Hemorrhagic disease (HD) is a viral disease that affects many species of wildlife. The disease is caused by two viruses: Epizootic Hemorrhagic Disease Virus (EHD) and Bluetongue Virus (BT). HD is an important disease that can have significant impacts on wildlife populations, and understanding the causes, transmission, and clinical signs of the disease is crucial for effective management.
Cause:
EHD and BT are both members of the genus Orbivirus, which is part of the family Reoviridae. Both viruses are transmitted by biting midges, which are small insects that feed on the blood of animals. Once infected, the virus replicates in the endothelial cells lining the blood vessels, causing damage to the vessels and leading to hemorrhage and edema. The virus can also infect white blood cells, leading to immune system dysfunction.
Significance:
HD is a significant disease that can have severe impacts on wildlife populations. The disease can cause high rates of mortality, especially in populations that are naive to the virus. In some cases, mortality rates can reach 50-90% of affected populations. In addition to the direct impacts on wildlife, HD can also have economic impacts on hunting and recreational industries.
Species Affected:
HD can affect many species of wildlife, including deer, elk, moose, bighorn sheep, pronghorn, and cattle. The disease is most commonly seen in white-tailed deer and mule deer in North America. However, other wildlife species, such as bison and coyotes, can also be affected.
Distribution:
HD is found throughout North America, including Canada, the United States, and Mexico. The disease is most common in the southeastern and midwestern United States but has been reported in other regions as well.
Transmission:
HD is transmitted by biting midges, which are small insects that feed on the blood of animals. The virus is not transmitted from animal to animal, and infected animals cannot transmit the virus to humans or other animals.
Clinical Signs:
The clinical signs of HD can vary depending on the species affected and the severity of the infection. In some cases, infected animals may show no clinical signs. However, in severe cases, animals may exhibit fever, lethargy, difficulty breathing, and swelling of the head and neck. Infected animals may also have ulcers on the tongue and gums, and bloody diarrhea. In some cases, infected animals may die suddenly without showing any clinical signs.
Diagnosis:
Diagnosing HD can be challenging, as the clinical signs can be similar to other diseases. A definitive diagnosis can be made through laboratory testing of blood or tissue samples. PCR (polymerase chain reaction) testing can detect the presence of the virus in blood or tissue samples, while serological testing can detect antibodies to the virus.
Treatment:
There is no specific treatment for HD. Supportive care, such as fluids and anti-inflammatory medications, may be provided to infected animals to help alleviate clinical signs. However, in severe cases, the disease may be fatal.
Management:
Management of HD involves controlling the spread of the disease and reducing the risk of transmission. Prevention measures include reducing the population density of wildlife, reducing the number of midges in the environment, and implementing surveillance programs to detect the presence of the virus. Vaccines are also available for some species, such as cattle and sheep. Additionally, hunters are advised to avoid consuming meat from animals that show clinical signs of the disease.
Conclusion:
HD is an important viral disease that affects many species of wildlife, with significant impacts on wildlife populations and the economy. The disease is caused by two viruses, EHD and BT, which are transmitted by biting midges. Infected animals can exhibit a range of clinical signs, including fever, lethargy, and swelling of the head and neck. Diagnosis can be challenging, but laboratory testing can confirm the presence of the virus. There is no specific treatment for HD, but supportive care can help alleviate clinical signs. Management of the disease involves controlling the spread of the virus and reducing the risk of transmission.
Prevention measures, such as reducing population density and implementing surveillance programs, can help reduce the spread of the disease. Vaccines are also available for some species, such as cattle and sheep. Public education is also important to raise awareness about the disease and reduce the risk of transmission.
In conclusion, understanding the causes, transmission, and clinical signs of HD is crucial for effective management of the disease in wildlife populations. While there is no specific treatment for HD, prevention measures and vaccines can help reduce the spread of the virus and protect wildlife populations. Ongoing research and surveillance are necessary to better understand the disease and develop new strategies for managing its impacts on wildlife and the economy.
You can read more about HD by reviewing the source material below or reading more posts for additional information on wildlife health, behavior, and management.
Sources:
- Hemorrhagic Disease in Deer: Understanding and Managing a Deadly Virus. Quality Deer Management Association. https://www.qdma.com/hemorrhagic-disease-in-deer-understanding-and-managing-a-deadly-virus/.
- Hemorrhagic Disease in Wildlife. United States Geological Survey. https://www.nwhc.usgs.gov/disease_information/other_diseases/hemorrhagic_disease.jsp.
- Bluetongue and Epizootic Hemorrhagic Disease. Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-wildlife-health-center/health-program/research-projects/bluetongue-and-epizootic-hemorrhagic-disease.