Medically Important Parasites (3) Flashcards
Gastrointestinal nematode examples
- Enterobius vermicularis (pin worm)
- Ascaris lumbricoides
- Trichuris trichiura
- Necator amercanus (new world), Ancylostoma duodenale (old world) (hookworm)
- Strongyloides stercoralis
Enterobius vermicularis characteristics
- Pin worm
* Long pointed tail
Enterobius vermicularis ovum
- Oval
- Flattened on one side
- Thick colourless shell
Enterobius vermicularis transmission
- Faecal oral
- Ingestion
- Inhalation of ova
Enterobius vermicularis diagnosis
Scotch tape test
Enterobius vermicularis treatment
• Anti-helminthic drug (eg. Mebendazole, piperazine)
Enterobius vermicularis life cycle
- Eggs on perianal folds. Larvae inside eggs mature within 4-6h
- Embryonated eggs ingested by humans
- Larva hatch in small intestine
- Adults in lumen of caecum
- Gravid female migrate to perianal region at night to lay eggs
Ascaris lumbricoides size
• Largest intestinal nematode
Ascaris lumbricoides egg
• Broadly oval, thick, transparent shell, surrounded by yellow/brown bile-stained mammilated outer covering
Ascaris lumbricoides Pathogenesis
- Inflammatory reaction due to migrating larvae: Loffler’s Syndrome
- Blockage of intestine by adult worms
Ascaris lumbricoides diagnosis
• Fertilised/unfertilised eggs
Ascaris lumbricoides treatment
Any antiparasitic agent (mebendazole, piperazine)
Ascaris lumbricoides life cycle
L2 hatch in small intestine -> penetrate wall -> migrate via hepatic portal circulation -> alveoli of lungs -> trachea -> pharynx -> swallowed -> develop into adult worms in small intestine -> mate -> 2 months egg production
Trichuris trichiuria characteristics
- Whipworm
* slender thread-like anterior, thicker posterior
Trichuris trichiuria egg
- Bile stained
- Oval, thick, smooth shell, clear
- Prominent polar plug at each end
Trichuris trichiuria pathogenesis
- Nausea
- Diarrhoea
- Blood loss
- Rectal prolapse
Trichuris trichiuria laboratory diagnosis
- Stool examination for eggs
* Concentration techniques
Trichuris trichiuria treatment
- Mebendazole
* Good hygiene
Trichuris trichiuria life cycle
- Eggs escaping in faeces
- Development of egg in soil
- Ingesting embryonated eggs
- Larva liberated from eggs in small intestine
- Larva develops into adult worms in caecum
Necator amercanus/Ancylostoma duodenale characteristics
- Hookworm
* Hook-like anterior end
Necator amercanus/Ancylostoma duodenale buccal capsules
Necator amercanus: cutting plates
Ancylostoma duodenale: teeth
Necator amercanus/Ancylostoma duodenale ova
- Slight difference in size
- Thin, clear, smooth colourless shell
- Clear space between developing embryo and eggshell
Necator amercanus/Ancylostoma duodenale pathogenesis
- Penetrate skin: hands or feet
* nausea, vomiting, abdominal pain, anorexia, anemia
Necator amercanus/Ancylostoma duodenale diagnosis
Stool examination of eggs
