Clinical Pharmacy program
Microbiology Code: MED 311
Level 5
Medically Important parasite
References:
Essential Microbiology by Stuart Hogg. Wiley-Blackwell; 2 editions (2013)
Medical Microbiology: with STUDENT CONSULT Online Access, by Patrick R. Murray PhD, Ken S. Rosenthal PhD, Michael A. Pfaller MD. Publisher: Saunders; 7 editions (2012).
Basic Principles of Medical Microbiology and Immunology. Kayser H. Fritz, Johannes Eckert, Rolf M. Zinkernagel. 2005 Thieme.
Jawetz, Melnick, & Adelberg’s.( 2013). Medical Microbiology (26 Edition).
1. Understand the basic classification of parasites.
2. Classify and give examples of AMOEBAE of medical importance . 3. Classify and give examples of HELMINTHS of medical importance.
4. Classify and give examples of ARTHROPODES of medical importance.
5. Describe general life cycle of each class of parasite.
6. Interpret important stages in each life cycle.
7. Understand the basic laboratory investigations of parasitic infections.
8. List important antiparasitic drugs.
Parasites and Parasitism
Parasitism
In this kind of symbiotic relationship, while one symbiont benefits and is called the parasite, the other one gets harmed and is called the Host.
The parasite is a living organism that live on or within the body of another organism called the Host. The parasite is metabolically dependent on the host and causes harm to this host.
Parasites are Eukaryotic organism in which the nucleus is quite
organized and is contained within a nuclear membrane.
What are the types of parasites?
ENDOPARASITES
• I. Protozoa
Protozoa are microscopic, one-celled
parasitic organisms that are infectious
to humans.
Protozoa
Entamoeba histolytica trophozoite
II. Helminths (metazoa)
Helminths are large, multicellular organisms.
• There are two main groups of helminths that are human parasites:
1. Platyhelminths: Trematodes and cystodes
2. Nemathelminthes : Nematodes
Trematodes (flat worm)
Schistosoma adult worm
Cestodes (flat segmented)
Taenia adult worm
Nematodes (Round worms)
Ascaris adult worm
hg
Nematodes (Round worms)
Eg Human hookworm
ECTOPARASITES
• Blood-sucking arthropods such as mosquitoes (because they are dependent on a blood meal from a human host for their survival
• Arthropodes that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to
months) such as ticks, fleas, lice, and mites
• Arthropods can cause diseases in their own, but also act as vectors, or transmitters, of many different pathogens that in turn cause tremendous morbidity and mortality from the
diseases they cause.
ECTOPARASITES
Mosquitoes
ECTOPARASITES
Life cycle of parasites
• During their life, parasites typically go through several developmental stages that involve changes not only in structure but also in biochemical and antigenic
composition.
• studying the life cycle of a parasite means to follow the pathway of its development starting by one stage and
ending at it.
Life cycle of parasites
• The development of a parasite usually requires a host or more
• The host that harbors the adult or sexually mature stage where sexual reproduction occurs is called the Definitive host.
• While the host that harbors the larval or sexually immature stage
is called the Intermediate host.
Life cycle of parasites
(cont.)• Human usually get infected by exposure to the infective stage : stage responsible for human infection
• The diagnostic stage is the stage that can be identified in different laboratory samples.
• Each parasite has a special organ, tissue or cell where it finally resides inside human host that is called the Habitat.
• Stages of development of the parasite, and its life cycle, as well as the
choice of a host or hosts required for survival and reproduction, are
important points of identification and diagnosis
Studying the life cycle of parasites is important to:
1. Recognize the characteristic clinical picture.
2. Trace the diagnostic stage.
3. Identify the weakest link for prevention and
control of parasitic infection
Clinical picture
• D ur in g th e jo ur ne y of th e pa ra si te in si de th e hu m an h os t an d af te r its ar ri va l to its ha bi ta t, it c au se s da m ag e or ha rm & f ac e a ho st r ea ct io n. • T he m ix tu re o f tis su e in ju ry an d re ac tio ns r es ul ts in a w id e ra ng e of c lin ic al p ic tu re fo r ea ch p ar as it e.
Parasites are classified according to their habitat into:
1.Intestinal parasites
2.Liver & biliary tract parasites 3.Respiratory system parasites 4.Blood parasites
5.Lymphatic system parasites
6.Central nervous system parasites
7.Genito-urinary Parasites
Habitat related clinical picture
• Small intestinal parasites:Ex. Giardia dudenalis
Symptoms: abdominal pain, colic (increase intestinal motility) Diarrhea is loose, watery stools with increase number of motions more than three times in one day.
In severe cases there is steatorrhea (fatty stool)
• Large intestinal parasites:Ex. Entamoeba histolytica
Symptoms: abdominal pain, colic (increase intestinal motility), Dysentery(with blood and mucous in stool.
Tenesmus(cramping rectal pain with straining).
Habitat related clinical picture
• Liver and biliary tract:
Symptoms: abdominal pain, right upper quadrant pain There may be change in the color of urine or stool.
• Blood parasites: Ex. Malaria
Symptoms: anemia with easily fatigability loss of
concentration and dyspnea.
Habitat related clinical picture
• Respiratory system parasites: Larva of soil transmitted helminths Symptoms: cough and expectoration of sputum that may be blood
tinged.
Wheezes occur if allergy developed to the circulating parasite antigen.
Dyspnea Shortness of breath may occur in severe case.
Habitat related clinical picture
• Urinary system parasites:Ex. Schistosoma haematobium Symptoms: dysuria= painful micturition.
Frequency= means having an urge to pass urine more often than usual (increase number of motion) due to urinary tract irritation.
Change color of urine due to presence of pus or blood.
Change volume of urine: oliguria., polyurea or anuria
Life Cycle of Parasites
From the previously described life cycles we can classify life cycles into:
Direct life cycle:
When a parasite requires only single host to complete its development, it is called as direct life cycle, e.g. Entamoeba histolytica requires only a human host to complete its life cycle.
Indirect life cycle:
When a parasite requires 2 or more species of host to complete its development, the life cycle is
called as indirect life cycle, e.g. malarial parasite requires both human host and mosquito to complete
its life cycle
.Modes of transmission of parasites
Modes of transmission of parasites
Through mouth/ food: The infective stage of the parasites may be
present in food or it may gain access to food from contaminated
water, soil etc. and enter the host via mouth. Vegetables are
contaminated with soil and water containing the cysts, ova, larvae
of parasites. The infective larval stages are present in meat, fishes,
molluscas. Food may also be contaminated by insects which act as
mechanical carriers and by infected food handlers.
Modes of transmission of parasites
Through skin penetration: The infective phase penetrates the hosts skin by it’s own effects, e.g. infective larvae of hook worms, or infective phases may be introduced into hosts body by arthropod vectors, e.g. malarial parasite Plasmodium malariae through female mosquitoes Anopheles.
Direct contacts: This implies the immediate transmission of infective materials from one host to another. The eggs of some helminths, the ectoparasitic arthropods such as lice, mites.
Transplacental/ Intra-uterine transmission or pre-natal infection: In
this case the infective phase enters the fetus through fetal circulation, e.g.
Modes of transmission of parasites
Vector : A vector is a living organism usually an arthropod that transmits the parasite from one host to another. Vectors may be:
• Biological vector : The arthropod in this case is essential for parasite development and part of the life cycle occurs inside it. Eg:
Mosquitoe carrying Plasmodium malaria
• Mechanical vector : The arthropod in this case has no role in the
development of the parasite, it just carries the infective stage on its
body. Eg :House fly carrying cyst of Entamoeba hystolytica
Taxonomic rank
• Taxonomic rank is the relative level of a group of organisms.
• Examples of taxonomic ranks are species, genus, family, order, class, phylum and kingdom
• Binomial naming system consists of giving two names to an organism. Just like we have a name and a surname, the organisms are named after their genus and species. These are the lowest two levels in the taxonomic system of naming. The first name is the genus
followed by the name of their species.
• For example: Entamoeba histolytica refers to one type of amoebae that causes flask shaped ulcers in the large intestine, Entamoeba is the genus and histolytica is the species. The genus always begins with capital letter and the species begins with small letter.
• A genus can have many species. Parasites of different species vary from each others in
the level of pathogenicity(virulence).
Important parasites:
Endoparasites
Helminths
Trematodes
Schistosoma mansoni and haematobium
Cestode s
Echynococcus granulosus Taenia saginata
Taenia solium Hymenolopis nana
Nematod es
Ascaris lumbricoides Hookworm Strongyloides stercoralis
Enterobius vermicularis
Protozoa
Entamoeba histolytica Giardia dudenalis
Gastrointestinal Protozoa
• Large intestinal protozoa:
Rhizopoda: Entamoeba histolytica.
Ciliophora: Balantidium coli.
• Small intestinal protozoa:
Flagellates: Giardia lamblia.
Sporozoa: Cryptosporidium parvum.
Cystoisospora belli.
Sarcocystis species.
General life cycle of protozoa
All protozoa except sporozoa have a direct life cycle which need one host.
They have only two stages trophozoite and cyst.
The cyst is the Non-motile, inactive form that can survives in extreme condition due to the presence of thick wall.
They multiply and are responsible for transmission of infection.
The trophozoite is the active multiplying form responsible for the pathology.
Human ingests cysts from fecally contaminated environment; the organism excysts; trophozoites multiply and attach to their habitat.
Trophozoites and cysts are passed in the feces.
Life cycle of
Entamoeba
histolytica
Entamoeba histolytica cyst
• Size: 12-15 μm in diameter.
• Rounded with well developed cyst wall.
• Nuclei: 1-4 identical to that of trophozoite (with
central karyosome and fine peripheral chromatin).
• Cytoplasm: may contain
chromatoid body= cigar
shaped bodies.
Entamoeba histolytica trophozoite
• Size: 10-60 approximately 20 μm in diameter.
• Nucleus with central karyosome and fine peripheral chromatin.
• Cytoplasm well differentiated into outer clear ectoplasm and inner granular endoplasm.
• Trophozoites are Irregular in shape due to
pseudopodia which are extension of the
ectoplasm and used by the parasite for
moving.
AMOEBIC LIVER ABCESS
Spread of amebiasis to the liver occurs via the portal blood.
The pathogenic strains evade the complement- mediated lysis in the bloodstream.
Trophozoites that reach the liver create unique abscesses with well-circumscribed regions of dead hepatocytes surrounded by few inflammatory cells and trophozoites.
Entamoeba histolytica
• Disease : intestinal and extraintestinal amoebiasis.
• Habitat: large intestine
• Definitive host: Human.
• Infective stage: cysts….never trophozoites.
• Mode of infection: ingestion of contaminated food or water containing the cyst
• Diagnostic stage: cysts or may be trophozoites.
• Diagnosis: Detection of cysts or may be trophozoites in stool samples of patients.
sero-diagnosis ( detection of antibody response) may be very helpful in extraintestinal amoebiasis since it is a closed lesion (no cysts or trophozoites in stool).
• Treatment: Metronidazole is the drug of choice.
Giardia duode
Giardia duodenalisnalis
Life cycle of Giardia intestinalis
Giardia lamblia trophozoite
• Size average 17x7 μm .
• Shape: Pear shape with anterior rounded
posterior tapering.
• 2 nuclei, central
karyosome, 2 axostyle dividing the body and 2 parabasal bodies.
• Flagella : 4 pairs ( anterior,
2lateral, and posterior).
Giardia lamblia cyst
• Size: average 12x8 μm.
• Shape oval with well developed cyst wall.
• Cytoplasm away from the cyst wall.
• Body containing 4 nuclei at one pole.
• 2 axostyle.
• 2 parabasal body.
Giardia duodenalis
• Disease : intestinal giardiasis.
• Habitat: small intestine
• Definitive host: Human.
• Infective stage: cysts….never trophozoites.
• Mode of infection: ingestion of contaminated food or water containing the cyst
• Diagnostic stage: cysts or may be trophozoites.
• Diagnosis: Detection of cysts or may be trophozoites in stool samples of patients.
• Treatment: Metronidazole is the drug of choice.
VECTOR BORNE
protozoa
MALARIA
• Malaria “Mal-air”. (mal: bad, aria: air) was given in the 18th century in Italy, as it was believed to
be caused by bad emission from wetlands
• Around 300-500 million clinical cases of malaria are reported every year, of which more than a
million die of severe and complicated cases of malaria.
•
Malaria ranks Fourth among the major infectious diseases in causing deaths after pneumococcal
acute respiratory infections and tuberculosis, then HIV then malaria.• Malaria parasites are transmitted from one person to another by the
female anopheles mosquito.
Plasmodium malaria
• Disease : malaria
• Habitat: red blood cells
• Definitive host: female anopheles mosquito.
• Infective stage: sporozoite.
• Mode of infection: bite of female mosquito
• Diagnostic stage: trophozoites inside red blood cells.
• Diagnosis: blood sample.
• Treatment: chloroquine .
Clinical picture
• Clinical incubation period: the time between infection and first appearance of characteristic malarial paroxysm
• It takes1-5 weeks according to the species.
• Fever that comes in attacks.
• Haemolytic anemia due to lysis of red blood cells--- symptoms of anemia
Leishmaniasis
• Disease : Cutaneous and Visceral leishmaniasis.
• Habitat: Macrophages
• Definitive host: female sand fly.
• Infective stage: larva.
• Mode of infection: bite of female sand fly
• Diagnostic stage: amastigote form in the macrophage
• Diagnosis:. sample from ulcer in cutaneous form and aspiration from bone marrow in visceral form
• Treatment: Amphotericin B (systemic) Pentavalent antimony( local)
Bone marrow aspiration
Bone marrow amastigotes
