Page 841 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

816 CHAPTER 4

VetBooks.ir Prognosis anorexia may worsen as dehydration develops. Young
foals are usually more severely affected, while older
With appropriate treatment, the prognosis for
affected foals is reasonable. Prognosis is worse in
cal clinical course is 3–5 days in duration, but diar-
foals with severe weight loss and hypoproteinae- foals may only develop very mild disease. The typi-
mia. Some foals may be so weak that they become rhoea may persist for longer periods in some cases.
recumbent. These foals carry a poor prognosis, even Signs of toxaemia and sepsis should not be present.
with aggressive support including parenteral nutri-
tion. Rapid clinical response to therapy has been Differential diagnosis
observed; however, gross small-intestinal changes Foal heat diarrhoea, salmonellosis, clostridial enteri-
and hypoproteinaemia require weeks to months to tis and parasitic diarrhoea should be considered.
resolve.
Diagnosis
ROTAVIRUS ENTERITIS Identification of rotavirus in faeces via enzyme-
linked immunosorbent assay (ELISA), a latex agglu-
Definition/overview tination test or electron microscopy is the clinical
Rotavirus is a common cause of diarrhoea in foals standard for diagnosis, but interpretation is com-
less than 3–6 months of age. Foals as young as 1–2 plicated by the potential for rotavirus shedding by
days of age can be affected. In some areas, rotavirus subclinical carriers. For this reason, it is prudent to
may be the most commonly identified cause of diar- also test for Salmonella, Clostridium difficile and C. per-
rhoea in young foals. Outbreaks are not uncommon. fringens to identify coinfection. Diagnostic testing
is important for identification of disease for which
Aetiology/pathophysiology specific treatments are indicated (e.g. clostridial
A variety of different equine rotavirus serotypes have enteritis) and for determining appropriate infection-
been identified. Rotavirus is prevalent in the horse control practices.
population and most horses are likely to be exposed
early in life. Foals are infected via the faecal–oral Management
route. Following ingestion, rotavirus invades villus Specific management depends on the severity of dis-
epithelial cells in the small intestine. Fluid absorp- ease and the age of the foal. Very young foals are
tion is decreased, and secretion can be increased. more likely to require intensive treatment. Fluid
Lactase-producing cells that reside at the tips of the therapy is the most important aspect of treatment.
villi may be damaged, and secondary lactose intoler- Intravenous fluid therapy with a balanced electro-
ance may be an important aspect of this disease. lyte solution is often required in dehydrated foals.
Foals can shed rotavirus, and be a source of Nutritional support may be required, particularly in
infection before clinical signs develop, while diar- young foals. Diagnosis and management of lactose
rhoeic and for variable lengths of time after resolu- intolerance should be considered and is covered else-
tion of disease. Some foals can shed rotavirus for where (see p. 819).
up to 8 months. While adult horses do not develop Rotavirus is not invasive, nor does it typically
clinical disease, they may be a source of infection. cause significant mucosal damage, therefore the
Rotavirus can persist in the environment for long risk of bacterial translocation is low and antimicro-
periods of time (up to 9 months in some situations); bial therapy is not usually indicated. Antimicrobials
therefore, once on a farm, rotavirus can be difficult should be considered in young, severely compro-
to eradicate. mised foals and in any case where septicaemia is
suspected.
Clinical presentation Infected foals and their dams should be isolated.
Most affected foals are diarrhoeic, mildly depressed, Good general farm management including imple-
partially anorexic and pyrexic. Other signs may mentation of isolation and quarantine protocols and
precede diarrhoea by 24 hours, and depression and proper disinfection is very important for prevention