Parasitology Final Exam

What are some epidemiological factors for Babesia microti?

-Avoiding exposure to tick infested habitats -use repellent on skin and clothing -Limit the amount of skin exposure (using appropriate clothing) -Walk in the center of hiking trails

What are some epidemiological factors for Toxoplasma gondii?

-Estimated that 1/4 of the global population is infected; CDC approximates that 60 million of them are in the US -Eating undercooked meat of animals harboring tissue cyst -Countries where raw meat is popular may have higher prevalence -Eating food or water contaminated with oocyst -Transplacentally from mother to fetus -Blood transfusion or organ transplantation

What is the epidemiology of N. fowleri?

-In the US, there have been 145 PAM infections since 1962; only 4 survivors -Water forced into nasal passages from diving or water sports -Nasal exposure to contaminated water -Naegleria found in freshwater, soil, ponds, canals, lakes, heated swimming pools, freshwater aquariums, sewage -It is sensitive to chlorine -Cannot be infected from drinking water

What are epidemiological factors for the spread of plasmodium spp.

-Reservoir hosts (tolerant individuals and primate) -Vector (anopheles mosquito) -Human to human blood transmission via transfusion/needle sharing -Vertical transmission

What are some epidemiological factors for Cryptosporidium parvum?

-Swallowing recreational water contaminated with Crypto -Eating undercooked food contaminated with crypto -touching surfaces contaminated by stool from an infected person -Can be found in swimming pools -Estimated 748,000 cases of cryptosporidiosis occurs each year in the US -People with decreased immunity are most at risk for severe disease -Occurs in young children both immunocompetent and immunodeficient -Parasite is resistant to chlorine

Describe what happens in the cold stage of malarial infections

-Typical attack begins with feeling of intense cold as hypothalamus is activated -temperature rises rapidly to 104-106 degrees F -Teeth chatter and intense shivering; nausea and vomiting are usual (teeth can chip and crack from chattering)

What is the pathology of N. fowleri?

-Up to 15 days for symptoms to appear -Death within 2 weeks after symptoms appear -Initial symptoms may include: severe frontal headache, fever, nausea, or vomiting -Later symptoms include: stiff neck, confusion, lack of attention, loss of balance, seizures, and hallucinations -Causes primary amoebic meningoencephalitis (PAM) -Case fatality rate over 97% -Usually diagnosed after death

What is the pathology of Toxoplasma gondii?

-Widely prevalent in humans worldwide; but clinical toxoplasmosis is less common. -Healthy people usually asymptomatic; some experience flu-like symptoms -premunition; resistance to reinfection conferred by a still-existing infection -Serious opportunistic infection of AIDS patients; continuous tachyzoite multiplication -Congenital toxoplasmosis -Increases risk-taking behavior: men and car accidents, women and promiscuity, rats and fearlessness of cats -Patients have slow reaction times

Describe the pathology of C. parvum

-Zoonosis; disease of animals that is transmissible to humans -Cause diarrheal disease known as cryptosporidiosis -The most common symptom of cryptosporidium is watery diarrhea -Other symptoms include: stomach cramps/pain, dehydration, nausea, vomiting, fever, weight loss -AIDS patients may have as many as 26 bowel movements per day, with a maximal stool volume of 17 liters per day. -Lasts 1-10 days in immunocompetent individuals; some asymptomatic

Describe the life cycle stages of Plasmodium that occur in Mosquitoes.

1. Female anopheles mosquito bites infected human and ingests blood containing either male or female gametocytes. 2. Microgametocyte produces 8 microgametes (exflagellation), macrogametocyte matures into 1 macrogamete. 3. After fertilization, zygote elongates to form ookinete and penetrates the gut of the mosquito. 4. Rounds up and transforms to oocyst, produces numerous haploid sporozoites 5. Sporozoites break out and wander to mosquito's salivary glands 6. Sporozoites injected into human bloodstream via mosquito blood meal

What are the two general factors leading to most major clinical manifestations of Plasmodium infections?

1. Host inflammatory response producing characteristic chills and fever 2. Anemia, arising from the enormous destruction of RBCs (iron bound in hemoglobin)

Describe the lifecycle of Cryptosporidium parvum.

1. Ingested oocyst exists in host intestine and sporozoites are released 2. Sporozoites parasitize epithelial cells of GI tract or respiratory tract 3. Asexual reproduction (Schizogony) 4. Gametogony Produces microgamont and macrogamonts 5. microgamete fertilizes macrogametes and oocysts develop; sporulates in host 6. Thick walled oocyst excreted in feces; thin-walled oocyst involved in autoinfection

Describe the lifecycle of Naegleria fowleri.

1. Trophozoite (amoeboid) stage enters nasal passages 2. Amoebas migrate along olfactory nerve into cranium 3. Flagellates can only be found in CSF

What is the lifecycle for Toxoplasma gondii?

1. Unsporulated oocysts in cat feces; takes 1-5 days to sporulate (infective) 2. Oocyst is ingested by intermediate hosts; commonly include birds and rodents 3. Sporozoites are released from oocyst and enter various tissues 4. Rapidly undergoes schizogony to form merozoites (tachyzoites) 5. Tachyzoites localize in neural and muscle tissue to form cyst (bradyzoites) 6. Definitive host is infected when eating meat containing bradyzoites; or oocyst 7. In cat intestinal epithelium, gametogony occurs, then sporogony

Which parasite was responsible for the largest parasitic infection in US history (1993)?

Cryptosporidium parvum. It caused 104 deaths and +400k infections

Explain the pathology of Congenital toxoplasmosis

Occurs when a pregnant woman becomes newly infected; damage is more severe the earlier the transmission occurs in the pregnancy. May result in: -Miscarriage -Stillborn child -Abnormal development

What percentage of the population is at risk of contracting Malaria?

Over 50% of the population

Cytoadherence, followed by sequestration along the venular endothelium, is characteristic of which plasmodium species?

P. falciparum

Sickle cell trait confers resistance to which Plasmodium species?

P. falciparum

Which species of Plasmodium is most responsible for transfusion malaria? Why?

P. malaria, due to its recrudescence (up to 53 years)

Which is the rarest malaria parasite in humans?

P. ovale

Which Plasmodium species has the most ways of invading RBCs? How many pathways of entry does it have? (No need to list them)

Plasmodium falciparum has 4 ways of entering RBCs, more than P. vivax

Which plasmodium species can acquire the highest levels of parasitemia?

Plasmodium falciparum, can reach 65%, although 25% is usually fatal

What is the most virulent Plasmodium species that affects humans?

Plasmodium falciparum; it is always serious.

What percentage of malaria cases is each Plasmodium spp. responsible for?

Plasmodium vivax - 43% Plasmodium falciparum - 50% Plasmodium malaria - 7% Plasmodium ovale is by far the rarest one

Compare quotidian, tertian, and quartan Malaria.

Quotidian: 24 hour fever cycle Tertian: 48 hour fever cycle Quartan: 72 hour fever cycle

What are paroxysms?

Rapid onset or return of symptoms or increased intensity of symptoms; it is associated with the release of merozoites from RBCs

What are the main stages in the life cycle of plasmodium and in which host they occur?

Starting from a mosquito biting an infected human: 1. Sporogonic cycle in Mosquito 2. Exo-erythrocytic cycle in Human Liver 3. Erythrocytic Cycle in Human Blood 4. Gametogony begins in Humans and finishes in Mosquito due to thermal cues; Mosquito has lower internal temperature than Humans.

Which region of Africa bears the brunt of Malaria incidence?

Subsaharan Africa: 93% of all malaria cases occur here

What are the definitive hosts of Plasmodium spp.?

The anopheles mosquito; humans are the intermediate hosts.

What is an Oocyst?

The cysti form resulting from sporogony; gives rise to many sporozoites

What does relapse mean?

The reappearance of symptoms when dormant hypnozoites in the liver are activated

What is recrudescence?

The reappearance of the disease after remission; sequestration

What does it mean to be febrile?

To have or to show signs of fever

What is the infectious stage of N. fowleri?

Trophozoite (amoeboid stage); primary stage where binary fission occurs

What is the recrudescence of P. malaria?

Up to 53 years; recall vietnam veteran example

What kind of erythrocytes does P. vivax invade?

Young erythrocytes with Duffy blood groups.

What is the definitive host of Babesia microti? Intermediate host?

blacklegged tick White-footed mouse

What is sequestration?

it is the adherence of infected RBCs containing late developmental stages of the parasite (trophozoites and schizonts) to the endothelium of capillaries and venules

What are the food sources for female and male anopheles mosquitoes?

males eat nectar, females take blood meals

Describe the sweating stage of a malarial infection.

Copious perspiration signals the end of the hot stage Temperature drops back to normal in 2-3 hours

Where can P. ovale be found?

Mostly in Africa (especially West Africa) and the islands of the western pacific

What is sporogony?

Multiple fission of a zygote

Describe the ilifecycle of Babesia microti

1. sporozoites exit salivary glands of infected tick during blood meal 2. Sporozoites enter white-footed mouse RBC and forms trophozoite 3. Erythrocytic schizogony gives rise to merozoites; cycle repeats 4. Some intraerythrocytic parasites will form gametocytes, which are then ingested by tick 5. Fertilization between male and female gamete, called ray bodies, occurs in tick gut 6. Zygote (called kinete) migrates to the salivary glands of ticks 7. Kinete develops into sporoblast that produce sporozoites *back to step 1*

After the exoerythrocytic cycle of P. vivax, how many merozoites are released?

10,000 merozoites

On average what is the yield of erythrocytic schizogony in P. vivax?

16 merozoites

The erythrocytic schizogony of P. falciparum yields how many merozoites on average?

22 merozoites

How many Malaria infections were there in 2018? How many deaths?

228 million infections; 400k deaths

What percentage of the world population is infected with Toxoplasma gondii?

25% of the global population

The recrudescence of disease caused by P. falciparum may follow remission up to how many years?

3 years

How many merozoites are released from liver cells after the exoerythrocytic cycle of Plasmodium falciparum?

30,000 merozoites

How many stagest does N. fowleri have?

3: cyst, amoeboid and flagellate

How long do paroxysms generally last?

6-10 hours; patient sleeps well until the next episode

How many nuclei does the schizont stage of P. ovale have?

8 nuclei

What is an ookinete?

A motile, elongated zygote

What is a hypnozoite?

A trophozoite in a liver cell that doesn't want to finish the exoerythrocytic cycle; it is dormant or quiescent

Which 2 plasmodium species have hypnozoites? A. Plasmodium Vivax and Plasmodium ovale B. Plasmodium vivax and Plasmodium malariae C. Plasmodium falciparum and Plasmodium ovale D. Plasmodium falciparum and Plasmodium malariae E. Only plasmodium falciparum

A. Plasmodium vivax and Plasmodium ovale

Describe the life cycle stages of Plasmodium that occur in Humans.

After Sporozoites are injected into human blood stream through blood meal: 1. Sporozoites invade parenchymal cells of liver; exoerythrocytic schizogony occurs (asexual multiplication). Only ONE ROUND OF THIS! 2. Tiny merozoites rupture out of each schizont from liver cell and invade RBCs 3. Within RBCs, erythrocytic schizogony occurs; RBCs rupture, releasing merozoites that can now infect more RBCs 4. After patient becomes clinically ill, merozoites invade RBCs and give rise to gametocytes (18-24 days after initial infection) 5. Gametocytes continue to circulate in blood stream, within RBCs. They are now in developmental arrest until they re-enter mosquito. 6. Once ingested by mosquito, gametocytes transform into gametes (gametogony), followed by sexual fusion. 7. Subsequent development into sporozoites through sporogony.

How many species of anopheles mosquito are there? How many can transmit Malaria? How many do it regularly?

Approximately 430 anopheles species About 100 can potentially transmit Malaria Only 30-40 transmit it regularly

How many calories does a single acute day of fever require?

Approximately 5,000; this is about 2 day's worth of hard manual labor

Approximately 94% of malarial related deaths occur in: A. South America B. Africa C. Asia D. Central America E. Australia

B. Africa

What kind of fever cycle does Plasmodium vivax have?

Benign tertian malaria (48 hour cycle)

What is the common name of Naegleria fowleri?

Brain eating amoeba

What are Macrogametocytes?

Cells that give rise to macrogametes; female

What are Microgametocytes?

Cells that give rise to microgametes; male

List the 3 stages of malarial pathology

Cold stage Hot stage Sweating stage

A patient arrives at the clinic with a 72 hour fever cycle and has recently been to the tropics on vacation. What species of plasmodium is the patient infected with? A. Plasmodium falciparum B. Plasmodium vivax C. Plasmodium ovale D. Plasmodium malariae E. Plasmodium idonowee

D. Plasmodium malariae; it is the only one that has a 72 hour fever cycle

Which of the following is not associated with Cryptosporidium parvum? A. Low host specificity B. Opportunistic infection C. Zoonosis D. Vector is mosquito E. All of the above

D. vector is the mosquito

What is the pathology of Babesia microti?

Healthy people usually asymptomatic; some experience flu-like symptoms Babesiosis can result in severe pathogenicity in the following people: -splenectomized -compromised immune system -Elderly -Complications include severe hemolytic anemia (hemolysis)

Describe what happens in the hot stage of malarial infections

Hot stage begins 30 minutes to 1 hour later, with intense heat and headache Often a mild delirium stag lasts for several hours

What is the definitive host for Cryptosporidium parvum?

Humans; no intermediate hosts needed. Direct lifecycle.

Where do most malaria cases occur?

In Africa where there isn't much food available

What are some additional pathological signs of plasmodium infection?

In addition to chills, fevers, and anemia, other symptoms may include: -splenomegaly -other fatal complications

Where is Plasmodium vivax mostly found?

In asia, Latin America; common in North Africa but drops off in tropical Africa

What is a Schizont?

In schizogony, when nuclear divisions have occurred but not cytokinesis. Can be considered the "mother" cell that gives rise to merozoites. Multiple nuclei are visible within the cell prior to cytokinesis.

When does the sporogenous phase begin?

It begins when the ookinete begins to develop

Where may Plasmodium malaria be found?

It can be found worldwide in tropics and subtropics, but the distribution is not continuous.

When considering P. vivax, what happens if a cell does not have Duffy group receptors?

It cannot be infected with P. vivax

What is a merozoite?

It is a daughter cell resulting from schizogony; the end product of schizogony

What is a sporozite?

It is a daughter cell resulting from sporogony

What is Schizogony?

It is a form of asexual reproduction in which multiple mitoses occur, followed by simultaneous cytokinesis. Results in the formation of many daughter cells at the same time

What is gametogony?

It is a process by which gametes are produced in protozoa; occur when merozoites entering RBCs transform into gametocytes

What is a trophozoite

It is the active, feeding stage of a protozoan, in contrast to a cyst

What does parasitemia mean?

It is the presence of parasites in the circulating blood; ~25% is considered high levels of parasitemia

What is cytoadherence?

It is the property of P. falciparum-infected RBCs to adhere to various host cell types such as endothelial cells and uninfected red cells

Naegleria fowleri is an opportunistic parasite. What does this mean?

It means that it is free-living, until it gets the chance to parasitize a human; low host specificity

What kind of fever cycle does Plasmodium falciparum have?

Malignant tertian malaria (48 hours)

What are the definitive hosts of Toxoplasma gondii?

Members of the family Felidae (includes domestic cats)

Which kinds of RBCs can P. malaria invade?

Merozoites of P. malaria can only invade aging RBCs, soon to be removed from circulation

When thinking about Macro- and microgametes, which one fertilizes which?

Microgametes fertilize Macrogametes; male fertilizes female

What kind of fever cycle does Plasmodium ovale have?

Mild tertian malaria