VIII. Protozoan Diseases

1. VIII. Protozoan Diseases A. Basic Properties of Protozoa B. Amebiasis C. Primary Amebic Meningoencephalitis D. Giardiasis E. Trichomoniasis F. Balantidiasis G. Toxoplasmosis H. Malaria I. Cryptosporidiosis J. Pneumocystosis

2. VIII. A. Basic Properties of Protozoa • Cellular properties • Eukaryotic microorganisms having animal-like cells • No cell walls • Most have heterotrophic metabolisms • A few protozoa (eg Euglena) are photosynthetic

3. VIII. A. Basic Properties of Protozoa • Cellular properties (cont.) • Many are free-living in soil or aquatic environments; a few are parasitic • Single-celled or simple colonial organization • Classification based predominately on the mechanism of motility

4. VIII. A. Basic Properties of Protozoa • Classification • Class Sarcodina • Motile by pseudopodia & amoeboid movement • Amebas, radiolaria, and foraminifera • Examples: • Amoeba • Entamoebahistolytica • Naegleriafowleri

5. VIII. A. Basic Properties of Protozoa • Classification (cont.) • Class Mastigophora • Motile by flagella • Examples: • Euglena • Giardialamblia • Trichomonasvaginalis

6. VIII. A. Basic Properties of Protozoa • Classification (cont.) • Class Ciliophora • Motile by cilia • Examples: • Paramecium • Balantidiumcoli

7. VIII. A. Basic Properties of Protozoa • Classification (cont.) • Class Sporozoa • A class of parasitic protozoa • Most have complex life cycles with both sexual & asexual stages • Adult forms are nonmotile • Examples: • Plasmodium • Toxoplasma gondii

8. VIII. A. Basic Properties of Protozoa • “Trophozoite” and “Cyst” • Some protozoa go through different stages in their life cycle. • This is especially true of certain parasitic protozoa. • Trophozoite: Actively growing and reproducing stage • Cyst: A dormant stage, enclosed in a resistant cyst coat

9. VIII. B. Amebiasis • Cause: Entamoeba histolytica • A parasitic ameba; class Sarcodina • Transmitted via contaminated food & water • Cysts are shed in the feces • When ingested: Excystation occurs in the intestine • Trophozoites grow & reproduce in the intestinal tract

10. VIII. B. Amebiasis • Symptoms • Abdominal pain • Little diarrhea but often blood in the stool (“amebic dysentery”) • Possibly of intestinal ulceration; perforation; infection of internal organs such as liver & lungs

11. VIII. C. Primary Amebic Meningoencephalitis • Cause: Naegleria fowleri • A fresh water, free living ameba • No cyst stage • Several cases of infections in swimmers • Transmission and Symptoms: • Transmission through the nasal & sinus passages • Infection of the brain & meninges • Headaches; delirium; seizures

12. VIII. D. Giardiasis • Cause: Giardia lamblia • A flagellate of class Mastigophora • The trophozoite has four pairs of flagella & two nuclei; giving it a face-like appearance • Grows in the intestinal tract • Cysts are shed in the feces

13. VIII. D. Giardiasis • Transmission and Symptoms • Transmitted via contaminated water & food • Foul-smelling profuse diarrhea • Sometimes chronic • Often misdiagnosed • Diagnosis via microscopic examination • Enterotest capsule

14. VIII. E. Trichomoniasis • Cause: Trichomonas vaginalis • Flagellate of the class Mastigophora • No cyst stage • Transmission & Symptoms • Transmitted via sexual contact • Genital itching • Painful urination with a white, mucoid discharge • Occasional reduction of sperm count or erosion of the cervix

15. VIII. F. Balantidiasis • Cause: Balantidium coli • Ciliated, in Class Ciliophora • Trophozoites grow in the intestinal tract • Cysts are shed in the feces and may remain embedded in intestinal walls, causing chronic infections • Transmission & Symptoms • Contaminated water & food • Ulceration in intestines • Profuse diarrhea

16. VIII. G. Toxoplasmosis • Cause: Toxoplasma gondii • In Class Sporozoa • Both asexual & sexual stages • Invasion of several areas of the body, including internal organs & muscle tissue • Possibly the most prevalent protozoan parasite of humans

17. VIII. G. Toxoplasmosis • Transmission & Symptoms • Transmitted via eating contaminated meat • Cysts are found in the meat, especially of grazing animals such as cattle • Cats can transmit the disease through their feces • Lymph node swelling; flu-like symptoms

18. VIII. G. Toxoplasmosis • Transmission & Symptoms (cont.) • Generally mild in non-immunosuppressed persons • Severe infections in immunosuppressed persons • Pregnant women are in danger of fetal damage or miscarriage

19. VIII. H. Malaria • Cause: Plasmodium species • In Class Sporozoa • Complex life cycle requiring two hosts: a mammal (human) and the mosquito Anopheles

20. VIII. H. Malaria • Transmission and Symptoms • The asexual merozoite stage infects human blood from the bite of a mosquito • The parasite invades erythrocytes & reproduces • Erythrocytes break open & release the parasite; this causes the characteristic fever, chills, anemia, weakness, hemorrhaging • Intense fever & chills about 48 - 72 hr after exposure, due to the simultaneous rupture of so many erythrocytes

21. VIII. H. Malaria • Transmission and Symptoms (cont.) • The sexual stage of Plasmodium develops in the human host and is picked up by a mosquito • The sexual stage is completed in the salivary gland of the mosquito to complete the cycle • Treatment by quinine & other antimalarial drugs

22. VIII. I. Cryptosporidiosis • Cause: Cryptosporidium species • In class Sporozoa • A common protozoan parasite in humans • Transmission and Symptoms • Contaminated water • Mild diarrhea in non-immunosuppressed persons • Severe diarrhea in immunosuppressed persons

23. VIII. J. Pneumocystosis • Cause: Pneumocystis carinii • Usually classified as a protozoan of class Sporozoa, but recent evidence suggests that it may be a fungus • Transmission and Symptoms • Transmitted by airborne contact • Usually asymptomatic or with mild respiratory symptoms • Causes severe pneumonia in immunocompromised persons • A major secondary infection & cause of death in AIDS patients