Trimethoprim and sulfadiazine: experimental infection of Beagles.

The purpose in the present study was to determine whether the commercial combination of trimethoprim (TMP) and sulfadiazine (SDZ) tribrissen (TRI) was more effective than either of the components for treating experimentally induced infection of Streptococcus zooepidemicus. Two dose levels of each were given subcutaneously for treatment, and their effectiveness was compared with that of sulfadimethoxine (SDM) in terms of (i) clinical manifestations, (ii) hematologic changes, (iii) blood culture examinations, and (iv) tissue culture examinations. According to these four measurements, the combination TMP/SDZ was more effective than either of the components. This effect was observed at the two dosages of TRI (30 and 15 mg/kg). The higher dosage, however, was more effective as demonstrated by three of the measurements. Alone, TMP and SDZ were not effective, but SDM treatment was effective in this model.

Effect of bovine alpha 1 interferon on bovine herpesvirus type 1-induced respiratory disease.

Treatment of calves with bovine recombinant alpha 1 interferon prior to challenge with bovine herpesvirus type 1 increased the animals' ability to withstand a subsequent Pasteurella haemolytica challenge. The reduction in viral-bacterial synergy observed following interferon treatment did not appear to be due to a direct effect of the interferon on virus replication in the upper respiratory tract. Thus, even though interferon-treated animals shed slightly less virus from their nasal passages than did untreated animals, this reduction was not statistically significant. Furthermore, there was no difference in the level of intranasal interferon secreted by control or interferon-treated animals. These results suggest that interferon treatment does not affect the production of endogenous interferon. In contrast, a significant difference was observed between the number of days that control animals were sick, the levels of serum fibrinogen and the functional activity of polymorphonuclear neutrophilic granulocytes obtained from infected calves. These results suggest that bovine recombinant alpha 1 interferon may have a greater immunomodulatory effect than a direct antiviral effect in this model. This is further supported by the observation that bovine herpesvirus type 1 is relatively resistant to the direct antiviral effect of bovine recombinant alpha 1 interferon in vitro.

Levels of interferon in blood serum and toxicity studies of bacteria-derived bovine alpha I1 interferon in dairy calves.

This paper reports information on the levels of interferon (IFN) in the blood serum of dairy calves given 10(6) U of bacteria-derived bovine alpha I1 interferon per kg of body weight by intravenous (i.v.), intramuscular (i.m.), subcutaneous (s.c.), and intranasal (i.n.) routes. Highest levels (10,000 U/ml) in the vesicular stomatitis viral assay system were obtained after i.v. administration and occurred within 30 min of a dose; levels rapidly declined thereafter to a low of 200 to 300 U/ml by 24 h. Serum inhibitory activity against vesicular stomatitis virus in this range is sometimes found in normal dairy calves. Levels after i.m. and s.c. administration were similar: a plateau of 1,000 to 2,000 U/ml between 2 and 8 h after a treatment with a decline to 200 to 300 U/ml by 24 h. Serum IFN was not detected after i.n. dosing or in the control group given physiological buffered saline by the i.m. route. A transitory moderate febrile response, but no other clinical adverse effects, was noted after the first intramuscular dose of IFN, but not after subsequent i.m. doses. No clinical signs were noted after i.v., s.c., or i.n. dosing or in the control calves given physiological buffered saline intramuscularly. After i.v., s.c., and i.m. administration of IFN, leukopenia, neutropenia, and lymphocytopenia were observed; these were most prominent within the first 24 h after the initial dose of IFN.