Cattle Diseases

The Nasty Seven

Keep these herd-health robbers top of mind to minimize losses throughout the year. (DTN/Progressive Farmer photo by Sam Wirzba)

From the commercial cow herd to the feedlot, cattle diseases are a growing concern. Veterinarians are stressing the importance of keeping herd health and biosecurity top of mind, as they will have a large impact on safety and profit levels going forward.

1. BOVINE VIRAL DIARRHEA

Commonly referred to as BVD, this disease is found most often in cattle younger than 2 years of age. It is the most costly viral disease in U.S. cattle herds today. One estimate reports exposure of feedlot animals to a persistently infected (PI) case of BVD will cost more than $67 per head in performance loss and fatalities.

BVD can infect several organ systems, causing suppression of the immune system, respiratory disease, infertility and fetal infection. Early infection of a bred cow can result in the birth of a PI calf. Once they are born, PI cattle shed the BVD virus throughout their entire lives.

"With BVD, you see a lower calf crop," said Tom Hairgrove, livestock and animal systems coordinator at Texas A&M University. "Vaccine programs are important, but they are only a part of a good herd-health program. Purchasing a PI animal or a bred female with a PI fetus can result in reduced reproduction for years. It is important to know your source of replacements and the health status of that herd."

Kathy Simmons, chief veterinarian for the National Cattlemen's Beef Association, added the cattle industry has worked to control BVD through research. The focus has been on a better understanding of the epidemiology of BVD, a wider availability of diagnostic tests to detect the disease and a clearer understanding of the economic impact it has on cattle herds. Visit www.bvdconsult.com for more information.

2. ANAPLASMOSIS

Good animal husbandry can help producers get a handle on the common infectious disease anaplasmosis. Also known as yellow bag or yellow fever, anaplasmosis is transmitted by exchange of blood. That means use of dirty ear tags, surgical instruments or needles spreads the disease, as do blood-sucking flies and ticks. It is estimated anaplasmosis costs cattle and dairy producers more than $300 million each year.

Cattle infected when they are under 2 years old usually adapt to the infection and are lifelong carriers. When older cattle become infected, symptoms include fever, weight loss, jaundice, abortion, anemia and erratic behavior because of a lack of oxygen to the brain. In some cases, anaplasmosis is fatal.

Hairgrove noted herd rebuilding is a common way that infected cattle are introduced to an operation.

"Anytime you comingle infected and uninfected cattle, you are risking the development of clinical anaplasmosis," he said. "Bovine anaplasmosis is a disease that has to be carried by flies or ticks, or bad husbandry practices."

Cases of anaplasmosis are more common in the summer and fall, when populations of insect carriers are higher.

There is one commercially available vaccine against anaplasmosis in the U.S., which will reduce death loss but won't prevent the disease. Common treatment includes the use of oxytetracycline and, in some severe cases, blood transfusions. Visit www.anaplasmosis.com for more information.

3. TEXAS CATTLE FEVER

A disease that almost wrecked the Texas cattle industry in the 19th century, Texas cattle fever (TCF), is still on the radar for producers throughout the country.

Caused by cattle ticks, the disease gets its name from its discovery in the longhorn breed during the days of the cattle drives from Texas to northern markets. TCF didn't affect the naturally immunized longhorns, but other cattle they came into contact with got sick and died. The fabled era of the Texas cattle drives ended in large part because of cattle fever. To deal with the problem, the state created the Texas Animal Health Commission (TAHC) in 1893.

A Cattle Fever Tick Eradication Program (CFTEP), established in 1906, helped eradicate the disease in the U.S. by 1943. Today, however, it thrives in Mexico, forcing the CFTEP to establish a permanent quarantine, or buffer zone, along the Texas-Mexico border.

The quarantine zone runs about 500 miles along the Rio Grande River, from Del Rio to Brownsville. Sixty-eight horsemen, known as "Tick Riders," travel the banks of the Rio Grande looking for stray cattle and inspecting domestic livestock and deer. The USDA's Agriculture Research Service estimates these riders save producers in the U.S. close to $1 billion a year in potential livestock losses.

Dee Ellis, state veterinarian and executive director of the TAHC, reports no recent clinical cases of Texas fever.

"Texas cattle fever, tick-infested herd numbers are relatively low inside the quarantine zone compared to seven or eight years ago. But, it is the infested herds in the free zone that worry regulators the most because they are not normally held to the same inspection requirements as cattle and horses in the permanent quarantine zone," Ellis explained.

When an infestation is detected, animals on the premises and those areas adjacent can be quarantined while treatment takes place. Treatment includes dipping/spraying cattle, use of injectable Dectomax and/or vacating the premises, thereby removing hosts for the ticks. Visit www.tahc.state.tx.us/news/brochures/TAHCBrochure_FeverTick.pdf for more information.

4. BRUCELLOSIS

A contagious, costly disease that can also affect humans, brucellosis is still not eradicated but is mostly contained.

A Disease Surveillance Area (DSA) for brucellosis exists in parts of Idaho, Wyoming and Montana near Yellowstone National Park because of a brucella reservoir in elk. States that have problems with feral swine also have a reservoir of swine brucellosis. In Texas, about three million feral swine harbor a brucella reservoir.

"Approximately 10% of Texas feral swine are thought to be infected with Brucella suis, which causes diagnostic complications when cattle test positive. Those cattle will test positive for Brucella suis, as they do for Brucella abortus [the cattle strain]," said Dee Ellis, state veterinarian. "The only way to tell the difference is to attempt to culture milk or lymph nodes at slaughter, and those tests are often not successful."

Brucellosis is mostly a ruminant disease, also known as contagious abortion or Bang's disease. In humans, it's known as undulant fever.

An infection decreases milk production and causes weight loss, abortions, infertility and lameness. It can spread rapidly and is caused by a group of bacteria known as the genus Brucella. These bacteria are shed in milk, an aborted fetus, afterbirth or other reproductive tract discharge. It is spread by direct contact with an infected animal or some part of that animal. There is no cure.

The U.S. has a Brucellosis Eradication Program that has shown good results. In 1956, there were 124,000 infected herds in the U.S. By 1992, there were 700 affected herds. Since then, the number of affected herds has fallen into the single digits. Visit www.aphis.usda.gov/animal_health/animal_diseases/brucellosis/downloads/bruc-facts.pdf for more information.

5. FOOT-AND-MOUTH

While economically devastating and highly contagious, thankfully foot-and-mouth disease (FMD) has not been present in the U.S. since 1929. It's important to know, however, that this transboundary disease of cloven-hoofed and wild animals is still high on the priority list of all health experts.

NCBA's Simmons said any outbreak of this disease would immediately disrupt animal agriculture trade and could cost the beef cattle industry close to $7 billion in lost exports. An outbreak would result in "aggressive quarantines, substantial restriction on animal movement and depopulation of infected and exposed animals," she said.

Animals with FMD show signs of fever, salivation, loss of appetite and blister-like lesions on the mouth, tongue, nose, feet and teats. USDA's Animal and Plant Health Inspection Service (APHIS) manages FMD risk through import restrictions, surveillance and preparedness.

"The strategy has evolved to consider vaccination for FMD, as widespread depopulation would not be feasible in a large outbreak in the United States," Simmons explained. She added NCBA is working closely with APHIS and other stakeholders in preparedness activities.

Simmons recommends producers have a clear preventive herd-health plan and implement biosecurity measures based on guidelines established by the Beef Quality Assurance (BQA) Program. BQA guidelines give five major components of a good biosecurity plan -- assessment, resistance, isolation, traffic control and sanitation. The plan includes targeting pathogens, following vaccine protocols, good nutritional management and developing production practices with an eye on reducing the spread of disease within the herd along with parasite-control measures and accurate treatment and health records. Visit www.fmdinfo.org/fmdsymptoms.aspx or www.bqa.wsu.edu/pdf/biosecurity.pdf for more information.

6. TRICHOMONIASIS

Most producers know this costly problem simply as "trich." Unfortunately, it is spreading to cattle across the country.

Once confined mostly to the Mountain West states, trich has spread south into Texas and across the Mississippi River into previously unaffected states like Georgia, Tennessee and the Gulf Coast states.

Jeff Ondrak, a bovine veterinarian at the Great Plains Veterinary Educational Center, at the University of Nebraska-Lincoln, has spent most of his professional career studying trich. He said it's hard to put a number on exactly how many states have cattle with trich today, but its spread is undeniable.

"When you look at distribution, it's hard to think it's not a national disease," he said. "We're seeing it in places where we've never seen it before."

The protozoan organism Tritrichomonas foetus, carried by a bull, causes trich. Infected bulls show no outward signs of the disease and carry the infection for life. There are tests to identify trich, but the only cure is a one-way trip to the slaughterhouse. Infected cows will abort their calves and have extended breeding seasons and a reduced calf crop.

Trich creeps into a herd without warning but leaves telltale clues in its wake.

"If your conception rates go down to 75 or 80% after you've had bulls on the cows for five months, or cows are supposed to be six or seven months bred, and many are only two or three months bred, or you just have more open cows than normal -- that's got trich written all over it," Hairgrove said.

There is a vaccination for trich, but Hairgrove said to be effective, it must be used correctly.

Nebraska's Ondrak said some producers are reluctant to make the vaccination a part of their herd-health protocol because of cost. That decision, he said, is best made on an individual basis.

"Vaccination does reduce calf loss if it's used in a timely manner right before breeding," Ondrak said. "You have to look at the situation locally. Are you in an area where it's widespread, or is the prevalence low? Does the cost of vaccination balance with the risk?"

Where trich is prevalent, vaccinating cows and testing bulls may well pay off.

"Trich is the disease that I think is costing us the most money in Texas," Hairgrove said. "Our studies show it might cost producers in Texas $100 million a year. We have about 4 million cows. That's $25 a cow."

At a 2014 joint national conference of the U.S. Animal Health Association and the National Institute for Animal Agriculture, Texas A&M University economist David Anderson presented the results of a study showing an annual revenue loss from trich of almost $37,000 on a "representative" ranch in west Texas. The ranch had 355 cows and a weaning rate of about 85%.

"When you dig into the numbers, it basically makes that ranch unprofitable to where they're losing money," Anderson said. "As they try to reborrow money and dig themselves out of a hole, they get further under water, and it becomes, long-term, not a financially sustainable operation."

Today, 28 states have some type of trich regulations and/or testing procedures. Most require that breeding bulls test negative for trich at change of ownership or entry into the state. Ondrak would like to see more consistency across state lines in regard to the period of time a trich test is valid and the age at which a bull does not require testing. Visit www.trichconsult.org for more information.

7. CALF SCOURS

University of Nebraska-Lincoln bovine veterinarian Ondrak tells his senior veterinary students one of the costliest diseases for today's cattle producers is calf scours. True, other diseases often get more attention. But Ondrak believes the all-too-common calf scours is one thing that can really do serious damage to any cow/calf operation.

"During my years in practice, the biggest financial losses I've seen have been from calf scours, both in death loss and the costs of labor and treating sick calves," he said. "I believe everybody should be on guard against calf scours."

Scours is not actually a single disease but a symptom associated with several diseases and characterized by diarrhea. The diarrhea prevents the intestines from absorbing fluids. Both infectious and noninfectious agents cause scours, but the calves that don't survive usually die from dehydration.

Fresh pastures and clean feeding and calving areas can go a long way toward preventing scours. In addition, a vaccination is available for use in cows that stimulates production of antibodies to infectious agents that can cause scours. The calf benefits from this when it consumes colostrum shortly after birth. There is also a preventative bolus for newborn calves that supplements the immune system. If scours is a common problem, producers should check with their veterinarian to see if the vaccination or bolus are options for their operations.

It's also important to keep dams in good health and at a body condition that allows them to produce a good quality and quantity of colostrum for their newborn calves. A dam with nutritional deficiencies is more likely to have a calf susceptible to scours than one that is well-fed and healthy. Visit animalscience.tamu.edu/wp-content/uploads/sites/14/2012/04/beef-calf-scours.pdf for more information.

(VM/CZ)