Listeriosis in pregnancy

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)