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Listeriosis in pregnancy

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Listeriosis can occur at any time in pregnancy. Patients may be asymptomatic, only being diagnosed after developing problems around delivery, or in the neonate.

  • in a case series of listeriosis in pregnancy (2)
    • 32% of women had symptoms of a flu-like illness
    • 65% had a fever
    • other symptoms included backache (21.5%) (which may be mistaken for a urinary tract infection)
    • headache (10.5%)
    • vomiting/diarrhea (7%)
    • muscle pains (4%)
    • sore throat (4%)
    • approximately 29% of the women were asymptomatic

Listeriosis occurs in 6-15/100,000 pregnancies.

Generally, perinatal infection occurs in the second or third trimester.

Diagnosis is made on the basis of clinical picture and blood culture.

Summary listeriosis:

Reservoir:

  • gastrointestinal tracts of humans, birds, cattle, sheep and other animals
  • widespread in the environment: soil, vegetation, water, silage/sewage, mammal/fish/bird faeces
  • occurs in raw foods, food components and ready to eat foods: most commonly in foods because of contamination from sites in food production environments
  • due to a listeria outbreak linked to smoked fish, people at higher risk of serious infection should only eat smoked fish products that have been thoroughly cooked (4)
    • when cooking smoked fish products at home, make sure they are steaming hot all the way through

Epidemiology:

  • listeriosis is a rare but severe systemic infection that includes bacteraemia, meningitis, encephalitis and in pregnant women can lead to miscarriage and stillbirth
  • most often affects those who have a weakened immune system including pregnant women, their unborn and new born infants, the elderly and individuals who are immunocompromised by a pre-existing medical condition or treatments for an existing illness
  • occasionally, healthy people can become infected
  • Listeriosis has a high mortality rate of 20-30% and in the UK is the most common cause of death from a foodborne illness. The annual number of laboratory-confirmed cases of listeriosis averaged 180 a year between 2005-14

Transmission:

  • majority of cases are foodborne. Cases and outbreaks have been associated with a variety of foodstuffs, the most common in England and Wales being pre-prepared sandwiches but other foods have included soft cheeses, cooked and processed meats (e.g. pâté and sliced meat), smoked fish, butter, olives and melon in the US
  • mother-to-baby transmission is important:
    • in utero transmission,
    • vertical transmission during birth, or
    • person-to-person spread soon after delivery
  • direct contact with infected animals can occasionally cause infection
  • pregnant women, individuals who are immunocompromised and those (< 1 month and >60 years of age) are more susceptible to infection
  • L. monocytogenes can be present in the faeces of approximately 5% of the population but is likely to be transitory

Incubation period

  • For invasive disease, the incubation period ranges from 1-70 days

Clinical Features:

  • initial symptoms of listeriosis include fever and flu-like symptoms, which may or may not be preceded by a febrile gastroenteritis. Pregnant women may be asymptomatic or have mild symptoms. A person of any age and immune-state may experience any of the following symptoms or remain asymptomatic. Below are the most common presentations for particular patient groups
  • Healthy adults and older children:
    • Asymptomatic infection
    • Acute gastroenteritis with fever
    • Non-specific symptoms such as fever, muscle aches, headache
    • (often goes undiagnosed/unrecognised)
  • Pregnant women
    • no/mild non-specific flu-like symptoms (as above)
    • foetal loss, stillbirth, pre-term delivery with severe infection in the newborn (some with pre-term delivery) and neonatal meningitis
  • Immunosuppressed persons / older adults
    • septicaemia, meningitis or meningo-encephalitis
  • Immunocompetent persons can also present with severe disease such as septicaemia or meningitis

Infectivity:

  • Not applicable except at and shortly after delivery due to contact (hand or fomites) from an infected infant to an apparently healthy infant who develops meningitis

Reference:

  • Benshushan A et al. Listeria infection during pregnancy: a 10 year experience. Isr Med Assoc J. 2002 Oct; 4(10):776-80.
  • Mylonakis E et al.Review Listeriosis during pregnancy: a case series and review of 222 cases.Medicine (Baltimore). 2002 Jul; 81(4):260-9
  • PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections
  • NHS Conditions. Listeriosis (Accessed 27/4/22)

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