The incidence of antibody to infectious bovine rhinotracheitis virus in Kenyan cattle.

A total of 3204 cattle sera, collected between 1966 and 1974, from all seven provinces and 34 of the 42 districts of Kenya were screened in a neutralisation test for antibody to infectious bovine rhinotracheitis virus (IBRV). Antibody to IBRV was found in some sera from all the districts, with cattle over two years old showing the highest incidence. A small number of goat sera also showed some antibody. From the results obtained it is concluded that IBRV infection is widespread in Kenyan cattle.     

Experimentally induced foot rot in feedlot cattle fed rations containing organic iodine (ethylenediamine dihydriodide) and urea.

Foot rot was experimentally induced in feedlot cattle with a mixed inoculum of Fusobacterium necrophorum (Sphaerophorus necrophus) and Bacteroides melaninogenicus. Both bacteria were isolated from the lesions. Isolates of F necrophorum from 2 of the lesions were serologically compared, using a passive hemagglutination test with the strain used to induce the lesions. These isolates were serologically similar but not identical, indicating antigenic change had occurred during animal passage. The addition of ethylenediamine dihydriodide or urea to the rations did not affect the frequency of experimentally induced foot rot.     

Evaluation of inactivated infectious bovine rhinotracheitis vaccines.

Sixty-five calves of approximately three months of age and of mixed sex were vaccinated twice at four week intervals with either attenuated or inactivated infectious bovine rhinotracheitis vaccines. Following initial vaccination there was no demonstrable serum infectious bovine rhinotracheitis titer in any of the calves receiving the inactivated vaccine with 20.7% of the calves receiving the attenuated vaccines having demonstrable titers. Following a second administration of vaccine at eight weeks post-initial vaccination 63.9% of the calves receiving the inactivated vaccine had no demonstrable titer with 72.4% of the calves receiving the attenuated vaccine exhibiting a blood titer of four or greater.     

Clinical and immunologic responses of cattle to infectious bovine rhinotracheitis virus after infection by viral aerosol or intramuscular inoculation.

Aerosol or intramuscular exposure to infectious bovine rhinotracheitis virus elicited generally comparable levels of serum antibody in cattle, but not measurable nasal secretion antibody. Aerosol-exposed cattle developed signs of mild clinical disease, fever, and leukopenia and shed virus from their nasal passages. Cattle exposed by intra-muscular inoculation developed a brief febrile response and leukopenia but did not shed virus. After an aerosol challenge exposure, cattle in each group developed detectable nasal secretion antibodies, but no clinical signs of disease.     

In vitro induction of cytotoxic lymphocytes from infectious bovine rhinotracheitis virus hyperimmune cattle

Cytotoxic lymphocytes against infectious bovine rhinotracheitis virus (IBRV)-infected cells were induced by in vitro stimulation with IBRV antigen of peripheral blood leukocytes obtained from hyperimmune cattle. After one in vitro stimulation with IBRV, cytotoxicity was detected against IBRV-infected autologous target cells, but not against heterologous IBRV-infected or K562 target cells. After 4 in vitro IBRV stimulations at weekly intervals (in the presence of autologous feeder cells followed by interleukin 2 treatment at 2-day intervals), cytotoxicity was detected against autologous-, and to a lesser extent, heterologous-infected cells. Most cells in cytotoxic cultures were positive to a monoclonal antibody shown to react with bovine T lymphocytes.