Medical Parasitology & Pathology

1. Medical Parasitology & Pathology By Dr: Yara Shamikh

2. Medical Parasitology Parasitology:is the science that deals with parasites, which infect man temporarily or permanently. Parasitism: indicates that one species (parasite) depends upon another species (host) to derive benefits such as food, shelter and maintenance of species. This association may show harmful effects to the host.

3. The association (relation) between 2 organisms • Parasitism: One organism (parasite) gets benefit and lives on the expense of another organism (host) that usually loses or suffers. • Mutualism: The two organisms get benefit from each other. • Symbiosis: Mutual benefit but the two organisms can’t live independently. • Commensalism: One organism gets benefit while the other (host) is not affected.

4. Description of Parasites • A- Ectoparasite: Live on the outside of the host (infestation). • B- Endoparasite: Live within the body of the host (infection). They are either obligate or facultative parasites • Obligate Parasite: Can’t live independent from the host i.e. permanent residence. ex: Trichomonas • Facultative Parasite: Can live free far from the host or as parasite. ex.: Fasciola They are also classified into: Permanent Parasite, Temporary Parasite, Accidental Parasite, Coprozoic Parasite and also Pseudo parasite, while the Zoonotic parasites are those which are normally found in wild /domestic animals and may harm man.

5. Types of hosts • Final or Definitive Host: Harbors the sexually mature parasite (adult worm or sexual stage of protozoa). • Intermediate Host:Harbors the immature or asexual stage. • Reservoir Host: Animal that harbors the same species of parasites as man and so is a potential source (store) of infection to man with this parasite. • Vector: Usually an arthropod that carries the parasite to its host.

6. Modes of Transmission of Parasitic Diseases Contact- Food & drink- Arthropods- Contact with larvae- Blood borne- Transplacental 1- Contact: • Direct contact with infested persons e.g. scabies, lice. • Indirect contact with infected person’s towels, bed sheets e.g. scabies. • Sexual contact e.g. Trichomonas vaginalis. 2- Food and drink: Is the most common. • Eating or drinking contaminated water or food e.g. helminthes ova, protozoan cysts. • Eating raw or under cooked or under salted fishes e.g. Heterophyes heterophyes. • Eating raw or undercooked meat e.g. Taenia saginata (in cattle meat), T. solium and Trichenella spiralis (in pig or pork meat).

7. 3- By arthropods • Mechanically by non-blood sucking insects e.g. housefly transmit protozoal cysts or helminthes ova. • Biologically by bite of blood sucking insects e.g. malaria, filariasis, trypanosomiasis. • Ingestion of insect containing the infective stage: e.g. infected flea (in Hymenolepis nana) and other insects (in H. diminuta) or infected Cyclops in water (in Dracunculus medinensis). 4- By contact with motile larval stages in the external environment: • Cercaria of schistosoma in water (swimming, washing or irrigation). • Larvae of ancylostoma in soil (penetrate the skin of persons walking bare-footed in muddy soil). 5- Blood transfusion and contaminated syringes e.g. malaria. 6- Transplacentally e.g. Toxoplasma, Trypanosomiasis.

8. Effects of parasitic infection on the host Anemia- Loss of weight- Mechanical effects- Poisoning or allergic reaction- Localized irritation- Facilitating secondary bacterial infection 1- Anemiadue to: Sucking of blood & blood loss e.g. Ancylostoma. • Destruction and feeding on Red cells hemoglobin e.g. malaria. • Depression of bone marrow e.g. Leishmania donovani. • Vit B12 deficiency e.g. Diphyllobothrium latum. 2- Loss of weight due to: Sucking digested food e.g. Taenia and Ascaris. • Preventing fat absorption e.g. Giardia lamblia. 3- Mechanical effects: • Intestinal obstruction in heavy ascariasis and in taeniasis. • Intestinal perforation (ascariasis, taeniasis). • Pressure atrophy in Hydatid (liver and lung). 4- Poisoning or allergic reaction due to toxic substances produced by the parasite in blood. 5- Localized irritation e.g. gastrointestinal disturbances with colic, dyspepsia, diarrhea, dysentery. 6- Facilitating secondary bacterial infection.

9. Methods of control of parasites 1- Control of hosts: • Man • Vector • Intermediate hosts • Reservoir host 2- Personal hygienic measures 3- General hygienic measures

10. Parasitology is classified into three main groups Protozology (proto = primitive) Study of protozoa Helminthology (Helminth = Worm) Study of helminth Entomology Study of arthropods

11. Helminthes = Worms • I. Phylum Platyhelminths(means flat worms) • i. classTrematoda(trematodes or flukes) • i i. class Cestoda(cestodes or tapeworms) • II. Phylum Aschelminths • class Nematoda(nematodes or roundworms) Important Pathogenic Trematodes: Fasciola sp.: includeF. hepatica, F. gigentica Heterophyes heterophyes Schistosoma sp.: includeS. haematobium, S. mansoni, S. Japonicum

12. General Features • All consist of flat, fleshy, leaf-shaped, un segmentedbody exceptSchistosoma sp. which are cylindrical. • They don’t have a respiratory system nor a blood vascular system. • The body is equipped with 2 muscular suckersfor attachment; (oral and a ventral), except the genus Heterophyes, which has a third “genital” sucker. • All are hermaphroditic (i.e. male and female reproductive organs exist in a single body), exceptschistosomes that have 2 separate sexes. • Their life cycles involve a sexual and an asexualreproduction parts. • All require one or more intermediate host(s) for completion of their life cycles.

13. The 1st intermediate host of all flukes is snail, where asexual reproduction occurs. • The adult worm develops in the secondary intermediate host (except the schistosomes which do require only one intermediate host). • The eggsof flukes are equipped with a lid at the top called operculum, through which the larval worm comes out to find its appropriate snail host. • The characteristic eggs are the diagnostic stages of trematodes’ diseases. • The mode of transmission is by ingestion of cyst-contaminated food, except in Schistosoma, where cercaria penetrate the skindirectly.

14. A. Hermaphroditic Trematodesthe most important ones • Fasciola sp. • Heterophyes heterophyes

15. Length: 30 - 75 mm • Common name: Sheep liver fluke {giant liver fluke} • Disease: Fascioliasis “liver rot” • Geographical distribution: Europe, Middle East, Asia. In areas where sheep, cattle {pigs} are raised. • Definitive host: sheep, cattle, pigs and man. • Primary intermediadte host: Snail Lymnoea truncatula forF. hepatica andLymnoea caillaudifor F. gigantica. • Secondry intermediate host: Leaves of fresh-water plants • Mode of infection: Ingestion of raw water-cress containing metacercaria • Infective stage: Metacercaria. • Location of adult: Bile duct • Symptoms: Hepatomegaly, fever, vomiting, diarrhea, eosinophilia, necrotic foci of liver (liver rot) 1. Fasciola sp. F. hepatica, F. gigentica

16. F. hepatica, adult worm measuring 2-5 cm by 8-13 mm, are flat, oval in shape with a cephalic cone containing the oral sucker. It can live in biliary ducts for up to 10 years. F. gigantica adult worm Fasciola hepatica, living adult in bile duct of sheep.

17. Fasciola sp.

18. Laboratory diagnosis • Fasciola egg demonstration of operculated egg in stool; or in duodenal or biliary drainage The eggs are ellipsoidal with small distinct operculum.  The operculum can be opened. Treated with Triclabendazole with Bithionol

19. 2.Heterophyes heterophyes • Length: 1-1.7 mm • Common name: Intestinal fluke • Disease: Heterophiasis • Geographical distribution: Africa, Middle East, Asia • Definitive host: Dog, cat, man • Primary intermediate host: Snail Pirenella conica • Secondry intermediate host: Fresh water fish (Boury, Bolti) • Mode of transmission: Ingestion of raw fish containing encysted metacercaria • Infective stage: Encysted metacercaria. • Location of adult: Small intestine • Symptoms: Abdominal pain, non-bloody diarrhea

20. Heterophyes heterophyes

21. Laboratory diagnosis Operculated egg in stool containing metacercaria Adult fluke of Heterophyes heterophyes. Treated with Praziquantal

22. B. Non-Hermaphroditic Trematodes • These include the Schistosoma sp. also known as {blood flukes}or {digenetic blood trematodes}. • They exist as separate sexes but live attached to each other through a groove in the male, the {gynecophoric canal} or the{schist} • They do not require a secondary intermediate host. • No metacercaria are formed. • All species share a common life cycle.

23. Schistosoma

24. All cause Bilharzia; also known as bilharziasis, schistosomiasis snail fever; or Katayama’s fever in acute schistosomiasis • All transmitted by direct skin penetration ofcercariaeduring swimming

25. Clinical features • The 1st sign is itching and pruritic rash (cercarial dermatitis) at penetration site. • Acute intestinal schistosomiasis (mostly by S. mansoni and S. japonicum) is characterized by fever (Katayama’s fever, that occurs after weeks of initial infection), headache, hepatosplenomegaly and eosinophilia. • Acute urinary schistosomiasis (by S. haematobium) is accompanied by fibrosis of bladder with hematuria. • Manifestations of chronic schistosomiasis include formation of bladder and urinary stones, bleeding oesophagal varices, hepato and splenomegaly, diarrhea (hematuria may progress to cancer).

26. egg embolization in hepatic venules egg in intestinal wall Egyptian with splenomegaly Portal hypertension and ascites due to infection with S. mansoni

27. Microscopic examination of characteristic eggs in stool (for all species), or in urine (for S. haematobium) Laboratory diagnosis • If no eggs appear, demonstration in rectal biopsy (for all species), or in biopsy of bladder (for S. haematobium). • X-rays of urinary tract or intestine. • Serologic tests, and antibody detection by ID injection of cercarial antigens (useful in recent infections) S. haematobium eggs, prominent terminal spine at the posterior end.  S. japonicum eggs, typically oval or subspherical, and has a vestigial spine S. mansoni eggs, prominent lateral spine near the posterior end.

28. Treatment • Praziquantelis the drug of choice for infections by all Schistosoma. • Oxamniquineis effective in treating infections by S. mansoni in some areas in which praziquantel is less effective