Targeted culling of deer controls disease with little effect on hunting

October 21, 2013

CHAMPAIGN, Ill. -- Chronic wasting disease, the deer-equivalent of mad cow disease, has crept across the U.S. landscape from west to east. It appeared first in captive mule deer in Colorado in the late 1960s. By 1981, it had escaped to the wild. It reached the Midwest by 2002. Little is known about its potential to infect humans.

Now researchers at the University of Illinois offer a first look at the long-term effectiveness of the practice of culling deer in areas affected by CWD to keep the disease in check. Their study appears in the journal Preventive Veterinary Medicine.

Each year, the Illinois Department of Natural Resources tests 7,000 (hunted, culled or incidentally killed) deer for CWD infection, conducts aerial surveillance to see where deer congregate and sends in sharpshooters to cull deer at the sites with disease, said Jan Novakofski, a professor of animal sciences at the University of Illinois and an author of the study.

"We know a lot about how far deer typically move," he said. "If they're sick, they're going to spread the disease that far. So if you find a deer that's sick, you draw that small circle and you shoot there."

He called this approach "a textbook scientific strategy for control. You reduce contact and you reduce the spread of infection with the smallest overall impact on healthy deer."

Novakofski and his colleagues at the Illinois Natural History Survey (part of the Prairie Research Institute at the U. of I.) found that the strategy worked: The prevalence of CWD in tested Illinois deer remained at about 1 percent from 2002 to 2012.

The team also found that hunters were killing more deer each year in each region of the state (north, central and south) regardless of CWD and CWD management. Statewide, the number of deer killed by hunters went from 147,830 in 2001, before the appearance of CWD, to 181,451 in 2012. The only exception: Two counties out of 10 with cases of CWD saw a reduction in hunter harvest over the same period.

"We wanted to know whether Illinois hunters have fewer deer to hunt now than they did before CWD," said Nohra Mateus-Pinilla, a wildlife veterinary epidemiologist at the INHS who led the study with postdoctoral researcher Mary Beth Manjerovic. "We found that hunter harvest has increased, and the prevalence of CWD has been maintained at low levels for 10 years in Illinois."

This finding answers a long-time complaint by some hunters that the culling of deer makes it harder for them to find deer to shoot, Novakofski said.

"Since 2001, hunter harvest of deer has increased similarly in the northern region of Illinois, where CWD occurs, and the rest of the state, where there is no disease or sharpshooting," he said.

In the two Illinois counties with fewer deer, "the reductions were 11 to 20 percent," Manjerovic said.

The team compared the Illinois experience with that of Wisconsin, which changed its CWD-management strategy from one that relied on culling to one that consisted primarily of allowing hunters to thin deer herds, the researchers said. Wisconsin saw a striking increase of infection in CWD-tested deer after it did that, the team found.

"In the early years in Wisconsin, (CWD prevalence) was still about 1 percent, just as it was in Illinois," Manjerovic said. "Then the strategy changed. Since 2007, CWD prevalence has increased to about 5 percent."

"We can't find an environmental or other variable that explains the increase in prevalence except a change in management," Novakofski said.

The numbers may not seem alarming to some, said postdoctoral researcher and co-author Michelle Green. But the trend is of concern, she said.

"CWD is a prion disease (like mad cow disease) and it's 100 percent fatal. There's no current way that we can actually make the deer better, so it's important that we keep it from spreading too far throughout the population," she said. "And then there's also the connection to mad cow disease. We don't have enough information yet to really understand what the impact to human health could be."

"We all hope that there is never a case of chronic wasting disease in humans. We all hope that it never spreads to people or agricultural animals," Novakofski said. "If it ever does, the investment in maintaining prevalence at a low level in Illinois will be repaid a thousand-fold."
-end-
Editor's notes: To reach Nohra Mateus-Pinilla, call 217-333-6856; email nohram@illinois.edu.

To reach Jan Novakofski, call 217-333-6181; email jnova@illinois.edu.

The paper, "The Importance of Localized Culling in Stabilizing Chronic Wasting Disease Prevalence in White-Tailed Deer Populations," is available online or from the U. of I. News Bureau.

University of Illinois at Urbana-Champaign

Related Infection Articles from Brightsurf:

Halving the risk of infection following surgery
New analysis by the University of Leeds and the University of Bern of more than 14,000 operations has found that using alcoholic chlorhexidine gluconate (CHG) halves the risk of infection in certain types of surgery when compared to the more commonly used povidone-iodine (PVI).

How plants shut the door on infection
A new study by an international team including University of Maryland scientists has discovered the key calcium channel responsible for closing plant pores as an immune response to pathogen exposure.

Sensing infection, suppressing regeneration
UIC researchers describe an enzyme that blocks the ability of blood vessel cells to self-heal.

Boost to lung immunity following infection
The strength of the immune system in response to respiratory infections is constantly changing, depending on the history of previous, unrelated infections, according to new research from the Crick.

Is infection after surgery associated with increased long-term risk of infection, death?
Whether experiencing an infection within the first 30 days after surgery is associated with an increased risk of another infection and death within one year was the focus of this observational study that included about 660,000 veterans who underwent major surgery.

Revealed: How E. coli knows how to cause the worst possible infection
The discovery could one day let doctors prevent the infection by allowing E. coli to pass harmlessly through the body.

UK study shows most patients with suspected urinary tract infection and treated with antibiotics actually lack evidence of this infection
New research presented at this week's European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Amsterdam, Netherlands (April 13-16, 2019) shows that only one third of patients that enter the emergency department with suspected urinary tract infection (UTI) actually have evidence of this infection, yet almost all are treated with antibiotics, unnecessarily driving the emergence of antimicrobial resistance.

Bacteria in urine doesn't always indicate infection
Doctors should think carefully before testing patients for a urinary tract infection (UTI) to avoid over-diagnosis and unnecessary antibiotic treatment, according to updated asymptomatic bacteriuria (ASB) guidelines released by the Infectious Diseases Society of America (IDSA) and published in Clinical Infectious Diseases.

Subsidies for infection control to healthcare institutions help reduce infection levels
Researchers compared three types of infection control subsidies and found that under a limited budget, a dollar-for-dollar matching subsidy, in which policymakers match hospital spending for infection control measures, was the most effective at reducing the number of hospital-acquired infections.

Dengue virus infection may cause severe outcomes following Zika virus infection during pregnancy
This study is the first to report a possible mechanism for the enhancement of Zika virus progression during pregnancy in an animal model.

Read More: Infection News and Infection Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.