InterdigitalNecrobacillosis (Footrot) of
Interdigitalnecrobacillosis, or footrotas it is more commonly
known, is an infectious disease of cattle characterized
by acute, painful inflammation of theinterdigital
subcutaneous tissues of the foot. The primary bacterial
agent is Fuso-bacteriumnecrophorum, which may act
synergistically with Bacteroidesmelanino-genicus
and other organisms, but others, such as Bacteriodesnodosus
(the agent which causes ovine footrot) may also be involved.
Clinical signs are usually quite obvious and relate to
the severe pain associated with the condition. The typical
presentation is an acute onset of severe lameness in one
or more limbs, with hind limbs being affected most frequently.
The animal is usually reluctant to put any weight on the
affected leg and usually holds it in a flexed position,
with only the toe touching the ground. This is sometimes
accompanied by a fever of 103-104T, a drop in milk production,
and/or a decreased appetite. Usually the interdigital space
and coronet is swollen, causing the toes to spread apart.
The interdigital space often contains a fissure, with protruding,
necrotic edges. Generally, there is little purulent exudatepresent,
but the lesion has a very characteristic foul odor.
The organisms are thought to enter through abrasions in
the epidermal layer of the foot. Uneven or stony ground
and wet conditions, which soften the skin, predispose to
the condition. F.necrophorum produces a leukocidalexotoxin
which causes a suppurative necrosis of the subcutaneous
tissue. If not treated promptly, the infection may spread
to the adjacent joints or tendon sheaths and may cause septic
arthritis or tenosynovitis.
This is a very commonly diagnosed foot condition, especially
in damp fall and winter weather. A recent study of the
prevalence of various foot diseases in Great
Britain found that footrot
was the seventh most common foot condition in the summer
and the fifth most common in the winter. Dairy breeds are
more susceptible than beef breeds, possibly due to the more
intensive condition under which they are reared. The Zebu
breeds from India
seem to be more resistant than other breeds of cattle. A
zinc deficiency may influence susceptibility, although this
connection has not been scientifically proven.
Diagnosis is usually straightforward and based on clinical signs and the characteristic gross lesions and
odor. Bacterial culture of biopsy material may be helpful
although lesions are often highly contaminated with fecal
flora. Although usually not required for diagnosis,
histopathology reveals a dermatitis and necrosis of the
skin and subcutaneous tissues.
Prompt treatment with parental antibiotics and local care
for the lesion is generally very successful. The organisms
are quite susceptible to most broad spectrum antibiotics.
Ceftiofur sodium (Naxcel®) was approved for treating footrot
in the Fall of 1996 and is now the drug of choice, since
it has no milk or meat withholding time. Procaine penicillin
G,oxytetracycline, and sulfa drugs are also quite effective.
Local treatment is beneficial and involves scrubbing
the affected area. All necrotic tissue should be curetted
away and then the foot should be wrapped with a clean bandage.
A local dressing of copper sulfate or an antibiotic ointment
may be helpful. The bandage should be kept on for several
days if possible.
As in most cases, prevention is the key. One mode of prevention
is to smooth any rough or sharp areas in barnyards, pastures,
or lanes, improve drainage of wet areas, and scrape barnyards
frequently. Another preventive method is the use of a footbath.
It should be of adequate size and depth to completely bathe
each foot. It is recommended that it be 8' long, 2-2.5'
wide, and at least 6" deep. The footbath can be placed
at the exit to the milking parlor or the entrance to the
pasture, so that the cows have to walk through it at least
once weekly. It should be filled with a 10% copper or zinc
sulfate or a 5% formalin solution. Copper and formalin solutions
can be toxic if ingested. The footbath should be changed
frequently to keep it clean. Alternatives to a traditional
footbath (to decrease contamination problems), include
placing a soft, thick rubber mat in the footbath, using
a rinse footbath in front of the medicated one, or using
a 10% mixture of copper sulfate in slaked lime. Feeding
chlortetracycline to feedlot cattle also reduces the prevalence
of footrot. There are commercial vaccines available against
Fusobacteriumnecro-phorum and Bacteriodesnodosus,
but little information regarding their efficacy is available.
In the last several years, a much more serious condition,
known as "super footrot," has been diagnosed on
several occasions. It seems to be caused by a multiple
drug-resistant strain of Fusobacteriumnecrophorum
and causes a more rapidly progressive disease. It also seems
to infect older cows more commonly. "Super footrot"
is a problem to diagnose because it looks just like "regular"
footrot initially. Prompt, aggressive treatment is required
to keep it from infecting the joint. Prevention of "super
footrot" is also a problem, since it can occur on farms
with good hygiene and regular footbathing. Using Ceftiofur
systematically and lincomycin or clindamycin topically
is usually an effective treatment protocol. While footrot
is a common condition in cattle, most cases are highly treatable
and moderately preventable. It usually will not lead to
severe herd problems if treatment is prompt and effective.
Delaying treatment could lead to joint involvement and create
a very serious condition requiring surgical intervention.
- by: Kent L. Wolf, Class of 1998
- edited by: MelissaPopielarczyk,DVM