Microbiology 18 - Trypanosomes PDF

Microbiology Parasitology Trypanosomes Microbiology| Trypanosomes Contents : Trypanosoma brucei 5 Trypanosoma cruzi 23 Microbiology| Trypanosomes Are hemoflagellates. Disease: trypanosomiasis is a vector-born disease. Habitat: live in the blood and tissues of their human hosts. Trypanosoma brucei Mi...

Microbiology Parasitology Trypanosomes Microbiology| Trypanosomes Contents : Trypanosoma brucei 5 Trypanosoma cruzi 23 Microbiology| Trypanosomes Are hemoflagellates. Disease: trypanosomiasis is a vector-born disease. Habitat: live in the blood and tissues of their human hosts. Trypanosoma brucei Microbiology| Trypanosomes Trypanosoma brucei has three subspecies : 1. Trypanosoma brucei: T. B. Gambiense and T. B. Rhodesiense cause sleeping sickness in man. 2. Trypanosoma cruzi: causes south american trypanosomiasis or chagas’ disease. The vector is tsetse fly (glossina spp.). Microbiology| Trypanosomes Trypanosoma brucei Gambiense : Geographical distribution T. B. Gambiense occurs in west and central africa. Habitat: it inhabits: 1. Connective tissue spaces of the various organs. 2. The reticular tissue of the lymph nodes and spleen. 3. The intercellular spaces in the brain. 4. Lymph channels throughout the body. 5. Blood and cerebrospinal fluid. Microbiology| Trypanosomes Morphology : In the blood of the vertebrate host: It occurs in three forms (polymorphic). A long slender form having a flagellum, a short stumpy one without a flagellum, and an intermediate one. Microbiology| Trypanosomes Morphology : In fresh blood the trypanosomes: Motile, colourless, spindle-shaped bodies. The nucleus is large, oval and central in position. Kinetoplast (parabasal body and blepharoplast) is situated on the posterior end. Microbiology| Trypanosomes Life cycle : T. B. Gambiense passes its life cycle in two hosts: 1- development in man and other vertebrate hosts (other animals) During the act of feeding, of the vector tsetse fly (glossina spp.). Introduces the metacyclic trypomastigotes (short and stumpy),into the mammalian host in saliva injected into wound. They transform into long slender forms and multiply by binary fission at the site of inoculation. Microbiology| Trypanosomes These then transform first into an intermediate stage then into a non-dividing short stumpy form with no free flagellum. Subsequently, the parasites invade the blood stream, resulting in parasitaemia. Trypomastigotes (short and stumpy) ⟶ long slender ⟶ intermediate stage ⟶ short stumpy (no flagella). Microbiology| Trypanosomes The long slender forms are able to penetrate the blood vessel endothelium and invade extravascular tissues including the central nervous system (CNS). Microbiology| Trypanosomes 2- development in invertebrate host (vector) Uninfected tsetse fly bites and take short stumpy forms. In the midgut of the insect it develops into long slender forms and multiply, they continue to multiply for some days. They then migrate forwards the salivary glands. Microbiology| Trypanosomes In the salivary glands they develop into epimastigotes (nucleus is posterior to the kinetoplast) and attach to the cells of the glands. The epimastigote divide and transform into non-dividing metacyclic forms, which are highly motile, short and stumpy. Metacyclic forms detach from the salivary gland and are infective to the vertebrate host (20 days). Microbiology| Trypanosomes Microbiology| Trypanosomes Pathogenicity : T. B. Gambiense causes African trypanosomiasis (west African sleeping sickness). It is chronic in nature lasting up to 4 years. 1- chancre (3–4 cm) develops at the site of bite. (Fluid contain trypomastigotes). Resolves spontaneously within 1–2 weeks. Microbiology| Trypanosomes 2- then the trypomastigotes spread throughout the entire body. Move through the blood and lymphatic vessels and multiply rapidly. First associated with intermittent recurring fever and lymphadenopathy. Winterbottom’s sign: lesion in the cervical lymph nodes of the neck. Hepatosplenomegaly. Microbiology| Trypanosomes 3- if untreated Infection of CNS. Trypomastigotes enter the subarachnoid space and then the brain. At this stage, patient develops severe headache. Behavioral changes include aggressiveness and sleeping. The patient falls asleep while eating, standing or sitting (sleeping sickness) and dies. Microbiology| Trypanosomes Laboratory diagnosis : 1. Direct microscopy (unstained and stained films): look for trypomastigote forms in blood, lymph node, bone marrow, cerebrospinal fluid aspirate. 2. Concentration methods (thick blood film): haematocrit tube centrifugation coupled with microscopic examination. 3. Culture: cultivation in NNN medium (Novy-MCNeal-Nicolle). Microbiology| Trypanosomes 4. Serologic techniques: Indirect fluorescent antibody test. Indirect haemagglutination test. Enzyme-linked immunosorbent assay (ELISA). Card agglutination test for trypanosomes (CATT). These tests detect antibody in the sera. Microbiology| Trypanosomes Treatment : Pentamidine: early stage of disease. Eflornithine: late stage of the disease. Microbiology| Trypanosomes Trypanosoma brucei Rhodesiense : Occurs in east africa. The habitat and morphology: identical to those of t. B. Gambiense. Its life cycle is also similar to that of t. B. Gambiense. The disease: (east african sleeping sickness) is similar to that of t. B. Gambiense. Treatment: suramin. Trypanosoma cruzi Microbiology| Trypanosomes Trypanosoma Cruzi (Chagas Disease) : It occurs in central and south America. Habitat It lives as trypomastigote in the blood. Amastigote in reticuloendothelial cells of man and mammals (spleen, liver, lymph nodes, bone marrow, and myocardium) and CNS. Morphology: occur in two forms 1. Trypomastigote forms. 2. Amastigote forms. Microbiology| Trypanosomes 1- Trypomastigote forms Present in the blood of the patient during the early acute stage. In stained slide it take c-shape. It has a central nucleus and a large kinetoplast situated at the posterior end. Two forms occur in the blood, a long slender one and a short broad one. Microbiology| Trypanosomes Microbiology| Trypanosomes Amastigote forms These are round or oval in shape. Have a large nucleus and a kinetoplast. The amastigote forms are collected within a cyst-like cavity in the invaded cells. Microbiology| Trypanosomes Life cycle : 1- development in reduviid bug Bugs feed on infected animal and takes trypomastigote. Which transform to amastigotes in the foregut and multiply by binary fission. Transform into epimastigote stage in midgut and multiply in the hindgut. Epimastigotes attach to the epithelium, transform to metacyclic (infective) trypomastigotes. Go with faeces of the bug. The development of t. Cruzi in the vector takes around 10–15 days. Microbiology| Trypanosomes 2- development in man Trypomastigotes enter the human through the wound of the bugs bite. The trypomastigotes invade cells near the site of inoculation, where they differentiate into intracellular amastigotes. The amastigotes multiply by binary fission. Differentiate into trypomastigotes, and then are released into the circulation. Microbiology| Trypanosomes Trypomastigotes Infect Cells From A Variety Of Tissues (Reticuloendothelial System, CNS) And Transform Into Intracellular Amastigotes In New Infection Sites. Bloodstream Trypomastigotes Do Not Replicate(Different From The African Trypanosomes). Replication Resumes Only When The Parasites Enter Another Cell Or Are Ingested By Another Vector. The Bugs Take The Trypomastigotes, And The Cycle Continue. Microbiology| Trypanosomes Microbiology| Trypanosomes Pathogenesis of Chagas Disease : 1- Acute infection is marked by the development of localized swelling and erythema at the site of the insect bite, (chagoma). This is a result of the local replication of parasites and the influx of fluid and inflammatory cells into the infected area. Microbiology| Trypanosomes Romana’s sign: Infection through the conjunctiva can result in periorbital swelling. Lymphatic drainage: result in activation and proliferation of cells, resulting in regional lymphadenopathy. the amastigotes transform into trypomastigotes, escape host cells and disseminate throughout the body. Microbiology| Trypanosomes 2- In chronic infection tissue parasites are difficult to detect significant interstitial fibrosis occurs, Cardiac involvement include fibrosis within the heart muscle damaging the affected tissue. In the gastrointestinal tract, chronic infection leads to parasympathetic denervation, resulting in massive dilatation of the esophagus and/or colon. Microbiology| Trypanosomes Diagnosis : 1. Microscopic examination for a blood film. 2. Culture the blood on NNN (Novy-MCNeal-Nicolle) media. 3. PCR. 4. Immunoassay. 5. animal inoculation Microbiology| Trypanosomes 6. Xenodiagnosis: In xenodiagnosis, colony-bred uninfected reduviid bugs are fed on a suspect host and dissected about 20–25 days, later to detect epimastigotes in the faeces, hemolymph, hindgut, and salivary glands of the bugs. 7. Intradermal test: After intradermal inoculation of extract of T. cruzi culture (cruzin), a delayed hypersensitivity reaction is seen. Microbiology| Trypanosomes Treatment : Nifurtimox and benznidazole may be used for the treatment of American trypanosomiasis.