REVIEW paper: mare reproductive loss syndrome.

An epidemic of early fetal loss (EFL), late fetal loss (LFL), fibrinous pericarditis, and unilateral uveitis which occurred during the spring of 2001, are together now known as the mare reproductive loss syndrome (MRLS). A similar epidemic with less intensity was reported during the same period of time from southern Ohio, West Virginia, and Tennessee. The same syndrome with lesser intensity recurred in 2002. The estimated economic loss from the syndrome in 2001 and 2002 together was approximately $500 million. Both EFL and LFL were characterized by the absence of specific clinical signs in aborting mares. Nonhemolytic Streptococcus spp. and Actinobacillus spp. accounted for 65% of the organisms isolated from fetuses submitted for a postmortem during the MRLS period in 2001 and 2002. The pathologic findings in fetoplacental units of LFL included bronchopneumonia and funisitis, and there were no findings in EFL. Epidemiologic studies conducted in 2001 suggested an association between the presences of eastern tent caterpillars (ETC) in pastures with MRLS. Experimental studies in pregnant mares by exposure to ETC, or administration by stomach tube or with feed material, reproduced EFL and LFL. Similar experimental studies in mouse, rats, and goats with ETC were unsuccessful. Currently, 2 hypotheses are proposed for MRLS. One hypothesis proposes that an ETC-related toxin with secondary opportunistic bacterial invasion of the fetus leads to MRLS. The second hypothesis suggests that a breach of gastrointestinal mucosal integrity by hairs of ETC leads to a bacteremia and results in MRLS. In 2004, a similar equine abortion storm was reported from Australia and caterpillar exposure was identified as a risk factor for the abortion. In 2006, the syndrome was observed in Florida and New Jersey.

Dystocia in a referral hospital setting: approach and results.

REASONS FOR PERFORMING STUDY: Dystocia in the mare is an emergency in which duration has a profound effect on survival of the foal. Specific examination of the effects of dystocia duration on foal survival provides information to enable horse care personnel and veterinarians to manage these cases more effectively and maximise the chances of obtaining a live foal. HYPOTHESIS: Dystocia duration would have a negative impact on foal survival while method of dystocia resolution would not have an effect on foal survival. Additionally, we were interested in determining the effects of dystocia on subsequent fertility. METHODS AND RESULTS: In the years 1986-1999, 247 dystocias were admitted. Of these, 91 % resulted in survival and discharge of the mare, 42% in delivery of a live foal, and 29% of foals survived to discharge. Period from hospital arrival to delivery for foals alive at discharge (23.0 +/- 14.1 mins) was not significantly different than for foals not surviving (24.8 +/- 10.6 mins) (P > 0.05); and from chorioallantoic rupture to delivery for foals alive at discharge (71.7 +/- 343 mins) was significantly less than for foals not surviving (853 +/- 37.4 mins) (P < 0.05). Average predystocia live foaling rates for all mares with available records was 84%. Overall post dystocia live foaling rates over the entire period of this study were 67%. Of mares bred in the year of the dystocia, 59% had a live foal in the year following. CONCLUSIONS: Based on these results, dystocia duration has a significant effect on foal survival and resolution methods should be chosen to minimise this time, as the difference between mean dystocia duration for foals that lived and those that did not in this study was 13.6 mins. Post dystocia foaling rates reported here are higher than previously reported for both same-season and overall breedings, indicating same-season breeding may be rewarding for select dystocia cases. POTENTIAL RELEVANCE: Dystocia resolution methods that minimise delivery time may maximise foal survival. Post dystoicia breeding may be rewarding in select cases.

Uroperitoneum in the hospitalised equine neonate: retrospective study of 31 cases, 1988-1997.

Historical, physical and diagnostic data were reviewed retrospectively in 31 equine neonates with uroperitoneum. Gender predilection was not observed, and classic electrolyte abnormalities were seen in less than 50% of the cases. Aetiologies for uroperitoneum have been well described, but this review found that septicaemia/severe illness played a crucial role the outcome of uroperitoneum. Approximately half the individuals with uroperitoneum had positive sepsis scores. Foals receiving fluid therapy were more likely to be septic and to have normal electrolyte concentrations. Ultrasonographic findings, serum creatinine and serum:peritoneal creatinine ratios were not affected by previous fluid therapy and were invaluable aids in the diagnosis of uroperitoneum, even with multisystemic disease such as sepsis.

Pharmacokinetics of a high dose of gentamicin administered intravenously or intramuscularly to horses.

OBJECTIVE: To evaluate pharmacokinetics of a high dose of gentamicin administered i.v. or i.m. to horses. DESIGN: Repeated-measures study. ANIMALS: 6 clinically normal female adult stock-type horses. PROCEDURE: All horses were given gentamicin (6.6 mg/kg [3 mg/lb] of body weight), i.v. and i.m., in a two-way cross-over design. Serum gentamicin concentrations were measured during a 24-hour period. RESULTS: Plasma concentration curves were consistent with a two-compartment model. Maximum plasma gentamicin concentrations were 71.9 +/- 15.7 micrograms/ml (0 hours after injection) and 22.0 +/- 4.9 micrograms/ml (1.31 hours after injection) for the i.v. and i.m. groups, respectively. Area under the curve (AUC) was 116.6 +/- 14.5 and 116.3 +/- 14.6 micrograms.h/ml for the i.v. and i.m. groups, respectively. Elimination half-life for the IV group was 3.0 +/- 2.8 hours. Trough concentrations were < 2 micrograms/ml for > 15 and > 12 hours for the i.v. and i.m. groups, respectively. Significant changes were not detected in clinicopathologic variables before and after administration of gentamicin. CLINICAL IMPLICATIONS: Administration of a high dose of gentamicin i.v. or i.m. resulted in peak plasma concentrations, AUC, and minimum trough plasma concentrations. Results indicate once-daily administration of gentamicin might be as efficacious and safe as multiple-dose daily administration in accordance with traditional low-dose regimens, similar to those used in other species.

Idiopathic hypocalcemia in foals.

Five thoroughbred foals (4 fillies and 1 colt), all in good to excellent body condition, ranging in age from 4 days to 5 weeks at the time of onset of signs, were presented to 2 Kentucky equine hospitals from 1992 through 1996. All 5 foals presented with tachycardia, hyperhidrosis, diarrhea or a recent history of diarrhea, and muscle rigidity or stiff gait. Four of the 5 foals presented for recumbency, seizure-like activity with opisthotonos, or pronounced extensor muscle rigidity. All 5 foals were hypocalcemic. All foals either died or had euthanasia performed. None responded to oral calcium supplementation. The cause of the hypocalcemia was unknown. Different idiopathic hypocalcemia syndromes may exist in foals.

Examination of the foal.

Recent advances in veterinary diagnostics have improved our ability to diagnose and treat foal diseases. However, these advances do not replace the physical examination as the most valuable diagnostic aid available to the equine practitioner. The basic physical examination provides the majority of information needed to make a presumptive diagnosis, provide a direction for ancillary tests, and formulate a plan for emergency therapy if needed.

Leptospirosis.

Equine clinical leptospirosis has been primarily related to uveitis and the often recurrent sequelae of ocular changes. Reports of equine hepatic and renal involvement are sporadic. More recently, serovar bratislava has been identified as a host-adapted serovar in the horse. More significantly, reports of equine abortion and stillbirth have become more frequent in the literature. This is more than likely a result of improved diagnostic techniques, not of increased prevalence of disease. In addition to abortion, equine neonatal disease is becoming more frequently recognized in association with leptospira infection. Whether leptospiral infection results in abortion or diseased foals may depend upon the stage of gestation when the mare is exposed and host immune status. Antibiotic of choice for treatment of equine leptospirosis remains speculative, as specific equine studies have not been performed. Extrapolation from other species suggests that the use of streptomycin remains a good choice of therapy for the chronic shedding state and may be used in combination with other antimicrobials for treatment of acute disease. Penicillin or potentiated penicillins and tetracycline at appropriate to high end dosages are logical choices for the treatment of acute leptospirosis.

Hematuria and leptospiruria in a foal.

A Thoroughbred foal that was born after 305 days of gestation was referred 6 hours after birth. On initial examination, the foal was alert, but weak and unable to stand. Heart rate was 150 beats/min, respiratory rate was 48 breaths/min, and rectal temperature was 33 C. Leukocytosis was detected (26,000 WBC/microliters). Dysuria and passage of red urine was observed approximately 30 hours after admission. Urine collected by free catch had a 3+ reaction for blood on dipstick analysis. Examination of Warthin Starry-stained sections of allantochorion revealed organisms morphologically characteristic of leptospira spp along the chorion. Results of direct fluorescent antibody tests on section of placenta were positive for Leptospira spp. Direct fluorescent antibody testing identified leptospires in the urine of the foal. Sera from mare and foal were tested for antibodies against Leptospira spp by use of the microscopic agglutination test. High titers were identified in serum from the mare and foal.

Leptospiral abortion and leptospiruria in horses from the same farm.

Leptospirosis was documented as the cause of abortion in a 5-year-old mare. Leptospires were detected in tissue specimens from fetal kidneys and from placenta by histologic evaluation of silver-stained sections. Antibodies against Leptospira interrogans serovar pomona were detected in fetal serum at a titer of 1,600 by use of a microscopic agglutination test. The mare had serum titers of 6,400; 0; 400; 800; 3,200; and 6,400 to L interrogans serovars bratislava, canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona, respectively. A serologic survey identified titers of at least 6,400 against serovars bratislava and pomona in 5 other horses on the farm. Titers of at least 100 against serovar bratislava were detected in 53% of the horses on the farm. Leptospires were detected by direct fluorescent-antibody testing in urine samples from the mare that aborted and from 2 of the other 5 horses.

Serologic survey for Borrelia burgdorferi antibody in horses referred to a mid-Atlantic veterinary teaching hospital.

Blood samples obtained from 13 of 100 (13%) and 6 of 91 (7%) horses at the George D. Widener Hospital for Large Animals in the months of June and October, respectively, had antibody to Borrelia burgdorferi as determined by ELISA. Horses from the states of New York, Maryland, Delaware, New Jersey, and Pennsylvania were seropositive for B burgdorferi. The frequency of antibody response in horses from New Jersey was greater (P less than 0.05) than the frequency of antibody response in horses from Pennsylvania or that of horses from the other states combined. Statistically significant difference was not found when a comparison was made between horses with serotiter and open diagnosis of neurologic or musculoskeletal disease and horses with negative serotest results and open diagnosis of neurologic or musculoskeletal disease.

Variations in serum sorbitol dehydrogenase, aspartate transaminase, and isoenzyme 5 of lactate dehydrogenase activities in horses given carbon tetrachloride.

Seven horses were given 0.5 mg of carbon tetrachloride/kg of body weight via a nasogastric tube. Subsequent hepatocellular damage was monitored by serum enzyme determinations of sorbitol dehydrogenase, isoenzyme 5 of lactate dehydrogenase, and aspartate transaminase activities. Creatinine kinase activity was evaluated as an indicator of muscle cell damage. Sorbitol dehydrogenase, isoenzyme 5 of lactate dehydrogenase, and aspartate transaminase activities were significantly (P less than 0.05) increased by 24 hours after carbon tetrachloride administration. Isoenzyme 5 of lactate dehydrogenase and sorbitol dehydrogenase activities returned to baseline several days before aspartate transaminase activity returned to baseline. Creatine kinase activity remained unchanged.

Surgical management of duodenal obstruction in an adult horse.

A 3-year-old Standardbred stallion was admitted for treatment of acute enterocolitis. The horse improved in response to empiric treatment, but subsequently developed ventral edema, scrotal abscessation, and severe laminitis. Improvement again was seen, but on day 29 of hospitalization, the horse developed rapid heart rate and signs of abdominal pain. Exploratory celiotomy revealed complete obstruction of the descending portion of the duodenum, 20 cm caudal to the duodenal sigmoidal flexure. Three-tier duodenojejunostomy and jejunojejunostomy were performed to bypass the duodenal obstruction.

Ultrasonographic diagnosis of small-intestinal intussusception in three foals.

Small-intestinal intussusceptions were diagnosed in 3 foals. Cross-sectional ultrasonography through the apex of the intussusceptum revealed a target-like pattern with a thick hypoechoic rim. The thick hypoechoic rim was caused by severe edema of the entering and returning walls of the intussusceptum. At the more proximal portion of the intestines, where parietal edema was less severe, the image appeared as 2 concentric rings and an inner circular area. The outer ring and inner circular area were hypoechoic and represented the returning and the entering wall of the intussusceptum. An additional cross-sectional pattern can be described as double concentric rings, with the inner lumen represented by a central echogenic core. Longitudinal scannings of the involved intestinal section revealed a different view of the same anatomic situation, with 2 hyperechoic areas delineated by 3 stripes of hypoechoic intestine. Ultrasonography of a foal's abdomen provides a clinician with a rapid noninvasive technique that may aid in the differential that may aid in the differential diagnosis of colic. The ultrasonographic diagnosis of intussusception may improve the recognition of a surgical lesion and improve the potential for successful treatment.