GROSS AND HISTOPATHOLOGIC CORRELATION OF LOW‐FIELD MAGNETIC RESONANCE IMAGING FINDINGS IN THE STIFLE OF ASYMPTOMATIC HORSES

With the recent introduction of a 0.25T rotating MRI system, clinical evaluation of the equine stifle joint is now possible in the average equine athlete. A recent publication described common abnormalities of horses with stifle lameness detected with a low‐field MRI system; however, postmortem corroboration of the lesions detected was not possible. Therefore, our objective was to compare postmortem findings with low‐field MRI findings in equine cadaver stifle joints. Ten fresh cadaver stifle joints from horses without clinical signs of stifle disease were evaluated using low‐field MRI, gross dissection, and histopathology. In eight stifles, either the lateral or medial cranial meniscotibial ligament had an irregular shape, fiber separation, or moderate abnormal signal intensity (SI) on all sequences. In five stifles, the medial femoral condyle had articular cartilage fibrillation with or without an osteochondral defect over the weight bearing surface of the medial femoral condyle. All stifles had abnormal SI on all sequences within the patellar ligaments that corresponded with adipose tissue infiltrating between the collagen bundles. Other abnormalities identified included articular cartilage fibrillation of the tibial condyles in three stifles, and articular cartilage fibrillation with chondral defects in the patella in three stifles. All abnormalities detected with low‐field MRI were corroborated by gross dissection. Findings from the current study supported the use of low‐field MRI for detection of stifle joint lesions in horses and demonstrated that some stifle joint pathologies may be subclinical in horses.     

Thyroid-stimulating hormone: response test in healthy horses, and effect of phenylbutazone on equine thyroid hormones

Adult horses showed a mild diurnal variation in equine plasma thyroxine (T4) concentrations, but not triiodothyronine (T3). Plasma T4 concentrations tended to be higher between 5 PM and 8 PM than at 8 AM. Increases in plasma T4 and T3 were similar in adult healthy horses given 5, 10, or 20 IU of thyroid-stimulating hormone (TSH). The T4 peaked at approximately twice (2.0 +/- 0.4 times) as high as the base line at 6 to 12 hours after the TSH was given. The greatest change from base line T3 occurred at 1 to 3 hours after the TSH was given, but the magnitude of increase was widely variable (4.36 +/- 2.49 times as high as base line). The following method for doing the equine TSH-response test was suggested: (i) prepare plasma or serum sample for determining base line T4 and T3, (ii) inject 5 IU of TSH IM, (iii) prepare plasma or serum samples at 3 and 6 hours after the TSH was injected, and (iv) freeze samples at -20 C until T4 and T3 determination by radioimmunoassay. Treatment of horses with phenylbutazone for 5 days caused a significant decrease in base line T4 and T3 in horses (P less than 0.05). However, phenylbutazone-treated horses responded to the injection of TSH, and the increase in T4 at 6 hours was greater than in the controls (not given phenylbutazone) (P less than 0.02).     

Serologic study of the incidence and prevalence of bluetongue infections in cattle in the Mexican states of Nuevo Leon,Tamaulipas, Coahuila and San Luis Potosi

Serum samples from 2156 cattle in 40 herds in northeastern Mexico were tested for antibody activity to bluetongue virus. In addition, animals from 5 other herds were sampled each month to determine when new infections were occuring. Prevalence rates ranged from 7 to 100%, with a herd average of 42%. New infections occurred on each of the five ranches sampled monthly. Attack rates for the study period were 9, 63, 22, 18 and 57%.     

Inclusion of licuri meal in the diet of pasture dairy cows

Tropical Animal Health and Production - The objective of this study was to evaluate the inclusion of increasing levels of licuri meal as a substitute for soybean bran in the diet of pasture-based...     

Pharmacokinetics of transdermal flunixin in sows

The objective of this study was to describe the pharmacokinetics (PK) of flunixin in 12 nonlactating sows following transdermal (TD) flunixin (3.33 mg/kg) and intravenous (IV; 2.20 mg/kg) flunixin meglumine (FM) administration using a crossover design with a 10‐day washout period. Blood samples were collected postadministration from sows receiving IV FM (3, 6, 10, 20, 40 min and 1, 3, 6, 12, 16, 24, 36, and 48 hr) and from sows receiving TD flunixin (10, 20, 40 min and 1, 2, 3, 4, 6, 8, 12, 16, 24, 36, 48, 60, and 72 hr). Liquid chromatography and mass spectrometry were used to determine plasma flunixin concentrations, and noncompartmental methods were used for PK analysis. The geometric mean ± SD area under the plasma concentration–time curve (AUC) following IV injection was 26,820.59 ± 9,033.88 and 511.83 ± 213.98 hr ng/ml for TD route. Mean initial plasma concentration (C₀) was 26,279.70 ± 3,610.00 ng/ml, and peak concentration (C_max) was 14.61 ± 7.85 ng/ml for IV and TD administration, respectively. The percent mean bioavailability of TD flunixin was 1.55 ± 1.00. Our results demonstrate that topical administration is not an efficient route for delivering flunixin in mature sows.     

Distinctive histopathologic features of canine optic nerve hypoplasia and aplasia: a retrospective review of 13 cases

Canine optic nerve hypoplasia (ONH) and aplasia (ONA) are significant neuro-ophthalmologic disorders that have been reported in several species. The purpose of this study was to describe the distinctive histopathologic features of ONH and ONA in canine patients identified from a collection of 20 000 ocular submissions at the comparative ocular pathology laboratory of Wisconsin from 1989 to 2006. The following information about ONH and ONA cases was collected: signalment, and clinical and gross findings, including unilateral vs. bilateral involvement. Microscopic evaluation was performed, with attention to optic nerve malformation, retinal ganglion cell (RGC) and nerve fiber layer (NFL) loss, and retinal disorganization. The distribution of retinal vasculature was recorded and a search for unusual findings of ONH and ONA was performed. Information and histologic documentation was available for 13 cases. Eight cases of ONH and five cases of ONA were identified. The average group age was 20.2 months and 16.1 months, respectively. The most common breed was the Shih Tzu (3/13). ONH usually presented bilaterally (7/8); all ONA cases presented as a unilateral disease (5/5). The morphologic findings in the optic nerve (ON) in ONH included variable degrees of ON hypoplasia and gliosis, as well as ectopic vestigial ON remnants within orbital nerves and connective tissues. The NFL was detected in the majority of the ONH cases; however, RGCs were rare or absent. Mild retinal disorganization was seen occasionally. Most cases of ONH were associated with regional peripheral retinal blood vessel extension into the vitreous, leaving the peripheral retina avascular. In ONA cases the retinal blood vessels, NFL and RGCs were totally absent and retinal disorganization was severe. Distinctive microscopic features encountered in ONA included anterior segment dysgenesis in some cases. The retina in these cases was stretched across the posterior lens capsule, never making contact with the posterior pole of the globe. The current study reviews the human and veterinary literature pertaining to ONH and ONA, compares ONH and ONA in dogs, and presents related ophthalmic histopathologic findings that have not been reported previously.     

Epizootic of fatal amebiasis among exhibited snakes: epidemiologic, pathologic, and chemotherapeutic considerations.

An epizootic of reptilian amebiasis seems to have caused the death of 15 to 16 large and valuable captive snakes (boas, pythons, and anacondas) occupying one of 5 large display dioramas in the Steinhart Aquarium of the California Academy of Science, Golden Gate Park, San Francisco. Subsequent review of previous snake deaths in the colony indicated that of 464 snakes that had died since early 1969, 89 snakes had intestinal or hepatic lesions, and 80 of these snakes had pathologic features which involved severe intestinal ulceration, hemorrhage, and massive enteritis, with or without hepatic necrosis and destruction, condition compatible with Entamoeba invadens infection. The present epizootic began in November, 1972, with the death by acute enteritis of a red-tailed boa constrictor (Boa constrictor amarali) and was followed by the loss of 15 other large boids and pythonids. The affected snakes became immobile, refused to feed, and began to die 10 weeks after the death of the red-tailed boa. Seven boa constrictors, 4 pythons, and 4 anacondas from the same diorama died during the ensuing 10 weeks. Entamoeba invadens trophozoites were identified in the stool of the remaining living snake, a 3-m boa constrictor, and in the liver and the intestinal tissue of 1 of the dead boas examined microscopically. The parasite was also found in the stool of a giant Burmese python (Python molurus bivittatus) that died in the adjacent diorama and in the tissues of a blue-tongued skink (Tiliqua scincoides), separately housed, that died of enteritis during this period. Amebic cysts were recovered from turtle and alligator fecal samples taken from a central "swamp," or reservoir, draining the dioramas, water that is returned to the snake display areas after passage through a biological sand-gravel filter and ultraviolet radiation exposure. Cultures from these stools were positive and proved lethal to an experimentally infected boa constrictor. Treatment of the surviving snake in the affected diorama with metronidazole at the dose rate of 275 mg/kg proved rapidly effective; toxicosis was not observed. Other snakes and lizards suspected of having the infection were similarly treated and returned to normal behavior and feeding patterns. Epidemiologic considerations review the probable mode of introduction and spread of this highly lethal snake pathogen and recommendations are made for avoiding infection, prophylactic treatment, and handling of similar epizootics when they do occur among captive reptiles in aquariums, zoos, and research laboratories.