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

If heartwater entered the United States, what would likely occur?

1. Asymptomatic infections in most cattle

2. High mortality in all susceptible ruminants

3. Chronic illness in sheep and goats

4. Equally likely scenarios for cattle and goats

The correct answer is: High mortality in all susceptible ruminants

The scenario presented in the question refers to heartwater, a rickettsial disease caused by the bacterium Ehrlichia ruminantium, primarily transmitted by certain species of ticks. This disease specifically affects ruminants, including cattle, sheep, and goats. If heartwater were to enter the United States, high mortality in susceptible ruminants would be expected. This is largely due to the acute nature of the disease, which can cause severe clinical signs and lead to death, especially in naive populations that have not been previously exposed to the pathogen. The high mortality rate is particularly pronounced in cattle, but it can also affect other ruminants depending on their exposure and immunity. While some species may exhibit mild or asymptomatic cases, the risk of high mortality remains a significant concern, especially considering the potential impact on livestock populations and economic repercussions in the agricultural sector. The potential existence of chronic illness in some animals is less common and does not align with the acute presentation typically seen with heartwater, making the prospect of widespread high mortality a more accurate and serious consequence of the disease entering new populations. Overall, the high mortality risk highlights the severe threat that heartwater poses if introduced into environments where native ruminants lack immunity, thus