Q&A: pregnant women and lambing season
What the main hazards to pregnant women during lambing?
Women who are, or who may be, pregnant are potentially at risk of acquiring certain infectious diseases from pregnant livestock including sheep.
Infection with certain organisms can cause abortion in pregnant sheep, and if a pregnant woman becomes infected with these organisms they may harm her unborn child. The most important organisms are Chlamydophila abortus [which causes enzootic abortion of ewes - EAE], Toxoplasma and Listeria.
Also important is Q fever which, although less likely to cause harm to the unborn child, may cause infection in the mother.
Specific and more detailed information is available for each infection.
What are the effects of these infections in human pregnancy?
EAE may have severe consequences in pregnant women, resulting in abortion or stillbirth of the foetus. If the pregnancy survives the infection there appears to be no risk of long-term harm or birth defects.
Toxoplasmosis acquired in pregnancy may lead to infection of the foetus, resulting in congenital malformation, or later congenital disease, such as eye problems. The mother may however, show no symptoms of infection.
Listeria infection during pregnancy can cause abortion of the foetus, or premature birth. If the child is infected in the womb or during delivery this may lead to septicaemia and meningitis, which has a high fatality rate. There can also be long-term effects in many organs, including the airways, eyes and nervous system.
Q fever may lead to acute or chronic infection in the mother, and rarely to an adverse effect on the foetus.
Do these infections cause illness in humans who are not pregnant?
Yes.
What are the symptoms of illness in human infections?
Symptoms of Chlamydophila abortus infection in humans vary, from no symptoms at all to a flu-like illness, sometimes with vomiting, fear of light, sore throat and myocarditis.
Toxoplasma infection may have no symptoms in humans, or there may be acute fever with enlarged lymph glands, and in very rare cases severe infection involving the brain, muscle and eye.
Listeria infection generally causes a mild flu-like illness.
Symptoms of Q fever vary and many people will be asymptomatic. The symptoms of acute infection are similar to influenza.
How do humans acquire these infections?
Whilst the route of transmission of Chlamydophila abortus to humans is not known with certainty, the organism becomes concentrated in the uterus of pregnant sheep. Contact with aborting sheep, dead lambs, infected placentas and uterine discharges are a risk to humans.
Toxoplasmosis may be acquired through needle-stick injuries, contamination of cuts and grazes, ingestion of contaminated material or from contact with clothing of someone involved in lambing. It may also be acquired from tasting or eating undercooked infected meat containing tissue cysts, or from cat faeces.
Listeriosis is acquired by ingestion, usually of contaminated food but can also occur following contact with infected animals. Veterinarians, particularly those attending bovine abortions, can acquire cutaneous listeriosis.
Q fever can be acquired from inhalation of aerosols from placental tissue or amniotic fluids, from urine, faeces or the carcass of infected animals, from contaminated bedding or litter (hay or straw) of infected animals, or via cuts or abrasions in the skin.
How common are these infections in pregnant women?
Chlamydophila abortus: Human infection with C. abortus infection from ewes appears to be very unusual, and very few infections are reported each year in pregnant women in England and Wales. No case of chlamydiosis (including psittacosis) diagnosed in 2007 reported either contact with sheep, or occurrence in pregnancy.
Listeriosis: There are 23-30 cases reported per year in pregnant women in the UK, however it is unknown what proportion, if any, are due to contact with sheep.
Q fever: Q fever is an uncommon disease in the UK. No recent cases are known to have occured in a pregnant woman
Toxoplasmosis: In the UK approximately 2 per thousand pregnancies are affected by toxoplasmosis, with transmission to the unborn baby in 40% of these cases. It is unknown what proportion, if any, are due to sheep contact.
Is there an effective treatment for these infections?
Chlamydophila abortus can be treated using antibiotics, the drugs used vary according to the stage of the illness. Listeriosis may also be treated with antibiotics. Most toxoplasmosis infections do not require treatment, however in pregnancy, treatment may be given to reduce the possibility of transmission to the foetus, this possibility should be discussed with the woman’s doctor. Q fever can be treated with antibiotics.
Is there a vaccine?
No vaccines for human use are currently licensed for these infections. Vaccines are available for use in sheep, against Chlamydophila abortus and toxoplasmosis.
Are subsequent pregnancies likely to be at any risk?
Chlamydophila abortus, listeriosis or toxoplasmosis in pregnancy do not generally pose a risk to subsequent pregnancies in humans. There may be a risk to subsequent pregnancies in the case of Q fever, because this infection may become chronic.
How common are these diseases in sheep?
Between 20-50% of abortions in sheep are thought to be due to C. abortus. Cases have declined in recent years, and a total of 464 (36% of incidents in which a diagnosis was reached) cases were reported in 2005. However, this is likely to be an underestimate.
Cases of toxoplasmosis in sheep have generally declined since the early 1990s, following introduction of a vaccine in 1992. In 2005 it accounted for 30% of the incidents in which a diagnosis of the cause of abortion was reached..
Listeriosis is most common in sheep in winter and early spring, with an average of 50 cases of fetopathy (abortion) reported each year.
Coxiella (Q fever) infection in farm animals is usually asymptomatic, although there may be inflammation of the placenta, or an abortion. It is however uncommon as a diagnosis of abortion in sheep and cattle.
What other diseases might cause abortion in sheep?
Other organisms that may infect sheep in the UK and cause abortion include Campylobacter and Salmonella. Other infections can also cause abortion in sheep, for example Brucella melitensis, but this is not found in the UK.
Last reviewed: 6 January 2010
