Apicomplexa: Parasites and Opportunistic Infections

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Questions and Answers

Which of the following genera infect humans?

Seven genera, including Plasmodium, Babesia, and others (correct)

Only Toxoplasma and Sarcocystis

Only Plasmodium and Babesia

All protozoan parasites

What is a characteristic of the life cycles of Apicomplexa?

Only asexual reproduction

Complex life cycles with both sexual and asexual reproduction phases (correct)

Only sexual reproduction

No reproduction phases

What is the role of humans in the life cycle of Apicomplexa?

Only as definitive hosts

Only as intermediate hosts

Neither as intermediate hosts nor definitive hosts

Both as intermediate hosts and definitive hosts (correct)

How many species of Plasmodium cause human malaria?

5 Signup and view all the answers

Which Plasmodium species has the widest geographic distribution?

P. vivax Signup and view all the answers

What percentage of infections are caused by P. vivax and P. falciparum?

95% Signup and view all the answers

Which Plasmodium species is associated with the most deaths in underdeveloped countries?

P. falciparum Signup and view all the answers

How many deaths occur annually worldwide due to malaria?

1 million to 2 million Signup and view all the answers

What percentage of erythrocytes may be infected with P.falciparum?

Up to 50% Signup and view all the answers

What is a common complication of P.malariae infection?

Nephrotic syndrome Signup and view all the answers

What is a characteristic of blackwater fever?

Hemoglobinuria Signup and view all the answers

What is a result of high-level parasitemia with P.falciparum infection?

Anemia Signup and view all the answers

What is a complication of P.falciparum infection?

Cerebral malaria Signup and view all the answers

What is a consequence of P.malariae infections?

Recrudescence Signup and view all the answers

What is the typical duration of the fever stage in a malarial paroxysm?

2 to 4 hours Signup and view all the answers

Which of the following is a possible route of transmission for malaria?

Transplacental infection Signup and view all the answers

What is a result of tissue anoxia in P.falciparum infection?

Tubular necrosis Signup and view all the answers

What is the term for the pigment deposited in the liver and spleen during long-term malaria infection?

Hemozoin Signup and view all the answers

What percentage of erythrocytes are infected in P.malariae infections?

2% to 5% Signup and view all the answers

What is the term for the cycle of symptoms that repeats itself at regular intervals in malaria?

Malarial paroxysm Signup and view all the answers

What is the reason for anaemia in malaria?

All of the above Signup and view all the answers

What is the purpose of calculating the level of parasitemia?

To follow the effectiveness of treatment Signup and view all the answers

What is the typical duration between the bite of an infected mosquito and the start of symptoms?

10 to 15 days Signup and view all the answers

What is the role of the female Anopheles mosquito in the life cycle of Plasmodium?

Definitive host and biological vector Signup and view all the answers

Which of the following is NOT a symptom of the prodromal phase of the paroxysm?

Diarrhea Signup and view all the answers

Which species of malarial organisms are generally associated with fewer complications?

P. vivax and P. ovale Signup and view all the answers

What is the purpose of RBC exchange in cases of high-level parasitemia?

To decrease the level of parasitemia and increase the effectiveness of the drug Signup and view all the answers

What is the earliest stage of human infection by Plasmodium?

Ring-form trophozoite Signup and view all the answers

Where does the exoerythrocytic phase of the life cycle of Plasmodium occur?

Liver Signup and view all the answers

What is the result of the schizogony phase of the life cycle of Plasmodium?

Production of merozoites Signup and view all the answers

How do humans acquire Plasmodium infection?

Through the bite of an infected female Anopheles mosquito Signup and view all the answers

What signals the beginning of the erythrocytic phase of the life cycle of Plasmodium?

Release of mature merozoites from liver cells and invasion of RBCs Signup and view all the answers

What is the method of diagnosing malaria that uses a fluorescent dye?

QBC system Signup and view all the answers

What type of smears are examined to identify the species of malaria?

Thin smears Signup and view all the answers

How many oil immersion fields should be examined before considering a smear negative?

200 to 300 Signup and view all the answers

What type of tests use monoclonal antibody directed against an antigen specific to P. falciparum?

RDTs Signup and view all the answers

What is the purpose of examining multiple sets of smears within a 36-hour period?

To rule out the presence of malarial organisms Signup and view all the answers

What is the advantage of nucleic acid amplification tests?

They are sensitive in detecting low levels of P. falciparum infection Signup and view all the answers

What is the principle used in RDTs?

Antigen capture immunochromatographic principle Signup and view all the answers

What type of protein is detected by some RDTs?

Histidine-rich protein Signup and view all the answers

Study Notes

Apicomplexa Phylum

Includes blood and tissue parasites that represent age-old pathogens and newly recognized agents of opportunistic infection
Seven genera infect humans: Plasmodium, Babesia, Cryptosporidium, Cyclospora, Isospora, Sarcocystis, and Toxoplasma

Plasmodium spp.

Cause malaria, which is endemic throughout the world in tropical and subtropical countries
Estimated 300 million to 500 million individuals are infected
Four species of Plasmodium cause human malaria: Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium falciparum
A fifth species, Plasmodium knowlesi, causes malaria in macaque monkeys and has been implicated in cases of zoonotic human malaria in Malaysia and the Philippines

Malaria

Major cause of death in underdeveloped countries, with annually between 1 million to 2 million deaths worldwide primarily due to P. falciparum infection
Death in children who have malaria is also significantly associated with P. falciparum infection
P. vivax has the widest geographic distribution and is the species most likely to be found in temperate climates
P. vivax and P. falciparum cause more than 95% of infections

Clinical Infections

Usually transmitted through the bite of an anopheline mosquito, but can also be transmitted through blood transfusion and infected needles
Transplacental infection has also been documented
The malarial paroxysm, which begins 10 to 15 days after the bite of an infected mosquito, is associated with the growth of the parasites in RBCs and high levels of cytokines
Symptoms are linked to the rupture of RBCs and release of merozoites, malarial metabolites, and endotoxin-like substances into the bloodstream

Life Cycle

Involves sexual reproduction (sporogony) and asexual reproduction (schizogony)
Sporogony is the formation of oocysts containing sporozoites that results from the division of a zygote
Schizogony produces merozoites by the process of multiple fission
The female Anopheles mosquito serves as the biological vector and definitive host

Laboratory Diagnosis

Examination of Giemsa-stained thick and thin smears remains the classic method of diagnosing malaria
The thick smear is used to detect malarial parasites, while the thin smear is used to identify the species
Trophozoites, schizonts, and gametocytes may be seen in the blood smear
At least 200 to 300 oil immersion fields should be examined on either type of smear before the smear is considered negative
Nucleic acid amplification tests and immunoassays (RDTs) are other methods for diagnosing malaria

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Description

Learn about the phylum Apicomplexa, including its diverse morphology, transmission methods, and complex life cycles. Understand how seven genera infect humans, including Plasmodium, Babesia, and Toxoplasma.