Parasitology 2 Flashcards
What is the causative agent of pinworm?
Enterobius vermicularis
Describe the transmission of Enterobius vermicularis
ingestion of eggs, direct person to person
What is the definitive host of Enterobius vermuclaris
Humans- no intermediate host needed
Describe the epidemiology of pinworm
More common in children, daycare
very common worldwide and in the US
Describe the lifecycle of Enterobius vermicularis
Gravid female emerges from anus to lay eggs, perianal scratching facilitates transmission and auto-infection
Eggs in clothes, sheets can be transmitted to others
Eggs are swallowed, hatch in intestine, adults mate and migrate to colon
Describe immunity to pinworm
None- re-infection is common
How is pinworm diagnosed?
Perianal itch, restlessness, insomnia
observation of eggs, scotch tape test
What treatments can be used for pinworm?
Pyrantel pamoate, mebendazole, albendazole
Multiple treatment for severe infection, stop reinfection
Thorough housecleaning
Trichuris trichiura, or _____, infects humans worldwide and is most common in tropical countries and the poorer communities of the southern US
whipworm
What is the definitive host of whipworm?
Humans only, no intermediate
How is whipworm transmitted?
Ingestion of embryonated eggs only, no direct person to person
Describe the lifecycle of the whipworm (Trichuris trichuria)
Eggs swallowed, hatch in intestine, adults mate and migrate to colon
Adults attach in colon
Eggs passed in feces
Eggs mature 10 days in soil before infectious
Pathology of whipworm infection depends on _______
worm burden
Describe the pathology of whipworm infection
Low to moderate: usually none; bleeding; bacteremia
High: disrupted colonic mucosa, bloody stool, prolapse, anemia
Heavy burden in children leads to impaired growth cognitive ability
Is there any immunity to whipworm infection?
Possibly some- acquired immunity in natural infections
How is whipworm diagnosed?
Only by eggs in stool
What is the treatment for whipworm?
3 days of ivermectin, mebendazole or albendazole
Describe transmission of Ascaris lumbricoides
Ingestion of eggs from soil, no direct person to person
Adult worms localize to upper intestine
______ is considered a US neglected disease of poverty and is common in Appalachia and the southern US
Ascariasis
Hookworm- Necator americanus
Strongyloides
Describe the lifecycle of ascaris lumbricoides
Females lay eggs that are passed in feces
Eggs mature in soil then are swallowed
Larvae hatch and invade the intestinal mucosa, enter venous circulation to the lungs and are coughed up and swallowed
Mature and mate in small intestine
The life cycle of _____ is very unique in that the eggs enter through the GI tract but must travel to the lungs, be coughed up and swallowed in order to return to the intestine
Ascariasis
Describe the pathology of Ascariasis
usually none with low to moderate worm burden
Heavy worm loads can lead to intestinal obstruction
Stressed worms migration to nose, ear, peritoneal, thru body wall
Chronic malnutrition leads to poor mental & physical development
Describe immunity to ascariasis
Allergic inflammation from larval migration through the lungs
How is Ascariasis diagnosed?
Eggs in stool
How is Ascariasis treated?
Mebendazole, albendazole or ivermectin
Necator americanus and Ancylostoma duodenale are also known as:
hookworms
Describe the transmission of hookworms
Invasion of skin in contact with soil
NO direct person to person
What is the definitive host of hookworm?
Humans
no animal reservoir
Describe the life cycle of hookworm
Filariform larvae invade skin and go into circulation, lodge in lungs
Larvae are coughed up and swallowed and mature into adults in intestine
Eggs in feces mature in the soil to infectious filariformlarvae form
List two worm infections that involve invasion of the lungs and coughing to introduce the organism into the GI tract
- Hookworm (Necator americanus, enters bloodstream through invasion of skin–> lung–> GI)
- Ascariasis (enters GI–> lung–> back to GI)
Describe the pathology of hookworm
Initial pruritis at penetration sites
Heavy infection, larval migration through lungs can cause bronchitis
Prolonged infection leads to pulmonary symptoms like Ascaris
Exsanguination (0.03 - 0.3 ml blood/worm/day)
Anemia, reduced mental & physical development in children
Describe any immunity to hookworm
Asthmatic pathology with repeated infection
How is hookworm diagnosed?
Anemia + eggs in stool
How is hookworm treated?
Pyrantel pamoate, albendazole & mebendazole
Describe transmission of Strongyloies stercoralis
Filariform larvae penetrate
localize to small intestine
_______ with strongyloides can result in long term infection
Autoinfection
What is the definitive host of strongyloides?
Humans
Describe the life cycle of strongyloides
Adult female lays eggs in intestinal mucosa, hatch
- Direct: larvae are excreted in feces
- Indirect: sexual reproduction occurs in soil under some conditions (environmental amplification)
- Autoinfection: larvae mature in the host, enter through colonic mucosa or perianal skin (host amplification)
How is strongyloides diagnosed?
- wet mount of stool stained with iodine
- human fecal smear with immunostaining
- agar plate culture for motile larvae
- gram staining of sputum can detect filariform larvae for diagnosing pulmonary strongyloidiasis
Gram staining of sputum can detect filariform larvae for diagnosis of _______
pulmonary strongyloidiasis
Describe the pathology of strongyloides
Pulmonary manifestations
High burden leads to chronic intestinal malabsorption, dysentery
Rash on buttocks, legs and lower back due to autoinfection
Autoinfection and immunosuppression leads to hyperinfection that can be fatal
_______ infection in immune suppressed people can lead to hyperinfection that can be fatal
Stronyloides autoinfection
How is strongyloides diagnosed?
Larvae in stool, sputum
eggs NOT seen in fecal specimens
serology
How is strongyloides treated?
ivermectin 1st choice, thiabenazole 2nd choice
_______ is transmitted by eating raw or undercooked pork containing encysted larvae
Trichinella spiralis (trichinosis)
What are the definitive and intermediate hosts of Trichiniella spiralis?
Definitive: bears, swine
Incidental: humans- dead end hosts
Describe risk factors for Trichinosis
Home made sausage, hunting, undercooked pork and bear meat
Describe the life cycle of Trichinella
Transmitted to humans by eating undercooked meat containing encysted larvae
Larvae are released into GI tract
Adults develop, mate in small intestine, female embeds in mucosa
Live larvae are birthed (no eggs)
Larvae enter lymphatics, blood and encyst in muscle
Larvae develop into an encapsualted spiral which is viable for up to 10 years
In ____, the female embeds in the intestinal wall after mating and births live larvae rather than laying eggs
Trichinella spiralis
Describe the pathology of Trichinosis
Mild pathology from adult worms= nausea, cramps
Localized inflammation around individual cyst;
degeneration of muscle cell architecture
Severity related to the number of cysts. Severe symptoms: fever, muscle pain, weakness, cardiac and neural dysfunction, conjunctivitis
List unique clinical sigs of Trichinosis
eosinophilia, periorbital edema, myositis, fever
How is Trichinosis diagnosed
clinical presentation
serologic tests
How is Trichinosis treated
Mebendazole or albendazole
corticosteroids for symptoms
_______ is transmitted by cats and dogs
Toxocariasis canis/ cati
What are the definitive and intermediate hosts of Toxocariasis
Definitive: dogs
Incidental: humans
How is toxocariasis transmitted
ingestion of embryonated eggs from soil, no direct person to person
Describe the life cycle of Toxocara canis
Sexual cycle in dogs produces eggs in the feces, larvae encyst in tissue and infect puppies in utero
Humans are infected by ingestion of eggs from dogs
In humans larvae burrow through the intestine and migrate for months in any tissue
What is visceral larva migrans
Toxocara canis larval migration in a dead end host
in humans- larvae burrow through the intestine and migrate through different tissues
Describe the pathology of Toxocariasis
Light infection: self-limiting with little pathology
Heavy worm loads can lead to severe necrosis in any location
Enlarged liver, pulmonary complications, ocular lesion, neurological symptoms all grouped as visceral larva migrans
Describe any immunity to toxocariasis
Asthmatic and immune hypersensitivity are common
How is toxocariasis diagnosed?
NO eggs in stool because infection does not progress to adults
History of geophagia (eating dirt) and/or exposure to dogs
ELISA for larval antigens, but can cross with Ascaris
How is toxocariasis treated?
Albendazole or mebendazole in all cases
Corticosteroids in severe cases
How can toxocariasis be prevented?
Properly dispose of dog waste
De-worm dogs
