ARCHIVE: Zoonoses: Advice to pregnant women during the lambing season

What are the main infectious hazards for pregnant women in contact with sheep?

Chlamydiosis (EAE), toxoplasmosis and listeriosis. There is also increasing evidence of risks to unborn children from exposure to Coxiella (Q fever). All of these agents are zoonotic (i.e. can be transmitted from animals to humans), and cause abortion in sheep and may harm pregnant women or their unborn children.

What other organisms cause abortion in sheep?

Campylobacter and Salmonella. More rarely in the UK, abortion may be due to Border Disease and tick-borne fever.  Abortion may also be caused by various fungi.

Do these agents represent any risk for pregnant women?

Neither salmonellosis nor campylobacteriosis are associated with specific effects upon human pregnancy, but both can cause human illness.

Further information on the infection risks to pregnant women during the lambing season is available on the HPA website.

The Department of Health advisory leaflet ‘While you are pregnant: How to avoid infection from food and from contact with animals’, is available, free of charge to general medical practitioners and midwives from: dh@prolog.uk.com or the telephone orderline 0300 123 1002.

Chlamydia (Enzootic Abortion of Ewes)(EAE)

What is Chlamydiosis?

Chlamydiosis is an infection caused by Chlamydophilia abortus (formerly known as Chlamydia psittacci). Chlamydiosis is thought to be transmitted by inhalation of aerosols and dusts heavily contaminated with Chlamydophilia abortus, which is the agent of enzootic abortion in ewes (EAE). It can cause serious disease in the unborn child, leading to stillbirth or abortion.

What effects does EAE have in human pregnancy?

The main effects are severe, sometimes life-threatening, disease in the mother, and stillbirth or abortion.

Is there any risk of later consequences?

If the pregnancy survives the acute infection, there appears to be no risk of long-term problems. There is no evidence that this infection can result in abnormalities in the baby when it is born (congenital malformation).

What are the symptoms of the disease in humans?

In humans infection may be asymptomatic but, where symptoms occur, they are commonly of a flu-like nature with headache, chills, fever, joint pains and non-productive cough. Photophobia, vomiting, sore throat and myocarditis may also occur. In pregnancy, a more severe form of the disease may occur, the majority of reported cases occurring between 24 and 36 weeks. This is characterised by systemic illness with disseminated intravascular coagulation (a haemorrhagic disorder), renal and hepatic complications. It is these cases that are most commonly associated with stillbirth or abortion, which generally occurs 3-8 days after the onset of the symptoms.

Who is at risk?

Only women who have close contact with ewes at the time of aborting or giving birth, with new-born lambs and with placentae or products of conception. Infection has also been associated with handling of clothing and boots contaminated by contact with infected animals.  By its nature the risk is limited mainly to those actively working with sheep, including veterinary surgeons, and their immediate families.

Although EAE is known to be present in the sheep flocks in some cases, it is often overlooked in the first year in which it is introduced to a flock. Typically, it is introduced into a flock by infected breeding females. Some of these suffer abortion in the first year and infect much of the rest of the flock but these secondary cases do not suffer abortion until the following year and a diagnosis is not made until then.

How is the infection acquired?

The route of transmission to man is not known with certainty. Inhalation of aerosols and dusts heavily contaminated with Chlamydophila abortus, appears to be the likely route of infection. The organism is concentrated in the uterus of pregnant sheep and the infected placenta and uterine discharges are the most potent sources of the infectious agent. Contact with aborting sheep, sheep at risk of abortion, dead lambs and placentae are thus considered to represent a risk for humans.

How common is this infection in man?

Human infection with Chlamydophilia abortus infection from ewes appears to be very unusual.

Very few reports of Chlamydophilia abortus in pregnant women in England and Wales are received each year by the Health Protection Agency’s Centre for Infections (CfI). In one or two cases per year (maximum 5 cases in 1986), this is associated with abortion or stillbirth. Since 1980, one maternal death associated with this infection has been reported.

In routine laboratory testing, and hence in reports to HPA CfI, no distinction is made between avian and mammalian (ovine) Chlamydophila abortus. The avian strain is not confined to psittacine birds but is common (for example) in feral pigeons. However, with the exception of one case, the severe form of the disease associated with human abortion has been due to the mammalian strain.

What tests are available to confirm the diagnosis?

Diagnosis rests chiefly on clinical suspicion and treatment should be started on that basis.

Diagnosis is generally confirmed by serological testing but this requires testing of both acute and convalescent sera. The complement fixation test (CFT) does not distinguish between Chlamydophila abortus and C. pneumoniae, and microimmunofluorescence or whole cell inclusion immunofluorescence tests are needed to confirm the diagnosis of with Chlamydophila abortus. Serological tests to distinguish avian and mammalian strains of Chlamydophila abortus may be available on a research basis.

Is there any effective treatment?

Chlamydophilia abortus is sensitive to macrolide antibiotics and a 2 week course of erythromycin 500mg 4 times daily can be given if the patient is seen at an early stage. The effectiveness of this treatment in preventing the development of more serious disease has not been established. Azithromycin is a suitable alternative. The organism is also sensitive to tetracyclines and these are probably the drug of choice in more severe disease despite the general reservations about use of tetracyclines during pregnancy.

Is there any vaccine?

There are no effective chlamydial vaccines for human use available at present.

Are subsequent pregnancies likely to be at any risk?

Following enzootic abortion, sheep generally acquire long-lasting immunity and give birth normally in subsequent seasons. Very limited data suggests that this is also the case in humans.

Is the infection common in sheep in the UK?

Yes. EAE is the commonest cause of infectious abortion in sheep. Defra laboratories diagnosed the infection in 336 reported incidents in 2008. This was a lower number than the previous year, where in 2007 it was diagnosed in 527 incidents of reported abortion. Each confirmed case generally represents an outbreak and the total number of sheep affected is therefore considerably higher. Some estimate may be gained from the fact that 20-50% of abortions in sheep are thought to be due to Chlamydophila abortus and about 1 million lambs are aborted or stillborn each year.

What are the manifestations of disease in sheep?

Characteristically, the production of dead or weak lambs in the last two or three weeks of pregnancy. Chlamydophilia abortus (Chlamydia psittaci) is the most common cause of abortion in lowland ewes, especially under intensive farming conditions.

Is a vaccine available for use in sheep?

Yes. A live vaccine is available.  However, it should not be handled by pregnant women or women of childbearing age.

Toxoplasmosis

What is toxoplasmosis?

Toxoplasmosis is a zoonotic infection (an infection that can be transmitted between animals and humans) caused by the parasite Toxoplasma gondii. Infection is usually asymptomatic or mild and self-limiting. When symptoms do appear, these are most commonly persistent acute fever with enlarged lymph glands. Very rarely there may be severe infection involving the brain, muscle and eye.

How is the infection acquired?

Routes of infection include direct contamination of cuts and grazes or ingestion of tissue cysts. If contact with ewes at lambing time is unavoidable, open wounds (cuts, grazes etc,) should be covered with waterproof dressings and hands should be thoroughly washed after handling animals to prevent the possibility of infection. Transmission of the organism can also occur from hand-to-mouth contact with faeces of infected cats, contaminated soil, poorly washed garden produce and ingestion of cysts in undercooked meat.

Who is at risk?

Pregnant women and individuals with a depressed immune system are most at risk from infection with Toxoplasma gondii.

How common is this infection in pregnant women?

In the UK, toxoplasmosis is thought to affect about 2 per thousand pregnancies. Less than half of these cases are transmitted to the unborn baby. Even when transmission occurs, the majority of babies (90-95%) have no symptoms.

What effects does toxoplasmosis have on babies when the infection has been acquired in pregnancy?

Toxoplasmosis, acquired for the first time in pregnancy, may lead to infection of the foetus and this may lead to congenital malformation.  Some affected babies may develop eye disease in later life.

If one pregnancy is affected by toxoplasmosis, are subsequent pregnancies likely to be at risk?

No.  Chronic or recurrent infection in expectant mothers is not associated with foetal infection.

What tests are available to confirm the diagnosis?

Blood tests can be carried out to detect antibodies to the organism. Since these may reflect infection in the past, confirmatory tests have to be carried out to see whether the infection is recent.

What is the recommended treatment for Toxoplasmosis infection?

Toxoplasmosis is usually a mild, self-limiting disease and does not usually require specific treatment when it occurs in normal, healthy people. 

Is there a vaccine available for humans?

No.

Is the infection common in sheep in Great Britain?

After chlamydia (EAE), toxoplasmosis is the second most common cause of abortion in sheep in Great Britain.  The number of incidents   recorded each year by Defra laboratories between 1999 and 2008       ranged from 197 to 490 reported incidents.  In 2008 it was diagnosed in 201 reported incidents.

What are the manifestations of disease in sheep?

Abortion, often in the last 4 weeks of pregnancy.  Full term lambs may be born dead or alive but weak, often dying within the first 2 weeks of life.  Mummified lambs, often one of a pair, may be seen.

Is a vaccine for use in sheep available?

Yes. There is a live vaccine for use in sheep.  However, it should not be handled by pregnant women or women of childbearing age, as it may interfere with normal foetal development.

Listeria

What is listeriosis?

Listeriosis is a disease caused by the bacterium Listeria monocytogenes. This disease can cause serious disease in the unborn or newborn child. The disease may be transmitted by contact with infected animals or ingestion of contaminated food.

What effects does listeria have in human pregnancy?

Infection may cause abortion or premature birth. Infection in utero or during delivery may lead to septicaemia and meningitis with a 50-100% mortality.

Is there any risk of later consequences?

Infection in the newborn may take the form of disseminated granulomatous disease, involving many organs including respiratory tract, eyes and nervous system.

What are the symptoms of the disease in humans?

Infection in pregnancy generally presents as a mild flu-like illness.

How is the infection acquired?

Infection is acquired by ingestion and most cases are probably the result of consumption of infected food. If contact with ewes at lambing time is unavoidable, washing of the hands after handling animals should prevent any possibility of infection.

How common is this infection

There are usually up to 25 cases of listeriosis in pregnancy reported annually in the UK, but it is not known how many of these, if any, are associated with contact with sheep.

What tests are available to confirm the diagnosis?

The diagnosis may be made by culturing the organism from the mother's blood or faeces.

Is there any effective treatment?

Listeria monocytogenes is sensitive to a number of antibiotics.

Is there any vaccine?

No.

If one pregnancy is affected by listeria, are subsequent pregnancies likely to be at any risk?

No.  Chronic or recurrent infection in expectant mothers is not associated with foetal infection

Is the infection common in sheep in Great Britain?

Listeria infection accounts for only 1-2% of sheep abortion incidents reported and diagnosed in Great Britain each year. The numbers of abortions incidents recorded by Defra veterinary laboratories for 1999-2008 ranged from 22 - 132 incidents each year (132 in 2008).  

What are the manifestations of disease in sheep?

Abortion from 12 weeks of pregnancy onwards.  There may be occasional deaths in ewes.  Encephalitis due to listeria infection may also be seen in sheep, but is not generally associated with abortions.

Q Fever

What is Q fever?

Q (Query) fever is caused by the Coxiella burnetii bacterium, and is widespread globally among livestock and domestic ruminants. Sheep, cattle and goats are the most frequent source of human infection, although pets such as dogs, and cats may also be a source.

What effects does Q fever have in human pregnancy?

Q fever acquired during pregnancy is usually asymptomatic in the mother, however chronic infections may subsequently become apparent. Occasionally, acute Q fever in pregnancy, regardless of whether this is symptomatic or not, may result in an adverse effect on the foetus including prematurity, low birth weight, or abortion.

Is there any risk of later consequences?

Subsequent pregnancies may also be at risk due to the possibility of a chronic infection in the mother.

What are the symptoms of the disease in humans?

Most people who are infected have no or very mild symptoms but very rarely serious illness occurs. Symptoms appear 2-3 weeks after exposure and include a flu-like illness with prolonged fever, tiredness, headache, muscle pains and occasionally pneumonia or other complications. Some people develop a chronic illness, with symptoms persisting for more than six months. Rarely, endocarditis (heart valve infection) may occur. This generally occurs in people who already have damaged heart valves or who have had heart by-pass surgery.

How is the infection acquired?

Inhalation is the main route of transmission to man, either from direct exposure to infected tissues (eg birth products) or indirectly through contaminated materials. Humans are at greatest risk of exposure where animals are handled when giving birth, handling birth products or during abortions because large numbers of Coxiella burnetii may be present in the birth fluids or the placenta of infected animals. They may also be present in faeces, urine or raw (untreated) milk. Coxiella burnetii may also gain entry to the body by transmission through cuts in the skin. Only small numbers of organisms are required to establish an infection.  Person-to-person spread does not generally occur.  Q fever can also be contracted by the inhalation of air borne infective spores.

How common is this infection in man?

The peak incidence of infection in humans in the UK is associated with the spring/early summer lambing season. Since 2000 the number of reported cases have declined annually and now there are less than 50 sporadic cases each year. This probably underestimates the true incidence of Q fever because many cases are mild or show no symptoms. Outbreaks have occurred in industrial settings: in Wales in 2002 and in Scotland in 2006. In 2007 an outbreak (32 cases) occurred in the Cheltenham area which was probably secondary to windborne spread from a farm source.

What tests are available to confirm the diagnosis?

Q fever is confirmed by serological (blood) testing to detect the presence of antibodies to Coxiella burnetii antigens. 

How is Q fever treated?

The treatment of choice for acute Q fever is doxycycline or tetracycline for 7-14 days, with treatment continued for at least three days after remission of fever.  Antibiotics are less effective in chronic disease and despite improved results with combination therapy (doxycycline and chloroquine) relapse rates of over 50% are still seen and a minimum of 3 years treatment is recommended.

Women who develop Q fever in pregnancy may be treated with co-trimoxazole but professional medical advice should always be sought.

Is there a vaccine against Q fever?

At present there is no licensed vaccine against Q fever available in the UK.

Is it possible to identify animals with Q fever?

Infections in animals are generally asymptomatic, however in mammals infection can result in late stage abortion, stillbirths or delivery of weak offspring.  Most animals that are infected have no clinical signs to allow diagnosis, but such individuals can still represent a risk for people to become infected.

Precautions on farms (and at other sites where animals are present and may give birth) relate to hygienic practices rather than specific action to minimise or eradicate this disease.

Further information

Page last modified: 4 February 2010