Parasites Flashcards
Protozoa
Single celled, organized cell structure
May ingest solid particles
Require aquatic environment
Reproduce by binary fission at some point in their life cycle
Classified based on their means of locomotion
Helminths
Multicellular, macroscopic, organized internal structure
Flatworms and roundworms
Ectoparasites
Insects and arachnida found on the skin
Entamoeba histolytica
Disease ranges from asymptomatic, to diarrhea, to dysentery, to liver disease (amoebic abscesses)
Transmission is fecal-oral, contaminated water/food
Ingest RBCs
Entamoeba dispar
Morphologically identical to E. histolytica but does not cause disease
Dysentery
From E. histolytic burrowing into the colonic wall and making ulcers that bleed
Giardia Phylum and Order
P: Metamonada
O: Diplomonadida
Giardia lamblia
Propelled by flagella
Have shape because of rigid outer wall
Disease rangers from asymptomatic to acute or chronic diarrhea
Transmission: fecal-oral, waterborne, world wide
Diagnosis: microscopy of stool sample or antigen detection in stool using EIA
Troph and cyst form
Giardia mode of disease
Coats the inside of the small bowel and flattens the wall
Cannot absorb the nutrients you’ve ingested
Stools are bulky and floating
Can last a couple of months
Trichomonas vaginalis
Order: Trichomonadida
Causes vaginitis in females, males are most asymptomatic carriers
Sexual transmission
Detection: microscopy of discharge (wet mount for live, or gram stained for non viable), can culture
Non pathogenic spp are found in the oral cavity and gut
NO cyst form!!
African Trypanosomiasis
Phylum: Euglenozoa, Order: Trypanosomatida African sleeping sickness Fever and encephalitis Transmitted by tse tse fly Detect via blood smears and serology
South American Trypanosomiasis
Phylum: Euglenozoa, Order: Trypanosomatida
Chaga’s disease
Cardiac complications
Transmitted by reduvid bug
Bites around the eye, you scratch feces with parasites into the wound
Detect via blood smears and serology
Leishmania
Causes leishmaniasis
Cutaneous ulcers or visceral infiltration (hepatosplenomegaly)
From sandfly bite
Phylum Apicomplexa
Mature forms are non motile
Obligate intracellular parasites
Complex life cycles
Diseases: Malaria, cryptosporidiosis, toxoplasmosis
Malaria
Plasmodium spp
Diseases: episodic fevers (when they get into the blood), anemia (from RBC rupture) - life threatening
Transmitted via mosquito bites
Detected by blood film
Cryptosporidium spp
Disease: watery diarrhea (usually only lasts a week or so, longer in immunosuppressed)
Transmission: fecal oral, water borne, animals, world wide distribution
Detection: microscopy of stool using special stains (acid fast), or detection of antigen in stool using EIA
There are drugs to treat it now
Toxoplasma gondii
Mostly asymptomatic infections but new infection in pregnancy causes fetal malformations; also infection in immunosuppressed
Transmitted by poorly cooked meat, from cat stool, rarely water
Detection by serology
Cestodes
Tapeworms Ribbon lide, segmented No digestive system, adult attached to gut wall by scolex, larval form in tissues Hermaphrodites Phylum: Platyhelminthes
Cestode life cycle
Definitive host: gut contains adult worms which produce ova, passed to environment and ingested by the intermediate host where they tissues contain larval stage
Definitive host eats intermediate host, and larval form develops into the adult worm in the gut
Taenia infections
T saginata (beef) and T solium (pork)
Disease: abdominal discomfort when definitive host
Transmission by larval forms ingested in food
Detection by identification of ova or adult segments in stool
Some cestodes infect humans by the adult forms in the gut, some infect by larval form in tissues, and some infect by both
Cysticercosis
T. solium larvae in tissues
Cysts throughout the body tissues
Transmission by ingested ova
Detection by serology, x ray, ultrasound, and other methods to detect mass lesions
Trematoda
Leaf shaped, hermaphrodite, primitive gut, suckers for attachment
Has 2 intermediate hosts
Schistosoma spp
Causes schistosomiasis Effects of inflammation, hematuria Transmission by penetration of the skin Detection by ova in the stool/urine depending on species Snail is intermediate host Separate sexes
Ascaris lumbricoides
Phylum: Nemathelminthes
Separate sexes, GI tract
Nematode disease
Abdominal pain/discomfort
Transmission by fecal oral route
Detection by recognition of ova using stool microscopy or identification of adult worms
Hookworms
Chronic blood loss (a lot of worms attached)
Larvae penetrate skin*
Detection by identification of ova or larvae in stool
Can get malnutrition
Cutaneous Larva Migrans
Animal hookworm infection
A risk of travel to the Caribbean: walking barefoot on beaches shared with defecating cats and dogs
Penetrate skin and wander through your tissues
Get immune response and intense itching (serpiginous rash)
Lasts for a while
Filaria
Causes filariasis
Fevers, elephatiasis (swelling and deformity of the limbs, genitalia)
Adult lives in and damages the lymphatic drainage
Larvae are released into blood
Transmitted by mosquitoes
Detection by parasite larvae stained on blood film
Insects
6 legs
Fleas, head/body/pubic lice, bedbugs
Arachnida
8 legs, but can have 6 in immature form
Ticks, mites
What is special about bedbugs?
Not vectors of disease!!
Endo vs ecto parasites
Endo: parasites that live within another organism
Ecto: parasites that live on the external surface of another living organism
Parasite definition
A living organism that acquires some or all of its basic nutritional requirements through intimate contact with another living organism
Definitive vs Intermediate host
D: organism in which the adult or sexually mature stage of the parasite lives
I: organism in which the parasite lives during a period of its development only
Zoonosis
A parasitic disease in which an animal is normally the host, but which also infects humans
4 adaptations to a parasitic existence
Loss of structures or enzymes (GI tract) Increased reproductive ability Development of pathogenic adaptations (ex: mechanism of attachment) Defense mechanisms (ex: resistance to digestion by nematodes)
