If an influx of wild hogs, outbreaks of brucellosis in elk or the slow spread of chronic wasting disease in Montana’s deer, elk and moose wasn’t already enough to worry about, state wildlife officials are now prepping for a possible outbreak of bovine tuberculosis.
“Bovine tuberculosis (bTB) is a bacterial disease caused by Mycobacterium bovis (M. bovis),” according to Montana Fish, Wildlife & Parks’ literature on the topic.
Although there has been no detection of the infection in more than a decade in Montana, officials at FWP want to be proactive and have a plan in place should an outbreak occur, according to Jennifer Ramsey, FWP’s wildlife veterinarian.
“The point of the plan is to lay out how we want to look for it,” she said. “Then, if it is detected, we can hit the ground running.”
With that in mind, FWP is requesting public review and comment on its Proposed Montana Bovine Tuberculosis Surveillance Plan. More detailed information on the disease, as well as the ability to comment online, is available at http://fwp.mt.gov/hunting/publicComments/2019/bovineTBPlan.html.
Montana has dealt with bovine TB before. It was detected in six game farms in the 1990s, according to FWP’s website.
Infected farmed fallow deer were found positive in Sheridan and Richland counties, and infected farmed elk were found in Granite, Park, Big Horn, and Carter counties. In 1993, after the disease was confirmed in captive elk on the Big Horn County game farm, an effort was made to survey free-ranging wildlife in the area for the disease. Forty-one mule deer and three white-tailed deer were collected from an adjacent cattle ranch from November 1993 through January 1994, and samples were submitted for bTB testing.
Two mule deer had suspicious lesions consistent with bTB infection. M. bovis was isolated from lymph nodes of one of those deer. M. bovis has also been detected in a few coyotes in that area. In August 1994, additional wildlife surveillance efforts were carried out and 130 mule deer, 15 white-tailed deer, 15 coyotes, 1 pronghorn antelope, 1 elk, 3 porcupines, and 1 rabbit were collected. Bovine TB was detected in just one of the 15 coyotes sampled during this effort. In 1995, 7 coyotes were collected for testing, and bTB was detected in 1 of those coyotes. Little wildlife surveillance was conducted around the other game farms, in part due to low wildlife densities in those areas.
“Active wildlife surveillance has not been conducted in these areas since 1995.”
Ramsey noted a lot of effort has gone into eradicating the disease, yet it has popped up in wildlife in parts of New York, Minnesota, Indiana and Ontario and is considered prevalent in wildlife in parts of Hawaii, Michigan, Alberta, and Manitoba. In 2017 the disease was detected in South Dakota cattle but not wildlife.
“A recent financial analysis found that it would cost $1.5 million annually over 30 years to eradicate the disease in wildlife in Michigan,” according to FWP’s report.
The disease can be spread by “direct contact, inhalation of droplets expelled from infected lungs, and ingestion of contaminated feed or milk,” according to the U.S. Department of Agriculture’s website. Although cattle can be tested for the disease, there is no live test for wildlife.
“The insidious part of this disease is that it can infect so many other kinds of wildlife,” said Emily Almberg, an FWP wildlife research specialist.
Skunks, raccoons and weasels can contract the disease. One of the methods of controlling an outbreak calls for regular trapping of such critters. Coyotes are also known “sentinel species” because they eat other wildlife, meaning USDA’s Wildlife Services would likely be called in to kill coyotes to be tested for TB should a case be detected.
“It gets really tricky to control quickly because there are so many potential hosts,” Almberg said.
Bovine TB can also infect humans, although cases are unusual. “Humans can be infected by drinking raw milk from infected cattle, inhaling infective droplets from an infected animal, or by contact with infective body fluids via open wounds,” according to FWP. For that reason hunters are being advised to wear rubber or latex gloves when they gut their deer and to thoroughly clean any knives, saws or other equipment.
“There has been at least one confirmed case of transmission of bTB to a human from an infected white-tailed deer,” according to FWP’s report. “In that case, the disease is believed to have been transmitted via bodily fluids from the infected deer through an open wound on the hunter during the field dressing process.”
FWP has already schooled its staff on what to look for in a bovine TB-positive animal. In advanced cases white pustules could be present on the lungs, liver or in the chest cavity, Almberg said. FWP is also extracting lymph nodes at check stations to check for TB, the same check stations where other lymph nodes are being extracted to test for CWD.
“We don’t need to do a full-on surveillance at this point,” Ramsey said.
In most cases where there have been TB detections, Ramsey said state officials have been able to rely on hunting seasons to test enough deer.
Although the Department of Livestock checks cattle for the disease there is no vaccination to prevent it.
“While some deer may develop severe disease within a few months, many are asymptomatic for years. Over time, infection results in gradual debilitation and emaciation. Other common symptoms in cervids surviving to late-stage disease may include coughing, nasal discharge, and difficulty breathing,” according to FWP.
Given the cost and problems of trying to deal with an outbreak, having a plan in place to halt bovine TB’s spread is key, Ramsey said.
“We need to keep it out of our wildlife and cattle.” she said.
“Hopefully we’ll get people looking for it so we don’t miss it if it’s there.”