Diseases & Testing

CAE - Caprine Arthritis Encephalitis

Caprine arthritis encephalitis (CAE) virus is a member of the small ruminant lentiviruses (also includes ovine progressive pneumonia, or OPP, of sheep), which may lead to chronic disease of the joints, and on rare occasions, encephalitis in goat kids less than six months of age. The CAE virus is intimately associated with white blood cells; therefore, any body secretions that contain blood cells are potential sources of virus to other goats in the herd. Since not all goats that become infected with CAE virus develop clinical disease, it is important to test goats routinely for infection by means of a serologic test that detects viral antibodies in the serum.

The CAE virus is primarily transmitted to kids via colostrum in the first few feedings after birth. Blood (e.g., contaminated instruments such as needles, dehorners, etc, and open wounds) is regarded as the second most common way of spread. Contact transmission between adult goats is considered to be rare except during lactation.

CL - Caseous Lymphadenitis

Caseous Lymphadenitis (CL) is a chronic contagious disease affecting mainly sheep and goats This disease is also called pseudotuberculosis or often "abscesses," and has been referred to as the curse of the goat industry throughout the world. CL is an infection of goats, caused by Corynebacterium pseudotuberculosis.

Corynebacterium pseudotuberculosis, the bacterium that causes the disease CL, is spread from animal to animal primarily through contact with material from subcutaneous abscesses (pus) or fomites (inanimate objects) contaminated with abscess material. The organism can survive several months in the soil and environment, remaining a source of infection. Though much less common than visible subcutaneous abscesses, internal abscesses may also form in the lungs and abdominal organs as a result of spread of the organism within the animal via blood or lymph. When abscesses are present in the lungs, the organism may be transmitted through respiratory secretions (nasal discharge or coughing). In rare cases, C. pseudotuberculosis may be present in the milk. Although CL is not sexually transmitted, it is recommended to avoid natural breeding of animals with abscesses in order to prevent transmission via close contact.

Until proven negative by culture, all abscesses should be treated as if they were CL. Bacterial culture is the most reliable test for determining the CL status of an animal with abscesses. It is possible for infected animals with active abscesses to test negative on serology due to a delay in antibody production (there is a delay in antibody production after initial infection). Many environmental bacteria can cause abscesses via traumatic wounds, but unlike CL these are sporadic and not readily transmitted from animal to animal. Animals with CL abscesses should be quarantined until the abscess has completely healed or be culled. If an abscess is lanced, it should be over a hard surface that can be disinfected (concrete) or thrown away (tarp). If an abscess ruptures in a pasture, the organic material (soil, grass) is contaminated, and the pasture should be rested for a prolonged period of time; CL has been shown to survive in soil for 8 months.

OPP - Ovine Progressive Pneumonia

Ovine Progressive Pneumonia (OPP) is a slowly progressive viral disease of adult sheep caused by an ovine lentivirus. Most sheep do not show clinical signs of OPP, but the sheep that do typically don't display signs until 2 years of age or older because of the virus's long incubation period.


Scrapies:

Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), which are related to bovine spongiform encephalopathy (BSE or "mad cow disease") and chronic wasting disease of deer.

Infected flocks that contain a high percentage of susceptible animals can experience significant production losses. In these flocks over a period of several years the number of infected animals increases and the age at onset of clinical signs decreases making these flocks economically unviable. Animals sold from infected flocks spread scrapie to other flocks. The presence of scrapie in the U.S. also prevents the export of breeding stock, semen, and embryos to many other countries.  More recently, increased attention and concern has been paid to all transmissible spongiform encephalopathy (TSE) diseases, including scrapie, as a result of the discovery of bovine spongiform encephalopathy (BSE) in cattle, and the link between BSE and new variant Creutzfeldt-Jakob disease (nvCJD) in people and feline spongiform encephalopathy (FSE) in cats in Europe. This increased concern has led to the following effects:

  • Packers and producers have had difficulty in disposing of sheep offal and dead sheep causing them to incur significant increases in disposal costs,
  • Other countries have expressed concerns and have indicated that they may prohibit or restrict certain ruminant products because the U.S. has scrapie, and
  • Our domestic and international markets for sheep derived meat and bone meal, have been adversely affected.

The combination of all of these factors has led to the decision to develop a full-fledged scrapie eradication program in the U.S.

Scrapie is classified as a transmissible spongiform encephalopathy (TSE). The agent responsible for scrapie and other TSEs is smaller than the smallest known virus and has not been completely characterized. There are three main theories on the nature of the scrapie agent: (1) the agent is a virus with unusual characteristics, (2) the agent is a prion, an exclusively host-coded protein that is modified to a protease-resistant form after infection, and (3) the agent is a virino, a small, noncoding regulatory nucleic acid coated with a host-derived protective protein. The scrapie agent is extremely resistant to heat and to normal sterilization processes. It does not evoke any detectable immune response or inflammatory reaction in host animals.The scrapie agent is thought to be spread most commonly from the ewe to her offspring and to other lambs in contemporary lambing groups through contact with the placenta and placental fluids. Signs or effects of the disease usually appear two (2) to five (5) years after the animal is infected but may be longer. Sheep may live one (1) to six (6) months or longer after the onset of clinical signs, but death is inevitable.

Signs of scrapie vary widely among individual animals and develop very slowly. Due to damage to nerve cells, affected animals usually show behavioral changes, tremor (especially of head and neck), pruritus, and locomotor incoordination that progresses to recumbency and death.  Early signs include subtle changes in behavior or temperament. These changes may be followed by scratching and rubbing against fixed objects, apparently to relieve itching. Other signs are loss of coordination, weight loss despite retention of appetite, biting of feet and limbs, lip smacking, and gait abnormalities, including high-stepping of the forelegs, hopping like a rabbit, and swaying of the back end.An infected animal may appear normal if left undisturbed at rest. However, when stimulated by a sudden noise, excessive movement, or the stress of handling, the animal may tremble or fall down in a convulsive like state.

St. Croix Sheep have appeared to have a better immune system at fighting off Scrapies.

There is a genetic test now that can be used to retain and breed for stock that is Scrapies resistance.

Johnes:

The majority of MAP infections in a herd are "invisible".  Goats or Sheep with clinical signs of Johne's disease (diarrhea and weight loss) are only a small fraction of the infected animals in a herd. The infection has the ability to silently spread from adults to kids long before signs of illness in infected animals are evident.

It is a chronic disease of primarily the digestive tract in ruminants, including goats and sheep, caused by the bacterium Mycobacterium paratuberculosis (M.para. TB).

 It can be transmitted several ways. The primary means of transmission in through ingestion of feces, by  fecal-oral transmission. Adult animals shed the organism in their feces and the susceptible young ingest it. Infected goats can carry the infection in a dormant state into adulthoold and at some point begin to shed the organism in the feces.


The organism can live up to one year, maybe longer, in the soil and environment. 

Udder Problems:

There are two major udder disease problems of ewes, 

Hardbag and Bluebag:

They both tend to occur sporadically and are frustrating for producers to treat or prevent.

 HARDBAG results from an accumulation of fibrous tissue in the udder which replaces the milk producing tissues and results in lamb starvation from lack of milk. It may be caused by a virus, the same one which causes ovine progressive pneumonia, (OPP) (“lungers”). Or, it may also result after the ewe is affected with a mild or moderate case of bluebag and one or both halves of the udder fills with scar tissue. Hardbag tends to be seen by producers mostly at lambing and at weaning. When seen at lambing, the udder appears full and usually well shaped but has little or no milk for the lambs. Some ewes may develop more milk with time but usually by then the lamb has been removed or died. Hardbag is also seen at weaning or in the fall if the ewes are worked and “bagged” or crutched (shorn). If both halves of the udder are involved in most affected ewes, then the cause is likely the OPP virus. It is common in most sheep flocks, especially range ewes. Be sure to keep poor doing, “lunger” type of ewes away from replacements as infected ewes spread the virus. It takes a year or two before the infection becomes apparent by affecting their lungs or udders. A blood test for OPP is also available for those who want to eradicate the virus from their flock. If only one half of the udder is affected, the hardbag is probably due to the after affects of a bluebag type of infection. The ewe may be able to feed one lamb okay but should usually be culled from the flock. 

BLUEBAG is a severe form of mastitis and is caused by bacteria which enter through the teat canal and cause an infection in the udder. It often becomes so severe as to interfere with the blood supply to the udder. This reduced blood supply causes a blue discoloration and if there is a complete loss of blood supply, gangrene, with sloughing off that half of the udder. If seen and treated early with antibiotics, there is often a good response. But, the problem is finding and getting them treated soon enough. Bluebag usually occurs within a couple months of lambing or shortly after weaning. To prevent cases at lambing time focus efforts on: 

 1. Bedding in the corrals and in the jugs, especially directed to keeping the ewes udders dry. Provide better drainage, clean out and/or add bedding more often. 

2. Don’t put the ewes on lush feed too quickly. The production of too much milk, before the lambs are big enough to remove it, greatly increases the incidence of bluebag. 

3. Continue to provide adequate feed for the ewes so the lamb’s needs are met. If the ewes go onto poor feed and decrease their milk production, the lambs become very aggressive in nursing and the resulting udder injury contributes to more cases of bluebag. 

4. Control respiratory infections in the lambs, mostly by improving the ventilation in the lambing sheds. One of the agents most often involved in lamb respiratory disease (pasteurella) is also a major cause of ewe mastitis. A lamb with a mouthful of infectious bacteria is more likely to spread it to the teats of their dam. 

5. Try to prevent lambs “bumming” milk from ewes besides their own dam. Lambs doing this tend to spread infection to many ewes. 

6. Prevent soremouth, if it is a problem in the flock. The mouth lesions, caused by a virus, also allow the growth of a variety of bacteria which may infect the udder of ewes nursed by affected lambs.

 The major concern at weaning is the continued production of large amounts of milk and over distention of the udder. At weaning, restrict the water and feed intake of the ewes for 24 to 36 hours to rapidly decrease their milk production. 

If either hardbag or bluebag has been a special problem with your flock, seek some extra information and help in dealing with it. It may be helpful for you to collect milk samples from ewes affected with bluebag in order to determine the main bacteria involved. 

For collection, restrain the ewe in shearing position, clean off the end of the teat of the affected udder half with several pieces of cotton soaked in alcohol or iodine. Milk out 1-2 squirts, then direct the next 2-3 squirts of milk into a sterile test tube. Keep dust out of the tube while getting the milk into the tube. Don’t touch the top of the tube or the inside of the cap or stopper. These samples can be frozen until it is convenient to deliver them to the Diagnostic Lab or they can be refrigerated and shipped immediately, with an ice pack and insulation.

TESTING:

CAE - Caprine Arthritis Encephalitis

The SRLV test is a "snapshot in time" and the CAE/OPP virus can lay dormant for months or years before it begins to reproduce and become infectious. Therefore routine testing is important if you want to maintain your herd as CAE or OPP negative. 

A enzyme-linked immunosorbent assay (cELISA) test is licensed to detect antibodies to caprine arthritis-encephalitis virus (CAEV) in goat sera and antibodies to ovine progressive pneumonia virus (OPPV) in sheep sera.

A marginal result can be an indication of a recent CAE/OPP exposure as antibodies are building up in the serum, or this may be the result of a false positive, possibly from the presence of non-CAE/OPP antibodies which can interfere with the test. We suggest you wait for 6 – 8 weeks after any vaccinations, injuries or illness symptoms are gone and resubmit for a confirmation.  Kids less than 6 - 9 months old may test positive for CAE/OPP if they have received colostrum or milk containing CAE/OPP antibodies. We suggest testing  kids after nine months of age to verify their status.

We recommend collecting 2 ccs of blood in a plain red top or red and gray serum separator tube. Tubes should be labeled at minimum with a tube sequence number and additionally with an animal ID or registration number.  

Collected Samples must be kept chilled and submitted to lab immediately.

CL - Caseous Lymphandenitis

IMPORTANT:  There is a Vaccine for CL.
Animals vaccinated with the CL vaccine should not be tested.

There are 2 test methods:
1.  bacterial culture to detect the bacterial organism in abscess material

2.  serology to detect C. pseudotuberculosis-specific antibodies in sheep and goat blood samples. 

For animals with visible subcutaneous abscesses, it is best to submit abscess material for culture since this is the most direct and definitive method to diagnose CL in an individual animal. It is recommended that all abscesses be cultured regardless of serology test results.

The serological test is the best method of “herd-level diagnosis” (screening herds).   The Synergistic Hemolysin Inhibition (SHI) test, which measures the antibody response to an exotoxin produced by the organism. No CL serological test is sufficiently reliable to confidently detect infection in individual sheep or goats, therefore the serology results for an individual animal test should be interpreted with caution. Furthermore, although a positive serologic test result alone may indicate active infection, it also may indicate past infection that has resolved. 

For bacterial culture, collect abscess material in a sterile container (red top tube, for example) or with a bacterial culture swab. If an abscess is lanced, be sure not to contaminate the environment (see #4 for more information). Please include ice packs with samples intended for culture, and always enclose the primary container in a sealed bag or secondary container.

For serology, blood should be collected into a five or ten ml. "red-top" clot tube or serum separator tube.  Leave the blood at room temperature for at least 1 hour to allow clot formation. We do not recommend separating the serum from the clot prior to shipment. Ice packs are not required for shipping blood samples unless the weather is very hot.  Use bubble wrap to pad the tubes and pack the box so that no tubes break when dropped.

When acquiring new animals, testing the herd of origin (10 or more animals) is the preferred approach to determining the status of the new additions. If testing the herd of origin is impossible, new additions should be quarantined and tested twice (30 days apart) before introduction into the negative herd. Testing only the new additions provides less confidence in negative tests than does testing the herd of origin. The frequency for testing an established herd or flock should be based on previous test results, eradication strategies, and the risk of exposure to other herds or flocks.

OPP - Ovine Progressive Pneumonia

The AGID, which detects viral infection by identifying antibody response, has proven effective in eradicating OPP for more than 30 years and is the prescribed test for international trade. It is simple, reliable, inexpensive, and “standard” in that most labs use a USDA-licensed test kit — including OPP antigen — from the same manufacturer.

Since it can take 12 weeks or longer for detectable antibodies to develop following infection with the OPP virus, two or three subsequent negative tests done at 6-12 month intervals will increase confidence in the negative status of a given animal. The AGID does not give false positives. And seroconversion is permanent, meaning that an AGID test-positive animal will remain positive on future tests.

RECOMMENDATIONS FOR PARTIAL FLOCK TESTING

While whole-flock tests are the norm for small numbers of animals and for seedstock producers wishing to eradicate, partial screening can be used to estimate the level of infection in larger flocks.
It is recommended that 50% of flock be tested if doing a partial flock testing.

**  Submit 1 ml of serum for the AGID.

 A 3 ml blood draw is adequate for AGID or ELISA. Use a new, sterile needle/syringe for each animal. If collecting into syringes, blood must then be transferred into red-top glass tubes to clot. While transferring, be sure to direct blood gently down the inside of the tube to avoid “splashing” (splashing may make your serum pink instead of straw colored.

Preferred are glass tubes with red rubber stoppers/caps, 16 x 100 mm size (10 ml, finger diameter, 4” long). For the serum, drawn off after blood has been allowed to clot in the red-top tubes, plastic tubes with snap caps are O.K., but push-in caps are difficult to remove. Avoid plastic tubes with push-in caps, as well as very slim (pencil diameter) or short (5 ml “stubby”) glass tubes. 

Send only serum drawn/poured off of blood clots for AGID or ELISA. Your vet can spin these down, or blood can be allowed to clot at room temperature in the red-top tubes and then serum transferred to a fresh tube. Serum may be refrigerated or frozen, but NEVER freeze whole blood.

Number tubes 1 through XXX. Number should be dark, easy to read, and placed at the very top of the label (nearest the rubber stopper/cap) while the tube is held in an upright position. Then, turning the tube on its side (horizontal), write the date drawn, the individual animal ID, and your last name on the label.

Scrapies

Scrapies has been found to be on the Condon 171 gene.  
There is now a test which can be ran on your flock to show you if your animal is:
RR - Scrapie Resistance - Carries 2 Resistant Genes.
QR - Scrapie Resistance but carries 1 Scrapie Susecptible Gene.  Could produce Scrapie Susecptible offspring if not bred to an RR mate.
QQ - Susecptible to Scrapies

A breeder could eradicate potential threat of Scrapies to their lambs by using only "RR" Rams.

Using "QR" and/ or "RR" Ewes would result in a Scrapie Free Flock if bred to "RR" rams.

We used "GENE CHECK" to test the Sheep here at LA Farm.  While we do not have a complete herd of QQ and RR genetics at this time we are working towards it.  We could not bring ourselves to sell off some of our best Ewes due to their Scrapie Genetic Testing Results but are keeping "QR" and "RR" offspring from them for replacements.  

Johnes

  • Blood tests (ELISA)
  • Milk tests (ELISA)
  • Individual and pooled fecal tests (Direct PCR)  


Responsibility of Buyer and Breeder:

It is the breeder/flock owners responsibility to manage their flock/herd in a responsible manner which would keep contagious diseases from spreading throughout their flock.

It is the Buyers responsibility to do their homework, ask questions and use common sense when buying animals.  If your not buying from tested flocks then your playing Russion Roulette.

Expect to pay more for animals from a tested CLEAR flock/herd just as you would expect to pay more for an animal of quality.   The expense is WELL WORTH it in the long run.