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  1. 1. Sahibzada Tasleem Rasool
  2. 2. Symbiosis ------The relationship between two living things (animals). Two living things live together and involve protection or other advantages to one or both partner.  Commensalism  Mutualism  Parasitism*
  3. 3. Host and type of host  Host : An organism that harbors the parasite usually larger than the parasite.  Intermediate host : The host harboring the larvae or asexual stage of parasite.  Final host : The host harboring adult or sexual stage of parasite.  Reservoir host : Animals harboring the same species of parasites as man. Potential sources of human infection.
  4. 4.  Life cycle : The whole process of parasite growing and developing.  The direct life-cycle : Only one host (no intermediate host).  The indirect life cycle : Life cycle with more than one host (intermediate host and final host).
  5. 5. Medical Parasitology is the study of the invertebrate animals and the diseases they cause. Parasites are classified as • Protozoans…….Protozoa (Chapter 21) • Metazoans………include Helminths (Worms) (chapter 22) • Arthopds…… Lice, Mites etc. A parasite: “a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”.
  6. 6. Parasite and the type of parasites  Parasite: It is an animal that is dependent on another animal (host) for its survival.  Type of parasites Protozoa --------------Endoparasite Parasites Helminth --------Ectoparasite Arthropods
  7. 7. A group of eukaryotic microorganisms traditionally classified in the animal kingdom. Protozoa are almost as widely distributed as bacteria. Free-living types occur in soil, wet sand, and in fresh, brackish, and salt waters. Protozoa of the soil and sand live in films of moisture on the particles.
  8. 8. Intestinal and urogenital Blood and Tissue AMOEBAE FLAGELLATES Entamoeba histolytica Giardia lamblia Trichomonas vaginalis PLASMODIUM TOXOPLASMA GONDII LEISHMANIA TRYPANOSOMES
  9. 9. Intestinal protozoa are transmitted by the fecal-oral route and tend to exhibit similar life cycles consisting of • Cyst stage • Trophozoite stage. • Cyst stage ….Cysts are characterized by a resistant wall and are excreted with the feces. The cyst wall functions to protect the organism from dehydration in the external environment as the parasite undergoes a relatively dormant. • Trophozoite stage….Trophozoites are the active, motile feeding stage of a intestinal parasites.
  10. 10. Transmitted by the faecal-oral route and cause diarrhoea may invade the colon and cause bloody diarrhoea – amoebic dysentery. Symptoms : Diarrhea, cramps, flatulence, nausea, and anorexia. Numerous stools per day with blood and mucous, but there is no visible blood. Also causes ameobic liver abscess.
  11. 11. Entamoeba histolytica • Amebiasis: Amoebic dysentery…Inverted flask-shaped lesions in large intestine with extension to peritoneum and liver, lungs, brain, and heart. Blood and pus in stools. • Liver abscesses.. Small necrotic foci, unite to form an abscess in the liver. Liver is primarily involved because trophozoites in blood are removed via the portal circulation through this organ. Diseases Form / Transmission Cysts / Fecal-oral transmission water, fresh fruits, and vegetables Treatment Metronidazole followed by iodoquinol
  12. 12. • Supportive treatment: Rehydration, electrolyte compensation and antispasmodics. • Specific treatment: i. Metronidazole (Flagyl): …for 5-10 days ii. Tinidazole (Fasigyn): …..for 2-3 days Both followed by iodoquinol (used also for asymptomatic carriers or cyst passers). Antibiotics:..Tetracyclines and erythromycin.
  13. 13. • It was probably the first symbiotic protozoan ever observed world-wide distribution. • It lives in the upper portion of the small intestine and results in malabsorption. Move by the lashing of flagella. • Mostly cause non-invasive diseases (unlike amoeba), only mechanical irritation and inflammation. • Acquired by drinking contaminated water, ingestion of contaminated vegetables or fruits, or person-to-person spread by the feco-oral routes. • Cyst is resistant to chlorine
  14. 14. • Foul-smelling, watery diarrhea, abdominal cramps. • May lead to severe malabsorption syndrome: a. Weight loss, fatigue. b. Fatty stools (steatorrhoea) due to diminished intestinal absorption of fatty acids giving the stools pale yellow frothy appearance. Clinical Syndromes Cysts and trophozoites in stool. Laboratory Diagnosis • Drug of choice is quinacrine or metronidazole. • Treatment of all infected persons at the same time e.g. family members. Treatment
  15. 15. • No cyst, only as a trophozoite • Found in urethras and vaginas of women and urethras and prostate glands of men. • Acidity of normal vagina (pH 4.0-4.5) usually discourages infection but once established the parasite causes a shift towards alkalinity (pH 5.0-6.0) which encourages further growth. 1. Sexual intercourse 2. Fomites 3. From mother to her infant through mother's infected birth canal.
  16. 16. 1. Mostly asymptomatic, may cause seropurulent, watery vaginal discharge, itching and painful urination. 2. Men serve as reservoir for infections in women. Men occasionally experience urethritis, prostatitis. Laboratory Diagnosis Trophozoite in vaginal or urethral discharge. (typical tumbling movements) Treatment, Prevention, and Control 1. Metronidazole (contraindicated in pregnancy and lactation) 2. Pessaries and acid douches in female treatment. 3. Both sexual partners should be treated. Clinical Symptoms
  17. 17. Blood and Tissue Protozoa : the cause of malaria. There are 4 species that infect man: P. falciparum, P. vivax, P. ovale and P. malariae : transmitted by the ingestion of Infection can lead to ocular problems and is also a transmitted by sand flies, can lead to visceral, cutaneous and mucocutaneous leishmaniasis haemoflagellates which cause – In Africa - sleeping sickness (transmitted by the Tsetse fly) – In South America - Chagas disease (transmitted by the Reduviid bug)
  18. 18. • Sporozoan parasites reproduce sexually and asexually in alternate generations by means of spores Require two hosts: • Mosquito: for sexual reproductive stages (sporogony host).. production of sporozoites. • Humans and other animals: for asexual reproductive stages (schizogony host)…asexual reproduction by multiple fission Infection initiated by female Anopheles mosquito’s bite, which introduces sporozoites via its saliva into circulatory system (??infective stage). Blood and Tissue Protozoa
  19. 19. • Flu-like symptoms with headache, muscle pains, photophobia, anorexia, nausea, and vomiting. Anemia is seen in pateints. • As the infection progresses, increased numbers of rupturing erythrocytes liberate merozoites and toxic cellular debris ...leading to bouts of chills and fever. • Paroxysms happen every 72 hours in P. malariae and 24 hours in other species. Malaria can acquired by: 1. Transmission by mosquitoes 2. Blood transfusions from infected donor. 3. Among narcotic addicts who share needles and syringes. 4. Congenital acquisition, although rare, is also a possible mode of transmission (congenital malaria).
  20. 20. If untreated, chronic infections by P. vivax, P. ovale, P. malariae cause : • Brain, kidney, and liver damage as a result of the malarial pigment, cellular debris. • Capillary plugging of these organs by masses of adherent erythrocytes. - P. falciparum infections likely to be fatal, if untreated: • brain: Capillary plugging leads to coma and death. • Kidney: renal failure and death. • liver: vomiting of bile, severe diarrhea, and dehydration. Laboratory Diagnosis Microscopic examination of thick and thin films of blood (taken between paroxysms) to identify species.
  21. 21. Supportive therapy : a. Bed rest, relief of fever and headache. b. In the cold stage hot water bottles and extra blankets may bevneeded. In the hot stage apply ice-bags. c. Regulation of fluid balance. d. Blood transfusion in severe hemolytic anaemia. Chemotherapy: - Ideal treatment should: *destroy erythrocytic forms to cure the malarial attack. *destroy exoerythrocytic forms to prevent relapses.
  22. 22. - A combination of two drugs is needed: • Chloroquine for clinical cure of primary malarial attack. acts on erythrocytic forms. • * Followed by primaquine acts on exoerythrocytic forms in liver to prevent relapses. Chemoprophylaxis: • For persons visiting an endemic area or for people living an area where malarial outbreak is reported. • Chloroquine is given two weeks before entering the endemic area, during the stay, and two weeks after leaving the endemic area. • Fansidar® (pyrimethamine and sulfadoxine) is given one tablet is given once weekly for resitant strains.
  23. 23. Diagnosis and Treatment of Malaria The diagnosis of malaria is based on multiple symptoms but eventually must be made from detection of the parasite via laboratory tests. Diagnostic kits using a dye-labeled antibody that binds to the parasite are also available and are especially useful in the field and for rapid diagnoses. The most effective new drugs are currently the most effective agents against multi-resistant malaria strains. However, these drugs are very expensive and are not yet widely available
  24. 24. T. gondii is important because virtually all warm-blooded animals, including man, can become infected with it. Domestic, wild, and cats can transmit Toxoplasma infection to humans. Symptoms of toxoplasmosis include • Anorexia • Weight loss • Lethargy • Difficulty breathing (because of pneumonia) • Fever.
  25. 25. In mothers who first acquire Toxoplasma infection during their pregnancy, about one-third to one-half of the infants are also infected, and the disease is most severe, if the mother has been infected during the first trimester of pregnancy. Treatment Pyrimethamine and sulfadiazine are the two drugs used to treat toxoplasmosis. They act together to inhibit Toxoplasma reproduction. Another choice is the antibiotic clindamycin, which has fewer side effects.
  26. 26. Leishmania are parasites transmitted by the bite of the small sand fly. Leishmaniasis is an important disease and the parasite is transmitted by blood-sucking sand flies with approximately two million new cases every year and one tenth of the world's population at risk of infection.
  27. 27. The symptoms of leishmaniasis are skin sores which erupt weeks to months after the person affected is bitten by sand flies.
  28. 28. Leishmania Leishmania is found always as amastigotes in macrophages. Amastigotes Leishmania donovani causes Viceral Leishmaniasis also called Kalazar The disease spreads by Sandfly bite. Amastigotes in macrophages in bone marrow, liver and spleen. Other species of Leishmania can result in Cutaneous Leishmaniasis Treatment .. Stibogluconate sodium Leishmania braziliensis can cause Mucocutaneous Leishmaniasis which may spread by Sandfly bite.
  29. 29. In contrast to the protozoa, helminths (worms and flukes) are multicellular. The word helminth comes from Greek hélmins, a kind of worm. Parasitic worms are categorized into three groups • Tapeworms (Cestodes) • Round worms (Nematodes) • Flukes (Trematodes.)
  30. 30. Although Parasitic worms can cause severe clinical disease, they usually persist as chronic infections and have insidious effects on growth and development that rarely cause attendance at health centres. Parasitic infections affect more than two billion people with lifelong infections, most of which are in underdeveloped and developing countries….especially those where human faeces is used as fertilizer. Helminthic Infections
  31. 31. Cestodes – pig and cattle "tapeworms" Adult tapeworms are elongated and their body is segmented and they are flat. Theses inhabit the intestinal lumen. Larval forms, which are cystic or solid, inhabit extra-intestinal tissues. Taenia Solium Taenia Saginata
  32. 32. Taenia Saginata – Beef Tapeworm. • Infects cattle and humans, and can only reproduce while in the human gut. • Humans acquire the infective larvae from eating undercooked meat. • T. Saginata is normally 3 m to 5 m in length, but can become very large, over 20 m long in some situations. • The life cycle is completed in humans as the definitive host and cattle as the intermediate host. Diagnosis The basic diagnosis is done from a stool sample. Faeces are examined to find parasite eggs. Treatment Praziquantel opens membrane calcium channels causing paralysis of the worm, aiding the body in expelling the parasite through peristalsis.
  33. 33. Round worms (Nematodes) • Nematodes are simple roundworms. In size they range from 0.3 mm to over 8 meters. • Roundworms are bisexual, cylindrical, colorless and unsegmented worms. • Many of the parasitic species cause important diseases of plants, animals, and humans. • They inhabit intestinal and extraintestinal sites. • Roundworm infections are more common in warm, tropical climates than in cooler, temperate areas of the world.
  34. 34. Nematodes commonly parasitic on humans include • Ascarids (Ascaris), ……Ascaris lumbricoides • Filarids, • Hookworms, • Pinworms (Enterobius) • Whipworms (Trichuris trichiura).
  35. 35. Ascaris lumbricoides Giant roundworm of human • Most common helminth worldwide • The disease ascariasis spreads through Ingestion of egg ~ larva which migrate thru lungs (cough) and mature in small intestine. • They can grow in number and size and may obstruct intestine or bile duct.
  36. 36. Ascaris lumbricoides Most diagnoses are made by identifying the appearance of the worm or eggs in feces. Due to the large quantity of eggs laid physicians can diagnose using only one or two fecal smears. The treatment of choice is Mebendazole Ascariasis I. Cough II. Shortness of breath III.Abdominal pain IV.Nausea and diarrhea V. Blood in the stool VI.Weight loss VII.Fatigue VIII.Presence of worm in vomit or stool
  37. 37. Filarids Wuchereria bancrofti Brugia malayi Wuchereria bancrofti and Brugia malayi are filarial nematode worms which spread by a mosquito vector. W. bancrofti is responsible for 90% of lymphatic filariasis. Lymphatic filariasis or Elephantiasis is an infection of the lymphatic system caused by these filarial worms. Elephantiasis, is a condition characterized by swelling of the lower limbs. It is not fatal but 40 million disfigured or incapacitated.
  38. 38. TREATMENT Single doses of diethylcarbamazine (DEC) administered concurrently with albendazole. is 99% effective in removing microfilariae from the blood for a full year after treatment. Elephantiasis
  39. 39. Hookworms Ancylostoma duodenale Necator americanus More than 1200m infections each year of which 100m are symptomatic. Adult worms live in the intestine and excrete eggs in the faeces. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed.
  40. 40. • Often itchy papules are found at the site where the larva penetrated the skin • There may be cough and wheezing as the larva migrates through the lungs • Hookworm anaemia – Tiredness, aches and pains, Pallor, Breathlessness, Oedema • Measure serum Hb and exclude other causes of anaemia. • Microscopic examination of faecal smears to demonstrate significant numbers of hook worm eggs. • Mebendazole (cheap) – 100mg, twice daily for 3 days
  41. 41. (whipworm) The name whipworm refers to the shape of the worm. • A soil transmitted helminth, prevalent in warm and humid conditions. It causes trichuriasis when it infects a human large intestine. • Can cause diarrhoea, rectal prolapse and anaemia in heavily-infected people Diagnosis Trichuriasis can be diagnosed when T. trichiura eggs are detected in stool examination TREATMENT Mebendazole is 90% effective in the first dose
  42. 42. Flukes (Trematodes) Trematodes  Are commonly called flukes.  Are leaf-shaped worms, which are generally flat and fleshy.  Are hermaphroditic except for Schistosoma, which has separate male and female. .  Have complicated life cycles occurring in two or more hosts.  The most important species pathogenic to humans are Schistosoma hematobium and Schistosoma mansoni.  The first intermediate hosts are snails.
  43. 43. According to WHOTechnical Report Series No. 830. Geneva: World Health Organization; 1993 Schistosoma
  44. 44. Schistosomes remain in the definitive host for an average of two to five years, but in some cases for as long as 20–40 years. Schistosoma
  45. 45. The main forms of schistosomosis are differentiated according to the localization of the lesions: Urinary schistosomosis (urinary bilharziosis). Causative agent: S. hematobium. Intestinal schistosomosis (intestinal bilharziosis). Causative agent: mainly S. mansoni Diagnosis. The eggs can be detected in stool specimens or in urine sediment Therapy. The drug of choice for treatment of schistosomosis is praziquantel, which is highly effective against all Schistosoma species and is well tolerated. Oxamniquine is effective against S. mansoni. Schistosoma
  46. 46. Parasitic arthropods are ectoparasites that have a temporary or permanent association with their hosts. Their considerable medical significance is due to their capability to cause nuisance. Some species or stages of arthropods are capable of penetrating to deeper skin layers or into body openings or wounds.
  47. 47. Infestation with Sarcoptes scabiei causes human scabies, a condition characterized by pronounced pruritus, epidermal mite burrows, nodules, and pustules. Transmission is by close contact (sexual partners, family members, school children, healthcare staff) from person to person, whereby female mites translocate to the skin of a new host. Pruritus is particularly bothersome in the evening when body heat is retained under the bedcovers. Itching mainly occurs in the interdigital spaces and on the sides of the fingers, on the wrists and ankles and in the genital region. Scabies
  48. 48. Diagnosis. Case history and clinical manifestations provide important diagnostic hints that require etiological confirmation by identification of the parasites Therapy requires topical application of c-hexachlorocyclohexane (lindane), permethrin or crotamiton in strict accordance with manufacturer’s instructions. A recent development is per-oral therapy with ivermectin. Underclothing and bed linens must be washed at a minimum temperature of 50° C. Control. Scabies
  49. 49. Fungi
  50. 50. Fungi Mycology • Fungi are eukaryotic microorganisms (domain eucarya) that occur ubiquitously in nature. • Only about 200 of the thousands of species have been identified as human pathogens, and among these known pathogenic species fewer than a dozen are responsible for more than 90% of all human fungal infections. • The basic form of a unicellular fungus is the yeast cell. • The cell walls of fungi consist of nearly 90% carbohydrate (chitin, glucans, mannans) and fungal membranes are rich in sterol types not found in other biological membranes (e.g., ergosterol).
  51. 51. Basic Morphological Elements of Fungi
  52. 52. General Aspects of Fungal Disease Besides fungal allergies fungal infections are by far the most frequent fungal diseases. Mycoses are classified clinically as follows: • Primary mycoses histoplasmosis, blastomycoses). • Opportunistic mycoses (surface and deep yeast mycoses, aspergillosis, pneumocystosis). • Subcutaneous mycoses • Cutaneous mycoses (dermatomycoses).
  53. 53. Most Important Mycoses in Humans Remarks Etiology Disease Pulmonary mycosis. Inhalation of spores. Dissemination into RES. America, Asia, Africa Histoplasma capsulatum Histoplasmosis Endogenous infection. Primary infection of mucosa and skin with secondary dissemination Candida albicans, other Candida sp. Candidiasis Aspergilloses of the respiratory tract, endophthalmitis; aspergillosis of CNS; septic aspergillosis Aspergillus fumigatus (90 %); Aspergillosis Infections of various organs in immunosuppressed patients. Sepsis also possible. Torulopsis glabrata; Trichosporon eigelii Yeast mycoses (except candidiasis)
  54. 54. Clinical Groupings for Fungal Infectios  Besides fungal allergies, fungal infections can lead to several diseases.  A. Skin Mycology: 1- Superficial Mycoses: infections of skin or hair. No living tissue is invaded and there is no cellular response from the host, e.g. tinea nigra disease in the hand palm. 2- Cutaneous Mycoses: superficial fungal infections of skin, hair or nails. No living tissue is invaded, however a variety of pathological changes occur in host because of the presence of the infectious agent and its metabolic products, e.g. Dermatophytosis (tinea) of scalp, skin and nails. 3- Subcutaneous Mycoses: e.g. Zygomycosis
  55. 55. Tinea nigra Tinea pedis (athlete's foot) Tinea capitis with extensive hair loss
  56. 56. is a chronic inflammatory disease that is typically restricted to the nasal submucosa and characterized by restricted subcutaneous masses. Symptoms include nasal obstruction, drainage and sinus pain (predominant in males). Zygomycosis caused by Conidiobolus sp.
  57. 57. B- Dimorphic Systemic Mycoses  Dimorphic fungal pathogens which can overcome the physiological and cellular defenses of the normal human host by changing their morphological form.  Primary site of infection is usually pulmonary, following the inhalation of conidia (asexual spores). C. Opportunistic Systemic Mycoses - Candidiasis is an infection caused by a species of the yeast Candida albicans. - Candidiasis can affect the skin, nails, and mucous membranes throughout the body including the mouth (thrush), esophagus, vagina (yeast infection), intestines, and lungs
  58. 58. Thrush mouth in immuno- suppressed patient Cutaneous candidiasis, Interdigital candidiasis Moisture, heat, friction of the skin are the principle predisposing factors in the normal patient, however obesity, diabetes mellitus, warm water immersion and the use of broad-spectrum antibiotics are additional factors.
  59. 59. Differences between Fungi and Bacteria Bacteria Fungi Propertie s Prokaryotic; no membrane; nucleoid; only one “chromosome Eukaryotic; nuclear membrane; more than one chromosome; mitosis Nucleus No mitochondria; no endoplasmic reticulum; 70S ribosomes, Mitochondria; endoplasmic reticulum; 80S ribosomes Cytoplasm No sterols Sterols (ergosterol) Cytoplasmic membrane Murein, teichoic acids (Gram-positive), proteins Glucans, mannans, chitin, chitosan Cell wall Heterotrophic; obligate aerobes and anaerobes, facultative anaerobes Heterotrophic; mostly aerobes; no photosynthesis Metabolism
  60. 60. Therapy A limited number of anti-infective agents are available for specific treatment of fungal infections: Polyenes. These agents bind to membrane sterols and destroy the membrane Structure…… Amphotericin B, Nystatin, natamycin. Azoles. These agents disrupt ergosterol biosynthesis. Their effect is mainly fungistatic…… Ketoconazole… Good activity against Candida and Aspergillus. Antimetabolites. 5-Fluorocytosine… (base analog) Interferes with DNA synthesis Griseofulvin. This is an older antibiotic used in treatment of dermatomycoses. By oral application, therapy must often be continued for months.