagnostic level of 

 1-20 through 461 DPI. At this time 20 ml. of blood were obtained from each sheep and inoculated into susceptible 

 sheep to check for the presence of BT virus. The inoculated sheep remained negative to the CF test. At the 

 termination of the experiment, at 719 DPI, the sheep had titers of 1-40. Large blood samples of 500 ml. were 

 collected and the cellular elements were inoculated into susceptible sheep. Serologic evidence of BT infection was 

 not detected. 



Three Holstein calves, two heifers and a bull, were inoculated with BT virus. A severe leukopenia and slight 

 pyrexia was detected at 5 DPI and a second period of illness was observed from 10 - 13 DPI. At 13 DPI serum 

 obtained from the calves was negative by CF test; however, by 20 DPI two of the calves had titer, 1-5 and 1-10. By 

 55 DPI titers of 1-80 and 1-160 were found and the titers persisted at this level through 150 DPI (fig. 1). At this 

 point the titers began to decrease and by 319 DPI had fallen to 1-10 in two of the animals and 1-40 in the third. 

 Eventually at 468 DPI the titers dropped below the minimum designated positive titer of 1-20 and remained in the 

 suspicious level of 1-5 and 1-10 through the termination of the experiment at 594 DPI. 



Attempts were made to recover BT virus from the blood of the calves at 320 and 550 DPI. At 320 DPI 20 ml. 

 of blood from each calf was inoculated into a susceptible sheep and at 550 DPI the cellular elements of 1000 ml. of 

 blood were inoculated. The inoculated sheep remained healthy and failed to develop any detectable titers to the CF 

 test. 



The rate of change in the mean titers (slope) was calculated and found to be a log titer decrease per day of 

 0.0021684 (fig. 1). This corresponded to approximately one dilution decrease in CF titer every 6 months. 



The standard error of the CF test as measured by the application of analysis of variance of the data was a log 

 titer of 0.4364 or slightly more than a twofold dilution. With a system of statistical analysis in which dummy 

 variables were employed, significant differences were found in the overall antibody response of two of the three 

 calves. 



The CF test was performed on serums collected from deer before and after experimental infection with either 

 BT or EHD. The serums from the BT infected deer had titers of 1-20 while the serums from the EHD infected deer 

 were negative at the 1-5 dilution (table 1). 



A minimal fixation of complement, approximately 20 percent, was consistently detected in the 1-5 dilutions 

 of the serums from the EHD infected deer. 



This titration was performed as a blind study using coded serums. 



