Hemorrhagic enteritis (HE), an economically important disease of turkeys is caused by an adenovirus. The virus is ubiquitous and is liable to infect most field turkeys. In unprotected turkey flocks, infection with virulent hemorrhagic enteritis virus (HEV) may result in variable mortality and immunodepression. Turkeys younger than 2-4 weeks of age are resistant to clinical HE. This age-related resistance is expressed in the presence or absence of maternal antibodies against HEV. Clinical disease is characterized by HE and splenomegaly. The virus causes intranuclear inclusions in the reticuloendothelial cells. Bursectomy or splenectomy abrogate clinical HE. Field data and laboratory studies indicate that HEV causes immunodepression in the humoral as well as the cellular immune functions of turkeys. The mechanism of immunodepression is not known (Sharma, 1991).
4. Microbial Pathogenesis
Experimental or natural exposure to HEV in turkeys often leads to HE and splenomegaly. The intestinal lesion, appearing within 5-6 days of oral exposure to virulent HEV, is often characterized by grossly visible accumulation of blood in the duodenum and jejunum. Along with the intestinal lesion, the spleen may become grossly enlarged and mottled. Histologically, severe intestinal hemorrhages may be associated with necrosis of the tips of villi and a varying degree of lymphoid cell hyperplasia in the lamina propria. The spleen lesion is characterized by lymphoid cell necrosis, reticular cell hyperplasia and the appearance of intranuclear inclusion bodies. Histopathological changes may also be present in a number of other organs including liver, lungs, pancreas, bursa of Fabricius and thymus (Sharma, 1991).
5. Host Ranges and Animal Models
Turkeys are afflicted by hemorrhagic enteritis, and chickens have been found to have antibodies to the virus (Sharma, 1991).
II. Vaccine Information
1. Hemorrhagic Enteritis Live Virus Vaccine (USDA: 17E1.20)
a. Manufacturer:
Intervet Inc., Arko Laboratories Ltd., Brinton Laboratories Inc., Biomune Company
