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?
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*1000 cases/year
*100,000 prescriptions/year - What is the vector for malaria? Is it a definitive or intermediate host for the parasite?
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*female Anopheles mosquitos
*definitive host - What occurs during the prepatent period of malaria infection?
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*asymptomatic
*parasite multiplies in liver - What is seen in the paroxysm phase of malaria infection? What causes this?
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*shaking chills, high fever, sweating
*infected RBC burst and release merozoites which induces a large immune response - Name 3 means of diagnosing malaria.
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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?
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*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?
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*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?
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*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?
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*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.
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*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.
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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.
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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?
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*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?
- RBC
- 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?
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*Felines
*tranferred in fecal oocysts - Name two ways humans can acquire a T. gondii infection.
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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.
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*macrophages
*fibroblasts
*intestinal epithelium - What is the seroprevalence of T. gondii in the US? Why might it be higher in France?
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*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.
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*immune suppression allows reactivation of latent infection
*retinal lesions and encephalitis - What medication is used as T. gondii prophylaxis in AIDS patients?
- SMX-TMP
- What are two means of diagnosing T. gondii infection?
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*serological tests
*innoculation/culture of mice - What animal typically hosts cryptosporidium? When was it first seen in humans?
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*cattle
*1976 - What are the common symptoms of infection with cryptosporidium? What patient population is at risk for a more severe clinical course?
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*mild to moderate diarrhea
*HIV/AIDS - How is cryptosporidium usually acquired? How is the parasite well-adapted to this mode of transmission?
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*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?
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*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?
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*cryptosporidium
*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.