1. BLOOD AND INTESTINAL PROTOZOA
QUICK REVIEW

2. Plasmodium species (P. vivax, P. ovale,
P. malariae, & P. falciparum)
Disease—Malaria.
Characteristics—Protozoan that infects red blood cells and tissue, eg, liver, kidney, and brain. Transmission and Epidemiology—Transmitted by female Anopheles mosquitoes. Occurs primarily in the tropical areas of Asia, Africa, and Latin America.

3. Pathogenesis_Merozoites destroy red cells, resulting in anemia
Pathogenesis_Merozoites destroy red cells, resulting in anemia. Cyclic fever pattern is due to periodic release of merozoites. Plasmodium falciparum can infect red cells of all ages and cause aggregates of red cells that occlude capillaries. This can cause tissue anoxia, especially in the brain (cerebral malaria) and the kidney (blackwater fever). Hypnozoites can cause relapses.

4. Laboratory Diagnosis_Organisms visible in blood smear
Laboratory Diagnosis_Organisms visible in blood smear. Thick smear is used to detect presence of organism and thin smear to speciate.

5. Treatment Chloroquine if sensitive. For chloroquine resistant P
Treatment Chloroquine if sensitive. For chloroquine resistant P. falciparum, use mefloquine or quinine plus doxycycline.
Primaquine for hypnozoites of P vivax and P ovale. In severe cases, use parenteral guanidine or quinine.
Prevention Chloroquine in areas where organisms are sensitive. For those in areas with a high risk of chloroquine resistance, mefloquine or doxycycline. Primaquine to prevent relapses

6. Toxoplasma gondii
Disease—Toxoplasmosis, including congenital toxoplasmosis.
Characteristics—Tissue protozoan. Life cycle: Cysts in cat feces or in meat are ingested by humans and differentiate in the gut into forms that invade the gut wall.

7. Transmission and Epidemiology—Transmitted by ingestion of cysts in raw meat and in food contaminated with cat feces

8. Pathogenesis—Trophozoites infect many organs, especially brain, eyes, and liver.
Cysts persist in tissue, enlarge, and cause symptoms. Severe disease in patients with deficient cell-mediated immunity, eg, encephalitis in AIDS patients.
Laboratory Diagnosis—Serologic tests for 1gM and IgG antibodies are usually used. Trophozoires or cysts visible in tissue.
Treatment—Sulfadiazine plus pyrimethamine for congenital or disseminated disease.
Prevention—Meat should be cooked. Pregnant women
should not handle cats, cat litter boxes, or raw meat.

9. A 40-year-old woman was well until 2 days ago, when she experienced the sudden onset of fever, shaking
chills, and profuse sweating. Today, she also complains of headache and abdominal pain but no nausea, vomiting, or diarrhea. She does not have a stiff neck, rash, or altered mental status. Travel history reveals she returned from an extended trip to several countries in Central Africa 1 week ago. Blood smear reveals ringshaped trophozoites within red blood cells.

10. A 20-year-old woman in her 30th week of pregnancy had an ultrasound examination that revealed a growth retarded fetus with a large head (indicating hydrocephalus) and calcifications within the brain. Umbilical
blood was cultured and crescent-shaped trophozoites were grown.

11. Which of the following has a life cycle that most closely resembles that of Plasmodium sp:
Please select the single best answer
A. Dracunculus medinensis
B. Blastocystis hominis
C. Babesia microti
D.Toxocara canis

12. How do immunocompromised individuals infected with Toxoplasma gondii present? What is the syndrome known as?

13. Answer
In immunocompromised individuals, cysts rupture and release tachyzoites that leads to toxoplasmosis. Patients present with:
Chorioretinitis
Encephalitis
Pneumonitis (rarely)
Toxoplasma is the most common cause of encephalitis in HIV patients.

14. What is the classic triad of symptoms in congenital toxoplasmosis?

15. Answer
If a pregnant woman without previous exposure becomes infected, T. gondii protozoa may cross the placenta, causing congenital toxoplasmosis.Congenital toxoplasmosis presents with the classic triad:
Chorioretinitis (cotton-like white/yellow scars on the retina)
Hydrocephalus
Intracranial calcifications (multiple ring-enhancing lesions in the cortex and basal ganglia on head CT)
Note that children can also often be born asymptomatic.

16. What additional lifecycle stage does Plasmodium vivax/ovale have
What additional lifecycle stage does Plasmodium vivax/ovale have? How does this translate into clinical disease?

17. Answer
P. vivax and P. ovale is known as ‘relapsing infection’ that occurs every 2 days, and infectsonly reticulocytes (immature RBCs).
Within hepatocytes, some sporozoites form latent hypnozoites, which can activate months to years after initial infection and cause symptomatic malaria in a relapsing fashion.

18. What is the unique effect of P
What is the unique effect of P. falciparum infection on RBCs, and what additional complications can this lead to?

19. Answer
P. falciparum trophozoites develop sticky “knobs” inside RBCs, making infected RBCs more likely to stick to capillary and venule walls. This can lead to vessel occlusion and hemorrhage, causing damage to:
Brain (cerebral malaria)
Kidneys (renal failure)
Lung (pulmonary edema)