Diarrhea with Dehydration and Acidosis in a Calf

History. You are asked to examine a 2-day-old calf. The owner reports that the calf appeared normal the night before, but this morning she is recumbent and will not rise. In addition, she shows no interest in suckling a bottle.

Clinical and Laboratory Examination. The calf’s body temperature is subnormal. The mouth is dry, and the eyes are sunken into the orbits. The ears, tail, and distal legs are cool to the touch. The tail and perineum of the calf are wet. As you remove your thermometer, the calf passes a stream of liquid feces. The feces are almost clear and slightly yellow, with the consistency of water. Simple laboratory tests indicate that the packed cell volume is 50% (normal, 30%-35%) and the serum total-solids concentration 7.5% (normal, 5.5%- 6.5%).

Comment. The calf has diarrhea, and the physical exam­ination and laboratory findings indicate a state of advanced dehydration. Loss of body fluid volume is so severe that the calf appears to be in or near a state of hypovolemic shock. Although you cannot be certain from your examination of the calf at the farm, the severity of dehydration, the rapidity of onset, and the age of the calf all suggest a hypersecretory diarrhea caused by enterotoxigenic E. coli bacteria. Animals with such clinical signs are usually severely acidotic, although blood pH is seldom measured in field cases. Diarrhea, acidosis, and dehydration occur because toxins produced by the bacteria stimulate opening of chloride gates in the apical membranes of crypt cells, stimulating copious secretion of water and electro­lytes, including bicarbonate. The sodium co-transport system on the villi is unaffected by the bacterial toxin, but the simul­taneous presence of glucose and sodium in the lumen is neces­sary to promote co-transport, which can offset some of the fluid and electrolyte losses caused by hypersecretion from the intestinal crypts.

Treatment. Vascular volume expansion and correction of acidosis are primary concerns in such cases. This calf should receive 2 L of alkalizing fluids by rapid intravenous (IV) admin­istration, with an additional 2 L or more over the next 24 hours. Frequently, the response of calves to such treatment is remark­able, and calves that appear almost dead can often be saved by vigorous fluid therapy. After the initial replacement of lost fluids by IV therapy, further dehydration caused by ongoing fluid losses can be prevented by oral administration of fluids containing glucose and sodium.