Salivary glands from males of 3 Dermacentor species (D andersoni, D variabilis and D occidentalis) that were infected with either the Virginia or Idaho isolate of Anaplasma marginale as nymphs or adults were examined for colonies of A marginale by use of light and electron microscopy. Prior to dissection of salivary glands, exposed ticks were held at 25 C for 15 to 18 days, followed by a 3-day incubation at 37 C. Ticks of 2 species transmitted A marginale to calves; the third tick species was confirmed infected by demonstration of typical colonies in tick gut cells, but transmission was not attempted; Colonies of A marginale were seen with light microscopy in salivary glands of all 3 species of ticks; they were located in acinar cells that contained simple granules. Colonies varied morphologically from small, compact ones to larger structures that contained distinct organisms and often were adjacent to the host cell nucleus. Electron microscopy confirmed that the colonies were rickettsial organisms. Morphologic features of A marginale varied and included reticulated forms, forms with electron-dense centers, and small particles; these various forms were similar to those described previously in midgut epithelial cells of ticks. We believe that the organism seen within tick salivary glands may replicate in the glands before its transmission to the vertebrate host.

The disposition of theophylline in healthy ruminating calves was best described by a first-order 2-compartment open pharamacokinetic model. The drug had a mean elimination half-life of 6.4 hours and a mean distribution half-life of 22 minutes. Total body clearance averaged 91 ml/kg/h. The mean values for the pharmacokinetic volume of the central compartment, pharmacokinetic volume of distribution during the terminal phase, and volume of distribution at steady state were 0.502, 0.870, and 0.815 L/kg, respectively. Theophylline was readily absorbed after oral administration to the ruminating calf, with a mean fraction of 0.93 absorbed. The plasma concentrations after oral dosing peaked in approximately 5 to 6 hours, with a mean absorption half-life of 3.7 hours. A flip-flop model (rate constant of input is much smaller than the rate constant of output) of drug absorption was not found because the elimination process roughly paralleled that of the study concerning IV administration. In a multiple-dose trial that used a dosage regimen based on single-dose pharmacokinetic values, clinically normal calves responded as predicted. However, diseased calves had higher than expected plasma concentrations after being given multiple oral doses of theophylline at 28 mg/kg once daily. Overt signs of toxicosis were not seen, but this aspect of the drug was not formally investigated. Theophylline can be used as an ancillary therapeutic agent to treat bovine respiratory disease, but not without risk. The suggested oral dose of theophylline at 28 mg/kg of body weight once daily should be tailored to each case. Twice daily oral dosing at 20 mg/kg should reduce the plasma peak:trough ratio and provide plasma concentrations more cnsistently within the human therapeutic range of 10 to 20 micrograms/ml. Even then, therapeutic drug monitoring should be done.

Tissue specimens from muscle, liver, kidney, and injection sites were collected, and serum was obtained from 3 calves euthanatized on each of posttreatment days 5 and 22. Calves were treated with 6.7, 13.4, or 20 mg of oxytetracycline (OTC)/kg of body weight, IM, once daily for 3 days; these dosages are 1, 2, and 3 times the label dose, respectively. One control calf was euthanatized on each of posttreatment days 5 and 22. In treated male calves killed 2 days after the last injection, OTC residues were detected in all tissues and serum, using high-performance liquid chromatography. Tissues from all injection sites also were considered positive for antimicrobial residues, using swab test on premises (STOP), microbial inhibition test (MIT), and thin-layer chromatography-biautography (TLCB) test. Kidney tissues from a calf given 13.4 mg of OTC/kg and kidney and liver tissues from a calf given 20 mg of OTC/kg also were considered positive, using the MIT and TLCB. Results of the STOP only were considered positive for the liver and kidney of a calf given 20 mg of OTC/kg, but substitution of Saskatoon antibiotic medium-3 for the original medium (antibiotic medium-5) allowed the STOP to detect residues in these tissues from all treated calves. In female calves killed 19 days after the last injection, the STOP, MIT, and TLCB procedures revealed positive results for tissues from some injection sites, but revealed negative results for other tissues. High-performance liquid chromatographic analyses detected OTC in tissues from injection sites from all treated calves, in muscle and liver from a calf given 20 mg of OTC/kg, and in kidneys from calves given 13.4 or 20 mg of OTC/kg. The STOP, MIT, and TLCB procedures lacked the sensitivity of high-performance liquid chromatography for detection of OTC residues.

Bovine leukemia virus (BLV) was transmitted by horse flies, Tabanus fuscicostatus, from a cow with a lymphocyte count of 31,500/mm3 to goats and dairy calves. As few as 10 and 20 flies transmitted BLV to goats and calves respectively, but the minimal number of flies required to transmit the infection was not established. Groups of 150 and 100 T fuscicostatus transmitted BLV to beef calves from a cow with a lymphocyte count of 14,600/mm3. These results support a role for horse flies in the horizontal transmission of BLV.

Sixteen 7-week-old Holstein male calves were inoculated with sporulated oocysts of Eimeria zuernii. Four calves (controls) were euthanatized and necropsied at 14 and 20 days after inoculation (DAI). Two calves were treated with 20 mg of dexamethasone (IM) on 13, 14, and 15 DAI and euthanatized and necropsied 17 DAI and 2 calves were given similar treatments and necropsied 20 DAI. The 8 other calves were euthanatized and necropsied 20 DAI. Two were started on the anticoccidial drug decoquinate in feed 13 DAI; 2 others were given decoquinated on the same schedule plus dexamethasone on 13, 14, and 15 DAI. Two calves were given the antibiotic narasin in feed beginning 13 DAI and 2 calves were given parasin on the same schedule plus dexamethasone on 13, 14, and 15 DAI. All calves, except 2 controls necropsied 14 DAI and 4 calves given decoquinate, discharged moderate-to-large numbers of oocysts in feces and had moderate-to-severe changes in fecal consistency. Histologic examintions revealed large numbers of endogenous stages in tissues of calves treated or not treated with dexamethasone. Few endogenous stages were observed in tissues from calves that were given decoquinate or decoquinate plus dexamethasone. Calves given narasin or narasin plus dexamethasone had moderate-to-large numbers of endogenous stages in the tissues.

A controlled anthelmintic trial was conducted to determine the efficacy of febantel paste (45.5%) at dosages of 2.5, 5.0, 7.5, and 10.0 mg/kg in calves harboring natural gastrointestinal nematode infections. Dosages of 5.0, 7.5 and 10.0 mg of febantel/kg of body weight were greater than 96% effective in removing adults of Haemonchus contortus, Ostertagia spp, Cooperia spp, and Oesophagostomum radiatum. The 2.5 mg/kg dosage was considered suboptimal because of low efficacy against Ostertagia and Cooperia spp. Efficacies against Trichostrongylus axei, Trichuris spp, Bunostomum phlebotomum, and Strongyloides papillosus were difficult to determine because fewer numbers of these nematodes were recovered. Efficacies of febantel paste against immature bovine parasites ranged from 83.62% to 97.72%.

The antibody responses to the capsular carbohydrate (CC) purified from Pasteurella haemolytica serotype 1 were determined by an ELISA using 135 sera from 6 calves vaccinated with phosphate-buffered saline solution, formalin-killed P haemolytica bacterins, live P haemolytica, or an extract of P haemolytica referred to as carbohydrate-protein subunit (CPS). Calves vaccinated with live P haemolytica, bacterins, or CPS developed serum antibodies to CC. Bacterins containing Freund incomplete adjuvant or Freund complete adjuvant induced higher antibody responses than did bacterins containing aluminum hydroxide. In 4 of 6 experiments, high antibody responses to CC were significantly (P less than 0.05) correlated with resistance to transthoracic challenge exposure with P haemolytica. When calves were challenge exposed with a dose of P haemolytica that was 4.5 times greater than the standard challenge exposure dose or when calves that had been vaccinated with CPS were challenge exposed, antibody responses did not significantly (P greater than 0.05) correlate with resistance to challenge exposure. The amount of serum antibodies to CPS increased significantly (P less than 0.05) when calves were vaccinated with live or killed P haemolytica or with CPS, compared with that in calves given saline solution. In 5 of 6 experiments, correlation between high antibody responses and resistance to challenge exposure was significant (P less than 0.05). The correlation between those variables was not significant (P less than 0.07) for CPS-vaccinated calves. In the ELISA, treatment of CPS with sodium m-periodate, to oxidize periodate-sensitive carbohydrate epitopes, failed to markedly alter the antibody response to CPS. However, the correlation between high antibody responses to periodate-treated CPS and resistance was significant (P less than 0.05) for all 6 experiments. In the ELISA, periodate treatment of CC, lipopolysaccharide, and CPS caused average reductions in antibody reactivity of 7.1%, 53.8%, and 34.5%, respectively. Preadsorption of sera with CC or lipopolysaccharide did not markedly reduce antibody reactivity with CPS. Preadsorption of sera with CC and reaction with periodate-treated and nontreated CPS indicatedthat for calves given phosphate-buffered saline solution vaccines, antibody reactivity was reduced 65.4%, whereas for those vaccinated with a bacterin with aluminum hydroxide, a bacterin with Freund incomplete adjuvant, or live P haemolytica, antibody reactivity was reduced 47.1%, 40.5%, and 25.0%, respectively. It was concluded that serum antibodies to CC are of some importance in resistance and that certain epitopes in CPS that are not sensitive to periodate are of importance in resistance to bovine pneumonic pasteurellosis. There are qualitative and quantitative differences among the serum antibody responses to carbohydrate epitopes for calves vaccinated with phosphate-buffered saline solution, bacterins, or live P haemolytica.

High-speed cinematography was used to record the movements of 12 cutting horses performing a standard test with a mechanical flag. Based on their previous competitive performances, horses were classified into 2 groups: group 1, composed of 5 moderately successful or average performers that had won less than $35,000 in purse money; and group 2, composed of 7 highly successful or elite performers that had amassed greater than $35,000 in competition earnings. Analysis of the results indicated that, compared with horses of the average group, the elite horses had faster reaction times in response to the start and cessation of flag movement (P less than 0.01), and were positioned closer to the flag during all stages of the trial (P less than 0.05). Discriminant analysis was used to construct a mathematical formula that could be used to classify an individual horse into 1 of the 2 alternative groups, based on the set of measurements. Two predictor variables were selected that described the maximal distance between the horse and the flag during the run and the part of the body that was moved first in response to the initial flag movement. The accuracy of the predicted group membership, compared with the actual group membership, was 100%.

A clinical trial examining the efficacy of 2 drugs for treatment of a natural epizootic of infectious bovine keratoconjunctivitis was performed. The study was conducted in 103 grazing Hereford calves during the summer of 1985. The calves were prospectively and randomly assigned to 1 of 3 groups at the beginning of the study on June 17, and were examined 3 times weekly thereafter until the final observation on August 6. Calves in group 1 (n = 34) were not treated and were used as controls. Calves of group 2 (n = 34) with corneal ulcers were treated with a long-acting oxytetracycline formulation (OTC group). The parenteral treatment was repeated in 72 hours. Affected calves of group 3 (n = 35) were treated topically with furazolidone spray when they developed new corneal ulcers, or when existing lesions worsened during subsequent examination periods (NFZ group). Healing times of the corneal ulcers were reported in 3 ways: the combined times for ulcers present in both eyes of a calf simultaneously (method A), independent times of each ulcer on a calf (method B), and time of the first ulcer for each calf (method C). Censored healing times were examined as left censored (ulcer present at the beginning of the study), right censored (ulcer not healed at the end of the study), or uncensored (true) healing times. The effect that the treatments had on healing times were investigated by use of notched box and whisker plots, life tables, and Cox regression models. The analysis indicated that treatment of calves with either antimicrobial reduced the healing time of corneal ulcers, compared with untreated controls. Calves treated with OTC had shorter periods with ulcers present on both eyes than did NFZ-treated calves. The healing time of the first ulcer on a calf was faster when treated with either antimicrobial than when not treated, but no significant difference between periods for OTC and NFZ treatments was found. Censored healing times were consistently longer than uncensored healing times. Box and whisker plots indicated that both treatments shortened healing times more than those for controls, and OTC shortened healing times more than did NFZ for responses A and B (but not C). Life tables showed that OTC healing times were shorter than those for controls, and NFZ shorter than controls for response B and C (but not A). Cox regression model (for response A) showed a borderline significant difference between times for OTC group and controls, and no significant difference between times for NFZ group and controls.

The potential action of immunologic reactions and mediators released during the course of bovine respiratory syncytial virus infection in pathogenesis of the ensuing disease process was examined in an experimental infection study . Prostaglandin (PG) E2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane B2 (TxB2) concentrations were quantitated in plasma and lung lavage fluid by radioimmunoassay at 3- to 4-day intervals during a primary and secondary virus infection of vaccinated, nonvaccinated, and control (mock-infected) calves. A significant increase in the plasma PGE2 concentration for the nonvaccinated calves was noticed on day 3 after primary infection and on day 7 after secondary infection. The PGF2 alpha plasma concentrations increased significantly for the nonvaccinated groups on day 10 after primary infection. Plasma 6-keto-PGF1 alpha concentrations increased for nonvaccinated and vaccinated calves 3 days after the secondary infection. Plasma TxB2 concentrations during the primary exposure did not vary significantly. However, 14 days after the secondary exposure, both experimental groups had concentrations significantly greater than did the control group. Lung lavage fluid concentrations of TxB2 had peaks of activity 7 days after primary and secondary viral infections for the nonvaccinated group. Increases in plasma PG concentrations corresponded variably with disease expression, whereas plasma TxB2 concentrations did not have any correlation with disease expression. However, there was a significant correlation between TxB2 concentration in lung lavage fluid of the nonvaccinated group with disease expression 7 days after primary and secondary virus infection. The potent physiologic effects of PG and TxB2 and their demonstrated production in this infection study suggest that these mediators and the effects of vaccination on their production should be considered as a potentially important factor in the natural disease process.