Clinically speaking, foot rot is a subacute or acute necrotic (decaying) infectious disease of cattle, causing swelling and lameness in one or more feet. The disease can become chronic, with a poorer likelihood of recovery if treatment is delayed, resulting in deeper structures of the toe becoming affected. Weight gain is significantly reduced when grazing cattle contract the disease. In one three-year study, Brazle (1993) reported that affected steers gained 2.3 lbs. per day, while steers not affected gained 2.76 lbs. per day. Foot rot is usually sporatic in occurrence, but the disease incidence has been reported as high as 25 percent in high-intensity beef or dairy production units. Approximately 20 percent of all diagnosed lameness in cattle is actually foot rot.

What's the Cause?

Cause of foot rot can vary. Normally, an injury of some type, mechanical or otherwise occurs or there is a softening and thinning of the interdigital (between the toes) skin by continuous exposure to wet conditions (common in Spring and late Fall). These situations are typically the cause of entrance points for infectious agents. A fairly nasty (and quite common) bacteria known as Fusobacterium necrophorum is the organism most often isolated from infected feet, but can also be found in non-diseased, interdigital skin. The majority of F. necrophorum isolated belong to one of two types (types A or B) which produce toxins that cause necrosis (death) or decay of the infected tissues. F. necrophorum is also isolated from liver abscesses in feeder cattle, necrotic stomatitis in calves, and calf diphtheria. F. necrophorum appears to act cooperatively with other bacteria, such as Bacillus melaninogenicus, Staphylococcus aureus, Escherichia coli, and Actinomyces pyogenes, thereby decreasing the infective amount of F. necrophorum necessary to cause disease. Bacteroides nodosus, the organism causing foot rot in sheep, may cause an interdigital skin surface infection in cattle, allowing entrance of F. necrophorum and thereby causing foot rot.

Regardless of the source once loss of skin integrity occurs, bacteria gain entrance into subcutaneous tissues and begin rapid multiplication and production of toxins that stimulate further continued bacterial multiplication and penetration of infection into the deeper structures of the foot.

Transmission

Feet infected with F. necrophorum serve as the primary source of infection for other cattle by contaminating the environment. Researchers and veterinarians disagree on the length of time F. necrophorum can survive off of the animal, but estimates range from one to ten months. This means that the condition can crop up again in a given area even after no cattle or no observed cases appear for a period of time.

Clinical Signs

Foot rot occurs in all ages of cattle, with increased case incidence during wet, humid conditions. When case incidence increases in hot and dry conditions, attention must be directed to loafing areas, which are often crowded and extremely wet from urine and feces deposited in small shaded areas. The first signs of foot rot, following a growth and development period of the organism for a period of five to seven days, are lameness, acute swelling of interdigital tissues, and swelling evenly distributed around the hairline of both hooves. Eventually the interdigital skin cracks open, revealing a foul-smelling, necrotic, core-like material. Untreated, the swelling may progress up the foot to the fetlock or higher. More importantly, the swelling may invade the deeper structures of the foot such as the navicular bone, coffin joint, coffin bone, and tendons.

A condition known as �Super Foot Rot,� has been noted in some areas of the country. It received this name due to the rapid progression of symptoms, severity of tissue damage, and lack of response to standard treatments. There is reported response to Naxcel� as an effective treatment. Standard treatments such as footbaths have not been effective in preventing the disease.

Diagnosing the Problem

Diagnosis of foot rot can normally be made by examination of the foot, looking at the characteristic signs of sudden onset of lameness (usually one foot), elevated body temperature, swelling between the digits (toes), and separation of the interdigital skin (skin between the toes). A potential problem is that there are other conditions that can cause lameness in cattle and can be mistaken for foot rot and would require different treatment. These include: interdigital dermatitis, sole ulcers, sole abscesses, sole abrasions, infected corns, fractures, septic arthritis, and inflammation or infection of tendons and tendon sheaths, all of which generally only involve one claw of the foot and not the areas of skin or soft tissues between the toes or claws.

Digital dermatitis (hairy heel warts) is often confused with foot rot because of foot swelling and severity of lameness. Digital dermatitis affects only the skin, beginning in the area of the heel bulbs and progressing up to the area of the dewclaws; whereas, foot rot lesions occur in the interdigital area and invade the subcutaneous tissues. Cattle grazing endophyte infected fescue pastures that develop fescue toxicity, causing loss of blood circulation to the feet and subsequent lameness, are sometimes mistaken as having foot rot.

Treatment

Treatment of foot rot is usually successful, especially when caught and started early in the disease course. Treatment should always begin with cleaning and examining the foot to establish that lameness is actually due to foot rot and not one of the other conditions discussed. At this point, a topical treatment of your choice should be applied. Some very mild cases will respond to topical therapy only. Most cases require the use of systemic (injectable) antimicrobial therapy. These might include:

1) LA 200�

2) Bio-Mycin 200�

3) Procaine penicillin G�

4) Tylan 200�

5) Sustain III� (sustained release Sulfamethazine) boluses are over the counter pharmaceuticals that have proven effective as a treatment of foot rot.

6) Naxcel� - require order of a liscensed veterinarian

7) Micotil� - require order of a licensed veterinarian

8) Albon S.R. � (sustained release Sulfadimethoxine) boluses are antimicrobials restricted to the use by the order of a licensed veterinarian, and have also shown to be effective in the treatment of foot rot.

If at all possible, affected animals should be kept in dry areas until healed. If improvement is not evident within three to four days, it may mean the infection has invaded the deeper tissues. Infections that do not respond to initial treatments need to be re-evaluated by your veterinarian soon rather than later. He or she will want to determine if re-cleaning, removing all infected tissue, application of a topical antimicrobial, and bandaging are appropriate, along with an antimicrobial change. In the more severe cases, management of the animal will be between salvaging for slaughter (following drug withdrawal times), claw amputation, or in valuable animals, claw-salvaging surgical procedures. Your veterinarian will be able to provide you with information you may need in making this decision.

Prevention � The Best Defense is a Good Offense

Preventive measures are centered on the prevention of mechanical damage to the foot as caused by frozen or dried mud, brush-hogged weeds or brush, stubble, and minimizing the time cattle must spend standing in wet areas. Other preventive measures presently used include the use of footbaths (most often used in confinement beef or dairy operations, 10 percent Zinc Sulfate � 16 lbs per 20 gallons of water or 10 percent Copper Sulfate � 16 lbs. per 20 gallons of water). Footbaths are not commonly very practical in range cattle situations and are normally used primarily in dairies. Other preventative measures include feeding low levels of chlortetracycline, addition of organic and inorganic zinc and organic iodine to the feed or mineral mixes, and vaccination.

Low level feeding of chlortetracycline (CTC) is labeled through the Food and Drug Administration for beef cattle, for the reduction of liver abscesses at 70 mg per head per day. F. necrophorum is the major infective agent in liver abscesses and foot rot in cattle. CTC is labeled at 350 mg per head per day (at least 0.5 mg per lb. per day) in beef cattle under 700 lbs., and 0.5 mg per lb. per day in cattle over 700 lbs., for the prevention of anaplasmosis. Consequently, many mineral mixes and commercial supplements are formulated to provide 350 mg per head per day, to control those diseases listed on the CTC label. Since foot rot is caused by the same organism as liver abscesses, some control of foot rot should occur at the 350 mg per head per day level. Due to the difficulty in conducting studies for a disease with low incidence, large controlled comparative studies evaluating the effectiveness of continually feeding CTC to grazing stocker cattle have not been reported. Most research trials indicate that average daily gain is increased in grazing cattle by .1 to .3 lbs. when CTC is included in a free choice mineral mix in grazing cattle. All this goes to say that while CTC is commonly used as a preventative for foot rot, there is no scientific documentation that this treatment does, in fact, work.

When cattle are moderately to severely deficient in dietary zinc, supplemental zinc may reduce the incidence of foot rot. Improvements have been seen in foot health even when zinc is not deficient in the diet when organic sources are included and overall zinc concentrations in supplements are increased. Zinc is important in maintaining skin and hoof integrity; therefore, adequate dietary zinc should be provided to help minimize foot rot and other types of lameness. In a three-year study, zinc methionine added to a free-choice mineral supplement reduced the incidence of foot rot and improved daily weight gain in steers grazing early summer pasture (Table 1).

Additionally, feeding of organic sources of iodine have been shown to also be effective in this type of a system. Iodine from EDDI (ethylene diamine dihydriodide) is believed effective in preventing foot rot although it should not be routinely fed at elevated levels year-round.

A commercial vaccine approved for use in cattle as a control for foot rot is available. Reported results by producers and veterinarians have been mixed from their use of this product, and controlled studies have not been reported. Your veterinarian, by knowing your specific geographic area, will be able to assist you in initiating preventive measures for foot rot.

Conclusions

Foot rot is one of many conditions of the foot that cause lameness in cattle. For treatment to be effective it must be started early in the course of the disease. It is necessary to have a break in skin integrity for foot rot to occur. The most important preventive measures are centered on the protection of interdigital skin health. All this said, however, solid preventative measures can dramatically reduce the expense of a foot rot outbreak and in general may be the most cost-effective method available to the cattleman.