Parasites Flashcards
What are the different classes of parasites?
1- Protozoa
2- Helminthes
What are protozoa?
microscopic single cell eukaryotes with an active replicating form and an inactive state
What is the replicating form of a protazoa?
trophozoite
What is the inactive state of a protozoa?
cyst
Which form of protozoa is infective to humans?
cyts
What are the 4 classes of protozoa and how are these classifications made?
Classifications made by method of locomotion:
1- amoebas
2- flagellates
3- cillates
4- sporozoans
What type of locomotion do amoebas have?
psuedopod locomotion
What is the main amoeba pathogen?
E. histolytica
What is the means of locomotion for flagellates?
Flagella
What is the means of locomotion for cilliates?
cilia
What is the means of locomotion for sporozoans?
these parasites do not have any method of locomotion
What is an important sporozoan?
the Plasmodium species
What are helminthes?
multicellular organisms with organ systems and reproductive structures
How are helmiths classified and what are the classes?
They are classified according to structure:
1- Cestodes
2- Nematodes
What is characteristic of cestodes?
they are flatworms usually acquired though ingestion of contaminated food
What are nematodes?
they are round worms that can be free living or can cause intestinal disease
Which species causes malarial disease? Which one causes the most disease?
Plasmodium species (a type of sporozoan)
P. falciparum and P. vivax case the most disease
What genetic disease gives protection against malaria?
HbS and HbC give immunity to P. falciform
Individuals lacking the Duffy antigen are resistant to P. vivax
Explain the life cycle of Plasmodium
1- Mosquitos inject sporozoites into humans
2– Sporozoites travel and infect hepatocytes
3- Liver stage= 1-2 weeks
4- Hepatocytes rupture
5- Merozoites infect RBC
6- Merozoites multiply and mature into schizonts 7- Rupture the red blood cell releasing the
schizonts into the bloodstream
8- Infect other red blood cells.
What is diagnostic of the different forms of malaria?
The length of each of the phases of the life cycle and they symptoms associated with the phase. The symptoms come in a cycle and the pattern of the cycle is indicative of the malarial species
Which malaria is the most acute and sever?
P. falciform
What is particular to the pathogenesis of P. falciform?
The ability of the pathogen to sequester in the deep venous vasculature
What is an important factor to the pathogenesis of P. falciform? What is the significance?
P. falciparum erythrocyte membrane protein-1 (PfEMP-1) is central to malaria pathogenesis
which is expressed on the infected red blood cells.
These proteins have knobs that adhere to host molecules (CD36)
Where is leishmania species typically found?
tropical and subtropical regions
How is leischmaniasis transmitted?
bit from a sand fly
What are the different forms of leischmaniasis?
1- Cutaneous
2- visceral
3- mucosal
What is distinctive about cutaneous leischmaniasis?
Skin sores that develop within a few weeks/ months after the bites
What is distinctive about visceral leischmaniasis?
Usually effects the spleen, lever, and bone marrow. Develops within a few months of the bite
What is distinctive about mucosal leischmaniasis?
This form can be a sequela (consequence)
of infection with some of the species (types) of the parasite that cause cutaneous leishmaniasis
Which parasite causes Chaga’s diease/ African Sleeping Sickness?
Trypanosoma species
How is Trypanosoma species transmitted?
kissing bugs
What is the pathogenesis of chagas disease?
Occurs immediately after infection and may last up to a few weeks or months, and parasites may be found in the circulating blood (not in cells)
Fever or swelling around the site of
inoculation (where the parasite entered into the skin or mucous membrane) - usually around a child’s eye.
Many die from this disease
How is babesia microti transmitted?
tick
What are the symptoms of a B. microti infection?
Nonspecific, and develop 1 to 6 weeks after the bite
What are some common intestinal at GU Parasitic infections?
Glariasis
Cryptospoiridiosis
Amebiasis
Trichomonas vaginalis
What flagellated protozoan causes Giardiasis?
Giardia lamblia
What is the pathogenesis and symptoms of a Giardia lamblia infection?
1- injections of cytsts in contaminated water, person-to-person, and foodborne
2- acute or chronic diarrhea, cramps, bloating and flatulence
How is Giardia lamblia diagnosed?
cyst presence in the stool or Giardia antigen in the stool
How is cryptosprodium transmitted?
ingestion of oocytes
Why is it difficult to get rid of crtptospridium oocytes?
they are resistant to chlorination—so they stay in the water supply in the US and in swimming pools
What are the pathogenesis of cryptosprodiosis?
1- causes diahhheal disease
2- symptoms begin 210 days after infection
3- symtoms last 1-2 weeks in immunocompetent people
What is the pathogenesis of E. histologica?
Amebic diarrhea without dysentery is the most common disease manifestation of infection with E. histolytica.
A more severe form of infection is an amebic liver abscess. Liver abscess can manifest acutely (with fever and right upper abdominal tenderness and pain) or subacutely (with prominent weight loss and less frequent fever and abdominal pain).
What is the only natural host of T. vaginalis?
humans
How is T. vaginalis typically transmitted?
Sexual contact
What are the symptoms of T. vaginalis?
Symptoms in women include vaginal discharge, pruritus, and irritation.
Almost 50% of all women with T. vaginalis are asymptomatic. In men, the infection is usually asymptomatic
What are the common intestinal nematode infections?
Ascariasis Whipworm infection Hookworm infection Enteroblasis Intestinal Cestodes (Tapeworms)
What is the most common helminthic infection?
Ascaris lumbricides
What does the Ascaris lumbricides infect in the human host?
Small intestine (jejunum)
What is the pathogenesis of Ascaris lumbricides?
1- ingestion of eggs
2- eggs hatch and release larvae
3- larvae penetrate the intestinal wall and migrate to the liver and heart
4- then go to lungs
5- are then swallowed and return to the small intestines where they develop into mature worms
What are the symptoms of a Ascaris lumbricides infection?
Usually asymptomatic but may have pulmonary symptoms and immune mediated hypersensitivity response.
How is whipworm contracted?
soil exposure
What is the pathogenesis of whipworms?
The eggs are shed in the stool where they undergo maturation.
After ingestion the eggs hatches in the GI
track and matures to an adult worm.
The adult worm lives for 1 - 3 years.
Heavy infection occurs in the distal portion of the colon and may lead to rectal prolapse - which can be recurring.
How is Hookworm transmitted?
soil, usually i areas where human feces are used as fertilizer
What is the pathogenesis of hookworms?
Eggs are passed in the stool into soil and they hatch
The released larvae grow in the feces and/or the soil and mature and are infective.
On contact with the human host, the larvae penetrate the skin (usually the bottom of the foot) and are carried through the blood vessels to the heart and then to the lungs.
They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed.
The larvae reach the small intestine, where they
reside and mature into adults.
What is the human pinworm?
enterobiasts
What is the most common infectious worm in the united states? Most notably in school children and daycare workers?
Enterobiasis vermicularis
What is the pathogenesis of pinworm?
A person is infected with pinworms by ingesting pinworm eggs either directly or indirectly.
The eggs are deposited around the anus by the worm - the adult female worm migrates to the colon and lays eggs around the anus at night, when many of their hosts are asleep.
The most common clinical manifestation of a pinworm infection is an itchy anal region
What is a tapeworm?
Intestinal cestodes
What do tapeworms look like?
flat segmented worms that live in the intestines of some animals
How are tapeworms contracted?
eating undercooked meat from infected animals is the main cause in humans
most notably pork, beef, and fish
What is the tapeworm life cycle?
Cows and pigs become infected after feeding in areas that are contaminated with Taenia eggs from human feces.
Once inside the cow or pig, the Taenia eggs hatch in the animal’s intestine and migrate to striated muscle to develop into cysticerci.
Humans become infected with tapeworms when they eat raw or undercooked beef or pork containing infective cysticerci.
Once inside humans, Taenia cysticerci migrate to the small intestine and mature to adult tapeworms, which produce segments and eggs that are passed in feces.
Once eggs are ingested, they hatch in the intestine, invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into cysticerci.
In humans, cysts can cause serious sequellae if they localize in the brain, resulting in neurocysticercosis
