Into to Parasitology Flashcards
How can parasites camouflage?
they are able to shuffle their surface proteins rapidly thereby escaping recognition by the immune system
How can parasites sabotage?
subvert host response
what major diseases are mosquito born?
- malaria
- elepantiatis
What major disease is fly born?
river blindness
Parasitism?
- a way of life is which one species gains its livelihood at the expense of another
- weaker organism obtains food and shelter from another organism
problems faced by parasites? (life cycle)
- ability- to establish infection in humans
- latency- ability to remain quiescent
- repliction
- restriction- in an immunological intolerant host
what are problems that parasites cause for people in terms of communication about parasites?
- attitudes that worms are not the sort of things that refined people talk about
- apparent reluctance of media to disseminate such information
- fact that poor people are the ones most seriously affected
What is key in a successful parasite? example?
- successful parasites do not harm their host
- example: herpes
What are different relationships a parasite can have with the host?
- symbiosis- close relationship
- mutualism- both benefit, not all symbiosis are mutualistic
- commensalism- one benefits, the other is not affected
Trypanosoma?
- ultimate master of disguise
- lives in blood stream and replaces its coats of proteins every two weeks
- greek trypano- auger, drill
- soma (body)- corkscrew like motion
About how many people in the world have intestinal round worms? malaria?
- worms: 1.4 billion
- malaria: 300 million
Protozoa?
- single cell
- lowest form on animal life, need microscope to see
- exist as cyst (infective stage)
- also exist as trophozoites (metabolically active stage)
Helminths?
- multicellular
- most are visible
- cause of chronic infections
- complex genome
- have multiple developmental stages
- conservation of sequences
- use of host derived cells for sequestration
- antigen masking
- antigen variation
What is Giardia lamblia (intestinalis)?
- protozoa
- cyst (infective) or trophozoites (metabolically active)
- patients with acute diarrhea pass trophozoites in stool (which are fragile, don’t survive in environment)
- cyst form- stay viable through water, desiccation, outside of body
What are some common helminths?
- nematodes- round worms
- platyhelminths- flat worms
- cestodes- tape worms
- trematodes- flukes
What are some soil dwelling nematodes/eggs?
- ascarias lumbricoides- round worms
- trichurias trichuria- whip worm
- ancylostoma duodenal- hook worm
What can we learn from the “sun king”?
-diet of rare meat was favored by nobility which contributed to parasitosis
pathogenicity of helminths?
- mechanical
- invasion and destruction of host cells
- inflammation
- competition for host nutrients
- worm burden
Charcot leyden crystals?
- the by product of eosinophil break down
- can be seen in sputum (ascariasis), stool (trichuriasis), urine, and CSF (angiostrongylus)
- they are dipyramidal and hexagonal
- usually evident with eosinophil breakdown and tissue damage from tissue invading parasites
Eosinophilia?
-generally caused by a helminth penetrating the mucous membrane during migration
Transmission of parasites?
- person to person (amebiasis)
- food borne (cyclospora)
- infected pets, farm animals, lab animals (cryptosporidium) -contaminated water (Giardia)
- sexual practices (Giardia)
- fecally contaminated fomites (cryptosporidium)
- contact with diaper age children (Giardia)
What is the F diagram? (22)
- shows the different fecal-oral transmission routes
- also shows possible barriers to prevent excreta related pathogens from finding a new host
What are barriers in specimen collection?
- perceived low occurrence of disease
- lack of familiarity with the disease
- lack of effective Rx
- expensive testing
- poor patient compliance with stool
- collection
Stool for O and P?
- should be repeated for better yield
- should be collected in closed containers
- urine and water may destroy the trophozoites
- reduced sensitivity due to interfering substances
What is the first test that can simultaneously detect 11 common viral bacterial and parasitic causes of infectious gastroenteritis from a single patient sample?
the xTAG Gastrointestinal Pathogen Panel (GPP)
What is the xTAG Gastrointestinal Pathogen Panel (GPP)?
- multiplexed nucleic acid test that detects 7 bacterial causes of gastroenteritis
- also detects 2 viruses, 2 parasites which are also common for gastroenteritis -all with one patient sample
How is there recognition of an outbreak?
- wide spread absenteeism among employees
- increased number of ER visits for diarrhea
- city wide shortage of anti-dirrheals
Delusory Parasitoses?
- patients think they have a parasite
- must seek psychiatric help Self Rx consists of:
- bathing in kerosene, mayonnaise, vinegar, bleach
- moving out of home
- picking, tweezing, cutting, poking
- shaving all of body hair
- burning skin with lighters
How do you control infection?
- proper hand washing and personal hygiene
- thorough washing/scrubbing of fruits/veggies
- proper waste disposal
- safe water supply
- thorough cooking of food
- prohibition of untreated night soil as fertilizer
- food stuff should not be harvested from pastures where animals graze
- improving domestic and personal hygiene
- controlling zoonotic reservoirs and water supplies
Hygeia?
neglected stepchild
Night soil?
human fecal matter used as fertilizer
A 73 year old woman reports that there are bugs crawling under the skin of her face and scalp. She brought multiple pieces of tape of which she has marked the areas containing insects. She lives alone with no pets. She had her house fumigated. What is her diagnosis? Doctor diagnosis?
- Her: facial xerosis
- Doctor: delusory parasitosis
What are hanging latrines?
-used as toilets and can help to end open defecation for poor in Bangladesh
What are some reasons that toilets are not used in other countries?
- sanitation is unpalatable and toilets make people go shy and giggle (not very exotic)
- mundane disease are associated with them (diarrhea and worms)
- belief that if a woman uses a latrine, she must be barren
- a pregnant woman using a latrine, her baby might fall down the pit
- it is not manly to squat and instead go in the bushes
- dropping children’s feces around compound is a sign of pride
Examples of ectoparasites?
- scabies
- head lice
What is the scabies vector?
mites
Different types of scabies? what do they look like?
- Sarcoptes Scabiei va Hominis- lives and burrows tunnels in skin, have caked on sand appearance
- crusted (Norwegian) scabies- plaques found all over
What is the systemic and topical treatment for scabies?
- systemic- ivermectin
- topical- permethrin cream, urea
What is the infection control for scabies?
- treat the contacts
- isolation
- protective garments
- separate laundering
Scabies case (37)?
-pic
Scabies case (38)?
-pic
Scabies case (39)?
-pic
Head lice infestation? how is it spread?
- pediculosis
- spread by direct head to head contact
- spread by sharing clothing (hats, bedding), combs, brushes
How do you treat head lice infestation?
- OTC pyrethrin or 1% permethrin
- prescription strength 5% permethrin, malation lotion, benzyl alcohol
- tea tree oil?
A 27 year old woman develops linear eruption. She stayed at a hotel and awoke with the rash and found 2-5mm brown insects under the bed sheet. What did she have? how is it treated?
- Cimex lectularis (bedbugs)
- treated with topical steroids
- global resurgence of bed bugs
- called the “breakfast-lunch-dinner rash” (host contact with bedding, test bites for blood vessels, interrupted feeding)
Free living parasites examples?
- Acanthemoeba castellani
- Naegleria fowleri
Acanthomoeba castellani? what does it cause?
- amebic keratitis with use of soft contact lenses
- causes ulcers in HIV patients
Naegleria fowleri? What does it cause? where is it found?
- meningo encephalitis in swimmers and divers in small lakes and ponds
- primary amoebic meningoencephalitis deaths with sinus irrigation using contaminated tap water (neti pot)
- has also been found in saline solution (trophozoites)
What is recommended for infectious control of Naeglaeria fowleri?
- for irrigation, flushing or rinsing nasal passages use sterile, distilled, filtered or previously boiled water, rinse the device the same way
- Rx: amph B, rifampin
Parasomia?
changes in smell
PAM case? (50)
pic
Pearl diving case? (51)
pic
Cutaneous acanthamebiasis? example? where does it thrive? symptoms? treatments?
- tender ulcerative nodules in a leukemic patient
- burning and painful nodules on arms, legs, abdomen
- thrives in fresh water, soil and dust
- treatment: IV amph B, antibiotics, antifungals
Risk factors for developing acanthemobiasis?
- use of contact lenses
- corneal trauma
- contaminated solutions
- two red eyes and one asymptomatic donor
Complications of acanthameobiasis?
- scleritis
- enucleation (if uncontrolled)
Other causes of acanthameobiasis?
- herpes
- fungal keratitis
Treatments of acanthameobiasis?
- aminoglycoside
- polyhexanide
- topical hexamidine
acanthameobiasis case? (55)
pic
What is the thought to be the reason for large amounts of allergies in US?
- Hygiene hypothesis
- TH2 responses such as chronic helminthiasis and malaria are not common in US and therefore the TH2 arm needs something to be filled with and it is believed that allergies are now taking their place
Naive individuals with a germ free, hygienic environment tend to have a TH2 response of what?
- allergies
- asthma
- eczema
Individuals with genetic predisposition, and poorly hygienic environment to tend to be what?
- healthy
- no asthma
- have a protective response
What is the relationship that the hygiene hypothesis has about leukemia?
-children who go to day care early in life are less likely to develop leukemia
Describe the hygiene hypothesis in terms of early germ exposure?
- exposure to microorganisms (decreased hygiene) during early age is important to develop a balanced immune system
- intestinal microbia protect against allergic inflammation
- increased hygiene leads to an uncontrolled TH2 immune response to allergens, resulting in atopic diseases
Where do parasites most likely arise from?
animals
What is Toxoplasmosis (Toxoplasma Gondii)?
-cosmopolitan AIDS defining parasite gets its name from a giant African rodent
How is Toxoplasmosis transmitted?
- ingestion of oocyst from contaminated sources (soil, cat litter, garden vegetables, water)
- ingestion of tissue cyst (bradyzoite) in undercooked meat from infected animals
- vertical transmission (mother to fetus)
- reactivation of infection in an immune compromised host
What is the Toxo Triad?
- hydrocephalus
- intracellular calcification
- choroidoretinitis
Deep seated butterfly lesion case? (64)
toxoplasmosis
Choroidoretinal case? (66)
choroidoretinal toxoplasmosis
What are the different ways Toxoplasmosis can present?
- in flu like illness and cervical lymphadenopathy
- opisthotonus (generalized rigidity) in congenital toxoplasmosis
- microphthalma(congenital toxoplasmosis)
Multi system febrile illness in cord blood transplant recipient case? (68)
toxoplasma gondii tachyzoites
toxoplasmosis case? (69)
pic
What is toxoplasma encephalitis?
- focal neurological deficit- hemiparesis, dysphasia, aphasia
- generalized cerebral dysfunction- lethargy, confusion, coma, decreased recent memory, global cognitive impairment
- neuropsychiatric abnormalities- dementia, anxiety, personality changes, psychosis
Toxoplasma encephalitis examples? (71)
pic
What are tachyzoites? what do they suggest? what do they look like?
- high prolific
- suggest an active infection
- crescent shaped
Prevention of congenital toxoplasmosis?
- never eat undercooked or raw meat during pregnancy
- pork and lamb are particularly likely to carry T. Gondii
- sufficient heat kills organism, so cook thoroughly
- wash hands thoroughly after preparing meat for cooking and never put hands in mouth
- wash kitchen surfaces that have come in contact with raw meat
- keep insects away from food, especially flies, as they can carry Toxoplasma
- if you own a cat:
- do not feed it raw meat
- get someone else to empty its letter tray, wear gloves
- disinfect litter tray with nearly boiling water for 5 minutes
- wash thoroughly vegetables from the garden
