Overview
Also known as typhoid fever, enteric fever describes an infection characterised by systemic upset (e.g. fever, headaches, and myalgia) along with constipation caused by Salmonella typhi, a Gram-negative rod that is not part of the normal gut flora.
Paratyphoid is similar to typhoid fever, but less severe and is caused by Salmonella paratyphi. Both species are spread via the faecal-oral route through contaminated food and water.
Enteric fever is endemic in developing countries including Asia, Africa, and Central and South America.
Pathophysiology
Salmonella species invade the reticuloendothelial system and can spread to the small bowel, bone marrow, liver, and spleen. Bacteraemia occurs, resulting in fever and symptoms. Salmonella species can survive within macrophages (an intracellular organism), enabling its spread.
Presentation
Overview
Features include:
- Initially systemic upset – fever, headaches, malaise, nausea, anorexia
- Relative bradycardia (sphygmothermic dissociation or Faget sign):
- This describes fever with bradycardia or an unusually low tachycardia
- Gastrointestinal symptoms – typically pain and constipation
- Although Salmonella gastroenteritis can cause diarrhoea, enteric fever is associated with constipation
- Rose spots – these are small red macules on the skin of the trunk due to bacterial skin emboli
Since it can infiltrate the bone marrow, osteomyelitis can occur, especially in people with sickle cell disease. Other features can include dehydration, peritonitis, pneumonia, encephalitis, pericarditis, and metastatic abscesses (including the liver, spleen, and heart).
Relative bradycardia
Also known as sphygmothermic dissociation or the Faget sign, this describes fever and bradycardia/unusually low tachycardia, which is the opposite of what is expected (i.e. fever and tachycardia). This sign is associated with intracellular parasites and viral haemorrhagic fever such as typhoid fever, yellow fever, Legionella infection, Q fever, and dengue fever.
The mechanism for this sign is unknown. Some theories include suggesting that the sinoatrial node may be affected by inflammatory cytokines or that systemic inflammation may alter the dynamics of neurotransmitters in the autonomic nervous system.
Investigations
Some investigation findings may include:
- Full blood count: may show leukopenia and thrombocytopenia
- Liver function tests (LFTs): may show elevated transaminases
- Blood, urine, or stool cultures: may be positive
