|
See also
management of reproduction: goats, Management of Reproduction: Goats. |
| Noninfectious causes of abortion in goats include plant toxins, such as broomweed or locoweed poisoning; dietary deficiencies of copper, selenium, vitamin A, or magnesium; and certain drugs such as estrogen, glucocorticoids, phenothiazine, carbon tetrachloride, or levamisole (in late gestation). |
| Major infectious causes of abortion in goats are chlamydophilosis, toxoplasmosis, leptospirosis, brucellosis,
Coxiella
burnetii
, and listeriosis.
Campylobacter
causes abortions but is not nearly as important in does as in ewes. |
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Chlamydophilosis (Chlamydiosis, Enzootic Abortion): |
|
Chlamydophila abortus
(the agent of enzootic abortion of ewes) is the most common cause of abortion in goats in the USA. In naive herds, up to 60% of pregnant does can abort or give birth to stillborn or weak kids. Abortions can occur at any stage of pregnancy, but most are in the last month. Reproductive failure is usually the only sign of
C
abortus
infection, but occasionally there is concurrent respiratory disease, polyarthritis, conjunctivitis, and retained placentas in the flock. Aborted lambs are usually fresh with no gross pathology. Placentitis is usually present and consists of reddish-brown exudate covering cotyledons and intercotyledonary areas. Microscopically, necrotizing vasculitis and neutrophilic inflammation are present in the placenta. Chlamydial organisms can be visualized in appropriately
stained placental smears, but they cannot be differentiated from
Coxiella
burnetii
. Fluorescent antibody or immunohistochemical staining, ELISA, PCR, or culture can be used to definitively identify
C
abortus
. The placenta is the specimen of choice, but sometimes the diagnosis can be made by testing liver, lung, and spleen. During an outbreak, aborting does should be isolated and tetracyclines given orally or parentally. There is no chlamydial vaccine for goats, but the vaccine for sheep is relatively effective. Like sheep, goats that abort are immune. Sheep that abort due to
C
abortus
remain infected for years, if not life, and shed the organism at the time of ovulation; whether or not this occurs in goats is not known.
C
abortus
is zoonotic, occasionally causing serious disease in pregnant women. |
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Toxoplasmosis: |
| Toxoplasmosis is a common cause of abortion in goats in the USA, and toxoplasmal abortion in goats is similar to the syndrome in ewes (see above). |
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Leptospirosis: |
| The most common serovars of
Leptospira
interrogans
involved in caprine abortion are
grippotyphosa
and
pomona
. While sheep are relatively resistant to leptospirosis, goats are susceptible, with abortions occurring at the time of leptospiremia. Some does have anemia, icterus, and hemoglobinemia; others are afebrile and are not icteric. Diagnosis is by serology or identification of
Leptospira
spp
in the dam’s urine, the placenta, or fetal kidney. (See also
Leptospirosis: Introduction.) |
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Brucellosis: |
|
Brucella
melitensis
is the principal organism, with occasional abortions due to
B
abortus
. Abortion may be accompanied by mastitis and lameness and is most common in the fourth month. The placenta is grossly normal, but does may develop chronic uterine lesions. Infection in adults is lifelong with organisms shed in the milk (
B
melitensis
is zoonotic but rare in the USA). In the USA, control is by test and slaughter. Tube agglutination and card tests can be used as screening tests. (See also
Brucellosis in Large Animals: Introduction.) |
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Coxiella
burnetii
Infection: |
|
Coxiella
burnetii
is increasingly recognized as an important cause of caprine abortion, especially in the western USA. Occasional outbreaks also occur in sheep. Late-term abortions, stillbirths, and weak lambs are the common presentations. Up to 50% of the flock may be involved. The placenta is covered by gray-brown exudate and the intercotyledonary areas are thickened. Microscopically, there is a necrotizing vasculitis in the placenta, and many chorionic epithelial cells are distended
by small, coccobacillary organisms <1 mm in diameter. Infection involves only the placenta; without it, the diagnosis usually cannot be made. Diagnosis is by identification of
C
burnetii
by immunologic staining methods or by isolation.
Coxiella
is zoonotic, causing Q fever in humans. |
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Listeriosis: |
|
Listeria
monocytogenes
is a common pathogen in goats and causes sporadic abortions. There are no specific fetal lesions, and the fetus is often autolyzed. The doe usually shows no signs before abortion but may develop severe metritis after abortion. Diagnosis is by isolation from the placenta, abomasal contents, or uterine discharge. In the rare case of a herd outbreak, preventive treatment with tetracycline is recommended. (See also
Listeriosis: Introduction.) |
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