Also, know as Foul in the foot — Infectious Pododermatitis — Interdigital Necrobacillosis — Interdigital Phlegmon — HoofRot — Footrot.
Interdigital phlegmon is an infectious claw disease that can affect individual animals sporadically or can cause whole herd outbreaks. Due to its severe economic consequences, rapid diagnosis and treatment of IP should be a high priority for farmers and veterinarians. Immediate and appropriate treatment and consistent prevention can stop the infection and reduce economic losses on farms.
Footrot 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.
Footrot in cattle should not be confused with Footrot in sheep. The two diseases are different and cross infection between the two species is not believed to occur. Foo trot in sheep requires not only a virulent strain of Dichelobacter nodosusto be present, but also Fusobacterium necrophorum.
Footrot is a subacute or acute necrotic infection that originates in the interdigital skin, leading to cellulitis in the digital region. Footrot has a worldwide distribution and is usually sporadic. It may be endemic in intensive beef units or in cattle at pasture. The incidence varies according to weather, a season of the year, grazing periods, and housing system. Footrot is presented less commonly today than decades ago, partly because more cases are treated by farmers and partly because dairy cows spend much less time at pasture. However, on average, footrot accounts for up to 15% of foot diseases.
The appearance of footrot in loose housing systems has been reported.
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Etiology and Pathogenesis:-
Injury to the interdigital skin provides a portal of entry for infection. Maceration of the skin by water, feces, and urine may predispose to injuries. Fusobacterium necrophorum is considered the major cause of footrot. It can be isolated from feces, in which it may survive as a saprophyte, which may explain why control is difficult. It can also survive in moist soil. F necrophorum is a gram-negative, nonspore-forming, nonflagellated, nonmotile, pleomorphic anaerobic bacteria.
It has a lipopolysaccharide endotoxin capable of necrotizing activity. There are three subspecies and a number of genotypes, each of which targets different tissues. When PCR assays become more widely available, the genotypes will be more readily identifiable. Other organisms, such as Dichelobacter nodosus, Staphylococcus aureus, Escherichia coli, Trueperella pyogenes, and possibly Bacteroides melaninogenicus can also be involved.
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Cases are usually sporadic but occasionally morbidity is high within a herd. Cattle of all ages, sexes, and breeds are affected. Incidence is higher in winter and in cattle that are confined.
Various predisposing factors favor the growth of infectious agents and lead to the development of a clinical case of IP.
The most important preconditions are:-
1. Inappropriate housing:-
High humidity, high temperature (bacterial reproduction rate increases above 10 °C), and rough floors in cubicles, walkways and loading areas can cause softening of, and damage to, the hoof horn or cracking of the skin in the interdigital area.
2.Level of claw care:-
Overgrown or misshapen claws and unprofessional trimming (e.g. low heel height) may induce the formation of micro-cracks in the skin in the interdigital area.
3.General health status of the animals:-
Metabolic disorders (SARA, ketosis, clinical or sub-clinical hypocalcemia, etc.), can lead to an impaired immune response. This makes animals more susceptible to infections such as IP. Nutrient deficiencies, for example, deficiencies in vitamin A or zinc, may cause poor horn quality.
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Lesions to the hoof and interdigital skin are frequently observed in high yielding dairy cattle.
DeFRAIN et al. (2013) reported that IP was diagnosed most frequently in the first 60 days post partum
(approximately 40% of IP events) which can be explained by immunosuppression and a negative energy balance
during this period.
Cows in their first lactation had the highest risk of IP (1.9%) and the second lactation cows the lowest (0.9%) according to ALBAN et al. (1995).
7.Association between the incidence of IP and other causes of lameness:-
A further important risk factor, often associated with those mentioned above, may be heat stress Heat stress increases the animals’ breathing and heart rate decreases the immune response and alters the cows’ behavior. Cows will stand for longer to dissipate heat, which promotes pooling of blood in the digits. Additionally, heat stress causes a reduction in feed intake.
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.
Interdigital phlegmon (footrot):-
Research suggests that the incubation period of footrot can be a week. The fore- or, more commonly, the hindlimbs can be affected, but more than one foot is rarely involved at the same time in mature cows. However, footrot can occasionally develop in several feet in calves. The first sign is swelling and erythema of the soft tissues of the interdigital space and the adjacent coronary band.
The inflammation extends to the pastern and fetlock. Typically, the claws are markedly separated, and the inflammatory edema is uniformly distributed between the two digits. The onset of the disease is rapid, and the extreme pain leads to increasing lameness. In severe cases, the animal is reluctant to bear weight on the affected foot. Fever and anorexia are seen. The skin of the interdigital space first appears discolored; later, it fragments with exudate production. As necrosis of the skin progresses, sloughing of tissue is likely to follow. A characteristic foul odor is produced.
If the disease proceeds unchecked, weight loss is severe and milk yield is significantly reduced. Milk production may not recover during the current lactation. Open lesions can be infected with secondary invaders. If the necrotic lesion is located in the anterior region of the interdigital space, the distal interphalangeal joint can become infected.
Hematogenous infection of the tissues of the interdigital space may account for peracute cases of footrot, which are referred to as either “blind” or “super foul.” This form of footrot is characterized by the initial absence of a skin lesion, extreme pain, and the tendency to progress despite aggressive therapy.
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Responds well if treated early with penicillin, tetracycline, sulfonamides, or ceftiofur sodium (Naxcel), the drug of choice for lactating dairy cows. Interdigital injection of penicillin/steroid combination may be of value. Should perform a thorough cleaning of the interdigital space and local debridement of necrotic tissue if necessary.
Bandaging with sulfa creme or sulfa powder with copper sulfate may be necessary. Bandaging helps prevent discharge of an abundance of organisms that contaminate the environment and also protects the foot from deeper infection if the epidermis is lost. It not treated early, septic arthritis, tenosynovitis, abscessation, or fibrotic digital swelling can occur.
Most treated animals recover in a few days. Good results are obtained with penicillin G, IM, for 3 days. Treatment should be administered as soon as signs are observed. However, the label dosage may be inadequate to effect a rapid resolution, and increased dosages may be needed, requiring increased withdrawal times. Treatment of “super foul” must be particularly aggressive. Early cases respond well to single doses of long-acting oxytetracycline.
Sodium sulfadimidine solution IV or trimethoprim/sulfadoxine, IV or IM, bid for 3 days, can also be used. A single oral administration of a long-acting bolus containing baquiloprim/sulfadimidine may be suitable to treat beef cattle.
High concentration of an agent in the target tissues can be achieved by a regional IV injection. Positive results have been obtained with penicillin or oxytetracycline.
Local treatment is essential for some longstanding cases and in all instances in which the anterior region of the interdigital space has been compromised. The lesion must be thoroughly cleansed, but it is inadvisable to curette or otherwise remove necrotic tissue surgically. The dorsal pouch of the distal phalangeal joint is very superficial at this point. A nonirritant bacteriostatic agent (such as nitrofurazone or a sulfa preparation) should be applied as a topical dressing. The application of gauze, cotton batting, or bandages is contraindicated.
However, the lesion can be protected and immobilized by binding the digits together with a bandage. The entire digital region can be protected from contamination if it is enclosed in a plastic bag fixed in place with an adhesive bandage. However, prolonged protection is not advocated, because the enclosed lesion tends to macerate further. Bandages, if used, should be replaced daily.
Prevention and Control:-
Animals actively shedding infectious organisms should be isolated until signs of lameness have disappeared. If this is not possible, a waterproof dressing or protective boot should be applied; however, animals wearing protective boots should be monitored carefully to avoid additional damage. Boots should be disinfected between use.
Because busy traffic areas are invariably heavily contaminated, steps should be taken to ensure that areas around drinking troughs, gateways, and tracks are adequately drained. Animals at pasture might be moved to a clean, dry area, or possibly housed during periods of heavy rainfall. Contaminated concrete must be frequently cleaned and scraped free of manure.
Preventive use of a footbath with an antiseptic and astringent solution (eg, copper or zinc sulfate [7%–10% in water]) has given beneficial results. Formaldehyde solution (3%–5% in water) can also be used. Ethylenediamine dihydroiodide has been used as a feed supplement for prevention, but the results are extremely uncertain.
Vaccines against F necrophorum have failed because of the weak immune response to the bacterium. High levels of zinc fed as a supplement have a beneficial effect by improving epidermal resistance to bacterial invaders.
Control measures include footbathing of animals with 5% copper sulfate or formalin. Zinc methionine and paraformaldehyde have also been used.
Compiled & shared by-
DR RAJESH KUMAR SINGH