Three Strands of Protection

By Boyd Kidwell
Progressive Farmer Contributing Editor

It's those dramatic outbreaks of mad cow or foot-and-mouth disease that capture the headlines. But these high-profile diseases aren't the ones putting most operations at risk. Rather, the diseases most likely to hit home are lurking just across your perimeter fence.

Rusty Kemp and his family work hard to keep their 1,100-cow beef herd at Pioneer Ranch healthy and productive. Kemp's operation is near Tryon, Neb., where he deals with everything from droughts to blizzards. But what really worries him is that stray cow or bull wandering over from another owner's herd.

THE TRICH NEXT DOOR

Kemp's biggest concern is that stray animals will spread trichomoniasis (trich) to his herd. Trich is a highly contagious venereal disease that causes infertility and abortions. Cows usually are clean of trich after a few fruitless heat cycles, but bulls are permanent carriers and transfer the disease throughout the cow herd. Other bulls catch trich from infected cows.

Calving percentages in trich-infected herds run 30% to 50% below average. That's too low for Kemp.

"A 50% calving rate on our 1,100 cows would put our operation in jeopardy," he says. "In some instances, I've only got three strands of barbed-wire fence between myself and catastrophe caused by trich in a stray cow."

Kemp had a close call about five years ago when an adjoining ranch had trich infections in its herd. He and other Nebraska cattlemen contacted state politicians and eventually got a regulation passed to make cattle owners responsible for notifying neighbors in case of a trich outbreak. The regulation also allows veterinarians to contact ranchers in an area when they identify trich in a herd. This is significant because there is no cure for trich after an animal has the disease.

"In the event of an outbreak of trichomoniasis, it's important to know who's got it to stop it from spreading," Kemp says. "Just the knowledge of where it is allows neighboring ranchers to take management steps to prevent their herds from getting infected."

Kemp chooses to run yearling beef steers in pastures adjoining the questionable cow herd. He also uses those pastures when his cow herd isn't in a breeding season, and he buys only virgin bulls.

Cattlemen who know their herd is at risk for trich may want to check with their veterinarian about a vaccine called TrichGuard. This is the first product licensed to protect against the disease. It comes from manufacturer Boehringer Ingelheim. Cows and heifers initially get two doses, two to four weeks apart. After that, a yearly dose is called for, timed about four weeks prior to breeding season. The vaccine comes in 10- and 50-dose packages. Online, the 10-dose package of TrichGuard V5L was selling for $39.95 at press time, or about $4 per dose.

ANAPLASMOSIS WRECK

During the fall months, if veterinarian Meredyth Jones gets a call to check on a sickly, weak cow, anaplasmosis is always suspected.

Jones, DVM, of the Texas A&M College of Veterinary Medicine and Biomedical Sciences, said anaplasmosis symptoms tend to appear in early fall in Texas, or about 21 to 45 days after infection. That infection usually takes place during fly and tick season, when the disease is transmitted by a parasite carried by horseflies, deerflies and some ticks. Once anaplasmosis is in a herd, any surgical instruments (including needles) not cleaned between cattle will spread the disease.

In a Kansas study, one needle used to vaccinate an infected steer was shown to have transmitted anaplasmosis to six of the next 10 animals. Middle-aged animals are often affected, with the most serious cases striking 6- to 8-year-old animals newly exposed.

In the acute phase, cattle are anemic and appear weak and sick. Affected animals may exhibit white or yellow mucous membranes. Some behave aggressively. Anaplasmosis can be fatal if not treated properly. Animals must be handled quietly during treatment or they can be killed by stress. Tetracycline-class antibiotics are a common treatment, and symptoms improve in a few days.

Prevention is by far the best way of dealing with anaplasmosis. Jones recommends the following:

--Use fly tags, treated rubs, sprays and pour-on insecticides to repel biting insects.

-- Change needles between each animal.

-- Provide chlortetracycline in feed (check with your veterinarian on proper rates) to kill the anaplasmosis organism before it replicates and attaches to blood cells.

-- Watch adult cows and bulls for signs of the disease late in the fly season.

As cattle are sold and moved across the country, naive cattle (those never exposed to anaplasmosis) can easily enter into infected herds and die. Ranchers in areas known to have high levels of anaplasmosis are urged to know the status of their herds before restocking in order to take the proper precautions and avoid loss.

BOVINE TB GETS TOUGH

While most cow/calf producers have enjoyed fairly good returns during the past few years, Michigan cattleman have had a terrible time dealing with bovine tuberculosis (TB).

TB is a contagious disease of both animals and humans. It is caused by Mycobacterium bacteria, with M. bovis being transmissible from livestock to humans and other animals. USDA began eradication efforts in 1917, and by the late 1990s TB eradication was considered a model achievement.

Unfortunately, bovine TB became endemic in Michigan's white-tailed deer herd. For the past 15 years, a small but consistent stream of cows in the state have been showing up positive for the disease. Cattle health experts say TB is transmitted by saliva of infected deer in cattle feed or water. If a cow grazes or eats feed within a few hours of an infected deer, she picks up the bacteria and may become infected.

"I consider beef farms the most at risk because cow/calf operations share grazing areas with wild deer," said Phil Durst, dairy and beef health specialist at Michigan State University.

Michigan has established a "Free Zone" over most of the state, and risk zones in areas where TB has been identified. Herds are regularly tested in a small core area of the state. All cattle are required to have radio-frequency identification tags so they can be traced back to the farm of origin if they show up positive for TB at slaughter. There is no cure for bovine TB, so identification of infected animals is the only way to help contain the number of cases. In addition, producers are urged, where possible, to store hay and feed indoors where deer can't reach it.

Michigan cattle producers were optimistic the disease was coming under control when only two new cases of TB were identified in 2012. However, four new cases popped up the first six months of 2013, and they were beyond the primary risk area.

"These cases outside the core area are discouraging, but Michigan dairy and cattle producers are working with the state Department of Agriculture and USDA to contain the disease and get beyond it," Durst says.

MEXICAN TB STRAIN CROSSING OVER

During the past few years, the Mexican strain of bovine TB has caused pain for cattle producers in several border states, including California, New Mexico and Texas. Health experts have identified these cases as the "Mexican strain" of TB and suspect the infections are a result of imported Mexican cattle.

With U.S. calf numbers at low levels, feedlots need Mexican feeder cattle. Last year, 1.6 million steers and spayed heifers were shipped across the border. The rate of TB is much higher in Mexican cow herds, and all imported calves are required to pass with negative TB tests. But animals with the disease have nevertheless slipped in.

Some of these animals were possibly incubating the disease and didn't test positive prior to crossing the border. Also, the sensitivity of the skin test for TB is approximately 85% when properly administered. This means even on its best day, the test can miss 15 out of 100 infected animals.

Bovine TB can be transmitted from humans to cattle, and, in some cases, farm workers could even be spreading the disease to cattle.

Once cattle cross the border, they are often sent to ranches for background grazing. This could allow the spread of the Mexican TB strain. Another source of infection, experts say, could be the use of Mexican roping calves at rodeo events.

(VM/CZ)

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