3/29/2014 7:00 AM
By Jane W. Graham Virginia Correspondent
Can a creature that died 50 years ago kill a herd of cattle today? It’s one of the many questions some farmers in Virginia and West Virginia want answered as they try to come to terms with massive losses of cattle from botulism.
Two farmers said they still have more questions than answers, but they have learned that spores of botulism bacteria in balage they ensiled last summer are the probable cause of illness in their cattle.
They also learned that these spores can live for a half century or more and can kill long after they are deposited in the soil by the decaying body of a dead animal.
The disease that killed cattle at Tom LeFevre’s farm in Bunker Hill, W.Va., and Roger Forrester’s farm in Wytheville, Va., has been identified as botulism poisoning. But the big question quickly became: “What can we do?”
In both cases, it took some time to find out that there is an antitoxin for the bacterium that is not widely known among veterinarians.
The outbreak late last year left Forrester with 34 dead feeder cattle and LeFevre with 46 dead replacement heifers, all five months pregnant. Another West Virginia farmer with eight sick animals lost one animal, LeFevre said.
LeFevre said he had taken three of his animals to the Virginia-Maryland Regional College of Veterinary Medicine on the Virginia Tech campus, where they were saved with an antitoxin produced at the University of Pennsylvania School of Veterinary Medicine. LeFevre said he shared his knowledge with his neighbor, who was then able to obtain the medicine for his cattle.
Both LeFevre and Forrester reported symptoms exhibited by their cattle as resembling symptoms of shipping fever, also known as bovine respiratory disease; the cattle were droopy and slobbering. But it soon became evident that something else was wrong as the cattle continued trying to eat, but were unable to swallow. Their body temperatures were normal or below normal, and they became weak and went down as the toxins spread through their bodies, paralyzing them and ultimately killing them. Some cattle died quickly, while others lingered for several days.
Veterinarians from two universities confirmed that botulism is common in the environment.
Dr. Raymond Sweeney of the University of Pennsylvania School of Veterinary Medicine — the school that developed both a botulism vaccine for horses and antitoxins for both horses and cattle — has traced the history of botulism research from its beginning 30 years ago.
Sweeney recalled that his colleague, Dr. Robert Whitlock, now retired, responded to an outbreak of botulism among horses at Brandywine Racetrack in Delaware 30 years ago. He created a botulism laboratory at the New Bolton Center, Penn Vet’s large animal hospital. Sweeney said Whitlock was able to develop an antitoxin to fight the poisoning, as well as a diagnostic laboratory to test for the disease in animals and animal feeds.
Creating the antitoxin takes a long time and involves injecting a normal horse with increasing doses of the vaccine to create the antitoxin. Sweeny said the process is quite involved and requires much testing along the way.
After developing the antitoxin for horses, Whitlock then developed an antitoxin for cattle using a similar procedure. The university still has a supply of the antitoxin produced from the initial cow, but the animal is now dead and there is not another animal from which to make more antitoxin.
Sweeney explained that his laboratory makes this dwindling supply available to farmers who need it as a humanitarian act. He stressed that the school is not a commercial operation, but a research facility, and that the $150 cost for one treatment of antitoxin is at cost of production or below. He said there is a company that produces the antitoxin for horses at a cost of $600 per treatment.
The botulism spores appear most often in balage, fermented grasses or grains bagged in plastic to keep oxygen out. Sweeney said the spores change into the toxin-producing form when placed in an environment without oxygen.
If fermentation of the balage or haylage is inadequate, then not enough acid is produced to prevent the botulism organisms from producing toxin. A silage/balage pH of below 5 is necessary to inhibit toxin production.
Sweeney said that botulism is very common in horses and cattle in the Mid-Atlantic States and Kentucky. The Virginias seem to have had an unusual number of cases this year. However, botulism can occur anywhere, and he noted that last year Texas reported a case, something that the local veterinarian did not recall seeing in the past.
Dr. Dee Witter, an Extension veterinarian with the Virginia-Maryland Regional College of Veterinary Medicine, said he was taught in vet school that the botulism spores got in stored forages when a dead animal’s body was baled into the hay or balage. He said newer findings show that spores remain in the soil for many years and can be picked up by hay rakes during the hay-making process.
Sweeney agreed, indicating that the type of botulism found in the more recent cattle outbreaks was more typical of what is seen with a soil source of botulism spores rather than a dead animal in a bale.
Whittier said recommendations are for forage balage to have a moisture content of 50 to 60 percent. Both Forrester and LeFevre reported moisture contents above 60 percent when they baled. Whittier said moisture helps in the fermenting process to keep feed acidic enough to kill the spores.
LeFevre said he made the balage because of the moisture in his area, which included 6.5 inches of rain in the weeks before harvest and a moist, humid atmosphere. He said he feels like he may have raked up a mud ball of botulism spores. He compared it to mushrooms appearing from spores one year and then missing several years before appearing again in the same place.
Since the outbreak, Forrester has vaccinated the remaining feeder cattle on his farm, fed them the same balage without more illness and sold them. He said he plans to be proactive by inoculating his balage next year as he harvests it in an effort to kill the spores.
LeFevre said he is still wrestling with his losses and what to do in the future.
One thing both farmers are sure about is that they want other farmers to know that this can happen and that steps can be taken to prevent it.
Forrester was joined recently by Phyl Snapp, owner of S&W Fertilizer in Wytheville, to get the word out to farmers. Snapp hosted an informational dinner meeting attended by more than 125 people to help the farming community better understand the problem.