EQUINE VETERINARY EDUCATION / AE / MAY 2015


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Highlights of recent clinically relevant papers


Diagnosis of Rhodococcus pneumonia In this recent study, Macarena Sanz and colleagues in the USA and Iceland evaluated methods of diagnosing Rhodococcus pneumonia in foals. Current methods of diagnosis of Rhodococcus


pneumonia include PCR from a tracheobronchial aspirate or imaging techniques to detect bronchopneumonia. Detection of infection prior to clinical signs and allowing differentiation of cases that are mild enough to resolve without treatment is a challenge. ELISAs have previously been investigated but were problematic due to interference with maternally derived antibodies and antibodies produced as a result of environmental exposure. This study investigated an ELISA detecting a specific virulence associated protein (VapA) for subclasses of IgG. This test is in current use but its performance characteristics are not known. Serum samples were collected from both exposed and non-exposed adult horses to validate the ELISA and samples from pneumonic and healthy foals were used to assess the diagnostic performance of the ELISA. The VapA-specific IgG(T) subclass was found to have both high sensitivity and specificity for the detection of infected foals and significantly outperformed the other subclasses of VapA-specific IgG. The VapA specific IgG(T) shows potential to be used as a


means of identifying infected foals although the test still requires assessment under field conditions.


Use of CT to assist internal fixation in the hoof


This retrospective study by Janik Gasiorowski and Dean Richardson performed at the University of Pennsylvania, USA, describes the clinical use of computed tomography (CT) and hoof surface markers to aid internal fixation in the equine hoof.


The 16 horses in this study had CT-guided internal fixation


of either the distal phalanx (DP) or distal sesamoid bone (DSB). The drill bit entry point and direction were planned from CT images of the hooves with grids of barium paste dots at the proposed entry and exit sites. Screw position and length, as well as fracture reduction, were checked on CT images following surgery. The time taken during each stage of this procedure and the outcome were recorded. In all horses the position and length of the screws were


considered near optimal, with no malposition of bits or screws, and fracture reduction was evident in all cases. The preoperative planning time (at least 2 CT image acquisitions and grid creation) was 10–20 min, surgery time was 45–90 min and general anaesthesia time was 115–220 min. The authors concluded that the combination of CT and


surface marker grids allowed accurate positioning of screws in clinical DP and DSB fractures and that this technique was quick and simple.


Horses undergoing repeated celiotomy


In this retrospective case study, Bettina Dunkel and colleagues in the UK examined the factors associated with short- and long-term prognosis for horses undergoing repeated celiotomy within 14 days of the first colic surgery.


Historical, clinical and laboratory data for 95 horses that had


undergone 2 celiotomies within a 14-day period were compared between horses that did not survive and horses that survived to hospital discharge (short-termsurvival rate) and to >3 and >6 months after hospital discharge (long-termsurvival rates). The most common finding during the first celiotomy was


strangulating small intestinal lesions (63.2%) and the most common reason for the second celiotomy was persistent gastric reflux (58.9%). Reasons for a second celiotomy were not found to be associated with survival rate. For horses that had long-term follow-up, 23.9% survived >6 months after hospital discharge. Two of 13 horses with intestinal resections during both surgeries survived to >6 months after hospital discharge. Significantly fewer horses requiring resection during one or both surgeries survived to hospital discharge and to >3 and >6 months after hospital discharge, compared with horses not undergoing intestinal resection. Of horses that survived to hospital discharge, incisional infections occurred in 68.4%, and 31.6% developed incisional hernias or dehiscence. These results indicate that the prognosis for horses undergoing repeated celiotomy is guarded, and intestinal resection negatively affects the long-termsurvival rate.


IgE food allergen testing inconsistent


Sofie Dupont and colleagues in Belgium and the Netherlands have recently evaluated a commercially available immunoglobulin E-based (IgE) test for food allergy in healthy ponies. IgE testing of serumsamples is commercially available and is


offered as a diagnostic aid for dietary allergies in equines. This method has been shown to be unreliable in humans and other species but has not previously been tested in equines. In this study blood sampleswere taken from 17 healthy Shetland ponies and submitted for IgE testing. Blood samples were repeated 14 days later to assess the reliability of the test. Six ponieswere found


to have a positive result to one ormore dietary allergens with the first sample and 7 ponies on the second sample; only 3 were positive on both occasions and only one was positive to the same allergen on both occasions. Thereafter, ponies testing positive were exposed to the dietary allergen during provocation tests. Allergens were introduced individually in the case of multiple allergens, with a washout period of one week between. Clinical parameters, including inflammatory markers were monitored in this time. The results from the first and second screening differed significantly, therefore the test was not found to be consistent. No pony showed any adverse reaction during the provocation testswith the suspected allergen. IgE testing for the detection of food allergies in horses was


not found to be a consistent or reliable test with positive results found in healthy horses.


Comparison of cardiac troponin assays


Different cardiac troponin I (cTnI) assays give different results and there are currently few studies of troponin T (cTnT) in horses. In this study Nicky Van Der Vekens and colleagues in Belgium compared cTnI and a high-sensitive cTnT assay (hs- cTnT) in horses.


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