Breaking Down the Hemorrhagic Disease Outbreak
The 2012 deer season might already be a distant memory; however, your next deer season may benefit from observations made during 2012–13. In 2012, more than 10,000 suspected hemorrhagic disease (HD) cases were reported, from all 114 counties, to Conservation Department sta ff, but the actual number of cases is unknown, and the severity will vary locally. To understand how and why this is the case, you must know a little more about the disease.
Understanding the Disease
Hemorrhagic diseases include both the bluetongue and epizootic hemorrhagic disease (EHD) viruses. Although the majority of confirmed-infected deer had the EHD virus, the bluetongue virus was also detected in Missouri. These viruses have indistinguishable symptoms, so we group them together for simplicity and refer to them as hemorrhagic diseases, or HD. Symptoms can appear similar to other diseases that affect deer, including chronic wasting disease (CWD). Therefore, it is important to notify the Conservation Department when sick or unexplained dead deer are found.
Hemorrhagic diseases are expressed in three different forms, with each causing a variety of symptoms. The three forms of HD are peracute, acute, and chronic (not related to chronic wasting disease) and dictate the length that a deer can survive. The peracute form progresses rapidly and causes death within a week after infection, which is the quickest of the HD forms. This form can cause swelling, or edema, when fluid accumulates in the head, tongue, neck, and lungs. Therefore, deer that die due to the peracute form often appeared healthy with very few clinical signs.
The acute form causes death within one to two weeks and symptoms include swelling and bleeding, or hemorrhages, throughout the body, including heart, rumen (portion of the stomach), and intestines. Sores, or ulcers, can also form on the deer’s tongue, dental pad (front portion of the roof of the mouth) and portions of the stomach. Both peracute and acute forms can cause deer to become lethargic, lose fear of humans, and develop a high fever. It is this fever that causes deer to seek relief in the form of water, but as the infection progresses they become disoriented and lose coordination, often dying in or in close proximity to these water sources. Research suggests that approximately 85 percent of the deer in Missouri that contract HD will have either the peracute or acute form.
Although the chronic form of HD is less common in Missouri,