Diagnostic Laboratory Rounds (cont.)


and rattlebox (southeast US) are common culprits. Hors- es consume these weeds when more appropriate grazing material is not present, as occurs in drought conditions. Fortunately these plants tend to have a bitter taste and horses won’t consume them when good forage is pres- ent. A horse needs to consume about 2% of its own body weight in PA-containing plants in order to develop liver failure.


Feed toxins that are culprits of liver damage are myco- toxins or aflatoxins. Tese fungi can be present in moldy feeds and it is not possible to tell if the toxin is present by a visual examination. Stored grains are screened for my- cotoxins and aflatoxins, but not all. One of the problems with evaluating feeds for mycotoxins is that pockets of the fungus can be present in otherwise normal product. Tis makes it difficult for the owner or the veterinarian to evaluate the presence of this toxin.


Both plant toxin and feed toxin damage are cumulative through the lifetime of the horse. Small amounts over time can do the same damage as a large dose all at once.


Diagnosis


Serum blood tests are great for determining that the liver is damaged. However, the levels don’t reflect how much functional liver tissue remains. In serum testing, damage


to the biliary tract is indicated by GGT (gamma-glu- tamyl transferase) and ALP (alkaline phosphatase) while damage to the hepatocytes is indicated in SDH (sorbitol dehydrogenase) and AST (aspartate amino- transferase) levels. Serum bilirubin levels can point to biliary obstruction.


Requesting serum bile acid levels, however, can give the veterinarian indications about liver function. Bile acid levels are good prognostic indicators of chronic disease. Elevated bile acids are associated with inflammation and fibrosis in the liver, both of which can interfere with he- patic function. Horses have no gall bladder and bile is secreted into the small intestine all the time. Because it is constantly being secreted, fasting is not necessary to get valid results and only one test is necessary. In mammals that have a gall bladder (like humans and dogs), two bile acid tests are necessary: the first fasting and the second following a meal.


Te most definitive answers for liver disease can come from a liver biopsy and histopathology. According to a paper by Dunkel and Jones, the best prognostication of long term survival of a horse with liver disease was biopsy and histopathology. Large animal veterinarians may not be comfortable with this procedure in the equine outside of a referral practice. Measuring bile acids appears to be a reasonable alternative to an invasive procedure. 


Veterinary responders can learn their role in livestock or poultry emergencies with online course


The impact of an animal disease outbreak will have serious consequences. Ensuring that all responders un-


derstand the impact, the terminology used, and actions required will produce a more rapid and coordinated re- sponse.


Te Center for Food Security and Public Health (CF- SPH) at Iowa State University College of Veterinary Medicine is now offering a web-based course, Animal Disease Emergencies: Understanding the Response. Te cost for the course is $100. To find out more and to register, visit http://www.cfsph.iastate.edu/ADE-Course/.


Tis web-based, awareness level course is designed for anyone who may be involved in an animal disease re- sponse – veterinary and animal health responders, live- stock or poultry producers and industry groups, wildlife managers and officers. Traditional responders, including


emergency managers, law enforcement, firefighters, pub- lic health, will also benefit and learn about roles they may have during a response.


Te course is approved for 4.0 hours of veterinary con- tinuing education credit in jurisdictions which recognize AAVSB RACE approval.


Connie Scovin, Development Coordinator Center for Food Security and Public Health Institute for International Cooperation in Animal Biologics 2160 Iowa State University College of Veterinary Medicine


Ames, IA 50011 Cell 515-520-9200 Email cscovin@iastate.edu http://www.cfsph.iastate.edu/ 


Spring/Summer 2018 23


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