Introduction To Parasitology

INTRODUCTION TO PARASITOLOGY

DEFINITION OF TERMS A. Parasitology - dependence of one living organism on another. Clinical Parasitology - Concerned with animal parasites of man Divisions of Parasitology 1. Protozoology 2. Helminthology a. Roundworms (nematodes) b. Flatworms –Cestodes (tapeworm) Trematode (fluke) 3. Medical Entomology

B. Host - Organism upon which parasites live - Types of hosts: 1. Final Host or Definitive Host - Harbors the sexual stage 2. Intermediate Host - Harbors the larval or asexual stage 3. Reservoir Host - Harbors the same species or parasites as man 4. Carriers 5. Vectors - Hosts that transmit parasites to man - An insect that carries the infective stage of an organism to another person.

C. Parasite - An organism living upon or within another organism for nourishment. - Types: 1. Obligate parasite - Organism which cannot exist without a host. 2. Facultative Parasite - Organism which may live either a parasitic or free-living existence 3. Incidental parasite - lives on another host other than its present host - animal parasites which occur in human beings.

4. Spurious parasite - parasitizes other hosts and are recovered in living or dead state from human feces 5. Endo vs. Ectoparasites a. Endoparasites---- produces an infection b. Ectoparasites---- Attached to the skin or temporarily invade the superficial of the host’s body. Produces an D.tissues Host- Parasite Relationships infestation. 1. Parasitism  a relationship between 2 living organisms of different species  one of the members lives at the expense of the other and at the same time causes it harm.

2. Commensalism- parasite benefits without reciprocating but without injury to the host. 3. Mutualism- beneficial to both but life without the other is still possible 4. Symbiosis  close association of 2 organism  both members are so dependent upon each other that life apart is impossible.

SOURCES OF PARASITIC INFECTION A. Contaminated Soil or water - Soil Ascaris lumbricoide, Trichuris trichura Hookworms, Strongyloides - Water Amoeba, Flagellates, Taenia solium Blood Flukes B. Food containing the Immature Infective Stage of the Parasite --Fish, crab, snail  tapeworms, capillaria -- Beef, pork  Trichinella, Taenia -- Intestinal, liver and lung flukes

C. Blood sucking Insect -- Malaria, Leishmaniasis, Trypanosoma D. Domestic or Wild Animal Harboring the Parasite -- Dogs: D. caninum, E. granulosus, T. canis A. Caninum --Cats: Toxocara cati -- Herbivorous animals: Trichostrongylus

E. Another person, his clothing, bedding or immediate environment that he has contaminated. -- E. histolytica, pinworm, tapeworm -- scabies F. One’s self (auto-infection) -- Strongyloides stercoralis -- E. vermicularis (pinworm)

MODE OF TRANSMISSION PORTAL OF ENTRY 1. Mouth- most common portal of invasion - ingestion 2. Skin a. Skin penetration Filaria, cercaria b. Blood sucking arthropods--- mosquitos, flies, mites 3. Inhalation--- Enterobius vermicularis 4. Transplacental– Ascaris lumbricoides --Toxoplasma, Malaria (Plasmodia) 5. Transmammary--- strongyloides, Ancyclostoma, Plasmodia,Schistosomes 6. Sexual Intercourse– Trichomonas vaginalis

B. PORTAL OF EXIT 1. Feces --- mostly all kinds of parasite 2. Urine --- Trichomonas vaginalis Strongyloides stercoralis, Schistosoma haematobium 3. Sputum --- Paragonimus westermani Ascaris lumbricoides 4. Discharges--- Trichomonas vaginalis Dracunculus medinensis

MECHANISM OF PATHOGENESIS A.

General Life Cycle Parasite

Host

Migrate to location for maturation

Reproduce B. Factors that determine intensity of parasitic infection a. Topography of Locality b. Social condition c. Age d. Hygienic Measure e. Sewage Disposal f. Water supply

C. Ways of damage to Host 1. Inapparent infection -- causes no symptoms and produces no harm 2. Traumatic damage a. External --- invades the skin b. Internal --- Direct damage to organs 3. Lytic necrosis -- Elaborate enzymes 4. Stimulate Host-tissue reaction -- Cellular proliferation and infiltration 5. toxic and allergic phenomena --- introduce toxins D. Immunity in Parasitic infections E. Infective vs. Pathogenic stage

CLASSIFICATION OF PARASITES ANIMAL KINGDOM Subkingdom Protozoa -Class Rhizopoda or Sarcodinia (Amoeba) - Class Mastigophora or Flagellata (Flagellates) - Class Ciliata or Infusoria (Ciliates) - Class Sporozoa (Sporozoas)

Subkingdom Metazoa - Phylum Nematoda or Nemathelminthes - Phylum Platyhelminthes (Flatworms) --- Class Trematoda (Flukes) --- Class Cestoda (Tapeworms) -Phylum Arthropoda

PROTOZO A

INTRODUCTION A. Morphology 1. Ectoplasm--- more homogenous and less granular Function: locomotor apparatus for procurement and 1 ingestion of food ( locomotion) 2 Respiration, Discharge of metabolic wastes (excretion), Protection of organism Structures: 3 a. Contractile or Pulsating vacoules– osmoregulators b. Plasma membrane c. Locomotor apparatus: pseudopodia, flagella and cilia d. Cystosome and cytophage e. Excretory vacoules

2. Endoplasm --more granular --Function: food synthesis --Structures: a. Chromatoidal bodies -- glycogen or protein stores -- seen in cystic stage only b. Mitochondria c. Golgi apparatus d. Microsomes e. endoplasmic reticulum -- Nucleus Forms: a. Vesicular nucleus -- small amount of chromatin material in large amount of nucleoplasm -- Karyosome -- ex. Entamoeba coli

b. Compact nucleus --large amount of chromatin material in small amount of nucleoplasm --Ex. Balantidium coli Life Cycle Excystation Trophozoite

Cyst Encystation

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Trophozoite– feeding stage -- absorbs nutrients from the plasma membrane -- Motile stage -- Have organ of locomotion Cyst--- non feeding stage -- rely on stored food (chromatoidal bodies) --- Non motile stage

Factors for excystation: 1. Osmotic changes in the medium 2. Enzymatic action of enclosed organism on inner surface of cyst wall 3. Favorable pH and enzymatic action of host tissues

 Factors

for Encystation: 1. Deficiency or overabundance of food 2. Excess of catabolic products 3. marked change in the pH 4. Desiccation of the medium 5. Depletion or excess supply of oxygen 6. Overpopulation

CLASS RHIZOPODA (SARCODINIA) Mode of locomotion : Pseudopodia (false feet) C. Entamoeba histolytica --- Disease: Amoebiasis --- Reservoir: major: humans minor: dogs, pigs, monkeys

Transmission: Contaminated food or drinks 1. polluted water supply 2. unclean handling of infected individuals 3. Droppings of flies and other insects 4. use of night soil 5. gross carelessness in personal hygiene --- incubation period: 2-5 days

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Infective stage: cyst --- Cigar shaped chromatoidal body

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Pathogenic stage: trophozoite --- central karyosome

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Types of Amoebiasis: 1. Asymptomatic--- carriers or cyst passers 2. Symptomatic a. Intestinal amebiasis - amoebic colitis - amoebic dysentery - amoebic appendicitis b. Extra-intestinal amebiasis - Liver most common - Lung, brain, skin

cyst

trophozoite

Diagnosis: - History and P.E. - Stool exam - Proctosigmoidoscopy -Liver function test, serologic exam, hepatoscan, ultrasound Treatment: - Metronidazole Prevention: - Personal hygiene -Environmental sanitation

Life cycle

Entamoeba coli 

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Stages: 5 developmental stages Trophozoite -- Eccentric karyosome -- Dirty looking sytoplasm Cyst -- 8 nuclei -- whisk broom shaped chromatoidal body Non- pathogenic  commensal tissue dweller Life cycle like E. histolytica

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Infective stage: cyst

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Pathogenic stage: none

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S/sx: none

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Diagnosis: demonstration of organism in stool

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Treatment: None

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Prevention: same as E. histolytica

Cyst

trophozoite

Endolimax nana   

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Smallest protozoa Non-pathogenic Trophozoite --- Eccentric karyosome --- Narrow rim of cytoplasm Cyst ---Ovoidal or round

Entamoeba gingivalis   

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Found in buccal cavity, gums Present in people with poor oral hygiene Only trophozoite stage is present -- Infective stage: trophozoite -- Pathogenic stage: none Manner of transmission: 1. droplet spray 2. Sharing of food and utensils 3. kissing If present indicates need for better oral hygiene Prevention: proper care of teeth and gums

FREE LIVING AMOEBAS (OPPORTUNISTIC AMOEBA) 1.

Naegleria fowleri -- found in freshwater lake or ponds, swimming pools -- life cycle: a. trophozoite– amoeboid form and flagellate form b. Cyst Pathogenesis: Portal of entry: olfactory neuroepithelium -- causes primary amebic meningoencephalitis -- seen in healthy individuals

-- Diagnosis: -- amebas in tissues are present only as trophozoites -- no cysts seen in tissues -- Treatment: Amphotericin B -- Prevention: Avoid contact with stagnant or thermal waters Hyperchlorination not effective

2. Acanthamoeba -- Most common species: Acanthamoeba culbertsoni -- Found in soil or stagnant waters -- Source of infection: dust or water -- Resistant to chlorine and drying -- Life cycle: a. trophozoite ----- no flagellate form b. cyst

-- Pathogenesis: Portal of entry: broken or ulcerated skin/eyes, lungs and GIT Disease: Chronic meningoencephalitis in immunocompromised host, Corneal ulceration -- Treatment: Sulfadiazine -- Prevention: early diagnosis Prompt treatment of lesions

CLASS CILIATA  Balantidium

coli

Mode of locomotion--- cilia Habitat– cecum of large intestine Epidemiology --- Final host: Pig  man and monkeys accidental host Mode of Transmission– fecal contamination

Morphology – Largest protozoa 2 stages: 1. Trophozoite – cytopyge and cytosome -- covered with cilia 2. Cyst – thick cell wall Pathology: Balantidiasis ----Dysentery ---fatal type Asymptomatic Diagnosis: (+) trophozoite or cyst in stool Treatment: Tetracycline, Metronidazole Prevention: same as E. histolytica

CLASS FLAGELLATA (MASTIGOPHORA) 

Mode of Locomotion: Flagella

4.

Giardia lamblia

Morphology: a. Trophozoite– pear shaped, pathogenic stage b. Cyst --- Infective stage Mode of Transmission: contaminated food or water, oralfecal route, anal sex Habitat: Duodenum, jejunum

Binary fission

Incubation period: 7-10 days Disease: Giardiasis, Lamblia intestinalis ,Giardia duodenalis and Giardia intestinalis, Malabsorption Syndrome Signs and Symptoms: steatorrhea, abdominal pain, flatulence, severe diarrhea, foul smelling and bulky stools,fatigue, nausea and vomiting.

Treatment: metronidazole, furazolidone Prevention -- Do not drink from fresh water streams or lakes without boiling or filtering the water. -- Do not use ice or drink beverages made from tap water that may be contaminated. -- Do not eat uncooked or unpeeled fruits or vegetables grown in conditions in which contamination with Giardia might occur. -- Wash hands before eating food, after changing diapers, using the bathroom, or touching pets. -- Avoid oral/anal sex.

Trophozoite emerging from cyst

Trophozoite emerging division

2. Trihomonas tenax (T. buccalis) - non-pathogenic, found in mouth and gums - trophozoite stage only - transmission: droplet spray, kissing, sharing of utensils - treatment: none - prevention: oral hygiene

3. Trichomonas vaginalis - found in vagina and prostate gland - trophozoite stage only: infective and pathogenic stage - transmission: ingestion unhygienic practices in females - alkaline vaginal pH sexual intercourse in males

“- disease: STD - pruritus vulvae - mucopurolent discharge - dysparenuria, dysuria - “strawberry cervix” - diagnosis: discharge and demostration of organism in urine - treatment: Metronidazole - prevention: hygienic practices douching limit to no sex

Trichomonas vaginalis: mature and trophozoite

STRAWBERRY CERVIX

Blood and Tissue flagellates Morphologial stages: - amastigote  promastigote  epimastigote  trypomastigote

Leishmaniasis - species: Leishmania donovani: kala-azar or visceral leishmaniasis Leishmania tropica: oriental sore or cutaneous leishmaniasis Leishmania braziliense: espundia or mucocutaneous leishmaniasis

- stages: amastigote  promastigote (pathogenic stage) (infective stage) -

vector: sandfly (phlebotomus fly) Life cycle: sandfly stageshuman stages

Cutaneous Leishmaniasis

2. Trypanosomiasis A) African sleeping sickness - species: T. brucei rhodiense (acute) T. brucei gambiense (chronic) - stages: epimastigote (infective stage)

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- vector: tse-tse fly (Glossina fly)

trypomastigote (pathogenic stage)

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Trypanosoma brucei

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Tsetse fly

B) American trypanosomiasis (Chagas disease) - species: T. cruzi - stages: amastigote (infective)  promastigote epimastigote  tyrpomastigote(pathogenic) -vector: Reduvid bug or kissing bug

Class

Sporozoa

general life cycle 1. Shizogony - asexual reproduction in human - stages: trophozoite schizont merozoite gametocyte: ♀macrogamete ♂ microgamete

2. Sporogony - sexual reproduction in mosquito - stages: zygote oocyst cyst (sporoblast) sporocyst sporozoites

Subclasses 1. coccidia: Isospora belli, Cyptosporidium, Toxoplasma gondii 2. plasmodia: Plasmodium

Plasmodium species Epidemiology - strain: Plasmodium falciparum Plamodium vivax Plasmodium malariae Plasmodium ovale - vector: Anopheles mosquito -stages: schizogony and sporogony infective stage in man: sporozoite pathogenic stage in man: merozoite infective stage in mosquito: gametocyte

Plasmodium species Plasmodium falciparum Incubation pd: 9-14 days Type of fever: malignant tertian RBC affinity: old and young Schizont: not seen in blood smear Gametocyte: sausage shape---male crescent shape---female Cytoplasm: Maurer’s dots

Plasmodium malariae Incubation pd: 14-30 days Type of fever: quartan RBC affinity: old RBC Schizont: rosette pattern Gametocyte: spherical shape---male spherical shape---female Cytoplasm: Ziemann’s dots

Plasmodium falciparum P. falcifarum trophozoite

P. falcifarum schizont

P. falcifarum gametocyte fig. 27 & 28 (female) fig. 29 & 30 (male)

Plasmodium Malariae Plasmodium Malariae Trophozoite

Plasmodium Malariae schizont

Plasmodium Malariae gametocyte fig no. 23 - Developing gametocyte fig no. 24 – Female gametocyte fig no. 25 - Male gametocyte

Plasmodium Vivax Plasmodium Vivax trophozoites

Plasmodium Vivax schizont

Plasmodium Vivax gametocytes

Plasmodium species Plasmodium vivax Incubation pd: 14-15 days Type of fever: benign tertian RBC affinity: young RBC Schizont: cluster of grapes Gametocyte: spherical shape---male spherical shape---female Cytoplasm: Schuffner’s dots

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Anopheles mosquito

Schizont

P. Vivax

P. Malariae P.Falciparum

12-24 chromatin dots

Rosette pattern 6-12 dots Spherical (male) Larger spherical (female

Spherical (male) Gametocyte Larger spherical (female)

Not seen in smear 18-24 dots Sausage-shaped (males) Cresent-shaped (females)

Cytoplasm

Schuffner’s Ziemann’s dots dots

Maurer’s dots

Multiple infections

rare

common

Very rare

Pneumocystis carinii -

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Previously classified as sporozoa Recently classified as a fungus Transmission: inhalation Disease: Pneumocystis carinii pneumonia Manifestations: most common opportunistic infection of AIDS patients fever, shortness of breath, non-productive cough, death Diagnosis: CXR, silver staining of alveolar secretions Treatment: trimethoprim sulfamethoxazole, IV pentamidine Prophylaxis: primary--------- Co-trimoxazole alternative------- dapsone, clindamycin, pentamidine

Toxoplasma gondii -

Obligate intracellular parasite

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Definitive host: cats

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Transmission: ingestion of uncooked infected meat containing cysts fecal-oral transmission transplacental (TORCHES) organ or blood transplantation accidental inoculation inhalation of cyst----- most common

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Manifestations: fever, lymphadenopathy, splenomegaly, pneumonia encephalitis, chorioretinitis

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Diagnosis: cranial CT scan, retinal examination, bone marrow smear

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Treatment: sulfadiazine plus pyrimethamine

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Prevention: cook meats completely cleaning kitty liter with precaution do not allow cats to scavenge for food wash vegetables thoroughly

Quiz time Please prepare ¼ paper And number it 1-2

1. Etiologic agent of malaria toxoplasma histoplasma plasmodium

2. Pathogenic stage cyst trophozoite