Mohave County's bighorn sheep ravaged by disease

The ewe was seen standing with her head down and coughing. She appeared lethargic. It was obvious that she wasn't well. It would be just a matter of time before she was dead.

This is what sportsmen and personnel from the Arizona Game and Fish Department have observed in the Black Mountains, which is home to state's largest sheep herds.

Erin Butler is the Region 3 Game Specialist and is worried about the sheep herds along the Colorado River in Units 15C North, 15C South, 15D North and 15D South.

"We have a serious issue out there," Butler said. The issue appears to be that many of the sheep in those units are infected with an upper respiratory disease, pneumonia. And that disease can be and usually is fatal to the infected sheep. Those sheep that do survive the disease may be left with chronic sinusitis.

Butler said that the department was first aware of sick sheep in August. A single ewe was seen north of Willow Beach that was sick. That sheep was removed and tested positive for pneumonia.

The department received reports of sick sheep along Highway 93 which divides Game Management Units 15B West and 15C North.

When the department conducted its annual sheep surveys in October, no sick sheep were found, but there were dead sheep in Unit 15C North, and the survey showed a huge decrease in the numbers of sheep seen in 15C North and 15C South. A decline of about 10 percent of the sheep population in Unit 15B West was also noted.

In November the department held a sheep capture and transplant of 40 sheep from Unit 15D North to Knab Creek in Unit 12A West.

The sheep were tested at that time, but none seemed to be ill.

But when the test results came back from the laboratory later it showed that those sheep were in fact infected.

Since that time, there have been sick sheep reported in the area where the transplanted sheep were taken.

Butler said that in December sheep hunters contacted the department and reported that sick sheep had been seen in Unit 15D North. Sick sheep were also seen at Boundary Cone in Unit 15D South.

This disease is believed to have reached the Arizona sheep herd by being in contact with sheep from Nevada, which had also had an outbreak of pneumonia. Testing revealed that sheep in California also had the same strain of pneumonia, biologists learned.

How did they get into Arizona? Sheep have been crossing the Pat Tillman Bridge over the Colorado River above Willow Beach and are able to swim across the river as well.

The disease is passed on from nose to nose, and so when an infected sheep is around other sheep and starts coughing, the disease is spread to those in the immediate area.

What about treatment?

"There is currently is no vaccine or other treatment that has been proven effective in either wild sheep or domestic sheep for this type of pneumonia," Butler said.

Symptoms of the disease range from coughing, nasal discharge and exercise intolerance, and those infected tend to lag behind the group and not keep up. Other symptoms include loss of appetite and reduced activity levels.

This disease is devastating to wild sheep. Mortality of between 75-90 percent has been known in the past to sheep herds that have been infected.

With the commission meeting in April to set sheep permit numbers, Region 3 is going to conduct another sheep survey this month to determine the extent of the disease outbreak to the herds along the Colorado River.

Butler said that after the survey the region will put together sheep permit number recommendations for this year to the commission.

"At this time I cannot speculate on what permit numbers may be," Butler said.

Since the disease affects both rams and ewes, a good guess would be that permit numbers will be down for sure, and maybe in some units, no permits at all.

Butler said that this is not the first time that there has been an outbreak of disease in the Black Mountains that has affected sheep population.

In 2002, the disease impacted the sheep population in units 15B West, 15C North and 15D that lasted for approximately 8-10 years. In Unit 15C South, the population still had not fully recovered.

Butler says that based on experience, the latest outbreak will last one to two years and can affect sheep numbers in the Black Mountains for the next seven to 10 years.

Obviously the department will no longer be transplanting sheep out of Unit 15D North, which had been at record numbers for the past few years.

Butler said that they will reevaluate the program once the sheep population recovers, however long that may take, and that sheep may still be collared and monitored during this time.

One thing is for sure. This outbreak will cause a decline in sheep numbers in the Black Mountains and with burro populations being at over three times the authorized level there, the daily competition for food, water and space will continue to be intense.