Assessment of myocardial function in the horse. 2. Experimental findings in resting horses

The paper describes observations on 8 horses at rest using catheter-mounted microtransducers to record intracavity pressures. In 5 of them records were obtained from both left and right sides and in 3 horses from the right heart only. Twelve indices were measured. Variations in left ventricular end-diastolic pressure seemed to influence the results on many of the parameters. It is suggested that left ventricular end-diastolic pressure itself may be a useful guide to left ventricular functional efficiency but more work is necessary to further evaluate these indices as possible measures of myocardial function in the horse.     

Equine monocytic Ehrlichiosis (Potomac horse fever) in horses in Uruguay and southern Brazil.

A disease named locally as churrío or churrido equino (i.e., equine scours) has occurred for at least 100 years in Uruguay and southern Brazil in farms along both shores of the Merín lake. This report describes cases of churrido equino and provides serologic, pathologic, and DNA-based evidence indicating that the disease is in fact equine monocytic ehrlichiosis (Potomac horse fever). Results of an epidemiological investigation conducted on an endemic farm are also presented. Clinical signs in 12 horses were fever, depression, diarrhea, dehydration, and sometimes colic and distal hind limb edema. Postmortem findings of 3 horses were of acute enterocolitis. Inclusion bodies containing ehrlichial organisms were found in the cytoplasm of macrophages of the large colon of 1 horse. Eleven of the 12 horses were serologically positive to Ehrlichia risticii (indirect fluorescent antibody assay) and, of 3 paired samples, 2 showed seroconversion. Ehrlichia risticii DNA was identified by a nested polymerase chain reaction in peripheral blood of an affected horse. A healthy horse inoculated with peripheral blood from an affected horse developed the disease and antibodies to E. risticii. The disease had a peak incidence in March (summer) and was statistically associated with a marshy ecosystem near the Merín lake, where large numbers of Pomacea spp. (Ampullariidae) snails were found. Incidence density was almost 8 times higher in nonnative horses than in native horses. It was concluded that the previous diarrheic disease of horses known in Uruguay and southern Brazil as churrido equino is equine monocytic ehrlichiosis.     

Pathologic findings in reintroduced Przewalski's horses (Equus caballus przewalskii) in southwestern Mongolia.

The Przewalski's horse (Equus caballus przewalskii) was extinct in the wild by the mid 1960s. The species has survived because of captive breeding only. The Takhin Tal reintroduction project is run by the International Takhi Group; it is one of two projects reintroducing horses to the wild in Mongolia. In 1997 the first harem group was released. The first foals were successfully raised in the wild in 1999. Currently, 63 Przewalski's horses live in Takhin Tal. Little information exists on causes of mortality before the implementation of a disease-monitoring program in 1998. Since 1999, all dead horses recovered (n = 28) have been examined and samples collected and submitted for further investigation. Equine piroplasmosis, a tick-transmitted disease caused by Babesia caballi or Theileria equi, is endemic in Takhin Tal and was identified as the cause of death of four stallions and one stillborn foal. In December 2000, wolf predation was implicated in the loss of several Przewalski's horses. However, thorough clinical, pathologic, and bacteriologic investigations performed on dead and surviving horses of this group revealed lesions compatible with strangles. The extreme Mongolian winter of 2000-2001 is thought to have most probably weakened the horses, making them more susceptible to opportunistic infection and subsequent wolf predation. Other occasional causes of death since 1999 were trauma, exhaustion, wasting, urolithiasis, pneumonia, abortion, and stillbirth. The pathologic examination of the Przewalski's horses did not result in a definitive diagnosis in each case. Several disease factors were found to be important in the initial phase of the reintroduction, which could potentially jeopardize the establishment of a self-sustaining population.     

Methicillin-resistant Staphylococcus aureus in horses and horse personnel.

Fortunately, MRSA infection and colonization are currently uncommon in veterinary medicine. Nevertheless, the increasing reports of the occurrence of MRSA infection in horses, veterinarians, and equine personnel dictate that serious consideration be given to the control of this pathogen in veterinary hospitals as well as in the equine community. It is unclear whether extrapolation from human hospitals and people in the community is appropriate; however, given the rapid increase in nosocomial MRSA in human hospitals and the recent shift of certain clones of MRSA into the community, it would be unwise to ignore this potential pathogen. If equine MRSA did, indeed, originate in the human population, complete eradication in the equine population is unlikely, regardless of the prevalence of infection in horses and the intensity of infection control measures, without concurrent eradication of MRSA in the human population, which is surely an impossible feat. Early institution of appropriate surveillance and other infection control measures should be used to attempt to limit the impact of MRSA in veterinary medicine, however. It has been stated, "The time to act is now, before the prevalence of MRSA in the community begins to rise and we end up with 50% of the community strains becoming methicillin-resistant". This statement was directed at control of MRSA in people; however, it is equally relevant in the veterinary context and should receive strong consideration.     

Disease features in horses with induced equine monocytic ehrlichiosis (Potomac horse fever)

Fifty-five horses were inoculated IV and/or SC with materials containing Ehrlichia risticii, ie, infected whole blood, buffy coat cells, or cell culture, to study clinical and hematologic features of equine monocytic ehrlichiosis (Potomac horse fever). Major clinical and hematologic features of induced E risticii infection were biphasic increase in rectal temperature with peak increases of 38.9 C and 39.3 C on postinoculation days (PID) 5 and 12, respectively; depression; anorexia; decreased WBC count (maximal decrease of 47% on PID 12); and diarrhea from PID 14 to PID 18. Increased WBC count was an inconsistent feature, with a maximal increase of 51.5% on PID 20. During times of decreased and increased WBC counts, lymphocyte/neutrophil ratios remained fairly constant. However, not all horses had all clinical and hematologic features, and these features were present in different degrees among horses. Increased rectal temperature, depression, anorexia, and decreased WBC count were more consistent features, whereas diarrhea developed in 73% of the horses. Of 55 horses, 39 (71%) had all clinical and hematologic features of the disease (classic disease), whereas 16 (29%) horses did not have greater than or equal to 1 of these features (nonclassic disease). The E risticii titer in the blood (ehrlichemia) was maximum during the peak increase in rectal temperature. In 55 horses, mortality was 9%. Significant differences (P greater than 0.5) in clinical and hematologic features were not detected between horses that survived and those that died of E risticii infection.     

Enterocolitis caused by Ehrlichia sp. in the horse (Potomac horse fever)

Potomac horse fever was reproduced in 15 ponies by transfusion of whole blood originally from two natural cases and subsequently from ponies infected by the transfusions. Incubation periods varied from 9 to 15 days. Affected ponies developed varying degrees of fever, diarrhea, anorexia, depression, and leukopenia. Eleven affected ponies were killed, three died in the acute phase of the disease, and one did not show clinical signs. The most consistent post-mortem findings were fluid contents in the cecum and large colon, and areas of hyperemia (of inconstant degree and distribution) in mucosae of both small and large intestines. Multifocal areas of necrosis occurred in mucous membranes. Ehrlichial organisms were most common in the cytoplasm of epithelial cells, macrophages, and mast cells of the large colon.     

Ultrasonographic findings post laryngoplasty in the horse

Laryngoplasty is commonly used to treat laryngeal hemiplegia in Thoroughbred racehorses. Evaluation of the success of the laryngoplasty is traditionally determined using endoscopy. Laryngeal ultrasonography and normal ultrasonographic appearance have been reported in the standing horse, but post‐laryngoplasty and ventriculectomy ultrasonographic evaluation has limited literature coverage. A prospective case series of 10 Thoroughbred racehorses with left laryngeal hemiplegia was examined ultrasonographically and endoscopically prior to 3‐10 days, 30‐50 days, and 6‐12 months after laryngoplasty and ventriculectomy. Anatomical structures and Plica vocalis movements were described and measurements and gradings analyzed by repeated means analysis of variance (P < .05). Postsurgical ultrasonographic visualization of Ventriculus laryngis entrances was possible. The distance between Plica vocalis in exhalation was significantly larger than that during inhalation (P < .05). Pre‐ and postsurgical caudal Basihyoideum and rostral Cartilago thyroidea depth was significantly different in some instances (P < .05). No significant differences in the Muscularis cricoarytenoideus lateralis measurements were found. Complications in the extra‐luminal structures were found in seven horses including soft tissue swelling, seroma, and hematoma. A luminal Plica vocalis abscess and Plica vocalis granuloma were also detected ultrasonographically. Ultrasonography can be used to evaluate the post‐laryngoplasty horse for assessing the success of the procedure, monitoring healing, and detecting complications.     

Bronchoalveolar lavage findings in horses with exercise intolerance.

Significant differences were detected by bronchoalveolar lavage (BAL) between horses racing successfully and those showing exercise intolerance. Neutrophil percentage, haemosiderophage percentage and total bacterial numbers were significantly elevated in horses with exercise intolerance. BAL provided a more accurate indication of the incidence and extent of exercise induced pulmonary haemorrhage (EIPH) than visual inspection.     

Mast cell tumours (mastocytosis) in the horse: A review of the literature and report of 11 cases

Mast cell tumours are uncommon tumours in horses, compared to some other species of domesticated animals. They are most frequently located in the skin, but they can also arise at other sites, including the upper respiratory tract and eye. Cytology or histopathology is required for diagnosis. Treatment options include surgical excision, laser ablation, cryotherapy, intralesional injection of corticosteroids or water, and radiotherapy. Malignant and systemic forms are very rare.     

Ultrasonographic findings in horses with cholelithiasis: eight cases (1985-1987)

Cholelithiasis and/or obstructive biliary tract disease was diagnosed ultrasonographically in 8 horses, 5 to 15 years old. Ultrasonographic findings revealed greater than normal amount of hepatic parenchyma in the right side of the abdomen in 8 horses and in the left side in 3 horses. The echogenicity of the liver was greater than normal, and thick distended bile ducts were seen in all horses. Choleliths were imaged ultrasonographically in 6 horses. Subsequently, postmortem findings in 6 horses revealed periportal and intralobular fibrosis, moderate bile duct dilatation, proliferation, and cholestasis. One or more choleliths were found in all horses. Ultrasonographic findings accurately depicted the histologic changes in the hepatic parenchyma in horses with cholelithiasis.