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Anaplasmosis and Epizootic Hemorrhagic Disease

Two diseases that are commonly encountered in the late summer and early fall at the ADDL are Anaplasmosis in cattle and Epizootic Hemorrhagic Disease (EHD) in deer.

Anaplasmosis is caused by a rickettsial organism (Anaplasma marginale) that is spread by ticks and biting insects. Additionally, it can be transmitted by needles or surgical equipment. Cattle are not the only animals that can be infected with the parasite; sheep, goats, buffalo, and some wild ruminants are also susceptible to erythrocytic Anaplasma. Once the parasite reaches the blood stream it infects red blood cells (RBCs) where they multiply. Anemia results from an erythrophagocytosis of the RBCs. Anemic animals will develop icterus but not hemoglobinuria because RBC destruction occurs from erythrophagocytosis rather than hemolysis.

In cattle, animals less than one year of age are usually subclinical while 1-2 year old animals have moderate to severe clinical signs, and older animals have severe signs and high mortality rates. Loss of condition, anorexia, dyspnea, anemia, icterus, and sudden death are the most commonly reported clinical signs with drop of milk production in nursing cattle and abortions in pregnant animals. On necropsy affected cattle may have severe anemia with pale white to yellow mucus membranes, diffuse icterus, enlarged and congested spleens (2-3x normal) and dry, firm feces.

Anaplasmosis testing can be done at the ADDL with Whole Blood or Fresh Spleen by PCR testing and/or Serum by ELISA testing.  

This year, the Ohio Department of Natural Resources (ODNR) Division of Wildlife has submitted several deer to the ADDL that have been positive for Epizootic Hemorrhagic Disease (EHD). As of October 1, 2020, affected counties that have detected positive cases of EHD include Butler, Champaign, Clinton, Hancock, and Montgomery. Counties along the Ohio River tend to have the most cases of the disease, but it can be found throughout the state. Captive deer owners have also reported the infection in several herds.

EHD is a viral infection (genus Orbivirus, family Reoviridae) that is primarily transmitted by biting midges (genus Culicoides) to several species of cervids, especially white tailed deer.  Sporadic clinical cases and outbreaks have also been reported in other cervids (mule deer and elk), cattle, bison, yaks, bighorn sheep, and pronghorn antelope, although most infections in these species seem to be subclinical. Deer infected with EHD can show little or no clinical signs (peracute illness) and are found dead, while in other infected animals the disease may linger for weeks and the deer may have fevers, anorexia, lethargy, weakness, lameness, and respiratory distress. The head and neck may swell and there may be ulcerations/erosions of the oral cavity with excessive salivation and nasal discharge. Diarrhea and severe dehydration and weight loss may occur if the animal survives the acute phase of the disease. The deer may show no fear of humans and often can be found near or in bodies of water due to fever and dehydration.  

Necropsy findings have varying degrees of edema and hemorrhages throughout the tissues of the affected animal. Petechiae and ecchymosis can be seen in gastrointestinal tract, cardiovascular system, and respiratory system along with lymph nodes, urinary bladder, pleural and peritoneal cavities. Erosions and ulcerations can be seen in the oral cavity, esophagus, rumen, abomasum and small intestines.             

Fresh Spleen, Lymph Nodes, and/or Lungs are the tissues of choice for PCR testing of EHD at the ADDL.

According to the Ohio Department of Natural Resources (ODNR) Division of Wildlife: “People should always avoid touching or handling sick or dead wild animals. Sightings of sick or dead deer should be reported at wildohio.gov/reportwildlife, your local Ohio wildlife officer, or wildlife district office”.

To submit samples for anaplasma (ELISA or PCR) or EHD (PCR) testing to the ADDL, use our Submission Form and follow our Shipping Guidelines.

Craig Sarver, DVM, MS, ADDL Pathologist