Microbiology - Vossler - Parasitic Infections of the Blood Flashcards Preview

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Flashcards in Microbiology - Vossler - Parasitic Infections of the Blood Deck (90):

The main type of malaria in (sub-saharan) Africa is caused by:

plasmodium falciparum, the most lethal strain


_____ is the most common malaria strain worldwide and is the cause of a large percentage of cases in the United States.

P. vivax is the most common strain worldwide and is the cause of a large percentage of cases in the United States.

P. falciparum is next most common.

Less common are P. malariae and P. ovale


T/F: Untreated infected patients eventually develop curative immunity against the parasitizing strain or malaria



_______ is the erythrocyte receptor for P. vivax merozoite invasion.

Duffy antigen is the erythrocyte receptor for P. vivax merozoite invasion.

Absence of the Duffy antigen (West Africans) is protective against P. vivax.


The anemia in malaria is due to:

The anemia in malaria is due to the rupture of parasitized erythrocytes, removal of parasitized and unparasitized erythrocytes by the spleen, capillary sequestration and bone marrow dyserythropoiesis


Name 3 symptoms of malaria.

fever, chills, headache, sweats, Fatigue, nausea and vomiting, splenomegaly, cough, back pain, muscle pain


What is the cold stage of the malaria paroxysm?

The malaria paroxysm --> the rupturing of RBCs every 48-72 hours

"feeling of intense cold
vigorous shivering
lasts 15-60 minutes"


What is the hot stage of the malaria paroxysm?

Follows cold stage:
"intense heat
dry burning skin
throbbing headache
lasts 2-6 hours"


What is the sweating stage of the malaria paroxysm?

After the hot stage
Full paroxysm may last 4-8 hours and then resolve

"profuse sweating
declining temperature
exhausted and weak →sleep
lasts 2-4 hours"


The cyclic pattern of malaria symptoms is due to:

The cyclic pattern of malaria symptoms is due to the life cycle of malaria parasites camera as they develop, reproduce, and are released from the red blood cells and liver cells in the human body. This cycle of symptoms is also one of the major indicators of the species malaria causing infection.


Recrudescence is:

Recrudescence is used to describe the situation in which parasitemia falls below detectable levels and then later increases to a detectible parasitemia.


Relapse is:

Reactivation of the infection via hypnozoites released from the liver.
P. vivax and P. ovale have liver stages can remain in the body for up to 30 years w/o symptoms.
Hepatocytes rupture

Relapse is NOT seen in P. falciparum and P. malariae.


The ability to sequester in the deep venous microvasculature characterizes what malaria strain?

An important feature of the pathogenesis of P. falciparum is its ability to sequester in the deep venous microvasculature.


The most significant pulmonary manifestation directly attributable to P. falciparum is:

Noncardiogenic pulmonary edema


Hypoglycemia in malaria can cause coma and convulsions and contributes substantially to the morbidity and mortality associated with _______.

cerebral malaria

The classic histopathological finding of fatal cerebral malaria is the intense sequestration of parasites in the cerebral microvasculature often accompanied by ring hemorrhages, perivascular leukocyte infiltrates, and immunohistochemical evidence for endothelial cell activation.

Sequestration of parasites is thought to stimulate the local production of inflammatory cytokines and mediators.


Name the four major sequelae associated with P. Falciparum infection:

Metabolic Acidosis
Pulmonary edema and respiratory distress

P. falciparum erythrocyte membrane protein-1 (PfEMP-1) is central to malaria pathogenesis, specifically P. falciparum.


_____ is the major receptor for PfEMP-1



T/F: Malaria is intracellular.



The primary factor for malaria resurgence seems to be:

drug-resistant strains popping up


Malaria is exclusively transmitted through bites from the ____ mosquito.



Chagas disease is also known as:

American Trypanosomiasis
caused by the protozoan Trypanosoma cruzi


What is the vector for Trypanosoma cruzi?

The reduviid bug in the Americas;
the tse tse fly in Africa


T/F: Vertical transmission of Trypanosoma cruzi is possible.



What is Romana's sign?

Swelling of the eyelids near the reduviid bute where the feces was rubbed into the eye


The initial phase of Chagas disease lasts:

4-8 weeks, acute

Chronic can be for life in 30-40% of patients


What is Chagas heart disease?

Low intensity, slowly progressive myocarditis
20-30% of individuals
sudden death common


Megacolon describes what chronic disease?

A manifestation of chronic Chagas disease
Can also have megaesophagus


How is the diagnosis of Chagas made?

Acute infection - detection of trypomastigotes in the blood

chronic - need two IgG readings (ie ELISA and indirect immunoflourescence)


How is leishmaniasis transmitted?

Sand fly


The three types of leishmaniasis are:



________ is considered to be a leading cause of death attributed to foodborne illness in the United States.

Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States.


What are the methods of toxoplasma gondii transmission?

People become infected through the accidental consumption of feline fecal material,
through food or water with fecal contamination,
through the consumption of undercooked meat containing infective cysts,
through transplantation, or
transplacentally from mother to fetus.


The classic triad of signs suggestive of congenital toxoplasmosis includes

chorioretinitis, hydrocephalus, and intracranial calcifications.

highest risk of transmission is during 3rd trimester


_______ is the leading cause of focal central nervous system (CNS) disease in AIDS.

Toxoplasmosis is the leading cause of focal central nervous system (CNS) disease in AIDS.


Humans are what kind of host for T. gondii?



In the human eye, toxoplasma infection causes:

a necrotizing chorioretinitis, with varying (and recurring) degrees of posterior and anterior uveitis


Testing for what determines a person's exposure to T. gondii?

Antibodies (IgG and IgM)


Plasmodium (malaria)

Blood borne parasite - Protozoan (single celled) - (malaria)


Trypanosoma (Chaga’s disease)

Blood borne parasite - Protozoan (single celled) - (Chaga’s disease)



Blood borne parasite - Protozoan (single celled) - (Babesiosis)



Blood borne parasite - Protozoan (single celled) - (Human Granulocytic Anaplasmosis)



Blood borne parasite - Protozoan (single celled) - (Human Monocytic Ehrlichiosis)



Blood borne parasite - Protozoan (single celled) - (leishmaniasis)


What is Ixodes scapularis?

most common tick of Northeast United States


What is the vector for African Trypanosomiasis?
American Trypanosomiasis?

What disease does it cause?

Tse fly
Reduvid bug

(Chaga’s disease)


Schistosomona (bilharzia)

Nematodes and Trematodes (multicellular - worms)


With Blood borne parasite - what is the typical vector? What is the host? Where does reproduction usually occur?

ticks (Ixodes scapularis in the Northeast United States), and specific flies (e.g. Tse fly - African Trypanosomiasis) and other arthropods (e.g. Reduvid bug - American Trypanosomiasis)

Humans are "intermediate host"

Sexual reproduction usually occurs in the vector


What causes malaria? What type or organism?

In Africa what is the vector?

protozoan parasites of the genus Plasmodium

Mosquito - (Anopheles gambiae)


Why is malaria resurging?

appearance of drugresistant
strains of the parasite


What is Plasmodium falciparum?

most predominant (single celled protozoan) parasite species (Plasmodium) that causes malaria in africa - particularly lethal form of malaria


What is Anopheles gambiae?

Mosquito vector that transmits Plasmodium falciparum


What factors determine the intensity of transmission of malaria?

parasite, vector, human host, and the
environment. (e.g. climate in africal allows anopheles (mosquitoes) to reproduce all year long)


When to vector species of anaphales transmit parasites?

night time


What are the 2 most common plasmodium species that cause malaria?

Plasmodium falciparum and Plasmodium vivax

Falciparum is most lethal

4 species total that carry malaria:
o Plasmodium falciparum
o Plasmodium vivax
o Plasmodium malariae
o Plasmodium ovale


What causes the clinical symptoms of malaria?

schizont rupture and destruction of erythrocytes


What is malarial paroxysm? What causes it? What are the symptoms?

string of recurrent attacks

rupturing of the erythrocytes can occur every 48 or 72 hours

fever (>92% of cases), chills (79%), headaches (70%), and diaphoresis (64%).


Pt. presents with redcurrant attacks of fever, chills, diaphoresis, headache, tachycardia, jaundice, pallor, orthostatic hypotension, hepatomegaly and splenomegaly and has symptoms of dizziness, malaise, myalgia, abdominal pain,
nausea, vomiting, mild diarrhea, and dry cough

What is likely Dx? What caused it?

Malaria - anophales mosquito vector carrying plasmodium protozoan parasite (falciparum or vivax)


What is the method of reproduction and life cycle of a plasmodium protozoan parasite? Which cells does it infect first? What are the ultimate cells it infects?

plasmodium are sprorozoan protozoans that form schizonts - meaning they divide by schizogony to form daughter cells.

Life cycle has 3 stages: gametocytes, sporozoites, and merozoites

Gametocytes within a mosquito develop into sporozoites

sporozoites are transmitted via the saliva of a feeding mosquito to the human bloodstream

Sporozoites then infect liver cells and mature into schizonts , which rupture and release merozoites into the blood stream and infects RBS


When is malaria lethal?

If it causes cerebral malaria, pulmonary edema,
acute renal failure, severe anemia, and/or bleeding.


What are the most common metabolic complications from malaria?

Acidosis and hypoglycemia


what is significant about the PfEMP-1 Antigen?

PfEMP-1 Antigen is a distinctive feature of P. Falciparum mediated malarial infection. The surface of a P. falciparum trophozoite (a growing stage of a plasmodium merozoite once it's infected RBCs) modifies the infected RBS so they are covered with knob-like out-growths made up of the PfEMP-1 antigen. These outgrowths become the contact points for adhesion to other host cells.


What are CD36 and chondroitin sulphate A? What disease are they relevant for?

CD36 (a major sequestration receptor on
microvascular endothelial cells)

chondroitin sulphate A (CSA - a
receptor on the placental intervillous space)

They are relavant in malaria because they allow infected RBCs (modified with PfEMP-1 Antigen) to adhere to the microvascular endothelium and placenta.


What is cerebral malaria? What causes it?

most severe neurological complication of infection with
Plasmodium falciparum

adherence of infected RBCs to brain vasculature damages endothelial cells and breaks down BBB - result is edema and can be fatal


What is placental malaria? what causes it?

pregnancy associated malaria - characterized by the accumulation of parasitized RBCs and monocytes in the placenta - leads to adverse birth outcomes likely to to inflammatory response.

infected RBCs becomes sequestered in the placental circulation, bind PfEMP-1 to CD36 on endothelial cells, damage endothelium, cuase an acute inflammatory response, extravasate from vessel and bind chondroitin sulphate A receptors the placenta


What is malarial relapse?

reactivation of the infection via hypnozoites (dormant forms of parasite) released from the liver some time later on (months - years)

P. faclciparum and P. malariae do not exhibit relapse
P. vivax and P. ovale do


What is Malaria recrudescence?

parasitemia falls below detectable levels and then later increases to a detectible parasitemia because of surviving malaria parasites in red blood cells.


What are the three main causes of Malaria recrudescence?

(1) incomplete or inadequate treatment as a
result of drug resistance or improper choice of medication, (2) an antigenic variation, or (3) multiple infections by different strains.


What is Chigas disease? What causes it?

chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi

aka American Trypanosomiasis


What is Romona's sign?

A distinctive sign of Chagas infection - swelling of the eyelids near the bite or where the feces was rubbed into the eye.


What are the three ways that Chigas is transmitted?

1) from a vector - an infected triatomine insect (kissing bug)
2) blood transfusions
3) maternal transmission to fetus


A poor Mexican pt presents with cardiomyopathy, megaesophagus, megacolon and weight loss one decade after having a resolved episode of fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, myocarditis and a unilateral palpebral and periocular swelling following a bug bite.

What pathogenic organism were they most likely infected with? What category of infectious agent does this fall in? What is the vector of transmission? How does transmission from vector to host take place? Where is the site of reproduction (i.e. intracellular or extracellular) and mechanism for reproduction?

American Trypanosomiasis (Chagas)


Infected reduviid (kissing) bugs (triatomines).

Bite human hosts to take a blood meal then release (metacyclic - no dividing) trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the wound or through intact mucosal membranes, such as the conjunctiva and invade cells. Once intracellular they differentiate into amastigotes which divide by binary fission. Amastigotes differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes where they go on to infect cells of many tissues, differentiate, multiply, etc. and cause systemic symptoms.

Unilateral palpebral and periocular swelling following a bug bite = Romana's sign

Chigas can exhibit relapse -- a period of acute infection 4–8 weeks and then long dormancy that is either asymptomatic or results in symptomatic disease

cardiomyopathy is most severe chronic symptom - can be lethal


How is Trypanosomiasis detected?

acute infection via detection in blood smear

chronic infection detected by antibodies against T. cruzi antigens - two methods required for confirmed diagnosis (ELISA, IF)


What is Toxoplasma gondii?

protozoan parasite that infects most species of warm blooded animals, including humans, and can cause the disease toxoplasmosis.


Who are at rick for developing toxoplasmosis?

congenitally infected fetuses, newborns and immunologically impaired individuals


What is the most common way to develop toxoplasmosis?

Eating undercooked, contaminated meat (especially pork, lamb, and venison)

The tissue form of the parasite (a microscopic cyst consisting of bradyzoites) can
be transmitted to humans by food.


What disease affects newborn and immune compromised individuals through eating undercooked contaminated pork, lamb, and venison?



Can toxoplasmosis be absorbed through the skin?

no, must be ingested


How is toxoplasma gondii transmitted from cats to humans?

poops have T. gondii oocysts that can be accidentally ingested by coming in contact with literboxes or anything the cat shit on. As if they weren't bad enough as is...


How does a fetus develop toxoplasmosis?

Mother becomes newly infected with T. gondii during pregnancy and passes it to fetus - The transmission risk during the first trimester pregnancy is 10 to 25 percent whereas the transmission risk is 60 - 90 percent during the third


What produces worse infant/fetus outcomes? Early (1st trimester) or late (3rd trimester) maternal T. gondii infection?

early infection is worse - can lead to miscarriage, a stillborn child, or a child born with signs of toxoplasmosis


Child is born with chorioretinitis, hydrocephalus, and intracranial calcifications - mother is asymptomatic. What could be the cause?

Toxoplasmosis from an early (1st trimester infection).

Is baby is fine at birth but later develops learning, visual, and hearing disabilities - could be from later (3rd) term maternal T. gondii infection


What is the typical presentation of a healthy adult who is infected with T. gondii and develops toxoplasmosis?

mild "flu-like" symptoms with cervical lymphadenopathy that may last for several weeks to months and then goes away


What is the most common delayed onset symptom of T. gondii?

uveitis - Toxoplasma infection creates a necrotizing chorioretinitis with varying degrees of posterior and anterior uveitis. Can lead inflammatory lesion of the retina, which resolves leaving retinochoroidal scarring. Symptoms of acute disease include: eye pain,
sensitivity to light (photophobia), tearing of the eyes, and blurred vision.


What is the leading cause of focal central nervous system disease in AIDS?

Neurotoxoplasmosis induced by immunosupression mediated reactivation of T. gondii infection

Symptoms include include fever, confusion, headache, seizures, nausea, and poor coordination - other impaired functions depending on where in the brain infection localizes

parasite remains in body in inactive state until person becomes immunosupressed


A late stage HIV patient presents with fever, confusion, headache, seizures, nausea, and poor coordination. CT shows multiple 1 - 3 cm hypodense
regions predominantly in the basal ganglia and at the
corticomedullary junction. What is the most likely Dx?



How is toxoplasmosis or latent T. gondii infection diagnosed?

Toxoplasma-specific antibodies


All of the following statements regarding malaria are true except:
a. Malarial relapse may be observed in P. vivax and ovale and is due to the parasite
becoming active after remain dormant in the liver hepatocytes.
b. All persons who contract P. vivax malaria lack the Duffy Antigen present on their red
blood cells.
c. Persons with sickle cell trait or disease are more resistant to serious malaria.
d. One way to help diagnose malaria is to carefully record the pattern of symptoms.



A 44-year-old native Nigerian who has lived in the USA for 10 years returned to visit his
family in Africa and now presents with a history of shaking chills, followed by high fever
and then profuse sweating. He states that this is the most severe case of malaria he has
ever had. His blood smear shows malaria organisms consistent with Plasmodium falciparum. Which of the following statements is true regarding P. falciparum?

a. Recurrence rather than relapse is more common with P. falciparum.

b. P. falciparum may relapse due the hypnozoites remaining dormant in the liver.

c. P. falciparum causes organ damage in the brain, lungs, and kidneys because of
adhesion of infected red cells to the endothelium of the capillaries which impairs the
microcirculation to these organs.

d. Infection with P. falciparum is less severe than the other forms of malaria.



Blood banks in Southern California and Texas have done studies to evaluate how often blood containing Trypansoma cruzi is found in their blood donor pool. They have found that the incidence varies between 1:8,000 to 1:40,000 donors. If you were making up a list of questions to ask blood donors, which of the following questions would be least helpful in screening to exclude this organism from persons that have grown up in an
endemic area?
a. Have you ever been bitten by a reduvid bug?
b. Have you ever eaten pigs, dogs, or other animals that are reservoir hosts for Chagas
c. Have you ever had swelling of your eye that lasted more than 3 days?
d. Have you ever had a blood test positive for Chagas disease?



A 42-year-old female presented with her chief complaint of “fuzzy vision” with decreased vision in the right eye for several weeks. She returned from Brazil several months ago where she had been living for the past 5 years. Ocular examination revealed a 1-2 disc diameter creamy, grayish-white, raised retinal lesion was present adjacent to several chorioretinal scars. Elevated toxoplasmosis IgG levels were confirmed, though the IgM antibody was not detected. What is the most likely cause of her presentation?

a. Acute toxoplasmosis due to a new infection from lamb meat
b. Reactivation of congenital chorioretinitis due to Toxoplasma
c. Reactivation of the tissue form of the parasite from a previous infection.
d. Inhalation of the oocysts while cleaning her cat’s litterbox