Parasites Flashcards
What are the four types of protozoa and how are they classified?
They are classified by locomotion. They include: amoebas, flagellates, ciliates, and sporozoans
What is a trophozoite?
The active replicating form of a protozoa, a single-cell eukaryotic parasite
What is a cyst? Is it infective?
The inactive, non-replicating form of a protozoa. It is the resistant stage of a parasite and is infective.
What kind of motion does an amoeba have. Give an example of a pathogen?
pseudopod. entamoeba histolytica.
Name the four flagellate pathogens commonly found in man.
- Giardia lamblia
- Trichomonas vaginalis
- Trypanosoma cruzi (American trypanosomiasis-Chagas disease) and brucei (African trypansomoiasis-sleeping sickness)
- Leishmania species
What kind of protozoa is Balantidium coli?
Ciliate
What is a sporozoan? Name an important pathogen in man of this type.
A protozoa that has no means of locomotion, maybe slight amoeba like motion. In man, this is seen in the Plasmodia species: P. vivax, P.ovale, P. falciparum, P. malariae
Name the three types of Helminths
Cestodes (tapeworms), Nematodes (roundworms), Trematodes (flatworms or flukes)
Where does the asexual stage of the malarial parasite occur?
In human
Where does the sexual stage of the malarial parasite occur
In the Invertebrate Host (The Anopheles mosquito)
What do mosquitos inject into man when they bite?
sporozoites
Where do sporozoites grow and multiply?
First in the liver, then the blood where it causes malaria. Liver stage development lasts about 1-2 weeks.
What are merozoites?
Daughter parasites that invade red cells after being released from the destruction of sporozoite containing hepatocytes.
What are gametocytes?
certain stage of the parasite in the blood that is ingested by a female Anopheles mosquito during a blood meal, enabling the start of a new cell cycle. . After 10-18 days, they become sporozoites that can be found in the salivary gland of the mosquito.
Describe schizonts
They are mature merozoites that infect other red cells
What are the stages of Malaria paroxysm? How long does it last?
Cold (cold sensation, shivering), Hot (fever, headaches, vomiting in children), Sweat (return to normal T- tiredness)
What is the key feature of the Plasmodium falcipurum pathogenesis? What proteins are important in this?
The ability for the mature trophozoites and schizonts to adhere to the deep venous endothelium. Key proteins include PfEMP-1 that bind to host cytoadherence receptors such as ICAM 1 (esp. in cerebral microvasculature) and CD 36.
How do Leishmania species spread? Where are they distributed?
By the bite of Plebotomine sandflies.
In tropical, subtropical, and temperate regions
What are the main forms of Leishmania? Describe clinical manifestations
Cutaneous (skin sores), Visceral ( lethal illness in internal organs; mostly spleen, liver, bone marrow ), and Mucosal (sequela/consequence of infection of cutaneous infecting species)
What genetic dispostion reduced Vivax infection?
The Duffy antigen necessary for their survival.
What zoonotic disease is transmitted during the blood meal of an infected hard-bodied tick of the genus Ixodes? What other disease can be transmitted from this tick?
Babesia species (Babesia mcroti). Lyme disease can also be transmitted from Borrelia borgodurferi.
What is the incubation period for Babesia micoti? What are the symptoms?
1-6 weeks after tick bite. nonspecific: fatigue/weakness/malaise/ fever/chills/sweats/ headach, maylgia, anthralgia, anorexia.
How can you transmit T. cruzi?
Trypanosoma cruzi can be transmitted by bloodsucking triatomine insects or kissing bugs’ feces containing infective worms.
What is Chagas disease? What definiing clinical manifestation may be found on a patient?
Infection from Trypanosoma cruzi may lead to a fever/ swelling at site of inoculation. This is usually around the eye. In a child, this is known as Romana’s sign.
What organs can be affected in 20-30% population of individuals affected by T. cruzi?
Heart and esophagus/colon
Which parasite is affected by the Duffy antigen and how?
P. vivax. The Duffy Antigen is the receptor on red cells that allow its entry. If the Duffy antigen is not present, it cannot invade the cell: Duffy Antigen Negativity
How is Giardiasis classified and what illness does it cause?
It is an enteric flagella protozoa that causes
“Traveler’s Diarrhea”
- Asymptomatic Cyst Passage: diarrhea (acute or chronic), malabsorption, and weight loss
or - Symptomatic giardiasis, characterized by the acute onset of diarrhea, abdominal cramps, bloating, and flatulence.
How is Giardiasis transmitted and diagnosed?
Transmission through ingestion of water contaminated with Giardia cysts, person-to-person transmission, or foodborne.
Diagnosis by testing stool for Giardiasis cysts or Giardia antigen. Cysts are hardy.
What pathogen causes Amebiasis?
Entamoeba histolytica, an invasive enteric protozoan
How is Amebiasis transmitted and what diseases does it cause?
Quadrinucleated cysts of E. hystolica is ingested from fecally contaminated water. Most commonly, Amebic diahrrea without dysentery can occur. More severe forms include a liver abscess due to toxin release and hepatocyte damage. The abscess is usually single and in the right lobe of the liver in 80% cases.
Where do T. vaginalis thrive? What species is the natural host?
In the UG tract of humans (host)
What symptoms are often experienced by women affected by Trichonomos vaginalis? What other diseases must be ruled out in the differential diagnosis?
Frothy vaginal discharge, irritation, odor, pruritus, and edema. Differential Dx: Candidiasis,bacterial vaginosis
What is the most common type of Helminthic infection?
Ascariasis lumbricoides
Where does the egg of the Ascaris mature?
They embryonate in the soil for 10-14 days
How is Ascaris trasmitted and how does it cause disease in humans?
Eggs are inhaled and ingested hatch and release larvae which penetrate the mucosal wall in Small Intestine. It disseminates to the liver via the portal veins and ultimately to the lungs (at 4 days) where it can invade the alveoli at 6-10 days. They are then coughed up and swallowed. Worms then become mature in the small intestine lasting 10-24 months.
What is the common name for Trichuris trichiura? How is it transmitted?
Whipworm Infection (third most common roundworm seen in humans). It is transmitted from soil.
Describe the life cycle and disease of Whipworm
Eggs mature in the stool. Egg hatches in GI tract and may lead to rectal prolapse as there is a heavy infection in the colon
What are the two Hookworm species? What is another term used for hookworm?
Ancylostoma duodenal and Necator Americanus. Nematode.
How is Hookworm transmitted?
Eggs are passed in the stool under warm, moist conditions.
Where is Hookworm most commonly found/?
In areas where human fecal matter is used as a fertilizer or where defacation occurs.
Hookworm larvae is known as? Where do they mature?
rhabditiform mature in the SI.
Describe the hookworm life cycle
Hookworm eggs mature in feces. The larvae penetrate human skin and then disseminate via blood vessels to the heart and then the lungs where they enter alveoli, ascent the pulmonary tree to the pharynx, and and swallowed to mature in SI.
Enterobiasis Vermicularis is known more commonly as _____ and it affects what population?
The human pinworm affects school-aged children, institutionalized children and the caregivers of the affected child
How is enterobiasis vermicularis transmitted?
A person can eat the pinworm egg directly or indirectly.
Where do pinworms deposit the egg and what is the clinical manifestation of an infected individual?
Adult Female Pinworms deposit their eggs around the anus and crawl back up to the colon while the individual is sleeping causing burning irritation and itching symptoms.
What are Intestinal Cestodes?
Also known as Tapeworms, these parasites are flat segmented worms that live in the intestines of some animals.
What is the most common way to get infected by Tapeworms?
By eating undercooked meat, humans ingesting infective cysticerci. Beef- Taenia saginata (may also be found in black bears), Pork- Taenia Solium (can also be found in wild boar) and Fish - Diphyllobothriasis
Where does the largest tapeworm matures and grows where in the body?
The largest tapeworm, Diphylloobothriasis, develops in the Small Intestine (can grow up to 30 feet long)
How do cysticerci develop?
T.solium eggs are ingested, oncospheres hatch in the intestine, invade the intestinal wall and migrate to stritated muscle, brain, liver, and other tissues where they develop into cysticerci
Describe the life cycle of tapeworms when they enter humans.
Once cysticerci are ingested, Taenia cysticerci develop into adult tapeworms which produce segments and eggs that are passed throgh the feces.
What is the disease in which humans infect themselves with eggs from a tapeworm infection? What is a possible sequalle of this disease?
Cysticercosis. Neurocystercosis in the brain.
