by Rodney Kott, Extension Sheep Specialist, Montana State University

 

"A sound preventive program begins with good sheep management."

 

DISEASES CAUSING ABORTIONS

Although abortions, still-births, or weak lambs can be induced by many factors such as improper nutrition, geneticdefects, toxic plants, etc., those caused by infectious agents should be of primary concern to sheep producers.

A sound preventive program begins with good sheep management. All aborting ewes or ewes with stillborn lambs should be isolated. Any fetal and placental tissues not sent to a laboratory for further diagnosis along with any bedding contaminated should be destroyed. Pregnant ewes should not be fed on the ground as most infectious diseases can be easily transmitted via urine- and feces- contaminated feed.

In order to implement an effective control program, it is essential that a proper diagnosis be obtained. This will require a coordinated effort by you, your veterinarian, and a diagnostic laboratory. It is crucial that proper specimens be collected and submitted to a diagnostic laboratory when unexpected abortions or stillbirths occur. Both aborted fetus and placenta (as fresh as possible) must be submitted to the diagnostic laboratory in order to have a reasonable chance at a diagnosis. A little bit of forethought and precaution may prevent a major problem down the road.

VIBRIONIC ABORTION

This infectious disease is caused by a bacterium called Campylobacter fetus intes-tinalis. This is not the same organism that causes Vibrio in cattle.

Transmission: Vibrio infections are usually introduced into a flock via carrier animal. Following an outbreak some ewes may carry and consistently shed the bacteria in their feces. Other possible carrier animals include magpies and crows. Improper management of aborted fetuses, fetal membranes and uterine discharges as well as feces contaminated feed and water can cause outbreaks to spread rapidly.

Symptoms: Affected ewes abort during the last 6 to 8 weeks of pregnancy. Abortion rates of 30 % are common but may be as high as 90%. Once an abortion storm begins, it can spread rapidly causing severe losses.

Diagnosis: Preliminary diagnosis is based on clinical signs and flock history. However, in most cases laboratory diagnosis will be necessary to distinguish this disease from other common abortive diseases.

Treatment: Immediately separate aborted ewes from pregnant ewes. Feed and bedding contaminated with uterine discharges should be removed to prevent further spread. A combination of antibiotics and immediate vaccination may reduce the potential size of an utbreak.

Prevention: Vibriosis can be controlled, although perhaps not eradicated by isolation of aborting ewes, good sanitation, proper disposal of infected tissues, and proper feeding practices combined with an annual vaccination program (not the same vaccine as vibrio in cattle).

ENZOOTIC ABORTION

Enzootic abortion (EAE) is caused by a chlamydia organism.

Transmission: Initially the spread of enzootic abortion was thought to be primarily through contact with infected fetuses, placenta or vaginal discharges. However, new evidence indicates that some "carrier" ewes may constantly shed the organism in their feces or from the lungs. Although the route of infection is unclear, it appears that once the organism enters a susceptible ewe or lamb it remains dormant until the ewe becomes pregnant. The infection may then become active causing and abortion. A lamb could possibly become infected in the jug as a lamb and not exhibit any signs until she becomes pregnant.

Symptoms: Enzootic abortion is quite similar to vibriosis. Abortions occur during late pregnancy. There are also usually a number of stillbirths or weak lambs that die shortly after birth associated with this disease. The number of ewes aborting from an enzootic abortion outbreak in a sheep flock is usually significantly less than during a vibrio abortion storm. Initially when enzootic abortion first appears in a flock, abortion rates can run as high as 30%. After the disease becomes endemic the incidence usually drops to as low as 1 to 5 percent.

Diagnosis: Diagnosis is based upon clinical signs and flock history combined with laboratory diagnostic confirmation. Laboratory diagnosis is difficult and therefore it is critical that the proper samples be submitted (both fetal and placental tissues).

Treatment: Antibiotic treatment will generally stop abortions in about ten days. Proper sanitation and disposal of infected fetuses, placental tissues, bedding, etc. is vital to minimize the spread of this disease.

Prevention: The occurrence of enzootic abortion can be minimized through a combination of sanitation and management practices. Always isolate aborting ewes and properly dispose of infected tissues. Avoid feeding pregnant ewes on the ground. A vaccine is available and can be used in combination with the above practices to further reduce losses.

TOXOPLASMOSIS

Toxoplasmosis is a common intestinal infection in cats and it is an accepted fact that in ewes it follows ingestion of feed or water which has been contaminated with infected cat feces. Toxoplasmosis can cause abortion in ewes at any stage of pregnancy depending on the stage during which the ewe was infected.

Preventing Abortions

1. Prevent contamination of feed and water by not feeding on the ground or watering from stagnant contaminated pools.

2. Prevent contamination of feed and water with feces from rodents, birds and cats.

3. Immediately isolate all aborting ewes or those with vaginal discharges from the main flock.

4. Properly dispose of infected fetuses, placentas, litter and dead lambs.

5. Develop a sound, cost effective vaccination program against infectious agents of major risk in your operation.

 

METABOLIC DISORDERS

PREGNANCY TOXEMIA (TWIN LAMB KETOSIS)

Pregnancy toxemia is a metabolic disease occurring only in late pregnancy and is caused by a deficiency of energy at the body-cell level.

Cause: The most important cause of pregnancy toxemia is a decline in the plane of nutrition during the last month of pregnancy in ewes carrying two or more lambs or which have been too well fed beforehand. In such cases the disorder can be brought on by a short period of starvation caused by management changes. Exposure to bad weather or worm infestations may be a secondary factor.

Symptoms: Early clinical signs include separation of the affected ewe from the flock. There is usually a grinding of the teeth and labored breathing along with frequent urination. A smell of acetone may be detectable in the breath. Affected ewes will usually not be able to stand after 3 to 4 days and remain in a state of coma for another 3 to 4 days.

Treatment: The response to treatment is variable. Treatment is implemented to increase blood sugar supply to the body. One treatment often used is the oral administration of propylene glycol (4 to 8 oz. daily for 2 to 3 days or until ewe is eating normally). In more severe cases an intravenous injection of glucose will be necessary.

Prevention: The most effective way to minimize pregnancy toxemia is to avoid over-fatness in early and mid pregnancy and to increase the plane of nutrition as lambing approaches. This is usually accomplished by supplementing ewes beginning about one month prior to lambing with a high energy feed. Grain and molasses are very effective in providing the required increased energy. The amount of additional energy needed to meet the additional requirements is dependent upon lambing rates.

HYPOCALCEMIA (MILK FEVER)

Hypocalcemia is a metabolic disorder occurring most commonly about the time of lambing or in early lactation. This disorder occurs sporadically in the US and generally only affects less than 5% of the flock. In a severe outbreak in can affect as many as 30% of the ewes.

Cause: Hypocalcemia is caused by the sudden increased calcium demand placed on the ewe usually required for milk production at the beginning of lactation. The system which regulates blood calcium levels is relatively slow in responding to increased or decreased demands sometimes taking several days to fully adjust. Therefore, during periods of sudden increased calcium demands as in the onset of milk production, there is an inability of the animal to quickly metabolize its calcium reserves from bones.

Symptoms: Hypocalcemia develops suddenly--more suddenly than pregnancy toxemia. The earliest signs are hyperexcitability, muscle tremors and a stilted gait. As the condition progresses the ewe usually looses the ability to stand and is found lying on its brisket with the hind legs extended backwards and head either turned onto the flank or stretched forward. Death usually occurs within 6 to 48 hours.

Treatment: Treatment consists of intravenous or subcutaneous administration of calcium salts (ie 50-100 cc of calcium borogluconate--20% solution--subcutaneous). Recovery is usually complete within one or two hours.

Prevention: Control consists of avoiding predisposing causes--unnecessary stress or excitement of ewes around lambing time. Sudden changes in feed as well as periods of fasting should be avoided. Ewes grazing on beet tops or other vegetation containing oxalate salts are more susceptible.

 

VAGINAL PROLAPSE

Partial prolapse of the vagina is a common occurrence before lambing. Protrusion of the vagina may be noticed when the ewe is lying down and may return to normal when the ewe is standing. Occasionally the vagina will remain extended at all times and this requires immediate attention.

The exposed vagina is washed with soapy disinfectant solution and then obstetrical lubricant is applied liberally. Using the palms of the hand or the clinched fist the vagina is forced back into the ewe. Care must be used to avoid perforating the vagina with an extended finger or thumb. The prolapsed vagina usually blocks the urethral opening preventing urination. As soon as the vagina is pushed into place the ewe will usually urinate. It is helpful to lift up on the prolapsed vagina prior to attempting to push it back into place. This sometimes will release some of the pressure on the urethral opening allowing the ewe to urinate. Once the ewe is through urinating, slide the bearing retainer into place (make sure the blunt end of the retainer is placed directly into the center of the cervix). Ewes will generally be able to lamb normally past the prolapse retainer, but it is advisable to put these ewes in a hospital pen where they can be regularly observed.

HERNIA

Occasionally, ewes heavy with lambs will rupture during late pregnancy. Usually these ewes can be allowed to deliver the lambs normally. In severe cases it will be necessary to deliver the lambs. This can be done by inducing labor (if the ewe is within a week of lambing) or by "C section". In these instances the wee is usually euthanized and the lambs bummed or grafted. Ewes having a hernia should be culled prior to the next breeding season.

 

MASTITIS

Mastitis is an infectious disease of lactating ewes. It may be observed in ewes shortly after lambing through the post weaning period.

Symptoms: Signs of the disease develop rapidly with affected ewes having a high fever (usually around 106 or 107 degrees F). They quickly loose their appetite. The infected side of the udder will be hard, hot and may be enlarged. Due to pain the animal will hold the rear leg on the infected side off the ground. Affected ewes will usually not allow lambs to nurse. If the ewe lives the affected part of the udder will usually dry up and become small, lumpy and hard.

Treatment: Antibiotic and sulfa drugs may be used successfully if treatment is started very soon after the onset of the disease. Usually the disease is not noticed until it has progressed to a point that udder damage is irreversible. Survivors should be marked and usually culled before the next breeding season.

Prevention: The precise factors resulting in transmission of infecting bacteria and the onset of clinical mastitis are unknown. Two factors, however, appear to be sanitation and stress to the udder.

When pregnant ewes are forced to bed in filth--especially in jugs--the udder becomes heavily contaminated by many bacteria, including those that cause mastitis. Clean, dry bedding in the jugs is essential. Affected ewes should be immediately isolated to prevent utter discharges from contaminating the lambing pens and to prevent spread of the infection through suckling lambs.

Stress to the udder which could result in mastitis could be from actual physical injury (i.e. lying on hard frozen ground etc.). Also, early weaning lambs from ewes whose milk production has not yet declined without taking precautions can cause severe stress on the udder predisposing mastitis. Heavy milking ewes seem to be more susceptible to mastitis. Although effective, modifying the feed program to reduce milk production and thereby potentially reduce of mastitis does not seem to be an acceptable solution to decreasing the instance of mastitis in most situations.

Recommended Sources of Information:

SID Sheep Producers Handbook; Cost $45.00 Order from: American Sheep Industry Association, Inc.; 6911 South Yosemite, Suite 200; Englewood, CO 80112-1414.
(303) 771-3500 Ext. 46 for more information.

A Practical Guide to Sheep Disease Management by Dr. Norman Gates; Cost $22.00 plus $2.00 shipping and handling. Order from: NW Sheep Publications, 1160 Driscoll Ridge Rd., Troy, ID 83871.


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The programs of Montana State University Extension Service are available to all people regardless of race, creed, color, sex or national origin. Issued in furtherance of cooperative extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Max Amberson, Acting Director, Extension Service, Montana State University, Bozeman, MT 59717.

View Text-only Version Text-only Updated: 11/23/2005
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