Bovine Wart Virus Linked To Canker

A clinical investigation into the underlying cause of equine hoof canker was conducted in Austria. Tissue samples from 24 canker specimens were examined for the presence of viral DNA from the papilloma virus that causes warts in cattle and has been associated with sarcoid tumors in horses. Most of the patients were warmbloods. On average they were 12 years old. Most were well cared for and presumably living in good, relatively clean environments. Tissues from 13 horses without canker were similarly examined as controls.

The viral DNA was found in all of the canker specimens. Most of the skin biopsies and blood samples from affected horses were also positive for the DNA. None of the canker patients were affected by sarcoid skin tumors. This along with the discovery that the specific variants of the virus found in the canker cases are also those associated with sarcoids led the researchers to suggest the canker patients likely acquired the viral infections from other horses rather than from cows. They also concluded effective treatment for canker might be improved by using antiviral medication and immune modulators, some of which have been effective for sarcoids.

—Brandt S et al. EVJ 2011;43:202-209.

Rattlesnake Bite Effect Quantified

A retrospective, descriptive study was conducted to better understand the most common characteristics of rattlesnake bites to horses in Northern California and identify factors associated with survival. The medical records of two referral hospitals were searched to identify 58 cases of rattlesnake bite. A scoring system was used to help describe the severity of cases in relation to the outcome.

The age of patients ranged from 1 month to 28 years with a median of 7 years. Breeds seemed to be represented in proportions that might be typical for the referring population of horses. Most bites occurred during the summer and 97% of bites were to the face. Head swelling was present in 97% of cases with swelling progressing down the neck in 32% of cases and respiratory distress in 57%. The median severity score (total possible score 13) for horses that survived was 4 and the median score for the 9% of horses that died was 10.

Treatment was mostly supportive but 57% of horses required a tracheostomy to maintain an airway. Antivenin was used to treat 16% of the horses. While none of the horses that received antivenin died the authors point out that additional research is need to better understand the best and most cost effective treatments for snake bite in horses.

—Fielding CL et al. JAVMA 2011;238:631-635.

Hoof Surface Strain Change Tested

An experimental study was conducted with 18 normal Standardbreds to measure how hoof wall strain distribution changes over time and in response to exercise. Strain gauges attached to the hooves were used to measure the principle surface strains during trotting at the toe and at the lateral and medial quarters. Half the horses were exercised 4 days each week at a trot in a straight line on a crushed limestone track for 4 months. The control horses were not exercised.

Strain distribution changed over time for both exercised and control horses. Exercise did not appear to affect the midstance maximal principle strain, but it did change with time in both quarters of all horses. Midstance and peak minimal principle strains were higher in the quarters of the exercised group at the beginning of the study, but higher in the toe and not the quarters of the controls at the end of the study.

The authors point out that not only did the absolute value of measured strains change with exercise, but exercise also reduced variability of measured strains. There seemed to be more change in the measured parameters in the quarters compared with the toe. More work may be needed to fully understand how hoof wall strains change over time and relative to exercise, but it does seem clear that mechanical properties of the hoof wall are not static.

To this reader, it seems equally likely these changes represent adaptations to exercise, loading and the environment.

—Faramarzi B et al. AJVR 2011;72:484-490.

Hydraulic Hoof Tester Shows Promise

For centuries the application and interpretation of hoof testers have been heavily dependent on the skill and experience of the operator. This study evaluated the reliability and ease of use of a hydraulically driven hoof tester that measured the force applied by hydraulic cylinders when applied to three locations on the solar surface. The operator controlled the final amount of pressure applied through the same type of subjective feedback used when applying manual hoof testers, that is releasing a button to release the pressure in response to the reactions of the horse.

On average, laminitic horses seemed twice as sensitive as normal horses. Variability of measurements in any particular normal horse was seen from one session to another for no apparent reason. The authors concluded that the pressure required to evoke a response can be safely and reliably measured using these hoof testers, but estimated that treatments would need to produce at least a 40% improvement if their efficacy was to be detected in this manner.

— Vinuela-Fernandez I et al. EVJ 2011;43:62-68.