Parasitology Introduction PDF

Introduction to medical parasitology Dr J.Mudenda  Learning Outcomes At the end of our discussions, you should be able to do the following: Define the terminology & importance of parasitology. Classify parasites of medical importance. For each parasite desc...

Introduction to medical parasitology Dr J.Mudenda  Learning Outcomes At the end of our discussions, you should be able to do the following: Define the terminology & importance of parasitology. Classify parasites of medical importance. For each parasite describe the following: 1. Geographical distribution and life cycle, 2. Mode of transmission and means of diagnosis 3. Prevention, control and treatment  Definition of parasitology Medical parasitology is the study of parasites and their pathogenic effects. Or branch of science that deals with parasites that cause human infections and the diseases that they cause. It involves the study of parasites, their hosts and the relationship between them. Humans and other living organisms live in close relationship with each other.  Importance of parasitology Inflicts significant morbidity and mortality to a huge population. 247 million cases of malaria recorded in 2021 (world malaria report 2021) 619,000 malaria deaths recorded during the same period. Neglected tropical diseases (NTDs) are a group of parasitic/bacterial infectious diseases affecting more than 1.7 billion people. Over 40% of the global NTD burden is concentrated in Africa. Amongst children, infection leads to malnutrition, cognitive impairment, stunted growth & the inability to attend school. Malaria cases at a facility in Siavonga District Parasite induced morbidity- Ascariasis/neurocystercosis  It is broadly classified into three main categories. 1. Protozoology(protozoa) 2. Helminthology(helminths) 3. Entomology(arthropods)  Medical Parasitology includes the study of 3 major groups of parasites: Protozoa Arthropods Helminths Hi I am a protozoa I like to present called One-celled my self as insects organisms and my allies Simply called Worms e.g. Glossina morsitans e.g. Giardia lamblia e.g. Ascaris lumbricoides  Terminology Parasite-A living organism which depend on another organism(host) for food and shelter. The term parasite usually applies to Protozoa(unicellular organisms) and Helminths (multicellular organisms e.g. worms). Parasites are divide as follows:- 1. Ectoparasite: inhabit the body surface of the host without penetrating the tissue e.g. Lice, ticks & mites. 2. Endoparasite: lives inside the body of the host e.g. most protozoan and helminthic parasites causing human disease are endoparasites. 3. Free-living parasite: refers to nonparasitic stages which live independent of the host e.g. the cystic stage of Naegleria fowleri.  Host -is an organism which harbors the parasite and provides nutrition and shelter. A host is usually larger than the parasite and are divided into the following:- Definitive host: An organism in which the adult forms of the parasite lives and undergoes sexual reproduction e.g. mosquito acts as definitive host in malaria. Man is the definitive host in majority of human parasitic infections, (e.g. filaria, roundworm, hookworm).  Intermediate host: is an organism in which the parasite lives during a period of development(larval stage) or where asexual multiplication takes place. In some cases 2 different intermediate hosts (first & second intermediate hosts) may be required to complete different larval stages. Reservoir host: an organism which harbors the parasite and acts as an important source of infection to other susceptible hosts e.g. dog is the reservoir host of hydatid disease.  Paratenic host: an intermediate host whose presence is needed to complete the parasite’s life cycle but in which no development of the parasite occurs. Accidental host: an organism that’s under normal circumstances not infected with the parasite. Life cycle of malaria with the mosquito as the definitive host & humans as intermediate host Habitat A habitat is where the parasite lives and multiplies in the body of the definitive or ▪ Small intestine intermediate host like: ▪ Large intestine ▪ Blood vessels ▪ Organs; liver, lung, heart, brain, ….. ▪ Muscles ▪ Lymphatics ▪ Reticulo-endothelial system ▪ Red blood cells  Zoonosis is defined as diseases and infections which are naturally transmitted between vertebrate animals and humans. Or a parasitic disease which an animal is normally the host but which also infects man. Vector: A vector is an agent or living carrier usually an arthropod that transmits an infection from man to man or from other animals to man, e.g. female Anopheles is the vector of malarial parasite. There are two types of vectors: mechanical and biological vectors. 1. Biological vectors(Also referred to as true vectors): Refers to a vector which not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well. Example of true vectors are: Mosquito—Malaria, filariasis Sandflies—Kala-azar Tsetse flies—Sleeping sickness Reduviid bugs—Chagas’ disease Ticks—Babesiosis 2. Mechanical vectors: Refers to a vector which assists in the transfer of parasitic form between hosts but is not essential in the life cycle of the parasite. Example of Mechanical vectors is: Housefly—amoebiasis  Humans and other living organisms live in a close relation with each other. This intimate interaction or living together of organisms from different species is referred as Symbiosis The three common symbiotic relationships are: Commensalism: an association in which only the parasite benefits without causing harm or injury to its host e.g most of the normal floras of the human body.  Parasitism: an association in which the parasite derives benefit and the host gets nothing in return and always suffers some injury e.g worms like ascaris lumbroicoides reside in the GIT of man and feed causing an illness. Mutualism: both organisms are metabolically dependent upon each other and one cannot live without the help of the other however none of them suffers any harm from the association e.g. the relationship between certain species of flagellated protozoa living in the gut of termites.  Epidemiology Environmental factors, social customs and habits of people greatly influence the distribution of parasites. Although parasitic infections occur globally , majority occur in tropical regions where there is: -poverty -poor sanitation and personal hygiene. -Low education standards -Inadequate nutrition Why rich nations suffer less from parasites High standards of education - better housing, higher standard of living. General good health - poor health = more susceptible to disease. Nutrition - adequate diet. Sanitation - sewers and septic systems keeps raw sewage out of streams. Temperate climate - parasites do better in the warmth of the tropics. Absence of certain vectors - intermediate hosts such as the tsetse fly, certain snails, etc.  Life cycle of parasites Direct life cycle: The parasite only requires a single host to complete its development e.g. Entamoeba histolytica requires only a human host to complete its life cycle. Indirect life cycle: In this case the parasite requires 2 or more host species to complete its development e.g. malarial parasite needs both human host and mosquito to complete its life cycle.  What are the sources of Infection 1. Contaminated soil and water Soil polluted with embryonated eggs (roundworm, whipworm) may be ingested or infective larvae in soil may penetrate exposed skin (hookworm, S.stercolaris). 2. Food(Gain entrance to the GIT): Ingestion of contaminated food or vegetables containing infective stage of parasite (amoebic cysts, Toxoplasma oocysts, Echinococcus eggs). Ingestion of raw or undercooked meat harboring infective larvae e.g. pork containing cysticercus cellulosae, the larval stage of Taenia solium, cysticercus bovis-T.saginata larval stage and T.spiralis). 3. Insect vectors: Arthropods that transmits an infection from man to man or from other animals to man, e.g. anopheline for malarial parasite, Tsetse flies for Trypanosoma, sand flies for Leishmanina,Culicine mosquitoes for Wuchereria banchroft. 4. Animals Include both domestic(Cow, e.g. T. saginata : Pig e.g. T. solium, Trichinella spiralis : Dog, e.g. Echinococcus granulosus ) and wild animals(Wild game animals, e.g. trypanosomiasis: Fish, e.g. fish tapeworm ). 5. Self (autoinfection). Finger to mouth transmission, e.g. pinworm Internal re-infection, e.g. Strongyloides Stercolaris. This results from poor personal hygiene hence the emphasis for hand washing.  Modes of transmission 1. Oral transmission: Most common mode occurring through contaminated food, water, soiled fingers, or fomites. The infective stages being cysts, embryonated eggs, or larval forms ,many intestinal parasites enter the body in this manner. 2. Skin transmission: Is another important mode of transmission. Hookworm infection is acquired, when the larvae enter the skin of persons walking barefooted on contaminated soil. Schistosomiasis is acquired when the cercarial larvae in water penetrate the skin. 3. Vector transmission: Many parasites are transmitted by insect bite, e.g., malaria by Anopheles mosquito, filariasis by Culex mosquito. 4. Direct transmission: Parasitic infection may be transmitted by person to person contact in some cases, e.g. kissing in the case of gingival amoebae and by sexual intercourse in trichomoniasis. 5. Vertical transmission: Maternal-fetal transmission occur in malaria and toxoplasmosis. 6. Iatrogenic transmission: Seen in case of blood transfusion in malaria and toxoplasmosis after organ transplantation.  Important pathogenic effects Parasitic infections may be dormant or give rise to clinical disease with a few organisms such as E. histolytica living without invading the tissue (commensals). Clinical infection produced may be acute, subacute, chronic, latent or recurrent. Pathological changes or disease mechanisms occur in the following ways:  Physical obstruction: Masses of A.lumbricoides (roundworm) cause intestinal obstruction. P.falciparum malaria may produce blockage of brain capillaries in cerebral malaria Inflammatory reaction: Inflammatory changes and consequent fibrosis e.g. lymphadenitis in filariasis and urinary bladder granuloma in Schistosoma haematobium infection cause clinical illness. Lytic necrosis: Enzymes produced by some parasite can cause lytic necrosis e.g. E. histolytica lyses intestinal cells producing amoebic ulcers.  Neoplasia: Some parasites are now classified as carcinogens or lead to malignancy. The liver fluke, Clonorchis cause bile duct carcinoma and S. haematobium may cause urinary bladder cancer. Trauma: Attachment of hookworms on jejunal mucosa leads to traumatic damage of villi and bleeding at the site of attachment-cause of anemia. Allergic manifestations: Clinical illness may be caused by host immune response to parasitic infection, e.g. eosinophilic pneumonia in Ascaris infection and anaphylactic shock in rupture of hydatid cyst  Laboratory diagnosis Whilst clinical symptoms or a case history may provide clues as to which parasite may be present, laboratory diagnosis remains key in finding the definitive diagnosis. Laboratory methods are divided into Direct and Indirect methods Direct methods involves visualization of the parasite in a particular specimen e.g. malaria parasites in RBCs , hookworm ova in stool etc. Indirect methods detect cytological changes, immune response or parasite products(antigens) without necessarily visualizing the parasite e.g. eosinophilia in worm infections or biochemical changes.  Laboratory methods include the following 1. Microscopy for blood film , stool, urine , sputum and biopsy examination. 2. Culture e.g vaginal discharge or urine for diagnosis of T.vaginalis 3. Serological test.eg in toxoplasmosis,schistosomiasis etc 4. Skin test(Immunological skin reactions) e.g in protozoa infections such as Chagas disease,toxoplasmosis and helminth infections e.g schistosomiasis(fairley’s),hydatid disease(Casoni’s). 5. Molecular methods  Xenodiagnosis Imaging(CT imaging in neurocystercosis) Hematology(eosinophilia in helminth infections)  Prevention and control Reduction of potential sources of infection Community education Destruction and/or control of reservoir hosts and vector  Treatment of parasitic infections Medical and surgical Chemotherapy Adequate nutrition  Websites of Interest There are thousands of reading resources on internet providing information and images on parasites, not all of them are as trustworthy. Two excellent sites to look for general information and visual illustrations: CDC (Division of Parasitic Diseases) WHO (Tropical Diseases Research Program) AMOEBA Dr J Mudenda  Introduction Are simple protozoans with no fixed shape & have a cytoplasm bounded by a membrane and differentiated into an outer ectoplasm and inner endoplasm. Movement and engulfment of food by phagocytosis occur by pseudopodia formed by thrusting out cytoplasm. Reproduction occurs by fission and budding. Cyst is formed in unfavorable conditions and is usually the infective form for vertebrate host (e.g. Entamoeba histolytica).  Amoebae are classified as either free-living or intestinal amoebae. The free-living amoebae occasionally act as human pathogens causing meningoencephalitis and other infections, e.g. Naegleria and Acanthamoeba. The parasitic amoebae inhabit the alimentary canal.  Classification of Amoebae Intestinal amoebae Free-living amoebae Entamoeba histolytica Naegleria fowleri Entamoeba dispar Acanthamoeba spp Entamoeba coli Balamuthia mandrillaris Entamoeba gingivalis Entamoeba polecki Endolimax nana Note: All free-living amoebae Note: All intestinal amoebae are opportunistic pathogens are non pathogenic, except Entamoeba histolytica  Entamoeba Histolytica The parasite was discovered & demonstrated in dysentery feces of a patient in St. Petersburg in Russia by Lösch in 1875. In 1891 the pathogenesis of intestinal & hepatic amoebiasis was established( 'amoebic dysentery' and 'amoebic liver abscess‘) by Councilman and Lafleur. E. histolytica strains can be classified into at least 22 strains of which only 9 are invasive and the rest are noninvasive commensals. The pathogenic & nonpathogenic strains though morphologically identical may represent 2 distinct species—the pathogenic strains being E. histolytica & the nonpathogenic strains reclassified as E. dispar. Trophozoites of E. dispar contain bacteria, but no RBCs.  Epidemiology Prevalent worldwide although much more common in the tropics. It has been found wherever sanitation is poor. Reported to affect about 10% of world population of which 50% of people in developing countries may be infected with the parasite. Majority of infected humans (80–99%) are asymptomatic. 50,000 deaths occur annually mostly in the tropical belt of Asia, Africa & Latin America. It is the third leading parasitic cause of mortality, after malaria & schistosomiasis.  Immunity Infection with invasive strains leads to both humoral & cellular Immune responses. Serological response is not seen in infection with non-invasive strains. Antibodies can be demonstrated within a week of invasive infection. Infection confers some degree of protection as evidenced by the very low frequency of recurrence of invasive colitis and liver abscess in endemic areas. Course & severity of amoebiasis does not seem to be affected by human immunodeficiency virus (HIV) infection.  Morphology E. histolytica occurs in 3 forms. 1. Trophozoite 2. Precyst 3. Cyst Trophozoite- is the growing stage of the parasite & the only FORM present in tissues. -It is large, irregular in shape & actively motile in freshly- passed dysenteric stool. -Tend to be smaller in convalescents & carriers  Trophozoites in acute dysenteric stools often contain phagocytosed erythrocytes a feature diagnostic of Entamoeba histolytica. Phagocytosed red cells are not found in any other commensal intestinal amoebae. Infection is not transmitted by trophozoites as they are rapidly destroyed in stomach hence cannot initiate infection even if live trophozoites from freshly-passed stools are ingested. Trophozoites can survive only up to 5 hours at 37°C & are killed by drying, heat, & chemical sterilization. Precystic Stage Trophozoites undergo encystment in the intestinal lumen. Encystment does not occur in the tissues nor in feces outside the body Before encystment, the trophozoite extrudes its food vacuoles and becomes round or oval. This leads to the precystic stage of the parasite. It contains a large glycogen vacuole and two chromatid bars. It then secretes a highly retractile cyst wall around it and becomes cyst. Cystic Stage Is highly resistant to gastric juice & unfavorable environmental conditions. It begins as an early cyst with a single nucleus, a glycogen mass & 1–4 chromatoid bodies. As the cyst matures, the other structures disappear and the nucleus undergoes 2 successive mitotic divisions to form 4 nuclei. The mature cyst is thus quadrinucleate.  Life Cycle E. histolytica passes its life cycle in a single host-man Mode of transmission is the fecal oral route where man acquires infection by ingestion of food & water contaminated with cysts. Infective form is the mature quadrinucleate cyst passed in feces of convalescents and carriers. The cysts can remain viable under moist conditions for about 10 days. When ingested the cyst passes through the stomach undamaged until the terminal ileum or caecum where excystation occur due to the alkaline environment.  Excystation leads to release of a quadrinucleate amoeba called the metacyst. The metacyst nuclei immediately undergo division to form 8 nuclei each of which gets surrounded by its own cytoplasm to form 8 small amoebulae or metacystic trophozoites. The metacystic trophozoites colonise the submucosal tissue of caecum & colon in the glandular crypts and grow by binary fission. Some metacystic trophozoites develop into precystic forms & cysts which are passed in feces to repeat the cycle.  In most of the cases, E. histolytica remains as a commensal in the large intestine without causing any ill effects. Such persons become carriers or asymptomatic cyst passers and are responsible for maintenance and spread of infection in the community. It may however be activated leading to clinical disease. Such latency and reactivation are the characteristics of amoebiasis. Schematic summary of Life cycle  Pathogenesis & Clinical Features E. histolytica causes two forms of the disease ,intestinal & extra- intestinal amoebiasis. Incubation period is highly variable with an average ranges of 4 days to 4 months. Amoebiasis can present in different forms & degree of severity, depending on the organ affected & the extent of damage caused.  Intestinal Amoebiasis Is characterized by multiple flask shaped ulcers confined to the colon- caecum, sigmoid & rectum. The intervening mucous membrane btn the ulcers remains healthy although ulcers may coalesce to form large necrotic lesions covered with brownish slough. This happens only in about 10% of cases of infection with the remaining 90% being asymptomatic. Ulcers are caused by penetration of the mucosa by trophozoites facilitated by their motility & the tissue lytic enzyme histolysin which damages the mucosal epithelium. Other parasite virulence factors include Amoebic lectin, cystine proteinase which inactivates complement factor C3 and ionophore.  Host factors affecting the course of infection are stress, malnutrition, alcoholism, corticosteroid therapy, bacterial flora & immunodeficiency. Glycoproteins in colonic mucus blocks attachment of trophozoites to epithelial cells hence changes in the nature & quality of colonic mucus may influence virulence. Tumor-like masses of granulation tissue called amoeboma form on the intestinal wall from a chronic ulcer.  The amoeba penetrates to submucosal layer & multiplies rapidly, causing lytic necrosis thus forming an abscess which then breaks down to form an ulcer. Occasionally, the ulcers may involve the muscular & serosa layer of the colon causing perforation & peritonitis. Superficial lesions generally heal without scarring, deep ulcers form scars which may lead to strictures, partial obstruction & thickening of the gut wall. Clinical Features of Intestinal Amoebiasis The clinical course is characterized by prolonged latency, relapses intermissions or short breaks btn episodes. Typical manifestation of intestinal amoebiasis is amoebic dysentery although quite often, only diarrhea or vague abdominal symptoms may occur. Compared to bacillary dysentery, amoebic dysentery is usually gradual in onset with abdominal tenderness which is less & localized.  The patient is usually afebrile & nontoxic however in fulminant colitis where there is confluent ulceration & necrosis of colon the patient is febrile and toxic. Chronic involvement of the caecum causes a condition simulating appendicitis. Charcot-Leyden crystals are often present & E.histolytica trophozoites can be seen containing ingested erythrocytes.  Extra intestinal Amoebiasis Hepatic Amoebiasis Involvement of the liver is the most common extra intestinal complication of amoebiasis. Usually there is no hx of amoebic dysentery in 50% of cases & about 2–10% of the infected suffer from hepatic complications. Amoebic hepatitis from probable repeated invasion by amoebae from an active colonic infection/toxic substances occur.  Liver damage is due to the inflammatory response to trophozoites (lysosomal enzymes and cytokines). Liver abscesses usually in the upper right lobe may occur in 5–10% of persons with intestinal amoebiasis. It consists of central necrotic tissue & normal periphery liver tissue with invading amoeba. They may be multiple or solitary with jaundice only occurring in multiple lesions or when pressing on the biliary tract. Pulmonary Amoebiasis Most often follows extension of hepatic abscess through the diaphragm. Rarely primary amoebiasis of the lung may occur by direct hematogenous spread from the colon bypassing the liver. The lower part of the right lung is usually affected. Hepato-bronchial fistula usually results with expectoration of chocolate brown sputum. The patient presents with severe pleuritic chest pain, dyspnea & non- productive cough.  Metastatic Amoebiasis Involvement of distant organs occur by hematogenous spread & via lymphatics. Hence abscesses in the kidney, brain, spleen & adrenals have been noticed. Spread to brain leads to severe destruction of brain tissue and is fatal. Other areas affected are the skin (Cutaneous Amoebiasis) & Genitourinary Amoebiasis( where the prepuce& glans are affected). Penile amoebiasis is acquired through anal intercourse The destructive ulcerative lesions resemble carcinoma.  Laboratory Diagnosis Microscopy Definitive diagnosis depends on microscopic demonstration of actively motile trophozoites in freshly-passed stool. Presence of ingested RBCs identifies E. histolytica. Iodine-stained preparation is needed to demonstrate cysts or dead trophozoites. Macroscopic features include brownish black foul-smelling stool intermingled with blood & mucus.  A trophozoite of Entamoeba histolytica showing A cyst of Entamoeba histolytica ingested red blood cells Stool Culture Stool culture is a sensitive method in diagnosing chronic & asymptomatic intestinal amoebiasis. Sero-diagnosis Serological tests become positive only in invasive amoebiasis. Tests done include IHA,Latex agglutination test & ELISA. lHA & LA are highly sensitive but often give false-positive results as they remain positive for several years even after successful treatment. Diagnosis of Extra-intestinal Amoebiasis Can be done by microscopic examination of the liver biopsy & also pus aspirate from the abscess may demonstrate trophozoite. Radiological examination is useful e.g the diagnosis of amoebic liver abscess is based on the detection (generally by USG or CT) of space occupying lesions in the liver & a positive serologic test for antibodies against E. histolytica antigens.  Treatment Three classes of drugs are used in the treatment of amoebiasis. 1. Luminal amoebicides: These include Iodoquinol, paromomycin, & tetracycline which act in the intestinal lumen but not in tissues. Note: Metronidazole & tinidazole act on both sites but non of them reach high levels in the gut lumen hence patients with amoebic colitis or amoebic liver abscess should also receive a luminal agent. 2. Tissue amoebicides: Are effective in systemic infections but less effective in the intestine. Examples include emetine, chloroquine, etc. 3. Luminal & tissue amoebicides: Metronidazole and related compounds like tinidazole and ornidazole act on both sites and are the drug of choice for treating amoebic colitis and amoebic liver abscess.  Prevention Preventive measures are like those of other fecal-oral infections. These are : 1. Improved sanitation to prevent water/food contamination from human excreta. 2. Health education & improved personal habits helps in control. 3. Detection & treatment of carriers and their exclusion from food handling occupations will help in limiting the spread of infection. PATHOGENIC FREE- LIVING AMOEBAE Dr J Mudenda  INTRODUCTION Numerous free-living amoebae are found in water & soil. However only a few are potentially pathogenic and can cause human Infections. These are termed as amphizoic organisms -can multiply both in the body of a host (endozoic) and in free-living (exozoic) conditions.  The pathogenic ones are Naegleria Fowleri & Acanthamoeba causing: 1. Primary amoebic meningoencephalitis (PAM) – caused by amoebofl agellate Naegleria (the brain eating amoeba). 2. Granulomatous amoebic encephalitis (GAE) and chronic amoebic keratitis (CAK) – caused by Acanthamoeba Balamuthia have also been reported to cause GAE. PAM & CAK occur in healthy individuals while GAE has been associated with immunodeficient patients.  Naegleria Fowleri Fowleri is the only specie of the genus Naegleria which infects man. It causes the disease called primary amoebic meningoencephalitis (PAM), a brain infection that leads to destruction of brain tissue. It has world wide distribution. Commonly found in warm freshwater (e.g. lakes, rivers, and springs) & soil. N. fowleri is a heat-loving (thermophilic) amoeba that thrives in warm water at low oxygen tension. Only 32 infections were reported in the US in the last 10 years from 2002 to 2011 with no case reported in Zambia. Morphology The parasite occurs in 3 forms: 1. Cyst 2. Amoeboid trophozoite form 3. Flagellate trophozoite form Trophozoite Stage The trophozoites occur in 2 forms, the amoeboid and flagellate.  Amoeboid trophozoite form The amoeboid form has rounded pseudopodia, a spherical nucleus & pulsating vacuoles(used for engulfing RBCs /WBCs). It is the feeding, growing & replicating form of the parasite, seen on the surface of vegetation, mud and water. It is also the invasive stage & the infective form of the parasite.  Flagellate form The biflagellate form occurs within a minute when trophozoites are transferred to distilled water. The flagellate can revert to the amoeboid form, hence N. fowleri is classified as amoeboflagellate.  Cyst Stage It’s the resting or the dormant form & can resist unfavorable conditions such as drying and chlorine up to 50 ppm(2ppm kills the cyst). Trophozoites encyst due to unfavorable conditions such as food deprivation, desiccation, cold temperature etc. Cysts and flagellate forms of N. fowleri have never been found in tissues of cerebrospinal fluid (CSF).  Life Cycle Infection occurs during swimming or diving in warm river freshwater/ponds. Infn can also occur in poorly maintained swimming pools or during nasal irrigation using contaminated tap water. The amoeboid form is the infective stage to man & multiplies by binary fission. Under unfavorable conditions, it forms a cyst which undergoes excystation when conditions are favorable.  Flagellate form of trophozoite helps in the spread of N. fowleri to new water bodies. Completion of the life cycle occur in the external environment.  University of Zambia School of Medicine The Parasitic Flagellate Giardia lamblia  The Parasitic Flagellates Intestinal and Urogenital system: – Giardia and Trichomonas Blood and Tissues: – Trypanosoma and Leishmania  Flagellates Phylum: Sarcomastigophora Subphylum: Mastigophora Class: Zoomastigophora (mastix:whip) Suborder: Diplomonadina Genus: Giardia, Trichomonas, Chilomastix, Enteromonas  Giardia lamblia Giardia lamblia (Syn. Giardia intestinalis, Giardia duodenalis) Disease caused = Giardiasis Named after Prof. A. Giard & Prof. F. Lambyl in 1915 Habitat: upper duodenum, adherent to microvilli  Morphology: trophozoites & cysts Trophozoites: contains 4 pairs of flagella, directed posteriorly that aid the parasite in moving, bilaterally symmetrical, pear shaped (pyriform), rounded anteriorly, tapering posteriorly Dorsal surface convex Ventral surface concave Sucking disc half anterior 9 – 21µm long x 5 – 15 µm broad x 1.5µm thick  Giardia lamblia Trophozoite: a. ventral view; b. profile view Trophozoite: has a convex dorsal surface and a flat ventral surface that contains the ventral disc, rigid cytoskeleton & composed of microtubules and microribbons Cyst: c. immature and mature with four nuclei  Giardia lamblia 1. Trophozoite – lying flat 2. Trophozoite – side view 3. Cyst  Giardia lamblia Scanning electron micrograph of Giardia lamblia, showing sucking disc and flagella; imprints of sucking disks are seen on surface of intestinal mucosa  Giardia species G. agilis, G. muris and G. lamblia N=nucleus MB=median body F=flagellum  Cysts Thick smoothed cyst wall, ovoid in shape or elliptical 8 – 12µm long x 7 – 12µm wide 4 pairs curved bristles, 4 nuclei either clustered at one end or present in pairs at opposite ends Cytoplasm off the wall anteriorly Axostyle runs diagonally through the cyst Flagella shorten and are retracted within cyst – Provide internal support  Giardia lamblia - cysts Giardia lamblia trophozoites and cysts. Giardiasis is probably the commonest, globally distributed, water-borne protozoal infection. It has been estimated, for example, that two million new infections may be acquired in the USA each year from contaminated water. The flagellated trophozoites (left) attach by their suckers to the surface of the duodenal or jejunal mucosa. The ovoid cysts in faeces (right) have a very distinctive structure. They are able to survive standard chlorination procedures, and filtration is required to ensure their exclusion from the drinking water supply. (left Giemsa ; right trichrome )  Giardia lamblia - trophozoites Scanning electron micrograph of G. lamblia in jejunal biopsy The trophozoites are attached to the surface of the jejunal Giardia epithelium by sucker-like organelles, which leave pit marks when they detach. Their ability to produce at least 12 variable surface proteins assists the trophozoites to evade host antibodies. Infection may therefore become chronic.  Giardia lamblia - trophozoites Scanning electron micrograph showing two G. intestinalis trophozoites.  Risk Factors Travel in developing world Changing diapers Eating food without cooking Eating fruits or vegetables without washing Owning a dog Other groups at increased risk for infection include: – children in day care institutions, homosexual men, individuals with immunoglobulin deficiency states (inherited or acquired)  Giardiasis Is a parasitic disease caused by G. lamblia Giardiasis is a major diarrhoeal disease found throughout the world Zoonosis: Giardiasis usually represents a zoonosis with cross-infectivity between animals and humans  Transmission Infective form – mature cyst passed in faeces of man Route of transmission – Faecal-oral Ingestion of contaminated water-most important Ingestion of contaminated food – Person to person-day care, nursing homes, mental asylums (poor hygiene) – Sexual-sexually active homosexual males  Life cycle Giardia has one of the simplest life cycles of all human parasites The life cycle is composed of 2 stages, trophozoite and cyst Acquire infection through ingestion of mature cysts Excystation occurs in stomach & duodenum within 30 minutes Two trophozoites hatch from one cyst  Life cycle Trophozoites multiply by binary fission & colonize in duodenum & upper jejunum Trophozoites adhere to enterocytes by ventral suckers Encystation occurs in transit down the colon Axonemes retract, cytoplasm condenses & thin tough hyaline wall is secreted  Life cycle Encysted trophozoites undergo nuclear division – mature quadrinucleate cyst Cysts passed in faeces into the environment No intermediate hosts are required  Life cycle of Giardia lamblia. Multiplication by binary fission by trophic stage Transmission: 5fs – direct and indirect  Giardiasis Incubation period: Averages 1 – 2 weeks Average duration of symptoms ranges from 3-10 weeks The infective dose: In humans about 10-25 cysts & are capable of causing clinical disease in 8 of 25 subjects Ingestion of more than 25 cysts results in 100% infection rate  Pathogenesis 1. Trophozoites do not invade tissue, feed on mucosal secretions 2. Trophozoites released, use their flagella to ‘swim’ to the microvilli covered surface of duodenum and jejunum where they attach to the enterocytes using their adhesive disc 3. Lectins present on the surface of Giardia binds to receptors present on surface of enterocytes causing duodenal irritation and inflammation of villi in duodenum & jejunum and damage epithelial brush boarder  Pathogenesis 4. Attachment process leads to damage of microvilli, which interfere with nutrition absorption by villi causing excess mucus secretion and dehydration 5. Rapid multiplication of trophozoites eventually creates a physical barriers between the enterocytes and intestinal lumen, further interfering with nutrition absorption.  Pathogenesis 6. This process leads to enterocytes damage, villi atrophy, crypt hyperplasia, intestinal hyperpermeability and brush boarder damage that causes a reduction in disaccharide enzyme secretion 7. Lectins and other cytopathic substance secreted by parasite also causes indirect damage to intestinal epithelium  Pathogenesis 8. Giardiasis results in decreased jejunal electrolyte water and glucose absorption, and damage to intestinal epithelium leads to malabsorption of electrolyte and fluids, resulting in osmotic diarrhoea known as giardiasis 9. Occasionally, trophozoites can enter gall bladder, bile duct leading to jaundice Pathogenesis Jejunal epithelium severe infection with Giardia lamblia can result in partial villous atrophy of the duodenum or jejunum, with resulting flattening of the villi Although the organism is commensal in many individuals, it is considered particularly pathogenic in children in the New World and is a common cause of diarrhoea and a malabsorption syndrome characterised by steatorrhoea in travellers  Symptoms Asymptomatic: largest group Acute: self-limiting infection, acute watery diarrhoea, dull epigastric pain, bloating, vomiting, nausea and flatulence – Stool is profuse & watery in earlier disease – Voluminous, foul smelling & greasy (Steatorrhoea) later – Loss of appetite, malaise, nausea, vomiting  Symptoms Chronic: chronic diarrhoea with malabsorption of fat (steatorrhoea) i.e. stool contains large amounts of mucus and fat = tropical sprue or the yellow syndrome & foul smelling) Malabsorption of vitamin A, protein and D-xylose leading to – Chronic illness with weight loss – Failure to thrive in children – Disaccharidase deficiency – Zinc deficiency in school children & growth retardation – Persistent gastrointestinal symptoms Jaundice: due to obstruction of gall bladder  Diagnosis Microscopy of stool, duodenal aspirates Direct faecal smear: ideally 3 specimens from different days should be examined – both saline and iodine Concentration Methods: – ZnSo4 Floatation reveals cysts – Formol ether sedimentation Trophozoites in soft, diarrhoeic stool Cysts in formed stool  Diagnosis Entero test (string test) – gelatin capsule containing a nylon string with a weight swallowed by the patient. Free end of the string is fixed to the mouth. Capsule dissolves & the string is released in the duodenum. After overnight string is removed & bile stained mucus collected Trichrome & iron haematoxylin  Diagnostic notes Although in severe infections the trophozoites or cysts can usually be found in the faeces, they may be very sparse in chronic infections The trophozoites can sometimes be obtained via a duodenal aspirates Culture – Not done routinely – Diamonds medium  Diagnostic notes cont. Serological methods have also been developed - An enzyme-linked immunosorbent assay (ELISA) to detect IgM in serum provides evidence of current infection - A polyclonal antigen-capture ELISA can be used to demonstrate submicroscopic infections in faeces and an IgA-based ELISA will detect specific antibodies in saliva Molecular diagnosis – DNA probes & PCR for research purposes  Treatment 1. Nitroimidazole derivatives - Metronidazole (Flagyl) – contraindicated in pregnancy??? - Tinidazole 2. Acridine dye - Atabrine (quinacrine) 3. Nitrofurans - Furazolidone  Epidemiology of Giardiasis 1. World wide: Leningrad’s curse, traveller’s diarrhoea 2. Groups, families, person-person - 100% in day care centers, asylums, holiday resorts, homosexuals, mountain streams 3. Warmer climate 4. Mostly waterborne, cross-confluence of municipal water supplies and mountain streams  Epidemiology of Giardiasis About 280 million people worldwide with symptomatic giardiasis Global rates of giardiasis, 1 – 7 % (developed world) & 30% or more (in developing world) 10% of those infected have no symptoms Person-to-person spread is common, – with 25% of family members with infected children themselves becoming infected  Prevention and control 1. Personal hygiene among over crowded population, families or groups, use of iodine - Wash hands thoroughly with soap and water i.e. after using the toilet, before handling or eating food 2. Sanitary disposal of human excreta 3. Proper composting of night soil  Prevention and control 4. Avoid food & water that might be contaminated 5. Boil drinking water or add Iodine tablets & not Chlorine  Prognosis Generally excellent Most patients are asymptomatic Most infections are self-limited Giardiasis is not associated with mortality except in rare cases of extreme dehydration, primarily in infants or malnourished children Thank You University of Zambia School of Medicine TRICHOMONADS  Classification Phylum: Metamonada Class: Parabasalia Order: Trichomonadida Family: Trichomonadidae Genus: Trichomonas  TRICHOMONADS Order TRICHOMONADIDA a. Typically with four to six flagella (one flagellum in one genus and none in another) b. In typical genera, one flagella recurved. free or with proximal or entire length adherent to body surface. c. Undulating membrane, if present associated with adherent segment with curved flagellum Trichomonas hominis Syn: Pentatrichomonas hominis Habitat: Caecum, feeds on enteric bacteria Second commonest intestinal flagellate next to Giardia. feeds on enteric bacteria Morphology: only the trophic stage 1. Pyriform, semi rigid axostyle, cytosomal cleft, 5-14 microns 2. 4 anterior + 1 posterior flagella, posterior flagella free, undulating membrane P. hominis trophozoites in trichrome-stained fecal smears. One can see the spherical nucleus situated near the anterior end in Figures 3 and 4 as well as the prominent axostyle that protrudes a short distance beyond the posterior end. The 3-5 anteriorly directed flagella are not usually seen with this stain. It is not always possible to see the single, posteriorly directed flagellum that usually extends beyond the pOsterior end of the body. A longitudinal series of prominent granules (hydrogenosomes) are frequently visible adjacent to the axostyle and the undulating membrane. The presence of these granules is often helpful in identifying the parasite. Iri Figure 5, the trophozoite is rounded and ameba-like in appearance. However, careful study of the organism reveals the presence of the axostyle and the hydrogenosomes. Trichomonas Trichomonas tenax hominis Trichomonas vaginalis  Life cycle: · longitudinal binary fission · Oral-fecal route, trophic stage transmitted via diet of gruel and milk by filth flies Pathogenesis: none Diagnosis: fecal smear Treatment: not indicated Epidemiology: 1. low incidence, 1 – 12%, warm climates, 2. Under 10 olds, diet of fresh vegetables and fruit Trichomonas vaginalis = causes sexually transmitted infection known as trichomoniasis Habitat: vagina, urethra, Prostate gland, preputial glands Feeds on mucosal bacterial  Trichomonas vaginalis It lives in the reproductive and urinary system Obligate parasite-cannot live without close association with vagina, urethral or prostatic tissues Infects squamous epithelium but not columnar epithelium High incidence of symptomatic infection is seen in women Zinc & other inhibitory substances probably inhibit their growth in men  Trichomonas vaginalis Natural flora (bacteria) keep the pH of the vagina at 4-4.5 and ordinarily this discourages infection T. vaginalis can survive at a low pH Once established it causes a shift toward alkalinity (pH 5-6) which further encourages its growth  Trichomonas vaginalis Facultative anaerobic parasite It produces energy by fermentation of sugars in a structure called hydrogenosome A modified mitochondria in which enzyme of oxidative phosphorylation is replaced by enzyme of anaerobic fermentation  Trichomonas vaginalis infection Significance Sexually transmitted disease of worldwide importance Cosmopolitan in distribution, however prevalence is not uniform because of sanitary and hygiene habits 7.4 million cases reported every year 180 million people infected worldwide 50% asymptomatic carriers, 20-40% in women & 15% in men Morphology: only trophozoites 1. Pyriform flagellate 2. 4 anterior flagella + 1 on body margin undulating membrane 3. posterior flagella does not extend beyond posterior of body 4. thick curved axostyle 5. cytostome small and inconspicuous costa ( chromatin basal body) 6. Chromatin granules present in cytoplasm Giemsa-stained trophozoitesof1 T. vaginalis from culture demonstrate the characteristic morphology of trichomonads. In these specimens one can see the large anteriorly situated nucleus, the prominent, stiff axostyle that extends beyond the posterior end of the body, and the four anteriorly directed flagella. Also the the single posteriorly directed flagellum that courses along the margin of an undulating membrane ending slightly posterior to the middle of the body. T  Risk factors Multiple sexual partners. A history of other sexually transmitted infections (STIs) A previous episode of trichomoniasis. Sex without a condom.  Life cycle The life cycle consist only of a trophozoite stage Transmitted by direct contact during sexual intercourse Reproduces by longitudinal binary fission  Life cycle It begins by division of the nucleus, followed by the division of the neuromotor apparatus and finally, separation of cytoplasm into two daughter trophozoites On sexual contact, trophozoites are transmitted to male and localise in erethra and prostrate gland Multiplies when vaginal condition become more basic than usual (normal pH 3.8-4.2) None venereal transmission is rare  Life cycle: The cycle of Trichomonas vaginalis, a cause of vaginitis in women. This is an example of the simplest type of cycle in which asexually propagating forms are transferred directly from host to host, in this case by sexual intercourse. No special forms for transmission exist. Trichomonas vaginalis on epithelial cells : When the flagellates make contact with vaginal epithelial, they within a few minutes transform to a cytoadherent amoeboid form with thin lamellipodia that make multiple contact points with the cells. The axostyle disappears, but the flagella and undulating membrane remain on free surface. The readiness with which this transformation occurs in different strains is apparently related to their virulence. Trichomonas vaginalis Transmission: STI, no cystic stage Promiscuity, poor personal hygiene = 100% prevalence Congenital (mother to child during delivery) Toilet seats, communal bathing have been implicated in transmission Trophozoite divides by binary fission Incubation period is roughly 10 days  Pathogenesis of T. vaginalis It is not an invasive parasite It remains adherent to the squamous epithelium but not columnar epithelium using adhesins Virulence factors Protein liquids & proteases – help in adherence Lactic acid & acetic acid which lowers the vaginal pH Enzyme cystein proteases - responsible for haemolytic activity of parasites  Symptoms (women) Asymptomatic in most cases Vulvovaginitis – Purulent vaginal discharge (leukorrhoea) concurrrent with Candida albicans – Malodourous smell – Punctate haemorrhages on the cervical mucosa or strawberry cervix – Vulva & vaginal epithelium fiery red & inflamed – Dyspareunia constant Cervical erosion due to Trich. predisposes to uterine cervical carcinoma  Symptoms (women) Urethritis – Dysuria – Increased frequency of micturition  Symptoms (men) Usually asymptomatic Urethritis, epididymitis, prostatitis and superficial penile ulcerations Irritation inside the penis, mild discharge, discharge may be purulent to mucoid or slight burning after urination or ejaculation Mostly self limiting trichomoniasis due to action of the prostatic fluid or flushing out of the flagellate during micturation  Complications (women) PID Premature birth Low birth weight Increased risk of transmission of HIV Increased chance of cervical cancer  Complications (men) Prostatitis Epididymitis Urethral stricture infertility  Diagnosis: 1.Finding Trich. in exudates, saline smear, swim with undulating membrane 2. Pap smear 3. Fecal samples 4. In uretheritis Trich. seen in urine 5. No discharge in males – massage needed 6. Antigen detection 7. PCR 8. Culture  Treatment Single dose of Metronidazole 2 gm once or metronidazole PO 500 mg TDS for 7 days Metronidazole is contraindicated in pregnancy due to its mutagenecity, so topical therapy with clotrimazole is applied Simultaneous treatment of both partners is recommended Tinidazole is an alternate drug Prognosis a full recovery (100%) Epidemiology: 1. Cosmopolitan, 16 – 35 yr olds 2. Highest in population at risk for other STDs. E.g 75%women with STIs have Trich. 30% of pregnant women attending antenatal clinics 3. Infected males infect 100% their female partners 4. males are symptomless carriers 5. An estimated 200 million women suffer from trichomoniasis every year worldwide Prevalence of STDs among antenatal clinic attenders in developing countries. Neisseria Chlamydia Treponema Trichomonas Gonorrhoeae trachomatis pallidum vaginalis Country (%) (%) (%) (%) _______________________________________________________________ Gambia 6.7 6.9 1 32 Kenya 6.6 10.0 - - Swaziland 3.9 - 14 23 Zambia 11.2. - 12.5 38 Nigeria 3.4 - 0.5 21 Ghana 3.4 7.7 - - ________________________________________________________________ Prevention: Good personal hygiene Barrier precautions as in other STDs (use of condoms) Avoidance of sexual contact with infected partners or avoidance of multiple sex partners Detection & treatment of cases either males/females NO VACCINE IS AVAILABLE Trichomonas tenax Habitat: Mouth, Gingivals, margins of gums Tartar around teeth, cavities of carious teeth, tonsilar crypts Transmission: close personal contact, kissing, sharing utensils Treatment: oral hygiene Trichomonas tenax. Comparative morphology of the tricho- monad flagellates of man. Am. J. Trop. Med., 23:125-127.) Hemoflagellates Dr J Mudenda  Introduction Hemoflagellates are parasites that move using a flagella and reside in blood and tissue. Clinically significant members belong to the genera Leishmania and Trypanosoma. There are four morphologic forms associated with these hemoflagellates: amastigote, promastigote, epimastigote and trypomastigote Names are related to the position of the flagella in relation to the position of the nucleus and its point of emergence from the cells. All the organisms in the two genera involve some combination of these morphologic forms.  The major difference between the two genera is the primary diagnostic form found in each. For Leishmania it is the amastigote and for Trypanosoma it is the trypomastigote. The exception is Trypanosoma cruzi in which amastigotes may also be found. Transmission of all hemoflagellates is via the bite of an arthropod vector.  General Characteristics They live in the blood and tissues of man and other vertebrate hosts and in the gut of the insect vectors. Members of this family have a single nucleus, a kinetoplast, and a single flagellum. Nucleus is round or oval and is situated in the central part of the body. Kinetoplast consists of a deeply staining parabasal body and adjacent dot- like blepharoplast. The portion of flagellum which is inside the body of the parasite and extends from the blepharoplast to surface of the body is an axoneme. A free flagellum at the anterior end traverses on the surface of the parasite as a narrow undulating membrane.  All members of the family have similar life cycles. They all require an insect vector as an intermediate host. Multiplication in both the vertebrate and invertebrate host is by binary fission. There is NO sexual cycle is known. Basic morphology of hemoflagellates Parabasal body and blepharoplast together constitute the kinetoplast Morphological stages from amastigote to trypomastigote N=Nucleus ; P=Parabasal body ; B=Blepharoplast ; A=Axoneme ; U=Undulating membrane ; F= Flagellum Trypanosomes  General Characters Members of this genus exist at sometime in their life cycle as trypomastigote stage. However some trypanosomes such as T. cruzi assume amastigote forms in vertebrate hosts. They pass their life cycle in 2 hosts— vertebrate hosts (definitive hosts) and insect vectors (intermediate hosts). In the vector the parasite undergoes development and multiplication afterwhich it becomes infective. Two modes of development in the vector occur and are accordingly classified into 2 groups—Salivaria and Stercoraria.  In salivaria, the trypanosomes migrate to mouth parts of the vectors, so that infection is transmitted by their bite. Examples are T. gambiense and T. rhodesiense causing African trypanosomiasis, which are transmitted by the bite of tsetse fl ies. In stercoraria, the trypanosomes migrate to the hindgut and are passed in feces e.g. T. cruzi causing Chagas’ disease acquired by rubbing the feces of the vector bug into the wound caused by its bit.  Human trypanosomiasis epidemiology Is restricted to two geographical regions- Africa and South America. This is due to the vector being confined to these places alone. 1. African trypanosomiasis (sleeping sickness) 2. South American trypanosomiasis (Chagas’ disease)  Human African Trypanosomiasis(HAT) Trypanosoma brucei complex  Epidemiology of HAT Control efforts have reduced the number of reported annual cases. Less than 10,000 cases reported in 2009 after 50 years of control efforts. Fewer than 2000 cases were reported to WHO in 2017–2018. In 2020, fewer than 700 combined cases were reported to WHO with 85% caused by T. b. gambiense and around 15% caused by T. b. rhodesiense.  Trypanosoma brucei gambiense Also referred to as West African sleeping sickness or Gambian trypanosomiasis. Found in 24 countries in tropical areas of west & central Africa in shaded areas along stream banks where the tsetse fly vector breeds. Accounts for 97% of reported cases of sleeping sickness. The course of the illness is chronic & less aggressive than Trypanosoma Brucei Rhodesiense. It is transmitted by two species of tsetse flies -Glossina palpalis and Glossina tachinoides.  Habitat/Morphology Trypanosomes live in man and other vertebrate host. They are essentially a parasite of connective tissue where they multiply rapidly. They then invade regional lymph nodes, blood and finally may involve central nervous system. In humans/vertebrate host, T. brucei gambiense exists as trypomastigote form with high pleomorphism i.e. can be slender, broad short stumpy and an intermediate form. In insects, it occurs as epimastigote and metacyclic trypomastigote forms.  Life Cycle T. brucei gambiense is digenetic i.e. passes its life cycle in 2 hosts. Definitive(Vertebrate)host include man, game animals, and other domestic animals. Intermediate(Invertebrate) host is an arthropod vector the Tsetse fly of glossina species Both male and female Glossina species (G. palpalis) transmit the disease to humans & dwell on the banks of shaded streams, wooded savanna and agricultural areas. The infective form to humans is the metacyclic trypomastigote.  Mode of transmission are: 1. Through the bite of tsetse fly. 2. Congenital transmission (recorded). Reservoirs include man is the only reservoir host(pigs and others domestic animals known to act as chronic asymptomatic carriers of the parasite). Metacyclic trypomastigotes are inoculated into man when an infected tsetse fly takes a blood meal. These transform into slender blood trypomastigotes that multiply asexually before entering the peripheral blood and lymphatic circulation.  The slender forms become non dividing short stumpy forms and enter the blood stream , CNS invasion occur in chronic infection. Trypomastigotes (short plumpy form) are then ingested by tsetse fly (male or female) during blood meal. In the midgut of the fly, short stumpy trypomastigotes develop into long, slender forms and multiply. In salivary glands they develop into epimastigotes,multiply and eventually transform into the infective metacyclic trypomastigotes. Thereafter, the fly remains infective throughout its life of about 6 months. Life cycle of Trypanosoma brucei  Immune evasion mechanisms-Antigenic Variation As a way of evading the immune system, Trypanosomes undergo periodic antigenic change of surface glycoproteins called variant surface glycoprotein (VSG). As many as 1,000 or more VSG genes are known to help evade immune response. Other mechanisms are resistance to trypanolytic serum proteins(Trypanosome Lytic Factors 1 & 2), immunosuppression, shedding of enormous VSG in circulation leading to formation of immune complexes with antibodies.  Pathogenesis & clinical features T. brucei gambiense causes African trypanosomiasis, a chronic illness that can persist for many years. Infection follows a period of parasitemia after which the parasite gets localized predominantly in the lymph nodes. A painless chancre appears at the site of tsetse fly bite followed by intermittent fever, chills, rash, anemia, weight loss, and headache. Systemic trypanosomiasis without CNS involvement is referred to as stage I disease. In this stage, there is hepatosplenomegaly and lymphadenopathy, particularly in the posterior cervical region (Winterbottom’s sign).  Myocarditis may develop in stage I disease although commonly seen in T. brucei rhodesiense infections. Hematological features seen in stage I include anemia, moderate leukocytosis, and thrombocytopenia. Stage II disease involves CNS invasion occurring several months marking the start of ‘sleeping sickness’. Headache, mental dullness, apathy and day time sleepiness begin at this stage. The patient falls into profound coma followed by death from asthenia  Histopathology show chronic meningoencephalitis with heavy infiltration by lymphocytes, plasma cells, and morula cells(atypical plasma cells) Brain vessels show perivascular cuffing followed by infiltration of the brain and spinal cord, neuronal degeneration and microglial proliferation. Abnormalities in CSF include raised intracranial pressure, pleocytosis, and raised total protein concentrations.  Trypanosoma Brucei Rhodesiense (East African Trypanosomiasis) Trypanosoma brucei rhodesiense is found in 13 countries in eastern and southern Africa. Also referred to as East African sleeping sickness Represents under 3% of reported cases and causes an acute infection. First signs and symptoms are observed a few weeks or months after infection. The disease develops rapidly and invades the central nervous system.  Epidemiology of trypanosomes in Zambia Historical hot spots of rhodesiense HAT epidemics are the Luangwa & the Kafue River Valleys since 1960. According to WHO ,Zambia currently reports