Footwarts were first described by two researchers from Italy in 1974. Since that time they have been found in almost every country in the world. Footwarts were first seen in New York in the mid 1970's and first reported in California in the San Jacint o area in the mid 1980's. The precise cause of the disease is unknown but it is an apparently contagious, painful, wart-like disease of the feet of dairy cattle. The prevalence in California and many other states and countries seems to be in creasing. Ep idemiological studies by Dr. David Hird and his graduate students from the School of Veterinary Medicine at UC Davis have indicated that muddy corrals and purchasing outside heifers are consistent risk factors for the disease.
During 1995 and 1996 researchers at UC Davis have conducted studies on the etiology (Dr. Richard Walker), pathogenesis (Dr. Deryck Read), epidemiology (Dr. David Hird), and clinical treatment of papillomatous digital dermatitis (Dr. Steven Berry) in d airy cattle. This research has been funded by the California Milk Advisory Board, the Livestock Diseases Research Laboratory of the School of Veterinary Medicine, and the Division of Agricultural and Natural Resources of the University of California. Thi s report will summarize the results of the clinical treatment trials during 1995 and 1996.
During the summer of 1995, clinical trials were conducted on 3 California dairies. Two of the dairies milked about 800 cows and one milked about 900 cows. All 3 dairies had an initial prevalence of footwarts of approximately 30-50%. This study was des igned to test 2 antibiotics; oxytetracycline (OTC) and lincomycin/spectinomycin (LS50) at 2 dosage levels and one non-antibiotic (RotNot™) against non-treated control cows. The treatments were administered using a 2 liter, hand held sprayer and wer e applied once per day for a total of 10 days (see picture).
The dosages of the antibiotics were 1 mg/ml oxytetracycline (LowOTC), 4 mg/ml oxytetracycline (HighOTC), 0.5 mg/ml lincomycin/spectinomycin 50 (LowLS50), 1.0 mg/ml lincomycin/spectinomycin 50 (HighLS50), and RotNot™ at label concentration (1 ml/ L). We used these concentrations because they were reported to work in footbaths. Using these treatments as in-parlor sprays allowed us to compare treatments against control cows. Cows were identified and randomly assigned to 1 of the 6 groups. They rece ived leg bands which identified which group they belonged to. During the treatment phase of the trial, the cows had their rear feet washed off with the drop hose and the treatment solution was applied to the rear feet, saturating the foot from the dewcla ws down. The treatment solutions were applied to the whole foot including the interdigital space once per day during milking by study personnel. Control cows had their feet washed off but were not treated. During enrollment and evaluations, lesions were scored for severity (1-4) with 4 being a very large, mature lesion with hairy fronds on the surface of the lesion. The lesions were also assigned a pain (0 or 1) and activity score (0 or 1). The cows were evaluated after the 1st week of treatment (day 5) , after the 2nd week of treatment (day 12), after one month, and after 3 months.
The RotNot™ treatment: was not different from the control on the first 2 dairies and was not used as a treatment on the 3rd dairy. When the percent of cows which were healed (lesion score <1 and pain and activity = 0) were comparedwefoundat30 days thatHighLS50 was better than the controls on all 3 of the dairies, LowLS50 was better than the controls on 2 of the 3 dairies, and HighOTC was better than the control on 1 of the dairies. We found the percent of cows healed at 90 days was better th an the controls only for the HighLS50 treatment on all 3 dairies. The effects of treatment were more apparent at 30 days than at 90 days.
In 1996, we used 2 antibiotics at dosages reported to work as in-parlor spray treatments. We used oxytetracycline at a 25 mg/ml dosage and lincomycin at 8 mg/ml. Cows were randomly assigned to treatment or control groups on 2 dairies. The treatment gr oups were oxytetracycline for 2 weeks (Oxytet1), lincomycin for 2 weeks (Linco1), oxytetracycline for a second 2 week treatment (Oxytet2), lincomycin for a second 2 week treatment (Linco2), and control groups. The cows were treated for weeks 1 and 2 of t he trial, then not treated for 2 weeks. The Oxytet2 and Linco2 cows were then treated for a 2nd week period (weeks 5-6). Cows were evaluated in the same way as 1995 for lesion score, pain, and activity of the lesions. We evaluated cows at approximately 1 5 days, 45 days, and 90 days after beginning the trials. Figure 1 shows the percent of cows healed at the various evaluations for dairy 3 (this dairy participated in the studies both years). At day 51, both the Lincol and Linco2 treatments were different from the controls, while at 91 days only the Lincol treatment was different than the controls. These results were similar on the second dairy in 1996, although we had fewer cows per group.
The results from these 2 years of trials indicate that the higher dosages of OTC and Lincomycin used in 1996 worked better than the lower dosages used in 1995 for controlling footwarts. There was no apparent advantage to using the antibiotics for a 2n d two week treatment (week 1-2 and week 5-6) over just using them for 2 weeks (week 1-2). During 1995, we noticed that a high proportion of the cows treated had recurrent lesions, so we conducted a biopsy trial in 1996 to determine if cows treated with a ntibiotics and apparently cured still had evidence of infection at 30 days post treatment. We will report those results later.
It should be remembered that use of antibiotics to treat footwarts in dairy cattle is EXTRA LABEL DRUG USE and legally requires a veterinarian's prescription. Also, milkers should NOT be handling antibiotics while they are milking cows. The in-parlor spray treatments should be applied by someone trained to evaluate the feet and apply the solution during milking.