CONTROL TREATMENT AND ELIMINATION OF FOOT ROT FROM SHEEP
Foot rot
Foot rot, or Infectious pododermatitis, is a hoof infection commonly found in sheep, goats, and cattle.
As the name suggests, it rots away the foot of the animal, more specifically the area between the two toes of the affected animal.
It is extremely painful and contagious.
Affected animal dies of starvation.
It can be treated with a series of medications, but if not treated, the whole herd can become infected.
The cause of the infection in cattle is two species of anaerobic bacteria, Fusobacterium necrophorum and Bacteroides melaninogenicus. Both bacteria are common to the environment in which cattle live, and Fusobacterium is present in the rumen and fecal matter of the cattle.
In sheep, F. necrophorum first invades the interdigital skin following damage to the skin, and causes interdigital lesions and slight inflammation.
The second stage of the disease is marked by the invasion of the foot by the foot rot bacterium Dichelobacter nodosus, a Gram-negative anaerobe.
Usually, an injury to the skin between the hooves allows the bacteria to infect the animal. Another cause of foot rot may be high temperatures or humidity, causing the skin between the hooves to crack and let the bacteria infect the foot. This is one of the reasons foot rot is such a major problem in the summer.
Foot rot is easily identifiable by its appearance and foul odour.
Treatment is usually with an antibiotic medication.
The best curative medication is using “Obcow” liquid as external application & Ceftiofur sodium Inj (parental)
preventing injury to the feet is the best way to prevent foot rot.
OVINE FOOT ROT was first reported in 1869. It is an infectious, contagious disease of sheep that causes severe lameness and economic loss from decreased flock production. With current understanding of the disease, and aided by drugs control and elimination of the disease should be the goal of all sheep producers.
It is caused by an interaction of two anaerobic (without oxygen), Gram (-) bacteria, Bacteroides nodosus (formerly Fusiformis nodosus) and Fusobacterium necrophorum (formerly Sphaerophorus necrophorus).
Fusobacterium necrophorum is a normal inhabitant of the ruminant digestive tract and in wet weather may interact with another bacteria, Corynebacterium pyogenes, to produce foot scald, an infection of the skin between the toes. This infection sets up the foot for invasion by Bacteroides nodosus, which, working in conjunction with the Fusobacterium, produces the condition referred to as foot rot. Since Bacteroides can only live in the hoof of an infected animal or in the soil for no more than 10-14 days, it is possible, through careful management procedures, to keep from introducing foot rot into a flock and to successfully control and/or eliminate the disease if the flock is infected.
Diagnosis
• Lameness is usually the major sign of an infected animal, although sheep with an early infection may not exhibit lameness.
• The area between the toes first becomes moist and reddened.
• Then the infection invades the sole of the hoof, undermining and causing separation of the horny tissues.
• The infection causes a characteristic foul odor and may infect one or more feet at the same time.
Differential Diagnosis : Other diseases that may be confused with foot rot are foot abscesses, foot scald, laminitis or founder, corns, traumatic injuries, and foreign bodies lodged between the toes. Not all lame sheep have foot rot.
Transmission
The bacteria that causes foot rot, Bacteriodes nodosus, is spread from infected sheep to the ground, manure, bedding, etc., where it is then picked up by non infected sheep.
Foot rot is introduced by purchase of an infected animal or
by simply using facilities or trucks that have been contaminated by infected sheep.
Spread occurs best when temperatures are from 40-70° F and the environment is wet.
Since the organism doesn’t survive long in the environment (< 2 wks), carriers in the flock will continue to reinfect the flock unless the animal is either culled or the organism is eliminated by proper treatment.
Prevention
It is always easier and less expensive to prevent foot rot than to treat it after it has become established. To remain disease free, there are five management principles that will help keep foot rot from being introduced into a clean flock.
a. Never buy sheep with foot rot or from a flock infected with foot rot, even if the animal(s) appear unaffected.
b. Avoid buying sheep at sale yards or livestock markets where clean and infected sheep may have been commingled or run through the same area.
c. Avoid using facilities (trails, corrals, dipping areas) where infected sheep may have been in the last two weeks.
d. Never transport sheep in a vehicle that has not been properly cleaned and disinfected.
e. Trim and treat the feet of all new arrivals, then re-examine them periodically during the 30-day isolation period.
Treatment
The control of ovine foot rot is based on several management practices that decrease predisposing factors, and on the treatment and immunization of infected and susceptible sheep. The best results are obtained when several of the following methods are combined.
- Foot trimming: This reduces the number of cracks and crevices where bacteria can hide, removes infected hoof, and exposes the organism to air and various medications. All affected tissue should be trimmed away. Many times, this involves removing a large portion of the hoof wall as well as the overgrown portion. This is necessary if the medication and oxygen are to reach the bacteria and kill them. Foot trimming should be done at least one to two times per year as a part of normal management practices, and more often in conjunction with footbaths in the control of foot rot. When trimming feet, it is important to disinfect the trimming instruments (foot shear, hoof parer, or knife) between animals to prevent spreading of the infection. During a severe outbreak, trimming without any other treatment may actually increase the severity of the disease.
- Footbaths/Footsoaks: There are two different types of solutions commonly used in foot baths: zinc sulfate and copper sulfate. For treatment, they should be used 1-2 times per week for several weeks. They may also be used routinely after foot trimming and as a preventative.
a. Zinc sulfate (10% solution) is perhaps the most effective and least toxic of the two baths. Tag wool should be added to all the solutions to reduce splashing and wastage and to discourage consumption by the animal as it stands in the solution. A surfactant or wetting agent (detergent) can also be added to the baths to increase their penetration into the cracks and crevices of the hoof. Use of zinc sulfate or copper sulfate solutions as a foot soak
(30-60 minutes of contact) increases their efficacy in a treatment program. When designing the foot bath area, it is important that length of contact with the solution be kept in mind. Sufficient sized baths/soaks are necessary to handle the flock and allow sufficient contact time with the solution.
b. Copper sulfate (bluestone) solutions (10% solution) are also useful but are toxic if consumed by the sheep. Hot water helps dissolve it, as does the addition of some vinegar. It is very corrosive so it should not be used in metal foot baths. It also stains the wool.
- Dry chemicals: Zinc sulfate (dry) can be placed in a box in an area sheep must walk through. This will not treat infected animals, but will help decrease the spread of the disease. Lime, disinfectants, or drying agents may be used around feed or water troughs to reduce moisture and decrease the spread of the disease.
- Oral therapy: Zinc sulfate at the rate of 1/2 (0.5) gram per day for 21 days may be helpful both in treatment and prevention, especially if the diet is zinc- deficient.
- High levels of certain antibiotics may also be helpful in some situations but should only be used after consultation with a veterinarian.
- Injection of antibiotics: Use of Penicillin and streptomycin combinations or Procaine Penicillin G or long-acting penicillin products or Single injections of long-acting tetracycline have also been successful in some cases. Use of any of these should be after consultation with a veterinarian.
- Topical medications: There are several different medications that can be applied to the hoof immediately after paring that are helpful in controlling foot rot.
Vaccination:
Though not available in India, vaccines for Bacteroides nodosus are available in the U.S. with 60-80 percent success.
The vaccine works not only as a preventative but has been shown to be fairly effective as a treatment.
A regimen of two vaccinations given subcutaneously on the neck just behind the ear 4-6 weeks apart is used.
Vaccination before the start of the wet season is recommended, followed by a booster each year prior to the wet season if eradication efforts have not been successful.
Abscesses are common at the injection site but should not be treated.
These abscess usually break and drain on their own with no ill effects to the sheep.
For this reason, vaccination of show animals or animals that may be going to slaughter soon may not be practical.
Eradication
Using combinations of these procedures, foot rot can be eradicated. Eradication is difficult and requires commitment but is possible using combinations of these treatment programs. It is also apparent from the following studies that no single treatment is effective. It must be a combination of the ones that best fit the facilities, management, and financial limitations of the flock owner/manager.
The essentials of the eradication program are
a. the willpower to cull chronically affected sheep and those that do not respond to vaccination, antibiotics, foot trimming, and footsoaks/baths.
b. a clean pasture or lot (no sheep with foot rot on it for more than 2 weeks minimum) to place clean animals on, and adequate fencing to assure that separation of clean and infected flocks is maintained.
c. Any lame sheep in the clean group should be immediately examined or put in the “dirty” flock to prevent contamination of the clean flock.
Recent research points out that some sheep seem to be more resistant to foot rot than others. Ewe lambs should not be saved from ewes that have a history of repeat occurrences of the disease.
Summary
Foot rot is a costly disease to the sheep industry. Treatment costs of labor, drugs and equipment, decreased flock productivity, losses from sales of breeding stock, etc., make this disease an economic hardship for producers. But, with current technology, it is possible and practical to eradicate the disease.
Compiled by :
Dr.Ashok Kumar Valupadasu
Asst.Director (V&AHD) Telangana
8500404016 / grass2meat@gmail.com
