Weanling ADR (Ain't Doing Right)
We've survived the summer, and with cool(er) weather soon on its way we are now into what I like to call "weanling season" (which follows naturally after "foal season"). One of the common things veterinarians get called about at this time of year is 5-6 month-old foals that just "aren't right." They may not be growing well, they may be skinny, they may not have the same healthy haircoat as other foals in the same group, and they may generally just be "dragging their heels" a bit - not very energetic, and maybe sometimes a little depressed. Of course this is particularly problematic in the fall when some farms are trying to get their foals ready for sale, and they want them looking their best!
Bloodwork on these scraggy foals often shows low - sometimes extremely low - protein levels in their blood. Blood protein is very important for normal body function and controlling tissue fluid levels, and the body (especially the liver) works very hard to maintain normal levels. Low blood protein (also called hypoproteinemia) in these animals usually indicates that the protein is being lost from the body, and the most common route for this to happen is through the intestine. (It can also be lost through the kidneys, but renal disease in young animals is generally uncommon.) Some of these foals have diarrhea as well, or may go on to develop diarrhea if left untreated.
What is it that turns a foal's intestine into a protein sieve? One possibility, and a hot research topic at the moment, is the bacterium Lawsonia intracellularis, which causes the condition known as proliferative enteropathy. But any severe infection of the intestine has the potential to affect the barrier that normally keeps blood protein fluids in the bloodstream, so other causes of enteritis and colitis such as Salmonella and Clostridium also need to be considered. Heavy burdens of intestinal parasites can cause similar problems - some of these may be difficult to test for because the larval stages do not produce eggs that can be found on a fecal test, and developing resistance issues mean that routine deworming cannot guarantee that parasites are not present. There are no doubt other causes as well that haven't been identified - in half of all diarrhea cases in (adult) horses, a causative agent cannot be identified, even with a complete diagnostic work-up.
In horses, if only the small intestine is affected (enteritis) - even in severe cases - the animal usually will not have diarrhea. However, if the infection spreads to the colon, or if the bacterial populations in the colon are affected badly by the foal's poor health status and abnormal "flow" of feed material due to the infected intestine "upstream", then colitis will develop as well, resulting in diarrhea. Anytime the normal intestinal bacteria of a horse are disrupted, the animal also becomes more susceptible to other bacterial pathogens such as Salmonella and Clostridium as well.
What should be done with these "scraggy" weanlings?
1. Have them examined by your veterinarian as soon as possible. Don't wait for them to start looking really sick. These weanlings can be frustrating to diagnose and treat at the best of times, but the farther they're allowed to slip, the harder it is (and the longer it takes) to bring them back.
2. Look for other foals that might be affected. Especially in larger groups of foals, one particularly sick animal may stand out, but there could be several others flying just under the radar that you may not notice unless you really take the time to look at each foal individually.
3. Separate healthy weanlings from those that aren't 100%. It may be difficult or impossible to individually isolate all the "scraggy" animals depending on numbers and the facilities available, particularly more severely hypoproteinemic foals that may take weeks to months to recover. At a minimum, the foals that appear healthy should be separated from and always handled before the ones that may be affected by an intestinal infection. Any animal with diarrhea should be isolated. The duration of isolation required will depend on the specific diagnosis (if one can be made).
More information about Lawsonia is available on the equIDblog Resources page and in our archives.
Image source: www.virginiawildhorserescue.com
