Transboundary Emerging and Exotic Animal Disease/ Exotic Animal Disease Practice Exam

Which animal is least likely to show clinical signs consistent with heartwater disease?

1. A lamb with a fever

2. A heifer that died suddenly with no signs

3. A cow showing respiratory distress

4. A steer with fever and mild coughing

The correct answer is: A heifer that died suddenly with no signs

Heartwater disease, caused by the bacterium Ehrlichia ruminantium and primarily transmitted by ticks, predominantly affects ruminants such as cattle, sheep, and goats. The clinical signs associated with heartwater often include fever, nervous signs, and respiratory issues, among others. The choice indicating a heifer that died suddenly with no signs aligns with the characteristic features of heartwater disease, particularly in that many infected animals may succumb to the disease rapidly without showing extensive clinical signs beforehand. While the disease can cause sudden death, it is not common for it to occur in the absence of any previous clinical signs. In contrast, the other options describe animals displaying symptoms such as fever and respiratory distress, which are known clinical manifestations of heartwater disease. Fever is particularly prevalent in affected animals, and signs of respiratory distress can also occur due to fluid accumulation in the lungs or other systemic effects of the disease. Thus, the heifer, having died suddenly and lacking any clinical symptoms beforehand, is the least representative of the typical disease progression seen in cases of heartwater. This makes it the answer to the question of which animal is least likely to show clinical signs consistent with heartwater disease.