Worms and Hygiene Flashcards
What are the symptoms of Enterobius vermicularis infection? What is its common name? 22:10
Pinworm (threadworm)
Symptoms:
- Intense anal itching (pruritus; particularly at night, adult female lays up to 10,000 eggs in irritant mucus around anus; viable for up to 20 days)
- Long term infestation
What is the prevalence of Enterobius vermicularis infection in the UK? How is it transmitted?
- Most common nematode (roundworm - phylum) in the UK
- Affects up to 20% of children < 10 years
- Transmitted by faecal-oral infection, ingestion from contaminated linen or retro-infection (larvae crawl back up into colon)
What complications may arise from Enterobius vermicularis infection?
- Scratching can lead to excoriation (wearing off skin); risk of secondary infection
- Vulvitis; when worms transferred to the vagina/urethra; can result in severe pelvic inflammatory disease w/Enterobius infection and secondary E. coli infection
What are the long-term symptoms of untreated Enterobius vermicularis?
Persistent infestation can lead to:
- Loss of appetite
- Weight loss
- Insomnia
- Irritability
- Cause of nocturnal enuresis (nocturnal bed-wetting) in children
What is the non-pharmacological approach to treating E. vermicularis?
- High standards of hygiene (sufficient if continued for several weeks)
- Washing bed sheets and clothes
- Vacuuming and damp dusting of surfaces
- Basic hand-washing hygiene/etiquette (inc. under nails)
- Wearing tight-fitting undergarments prevents scratching/cotton gloves
- Bathing every morning after waking up reduces re-infestation rates
What is the pharmacological management of E. vermicularis?
Mebendazole (everyone > 2 years)
- Single dose, with a second after two weeks (reinfection common)
- Does not kill eggs; use along w/hygiene measures
- Max. 8 x 100g chewable tablets to be sold at one time (Ovex)
What are the symptoms of Strongyloides stercoralis infection?
Also known as threadworm (dumb af; call E. vermicularis pinworm then)
- Pruritus ‘larva currens’; larvae burrow through skin causing pruritus around feet and toes. Migrate via venous circulation to lungs; can cause pneumonitis (Loffler’s syndrome, like Ascaris lumbricoides), then expectorated into the pharynx, swallowed and excreted via colon.
- Cutaneous, GI and pulmonary symptoms too maybe but no problems in > 60% of cases
> > > Can lead to Hyperinfestation; widespread dissemination of larvae, leading to systemic organ failure (together w/bacterial sepsis; usually only in immunocompromised e.g. chemotherapy
How prevalent is Strongyloides stercoralis? How is it transmitted?
- Not endemic in UK
- Picked up from travel abroad; prevalent (up to 20%) in sub-Saharan Africa, S. America, SE Asia (poor sanitation, or where human excrement used routinely as fertiliser
- Worms exist in soil as free-living worm, or parasitic filariform larvae; picked up by walking barefoot in soil
What is the pharmacological treatment for Strongyloides stercoralis infection? What adjuvant measures are there?
Post-referral to infectious diseases specialist:
- Ivermectin (Stromectol); only availible via special order manufacturers (unlicensed)
- Two doses administered 2 weeks apart (although not shown to be more efficacious than single dose)
- Covers 3-4 week period of larval maturation, reducing potential auto-reinfection
> > > Combine w/wearing shoes, avoiding walking in insanitary areas
How is hyperinfestation syndrome treated in Strongyloides stercoralis infection?
- Combination of daily ivermectin (2 weeks) and antibiotics to treat associated gram -ve bacterial infection, and intensive care support (multiple organ failure)
- Mortality still high w/treatment though
- Parenteral ivermectin sometimes given; but only availible as unlicensed veterinary formulation
What are the symptoms of Taenia saginata infection?
Taeniasis (usually asymptomatic):
- GI disturbances; abdominal discomfort, diarrhoea, loss of appetite and emaciation
- Anal pruritus when proglottids excreted
- Can reach 17m (small intestines ideal environment o accommodate)
What could infection with the pig tapeworm, Taenia solium lead to?
Cysticercosis; ingesting eggs/proglottids instead of cysts
- Human becomes intermediate host for parasite
- Worm can migrate to lungs etc., even neurocysticercosis (migration to brain); causing headache, seizures, meningitis and death.
How is Taenia spp. infection treated?
- Avoid raw meat (especially abroad)
- Personal hygiene; avoid reinfection w/eggs
- Broad-spectrum anthelminthic; praziquantel or niclosamide
- Available on named-patient basis only
- Co-prescribed with laxative (help remove head scolex) and antiemetic (stopping reinfection by vomiting and re-ingesting proglottids)
What is the hygiene hypothesis?
- Lower incidence of infection in early childhood = rapid 20th century rise in allergic diseases e.g. asthma/hayfever (allergic triad)
- Protective effects of large families and certain environments e.g. farms
»> Stimulation of body’s immune defences
What is the ‘old friends’ hypothesis?
- Immune stimulation part of evolutionary development; early commensal organisms (inc. parasites) may be more important than chickenpox in childhood etc.
> Microbial diversity theory that gut flora is key for priming and regulating immune system in pregnancy and breast feeding
