Caprine Arthritis Encephalitis

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					                   Caprine Arthritis Encephalitis


With the recent growing interest in the importation of Boer goats,
and Boer goat frozen semen and embryos from New Zealand,
there have been some concerns about the potential risk of
introducing diseases into the US got population. New Zealand is
considered free of foot-and-mouth disease, rinderpest, scrapie,
contagious caprine pleuropneumonia, Akabane, bluetongue,
epizootic hemorrhagic disease, and Brucella
melitensis. New Zealand is not free of caprine arthritis encephalitis
(CAE), but this disease is limited to some areas. However, the real
threat of CAE for the Boer goat industry is that some producers are
considering using dairy oats as recipients for the Boer goat
embryos. The prevalence of CAE in US dairy goats is high
(between 40 and 80%).
Therefore, the use of dairy goats as recipients in an embryo
transfer program represents arisk of spreading CAE.
Limited serological surveys indicate that for the most past Spanish
and Angora goats in West Texas are free of CAE. It is very
important to maintain the new Boer goat population free of CAE.
As a general rule, all recipient goats (whether dairy or meat/hair
goats) in an embryo transfer program should test negative for
CAE. The purposed of the present report is to describe some of
the characteristics of CAE as well as the ways to prevent this
disease.
Etiology and Transmission
Caprine arthritis encephalitis is an infectious disease of goats
caused by a virus called caprine arthritis encephalitis virus CAEV).
This virus belongs to the family lentivirus (lenti means slow), and
they are so called because they produce slow progressive
diseases. Capring arthritis encephalitis virus is very similar to the
virus that causes ovine progressive pneumonia (OPP) in sheep,
and some of the disease conditions that these two viruses cause
are alike. In fact, sheep are susceptible to infection by CAEV and
goats are susceptible to OPP virus.
Transmission of CAEV occurs mostly through the milk and
colustrum of infected mothers to nursing kid goats. Contact
between infected and non-infected animals is also an important
way of CAE transmission. Intrauterine transmission to the fetus
can also occur but is less common. These are the reasons why it
is very important that does that are going to be used as recipients
are free of CAE. If frozen embryos free of CAE are implanted in
infected recipient goats, the offspring resulting from these embryos
can acquire the infection. Caprine arthritis encephalitis has a major
impact on lifetime productivity of goats and on the eligibility of the
United States to export goats.
Signs of the Disease
There are two main forms in which CAE can be manifested. In
young kids 2-6 months of age, the disease is characterized by rear
leg paralysis that progresses and eventually
involves also the front legs. Most kids affected by this form of CAE
eat normally, have normal rectal temperatures and are alert. The
paralytic form of the disease is uncommon but needs to be
differentiated from other causes of paralysis, such as copper
deficiency,white muscle disease, bacterial arthritis, or spinal cord
injury.
The most common form of the disease is arthritis in adult goats.
The onset of this form ofthe disease is insidious, with affected
animals having bouts of joint swelling followed by apparent
recovery. The joint enlargement is due in part to increased joint
fluid, but generally results from formation of a chronic fibrous
inflammatory tissue inside the joints and around the tendons
associated with the affected joints. The carpal joints are usually the
first to be affected, followed by the stifle, hock, tarsus and hip. The
affected joints are painful and have restricted movement. Goats
with arthritis are reluctant to walk, remain prostrated or walk on
their knees. Other causes of arthritis in goats, such as chlamydial
polyarthritis and mycoplasmosis, need to be included in the
differential diagnosis. Most does affected by the arthritic form also
develop chronic inflammation of the mammary gland (hard bag),
with decreased or total suppression of milk production. In addition,
some goats develop chronic interstitial pneumonia in conjunction
with or independently of the joint and mammary land involvement.
Goats affected by the respiratory form have difficulty breathing and
weight loss. This form of the disease needs to be differentiatedn
from other types of chronic pneumonia, including lung abscesses,
chronic pasteurellosis and parasitic pneumonia.
Diagnosis and Identification of Infected Animals
Infected animals remain infected for life. The great majority of
infected animals do not manifest signs of disease, but they may be
the source of virus for non-infected goats. The agargel
immunodiffusion (AGID) test is the most common way to identify
infected animals. his test is easy to perform, relatively cheap and
fast. However, the sensitivity of this test is low and a large
proportion of infected animals (up to 40%), mostly those in the
initial phases of the infection, will not be detected. A more
expensive test to detect infected animals is the ELISA test. In
general, this test is more sensitive than AGID, and as many as
90% of the affected animals can be detected by ELISA, although
the range of detection may vary between laboratories. Additional
studies are needed to determine the efficiency of the ELISA test to
detect CAE-infected animals. Because there is a chance of
missing infected animals, retesting every 3-6 months is
recommended.

Prevention and Control
Thee is no treatment for CAE. All animals that result positive to
CAE need to be isolated from the rest of the flock. Alternatively,
offspring from infected goats need to be removed from the does
immediately after birth and before ingesting colostrums. These
kids need to be given colostrums from non-infected does,
pasteurized colustrum or bovine colustrum within the first hour
after birth and then bottle-fed with non-infected milk or milk
replacer until weaning.

				
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posted:9/15/2011
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