The University of California, Footwarts Task Group recently reported on their current findings about footwarts in dairy cattle at several UC Davis extension meetings. They have been studying footwarts in California dairy cattle since the early '90s using a variety of methods. Each of the methods, whether they were epidemiological, diagnostic or treatments, has provided valuable information about footwarts.

Dr. David Hird, UC Davis School of Veterinary Medicine, reported on the epidemiological studies to determine what factors might be predisposing some cattle to footwarts. The two major factors which seem to contribute to an increased amount of warts of dairies were buying heifers and environmental conditions. On a herd basis, dairies which purchase heifers are more likely to have footwarts. Dairies which purchase more than 60% of their heifers are 6.5 times more likely to have footwarts. Dairies which have muddy condition, particularly along the feed alleys where the cows stand to eat, have a far greater chance of having footwarts. These dairies are over 20 times more likely to have footwarts than dairies which have clean feeding pads on which the cows stand. He also reported that cows in larger herds tend to have more warts; heifers are more likely than older cows to have warts; and that footwarts are most likely to appear between 80 and 140 days in milk. In all the studies, about 50% of the animals never got warts.

The causes of footwarts has also been investigated. Dr. Richard Walker, California Veterinary Diagnostic Laboratory, Davis, indicated that because of the occurrence pattern and response to antibiotics they felt the cause of footwarts was an infectious agent. Their work strongly suggests that spirochete bacteria, probably two strains of Treponema, are very important. The spirochetes are found by the millions near the surface of the footwarts. It is the cow's response to the invasion by these spirochetes which results in the wart-like lesions on the feet. They have also found that the cow makes an immune responses to the spirochetes. Other bacteria and mycoplasma (not the mastitis types) are also found in smaller numbers. Viruses, fungi and protozoa are not thought to play an important role in causing footwarts.

Dr. Deryck Read, California Veterinary Diagnostic Laboratory, San Bernardino, has looked at the pathology of the footwart lesions. He notes that the character of the early red and bleeding lesions is due to the growth of blood vessels near the skin surface. Using the electron microscope, he found the spirochetes in very large numbers close to the surface of the warts. In attempts to transmitted the disease from one cow to another, they found that by scraping off the surface of the warts, the warts tended to heal rapidly. When he kept a cows foot wet and lowered the oxygen content on the skin, they were able to transfer a footwart from one cow to another. On the same cow without wetness and lowered oxygen, they could not transmitted the disease. In the transmission studies, spirochetes were always found in the newly transmitted lesions.

Treatment studies have been conducted recently by Dr. Steven Berry, UC Davis Animal Science Extension. They have done field trials using foot wraps and foot spraying. Foot wraps worked well using a slurry of about 10 grams of either oxytetracycline or lincocin to apply on the wart and then wrapping. They also tested hand-held, garden sprayers with an antibiotic-water mixture. Spraying was found to be less time consuming and required no restraint compared to foot wraps. They found oxytetracycline at 25 mg/ml or lincocin at 8 mg/ml to be effective foot spray concentrations. Spraying was done in the milking parlor after the foot had been washed with water. Spraying is usually repeated daily for 10-14 days. The antibiotic spray is intended to soak the wart lesions. With all the treatments they tested, there were some recurrences of the warts.

The take-home message from their studies seems to be that dairies are more likely to get footwarts if they purchase heifers and have muddy corrals. The muddy corrals provide the wet conditions with low oxygen which favors the invasion of the bacterial spirochetes. So improved corral management especial where the cows are going to stand for long periods of time may help to prevent the disease. Once the disease occurs, foot spraying in the parlor is an effective means of control. As almost 50% of the cows never get warts, it is suggested that only cows with footwarts be sprayed and not all the cows in the milking herd.