Biomedical subjects
Publications and source records attributed to W C Rebhun.
Most ocular and orbital injuries or acute ocular inflammation in horses result in similar signs of adnexal swelling, photophobia, blepharospasm, and lacrimation. It is hoped that detailed examination and the suggestions in this article will enable veterinarians attending horses having ocular emergencies to arrive at a correct diagnosis and appropriate therapy.
In Holstein cattle, an inherited disease has been recognized recently in which leukocytes lack surface glycoproteins termed beta 2 integrins, which are important in cell adhesion processes. This disease is the homologue of leukocyte adhesion deficiency in human beings and has been termed bovine leukocyte adhesion deficiency. The molecular basis of this disease is failure to produce normal CD18. The gene encoding bovine CD18 and its abnormal mutation have been sequenced, allowing specific diagnosis of the condition by DNA amplification by polymerase chain reaction followed by specific endonuclease digestion. This test was applied to formalin-fixed archival tissues from 18 cattle that had been admitted to the veterinary medical teaching hospital between 1975 and 1991 and that had had persistent and severe neutrophilia. Blood samples were collected from 2 additional cattle, and leukocytes from these samples also were tested. Fourteen cattle were confirmed to have been homozygous for the bovine leukocyte adhesion deficiency gene. Cattle with this condition had ranged in age from 2 weeks to 8 months at admission. They typically had had chronic bacterial infections that had failed to respond to or had recurred after conventional treatment. Consistent findings in these cattle included signs of bronchopneumonia, gingivitis, periodontitis, and peripheral lymphadenopathy. Severe neutrophilia, usually without a left shift, was a hallmark of the disease; consistent clinical biochemical findings included hypoalbuminemia, hyperglobulinemia, and hypoglycemia. This disease is important because it mimics common calfhood diseases such as pneumonia and diarrhea, but is ultimately consistently fatal before adulthood.
A 9-year-old Quarter Horse mare was examined because of progressive weight loss, weakness, muscle atrophy and tremors, and behavioral change. Selenium and glutathione peroxidase assays, blood lead analysis, erythrocyte transketolase analysis, pseudorabies and Borrelia burgdorferi serology, electromyography, and CSF analysis were performed. Motor neuron degeneration was diagnosed by microscopic examination of neural tissues. The cause of the disease was not substantiated, but several possibilities were excluded via diagnostic testing. Diagnosis of motor neuron degeneration in horses may be made from an accurate history, thorough neurologic examination, and ancillary testing. In particular, antemortem diagnosis may be based on finding scattered angular atrophy of predominantly type-1 or of type-1 and -2 skeletal muscle fibers in frozen sections of muscle biopsy specimens.
The effect of prior Rhodococcus equi-induced pneumonia on pulmonary health was investigated in 5 horses (< 24 months old) using endoscopy, radiography, hematologic and bronchoalveolar lavage analyses, and pulmonary function testing. Rhodococcus equi-induced pneumonia had been diagnosed in principal horses when they were foals. Diagnosis was based on positive results of transtracheal aspiration and thoracic radiography at the time of initial clinical examination. Results of reevaluation of the respiratory system of these horses (R+) were compared with those of 5 age-matched healthy horses (R-) that lacked clinical or historical evidence of foalhood pneumonia. Significant differences in variables between the 2 groups of horses were not evident. In both groups, most horses had radiographic evidence of an accentuated bronchointerstitial pattern, although results of analysis of bronchoalveolar lavage specimens were normal and mononuclear cells predominated. Variability in results of the pulmonary function tests was observed within the between the 2 groups of horses. Only normalized dynamic lung compliance was slightly lower in the previously infected horses, but this difference was not significant. We concluded that horses previously infected with and successfully treated for R equi-induced pneumonia do not have detectable evidence of residual lung damage.
A diaphragmatic hernia was found in a pre-partum dairy heifer that was exhibiting signs of respiratory disease. Ruminal tympany was included in the history although this was not a feature of the disease on admission. Diagnosis was made by auscultation and confirmed by radiology and during elective Caesarean section to remove the fetus.
This paper describes two cases of infection of the soft palate and pharyngeal wall in cattle. The infections were secondary to trauma and laceration received during treatment with an oral calcium preparation which was given to treat post-parturient hypocalcemia. Clinical signs included dehydration, depression, pseudoptyalism, and fetid breath. Other signs involved the upper respiratory and gastrointestinal tracts. Digital oral examination revealed the traumatized regions. Treatment included antibiotics and non-steroidal antiinflammatory agents. A semipermanent rumenostomy was performed on one cow for fluid and nutritional maintenance, but she died from secondary septic peritonitis. The second cow survived.
Selective IgM deficiency was diagnosed in a 3-month-old Standardbred colt that was referred for chronic respiratory tract disease. Immunoglobulin quantification revealed normal IgG and IgA concentrations, but undetectable IgM concentration. Stimulation of blood lymphocytes with the T-cell mitogens concanavalin A and phytohemagglutinin yielded results within the normal range. However, stimulation with the B-cell mitogen lipopolysaccharide produced no response. A B-cell defect similar to that associated with several immunodeficiency disorders in people was suggested as the cause of the IgM deficiency in this colt.
Chronic frontal sinusitis in 12 dairy cattle most often was associated with a history of dehorning, in which the sinus was entered (67%), or with respiratory tract disease (25%). The most common organisms isolated were Actinomyces pyogenes and Pasteurella multocida. Signs of infection did not develop for months in some cattle and were often intermittent. The most common clinical signs included anorexia, lethargy, fever, frontal bone distortion, exophthalmos, abnormal posture, nasal discharge, and neurologic abnormalities. Treatment consisted of trephination at 2 sites, drainage and lavage of the sinus cavity, and administration of antibiotics and analgesics. Eight cattle responded well to treatment and were discharged, but 4 others had signs of CNS involvement and died or were euthanatized. Trephination of the frontal sinus cavity at carefully chosen sites and antibiotic treatment are indicated when sinusitis is suspected. Drainage of the sinus cavity is imperative to avoid extension of the infection into the CNS.
Fourteen cows were subjected to thoracotomy as an aid in the treatment of either septic pericarditis (n = 7) or unilateral pleuritis (fibrous or purulent; n = 7). Thoracic lesions were primary in 4 cows, secondary to traumatic reticuloperitonitis in 9 cows, and secondary to extension of a liver abscess in 1 cow. Thoracotomy was performed on 9 cows under local anesthesia. Surgery was performed on 5 cows under general anesthesia; 2 died during anesthesia, and 2 others were euthanatized. Of the 10 cows allowed to recover from surgery, 4 had pericarditis and 6 had pleuritis. Four cows with pleuritis had thoracic abscesses. All but 1 cow with pericarditis died or were euthanatized, and 5 of the 6 cows with pleuritis were discharged from the hospital. A year after surgery, 1 cow was culled because of infertility, and the other 5 cows were returned to production.
Basic knowledge of the normal appearance and variations of the equine fundus coupled with frequent practice in ophthalmology will allow equine practitioners to be confident when assessing the equine fundus during ophthalmic examinations. Once the normal variations are mastered, appreciation of retinal, choroidal, optic nerve, and vitreal abnormalities is possible. Congenital and acquired lesions of the equine retina, optic nerve, and vitreous are discussed and illustrated.
A retrospective case-control study was conducted to identify risk factors in horses associated with the development of the common skin tumours known as sarcoids. The study involved 503 sarcoid cases diagnosed (January 1980-December 1989) at New York State College of Veterinary Medicine and a similar number of controls (non-sarcoid cases). Data on age, breed and sex of cases and controls were obtained from computerised records. Multiple logistic regression analysis was used to identify risk factors. Separate data were obtained for the same 10-year period from the Veterinary Medical Data Program to determine the proportional morbidity rate at different veterinary colleges in North America. Appaloosa, Arabian and Quarter horses were at a higher risk of developing sarcoid tumours than were Thoroughbred horses. Standardbred horses had a lower risk of developing sarcoids. Geldings were at a higher risk of developing sarcoids in comparison with stallions. There was no significant difference in the risk of developing sarcoids between stallions and mares. The risk of developing sarcoid increased with age up to 15 years and then declined. The proportional morbidity rate of sarcoids among the veterinary colleges ranged between 0 and 14 per 1,000 cases, with an average of 6 per 1,000.
A 6-year-old Quarter Horse was examined because of acute, severely swollen masseter muscles (palpation of which elicited pain response), exophthalmos, severe chemosis, and protrusion of the third eyelids. Blood selenium and vitamin E concentrations, and results of feed analysis and muscle biopsy supported a diagnosis of nutritional myopathy. The horse was treated and was clinically normal 2 weeks after discharge from the hospital.
A 12-year-old Morgan gelding was examined for colic of 3 days duration. Signs of depression, colic, diarrhea, and endotoxemia persisted despite aggressive medical therapy and surgical exploration. Culture results from gastric fluid and feces yielded many colonies of Clostridium perfringens. This organism also was recovered from peritoneal fluid 10 days after admission; consequently, the horse was euthanized. At necropsy, a localized gas-filled, necrotic stomach wall was found; many mucosal and submucosal gas blebs were visible. Culture of this tissue yielded Clostridium perfringens. Emphysematous gastritis is a fulminant infection of the stomach wall caused by gas-forming organisms that gain access to the submucosa via mucosal defects such as ulcers. This condition has been reported infrequently in people, and the case reported herein represents the first instance of emphysematous gastritis in the horse.
Medical records of 15 adult cows with a final diagnosis of pyelonephritis were evaluated retrospectively. Only 3 cows had obvious clinical signs that indicated urinary tract disease. Physical examination, including rectal and vaginal examinations, and urine chemical reagent strip screening detected abnormalities in all 15 cows and allowed subsequent confirmation by culture results of urine samples obtained using a catheter. Bacteriologic cultures of urine revealed Corynebacterium renale infection in 6 cows and Escherichia coli infection in 9 cows. Long-term treatment with antimicrobial drugs resulted in recovery in 9 of 11 treated cows. Of these, 4 of 4 cows with C renale infection and 5 of 7 cows with E coli infection recovered; the remaining 2 cows with E coli infection died.
During a 7-year period, failure of omasal transport attributable to a perireticular abscess was diagnosed in 29 cows. Affected cattle were examined because of anorexia, hypogalactia, and bilateral abdominal distention. The cows were all female Holsteins, 15 months to 10 years old. The abscess was identified during exploratory celiotomy and rumenotomy or at necropsy. Traumatic reticuloperitonitis was believed to be the cause. Twenty-seven cattle (93%) were treated surgically. The abscess was drained into the reticulum or omasum in 25 cows (86%). Twenty-four cows (83%) survived to the time of discharge from the hospital, and 20 (69%) survived for at least 1 year and became productive members of the herd. This is a better survival rate than that reported for other causes of vagal indigestion.
Blindness characterized by dilated unresponsive pupils and funduscopic evidence of varying degrees of vitritis, retinal vasculitis, retinitis, chorioretinitis, and optic neuritis developed in 21 alpacas and 1 llama within a 30-day period. The animals were part of a group of approximately 100 animals imported from Chile one year earlier. The animals had spent 6 months in quarantine and then, for the 6 months preceding the epizootic, were housed at an exotic animal import-export farm, where the disease developed. Four of the affected animals also had signs of neurologic dysfunction. A herpesvirus indistinguishable from equine herpesvirus I was isolated from 4 of the affected animals, and antibody titers diagnostic for equine herpesvirus I were demonstrated in the serum of all but one of the affected animals.
Actinobacillus lignieresii is well recognized as the cause of "wooden tongue." We have encountered Actinobacillosis as the cause of granulomas in unusual locations. These lesions have been confused with neoplasms, nasal polyps, or exuberant granulation tissue. Four such cases constitute this report.
The signs of bovine listeriosis include depression and variable cranial nerve deficits indicative of brain stem inflammation. Because a wide range of cranial nerve deficits exists in bovine listeriosis patients, a thorough neurologic examination and cerebrospinal fluid analysis are essential to accurate diagnosis. Treatment should consist of intensive antibiotic therapy owing to the intracellular location of the causative organisms and should also address metabolic acidosis in those patients with loss of buffer because of excessive salivation. The public health implications of bovine listeriosis require the veterinarian to protect all persons attending the bovine patient affected with listeriosis.