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Apicomplexa and malaria


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Describe the definitive organelle of the apicomplexa.
The apicoplast is a double-walled organelle similar to a chloroplast thought to be derived from algae.
How many cases of malaria appear annually in the US? How many prescriptions are written each year for malaria prophylaxis?
*1000 cases/year
*100,000 prescriptions/year
What is the vector for malaria? Is it a definitive or intermediate host for the parasite?
*female Anopheles mosquitos
*definitive host
What occurs during the prepatent period of malaria infection?
*parasite multiplies in liver
What is seen in the paroxysm phase of malaria infection? What causes this?
*shaking chills, high fever, sweating
*infected RBC burst and release merozoites which induces a large immune response
Name 3 means of diagnosing malaria.
1. Geimsa stain of thick or thin smears
2. Rapid antigen tests
3. Travel history and clinical presentation
What kinds of RBC's does P. falciparum invade?
*RBC of all ages
What morphology is unique to P. falciparum?
Sickle-shaped gametocytes.
What is the periodicity of P. falciparum?
48 hours
What form of malaria is both the most common and the most dangerous?
P. falciparum
What kinds of RBC's do P. vivax and P. ovale invade?
*enlarged, immature reticulocytes
What is a diagnostic sign that is unique to infection by P. vivax or P. ovale?
Schuffner's dots.
Why are patients infected by P. vivax or P. ovale prone to relapse?
Formation of hypnozoites which remain dormant in the liver for months or years.
What is the periodicity of infection by P. vivax or P. ovale?
48 hours
Why might patients infected by P. malariae be prone to relapse?
The parasite may persist in the bloodstream at very low levels.
What is the periodicity of infection by P. malariae?
72 hours.
What are the characteristics of malaria in areas of high transmission?
*high exposure to bites
*adults are generally immune
*disease seen in children and pregnant women
*some immunity present
What are the characteristics of malaria in areas of low transmission?
*low exposure to bites
*adults and children become sick
*no native immunity
What stages of P. falciparum are visible in circulation? Which are not and why?
*Rings and gametocytes visible
*trophozoites and schizonts not seen because expression of sticky knobs on RBC surface causes sequestration
What is a dangerous complication of infection by P. falciparum? How does this occur?
*cerebral malaria
*trophozoite forms secrete proteins that cause sticky knobs on RBC surface
*RBC adhere to cerebral capillaries and cause blocks
What is a "schizont"?
A multi-nuclear intermediate involved in the asexual reproduction of plasmodium spp.
Describe the sexual reproduction of apicomplexa.
Merozoites differentiate into gametocytes which then unite to form oocysts.
Describe the life cycles of plasmodium spp. through its vector.
*gametocytes are ingested by mosquito during a blood meal
*formation of sporozoites which live in the salivary glands of the mosquito
*tranferred to host upon next blood meal
Name three drugs commonly used for malaria prophylaxis and a drawback for each.
1. Chloroquine - high resistance
2. Lariam - neuropsychiatric side effects
3. Doxycycline - photosensitivity
4. Malarone - expensive, must be taken daily
Other than drugs, what is the best prohylaxis against malaria?
Personal protection against mosquito bites though clothing, DEET, and bed nets.
What is the preffered treatment protocol for malaria at UNC hospitals?
Quinine and tetracycline.
Name three genetic conditions that actually confer resistance against malarial infection.
1. Sickle cell anemia
2. Thalassemia
3. Duffy blood group negative
4. G6P dehydrogenase deficiency
Where in the US is babesiosis endemic?
In the northeast.
What is the vector of babesiosis? What is its host?
*vector is a tick
*host is the white-footed mouse
What is the clinical course of babesiosis?
A mild flu-like illness.
What cell type in humans does babesia invade?
What two patient populations are susceptible to complications in babesiosis?
Splenectomized patients and elderly.
What is the definitive host of Toxoplasma gondii? How is the parasite transferred from this host?
*tranferred in fecal oocysts
Name two ways humans can acquire a T. gondii infection.
1. exposure to fecal oocysts
2. ingestion of oocysts in contaminated meats
Name three cell types that T. gondii is able to inhabit in humans.
*intestinal epithelium
What is the seroprevalence of T. gondii in the US? Why might it be higher in France?
*22% in the US
*more ingestion of raw meat products
What is the clinical presentation in acute infection by T. gondii? What viral infection does it resemble?
Mild flu-like febrile illness that resembles mononucleosis.
Describe the effects of T. gondii primary infection of a pregnant woman in the first trimester.
Congenital toxoplasmosis resulting in malformations, ocular disease, and mental retardation.
What are the effects of T. gondii primary infection of a pregnant woman in the second or third trimester?
Spontaneous abortion
Why are AIDS patients prone to acute toxoplasmosis? Name 2 serious complications of infection of this population.
*immune suppression allows reactivation of latent infection
*retinal lesions and encephalitis
What medication is used as T. gondii prophylaxis in AIDS patients?
What are two means of diagnosing T. gondii infection?
*serological tests
*innoculation/culture of mice
What animal typically hosts cryptosporidium? When was it first seen in humans?
What are the common symptoms of infection with cryptosporidium? What patient population is at risk for a more severe clinical course?
*mild to moderate diarrhea
How is cryptosporidium usually acquired? How is the parasite well-adapted to this mode of transmission?
*drinking water, swimming pools, food
*cysts are chlorine-resistant
What are the two types of cryptosporidium? Which is generally associated with outreaks and which with sporadic cases?
*C. hominis - infects humans only, associated with outbreaks
*C. parvum - infects cattle and humans, associated with sporadic cases
Cyclosporiasis is similar to which other parasite in appearance and illness? What is this course of this illness?
*mild to moderate diarrhea
What is the animal reservoir of cyclospora?
Cyclospora has no animal reservoir.
North American outbreaks of cyclosporiasis are associated with what food product?
Imported fruits, especially raspberries.

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