Diarrhea in Horses


Diarrhea is an increase in the water content of the feces and/or
the frequency of defecation. Fourteen to 50 percent of all foals
have diarrhea. A few causes of diarrhea are self-limiting after a
few days, it stops and the foal is not harmed. However, some
causes of diarrhea can result in dehydration, acid base and
electrolyte imbalance as well as death. Any foal with diarrhea
should be carefully observed as they can deteriorate fast.

Most outbreaks of foal diarrhea are caused by rotavirus.
Overcrowding and poor hygiene have been associated with
such outbreaks.

Foals with rotavirus become depressed, lose their appetite
and normally have a fever. Diarrhea usually follows in 12 - 24
hours and may last for two to three days, but may linger for
nine days. Foals may become dehydrated, have an electrolyte
imbalance and may die from hypovolemic shock. Intravenous
fluids are required if foals become dehydrated. They also
need intensive care.

Rotavirus is extremely contagious. The virus is shed in the
feces; affected foals may infect other foals.
Unfortunately, the organism may live in the environment for as
long as nine months. If foals become sick with rotavirus
diarrhea, do not remove "healthy" foals from the barn,
thinking you will prevent the spread of the disease. Once an
outbreak of rotaviral diarrhea occurs, all horses should be
considered exposed.

It is easier to try and prevent rotavirus diarrhea than it is to
treat it. It is imperative that mare owners disinfect stalls
before foaling.

Individuals that handle a sick foal must wash their hands with a
povidoneiodine scrub. A phenolic solution should be used as a
foot bath for anyone entering the stall with a sick foal, and all
equipment should be disinfected with a phenolic solution.

Salmonellosis is the most common cause of bacterial diarrhea and
enteritis in foals. Signs are depression, colicky pain and
profuse watery diarrhea. Due to the risk of septicemia,
antibiotics may be used. However, antibiotics can aggravate
diarrhea. Carriers and environmental contamination are the
primary sources of infection. Stress and overcrowding of foals
should be avoided.

It has long been known that internal parasites can cause
diarrhea in foals. Unless the foal's dam is treated shortly after
foaling, foals normally ingest Strongyloides westeri from the
mare's milk. Deworming mares the day of foaling reduces the
problem.

The most common cause of diarrhea is foal heat, which occurs
seven to 12 days after birth and corresponds to the mare's first
estrus after foaling. Foal heat diarrhea is usually self-limiting
unless there is a need to replace lost fluid and electrolytes.

It is important to keep the foal's rear quarters clean. Gently
wash their buttocks with warm water and a mild detergent or soap,
then rinse thoroughly. Apply a thin coat of petroleum jelly or
zinc oxide over the buttock. This procedure should be used with
all foals observed to have persistent diarrhea. One of the most
common causes of mild, non-organism diarrhea is due to excess
milk consumption. Excess milk intake may occur in very young
foals. With an orphan foal, too much milk replacer may be fed, or
it may be too concentrated or too dilute.

Diarrhea can interfere with normal foal growth, result in long
treatment periods and may be fatal. In addition to good
disinfecting practices, a number of other practices will aid in
reducing the incidence of foal diarrhea. Straw bedding, normally
recommended for foaling mares, is better than shavings. A large
number of foals, 94 percent, born on shavings had diarrhea, while
only 43 percent of those foaled on straw had diarrhea. It is not
advisable to use antibiotics when a foal is born. Foals treated
with an antibiotic as a preventative measure at foaling are at a
greater risk of developing diarrhea. It should be noted that
employment of these practices did not eliminate foal diarrhea,
but it greatly reduced its occurrence. Due to cost of treatment
and time-consuming care and the risk of foal diarrhea, initiating
these managerial practices in combination with a thorough
disinfection program as previously outlined is worthwhile.