Respiratory tract infections are prevalent in foals, yet the frequency with which the distal airways are affected in chemical episodes of respiratory tract disease has not been evaluated to our knowledge. The objective of the study was to determine the incidence of distal respiratory tract infection (DRTI) in foals on a sample of Thoroughbred breeding farms (n = 10) in Ontario. In a pilot study, clinical criteria commonly used to select foals for antimicrobial treatment (detection of abnormal lung sounds, plus nasal discharge, cough, fever, tachypnea, and/or lethargy) were found to segregate foals with and without endoscopically confirmed DRTI. Mucopurulent exudate and bronchial erythema were observed more frequently (P < 0.005), bronchial lavage total cell count and neutrophil concentration were significantly (P < 0.005) higher, and intracellular cocci were recovered significantly (P < 0.01) more often from bronchial lavage samples of affected foals (n = 8) than of controls (n = 8). These clinical criteria were used to identify cases in a cohort of Thoroughbred foals (n = 219) from May 1 to October 30, 1991. Case morbidity adjusted for clustering was 82 +/- 5% (95% confidence limits, 72 to 92%). Most (74%) episodes of clinical DRTI were detected in july and August, and equal numbers were detected before (53%) and after (47%) weaning of foals. Of 178 cases, 66 (48%) were selected at random for endoscopy and bronchial lavage. Grade-II pharyngeal lymphoid hyperplasia was observed commonly (60% of foals); auditory tube diverticulum (guttural pouch) discharge was observed in 18 of 86 (21%) foals, and guttural pouch infection was confirmed in 6 of 7 foals examined endoscopically. Endoscopically confirmed DRTI, defined as visual detection of bronchial exudate with microscopic detection of intracellular cocci and markedly high neutrophil count in bronchial lavage samples, was confirmed in 75 of 86 (87%) cases tested. These data indicate that DRTI might be reliably diagnosed by auscultation during a simple rebreathing exercise. The syndrome of DRTI was extremely common in Thoroughbred foals, characterized by marked inflammation of visible airways and cytologic evidence of bacterial infection. Risk factors for clinical (undifferentiated) DRTI were not identified in this study.

Stimulation of alpha 2 adrenergic receptors inhibits colonic motility and may constrict some peripheral vascular beds. Endotoxemia elicits release of sympathetic neurotransmitters and increases sympathetic nerve activity, which may result in stimulation of alpha 2 adrenergic receptors. The objective of this study was to determine whether blockade of alpha 2 adrenergic receptors would restore cecal motility and blood flow during endotoxemia in horses. Strain-gauge force transducers and ultrasonic flow probes were used to measure cecal and colonic mechanical activity and lateral cecal arterial blood flow. Intravenous infusion of endotoxin (cumulative dose of 0.03 mg/kg) significantly decreased cecal and right ventral colon contractile activity and lateral cecal arterial blood flow. Slow IV infusion of yohimbine (cumulative dose of 75 micrograms/kg) significantly attenuated those effects of endotoxin. On the basis of our findings, we concluded that endotoxemia causes cecal and proximal colonic ileus and cecal hypoperfusion via a mechanism that involves alpha 2 adrenergic receptors.

The effects of exogenous platelet-activating factor (PAF) were determined in anesthetized ponies. Administration of PAF induced a decrease in cardiac index that resulted in systemic hypotension. This was followed by tachycardia, hypertension, and a return of cardiac index to baseline. Pulmonary arterial pressure increased markedly because of pulmonary vasoconstriction. Exogenous PAF also caused leukopenia and thrombocytopenia. The specific PAF receptor antagonist (WEB 2086) blocked all PAF-induced changes. Flunixin meglumine, a cyclooxygenase inhibitor, abolished the pulmonary hypertension and tachycardia, and attenuated the systemic hypotension but did not change the PAF-induced peripheral cellular changes. The PAF antagonist also inhibited platelet aggregation induced by PAF in vitro. The PAF-induced changes are similar to those reported after endotoxin exposure in horses.

Using polyclonal rabbit and monoclonal mouse anti-dog IgE antibodies, we developed ELISA for measurement of ragweed-specific IgE in canine serum. In the ELISA, microtitration plates were coated with ragweed extract and sequentially incubated with canine serum, purified monoclonal or polyclonal anti-dog IgE, and conjugated goat antibody to mouse IgG or rabbit IgG. Serum ragweed-specific IgE values were measured by the 2 ELISA in serum samples from 60 ragweed-allergic dogs and in serum from 10 control dogs. Passive cutaneous anaphylaxis (PCA) tests were performed on these sera to compare results with those of the ELISA, Mean coefficient of variation between assays was 0.20 +/- 0.10 for the assay using the polyclonal antibody and was 0.17 +/- 0.10 for that using monoclonal antibody. Sensitivity was 0.6 U/ml for the ELISA, using polyclonal antibody, and 2.5 U/ml for the ELISA, using monoclonal antibody. Serum ragweed-specific IgE values measured by the 2 ELISA strongly correlated with PCA titers (P < 0.0000), but the ELISA using polyclonal antibody had higher correlation with PCA titer (r = 0.84) than the ELISA using monoclonal antibody (r = 0.59). The geometric mean ragweed-specific IgE value measured by the 2 ELISA and by PCA testing, was significantly higher (P < 0.0000) in allergic dogs than in control dogs. The 2 ELISA were specific, sensitive, and reproducible for measurement of ragweed-specific IgE in canine serum.

Foremilk, residual milk, and blood samples were studied for 10 days during acute mastitis episodes induced by endotoxin infused via the teat canal. Quarter milk and blood samples were collected frequently for 3 days after the infusion and thereafter once or twice daily. Leukocyte concentration in milk and blood was determined by flow cytometry. Within 2 hours after infusion of the endotoxin, clinical mastitis was observed. Total leukocyte concentration and proportion of neutrophils increased significantly (P < 0.05) by postinfusion hour (PIH) 2 in foremilk and by PIH 4 in residual milk. From PIH 2, serum albumin content and N-acetyl-beta-D-glucosaminidase activity were significantly increased in both fractions. Neutrophils were the predominant leukocyte population in both fractions until PIH 59. From PIH 72, lymphocytes were the predominant cell population until PIH 175 in foremilk and until PIH 223 in residual milk. Serum albumin content and N-acetyl-beta-D-glucosaminidase activity in residual milk was significantly lower than in foremilk from PIH 4 to 24 and from PIH 24 to 59, respectively. Regarding total and differential leukocyte counts, values for the 2 fractions followed the same pattern throughout the course of inflammation, probably owing to frequent sample collection. Total and differential cell counts tended to differ between the fractions during some periods, although differences were not statistically significant. When samples were taken less frequently, the total leukocyte concentration in residual milk was higher than that in foremilk. Although sample collections were frequent, clustering of immature neutrophils was not observed in the cytofluorogram of blood leukocytes in this study. Residual milk seems to be the fraction that best reflects the condition in the quarter at the particular time when the milk sample is taken. Results also indicate that residual milk reflects the condition of the secretory tissue, as well as the lower regions of the gland.

Sonographic observations were made of the image mean gray scale (MGS) of the flexor tendons and ligaments in the left and right metacarpal regions of each of 10 clinically normal horses. In images made in the dorsal and sagittal planes, the MGS was measured at multiple sites in the superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT), accessory ligament (AL), and suspensory ligament (SL), and at single sites in the medial and lateral limbs of the SL, and the palmar ligament. Relative sonographic brightness of each tendon and ligament was calculated by dividing the value of its MGS by the mean value for the MGS of images of 3 soft tissue equivalent phantoms. When a multivariate repeated-measures of ANOVA of the relative brightness values was statistically significant (P < 0.05), Tukey's method of multiple comparisons was used to determine which values were significantly different from each other. In the dorsal plane, the SL was significantly brighter than the DDFT, SDFT, and AL; relative brightnesses of the DDFT and SDFT were similar, as were those of the SDFT and AL. In the sagittal plane, the SL again was the significantly brightest structure, followed by the Al, and similar brightnesses of the DDFT and SDFT. In dorsal images made 25 cm distal to the accessory carpal bone, relative brightnesses of the SDFT, DDFT, and the medial and lateral limbs of the SL were similar. In images made 30 cm distal to the accessory carpal bone, relative brightness of the palmar ligament was significantly (P < 0.05) less than that of the SDFT and DDFT in the dorsal plane, but not in the sagittal plane, where it was significantly greater. Relative brightness values represented a unique sonographic characteristic of each structure and, in the future, may provide further insights into tendon and ligament structure and function.

Monoclonal antibodies were prepared against 40- and 56- to 64-kd antigens of Chlamydia pecorum strain Maeda, which was isolated from a cow with pneumonia. Using the monoclonal antibodies, 5 strains of C pecorum, 25 strains of mammalian and 19 strains of avian C psittaci, 1 strain of C pneumoniae, and 3 strains of C trachomatis were analyzed for immunologic reactivity by use of the indirect immunofluorescent test. Monoclonal antibody analysis revealed immunologic relatedness between C pecorum and mammalian strains of C psittaci, which were completely differentiated from the other avian strains. Bovine strains were distinguished from ovine strains. Antigenic diversity mm observed for bovine and ovine strains. Feline- and guinea pig-derived strains were shown to be immunologically different from bovine and ovine strains. Results provide the basis for typing and epidemiologic study of bovine and ovine strains of C pecorum and C psittaci.

We compared the plasma cortisol and immunoreactive corticotropin (IR-ACTH) responses to incremental doses (1.25, 12.5 and 125 micrograms) of synthetic ACTH (cosyntropin) administered IV to 6 clinically normal cats. Mean plasma cortisol concentration increased significantly (P < 0.0001) after administration of all 3 doses of cosyntropin. After administration of the 1.25- and 12.5-microgram doses, plasma cortisol concentration peaked at 30 minutes, then decreased to values not significantly different from baseline concentration by 90 and 120 minutes, respectively. In contrast, after administration of the 125-microgram dose, mean cortisol concentration peaked at 60 minutes and remained significantly (P < 0.05) higher than baseline values at 120 minutes. Compared with the 1.25- and 12.5-microgram doses, administration of the 125-microgram dose of cosyntropin induced significantly (P < 0.05) higher cortisol responses at 60, 90, and 120 minutes. Although individual cat's peak plasma cortisol concentration after administration of the 125-microgram dose was higher than the peak value determined after administration of the 2 lower doses of cosyntropin, these differences were not statistically significant. Mean plasma IR-ACTH concentration increased significantly (P < 0.0001) and reached a maximal value at 30 minutes after administration of all 3 doses of cosyntropin. After administration of the 1.25- and 12.5-microgram doses, plasma IR-ACTH concentration decreased to values not significantly different from baseline concentration by 60 and 120 minutes, respectively, whereas mean IR-ACTH concentration remained significantly (P < 0.05) higher than baseline values 120 minutes after administration of the 125-microgram dose. Mean peak plasma IR-ACTH concentration attained after administration of the 125-microgram dose of cosyntropin was significantly higher than that attained after administration of the 2 lower doses. Peak plasma IR-ACTH concentration attained after administration of the 12.5-microgram dose of cosyntropin was significantly higher than that attained after administration of 1.25 micrograms of cosyntropin. Results of the study indicate that IV administration of cosyntropin at doses ranging from 1.25 to 125 micrograms induces similar peak plasma cortisol responses in clinically normal cats, indicating that all of the doses may maximally stimulate the adrenal cortex. Administration of the higher cosyntropin doses did, however, result in more prolonged adrenocortical response.

Four 1-year-old steers were each inoculated orally with 10,000 Toxoplasma gondii oocysts of the GT-1 strain and euthanatized on postinoculation days (PID) 350, 539, 1191, and 1201. Samples (500 g) of tongue, heart, semimembranosus and semitendinosus muscles (roast), intercostal muscles (ribs), longismus muscles (tenderloin), brain, kidneys, liver, and small intestine were bioassayed for T. gondii by feeding to cats and examination of cat feces for shedding of oocysts. Toxoplasma gondii was recovered by bioassays in cats from the 3 steers necropsied PID 350, 539, and 1191, but not from the steer euthanatized on PID 1201. Cats shed oocysts after ingesting tongue from 2 steers, heart from 3 steers, liver from 2 steers, and roast, ribs, brain, and intestines from 1 steer each. Taxoplasma gondii was not isolated from any of the other bovine tissues. In addition to tissues bioassayed in cats, homogenates of mesenteric lymph nodes, lungs, spinal cord, spleen, and eyes were bioassayed in mice for T. gondii infection. Toxoplasma gondii was not recovered from the 135 mice inoculated with tissue from each of the 4 steers. All 4 inoculated steers developed high T. gondii antibody titers (greater than or equal to 1:8,000) in the agglutination test, using formalin-fixed whole tachyzoites. In the steer euthanatized on PID 1201, agglutinating T. gondii antibody titers decreased from 1:4,000 to 1:320 between 2 and 5 months after inoculation and to 1:20 by 19 months after inoculation.

Combined blood pool and delayed images produced by use of 99mTc-methylene diphosphonate (99mTcMDP) were evaluated as an objective measurement of the response of equine joints with osteochondral defects to postoperative exercise and intra-articularly administered polysulfated glycosaminoglycan (PSGAG). Osteochondral defects (approx 2.4 X 0.9 cm) were induced arthroscopically in the dorsodistal radial carpal bones of 18 ponies. These ponies were randomized (while balancing for age [range 2 to 15; median, 5.0; mean, 5.1 years]) to 2 treatment groups. Nine ponies were assigned to be exercised, and 9 were stall-rested. Six ponies in each group were administered PSGAG (250 mg) in 1 joint (medicated) and lactated Ringer's solution (LRS) in the contralateral joint. The 3 remaining ponies in each group were administered LRS in both joints (nonmedicated). Medication was given at surgery, then weekly for 4 weeks. The exercise protocol (begun at postoperative day 6 and conducted twice daily) started with 30 minutes walking (approx 0.7 m/s), and, by postoperative month 3, the ponies were being walked for 15 minutes and trotted (approx 1.6 m/s) for 25 minutes. Simultaneous dorsal images of both carpi were made 2 to 3 minutes after IV administration of 99mTcMDP (blood pool image) and 90 to 120 minutes later (delayed image). Scintimetry, in counts per minute per pixel per millicurie, was done before, and at 1, 2, 4, 8, 10, 13, and 17 weeks after surgery, prior to euthanasia. Radionuclide uptake on blood pool images decreased faster than that on delayed images, in which uptake remained high for 17 weeks. This indicated that bone was metabolically active for at least 17 weeks after surgery. Exercise significantly (P < 0.05) decreased uptake on the blood pool images of medicated joints up to 1 month after surgery. Thus, exercise (in the presence of PSGAG) probably had a transient, beneficial effect on soft tissues of the joint. Exercise, without PSGAG, promoted increased bone remodeling, because the highest uptake on delayed images was observed in exercised, nonmedicated ponies up to 3 months after surgery. This was consistent with development of osteoarthritis in these ponies. Medication alone stimulated bone remodeling, and data indicated that an identical effect may take place in contralateral LRS-injected joints, because of systemic circulation of the drug. However, the combination of exercise and medication appeared to moderate the independent effects of each. The combination of exercise and medication in individual joints resulted in notably (P < 0.05) decreased bone remodeling. Medication caused a decrease in bone remodeling in exercised ponies, indicating a protective effect against development of osteoarthritis.