During the spring of the first year of a vaccine study, 57 of 238 calves (24%), in which modified-live Pasteurella haemolytica vaccine (MLV) was injected twice, developed 1 or more abscesses. Abscesses were not observed after multiple visual examinations of 437 calves given killed P. haemolytica bacterin or placebo injections of similar adjuvants used in the vaccine and bacterin. Calves that developed abscesses after the second injection of MLV weighed significantly (P < 0.05) less (on the basis of body weight adjusted for weaning weight) at the second injection than did those that did not develop abscesses. Compared with calves given MLV that did not develop observable abscesses, calves developing abscesses after the second injection of MLV weighed 11.0 and 14.2 kg less, respectively, at 56 days and 112 days after injection, and they had 11.0 kg less gain at 56 days after injection. Abscess prevalence tended to be highest on certain days or at certain locations used for cattle processing, and the prevalence of abscesses increased in cattle processed later on a given day. Abscesses were not observed in 2 other groups of similarly treated calves vaccinated in the autumn or in the subsequent spring.

The 1-host tick Boophilus annulatus was found to transmit anaplasmosis in cattle transstadially. Anaplasma marginale was invariably transmitted when ticks that had been pulled off Anaplasma-infected calves either after 7 days (as fully engorged larvae) or after 14 to 15 days (as fully engorged nymphs) were transferred within 4 days to susceptible calves. Three morphologically different A marginale isolates, 1 round (tailless) and 2 with different types of appendages (tailed) were transmitted by the ticks. These findings might explain the overlap of the geographic distribution of the disease and that of Boophilus spp in some areas of the world.

Pili have been implicated as virulence factors that result in increased infectivity of Moraxella bovis, the causative agent of infectious bovine keratoconjunctivitis (IBK). Healthy calves' eyes were inoculated with I- or Q-piliate or nonpiliate M bovis Epp63 to compare the pathogenicity of these isogenic variants. Pathogenicity was determined by the rate of persistent M bovis infection and the prevalence of clinical IBK. Inoculation with M bovis expressing the Q pili resulted in the highest frequency of infection and IBK whereas I-piliate M bovis elicited a lower rate and nonpiliate M bovis did not result in infection. In vivo pilin gene rearrangement and pilin-type switching were evaluated by DNA hybridization and immunoblot. Gene rearrangement and type switching varied dependently, and were observed only in eyes inoculated with Q-piliate M bovis. This study suggests that Q pili are specific for colonization of bovine corneal epithelium, whereas I pili enable maintenance of an established infection.

Bovine leukemia virus (BLV) infection and culling of cows in a commercial dairy herd were evaluated to determine whether a relation existed between the 2 factors. Cattle from the study population, a Holstein dairy herd consisting of approximately 400 milking cows, were tested for antibodies to BLV, using the agar gel immunodiffusion test, semiannually for 2 years, annually for 2 years, and when cattle were culled. Complete records of BLV test results were available for 849 (79%) of the 1,078 cattle that had at least 1 test during the study period. Using the Cox hazard model, the cull hazard rates (culls/cow-months) were greater for BLV seropositive cows than for seronegative cows > 36 months old. Hence, among older dairy cows, BLV-infected cows were culled prematurely, compared with uninfected cows.

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.

Spontaneous variations in ECG and continuous Holter monitor recordings of a colony of 31 male and 31 female cynomoigus monkeys were characterized. Electrocardiograms recorded for approximately 1 minute on 2 occasions in nonsedated monkeys were analyzed, and intervals (PR, QRS, and QT), amplitudes (P, Q, F, and T), and heart rate were determined from lead II of these tracings. In addition, Holter monitor recorders were placed on monkeys by use of carrying jackets for 16 to 24 hours of continuous recording twice during the study, and tapes were analyzed. Mean heart rate and intervals and amplitudes were similar for males and females on the first and the second recordings, Mean heart rate for males and females was 232 and 226 beats/min (bpm), respectively. The PR, QRS, and QT interval measurements, 77, 29, and 165 milliseconds, respectively, were recorded for males and 81, 30, and 162 milliseconds, respectively, were recorded for females. The P, Q, R, and T wave amplitudes were 0.16, 0.11, 0.64, and 0.28, mV respectively, for males and were 0.17, 0.10, 0.79 and 0.24 mV, respectively, for females. In addition, ventricular ectopic beats were observed in ECG from 5 females, but not in ECG from the males. Single ventricular ectopic beats were observed in 3 females for either the first or second tracing. One monkey had ectopic beats in both tracings, but in both instances, the number of ectopic beats was low (3 singles in the first and 1 in the second tracing). One monkey had runs of pairs and bigeminal beats in only the first tracing. One monkey had sporadic beats indicative of right bundle branch block morphology in both tracings. In Holter recordings, ventricular ectopic beats were identified in 47 monkeys. Ventricular ectopic beats were observed in only 1 of the 2 Holter monitor tapes for 53% of these monkeys. Most ventricular ectopic beats occurred as single beats, but pairs, ventricular tachycardia, and bigeminy also were observed. Ectopic beats were of a single morphology in 60% of the monkeys, but as many as 4 different morphologies were observed in a single tracing. Sinus arrhythmia or arrest was observed in 66% of the monkeys. Ventricular ectopic beats and sinus arrhythmia can occur without apparent cause in clinically normal monkeys. Higher prevalences of these abnormalities are identified by Holter monitoring relative to routine ECG procedures. These variables should be cautiously evaluated, because the lack of proper characterization of monkeys on test may mislead investigators as to the real importance of these findings.

A serologic survey was conducted to determine the prevalence and seroconversion rates for ovine adenovirus (OAV) serotypes 1-4 and bovine adenovirus (BAV) serotypes 2, 3, and 7 in sheep in Iowa and in surrounding states. For 2 consecutive years, paired serum samples were obtained from 1- to 2-month-old lambs as they entered a ram test station and, again, 2 months later. Sera were tested for adenovirus antibodies by use of a microtitration serum virus-neutralization test. At the time of entry, high prevalence of antibody (titer greater than or equal to 2) was detected to all tested adenoviruses except BAV-3. All adenoviruses were active in the ram test station both years, as indicated by greater than or equal to fourfold increase in adenovirus antibody titer (seroconversion) in some of the lambs. The prevalence and seroconversion rate for OAV-1 was 94.0 and 7.2%, respectively; for OAV-2, 98.6 and 15.1%; for OAV-3, 86.5 and 11.0%; for OAV-4, 98.4 and 13.2%; for BAV-2, 97.6 and 22.4%; for BAV-3, 11.4 and 3.8%; and for BAV-7, 81.6 and 4.5%. The results indicate that adenovirus infections were widespread in the sheep population and that the prevalence of active infection based on seroconversion rates was approximately 45%.