Parasitology Flashcards
Life stages of a parasite include:
- Egg
- Immatures = larvae (nymph)
- Adults
Host in which parasite reproduces
Definitive host
Host in which development occurs, but no reproduction
Intermediate host
How are intestinal parasites diagnosed?
Fecal specimen
How are blood parasites diagnosed?
Thick and thin specimen slides
Thick for finding the parasite
Thing for IDing the parasite
How are tissue parasites diagnosed?
Biopsy
What parasite causes amebic dysentery?
Entamoeba histolytica
What are the life stages of entamoeba histolytica?
Trophozoite - the active feeding stage
Cyst - resistant to environment and infective form
How is entamoeba histolytica transmitted?
Cysts are ingested in contaminated water or food, especially if night soil used.
Can also be vectored by flies
The cysts of entamoeba histolytica excyst where in the host?
Intestines, causing bloody diarrhea, but the trophozoite can enter the blood and move to the liver causing hepatic amebiasis (pus in liver)
What parasite causes beaver fever?
Giardia lamblia
What are the life stages of giardia lamblia?
Trophozoite - active feeding stage
Cyst - resistant to environment and infective form
How is giardia lamblia transmitted?
Cysts are ingested in contaminated water, especially if beaver habitat is close by because they are reservoirs
The cysts of giardia lamblia excyst where in the host?
They excyst in the intestines and cover the intestinal wall, interfering with fat absorption and causing diarrhea
What are the flagellated Protozoa that are pathogenic to humans?
- giardia lamblia
- trichmonas vaginalis
- trypanosoma brucei
- trypanosoma cruzi
- leishmania donovani
- leishmania tropica
- leishmania braziliensis
What are the life stages of trichomonas vaginalis?
No cyst stage, only trophozoite
How is trichomoniasis transmitted?
The trophozoite of trichomonas vaginalis is passed sexually, causing urogenital infection
What is characterized by a “strawberry cervix”, intense itching and copious discharge from a urogenital infection?
Trichamoniasis
African sleeping disease is caused by what flagellated Protozoa
Trypanosoma brucei
What is the vector for trypanosoma brucei?
Tse Tse Fly
What is the reservoir for trypanosoma brucei?
Big game animals
What are the life stages of the trypanosome parasites (brucei and cruzi)?
The Protozoa form called trypanosome, there is no cyst stage
Describe the pathology of African sleeping sickness (AKA African trypanosomiasis)
Trypanosomes invade blood, lymph nodes, spleen and CSF of host. The invade the tissue spaces, not the cells themselves. Causes mental dullness, sleepiness, coma and death
What causes Chagas’ disease?
Trypanosoma cruzi
What is the vector for trypanosoma cruzi?
The reduviid bug (kissing bug)
How is trypanosoma cruzi transmitted?
The reduviid bug vectors the parasite, feeds on the host and infects the wound through defecation
The small red nodule at the bite site of a reduviid bug that is vectoring trypanosoma cruzi is called ____.
Chagoma
What disease caused by trypanosoma cruzi mostly affects children and causes anemia, nervous disorders, muscle and bone pain, heart failure within 3-4 weeks?
Acute Chagas’ disease
What disease caused by trypanosoma cruzi is virtually asymptomatic for years and then suddenly causes death due to heart failure?
Chronic Chagas’ disease
What are the life stages of the leishmania parasites (donovani, tropica and braziliensis)?
The life stage is the Protozoa form and there is no cyst
What flagellated Protozoa causes visceral leishmaniasis (AKA Kala-azar)?
Leishmania donovani
What is the vector for all leishmania species (donovani, tropica, braziliensis)?
Sand fly
What is post-kala azar dermal leishmanoid?
A granulomatous reaction on the skin that occurs 2-3 years after being treated for leishmania donovani
Visceral leishmaniasis (AKA kala azar) affects what organs?
It causes enlarged liver and spleen, leading to wasting and eventual death if untreated
What causes cutaneous leishmaniasis (AKA oriental sore)?
Leishmania tropica, a flagellated Protozoa
What disease is characterized by a red papule from sandfly bite that is slow to heal and scars?
Cutaneous leishmaniasis AKA oriental sore
What causes mucocutaneous leishmaniasis (AKA espundia)?
Leishmania braziliensis
What disease is characterized by lesions in the junction of the pharynx that results in a break down of the palate of the nose and mouth?
Mucocutaneous leishmaniasis AKA espundia
What causes ciliary dysentery?
Balantidium coli
What are the life stages of balantidium coli?
- large ciliated trophozoite
- cyst
How is balantidium coli transmitted?
Water contaminated with pig feces
What are the symptoms associated with ciliary dysentery caused by infection with balantidium coli, a ciliated protozoa?
Abdominal pain, watery and bloody stool
What are the genera included in the sporozoa group of parasitic protozoa?
- plasmodium
- toxoplasma
- babesia
- cryptosporidium
What genera of sporozoa cause malaria?
Plasmodium
What are the life stages of plasmodium?
- Sporozoite is the infectious form that is released from mosquito into human host and then goes to the liver
In the vertebrate host, what are the two cycles that occur for the sporozoite plasmodium?
- exoerythrocytic stage occurs in the liver
- erythrocytic stage occurs in RBCs
In the erythrocytic stage of plasmodium infection, merozoites produce a waste product called ______ that causes lysis of RBCs leading to anemia and jaundice.
Malarial pigment
What is the vector for all plasmodium species (vivax, malariae, falciparum, ovale)?
Anopheles mosquito
Which species of plasmodium is the most common cause of malaria?
Plasmodium vivax
Red blood cells infected with what parasite have unique pink dots called Schuffner’s dots?
Plasmodium vivax
Malaria with a characteristic relapsing fever that occurs every other day is caused by what parasite?
Plasmodium vivax, a sporozoa
What species of plasmodium is characterized by the asexual form appearing as a rosettes in the infected RBCs and causes fever that occurs in 72 hour pattern?
Plasmodium malariae
Malaria caused by plasmodium malariae is also know as _______.
Quartan or malarial malaria
Malaria caused by plasmodium vivax is also called _______.
Benign tertian malaria
What species of plasmodium causes the most serious form of malaria?
Plasmodium falciparum
What parasitic infection is characterized by multiple sporozoite infecting one RBC creating “signet ring” formation?
Plasmodium falciparum
What parasite causes the form a malaria characterized by black water fever (intracascular hemolysis), kidney failure, mental decline, coma and death?
Plasmodium falciparum
What species of plasmodium is similar to plasmodium vivax but produces fewer merozoites and relapse of fever is common?
Plasmodium ovale
What is the definitive host for toxoplasma gondii?
Cats
What are the life stages of toxoplasma gondii?
- sporozoite are infectious form
- contained within oocyst that is passed out in feces
What are the possible means of transmission for toxoplasma gondii?
- ingestion of undercooked meat that is infected
- infection of the oocyst from recalls contaminated hands or food
- transplacental
Infection with toxoplasma in immunocompetent persons is generally asymptomatic but in those with AIDs it can cause ______
Toxoplasmic encephalitis
Congenital toxoplasmosis results from an acute primary infection acquired by the mother during pregnancy. During which trimester is it most damaging and what does it cause?
- Infection during the 1st trimester is most damaging
- causes blindness, encephalitis and mental retardation
What parasite is difficult to detect in water treatment, is resistant to chlorination and ingestion of the cyst causes watery diarrhea?
Cryptosporidium parvum
What is another name for roundworms?
Nematodes
What are the roundworms that are transmitted by ingestion of the ova?
- ascaris lumbricoides
- trichuris trichiura
- enterodius vermicularis
What is the largest nematode that parasitizes the human intestine?
Ascaris lumbricoides
What is the life cycle of ascaris lumbricoides?
Ova ingested => larva hatch in duodenum => move to lungs via blood vessels => molt and mature in lungs => larvae are coughed up and swallowed => develop into adult worm in small intestine => female produces 200,000 eggs daily that are passed in feces
The eggs of the escapism lumbricoides roundworm can stay viable in soil for how long?
Up to 3 years
What is the pathology of ascaris lumbricoides infections>
Some pulmonary symptoms during the lung stage but usually no acute symptoms until there is a high worm burden that may cause abdominal pain and intestinal or bile duct obstruction
What species of nematode is also known as the whip worm?
Trichuris trichiura
What is the life cycle of trichuris trichuria?
Eggs ingested => hatch in small intestine => larvae migrate to cecum and mature to adults => female produces 10,000 eggs daily that are excrete in feces
What is the pathology of trichuris trichiura (whip worm) infection?
Mostly asymptomatic, until there is a heavy worm burden and then it causes anemia from consumed blood cells, secondary infections from damaged epithelia, and prolapse of the rectum can occur
What is another name for the nematode, enterobius vermicularis?
Pinworm
Humans are considered to be the only hosts for which parasitic nematode?
Pinworm (enterobius vermicularis)
What is the life cycle of enterobius vemicularis?
Gravid female is nocturnal and migrates out of intestine to lay eggs on perianal skin at night => causes intense itching and eggs are transferred to fingernails and then ingested => larvae hatch in small intestine and migrate to colon where they mature into adult worm
What is a helminthic infection?
Infection with parasitic worm
What is the most common helminthic infection in the US, common in school or preschool children?
Enterobius vermicularis
What is the pathology of an enterobius vermicularis infection?
Frequently asymptomatic except perianal itching, especially at night, which may lead to secondary bacterial infection
Rarely invades female genital tract causing vulvovaginitis
What are the species of parasitic roundworm that are transmitted by direct penetration of infectious larvae?
- ancylostoma duodenale
- nectar americanus
- ancylostoma braziliense
- strongyloides stercoralis
What two species of roundworm are also known as the American hookworm?
Ancylostoma duodenale and necator americanus
What is the infective life stage form of ancylostoma duodenale and necator americanus?
Filaform
What is the life cycle of ancylostoma duodenale and necator americnus?
Adult female in small intestine lays eggs => excreted in feces => larva hatch and feed on bacteria in feces =>rhabditiform larva molts to filariform larva => filariform larva penetrates bare skin => moves to lungs => coughed up and swallowed
What is the pathology of infection with American hookworm (ancylostoma duodenale and necator americanus)
Possibly dermatitis or pulmonary symptoms in the early stages and anemia with malnutrition in the late stages
What is the dog and cat hookworm?
Ancylostoma braziliense
What is the life cycle of ancylostoma braziliense?
Larvae penetrate skin and wander because they cannot complete life cycle in humans
What is the pathogenesis of ancylostoma braziliense?
The larvae cannot complete their life cycle in humans so they cause visceral larval migrans which is a creeping eruption that causes intense itching and eosinophilia
What parasitic round worm alternates between free-living and parasitic forms?
Strongyloides stercoralis
What does ovoviviparous mean?
The eggs remain within the mother until they hatch or are about to hatch
What is the infectious for of strongyloides stercoralis
Filariform larvae
What is the lifecycle of strongyloides stercoralis?
Ovoviviparous female deposits eggs in small intestine => they hatch and are are excreted in feces or auto infect => can become free-living adults in soil or become infectious filariform larvae => larvae penetrate skin => move through blood to lungs => molt in lungs and are coughed up and swallowed
What are the main species of parasitic tissue roundworms?
- anisaka
- trichinella spiralis
- wuchereria bancrofti
- onchocerciasis vulvulus
The larvae of what parasite is found in the flesh of raw fish that can be transmitted to humans, producing intestinal obstructions, pain, nausea and vomitting?
Anisaka
What is the life cycle of trichinella spiralis?
Encrypted larvae are ingested => molt in intestines => adult female produces 100s of eggs => adult male and female die => larvae are carried via blood to muscle where they encyst => muscle tissue must be consumed for life cycle to complete => larvae calcify and die if not consumed => must be surgically removed
Humans are a dead end host for what parasitic roundworm whose larvae encyst in muscle, calcify and die?
Trichinella spiralis
What is the pathology of trichinella spiralis infection once they have encysted in muscle tissue?
- facial edema, conjunctivitis, fever, myalgia, rashes and blood eosinophilia
- occasionally myocarditis, CNS involvement and pneumonitis that can be life threatening
Bancroftian filariasis is better know as _______.
Elephantiasis
How is bancroftian filiaris vectored?
Mosquito
What is the life cycle of wuchereria bancrofti, the filarial worm that causes elephantiasis?
Ovoviviparous female in lymph duct produce immature larvae known as microfilariae => lymph nodes obstruct and swell primarily in legs and scrotum
Why can blood draws of individuals with wuchereria bancrofti infection, sometimes be absent of the parasite?
The microfilariae (larvae) exhibit periodicity and are active only at night, so blood must be drawn at night
What parasite causes river blindness?
The filarial worm, Ochocerca volvulus
What is the vector for onchocerca volvulus?
Black fly, simulium
What is the life cycle of onchocerca volvulus?
Adult worms under the skin become encapsulated by host reactions => nodules form => female releases microfilariae that migrate through skin and eyes
Trichinella spiralis has low host specificity and can infect what species other than humans?
Bears, pigs, rats
What is the pathology of onchocerca volvulus?
Larvae migrate through skin causing inflammation or eyes causing blindness
Inflammed skin known as “lizard skin” is seen in the infection with what parasite?
Onchocerciasis volvulus
What is another name for flat worms?
Platyhelminthes
What is another name for trematodes?
Flukes
What is another name for cestodes?
Tapeworms
What are the main species of parasitic trematodes/flukes, all of which have snails as their intermediate hosts to excrete cercariae?
- fasciola hepatica
- clonorchis sinesis
- fasciolopsis buski
- schistosomes (mansoni, haematobium, japonicum)
What parasitic trematode causes liver damage as well as bile duct inflammation, pain, chills and fever?
Fasciola hepatica, AKA the liver fluke
What is the life cycle of fasciola hepatica?
Adult flukes live in bile duct => eggs are passed out of liver with bile and excreted in feces => larvae penetrate snails => motile larvae leave snails and encyst as metacercariae on water plants => metacercriae are ingested => migrate to liver
The Chinese liver fluke, also known as ______, matures in the bile ducts and produce thousands of eggs daily for at least 6 months.
Clonorchis sinensis
What is the life cycle of clonorchis sinensis?
Eggs excreted in feces => hatch in water => larvae penetrate snails => cercariae leave snail to penetrate fish => metacercariae encyst in fish flesh => humans ingest metacercaria with raw fish
The giant intestinal fluke is also called ______
Fasciolopsis buski
What is the life cycle of fasciolopsis buski?
Eggs excrete in feces and infect water => larvae penetrate snail => cercariae move to plants => metacercariae encyst under leaves => humans or pigs ingest
What parasite are you most at risk of ingesting when you eat water chestnuts?
The metacercariae of fasciolopsis buski
Schistosomes are also known as ________.
Blood flukes
Most flukes are monoecious, meaning each fluke has both male and female reproductive parts. The exception is ________, that are dioecious, with separate male and female worms.
Schistosomes including mansoni, haematobium, japonicum
All three species of schistosomes (mansoni, haemotobium, japonicum) have similar life cycles. What are they?
Male and female live in blood vessels => release eggs that travel to intestine or bladder => excreted in urine or feces => eggs hatch in water => penetrate snails => snails excrete infective cercariae => cercaria penetrate skin of host => mature and reside in veins for 20-30 years
What is the pathology of infection with scistosomes (mansoni, haemotobius, japonicum)?
- Dermatitis, known as swimmer’s itch, from penetration by cercaria
- splenomegaly and ascites from eggs accumulating can causing an immune response
- eosinophilia
WHat are the main species of tapeworms that infect humans?
- taenia saginata/beef tapeworm
- taenia solium/ pork tapeworm
- diphyllobothrium latum/ fish tapeworm
- echinococcus granulosus
Adult tapeworms live in the small intestine of the human by attaching to the intestinal wall by means of a head called a _____.
scolex
The body of the tapeworm is composed of segments called ______, each of which contains a set male and female organs that produce eggs.
proglottids
Which species of tapeworm is also known as the beef tapeworm?
Taenia saginata
What species of tapeworm is also known as the pork tapeworm?
Taenia solium
What species of tapeworm is also known as the fish tapeworm?
Diphyllobothrium latum
What is the life cycle of taenia saginata?
Cattle consume gravid proglottids or eggs in contaminated feed => eggs hatch and larvae migrate to muscle => larvae encyst in muscles as cysticerci => humans consume undercooked beef
What is the pathology of taenia saginata?
Mild abdominal symptoms
Passage of proglottids in feces
What is the life cycle of taenia solium?
Same as T saginata, except the intermediate host is a pig instead of cow.
What is the pathology of infection with taenia solium?
Infective larvae migrate into muscle or tissue of human host and develop into cysticerci
Usually this does not cause symptoms but if they develop in the eye or brain, can cause meningitis, visual disturbance and acute inflammatioin
What is the life cycle of diphyllobothrium latum?
Eggs eliminated in feces => eggs hatch in water => larvae called coracidium are ingested by copepods => fish ingest copepods => larvae mature to sporangum and encyst in fish muscle => humans ingest undercooked meat
What is the pathologies associated with diphyllobothrium latum infection?
- Vitamin B12 deficiency and associated anemia
- abdominal discomfort, diarrhea, vomiting, and weight loss
What is the life cycle of echinococcus granulosus?
Adult worms infect canines and release eggs in small intestines => eggs released in feces and ingested by sheep, cattle, pigs => humans are accidental host by contact with infected dog => larvae move into liver and lung => form hydatid cyst
The hydatid cyst, as seen in echinococcus granulosus infection, contains infectious worms called _____>
Hydatid sand
What is the pathology of echinococcus granulosus?
Asymptomatic for years until enlarging hydatid cyst causes symptoms in affected organ (liver, lungs, brain, bone heart)
The cyst can also rupture and produce fever, eosinophilia and anaphylactic shock
