Enzootic abortion
(Chlamydia)
- late pregnancy abortions, stillbirths and weak lambs
- when first introduced in a flock, abortion rates may run from 25-60% of the ewes. After the first outbreak, the incidence of abortion may drop to 1-5%
- newly purchased ewes and ewe lambs are most susceptible in contaminated farms.
- the placenta is often severely damaged and may be retained; membranes are opaque, reddened and thick
- fetus may have abnormal levels of fluid in the abdomen and enlargement of the liver
- recovered ewes are usually resistant for two to three years
Cause
- the major sources of infection are aborted fetuses, placentas, vaginal discharges, and feces from carriers
- the organism enters a non-pregnant ewe and lays dormant until the ewe conceives (accumulates in the placenta). The response during the dormant stage. During the infective stage, the ewe develops an immune response that clears the organism from the system.
- ewe usually only aborts once in her lifetime, but may remain a carrier
- an infected ewe may have a normal lamb, but spread the bacteria when stressed
Prevention
- a vaccine is available and generally considered to be effective in sheep.
- crowding at lambing time increases the risk of abortion in the same or subsequent lambing season.
- no effective way to identify infected or carrier animals. Control measures are, therefore, based on accurate diagnosis and good hygiene such as isolation of aborting ewes and disinfecting infected pens.
Vibriosis
(Campylobacter, Campylobacter jejuni)
- late pregnancy abortions, stillbirths, and weak lambs are common.
- abortion rates may reach 80-90% in previously unexposed flock
- infected ewes generally recover following abortion and can be expected to be immune to re-infection for several years
- some ewes die of complications such as infected uterus or fetal/placental retentions
- new and young ewes are most likely to abort in flocks with a history of vibrio
Cause
- some infected ewes will continue to shed bacteria in their feces.
- new ewes are infected by oral ingestion.
Prevention
- effective vaccine available
- clean flocks should be vaccinated if replacement ewes are purchased from other flocks.
- replacements should be vaccinated when brought into a flock of vibrio carriers
- vaccinate just before flushing or breeding or at weaning time.
Toxoplasmosis
(Toxoplasma gondii)
(Toxoplasma gondii)
- generally does not cause clinical signs or detrimental effects in non-pregnant, healthy ewes.
- in stressed and immunosuppressed ewes, neurological signs and death on rare occasions
- result in pregnant ewes varies with stage of pregnancy when infected: first two months = embryonic death and reabsorption; mid gestation=abortion or weak lambs; the last trimester =weak lambs or healthy, but infected lamb
- typical losses averaging 15-20% of the lamp crop.
Cause
- protozoa which causes coccidiosis-like disease in cats
- infection in sheep follows ingestion of feed or water contaminated with cat feces containing protozoa eggs
Prevention
- treatment of ewes during pregnancy with anticoccidial drugs and immunization with a live vaccine or by exposure of susceptible sheep to infection before pregnancy
- the risk of infection greatly reduced by preventing contamination of sheep feed with cat feces. Keeping cats out of sheep barns to prevent Toxoplasmosis must be weighed against the benefits of rodent control Salmonella
- abortion may occur earlier in gestation but are most common in the last month of gestation.
- abortion rates as high as 70%.
- diarrhea in ewes is common
- lambs may also contract the disease and die.
Cause
- ewes that have aborted are immune but can carry and shed bacteria for up to four months
Prevention
- no vaccine available
- ampicillin may help (consult your veterinarian)
Listeriosis
- may also cause neurological signs as well, although both neurological and abortions are rarely seen at the same time
- number of ewes affected depends on feeding practises and degree of silage spoilage
Cause
- moldy silage most often implicated
Prevention
- never feed moldy silage to sheep, especially pregnant ewes
- no vaccine available
- antibiotics may help, consult your veterinarian
Brucellosis (Brucella ovis)
- relatively rare cause of abortions in ewes
Cause
- bacteria passed from infected rams to ewes
Prevention
- perform pre-breeding and pre-purchase checks of rams for unusual scrotal swellings – don’t buy rams with abnormalities
- brucellosis is a reportable disease
