Diseases

Ovine Progressive Pneumonia (OPP)

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. An ELISA test for OPP is now available through PAVL for routine testing or flock clean-up programs.

Caseous Lymphadenitis (CL)

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 and goats. Since vaccinated animals cannot be differentiated from infected animals, animals 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.

Paratuberculosis (Johne’s Disease)

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.

Brucella Ovis

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. B. Melintesis.

Q Fever

Q fever is a bacterial disease caused by infection with Coxiella burnettii. The infection occurs in many species including sheep, goats and man. In sheep and goats this disease causes late term abortions or weakened lambs and kids. The disease is of especial concern because it is highly infectious for man and causes very serious and often life threatening illness. Health problems known to be caused by Q Fever include immediate hypersensitive response including rash, and fever. Severe respiratory distress, which can result in death, is attributed to Q Fever. The effect of chronic Coxiella burnettii infection is degradation of the valves of the heart and eventually heart failure.

While Q Fever has detrimental economic effects due to lowered kidding and lambing rates and lower growth rates of infected animals, the major concern is human health problems. Birthing fluids and membranes from infected animals typically contain high levels of infectious organisms, which can be transmitted by simple contact. Contact is likely to occur with stillborn or weak lambs or kids. Handling and resuscitation of newborn or stillborn kids or lambs is an excellent opportunity to become infected.

In order to avoid these human health hazards it is important to test each animal in the herd annually for Q Fever infection.

Toxoplasmosis

Toxoplasmosis is a parasitic disease caused by infection with Toxoplasma gondii. The infection occurs in many species including sheep, goats and man. In sheep and goats this disease causes late term abortions or weakened lambs and kids. The disease is of especial concern because it is highly infectious for humans. Toxoplasmosis in pregnant women results in severe birth defects or death of the fetus. This disease has been closely associated with cats and has been called “Cat Box Disease”. Feces, milk and birthing fluids from infected animals serve as sources for infection and should be handled with care. The PAVL ELISA test for Toxoplasmosis accurately identifies infected animals and allows for safe handling.

Chagas Disease

Chagas disease also called American trypanosomiasis) is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. T. cruzi is commonly transmitted to humans and other mammals by an insect vector, the blood-sucking “kissing bugs” of the subfamily Triatominae (family Reduviidae), most commonly from species belonging to the Triatoma, Rhodnius, and Panstrongylus genera.

The disease may also be spread through blood transfusion and organ transplantation, ingestion of food contaminated with parasites, and from a mother to her fetus.

The symptoms of Chagas disease vary over the course of an infection. In the early, acute stage, symptoms are mild and usually produce no more than local swelling at the site of infection. The initial acute phase is responsive to antiparasitic treatments, with 60–90% cure rates. After 4–8 weeks, individuals with active infections enter the chronic phase of Chagas disease, which is asymptomatic for 60–80% of chronically infected individuals through their lifetime.