Horses
can develop a rapid onset form of acute diarrhoea, or more long term,
chronic diarrhoea with loose ‘cow pat’ like droppings.
The
underlying causes of diarrhoea can be related to age, breed, diet and
use.
It
can be caused by ingestion of certain feeds, microbial contamination
of feed and/or water, viral infection and internal diseases, such as
chronic liver disease, gastro-intestinal ulcers, ingestion of sand,
food allergies and fungal toxins in feed, heavy worm burdens, bowel
or organ cancers and drug induced diarrhoea
Horses
which become nervous due to handling, pre-competition ‘nerves’
and travelling can develop ‘cow pat’ droppings for a few hours.
Diarrhoea
can be basically separated into the following types relative to the
underlying cause.
Acute,
Painful Diarrhoea
This
type of diarrhoea is usually associated with an elevated body
temperature and colic-like signs with inflammation of the small or
large intestine as a result of bacterial infection (most often
Salmonella spp) and Clostridial Colitis ‘X’ infection.
Salmonella
spp diarrhoea is most common in young horses, being spread by
adult ‘carrier’ horses which exhibit no signs. Young horses under
crowded conditions or stress are susceptible, as are horses drinking
contaminated dam water or grazing grassy areas frequented by wild
ducks or poultry, which are often carriers of Salmonella spp.
Clostridia
perfringen Type A diarrhoea is associated with a severe colicy,
debilitating colitis, often referred to as ‘Colitis X’. It was
initially thought to be due to a viral infection. It can cause a high
temperature with rapid liver and kidney toxaemia, severe dehydration,
shock and death within 24-36 hours. Infection is thought to be water
borne, such as septic tank run-off or creek water contaminated with
sewerage. It
Drug-induced
secondary colitis can be caused by high doses of sulphonamide
antibiotics used to treat respiratory disease which allow pathogenic
Streptococcus spp, Salmonella spp or Clostridia spp, as well as
fungal organisms to multiply producing a mycotoxin–induced
diarrhoea, which can lead to a severe toxaemia.
Chronic
Diarrhoea
In
many cases, it is difficult to diagnose the underlying cause of a low
grade chronic diarrhoea which develops and persists over 2-3 weeks or
longer, with ‘cow pat’ droppings and often without an elevated
temperature. It is usually a result of intestinal ulceration, sand
ingestion, feed allergies or feed related toxins and often has a
characteristic odour. This type of diarrhoea often.leads to weight
loss and ill-thrift, chronic dehydration and lack of energy to
exercise and the need to daily clean a scour soaked tail. Aged horses
over 30 years can develop the ‘scours’ as their bowels
deteriorate and reduced absorption of feed proteins and other
nutrients occur especially if they have poor teeth.
Common
causes include:
Heavy
Small Strongyle burdens - long term use of a resistant worming
compound or heavily contaminated grazing/yard areas. Often a brown
scour with a distinctive ‘dead’ tissue odour. Check for high
Strongyle worm egg count above 500 eggs per gram in droppings. Rotate
worming compound, dose twice, 3 weeks apart to control heavy burdens,
then adopt a strategic worming program and rotate, rest and
rigorously clean pastures to reduce recontamination.
Sand
ingestion - most common in foals and young horses. A higher
incidence occurs under drought conditions when horses graze closer to
the soil surface, or after heavy rain which splashes sand onto the
plants which the horses then consume as they graze, or even flooding
after rain. Horses grazing pasture or confined to yards with soils
based on fine ‘beach-like’ sand are most likely to accumulate
sand as they graze or eat hay off the ground. Check droppings for
sand and feed psyllium husks. Young foals and growing horses can
develop a ‘pica’ or craving to eat sand when bored or when not
enough feed is provided. It is best to provide hay and avoid grazing
them on pasture based on fine sandy soils.
Excess
or rapid grain intakeby a horse in training - often soft, pastey
‘cow pat’ droppings with a sour odour containing whole grain. It
is best to slow down grain intake by cutting 100mm square box heavy
weldmesh to fit into feeder to prevent gorging and offer smaller more
frequent feeds.
Succulent
grass intake in grazing horse results in a ‘sloppy’ green,
slimey scour with a pungent odour often after break of season in
horses hungry for a ‘green’ pick. Limit access to green lush
clover or lucerne based pastures to 2 hrs per day and provide hay in
a hay rack until pasture matures and has a lower moisture content
(more dry matter content). The scour usually clears up after 3-4 days
in these cases.
Treatment
and Control
- A
key component to treating moderate to severe diarrhea is the use of
isotonic intravenous fluid replacement to maintain hydration and
electrolytes, and to correct acid-base imbalances.
- Intravenous
plasma replacement restores proteins and provides the horse with
immunoglobulins (infection-fighting antibodies).
- Oral
intestinal protectants such as bismuth subsalicylate, activated
charcoal, ori-tri-octahedral (DTO) smectite can be used to reduce
toxin uptake through the permeable bowel lining.
- Analgesics
(pain relievers) such as NSAIDs are used to control pain and diminish
adverse effects of endotoxin.
- Other
medications such as polymyxin B, DMSO, or pentoxyfylline also can be
administered to limit the effects of endotoxin on the body and
perhaps reduce the incidence of secondary complications such as
laminitis.
- Management
approaches to prevent diarrhea include modifying feeding practices to
curtail sand ingestion.
- Also
provide your horse with good-quality forage and routine dental care
to avoid bowel irritation related to coarse or poorly chewed feed.
- Reference
The
Mercks Veterinary Manual
