Eukaryotic Parasites Flashcards
Helminths
Parasitic- invade human tissues
Roundworm (nematodes);
Flatworm; Tapeworm(cestodes) and flukes(trematodes)
Helminths; method of entry
Hookworm larvae; live in soil & enter skin…multiply in digestive tract and eliminated through feces…poor sanitation and being bare-footed is a risk factor
Ingested (eating undercooked pork)
Transmitted by mosquitoes; causes elaphantiasis (lymph vessels are blocked)
Spread by flies and can cause river blindness
Helminths; complex life styles
intermediate hosts that house a sexually immature stage of the parasite and are necessary for its development (ex; snails)
Definitve host; sexual reproduction that takes place in human
Dead end host; humans become this host if infected by a parasite that normally completes its life cycle in another host
Round Worms
Has a digestive tract that goes from mouth to anus
Ascariasis (most common disease); eggs ingested, hatch in intestine and invade bloodstream, go into lungs and are coughed up or swallowed, the mature, and are excreted in feces…only steal nutrients does not feed on human tissue
Tapeworm
No digestive system
Usually infect by being injested from raw or undercooked meat or fish
Attach to intestine and absorb predigested nutrients through their body from a definitive host. Has hooks and suckers
Flukes
Has a mouth but no anus (nutrients enter mouth and waste exits mouth)
Snail host(asexual reproduction) and mammalian/verterbrate host(sexual reproduction)
Tissue flukes; hermaphrodite (has male and female organs)
Blood flukes; has separate sexes
Can cause liver damage from schistosomiasis
Giardiasis
most common waterborne illness (travelers diarrhea)
2/3 symptomatic
Gas & nausea … to Vomiting explosive diarrhea fatigue
Symptoms end early without treatment but person can be a life long carrier
Dormant Cysts (excreted from stool); tough, prevents it from environmental conditions (stomach acid) Feeding trophozoite (excreted from diarrhea); interferes with intestines ability to absorb nutrients and secrete digestive enzymes
Epidemiology; fecally contaminated water, low infectious dose, person to person spread
Treatment; Antimicrobial meds
Prevention; boiling, filtering, or disinfecting drinking water
Cryptosporidiosis
Signs/symptoms; fever, loss of appetite, nausea, watery diarrhea
Life cycle takes place in epithelial cells of small intestine
Pathogenesis; ingestion of oocysts, sporozoites released in intestine, invade epithelial cells causing inflammatory response, secretion of water and electrolytes increases, abosorption of nutrients decreases
Epi; Low infectious dose (person to person spread), cysts continually are discharged weeks after symptoms are gone, cysts resist chlorination and pass through water filtration systems. Wide host range
Treatment; antimicrobials
Prevention; Pasteurization of beverages, boiling or filtering drinking water, sanitary disposal of human and animal feces
Cyclosporiasis
Signs/symptoms; fatigue, vomiting, watery diarrhea…symptoms improve in 3 to 4 days but relapses occur for up to a month
Pathogenesis; sexual and asexual stages in intestinal epithelium
Epi; cysts not infectious so person to person spread doesn’t occur. Travelers to tropical places are at risk. Rasberries implicated in outbreaks
Treatment; antimicrobials
Prevention; boiled or filtered drinking water, thorough washing of berries and leafy veggies
Amebiasis
Life threatening in developing countries because virulent strain spreads easily in crowded unsanitary living conditions
Signs/symptoms; diarrhea, blood in feces
Path; infected cysts release trophozoites (feed on mucus and bacteria in the large intestine) has cytotoxic enzyme that kills intestinal cells. can be carried to liver and other organs and cause abscesses
Epi; ingestion of fecally contaminated food or water, poverty at risk, migrant workers, men having sex with men
Malaria
Insecticides had gotten rid of malaria in some places but in others the mosquito vectors became resistant and malaria began to reappear
Signs/Symptoms; flu like (fever headache joint pain), cold phase (feels cold and has chills), hot phase (temp rises sharply), wet phase (temp drops and sweating occurs)…the three phases are called paroxysm
Gametocytes are not responsible for symptoms but they are responsible for the person to person transfer. Schizont is responsible for symptoms
Immunodeficiency and ruptured spleen occurs.
P. falciparum is more severe; infects ALL RBC’s, causes RBC’s to stick to capillaries (blocks O2), deprives tissues of O2, leads to cerebral malaria, can cause complications in pregnancy too
Malaria common in warm climates
Transmitted by mosquitoes, blood transfusions, drug users sharing syringes
Africans are more resistant (lack duffy antigen) and person to person transmission is easier to cure than from mosquito
Treatment; most meds are effect against the erythrocytic stage (RBC not liver)…ex chloroquine, quinine, and mefloquine…combination therapies because Plasmodium is becoming resistant
Vaccines under development…best bet
Plasmodium vivax life cycle
infected mosquito ejects p vivax sporozoites into a capillary as it feeds, sporozoites are carried to and infect liver cells, multiply to form merozoites that are released into blood, infect RBC’s and form male/female gametocytes, another mosquito ingests the gametocytes and releases gametes which form to make zygotes, zygote enters gut wall and forms cyst that releases sporozoites that infect the mosquitoes salivary glands
