The limb joints of animals are
designed for mobility. In conjunction with the muscles
and tendons, the joints allow for flexion and extension
of the legs and permit a wide range of motion and
activity. Normal joint function is essential for good
health, particularly in grazing animals such as goats
which may have to cover large areas over varying terrain
in search of food. Normal joint function also allows
flight from predators and is important for breeding
success in active bucks. In addition, lameness or
swellings over joints may reduce an animal's chances
in the show ring.
2. Normal limb joints are comprised
of several structures. First are the bone ends, covered
with cartilage and shaped to interlock for increased
stability. The cartilage is quite smooth, for reducing
friction and wear in the joint. A space exists between
the cartilage surfaces called the joint cavity. This
space is filled with joint (or synovial) fluid which
lubricates the joint and acts as a shock absorber
to reduce the trauma associated with movement. The
fluid is held in place by a fibrous joint capsule
which is lined with a synovial membrane that produces
the joint fluid. Outside the joint capsule are numerous
ligaments, muscles and tendons which add further strength
and stability to the joint. The tendons are also surrounded
by sheaths containing fluid known as bursae. Inflammation
of the tendon sheaths is known as bursitis. Inflammation
of the joint from any cause is known as arthritis.
Any or all of the structures comprising the joint
may be damaged in arthritic conditions.
3. Recognizing Joint Disease
Arthritis may result from a variety of infectious
and noninfectious causes. A single joint may be affected
or multiple joints involved (polyarthritis). Depending
on the cause, signs of arthritis may vary. For example,
in bacterial or traumatic arthritis, the affected
joint may be swollen and warm to the touch. In early
viral or nutritional arthritis, no visible change
may be detected in the joint. In these cases, the
presence of arthritis is suggested by observation
of signs such as reluctance or difficulty in rising,
slowed return to the barn at milking time, inability
of bucks to mount does at breeding time, limping or
uneven gait, or complete disuse of a single limb.
Even when these signs are noted, other conditions
which might result in abnormal motion should be considered.
These would include fractures, laminitis or founder,
foot rot, and white muscle disease (vitamin E/selenium
deficiency). In addition, various neurological problems
may be misinterpreted as musculoskeletal disease.
4. Several diagnostic procedures
may be employed to identify the cause of arthritis.
Examination of the joint fluid obtained by aseptically
tapping the joint may be useful. Large numbers of
neutrophils in the fluid are suggestive of bacterial
arthritis. Large numbers of mononuclear cells are
more indicative of viral arthritis. Little change
in the fluid composition may be observed in traumatic
or nutritional arthritis. In the case of bacterial
arthritis, joint fluid may be cultured to identify
the causative organism and to select the appropriate
antibiotic therapy.
5. In cases of nutritional or traumatic
arthritis, radiographs may be helpful in establishing
a diagnosis and prognosis for recovery. Serological
testing may be required for the diagnosis of arthritis
due to virus or mycoplasma. Successful treatment of
individual cases of arthritis and control and prevention
of additional cases depends on accurate and specific
diagnosis.
6. Specific Causes of Caprine Arthritis
Bacterial Arthritis -- Lacerations or puncture wounds
over joints can lead to bacterial infection. Injuries
such as these should be cared for immediately. The
affected area should be cared for immediately. The
affected area should be cleaned thoroughly with soap
and water. If the joint has been opened, suturing
may be indicated. Antibiotic therapy should be initiated
to prevent infection.
7. In young kids, bacterial polyarthritis
can occur. The organisms involved are usually E. coli,
Corynebacterium pyogenes, or staphylococci. The condition
is recognized by lameness and swelling in one or more
joints, particularly the front knees (carpi), hocks
and stifles. This condition is secondary to bacterial
infection elsewhere in the body, usually the navel
or digestive tract. The bacteria are carried to the
joints via the bloodstream. Therapy is often ineffective
and prevention is the preferred method of control.
Unclean environment and improper kid care promote
the incidence of polyarthritis. Improved management
practices will reduce the occurrence of this disease.
Maternity pens should be used for kidding, and kept
clean and dry with bedding changed between births.
Navels of newborns should be dipped in iodine immediately
after birth. Kids should receive adequate colostrum
within six hours after kidding. They should be housed
in warm, dry quarters, and not overcrowded.
8. Mycoplasma Arthritis -- Mycoplasmas
are small microorganisms which differ from bacteria
in that they do not have a cell wall. They are difficult
to culture in the laboratory and much confusion exits
with regard to the species of mycoplasma responsible
for caprine arthritis in the United States. Several
species of goat mycoplasmas are known in the US but
Mycoplasma mycoides subspecies mycoides, large colony
type, appears to be most responsible for cases of
mycoplasmal arthritis. The prevalence and distribution
of caprine mycoplasma arthritis is unclear, and sporadic
reports from several regions of the US have appeared
in the veterinary literature, most notably from California.
9. Mycoplasma infection produces
a severe systematic disease in which arthritis may
be the only sign or may be accompanied by high fevers,
inappetence, pneumonia, diarrhea, keratoconjunctivitis
(pink eye), or sudden death. All animals in a herd
may be affected, but the more dramatic signs are seen
in kids and younger adults. Outbreaks are often preceded
by some stress such as dehorning. The infection may
be carried unnoticed in a herd for extended periods.
10. Whenever several animals in a
group are suddenly affected with arthritis along with
signs of illness elsewhere in the body, mycoplasma
should be suspected. Any dead animals should be submitted
to a diagnostic laboratory for specific diagnosis.
Blood samples from living animals should also be taken
for evaluation of titers to mycoplasma infection.
Correct diagnosis is important since few antibiotics
are effective against mycoplasma. Tylosin and tetracyclines
may be useful in controlling herd outbreaks although
losses may be high.
11. Viral Arthritis -- (CAE) A recently
discovered retrovirus has been identified as a cause
of chronic arthritis in goats. It is very likely that
many previously unexplained cases of caprine arthritis
were the result of this slow virus infection. The
caprine arthritis encaphalitis virus (CAEV) was first
recognized as a cause of progressive paralysis in
two of four month old kids resulting from infection
of the brain (encephalitis). Later it was demonstrated
that the same virus also produces a progressive chronic
arthritis in older goats. The presence of this virus
in the US goat production is believed to be very high.
12. Nutritional Arthritis -- One
specific syndrome of arthritis related to feeding
deserves mention. It involves the excessive consumption
of calcium in the ration by mature bucks. Lactating
does and young growing animals may require supplemental
calcium in the diet. However, mature bucks fed in
similar ration are likely to develop arthritis due
to excessive deposition of calcium in the bone (osteopetrosis).
Proliferative calcification (osteophytes) forming
on the margin of joints disrupts normal joint architecture
and may impair mobility and breeding effectiveness.
Osteophytes may be visible radiographically. To prevent
this problem, mature bucks should be fed either grass
hay or not more than two pounds of alfalfa hay daily.
13. Traumatic Arthritis -- Because
goats are prone to fighting, traumatic joint injuries
(sprains, dislocations, torn ligaments) are not uncommon.
Sudden lameness and swelling of a single joint without
fever is suggestive of traumatic injury. Affected
goats should be isolated and confined with exercise
restricted. The joint may be wrapped with an elastic
bandage and cold compresses applied to minimize swelling.
The animal may be placed on aspirin to reduce pain
and inflammation. The degree of recovery is dependent
on the extent of the injury.
14. Other Causes of Arthritis --
Herd outbreaks of polyarthritis in lambs due to Chlamydia
sp., a virus-like organism, are known to occur in
the United States. It has been suggested that chlamydial
arthritis in goats also occurs, especially in herds
which have experienced outbreaks of chlamydial abortion.
As interest in and recognition ofcaprine diseases
continues to develop in the United States, chlamydia
as well as other organisms may be identified as causes
of arthritis in goats.
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