Identification of blood parasites, Protozoa

1. Identification of blood parasites, Protozoa

2. African sleeping sickness (African Trypanosomiasis) Causal Agents:Protozoan hemoflagellates belonging to the complex Trypanosoma brucei.  Clinical Features:Infection occurs in 3 stages.  A trypanosomal chancre can develop on the site of inoculation.  This is followed by a hemolymphatic stage with symptoms that include fever, lymphadenopathy, and pruritus.  In the meningoencephalitic stage, invasion of the central nervous system can cause headaches, somnolence, abnormal behavior, and lead to loss of consciousness and coma. 

3. Laboratory Diagnosis The diagnosis rests upon demonstrating trypanosomes by microscopic examination of chancre fluid, lymph node aspirates, blood, bone marrow, or, in the late stages of infection, cerebrospinal fluid. A wet preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained with Giemsa (or Field), and examined.  Concentration techniques can be used prior to microscopic examination.  Antibody detection has sensitivity and specificity that are too variable for clinical decisions. 

4. Trypansoma brucei ssp. in thick blood smears stained with Giemsa

5. Trypansoma brucei ssp. in thin blood smears stained with Giemsa

6. Trypomastigotes of T. brucei ssp.

7. The trypomastigote is beginning to divide

8. Tsetse fly taking a blood meal

9. Chagas Disease (American Trypanosomiasis) Causal Agent:The protozoan parasite, Trypanosoma cruzi, causes Chagas disease, a zoonotic disease that can be transmitted to humans by blood-sucking triatomine bugs. 

10. Clinical Features The acute phase is usually asymptomatic, but can present with manifestations that include fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, and myocarditis.  Romaña's sign (unilateral palpebral and periocular swelling) may appear as a result of conjunctival contamination with the vector's feces.  A nodular lesion or furuncle, usually called chagoma, can appear at the site of inoculation.  Most acute cases resolve over a period of a few weeks or months into an asymptomatic chronic form of the disease.  The symptomatic chronic form may not occur for years or even decades after initial infection. Its manifestations include cardiomyopathy (the most serious manifestation); pathologies of the digestive tract such as megaesophagus and megacolon; and weight loss.  Chronic Chagas disease and its complications can be fatal.

11. Laboratory Diagnosis Microscopic examination: of fresh anticoagulated blood, or its buffy coat, for motile parasites of thin and thick blood smears stained with Giemsa, for visualization of parasites. Isolation of the agent: inoculation in culture with specialized media inoculation into mice In certain circumstances, investigational molecular diagnostic tools, such as PCR, may be useful.

12. T. cruzi trypomastigotes in a thick blood smear stained with Giemsa

13. T. cruzi trypomastigotes in thin blood smears stained with Giemsa

15. Malaria Blood parasites of the genus Plasmodium.  There are approximately 156 named species of Plasmodium which infect various species of vertebrates.  Four species are considered true parasites of humans, as they utilize humans almost exclusively as a natural intermediate host: P. falciparum, P. vivax, P. ovale  and P. malariae. 

16. Clinical features fever and chills, which can be accompanied by headache, myalgias, arthralgias, weakness, vomiting, and diarrhea.  Other clinical features include splenomegaly, anemia, thrombocytopenia, hypoglycemia, pulmonary or renal dysfunction, and neurologic changes. The clinical presentation can vary substantially depending on the infecting species, the level of parasitemia, and the immune status of the patient.   Infections caused by P. falciparum can progress to severe, potentially fatal forms with central nervous system involvement (cerebral malaria), acute renal failure, severe anemia, or adult respiratory distress syndrome.   Complications of P. vivax malaria include splenomegaly (with, rarely, splenic rupture), and those of P. malariae include nephrotic syndrome.

17. Laboratory Diagnosis Microscopic identification is the method most frequently used to demonstrate an active infection. Morphological comparison and images of Plasmodium species Molecular diagnosis techniques can complement microscopy, especially in species identification. Antibody Detection can detect past (not necessarily active) infections. Immunologic/Biochemical detection of malaria parasite products are available and under evaluation. Bench aids for Malaria

18. Ring-form trophozoites of falciparum P.

19. trophozoites falciparum P.

20. Gametocytes of P. falciparum

21. P. vivax Ring-form trophozoites

22. Trophozoite P. vivax

23. Schizonts of P. vivax

24. Macrogametocytes of P. vivax

25. Anopheles Mosquito

26. Leishmaniasis Causal Agent:Leishmaniasis is a vector-borne disease that is transmitted by sandflies and caused by obligate intracellular protozoa of the genus Leishmania Human infection is caused by about 21 of 30 species that infect mammals. 

27. Clinical Features Human leishmanial infections can result in 2 main forms of disease, cutaneous leishmaniasis and visceral leishmaniasis (kala-azar).  The factors determining the form of disease include leishmanial species, geographic location, and immune response of the host. 

28. Cutaneous leishmaniasis Cutaneous leishmaniasis is characterized by one or more cutaneous lesions on areas where sandflies have fed. Persons who have cutaneous leishmaniasis have one or more sores on their skin.  The sores can change in size and appearance over time.  They often end up looking somewhat like a volcano, with a raised edge and central crater.  A scab covers some sores.  The sores can be painless or painful.  Some people have swollen glands near the sores (for example, in the armpit if the sores are on the arm or hand

29. Cutaneous leishmaniasis

30. Visceral leishmaniasis Persons who have visceral leishmaniasis usually have fever, weight loss, and an enlarged spleen and liver (usually the spleen is bigger than the liver).  Some patients have swollen glands.  Certain blood tests are abnormal.  For example, patients usually have low blood counts, including a low red blood cell count (anemia), low white blood cell count, and low platelet count.  Some patients develop post kala-azar dermal leishmaniasis.  Visceral leishmaniasis is becoming an important opportunistic infection in areas where it coexists with HIV.

31. Laboratory Diagnosis Examination of Giemsa stained slides of the relevant tissue is still the technique most commonly used to detect the parasite. Isolation of the organism in culture Antibody detection can prove useful in visceral leishmaniasis but is of limited value in cutaneous disease

32. Leishmania spp. amastigotes

34. Sandfly

35. Thank you Dr. Ayham Abulaila