Draxxin Treatment and Dosages for Sheep

Ovine foot rot is a costly disease in the sheep industry, with producers losing time and money each year in their attempts to control this condition in their flocks. When foot rot becomes a problem on a farm, it takes a great deal of effort to control symptoms and eliminate it. Foot rot is a preventable disease however, that can be controlled with attentive management.

First reported in 1869, ovine foot rot is caused by the coexistence of two gram-negative, anaerobic bacteria, Fusobacterium necrophorum and Dichelobacter nodosus (also referred to as Bacteroides nodosus). Several different strains of D. nodosus can affect both sheep and goats, and can also be carried by cattle, deer, and horses. In general, sheep are affected more severely than goats. The bacteria Fusobacterium necrophorum also causes a common disease known as foot scald.¹ F. necrophorum is a natural inhabitant of the large intestine of small ruminants and is ubiquitous in the soil and manure of pastures or feedlots. Infection is often exacerbated by cold, wet conditions where mud and manure have been allowed to accumulate. The mud and manure causes interdigital irritation, and F. necrophorum readily infects the soft, irritated area. Alone, this bacterium is not capable of causing foot rot.² Dichelobacter nodosus is only capable of living in soil for 10 to 14 days, yet it can survive in the hoof for extended time periods given the right anaerobic environment.¹ These bacteria require irritation of the interdigital area, possibly due to moisture or trauma, in order to gain entry for infection. Hard frozen ground (as is found in dry lots) can cause irritation to the soft tissue, and create ideal conditions for foot rot when the ground warms to mud.² Foot rot is most prevalent and more contagious in wet, moist areas. When pastures have been consistently wet with no dry spells, there is a higher incidence of outbreaks.

In most bacterial cases of foot rot, the bacteria is spread from infected sheep to the ground, manure or bedding, where it is then picked up by noninfected sheep. Often, it is introduced by the purchase of an infected animal or by using facilities or trucks that have been contaminated by infected sheep. Since the organism doesn't survive long in the environment, carriers in the flock will continue to reinfect other animals unless the sheep is either culled or the organism is eliminated via treatment.

Symptoms of Ovine Foot Rot

Lameness is usually the first indication of an infected animal, although sheep with early infections 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.³ Foot scald and foot rot can also result in reduced weight gain, decreased milk and wool production, and decreased reproductive capabilities as severely infected animals are reluctant to move in order to feed. Affected animals often carry the affected leg or lie down for extended periods, rubbing off the wool/hair on their flanks, brisket, and knees. These conditions result in production losses, treatment and prevention costs, premature culling, and reduced sale value of infected animals.¹

Not all lame sheep will have clinical cases of foot rot, so it is best to consult a veterinarian for a positive diagnosis before undertaking an eradication, treatment, or control program. Other diseases that may be confused with foot rot include abscesses, foot scald, laminitis or founder, corns, traumatic injuries, and foreign bodies lodged between the toes.

Prevention of Foot Rot

While not always possible, it is easier and less expensive to prevent foot rot than to treat it after it has become established. For an establishment to remain disease free, there are several management principles that help to keep foot rot from being introduced into a clean flock.

• Avoid buying sheep from an establishment with foot rot, even if individual animals appear unaffected.
• Avoid buying sheep at sale yards or livestock markets where clean and infected sheep may have been commingled.
• Avoid using facilities where infected sheep may have been within the previous two weeks.
• Do not transport sheep in vehicles that have not been properly cleaned and disinfected.
• Clean, trim and treat the feet of all new arrivals and isolate for 30 days.

Treatment of Foot Rot

The control of ovine foot rot is based on several management practices that decrease predisposing factors. The best results have been reported where several of the following methods are implemented.

Foot trimming: Reduces the number of cracks and crevices where bacteria can hide, removes infected hoof, and exposes organisms to air.

Footbaths and soaks: 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.

Dry chemicals: Dry zinc sulfate can be placed in a box in an area sheep must walk through. This does not treat infected animals, but can help decrease the spread of the disease.

Topical medications: Several medications have been used that can be applied to the hoof immediately after paring which are helpful in controlling foot rot

• Zinc sulfate
• Copper sulfate
• Copper sulfate in pine tar
• Oxytetracycline solution in alcohol
• Penicillin in alcohol

Vaccination: Vaccines for B. nodosus are approved for use in the U.S. They may range in effectiveness from 0-100 percent; most users report from 60-80 percent success.

Antibiotics: Penicillin and streptomycin combinations used either as a single treatment or daily for up to ten days has been effective in treating foot rot. Procaine Penicillin G or long-acting penicillin products at the same dosage may also be effective. Single injections of long-acting tetracycline have also been successful in some cases.²

Draxxin^® injectable solution is indicated for the treatment of ovine foot rot associated with B. nodosus when systemic treatment is required due to the presence of active lesions. Draxxin^® is a branded form of tulathromycin, a macrolide antibiotic that is indicated for the treatment of BRD associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni (Haemophilus somnus), and Mycoplasma bovis in beef and non-lactating dairy cattle.⁴

For the treatment of foot rot in sheep, the manufacturer recommends a single dose of 2.5 mg/kg body weight (0.25 mL/10 kg), inject intramuscularly in the neck. They also note that foot rot in sheep is a multifactorial disease process (see “Treatment of Foot Rot” above) for which there are no unique approaches for prevention and treatment. Draxxin^® should be used as part of a whole flock management program which may also include environmental management, such as providing a dry environment.⁵ Treated animals must not be slaughtered for use as food for at least 44 days in cattle, 8 days in swine and 16 days in sheep after the latest treatment with Draxxin^®.