Deer viral hemorrhagic disease outbreak in San Gabriel Mountains, Los Angeles County

An outbreak of bluetongue (BTV) and epizootic hemorrhagic disease viruses (EHDV) occurred in free-ranging deer in the foothills of the San Gabriel Mountains in Los Angeles County this year. The outbreak started mid to late August and continued through October. Reports from concerned citizens in the Pasadena and Altadena areas adjacent to deer habitat, including the Jet Propulsion Laboratory grounds, suggested that multiple deer were affected (> 20), deer were often found dead near streams or other water sources, there were few or no sick deer observed, and no other species were affected. The history was consistent with an outbreak of one of a group of hemorrhagic disease viruses that can affect deer. In collaboration with CDFW South Coast Region biologists and the Pasadena Humane Society, three deer associated with this mortality event were necropsied and samples were submitted to the California Animal Food and Health Safety (CAHFS) laboratory in San Bernardino. Testing at CAHFS confirmed that EHDV was the cause of death for two of the deer tested and BTV the cause of death for the third.

The Department’s Wildlife Investigations Lab (WIL) is interested in outbreaks of viral hemorrhagic diseases in California’s free-ranging deer populations. These viruses include deer adenovirus and two closely related Orbiviruses, BTV and EHDV. None of these viruses are known to affect people. Deer adenovirus was first described following a 1993 outbreak in California involving multiple counties with mortality estimates of over a thousand deer. Since first being described in California deer, deer adenovirus has subsequently been detected in association with deer mortalities in most of the Western states and may be the most important hemorrhagic disease virus affecting California’s deer. Bluetongue virus has long been recognized as a disease of both domestic ungulates like cattle, sheep, and goats, and of free-ranging ungulates like deer. Epizootic hemorrhagic disease virus is one of the most significant infectious diseases of white-tailed deer with outbreaks occurring regularly in white-tailed deer from the Northern Great Plains down to Florida, and has been associated with disease in cattle. Historically, mule deer and black-tailed deer, the deer native to California, were considered less susceptible to the Orbiviruses than white-tailed deer; however, we do see localized outbreaks of BTV and EHDV in native deer throughout California.

The Wildlife Investigations Lab would like to thank the efforts of the local citizens that reported this outbreak and the Department staff, the Pasadena Humane Society, and the California Animal Health and Food Safety labs for their efforts in determining the causes of this outbreak.

Authored by: Dr. Brandon Munk

 

Advertisements

Bighorn Herds Studied for Health and Management

An understanding of the demography, distribution, behavior, and genetic diversity of animal populations enables the California Department of Fish & Wildlife to properly manage species statewide. Capturing bighorn sheep provides an opportunity to place GPS and VHF collars, as well as collect biological samples (e.g. blood, nasal swabs, hair, feces). This accumulation of data will offer insight into bighorn sheep population dynamics, genetic diversity, and overall health.

From October through November of this year, CDFW participated in helicopter captures of multiple bighorn sheep populations. After ensnaring the sheep in a net, a capture crew member would exit the helicopter, secure the sheep by placing leg hobbles and an eye cover, and then either process the sheep in the field or place it in a carry bag for long-line transport to a base camp for processing. Processing at the base camp consisted of weighing the sheep, collecting morphometrics (body measurements), blood, hair, feces, and nasal swabs (for detection of Mycoplasma ovipneumoniae, a bacteria that can cause a fatal pneumonia), administering vitamin E and selenium injections, followed by GPS and/or VHF collar placement and ear tagging. Additionally, an ultrasound examination was performed to both determine body condition score by measuring the thickness of subcutaneous fat and particular muscle bodies, as well as check if any ewes were pregnant. Following processing, sheep were either released from the base camp or returned by helicopter to the capture site for release.

Up first on the schedule were the endangered Sierra Nevada bighorn sheep. Over the course of six days in the Sierra Nevada Mountains, a total of 34 sheep were captured, including seven rams, with 33 sheep receiving at least one VHF or GPS collar (33 VHF, 31 GPS). Operations then moved to the Sespe Wilderness Area within Los Padres National Forest to capture desert bighorn sheep that had originally been translocated to the area, part of their historic range, back in the mid-1980s. This was quite the unique opportunity in that these sheep were thought to be all but gone from the range in the early 2000s and were only recently seen on the landscape. Furthermore, the population hadn’t been handled in the more than 30 years since their initial reintroduction. A total of 22 sheep were captured over three days, including 10 rams, with 19 sheep receiving at least one VHF or GPS collar (15 VHF, 13 GPS). The Sespe captures were followed by four days in Anza Borrego State Park and Palm Desert, CA for field processing of desert bighorn sheep from the Peninsular Ranges. These efforts yielded 42 total captures, all ewes, with each sheep receiving at least one VHF or GPS collar (18 VHF, 26 GPS). The capture team then moved to the Mojave Desert and Death Valley National Park for seven days of desert bighorn sheep processing, yielding 71 total captures, including 18 rams, with all but two sheep receiving both a VHF and GPS collar (69 VHF, 69 GPS). Capture operations wrapped up in the White Mountains just outside of Bishop, CA, where 33 desert bighorn sheep were captured over four days, including 12 rams, with all but two sheep receiving both a VHF and GPS collar (31 VHF, 31 GPS).

In less than one month, CDFW captured 202 bighorn sheep, placed 166 VHF and 170 GPS collars, and collected abundant biological samples that will be closely studied for the next few years. The information acquired through analysis of the biological samples, as well as the continual spatial data that the collars will generate, will provide CDFW with valuable material by which they can make educated and well-informed decisions regarding the management of the state’s bighorn sheep populations.

BHS Capturejpg_Page1.jpg

IMG_1109

IMG_1352