Brucellosis
Caseous Lymphadenitis (CL)
Caprine Arthritis Encephalitis (CAE)
Ovine Progressive Pneumonia (OPP)
Paratuberculosis (Johne's Disease)
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Brucella Ovis is a disease affecting breeding rams. The most obvious symptoms are swelling and hardness of the testicles associated with orchitis. Other palpable abnormalities in the epididymis and accessory sex glands are also detectable. The disease results in reduced fertility, prolonged lambing season, increased number of barren ewes, and excessive costs to replace infected rams. The disease is transmitted primarily through homosexual activity among rams in common housing. Identification and removal of infected animals is the most effective strategy for eliminating this disease. All breeding rams should be evaluated for presence of the disease on a regular basis. Palpation and culture is less effective than ELISA testing. Once a herd has been freed of this disease, a producer should purchase animals only from flocks that are proven negative by ELISA. PAVL offers a highly sensitive ELISA for the detection of antibodies to B.ovis in rams. |
| Caseous Lymphadenitis (CL) is a disease common to many species
but is of particular significance to sheep and goats. This bacterial
infection, which is also known as infectious abcesses, is caused
by Corynebacterium pseudotuberculosis. Abscess of superficial
lymph nodes is the most obvious clinical symptom. However, visceral
nodes and organs such as the lungs, liver, kidneys, and spleen may also
be involved.
Animals gradually become emaciated and lose reproductive efficiency. The economic impact of this disease may be through reduced wool production in sheep or reduced milk production in dairy goats. Economic losses may also occur through carcass trimming and condemnation at slaughter, reduced body weight, and reduced value of goat hides. Animals from infected herds may also have lower value as a replacement stock. This will be important as certification programs for disease free flocks and herds are developed. In sheep transmission of this disease occurs primarily through contamination of wounds at shearing time or when injuries are incurred around water and feed troughs. In goats oral contamination (licking) leads to infected lymph nodes in the jaw and neck area. An effective vaccine is now available for sheep but not for goats. Since vaccinated sheep cannot be differentiated from infected animals, sheep should be tested prior to vaccination and the flock divided into positive and negative units. All new additions to the flock/herd should be tested before vaccination in order to minimize the risk of contamination by an infected by asymptomatic animal. The ELISA available through PAVL detects antibodies specific for the cell wall of the causative bacteria as well as the toxin which this bacteria produces. This test has proven to be both sensitive and effective in the early detection of CL for both sheep and goats. |
| Caprine Arthritis Encephalitis (CAE) is a disease of goats caused
by a retrovirus which is closely related to the OPP virus of sheep.
As in sheep, there is no known cure. Clinically infected goats often
develop arthritis of the knees resulting in swollen, painful joints.
Young goats may also exhibit a neurological syndrome consisting of progressive
paralysis and other symptoms of brain involvement. It is important
to note that many infected goats never show significant symptoms.
Although these "carrier" animals remain asymptomatic, they are a source
of infection for other goats in the herd.
The economic effects of CAE in goat herds are loss of up to 25-30% in milk production, early culling, a shorter life span and reduced growth of offspring The primary source of infection is through the colostrum and milk. Rarely direct transmission can occur through animal contact. In utero infection (i.e. doe to unborn kid) is not common. Since a vaccine is not available, identification of positive animals followed by isolation and/or culling is the most effective method to control spread of the disease. Additionally, heat treatment of colostrum and milk to kill virus has been used extensively to break the cycle of doe to kid infection. Control programs should include testing the entire herd every six months until 2 consecutive negative tests are achieved. Subsequently, annual herd testing should be performed to prevent re infection of the herd. Any new additions to the herd should be tested and found negative, or come from herds that are proven to be free of CAE. The PAVL ELISA test for CAE utilizes 2 detection antigens for increased sensitivity. The first antigen is a recombinant protein developed at the U.S. Meat Animal Research Center which is particularly suited for detecting recently infected animals. The second is a synthetic peptide antigen developed in conjunction with research done at the Pasteur Institute, Paris, France. This antigen provides the best sensitivity for chronic infection and is a good predictor for which animals will develop arthritis. In addition to the blood test for CAE, PAVL is able to test colostrum samples for CAE. The high concentration of antibodies in colostrum increases the detection capability of the test and makes sample collection very convenient. |
| Ovine Progressive Pneumonia (OPP) is a disease of sheep caused
by a retrovirus. Many retroviruses suppress the immune system, pre-disposing
the animal to secondary infections; and once infected, there is no known
cure.
Clinical symptoms appear slowly and are more commonly reported in older sheep (3-4 years old). The symptoms include progressive emaciation, labored breathing, predisposition to secondary bacterial pneumonia, indurative mastitis (hardbag), and arthritis. Economic effects of this disease in sheep are reduced productivity arising from early culling, a shorter life span and reduced growth of offspring. The primary method of infection is through the colostrum and milk, although direct transmission can occur when animals are kept in close confinement. It is important to note that in utero infection (ewe to unborn lamb) is rare. Since there is no vaccine for OPP, most breeders depend on identification and isolation of infected animals. Lambs of infected animals may be isolated before nursing and bottle fed non-infectious milk. The American Association of Small Ruminant Practitioners recommends testing lambs at six month intervals followed by culling or segregation of positive animals. Any new additions to the flock should also be tested and found negative, or come from flocks that are proven negative of this disease. An ELISA test for OPP is now available through PAVL for routine testing or flock clean-up programs. |
| Paratuberculosis (Johne's Disease) is a disease common to all ruminanats.
The etiologic agent, Mycobacterium paratuberculosis, localizes in the
small intestine. As the disease progresses, the lining of the small
intestine and large intestine becomes thickened and the animal is unable
to absorb nutrients. The feces may lose their characteristic pellet
appearance and become pasty or softer than normal. Depression and
labored breathing in goats and shedding of wool in sheep are other symptoms.
Affected animals often succumb to other bacterial and viral infections.
Johne's disease may be transmitted in utero, by ingestion of milk or colostrum from infected animals, or by ingestion of contaminated water or feed. Very young animals are most susceptible to infection. Intervention strategies should include identification and segregation of infected animals to prevent contamination of clean areas, especially the lambing or kidding areas. The separation of offspring at birth is not effective in controlling the disease. Offspring from infected animals should not be retained for breeding or sold for replacements. Flock/herd management is essential to reduce or to eradicate infection with Johne's disease. Johne's disease has a very long incubation period. Infection may occur before birth or in animals less than 30 days old, but symptoms generally do not appear until animals are over two years old. AGID and complement fixation tests are effective in detecting infected animals only at the very terminal stages of the disease. The sensitivity of ELISA tests allow earlier detection of infected animals which can than be segregated from the non infected animals to prevent the spread of this disease. The PAVL Johne's test is simple, rapid, sensitive, and especially useful for herd control and management of Johne's Disease. |
©2002
Pan American Vetrinary Labs
Email: bglass@pavlab.com