An outbreak of heartwater has been identified on a farm. Which of the following animals does not have clinical signs consistent with this disease?

• A. A lamb with fever
• B. A heifer that died suddenly a week ago, with no other clinical signs
• C. A cow that is circling, depressed, and in respiratory distress
• D. None of the above

Answer: (D)

Heartwater can produce a range of clinical signs in cattle, sheep, and goats, reflecting its effects on the vascular system and nervous system. Animals may show fever and depression, respiratory distress from pulmonary edema, and nervous signs such as circling or ataxia. Death can occur rapidly, sometimes with little warning signs beforehand or with only minimal signs before collapse.

Given that each described animal can display signs consistent with heartwater—fever in a lamb, sudden death in a heifer, and circling with respiratory distress in a cow—there isn’t an animal here that lacks signs. Therefore, none of the above is the best choice, because all scenarios can be associated with heartwater manifestations.