The Cervidae Health Research Initiative Creates a Deer Farm Diagnostic Network

By: Allison Cauvin, Shannon P. Moore, Katherine Sayler, Samantha M. Wisely 
Dept. of Wildlife Ecology and Conservation, Institute of Food and Agricultural Sciences, University of Florida
Originally appeared in the Spring 2017 Issue of the Southeast TDA Newsletter

Cervid farming has been named one of the fastest-growing industries in rural America. Due to its explosive growth, the need to understand the diseases that affect deer health and how these are impacted by management decisions has become more crucial. The Cervidae Health Research Initiative (CHeRI) is an interdisciplinary effort funded by the Florida legislature to promote the health and sustainable production of farmed cervids, while also focusing on the health of native wildlife and the ecosystems in which they live. CHeRl involves 14 University of Florida faculty from all disciplines of life sciences who work collaboratively to help tackle the most pressing disease problems in the deer farm industry. Our stakeholders represent more than 300 deer farms located throughout the state of Florida. 

The primary focus of CHeRl revolves around keeping deer healthy. In Florida, one of the most significant diseases of deer is hemorrhagic disease. Our initiative uses a four pronged approach to tackling this persistent threat to the industry: 1) we are building a network of deer farm cooperators to help with proactive disease surveillance in Florida, 2) using the information gleaned from our surveillance network, we are working with producers to develop management plans for preventing cervid diseases, 3) as new vaccines for hemorrhagic disease are developed, we are partnering with other research groups to bring vaccines to trial phase, and 4) we are developing integrated pest management plans specific to Florida in order to control the midges that spread disease. CHeRl's ultimate goal is to reduce the impact that hemorrhagic disease has on the Florida deer farm industry. Central to this effort is the Deer Farm Diagnostic Network. 

Creating a Florida Deer Farm Diagnostic Network 

We provide free diagnostic services for deer that appear to have died from an infectious disease so that both deer farmers and scientists can understand the leading causes of death in Florida farmed deer. Providing deer farmers with information about the cause of death for their deer allows them to better identify symptoms of illness, manage their herd for disease outbreaks, and make informed management decisions. As more deer farmers across Florida submit deer samples for testing, it will allow CHeRl scientists to determine epidemiological patterns for hemorrhagic disease emergence and to identify newly emerging disease threats. Information collected from dead deer is critical for the study of Florida hemorrhagic disease viral strains, vaccine development, and provides Florida deer farmers with an early alert system for hemorrhagic disease outbreaks. Ultimately, we hope this service will reduce the incidence of disease in farmed cervid populations across the state. 

How Does the Deer Farm Diagnostic Network Operate? 

CHeRI needs a suite of tissues collected from dead animals in order to determine cause of death. Tissues can be collected in three ways: 1) deer farmers can harvest tissues themselves and send them to the UF Molecular Ecology Lab where CHeRl is housed; 2) a CHeRI necropsy technician can travel out to the farm and collect tissues or; 3) CHeRl will reimburse veterinarians who collect and send tissues. CHeRI has a monitored hotline for deer farmers to call when one of their animals dies. Full directions on how to collect tissues and where to send them (including a necropsy tutorial video) are on the CHeRI website. Once collected, tissues are processed to determine a cause of death. CHeRI conducts a variety of tests to provide a comprehensive pathology profile of the animal. Molecular assays and basic microbiology are run on the blood and tissues (lung, liver, heart, kidney, and spleen) of animals to look for common cervid viruses and bacteria. Tissues may also be stained and examined microscopically or submitted for further viral testing if additional pathogens are suspected. All of this information is combined to generate a diagnostic report that is returned to deer farmers, and these results are completely confidential. In order to protect the interests of our stakeholders, no testing of reportable diseases is performed and no farm names are utilized in any research reports or publications. If interested in our free necropsy and screening service, please contact 352-562-DEER.

The CHeRI Deer Farm Diagnostic Network Has Already Provide Valuable Insight Into Causes of Disease

The information gained from the diagnostic network has already shed light into the disease dynamics of Florida cervids. In 2016, we conducted 92 necropsies on Flonda farmed cervids, yielding valuable information on the timing and cause of disease. We determined that there was a seasonal shift in the causes of illness in Florida cervids. During the summer months, from roughly June-October, the primary cause of death for necropsied deer was enteritis and sepsis caused by bacterial infection. In fawns, the key pathogens during this time included E. coli and Trueperella, while adults were more likely to die of E. coli or Clostridium infections. This is unsurprising, as the hot, wet conditions of summer make the soil a perfect breeding ground for these types of bacteria. Sick deer typically contaminate the soil of their pen with their feces, and others become infected by eating contaminated feed or dirt. Depending on the type of bacterial infection, affected deer might act lethargic or tired, isolate themselves, develop a fever or lesions, or present with severe diarrhea. 

During the late summer-fall season, there was a shift to viral infections of hemorrhagic disease as the primary cause of death in necropsied deer. Hemorrhagic disease is caused by two separate but closely related viruses: epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV). Common symptoms of EHDV and BTV infection include fever, anorexia, swelling of the soft tissue around the head and neck, dental pad erosion, and a swollen, lolling tongue. These viruses are both transmitted by Culicoides biting midges, though the exact species acting within Florida is unknown. UF entomologists are working as a part of CHeRl to identify which species is acting as a vector and to determine the ecology of these midges. 

There are five serotypes of BTV found in Florida, and all have been shown to infect deer. There have also been reports of the introduced BTV-8 causing disease in farmed and wild Florida cervid populations.  There are three  serotypes of EHDV in the United States: EHDV-1, 2, and 6. All three of these serotypes have been found to cause illness in Florida cervids. Through CHeRI’s long-term hemorrhagic disease monitoring, we actually documented a shift in incidence of EHDV serotypes between the 2015 and 2016 seasons. In 2015, there were relatively few deaths attributed to EHDV, and EHDV-1 was the most prevalent serotype. In 2016, EHDV-2 incidence was much higher, and more deaths were attributed to hemorrhagic disease. Looking at which viral serotypes are circulating from year to year helps us design vaccine schedules and will eventually determine which vaccines farmers should be using to maximize protection for their herds. 

While the bulk of hemorrhagic disease cases typically occurred in the late summer season, Florida's subtropical climate allows the disease to be transmitted well into the winter months. In winter 2016-2017 we saw animals die of hemorrhagic disease through December and circulating virus in January 2017. CHeRl scientists are working to understand how these viruses are being sustained during the winter season. Discovering which factors are important to how this disease overwinters is crucial to developing targeted disease mitigation efforts specific to Florida deer farmers. 

The CHeRl Deer Farm Diagnostic Network has already provided several unanticipated success stories. The proactive disease surveillance of CHeRl's diagnostic network identified the first case of deer poxvirus in Florida. Four fawns with facial lesions rapidly died, yet were negative for Trueperella, all other suspect bacteria, and hemorrhagic disease. A comprehensive diagnostic analysis by UF identified the virus and allowed the farmer to make management decisions to prevent the spread of this highly contagious disease. In another win for the network, CHeRI was able to rapidly alert deer farmers in south Florida of the screwworm outbreak that occurred in deer in the Florida Keys in fall 2016. Screwworm is a devastating infestation that can rapidly take over a deer herd causing massive economic losses to deer and livestock. 

Ultimately, the information generated by CHeRl can be used by deer farmers to improve the health of their herds. Cervid diseases not only cause animal loss but can lead to decreases in animal production. We are developing a multi-pronged approach that includes an integrated pest management plan and a best farm management plan that can be utilized by deer farmers to maximize their deer health and production while minimizing their incidence of disease and mortality. The CHeRI Deer Farm Diagnostic Network will play a key role in the success of these endeavors.