Strongyloidiasis is primarily an infection of the small bowel by the filarial worm Strongyloides stercoralis
it is endemic in the tropics and subtropics but also seen in countries with temperate climates, people who have lived or travelled to these areas are also at risk
infection can be either acute or chronic in nature
Transmission of the infection may occur through:
direct penetration of human skin by infective larvae when in contact with soil e.g. – walking barefoot
oro-anal contact – seen in homosexual men
solid organ transplants – there have been reports of transmission of the infection derived from the donor organ
faecal-oral route – may be possible when larvae contaminated water is used to wash vegetables in endemic areas
Most infections are asymptomatic however immunosuppressed individuals may suffer gross infection.
Most infections are either mild or asymptomatic.
In these patients an increase in peripheral blood eosinophil count is the only sign of infection
life-cycle
Faecal soil contamination with S stercoralis larvae are most likely to be seen in rurual areas with poor sanitation.
filariform larvae in the soil penetrate the skin when the host walks barefoot on contaminated soil
parasitic cycle
larve enters venous circulation and migrate to the lungs.
They are coughed up and swallowed.
the larvae in the small intestine develops into adult female.
The reproduce asexually and release eggs into the digestive system
hatched eggs release non-infectious rhabditiform larvae which is excreted in stools and enter the soil
free living cycle
these free-living rhabditiform larvae may mature into male and female adult worms, which reproduce sexually or transform directly into filariform larvae
S stercoralis parasite has the ability to reinfect the host through the wall of gastrointestinal system – known as autoinfection:
this is caused by rhabditiform larvae in the faeces which transforms into infectious filariform larvae inside the gastrointestinal system.
These filariform larvae penetrates the gut wall and enter the circulation and migrate to the lungs to begin the cycle again
Symptoms
ground itch
characteristic cutaneous reaction following acute larvae invasion of the skin
most commonly affects the foot
may cause serpiginous or urticarial tracts with severe pruritus lasting for several days
larva currens (literally “running larvae”)
intensely itchy red tracts seen in the perianal area and upper thighs due to rapid speed of intradermal migration (progressing at around 5-15 cm per hour) of the parasite in chronic infection
pathognomonic for strongyloidiasis
pulmonary manifestations
dry cough or wheeze
Loeffler’s-like syndrome
rare
characterised by fever, dyspnoea, wheeze, pulmonary infiltrates on chest radiographs, and accompanying blood eosinophilia
gastrointestinal manifestations
diarrhoea, anorexia, and vomiting
epigastric pain worsened by eating
Disseminated strongyloidiasis seen in immunosuppressed patients may present with
abdominal pain and distension
shock
pulmonary and neurologic complications
septicemia
should be investigated for strongyloidiasis:
travelers or people who migrate from an endemic area and develop the following within 3-4 weeks of travel:
