A specific polymerase chain reaction (PCR) assay was devised, allowing detection of 1 bovine leukemia virus (BLV)-infected cell in 10(4) bovine lymphocytes. The efficacy of field application of the developed method was verified by evaluating the rate of viral transmission to calves from infected cows, whether they have persistent lymphocytosis. With this objective, 43 calves were simultaneously tested at birth and at 6 months of age for viral antibodies in serum and for proviral DNA in lymphocytes. At birth, 36 calves were BLV-negative and 3 were BLV-positive by results of serologic and DNA-based assays. Conversely, results for 4 calves had lack of correlation between the diagnostic methods. In particular, 2 calves were DNA-positive and antibody-negative for BLV and 2 other calves had the opposite test results. At 6 months of age, when the immunologic pattern more closely reflects the status of calves' immune response, independent of maternal antibodies, all calves DNA-negative for BLV at birth (n = 38), were consistently PCR- and antibody-negative for BLV. On the contrary, the cattle DNA-positive for BLV at birth (n = 5), whether seropositive or not, were PCR- and antibody-positive for BLV, at the time of the second screening. Thus, these results indicate reliability of the PCR to diagnose perinatal BLV infection. Furthermore, the observation that all calves found to be infected at birth were born to BLV-positive cows with persistent lymphocytosis, indicates that the persistent lymphocytosis status of the cow may represent a factor associated with BLV infection in utero.

Characteristic alterations in the serum and urine biochemical profiles of Doberman Pinschers with congestive heart failure (CHF) resulting from idiopathic dilated cardiomyopathy were determined. We compared these alterations with those observed in 2 other models of CHF: rate overload induced by rapid ventricular pacing in dogs, and biventricular hypertrophy and dilatation induced in turkey poults by furazolidone toxicosis. Serum and urine biochemical changes in both models of CHF in dogs were mild to moderate in degree, and were moderately consistent, They could be attributed to secondary neurohumoral, hepatic, and renal effects of heart failure. The most marked and consistent changes observed were mildly decreased anion gap that developed, in part, because of decreased serum sodium concentration, moderately increased catecholamine concentrations, moderate lactaciduria, hyposthenuria, and mildly increased urea concentrations and liver enzyme activities. In birds with furazolidone cardiomyopathy, we observed mild increases in serum urate concentration, liver and muscle enzyme activities, but moderately increased sodium concentration with decreased chloride concentration. In the pacing and furazolidone models, in which CHF was rapidly induced, moderate to marked hypoproteinemia was attributable to decreases in albumin and globulin concentrations. Using the avian model we found that the hypoproteinemia could be largely attributed to blood volume expansion, and to a lesser extent, inanition. Development of hypoalbuminemia during rapid ventricular pacing and furazolidone treatment may contribute to the effects of rate overload or drug toxicity in the pathogenesis of CHF, because hypoalbuminemia may contribute to altered hemodynamics and neuroendocrine system activation. Our data indicate that clinical biochemical analysis of serum and urine may be useful for assessing progression of CHF.

Lameness examinations and radiography of the distal phalanx and associated soft-tissue structures of the front feet of 103 Thoroughbred racehorses, 4 to 9 years old, were performed to determine normal radiographic appearance and morphometry. Of 103 horses examined, 41 were used in the study that were without clinical signs of foot problems or lameness, had raced at least twice prior to radiography, and had raced at least twice more in the 6 months after radiography. Lateromedial and dorsoproximal-palmarodistal radiographic views of each front distal phalanx were used to measure 28 bone and soft-tissue structures, and to evaluate 14 radiographic findings. Significant differences were not observed between left and right digits for any radiographic determination. Mean thickness of the soft tissues dorsal to the distal phalanx, which provides an evaluation of the epidermal laminae, was 14.6 +/- 1.0 mm when measured adjacent to the distal aspect of the distal phalanx. Most horses had straight, smooth hoof walls that were parallel to the dorsal cortex of the distal phalanx. The mean degree of palmar rotation of the distal phalanx was -0.5 +/- 1.3, and none was rotated more than 4 degrees. The dorsal cortex was smooth and straight, without bone deposition or reaction in either digit for only 5 of the 41 horses. Active bone formation was seen unilaterally along the middle portion of the dorsal cortex in 7 horses, and along the distal portion of the dorsal cortex in 4 of the phalanges from 3 horses. New bone formation along the distal dorsal cortex was often accompanied by resorption of the palmar cortex. For 26 of the 31 horses without active bone deposition, smooth inactive bone formation along the midportion of the dorsal cortex was identified in 1 or both distal phalanges. Bone at the solar margin of the distal phalanx was uniformly dense and finely trabeculated, without evidence of resorption or fractures. Severe irregularity of the solar margin was not found in any digit, and the margin of both phalanges was smooth in 8 horses. Various degrees of solar margin irregularity were observed in the other 33 horses. The mean number of vascular canals within the distal phalanx was 8.4 +/- 1.7, and the diameter of the largest canal was 3.4 +/- 0.6 mm. A mean number of 2.0 +/- 1.2 vascular canals was oriented parallel to the radiographic beam on the dorsoproximal-palmarodistal view, and these were termed end-on vessels, because they were visualized as radiolucent dots greater than or equal to 1 mm in diameter in the central portion of the distal phalanx. Racing performance of horses with subtle radiographic signs of laminitis (palmar rotation, hoof wall curvature or undulations, palmar cortical resorption, distal dorsal cortical bone deposition) was poorer than that of horses without these signs. These findings are suggestive of a subclinical laminitis condition, which may influence performance without causing overt clinical signs.

The role of platelet-activating factor in mediating the cardiovascular and peripheral cellular responses to large-colon ischemia and reperfusion, was explored in anesthetized ponies. A specific platelet. activating factor (PAF) antagonist (WEB 2086) was administered to a group of 6 ponies, and another 6 ponies (controls) were given an equivalent volume of saline solution, prior to 1 hour of large-colon torsion. After correction of the torsion, ponies were monitored during the reperfusion period. Significant (P < 0.05) hypotension and metabolic acidosis developed in afl ponies after correction of colonic torsion, cardiac index increased initially, but then decreased significantly (P < 0.05) over the study period. Mean times between correction of torsion and onset of cardiac failure and death were not different between groups. Significant (P < 0.05) thrombocytopenia developed during the reperfusion period in control ponies, but not in WEB-treated ponies. Blood leukocyte concentration in control ponies was more variable and significantly (P < 0.05) decreased immediately upon reperfusion, compared with that in WEB-treated ponies. We conclude that although the cardiovascular responses to colonic ischemia and reperfusion are not prevented by use of a specific PAF-antagonist, specific peripheral cellular responses are mediated by PAF.

Brain stem auditory evoked potential (BAEP) testing with air-conducted click stimuli can be used to diagnose sensorineural deafness in dogs if conductive deafness can be ruled out. Detection of conductive deafness can be performed by recording BAEP elicited by a vibratory stimulus transducer placed against the skull. Air- and bone-conducted BAEP were compared in dogs, varying bone stimulator placement, click polarity, and stimulus intensity. Optimal bone stimulator placement was determined to be over the mastoid process, followed by the mandible and the zygomatic arch. Condensation polarity clicks gave responses preferable to those elicited by rarefaction or alternating polarity. Bone-conducted BAEP peak latencies were significantly longer than air-conducted latencies after correction of the latencies for the air conduction time accompanying air-conducted stimuli. Significant differences between stimulus modalities were not seen for BAEP peak amplitudes or interpeak latencies. Latency-intensity and amplitude-intensity regressions had similar effects for both modalities: latencies decreased and amplitudes increased as stimulus intensity increased.

Virologic and pathologic investigations were done on prednisolone-treated bitches with a history of canine herpesvirus (CHV) infection. Reactivation of CHV was demonstrated in 5 Beagle bitches after daily administration of 600 mg of prednisolone for 5 days. The reactivation was confirmed in 4 of 5 bitches. Canine herpesvirus was recovered from nasal, oral, vaginal, and ocular secretions on the 5th to 2lst days after initiation of treatment with prednisolone, and also from nasal mucosa and tonsil tissues. Results indicated that latent CHV infections develop and that the virus may be reactivated, without clinical signs, in dogs with a history of CHV infection.

Tissue homogenates were obtained from swine co-infected with 2 vaccine strains of pseudorabies virus (PRV). Viral isolates derived by serial plaque purification directly from tissue homogenates, without an intervening step of isolation and amplification on cell cultures, were characterized as recombinant and parental PRV genotypes on the basis of thymidine kinase and glycoprotein X gene combinations. Use of limiting dilutions and recovery of virus isolates as individual plaques minimized the likelihood of in vitro recombination serving as a confounding source of recombinant PRV. The thymidine kinase and glycoprotein X gene sequences were classified as wildtype or deleted, using a battery of polymerase chain reaction assays. Results substantiate the observation that PRV vaccine strains can form genetic recombinants in vivo after experimentally induced co-infection.

The prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavage specimens and the prevalence of mycoplasmal recovery from pharyngeal swab specimens from dogs with (n = 38) or without (n = 26) pulmonary disease were determined. Similar mycoplasmal recovery rates were found for tracheobronchial lavage specimens from dogs > 1 year old with (21%) or without (25%) pulmonary disease. Prevalence of mycoplasmal recovery from tracheobronchial lavages was significantly associated with pulmonary disease among dogs < 1 year old (P = 0.04), and with dogs that had concurrent Bordetella (P = 0.006) and Streptococcus (P = 0.05) isolations. Among dogs with pulmonary disease, mycoplasmas were significantly (P = 0.02) more prevalent in dogs with septic inflammation than in dogs with nonseptic inflammation of the tracheobronchial tree. Ureaplasmas were only isolated from a tracheobronchial lavage specimen of 1 dog with pulmonary disease and from none of the dogs without pulmonary disease. Most dogs with (84%) and all dogs without pulmonary disease had mycoplasmas isolated from the pharynx. Seemingly, mycoplasmas are part of the normal pharyngeal flora of most dogs and normal inhabitants of the lower airway in about a fifth to a fourth of the canine population greater than or equal to 1 year old. Dogs < 1 year old with pulmonary disease and dogs with concurrent Bordetella or tracheobronchial streptococcal isolations may be more susceptible to mycoplasmal colonization of the lower airways. Seemingly, ureaplasmas are rarely associated with pulmonary disease, and are not normal inhabitants of the trachea and bronchi of dogs.

Existence of ultradian variation in serum progesterone concentration and the relation between progesterone and luteinizing hormone (LH) secretory patterns were investigated in nonpregnant and pregnant mares. Blood samples were taken every 15 minutes for a 24-hour period on day 8 of the estrous cycle and day 18 of pregnancy, respectively. Progesterone and LH concentrations were determined by radioimmunoassay. Progesterone was secreted in pulsatile manner in nonpregnant and pregnant mares. Luteinizing hormone also was secreted in a pulsatile manner in both groups of mares. There was little temporal relation between LH and progesterone pulses in either pregnant or nonpregnant mares.

The impact of nematode parasitism of the digestive tract on milk output and milk quality was examined in dairy goats. In addition, the consequences of worm infection were compared in goats with different lactation performance (ie, with initial high or low milk production). Forty-eight goats in the second month of lactation were allotted equally to 2 groups. The first group was given 5,000 Haemonchus contortus and 20,000 Trichostrongylus colubriformis larvae. The 24 additional goats remained free of parasites. Parasitologic, serologic, and milk data were collected every 2 weeks for 5 months, and body condition of the goats was scored throughout the study. Results of strongyle egg count in feces, increase in pepsinogen values, and reduction in RBC count, PCV, and serum inorganic phosphate concentration indicated subclinical infection, This subclinical parasitism induced a decrease in body condition scoring and led to persistent decrease in milk yield, ranging from 2.5 to 10% reduction from control values. Changes in fat and protein contents were not detected. In contrast, the consequences of infection were more severe in the 6 goats with the highest milk production at the start of the study. Decrease in milk output ranged between 13.0 to 25.1%, and was associated with decrease in fat content. Comparison of the response to parasitism in the 6 goats with the highest lactation performance and the 6 goats with the lowest performance indicated differences be- tween both subgroups. According to parasitologic and pathologic data, high-producer goats had less resistance and/or resilience to infection associated with more severe consequences on milk production.