Flagellate. All are pathogenic

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1 Flagellate Are those protozoa which are provided with flagella? According to their habitation man body, flagellates can be grouped into three categories 1 Intestinal flagellates. 2 urogenital flagellates. 3 Blood (haemo -) flagellates. Intestinal flagellates 1.Giardia lamblia. Pathogenic (duodenum, Jejunum). 2.Embadomonas intestinalis (colon). 3.,Enteromonas hominis (colon) 4.Chilomastix mesnili (caecum) 5.Trichamonas hominis (caecum) 6.Trichomenas tenax (buccalis) (buccal cavity) Luminal flagellates are non pathogenic commensals except Geiardia lamblia Urogenital flagellates -Trichomonas vaginalis (pathogenic) in habits the vagina and prostate Blood flagellates A. Extra cellular (outside r. b. c. in the plasma) 1. Trypanosome gambinese 2. Trypanosome rhodesiense 3. Trypanosome cruzi Trypanosomal form All are pathogenic. B. Intracellular (inside r, b, cs) 1. Leishmania tropica 2. Leishmania braziliense 3. Leishmania donovarni 4. Leishmania form of T. cruzi All are pathogenic 1

2 Giardia lamblia is a flagellate of world-wide distribution. It is more common in warm climates than temporal climates. It is the most common flagellate of the intestinal tract, causing Giardiasis. Humans are the only important reservoir of the infection. The infection is most common in parts of the world where sanitation is at its lowest. Giardiasis is an infection of the upper small bowel, which may cause diarrhoea. Only Giardia spreads disease. Diagnostic morphologhy It has 2 stages the trophozoite and the cyst. Trophozoite 1. Pear shaped or heart shaped broad and rounded anterierly and tapering posterior microns. 3. Presence of aventral bilobed sucking disc which occupies almost the entire anterior half of the body. 4. With two over nucler one on each lobe of the disc, 5. Nucleus has a central karysome. 6. with 4 pairs of flagella axostyles running along the midline sausage shaped parabasal or medium bodies lying transversely, posterior to the sucking disc. Cyst 1. Oval in shape and thick welled. 2. With 4 round nuclei grouped at one pole 3. Presence of axostyles and fibrils. 2

3 Life cycle When the human ingest the cyst with contaminated food. It excyct in upper GIT and liberate trophozoites that multiply by binary fission. When the trophozoite drop off it lives in the duodenum and upper part of the jejunum, attached by means of the sucking disc to epithelial cells of the velli feeding by pinocytosis. Trophozoites which reach lower part of the small intestine or the large intestine start encystations the trophozoite retracts its flagella into the axaonemes which remain as curved bristles in the cyst. 3

4 When there is diarrhea, trophozoites are found in stools. 10 cysts being capable of initiating infection. Within half an hour of ingestion, the cyst hatch s out into two trophozoites Which multiply successively by binary fission and colonies the duodenum. The trophozoites as they pass down the colon develop into cyst. Mode of clinical picture 1 The incubation period is variable, but is usually about 2 weeks. 2 Sever diarrhea a (Steatorrhea). Stool is pale, offensive & fatty. 3 Flatulence, upper abdominal pain and tenderness. 4 Anorexia vomiting (in early stage). 5 Malabsorption, weight loss due to large number of the parasite adhering to the mucosal surface of the small intestine may interfere with absorption, competition of parasite & normal flare for nutrient. Steatorrhoea? Diagnosis The cysts and trophozoites can be found in drarrhoeal stools. 4

5 trophozoite may be recovered by duodenal aspiration. (Early stage (Late stage cyst + trophzoite) cyst). Fatty and offensive stool confirm diagnosis. Laboratory Diagnosis Cysts can be found by examination of the deposit of a formol-ether concentrate of a stool preparation. The oval cysts with thick walls serve as characteristic features for these organisms. The flagella disintegrate and form a central streak which becomes visible when stained with iodine or MIF (merthiolate-iodineformaldehyde). Cysts may be excreted intermittently; therefore it is important to examine more than one stool. Stools are usually passed 3-8 times / day and are usually pale, offensive, rather bulky and accompanied by much flatus. Trophozoites are found by examination of saline wet preparations of fresh, diarrheic stool, duodenal or jejunal aspirate or in a permanently stained faecal preparation. Trophozoites can also be found in the jejunal aspirate. These can be recovered by the String Test or Enterotest capsule and the material examined microscopically for motile trophozoites. Trophozoites and cysts can be found to be scarce in chronic infections. Serological methods of diagnosis are proving to be useful as means of diagnosis. An ELISA to detect IgM in serum provides evidence of a current infection. A polyclonal antigencapture ELISA can be used to demonstrate submicroscopic infections in faeces and an IgA-based ELISA will detect specific antibodies in saliva. Treatment Metronidazole and tinidezole are the drugs of choice. 5

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8 Trichomods are widely distributed, there are three human species. 1 T. vaginalis of the vagina (only pathogen) 2 T. hominis of the intestine heavy Caused diarrhea. 3 Tenux of the mouth. They may be differentiated site of origin. T. vagnalis is a sexually transmitted flagellate. Members of both sexes are equally susceptible to this infection, but women tend to remain infected for longer periods of time. Trichomonas vaginelis is a common sexually transmitted infection it was described by Donne 1836 regarded as a commensal 1837 describe vaginalis infection Trichomonas vaginalis is role as a primary phages of human urogenital tract is now undisputed. Therapy of human trichomoniasis was inadequate until the 1960 when metrenidozol (and derivatives) were found. Diseases.. Trichomonal virginities, urthritis, prestatovesiculitis Mode of infection 1 Sexual transmission: it is the most prevalent. 2 Bathing water. 3 Contaminated cloths. Epidemiology.. The incidence of infection is about % in Women it is higher in groups in which feminine hygiene is deficient. Morphology T.vaginalis occurs only as the trophozoite, there being no cystic form in trichomonas. The tropthozoit is a void or pear shape with a short undulating membrane reaching up to the middle of the body. It has 4 anterior flagella and a fifth running along the margin of undulating membrane., 8

9 Which is supported at its base by a flexible rod, its Costa? A prominent axostyle runs throughout the length of the body and projects posterior. The cytoplasm shows prominent granules which are most numerous alongside the axostyle and Costa. Life cycle.. After infection with T.vaginalis the trophozoite live in close association with, and at times even attached to the epithelium of the urogental tract. The normal habitats are the human vagina in the female host, the organism typically feeds on the mucosal surface of the vagina ingesting bacteria and leukocytes and at times being phagocytosed by macrophage. In male T.vaganilis habitats in urethra, epididymis and prostate hence it is frequently found in the urine. T.veginalis divides by longitudinal binary fission which is initiated by division of the nucleus followed by division of neuromotor apparatus and finally separation of the cytoplasm into two daughter organisms. Note the trophozoite is one of the most resistant of the parasitic protozoa. It loses its vitality below ph.4.9 hence it cannot live in the normally acid vaginal secretion ph. 3.8 to 4.4 of healthy adults. 9

10 Pathology & symptomatology.. The causative agent is responsible for a low grade inflammation by its toxic action on cells and production of viginitis. The bacterial flora and the physiologic status of the vagina including ph. Are among the factors that determine infection. Hyperemia & petechial hemorrhages. In a advanced Cases granular area. The surface is covered with creamy or yellowish discharge. Vaginal and cervical inflammation itching and burning. In male there may be arthritis and prostatovesiculitis. Diagnosis 1 Clinical diagnosis is based on symptoms. 2 The microscopic examination in a drop of saline for motile trichomonads of the fresh vaginal discharge. Obtained with a speculum on cotton tipped applicator and dipped in normal saline Solution is the most practical method of diagnosis. Cultures will reveal the organism when microscopic examination is negative. 3 Prostatic secretion following prostatic massage and urine of the male should be examined. Acridin orang staining : looking for morphology of parasite by Note... Giemsa station 1- Care should be taken to prevent contamination to the specimen with feces since T. hominis may be seen and misdiagnosed as T. vaginalis. 11

11 2 If more than 10 minutes has passed since the collection & specimen motility can often be increased by incubation the sample at for a few minutes. Treatment 1 Metronidazales (flagyl). 0.5 gm twice daily for (5) days 2 Acidifying agents (as lactic acid) used as I table spoon in I liter warm water. For mild Restoration of normal acid PH of the vagina will suppress trichomonas below PH silver picrate use Habitat. The vagina especially when vaginal secretion is less acid than normal (average ph 5.5). Cervix, uterus or the urethra, urinal bladder In it may inhabit the urethra, urinary bladder, prostate and seminal vesicle. Pathogenesis and symptomatology In female the patient feeling itching in the external genitals: Burning sensation and frequency of urination. Milky yellowish exudates from the vagina. In male Infection is generally asymptomatic. When symptoms occur, they consist of burning sensation during urination, accompanied with a yellowish discharge from the urethra. If infection extends to posterior urethra and prostate, urethritis becomes chronic. Trachomas homins Carries 5 anterior flagella and undulating membrane that extends the full length of the body. It is a very common harmless commensal of the Caecum. 11

12 Undulating membrane with a free trailing posterior end. The semi rigid axostyle with a spiked posterior end protruding through the posterior portion of the cytoplasm. Thick Costa that extends the full length of the undulating membrane. Trichomonas tenax It is a harmless commensally which lives in the mouth. This is smaller than T. vaginalis. 12

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14 Blood flagellates C. Extra cellular (outside r. b. c. in the plasma) 4. Trypanosome gambinese 5. Trypanosome rhodesiense 6. Trypanosome cruzi Trypanosomal form All are pathogenic. D. Intracellular (inside r, b, cs) 5. Leishmania tropica 6. Leishmania braziliense 7. Leishmania donovarni 8. Leishmania form of T. cruzi All are pathogenic Leishmania (leishmaniasis).. Lieismaniasis was first described in 1903 by Leishman and Donovan both of these physicians separately demonstrated parasite stained smears from the spleen of patients suffering from a malaria like illness.. Which become known as visceral Leishmaniasis? What is leishmaniasis. Is a parasitic disease spread by the bite of infected female sand flies (phlebotomies SPP.) there are several different form of Leishmaniasis. The most common form are coetaneous Leishmaniasis which cause skin sores. And visceral Leishmaniasisl which effects some of the internal organs of body (spleen, liver, bone marrow). Classification 1 Viscerel Leishmaniasis (VL) -Leishmania donovani complex -L. d. donovani -L. d. infantum - L. d. chagas and others 14

15 2 Cutaneous Leishmansiasis. -L. Tropica miner dry cutaneous Leishmaniasis. -L. Tropica major wet cutane0us Leishmaniasis. -L. aethiopica anergic cutaneous Leishmaniasis. 3 mucocutaneous Leishmaniasis. -L. braziliensis complex M. C. L. -L. Mexicana - The vector is female sand flies (phlebotomus) - Infective stage promastigotes - Diagnostic stage. Amastigotes which is the reservoir of infection that present in animal reservoir host. In human RES 1 histocyte multiply within these macrophage 2 monocyte Mode of transmission 1 Bite of sand fly. 2 Blood transfusion. 3 Direct transmission from person to person in infected secretion during sexual intercourse Morphology.. There are two forms of the parasite, the intracellular amastigote form found in the vertebrate host (ex. human) and the promastigote form found in the vector...amastigotes are spherical in shape within a macrophage there is a prominent nucleus and kinetoplast and the cytoplasm is vacuolated and contains Lysosomes nor surface coat. 15

16 Intracellular amastigote Mononuclear phagocyte Containing amastigote" Amastigote Promastigotes. The surface membrane has finding site molecules such us glycoprotein and manose receptors have also been detected. These are important in the uptake of promastigotes by the macrophages. antibodies in the host serum bind to the promastigotes and facilitate uptake and entry into the macrophages. the macrophage having fc receptors on their surface. Flagellum (leptomonad) Elongated and fusiform and the flagellum originating from the kinetoplast which lies anterior to the nucleus. The glycoproteins that are refractory to host Lysosomal enzymes and may also destroy them. Once the protozoan has entered the vacuole it transforms into the amastigote form and undergoes binary fission. Lifecycle The infection in usually transmitted by the bite of female sand flies -The promastigotes are inoculated by bitting. 16

17 -These bind and penetrate macrophage (histiocyte if cutaneous and kuffer s cells if visceral) -Inside macrophage the promastigotes change into amastigotes that able to multiply inside macrophage. - The presence of large number of amastigotes in side of infected cells lead to increase pressure so the infected cells rupture and release these amastigotes into skin or visceral cavity. The rupture of infected cells provides organisms to be phagocytosed by other cells that may spread the infection to other organs or more distant sites (depending upon the infecting species or the immune status of the host). Temperature is one important factor that may determine locolizotion of Leishmanial lesions. -The sand fly take up these with its blood meal. -In sid the sand fly the amastigote begin to multiply by simple fission. and become elongated, fusiform and a flagellum appears, originating from the kinetoplast which lies anterior to the nucleus. the blood from clotting Sand fly into wound to prevent 17

18 Visceral Leishmaniasis (Kala - azar) Is a disease caused by aprotozoan complex called Leishmania donovani. LD body 3species Ecological types.. the epidemiology and clinical features of visceral Leishmaniasis and the ecology of the parasite are very different in different geographical areas the 3species are 1 L. infantum.. Mediterranean middle Easten Leishmaniasis.. affecting mostly young children.. it s a zoonotic disease. 2 L. donovani.. Indian visceral Leishmaniasis the disease is not zoonotic man being the only host and reservoir. 3 L. chagasi.. in parts of south & central America.. The disease is zoonotic. Kala azar.. meaning black sickness.. fever of tropical splenomegaly. incubation period.. is very variable, usually 3 18 months (occasionally as short as 2 weeks) the parasite may persist in the body in a dormant 18

19 state for many years, only to emerge when the hosts immunity wanes for any reason. Stages of the Disease responses A Initial response.. is the initial stage in which there is a cellular reaction due to local multiplication of injected promastigotes that lead to formation of a definite nodule. when such a lesion forms it is called Leishmanioma which varies with geographical strains of Leishmaniasis. -The cells found in the Lesion are macrophages, Lymphocytes and plasma cells but the effective is specialized killer cells -If the cell mediated immunity (CMI) response is poor the a mastigotes multiply rapidly inside macrophages Leading to rupture of parasitized cells, become disseminated through the body. They are taken up by phagocytic cells of RES and visceral stage is established B Clinical Established visceral Leishiraniasis. 1 Fever.. due to generalized infection usually of slow or subacute onset sweating is prominent. (fever) Its irregular and intermittent at first, later become remittent. 2 Splenomagly. Starts early and is progressive and massive. 3 hepatomegly due to increase in kuffer cells. 4 Swelling of Lymph gland.. -The disease progresses for several month. With periods of pyrexia followed again by fever.. -Eimaciation and anaemia develop. -The skin become dry, rough and darkly pigments (the name kala - azor). -Epistaxis and bleeding gums are common..about % of patients who recover develop post kala-azar dermal Leishmaniasis (PKDL). 19

20 . Pathological changes Kala-azar is a reticuloendotheliosis resulting from the invasion of the RES by L. donovoni Parasitized macrophages disseminate the infection to all parts of the body in the spleen, liver, and particularly bone marrow. The a mastsgotes multiply enormously in the fixed macrophages this lead to a marked proliferation of RE Tissue in these organs -the spleen.. most affected.. it is grossly enlarged and the capsule is frequently thickened due to perisplenitis Lymphocytic infiltration is scanty but plasma cells are numerous. -The livers.. the Kupffer cells and vascular endothelial cells are heavily parasitized, prothrombin production is commonly decreased. -The bone marrow is heavily infiltrated with parasitized macrophages which may crowdout the hoemopoietic tissues. -Peripheral lymph nodes and Lymphoid tissues of nasopharynx and intestine are hypertrophic due to infiltration with parasitized cells. Blood changes 1-Totalglobulin level increase more than 4-5g/dl due to high level of IgG.. because antigenic increased by amastigotes. 2-Albumine level falls..lead to oedema. 3-Anaemia..(normochromic,normocytic) due to the secondary hypersplenism initially, later there may be marrow depression reflected low reticulocyte count. 4- leucopenia (granulocytopenia) due to. splenic in origin. Effect of parasite on bone WBC.less 3000\ ml or 2000\ ml Low count. eosinophil. Platelet 5- The eosinophil count is invariably low. 21

21 6-The platelet count is low which may lead to purpura..bleeding especially from gums epistaxis -Note; strong granulomatous reaction around parasites indicates high level of CMI, is a good prognostic feature, but in Kala-azar this granul response is minimal. -The untreated disease is fatal,death may occure with few weeks or after 2years or more. Immunity The most important immunological feature in Kala-azare is the marked suppression of cell mediated immunity to Leishmanial antigens this makes possible the unrestricted intracellular multiplication of the parasite. In contrast, there is an overproduction of immunoglobulins lgg and lgm Patients who have recovered from the infection are considered immune to reinfection. Laboratory Diagnoses 1 Direct diagnosis. For microscopic demonstration of parasite the materials collected. a) Peripheral blood. b) Bone marrow. c) splenic aspirate. *peripheral blood contains the amastigotes present inside circulating monocytes and less in neutrophils, but the numbers are so scanty that a direct blood smear may not show them. -thick blood film. -best to examine buffy coat smear. Even these are not often found positive. 21

22 *Bone marrow aspirate is the most common diagnostic specimen collected generally the sternal marrow is a spirated by puncturing the sternum at the level of the 2 nd or 3 nd intercostals space (painful.. need local anesthesia) after disinfecting the needle is introduced into the sternal marrow and about 0.5 ml of marrow fluid aspirated using syringe. *Spleen aspirates are richer in parasites and more valuable for diagnosis.. fix the spleen between 2 hands, dry small intramuscular needle (2 ml syringe) is inserted, -Suction and Immediately with drown. -fix the contents on clean slide by 100% formal to avoid drying if parasite.the specimen is stained by Giemsa (you can inoculate this sample in NNN media or in animal ). Amastigote parasites (LD bodies) can be seen within macrophages. Culture are made on Novy MacNeall Nicolle (NNN) medium this is rabbit blood Agar Having an overlay of Locke s' solution with added antibiotics (penicillin, streptomycin, gentamicin). Bacto agar 14 gm Nacl 6 gm H 2 O distilled 900 ml NaOH 0.1 N solution Rabbit or guinea pig dafibrinated 10 ml Animal inoculation is not used for routine diagnosis, where necessary humster is the animal employed. the materials are inoculated intraperitoneally or intradermally into the skin of nose and feet. 2 Indirect diagnosis (Immunodiagnostic) It is called indirect since it demonstrates some thing produced due the response to parasite (Abs). Or as parasitic products (Ags). Demonstration of Abs (the majority).. Diagnosis of visceral leishmaniasis based on serology is made less reliable due to.. 22

23 1) Not 100 % specific (cross - reaching) because the antigen is crude has many antigenic determinants that not merely specific for Leishmaniasis. -cross reaction with malaria, toxoplasmosis and T.B. 2) Low sensitivity (70 80%). 3) The time between infection and appearance of Abs is imperfect (may be already infected by Leishmaniasis Abs not detectable). 4) Persistence of Abs after treatment (after recover the Abs still of high titer). A-demonstration of Abs(the majority) *Indirect fluorescent antibody test (IFAT). The IFAT is one of the most sensitive test available. the test is based on detecting antibodies Which are demonstrated in the vary stages of infection and undetectable six to nine month after care. if the antibodies persist in low titers it is good indication of a probable relapse. Titer above 1/20 are significant and above 1/128 are diagnostic there is a possibility to a cross reaction with trypanosomal sera, however. *Direct agglutination test (DAT). The DAT is a highly specific and sensitive test it is cheep and simple to perform making it ideal for both field and laboratory use the antigen is prepared from pramastigotes of L. donevani and test can be carried out on plasma, Serum, blood spots whole blood. serum titers of 1 : 3200 are considered positive. *Enzyme linked immunosorbent assay (ELISA). The antigen is prepared from promastigotes of L. Donovan and the test can be performed on serum, plasma or blood spots collected on filler paper it is useful in the field owing to its simplicity. B.Antigen demonstration; Advantages..Less cross reaction no persistence after treatment- very representive of infection by methods..pcr(polymerase chaine reaction) 23

24 *formal gel test. (cicumstantiol diagnosis) Its mainly chemical interaction rather than immunodiagnosis its simple when positive. hyperglobulinaemia what over its cause (so not specific for visceral Leishmanisis) to 1 ml of serum in a test tube in added one drop of (40 % formeldehyde) then shake the tube to mix thoroughly after 20 minutes of room temperture the serum becomes firm, opaque jelly (like a cooked egg whit) if the test is the positive Cutaneous Leishmaniasis.. The clinical and epidemiological patterns vary from region to region. Morphology and life cycle.. of these species resemble those of L. donovani the amastigotes are present in the skin, within large mononuclear cells, in neutrophil, in side capillary endothelial cells. They are ingested by sandflies feeding near the skin lesions. In the midgut of the sand fly, the amastigotes develop into promastigotes which replicate these are inturn transmitted to the skin of persons bitten by the sand flies. In the skin the promastigotes are phagocytosed by the mononuclear cells, in which they become a mastigotes and multiply. However they remain confined to the skin, Without being transported to the internal organs as in the case (visceral leishmaniusis). - The common mode of infection Sand flies...some times occurs by direct contact... Man to man or Animal to man.. Autoinoculation --Some times the Sand fly may act as a mechanical vector into wound The lesion may be... Single dry Lesion.Wet exudates Lesion..Diffuse coetaneous Lesion (multiple). Test for diagnosis. 24

25 1) Skin Scraping. to see intracellular or extracellular a mastigotes. a) Use scalpel gently to scrap the skin collect the sample from periphery of the area of redness, inflammatory reaction where the parasite are still alive. b) Try to collect fluid rather than blood because there is scanty parasites. 2) Immunoassay. Not helpful because the Immune response in this case is cellular not humoral even if there are some Abs. 3) Leishmanin or montenegro test Inject 0.1 ml of a suspension of killed promastigotes intradermally in one arm (A) & inject normal saline in other arm (B) and put a circle around the site of injections. Wait for about 22h then see if there is redness slight swelling and rash on arm (A) positive result. Post Kala-azar dermal Leishmaniasis (PKDL).. It s a macular or nodular skin eruption, localized or widespread of very varied appearance.. *occurance.. it occur after chemotherapy of visceral. Leishmaniasis or less often after spontaneous recovery. Cause it is caused by presence of large number of amastigotes within the skin. It is most common after Kala-azar where it froms the only reservoir of infection. Treatment it may respond to long courses of treatment with stibogluconate. In some cases it may persists for several years before finely resolving spontaneously. 25

26 Treatment of kala-azar -Sodium stibogluconate (10 20 my/kg) each day for 30 days. -hydroxy stilbamidine isethionate (3 4.5 mg/kg) per day for 10 days 7 day rest between three course. Notes 4 Secondary infections complicate visceral Leishmaniasis. 1) Pneumonia. 2) Dysentery (bacillary dysentery). 3) Dysentery due to entamoeba histolytic. 4) T. B. TRYPANOSOMA (TRYPANOSOMIASIS) Three Trypanosomes of medical importance: Trypanosoma gambiense : the causative of gambian Trypanosomiasis ( west and central African sleeping sickness ) Trypanosoma rhodesiense : the causative of Rhodesian Trypanosomiasis ( east African sleeping sickness) Trypanosoma cruzi : the causative of American Trypanosomiasis ( chagas disease ). Mode of transmission By the bite of the tsetse fly ( genus Glossino ). ( cyclopropagative) 26

27 Mechanical transmission ( direct ) Intermediate host.. Glossina palpalis for T. gambiense Glossina morsitans for T. rhodesiense Morphology and life cycle Infection is acquired by the bite of the vector tse tse The infection form of the parasite is the metacyclic trypomastigote. The parasite proliferates initially at the site of inoculation and then through the lymphatic, enters the blood stream. Elongate trypomastigote form in mid gut of tsetse fly Epimastigote in salivary gland which develops into Metacyclic trypomastigote In the blood three forms of trypanosomes are found ( poly-morphic) the long slender trypomastigote(4), a short broad stumy form with flagellum attenuated or absent(6), and an intermediate form.(5) Spindle shape bodies that more rapidly (in fresh blood films) in smears stained with giemsa or other romanowsky stain the cytoplasm 27

28 appear pale blue and the nucleus red. The kinetoplasts appear as a deep red dot. The undulating membrane appears pale blue and the flagellum red. When a vector tsetse fly feeds on person with parasitaemia. It takes in the trypomastigotes along with it blood meal, (particularly the short broad forms). These become long slender forms in the mid gut and hind gut of the fly. (Both sexes of tsetse feed on blood). In the stomach (mid & hind gut) of fly the parasite multiply by simple fission penetrate the gut wall and migrate to the salivary glands. Here they become broad Epimastigotes which multiply and fill the cavity of the gland. The fly become infective when the Epimastigote become transformed into Metacyclic trypomastigote. It takes about 3 weeks from the time of the blood meal for the fly to become infective one, the fly remain infective for life. The trypanosomes remain extracellular throughout its life cycle, both in the vertebrate and in the vector. Antigenic variation Trypanosomes exhibit antigenic variation of their surface glycoprotein (the process by which selective pressure by Abs on the parasite population is followed by change in antigenic mak-up ) it explains the fluctuating nature of the illness. Pathogenesis The lymphatic system is the main site of infection The disease has: 1- invasion stage 2- sleeping stage In skin just after injection of trypanosomes, trypanosoma chancres which are tender nodules are formed this is a hot, raised, inflamed area (resemble a blind boil). It appears 3 or more days after the bite and increase in size for 2-3 weeks, at the end of which time it begins to regress. Trypanosomes are found in the blood soon after the 28

29 development of chancre Invasion of lymphocytic is accompanied by fever, enlargement of lymph nodes especially the cervical lymph gland (posterior triangles) postcervical group Winter bottom's sign When the C.N.S is involved, sleeping stage is reached and accompanied with leptomeningitis. In general T. gambiense is well tolerated and the illness it causes tends to be subacute or chronic and parasitaemia may be asymptomatic. (T. gambiense is better adapted to human than T. rhodesiense ) So infection with T. rhodesiense runs a more acute course Splenomegaly (moderate). Molt morula cell (retractile eosinophil are found) Clinically: change in behavior becomes careless about his appearance Sleep disorder: sleeps badly at night, fall asleep during the day. Death occurs within few months. Immune response After initial infection, the parasitaemia typically rises, followed by Abs production ( mainly IgM ), when the Abs reach effective level in destroying the parasite the parasitaemia rapidly falls, and the parasite disappear from the circulation.later the parasitaemia recurs, but this generation of parasite has deferent antigenic mak-up from previous population this second wave of parasitaemia is also terminated by Abs. The whole process is repeated many times. Diagnosis Trypanosomes may be recovered from chancres. Blood film ( most useful for T. rhodesiense ) Gland puncture ( most useful for T. gambiense ) CFS examination 29

30 Aspiration from chancre before the blood positive Treatment Suramin + pentamidine are used for early cases. Melarsoprol. Effective in late cases South American Trypanosomiasis ( chagas disease ) Caused by Trypanosoma cruzi. Morphological forms Trypomastigote in blood Amastigote in RES and other tissue Epimastigote in mid gut of winged bug Life cycle T.cruzi passes the life cycle in two hosts including man and the insect (vector) reduviid bug - ( triatoma megista ) night biting bugs which typically defecate while feeding, the faeces of infected bugs contains the metacyclic trypomastigote which are the infective form.the parasite enter the lymphatic system and go inside cells ( RES & other tissue ) and transformed into Amastigote ( leishmanoid forms ) which divided by binary fission, after passing through Promastigote & Epimastigote forms, they again become trypomastigote which are release into blood stream.(no multiplication occurs in the trypomastigote stage). Multiplication take place only intracellular in the Amastigote form, when a bug bites a person with trypomastigote are transformed into Epimastigote which migrate to hind gut and 31

31 proliferate. These in turn develop into metacyclic trypomastigote which are excreted in faeces (stercorarian transmission). Mode of transmission Stercorarian transmission (through faeces of the bug contain trypomastigote via hand of patient of site of injury. ( bite wound by hand persons fingers cause mucosal surface, particularly the conjunctiva ) Fresh blood transfusion Clinical feature The heart is the main organ involved myocarditis may produce heart failure. On skin primary lesions as a result of invasion by trypanosomes is called (chagoma). Oedema of eye lids and of one side of the face with unilateral conjunctivitis ( romana's sign ) may be noticed 3 weeks after infection. The disease chiefly affects children and appears in 2 clinical pictures (acute) in children under 1 year and (chronic) in relative older children up to 15 years. Diagnosis Blood examination: T.cruzi with large kinetoplast, central nucleus and flagellum. Serological test (detection of include complement fixation, haemagglutination test) 31

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