FOOT ROT IN CATTLE
Post no-1349Dt 04/08/2019
(Compiled & shared by-DR RAJESH KUMAR SINGH, JAMSHEDPUR, JHARKHAND, INDIA, 9431309542, rajeshsinghvet@gmail.com)
Foot rot in cattle is caused by the anaerobic bacteria Fusobacterium necrophorum. Fusobacterium necrophorum is ubiquitous in the environment of cattle as it is a normal inhabitant of the intestine and faeces. It can also remain dormant in the soil for several months.The organism contaminates areas where cattle congregate.
Foot rot in cattle should not be confused with foot rot in sheep. The two diseases are different and cross infection between the two species is not believed to occur. Foot rot in sheep requires not only a virulent strain of Dichelobacter nodosusto be present, but also Fusobacterium necrophorum.
Foot rot is a sub-acute or acute necrotic (decaying) infectious disease of cattle, causing swelling and lameness in at least one foot. This disease can cause severe lameness and decreased weight gain or milk production. Lame bulls will be reluctant to breed, and severely affected animals may need to be culled from the herd. The disease can become chronic, and if treatment is delayed the recovery prognosis is poor. This results in deeper structures of the foot becoming affected. Weight gain is significantly reduced when grazing cattle contract the disease. The incidence of foot rot varies according to the weather, season of the year, grazing periods and housing system. Foot rot is usually random in occurrence, but the disease incidence may increase up to 25 percent in high-intensity beef or dairy production units. Approximately 20 percent of all diagnosed lameness in cattle is actually foot rot.
Causes——-
Normal healthy skin will not allow the bacteria involved in foot rot to enter the deeper tissues. Mechanical injury or softening and thinning of the interdigital (between the toes) skin by puncture wounds or continuous exposure to wet conditions are necessary to provide entrance points for infectious agents. Grazing stubble on recently mowed pasture may irritate the interdigital skin as well as standing in environments heavily contaminated with feces and urine. Injury is often caused by walking on abrasive or rough surfaces, stony ground, sharp gravel, hardened mud or standing in a wet and muddy environment for prolonged periods of time. High temperatures and humidity will also cause the skin to chap and crack, leaving it susceptible to bacterial invasion. Fusobacterium necrophorum is the bacterium most often isolated from infected feet. This organism is present on healthy skin, but it needs injury or wet skin to enter the deeper tissue. F. necrophorum appears to act cooperatively with other bacteria, such as Porphyromonas levii, Staphylococcus aureus, Escherichia coli, and Actinomyces pyogenes, thereby decreasing the infective dose of F. necrophorum necessary to cause disease. Prevotella intermedia has also been implicated as causative agent for foot rot. Porphyromonas levii (formerly Bacteroides nodosus), the organism causing foot rot in sheep, may cause an interdigital skin surface infection in cattle, allowing entrance of F. necrophorum, thereby causing foot rot. Mineral deficiencies of zinc, selenium and copper seem to increase the incidence of disease.
Transmission ———
Feet infected with F. necrophorum serve as the source of infection for other cattle by contaminating the environment. F. necrophorum can be isolated on non diseased feet, as well as in the rumen and feces of normal cattle. Porphyromonas levii and Prevotella intermedia can also be isolated from the alimentary system of cattle. Since these organisms are part of the normal gut flora, they are readily available to contaminate the environment. Once loss of skin integrity occurs, bacteria gain entrance into subcutaneous tissues and begin rapid multiplication and production of toxins, further stimulating continued bacterial multiplication and penetration of infection into the deeper structures of the foot.
Clinical signs——–
Foot rot occurs in all ages of cattle, with increased incidences 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 include: • Extreme pain leading to sudden onset of lameness, which increases in severity as the disease progresses. • Acute swelling and redness of interdigital tissues and adjacent coronary band. • Lesions in the interdigital space are often necrotic along its edges and have a characteristic foul odor. • Evenly distributed swelling around both digits and the hairline of the hoof, leading to separation of the claws. • Fever. • Loss of appetite. These lesions are sometimes difficult to see unless the foot is picked up. It can affect both the front and hind limbs. It initially affects a single foot on most occasions. Eventually, the interdigital skin cracks open, revealing a foul-smelling, necrotic, core-like material . If 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. “Super foot rot,” seen in some areas of the country, has received this name due to the rapid progression of symptoms, severity of tissue damage, and lack of response to standard treatments. The standard footbaths have not been effective in preventing the “super foot rot” form of the disease. Veterinary supervision and earlier therapy resulted in a more satisfactory outcome.
Clinical Signs——–
Once F. necrophorum has entered the interdigital space, extensive cellulitis develops. The inflammatory oedema between the claws pushes them apart, stretching the interdigital ligaments and causing considerable pain. The skin between the claws fissures then sloughs. A common complication is septic arthritis of the distal interphalangeal joint.
Signs are usually a sudden onset generalised lameness of varying degree. Animals are usually pyrexic. The affected leg will appear swollen and erythematous and the animal may be noted to be shifting its weight. If chronic, there may also be evidence of disuse atrophy in the affected limb. The animal may have reduced weight gain or weight loss and have a decreased milk yield.
On closer examination of the foot, it will appear hot, moist, erythematous and have a foul odour. There may be skin necrosis and sloughing of the affected area and a purulent discharge may be present. The swelling may have caused the two digits to separate, and the cleft between the claws may appear to be larger than normal.
Diagnosis——–
Diagnosis of foot rot can be made by a thorough examination of the foot, looking at the characteristic signs of sudden onset of lameness (usually in one limb), elevated body temperature, interdigital swelling and separation of the interdigital skin. Other foot conditions causing lameness that may be confused with foot rot are: 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 often involve one claw of the foot only. Swelling attributable to foot rot involves both 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 dew-claws; whereas, foot rot lesions occur in the interdigital area and invade the subcutaneous tissues. Cattle grazing endophyte infected fescue pastures and develop fescue toxicity. This causes loss of blood circulation to the feet and subsequent lameness, sometimes mistaken as having foot rot.
Diagnosis———-
Clinical signs plus physical examination of the foot will lead to a presumptive diagnosis of the disease.
Radiography is not useful in most instances, but is essential in cases failing to respond to treatment and when either septic pedal arthritis or a retroarticular abscess is suspected.
The organism can be isolated and cultured in a laboratory, but this is not usually required for diagnosis.
Exclusion of differential diagnoses such as retroarticular abscessed is important. The characteristic of this condition is that swelling occurs around one digit only, which is different to foot rot. Severe diseases such as Foot and Mouth should also be eliminated, particularly notifiable disease.
Treatment———
Sulphadiazine with trimethoprim (Sulcoprim) 10-15ml i/m for 3 days. Foot bath with 10 ml formalin in 500 ml of water for 15 minutes for 10 days. Damaged sole become normal.
If treated, most cases respond very rapidly, usually with very little after effect. Recurrence will occur occasionally. Natural immunity appears to inhibit reinfection for at least six months.
Suitable antibiotics for treatment of the condition include penicillin G, oxytetracycline, sulfadiazine/trimetroprim, sulfadimethoxine and tylosin. All should be given by injection for three days as topical therapy is not effective. Always follow withdrawal guidelines.
Intravenous infusion via the digital vein with a suitable antibiotic is the most effective way to treat the most advanced cases.
If the skin of the interdigital space has sloughed, topical treatment is also essential. This is particularly important if a secondary lesion appears to be starting in the dorsal region of the interdigital skin. The wound should be cleaned with soapy water, then thoroughly dried and a topical dressing such as an antibiotic paste should be applied. The lesion must then be protected for a few days minimum.
Treatment of foot rot is usually successful, especially when instituted 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. A topical treatment of choice should be applied at that time. Some very mild cases will respond to topical therapy only. Most cases require the use of systemic antimicrobial therapy. A local veterinarian may advise on recommended antibiotics and dosages for each situation. Use of a non-steroidal anti inflammatory may be indicted for pain relief. Affected animals should be kept in dry areas until healed, if possible. If improvement is not evident within three days to four days, it may mean the infection has invaded the deeper tissues. Infections not responding to initial treatments need to be re-evaluated by a veterinarian in a timely manner. A local veterinarian will want to determine if re-cleaning, removing all infected tissue, application of a topical antimicrobial and bandaging are appropriate, along with a change in the antimicrobial regimen.
Prevention ———
Preventive and control of foot rot begins with management of the environment. Prevention of mechanical damage to the foot caused by frozen or dried mud, brush-hogged weeds or brush stubble and gravel is desired. Attempt to minimize the time cattle must spend standing in wet areas. Pens should be scraped and groomed. Areas around ponds, feed bunks and water tanks should be managed to reduce mud and manure. Other preventive measures presently used include footbaths (most often used in confinement beef or dairy operations), addition of organic and in-organic zinc to the feed or mineral mixes and vaccination. Most research trials indicate that average daily gain is increased in grazing cattle by 0.1 lb to 0.3 lb when CTC is included in a free choice mineral mix in grazing cattle. When cattle are moderately to severely deficient in dietary zinc, supplemental zinc may reduce the incidence of foot rot. 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. A three-year study has shown 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 Supplemental iodine has been shown to prevent naturally occurring foot rot in beef cattle (Maas, 1984). Iodine can be supplemented in trace mineral formulations in total mixed rations, salt-mineral mixes for grazing animals, molasses based formulations and other methods. Common supplements include sodium iodide, calcium iodate and EDDI (ethylenediamine dihydriodide; organic iodide) A commercial vaccine approved for use in cattle as a control for foot rot is available in the developed countries like USA but till date it is not available in India.
Control——
Control measures include footbathing of animals with 5% copper sulphate or formalin. Zinc methionine and paraformaldehyde have also been used.
Proprietary vaccines are available but it is, at present, questionable if they are cost effective. Two injections are required one month apart, but the immunity that develops only reduces the incidence of the disease and does not eliminate the risk completely. Vaccinating bulls twice per year is strongly recommended to maintain breeding performance.
The reduction of slurry is also extremely important. Good drainage around drinking and feeding areas is helpful. The isolation of cows (or the use of a protective boot) during the early infectious stages of the disease is strongly recommended. Very early, adequate treatment is essential.
