When I got a text from my friend saying “the results are in. Rotavirus. Call me for more info.” I’m pretty sure I called her before her finger left the phone after hitting send. She wasn’t surprised. It was baffling to me, and apparently to the internal medicine specialist vet at the clinic, as he called the lab to ask them to double check the tests and run it again. They already had, as they too were baffled after seeing Indy’s age.
(For Indy’s experience and symptoms, see “Indy Calls Out Sick“)
What is so baffling about this diagnosis? Or perhaps you are asking more basic, what is Rotavirus? I was familiar with the disease in preparing for Indy’s arrival, but decided to do a little more digging to get all the facts.
Rotavirus is a viral infection. It is seen in many species, including horses and humans. In the case of equine Rotavirus, it does not have the ability to be transmitted across species, nor from human to horse. In humans, it is very common in young children and typically by the age of 5 they have developed an immunity.
Rotavirus is the most common cause of foal diarrhea. Over 50% of foal diarrhea is caused by Rotavirus, with some studies reporting as high as 70%. Diarrhea can lead to dehydration, malnutrition, electrolyte imbalance, and, albeit rare, death if left untreated.
It is baffling that this is Indy’s diagnosis because it is nearly unheard of for a horse over the age of 6 months to get it. Indy, at 16 months, should have developed immunity and just shed the virus from his system. Foals ingest Rotavirus from infected feces and typically develop symptoms within 1-2 days. Once in the system, the virus replicates in the GI tract and attaches itself to the epithelium of the villi in the small intestine. This then disrupts the digestive process, causing decreased metabolism, absorption, and digestion. It greatly affects water absorption, which contributes to diarrhea. The intestine responds to the large volume of food not being digested by producing more digestive fluids, in an effort to flush the food out of the body. This in turn overwhelms the large intestine, which is responsible for water and fluid absorption, causing more water to pass through the horse, leading to very watery diarrhea.
There is no “cure” for Rotavirus; the only option is to treat the symptoms and wait for it to pass. Rotavirus is highly contagious as the virus replicates extremely quickly. A single foal can shed millions of Rotavirus particles in one small particle of manure. Prevention is key – an affected foal will shed the virus for about 10 days, with a rare possibility of them shedding the virus asymptomatically for a few months. Rotavirus is not affected by bleach and can survive in the environment for up to 9 months. The human strain has also been found in water sources. Pregnant mares can be vaccinated for Rotavirus, however even those foals can still contract the disease, though the symptoms are typically more subdued.
Treatment includes fluid treatment (IV fluids if necessary), electrolytes, probiotics (to help support the hindgut), and, in extreme cases, tubing water and nutrients directly into the stomach.
In Indy’s case, he did not have diarrhea. He had a fever, which in turn caused him to feel lethargic, weak, and reluctant to drink. He may have been having some digestive upset as well, which would explain why he didn’t want to drink. Eating was only an issue when his fever was high.
Our theory is that Indy somehow came into contact with Rotavirus recently, despite not being around any young foals. The virus doesn’t live long in the digestive system as the epithelial cells where the virus lives are always replicating, sloughing off the old ones and constantly creating new cells, so the thought that he had been harboring it for a while is unlikely. Having a strong immune system, Indy didn’t react by getting diarrhea, but rather instead just developed a response to a virus – a fever. There have been some cases of healthy foals who are shedding the virus, but not showing diarrhea. I guess I can be grateful that this means Indy has a very healthy immune and digestive system, and I did pretty good to keep him from being exposed for so long!