Foal diarrhea

Diarrhea is a significant cause of morbidity and mortality in foals. Numerous noninfectious and infectious agents are responsible for enterocolitis and enteritis in the newborn foal. Altered fecal consistency may be associated with uncomplicated diarrhea which often does not require treatment, to life threatening enteritis or enterocolitis with endotoxemia and clinical signs associated with systemic inflammation. Associated metabolic complications include acidosis, hypovolemic shock, hypotension, and bacteremia. Therapy is dependent on the severity, suspected etiology and concomitant complications. Supportive care and rehydration to prevent hypovolemic shock and renal damage can be life threatening. Antibiotic therapy is only required if bacterial enteritis is suspected or if there is the possibility for bacterial translocation across the compromised gastrointestinal tract.

Infectious causes

Viral enteritis

Rotavirus is the most common viral cause of neonatal diarrhea and may occur as outbreaks on farms in foals between 5 and 35 days old. Rotavirus is highly contagious and the incubation period as short as only 2 days. Older foals can be infected, although diarrhea tends to be milder, they can serve as reservoirs for neonates and should be isolated when identified. Transmission occurs by direct foal-to-foal contact and indirectly through personnel, fomites or environmental contamination. The virus affects the small intestine, causing blunting of the microvillus. Maldigestion (lactose intolerance) and malabsorption result. With villous atrophy and compensatory crypt cell proliferation, there is a net decrease in fluid absorption and an increase in secretion. With maldigestion, lactose may enter the colon, with subsequent fermentation and osmotic diarrhea. Clinical signs of rotaviral diarrhea are similar to those of other infectious diarrheas, and range from sub-clinical to mild diarrhea to severe, watery diarrhea with dehydration.

Rotaviral infections are diagnosed through the demonstration of virus particles in feces using commercial immunoassays or electron microscopy. Affected foals should be strictly isolated as morbidity can approach 100% in an outbreak. Disinfection with substituted phenolic compounds or quaternary ammonium should be performed. The virus can persist for several months in the environment.

Treatment of rotaviral diarrhea is largely supportive, and with good care mortality rates are low. Vaccination of mares during gestation is controversial, with mixed results reported.

Coronavirus is another rarely reported cause of viral enteritis in foals. An antemortem diagnosis of coronaviral enteritis can be made using fecal-capture ELISA, electron microscopy, and serology using bovine assays. The highest viral load appears to be shed in the feces during the acute stages, highlighting the importance of an early diagnosis and isolation. Immunohistochemistry can be used at postmortem examination.

Posted by : vetweb April 19, 2022 Tags : diseases

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