Page 865 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

840 CHAPTER 4

VetBooks.ir Antimicrobial-associated diarrhoea antimicrobial administration in salmonellosis is
directed at prevention and treatment of extraintes-
Diagnosis of antimicrobial-associated diarrhoea is
based on a temporal association of antimicrobial
administration and onset of clinical signs. Specific tinal infection. Concerns about the use of antimi-
crobials include prolonging shedding of Salmonella
pathogen testing should be performed. (if present), development of antimicrobial resistance
and further disruption of the intestinal microflora.
Idiopathic colitis Oxytetracycline (6.6 mg/kg slowly i/v q12 h
Idiopathic colitis is a diagnosis of exclusion that is for 3–5 days) is indicated in cases of diagnosed
made when other known causes of enterocolitis have or highly suspicious PHF. Typically, a response
been ruled out. is noted within 12 hours. Abatement of fever is
usually the first sign of improvement, followed
Management by improvement in attitude and appetite. If no
Aggressive supportive therapy, particularly fluid response is noted within 24–48 hours, the diagno-
therapy with large volumes of balanced electro- sis should be reconsidered.
lyte solution, is the most important component of Di-tri-octahedral smectite (1.5 kg/adult horse
treatment. Intravenous fluid therapy is required in p/o, followed by 450 g p/o q6–8 h) may be useful
all but the mildest of cases. Intravenous hypertonic as an adsorbent. Saccharomyces boulardii (25–50 g p/o
saline (4–6 ml/kg of 5–7% NaCl) may be useful q12 h) may be beneficial. Other probiotics are widely
in severely dehydrated horses but must be followed used; however, there is no evidence of efficacy at this
by large volumes of isotonic fluids. Supplemental time.
potassium, magnesium or calcium may be Horses that are not displaying signs of abdomi-
required, and supplementation should be based nal pain should be fed grass hay ad libitum. Small
on monitoring of blood electrolyte levels. Ionised volumes of concentrates may be gradually intro-
calcium should be measured, if possible, because duced to horses that require additional caloric
total calcium levels will decrease if the horse is intake. Most horses with moderate to severe coli-
hypoalbuminaemic, while the metabolically active tis will lose significant body condition, regard-
total calcium may be normal. Sodium bicarbonate less of dietary intake. Parenteral nutrition may
is rarely required, even in severely acidotic ani- be required in cases where feeding is withheld for
mals, as aggressive fluid therapy will correct the more than a few days.
acid–base status in most cases. Total protein levels Affected horses require intense monitoring to
should be monitored because severe hypoprotein- detect changes in clinical condition and develop-
aemia can develop. ment of complications. Laminitis, the most severe
Endotoxaemia is very common, regardless of complication, is addressed elsewhere (see p. 68) but
the aetiology. Flunixin meglumine (1.1 mg/kg i/v) all four feet should be iced continuously during the
is indicated but should be used judiciously in dehy- acute inflammatory stage of the disease.
drated horses. Polymyxin B (6,000 IU/kg i/v q12 h) All horses with colitis should be assumed to be
may be used to bind endotoxin. infectious until proven otherwise. Salmonellosis is
Metronidazole (15–25 mg/kg p/o q8–12 h) transmissible to horses and is zoonotic. C. difficile
appears to be effective in the treatment of clostrid- can be transmitted between horses and may also
ial diarrhoea and many cases of idiopathic colitis. be a zoonotic disease. The risk of transmission of
Metronidazole-resistant strains of C. difficile are rare C. perfringens is probably lower, but precautions
but have been reported. The use of broad-spectrum should still be taken. PHF is not transmissible
antimicrobial therapy is controversial. Parenteral by horses. Idiopathic cases should be treated as
antimicrobial therapy is mainly indicated to protect infectious.
against bacterial translocation and is not necessary in In all cases where a transmissible disease is con-
most cases. Antimicrobial therapy (e.g. sodium peni- sidered possible, precautions should be taken to
cillin/aminoglycoside) is often indicated in neonates decrease the risk of transmission to other horses
and immunocompromised individuals. Parenteral and to humans. Ideally, affected horses should be