Infectious agents in acute respiratory disease in horses in Ontario.

A study of acute respiratory disease in horses in Ontario was undertaken to determine the identity of current causative infectious agents. A nasopharyngeal swab was designed and utilized to maximize isolation of viruses, mycoplasma, and pathogenic bacteria. Serum samples were collected for parallel determination of antibody titers to equine influenza virus type A subtype 1 (H7N7) and subtype 2 (H3N8), equine rhinovirus types 1 and 2, equine herpesvirus type 1, Mycoplasma equirhinius, and Mycoplasma felis. Equine rhinovirus type 2 was recovered from 28/92 horses tested, and equine influenza virus type A, subtype 2, was recovered from 5. The mycoplasma and bacteria isolated were consistent with those commonly associated with nonspecific respiratory diseases in horses, except that Streptococcus pneumoniae capsular type 3 was isolated from 10 horses.

Use of high-speed cinematography and computer generated gait diagrams for the study of equine hindlimb kinematics.

High-speed cinematography with computer aided analysis was used to study equine hindlimb kinematics. Eight horses were filmed at the trot or the pace. Filming was done from the side (lateral) and the back (caudal). Parameters measured from the lateral filming included the heights of the tuber coxae and tailhead, protraction and retraction of the hoof and angular changes of the tarsus and stifle. Abduction and adduction of the limb and tarsal height changes were measured from the caudal filming. The maximum and minimum values plus the standard deviations and coefficients of variations are presented in tabular form. Three gait diagrams were constructed to represent stifle angle versus tarsal angle, metatarsophalangeal height versus protraction-retraction (fetlock height diagram) and tuber coxae and tailhead height versus stride (pelvic height diagram). Application of the technique to the group of horses revealed good repeatability of the gait diagrams within a limb and the diagrams appeared to be sensitive indicators of left/right asymmetries.

Use of scintigraphy for the determination of mucociliary clearance rates in normal, sedated, diseased and exercised horses.

Mucociliary clearance rates from the trachea were determined in normal, sedated, diseased and exercised horses from scintigraphs obtained after an injection of technetium-99m sulphide colloid into the tracheal lumen. The group mean tracheal clearance rate of eight clinically normal horses during 42 trials was 2.06 +/- 0.38 cm/min. Significant between horse differences were found (p less than 0.05). When six and seven of these horses were given xylazine and detomidine hydrochloride, respectively, mean group tracheal clearance rates dropped significantly (p less than 0.05). The decreases from each normal horse's mean tracheal clearance rate ranged from 18 to 54%. There did not appear to be a difference between the tracheal clearance rates (TCRs) of the normal horses and those with chronic respiratory disease. Postexercise evaluations were not significantly different from the pre-exercise TCRs in three clinically normal horses and three horses with chronic obstructive pulmonary disease (p greater than 0.05). This minimally invasive scintigraphic technique for determining TCRs has proved to be useful and reliable.

Bronchoalveolar lavage of cranial and caudal lung regions in selected normal calves: cellular, microbiological, immunoglobulin, serological and histological variables.

Of a group of 30 clinically normal male Holstein calves two to eight weeks of age, six two week old and six four week old calves met various radiographical and clinicopathological criteria for normality. Bronchoalveolar lavage was performed by fiberoptic bronchoscopy on cranial and caudal lung regions in all 30 calves and samples analyzed for free cells, microorganisms, and immunoglobulins. Lateral chest radiographs and lung biopsies were also conducted on each calf. Calves were euthanized and necropsied ten days after bronchoalveolar lavage was conducted. Reported in this paper are results from the 12 normal calves. Microorganisms were present in small numbers in the lower respiratory tract of some normal calves. There were no differences in the above parameters between cranial and caudal lobes. There were statistically significant changes in bronchoalveolar lavage cell proportions with age although there were no detectable differences in clinical signs. Four week old calves had a lower percentage of macrophages and a higher percentage of epithelial cells than two week old animals (p less than 0.05). There was also a trend toward an increased percentage of neutrophils in older calves but this was not significant (p greater than 0.05). Total bronchoalveolar lavage protein also appeared to increase with age (p less than 0.05). In both groups a higher proportion of IgG2 in bronchoalveolar lavage compared to serum was found, suggesting the presence of a local selective transfer mechanism into respiratory secretions.

The rates and patterns of survivorship and disease in a university dairy herd.

The rates and patterns of disease occurrence and survivorship were determined over a six year period in a university operated dairy herd. Of the ten diseases selected for study, clinical mastitis occurred most frequently with an incidence rate of 10.1% and displaced abomasum occurred least frequently with an incidence rate of 4.4%. The occurrence of all disease except those of the ovary was associated with the age of the cow. Mastitis, pneumonia and cystic graafian follicles tended to reoccur in the same cow after the initial occurrence. The average culling rate was 25.6% and the median number of years cows survived in the herd was 3.4 years. Methods for calculating the various rates and survivorship are described and their interpretation discussed.

The association between disease, production and culling in a university dairy herd.

The impact of ten diseases of dairy cattle on milk production, calving interval and culling were studied in a university operated dairy herd. Cows with clinical mastitis, ketosis or displaced abomasum had lowered milk production. Cows with metritis, retained placenta, cystic graafian follicles or ovarian hypofunction had longer calving intervals. Cows with clinical mastitis, metritis, pneumonia or retained placenta had increased risks of culling. The relationship between disease and culling was based on the medical history of culled and nonculled cows using a case control approach. Therefore, it is likely that in many cases, the association between disease and culling is due to the impact of that disease on productivity.