medical parasitology lec.6 introduction to medical ... · vaginalis, trichomonas tenax, and...

Dr. Abdullah Ahmed Hama

PhD. Molecular and Medical Parasitology

Sulaimani University College of Pharmacy

Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 4 part1

Microbiology/ parasitology and virology

Protozoa/ Class: Mastigophora (Flagelates)

Giardia lamblia

Outline: • Introduction to flagellates

• General characteristic of flagellate.

• Classification of flagellate according to the habitat.

• Giardia lamblia and Trichomonas spices • Morphology and life cycle and transmission

• Pathogenesis

• Disease

• Laboratory diagnosis

• Treatment

• Prevention and control

Introduction • Flagellates: are a major group of parasites with medical importance that inhabit

the intestinal and urogenital tract.

• These organisms have a simple life cycle, and at least three of the following four

species do not have a cyst stage but only a trophozoite stage, during which unlike

many protozoa they are infective. These are Dientamoeba fragilis, Trichomonas

vaginalis, Trichomonas tenax, and Trichomonas hominis, although there are others

that may be found in both cystic and trophozoitic forms, some these organisms may

be characterized by exhibiting an undulating membrane, the most medical

important flagellates are Giardia lamblia and Trichomonas vaginalis.

General characteristic of flagellates

1- They are protozoan unicellular organisms.

2- They have primitive organelles.

3- They have no organ for digestion, excretion, secretion, etc.

4- The hydro genome are present in most flagellates, that

serve as mitochondria.

5- Characteristic feature of flagellate is Locomotion organ

(Flagella).

Giardia lamblia

• After that other researchers have named the species of the human (G. lamblia). In 1879, the

first time Giardia was used as a genus name. In 1888, Blanchard suggested the

name Lamblia intestinalis , which Stiles then changed to G. duodenalis in 1902.

Dr. Abdullah A. Hama Medical Parasitology Lec.7 Text book: 978-1-4354-4816-2 Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 4 part1

• Giardia was initially described by Van Leeuwenhoek in 1681 as he was examining

his diarrheal stools under the microscope. The organism was described in greater

detail by Lambl in 1859, who thought the organism belonged to the

genus Cercomonas and called Cercomonas intestinalis.

Giardia lamblia

• Giardia lamblia ( Giardia intestinalis, Giardia duodenalis) is a flagellated

unicellular eukaryotic microorganism that commonly causes diarrheal

disease throughout the world. It is the most common cause of waterborne

outbreaks of diarrhea in the United States and is occasionally seen as a

cause of food-borne diarrhea .

• In developing countries, there is a very high prevalence and incidence of

infection, and data suggest that long-term growth retardation can result from

chronic giardiasis . In certain areas of the world, water contaminated with G.

lamblia cysts commonly causes travel-related giardiasis in tourists .

Morphology

• Trophozoites of G. lamblia are either oval or pear shaped, and the size

ranged from 9 to 21 μm in length and 5 to 15 μm in width.

• The trophozoite form of this organism has been likened to a “monkey face” with

two nuclei as eyes that contain central karyosomes which lack peripheral

chromatin.

• The trophozoite stage is bilaterally symmetrical with an axostyle evenly dividing

the cell down the middle.

• Two curved structures, called median bodies, lie parallel to each other and

perhaps contribute to the metabolism of the parasite.

• Trophozoite

Morphology

• Cysts : The cyst is oval shape and ranges from 8 to 17 μm length by 7 to 10 μm width.

The karyosomes may be less concentric than those of the trophozoites, and in the mature

cyst, four median bodies are present.

• Longitudinal fibers are visible and four nuclei are seen in the cyst form of G. lamblia.

• There may be a clear zone between the cytoplasm and the cell wall, unlike that of the

trophozoite, are responsible for transmission (infective stage) and can

survive several months out side the host or in water.

• each cyst produces two trophozoites.

General characteristic of Giardia lamblia •They are unicellular Eukaryotes parasite

• Facultative anaerobes,Carbohydrate metabolism is

anaerobic

• They have not mitochondria

• They are extracellular parasites (intestine)

•They can not invade the host cell.

•They adhere to plasma membrane of host cell

•The contact-dependent cytotoxicity was common in giardia

•The infection cause mechanical damage to host tissues

Infection with the Giardia lamblia

• Name of pathogen: Giardia duodenalis is the most common name used.

• G. intestinales and G. lamblia are also used.

• Host: can parasitize the intestinal tract of a wide range of vertebrates,

including humans.

• Epidemiology: Disease is prevalent in children attending day care centers.

• In addition the domestic dog and certain wild animals serve as hosts.The

distribution is cosmopolitan (word wide).

• Transmission: Giardia is predominantly transmitted through ingestion of

food or water contaminated with cysts and direct from hand to oral (fecal oral

route) .

Giardia lamblia

Karyosom

Adhesive disc

Median body Axostyle

Cell wall

Flagella

Lifecycle of Giardia lamblia

• Infection of a host is initiated when the cyst is ingested with contaminated water or

food and may be through direct fecal-oral contact.

• The cyst is relatively inert (inactive), allowing prolonged survival in a variety of

environmental conditions. After exposure to the acidic environment of the

stomach, cysts excyst into trophozoites in the proximal small intestine.

• The trophozoite is the vegetative form and replicates in the small intestine, where it

causes symptoms of diarrhea and malabsorption. After exposure to biliary fluid,

some of the trophozoites form cysts in the jejunum and are passed in the feces,

allowing completion of the transmission cycle by infecting a new host.

Giardiasis Pathophysiology:-

•Giardia colonizes the upper small intestine and cause Villous blunting,

Lymphocytic infiltration and malabsorption.

•No tissue invasion-high number of trophozoites present in the duodenal

cause diarrhea called steatorrhea.

Symptoms:

1.Diarrhea with loose, fool-smelling stools

2.Flatulence

3.Abdominal cramps and bloating

4.Nausea and anorexia

5.Weight loss and Malabsorption

• Identification of cysts or trophozoites in fecal specimens by direct and indirect

microscopic examination

• Biopsy from small intestine

• Stool culture for G. lamblia growth which is time required an relatively expensive.

•The enzyme linked immune sorbent assay (ELISA) for the detection of Giardia

antigen in fecal specimen is so reliable.

Laboratory Diagnosis

Metronidazole: (250 mg x 3 for 5-7 day)

Tinidazole- not approved in the US. Single dose of 2 g.

Furazolidone- approved by the FDA for giardiasis

Paramomycin- used for pregnant women

Nitazoxanide: recently approved for giardiasis and cryptosporidosis in

children

Treatment

Questions? 1. Draw a typical trophozoite of Giardia lamblia with the

basic structure.

2. Explain the pathogenesis of G. lamblia.

3. Write the infective and diagnosis stages of G. lamblia.

4. Enumerate the main flagellates which cause human

infection.

5. Write the laboratory diagnosis methods of Giardia

lamblia .

Dr. Abdullah Ahmed Hama

PhD. Molecular and Medical Parasitology

Sulaimani University College of Pharmacy

Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 4 part 2

Classification of Viruses

• Some facts that should be in mind when talking about the process of virus

classification:

A. The amount of information available in each category is not the

same for all viruses.

B. The way in which viruses are characterized is changing rapidly.

C. Genome sequencing data are advancing taxonomic criteria [Gold

standard method] (eg, gene order) and may provide the basis for the

identification of new virus families.

Basis of Classification:

1. Virion morphology, including size, shape, type of symmetry, presence or absence of

peplomers (glycoprotein spike on a viral capsid or viral envelope) and presence or absence

of membranes.

2. Virus genome properties, including type of nucleic acid (DNA or RNA), size of genome in

(kb) or (kbp), strandedness (single or double), whether linear or circular, sense (positive,

negative, ambisense), segments (number, size), nucleotide sequence, G + C content, and

presence of special features [repetitive elements, isomerization, 5'-terminal cap, 5'-terminal

covalently linked protein, 3'-terminal poly(A) tract].

3. Physicochemical properties of the virion, including molecular mass, buoyant density, pH

stability, thermal stability, and susceptibility to physical and chemical agents, especially

ether and detergents.

4. Virus protein properties, including number, size, and functional activities of structural

and nonstructural proteins, amino acid sequence, modifications (glycosylation,

phosphorylation, myristylation:is a lipidation modification), and special functional

activities (transcriptase, reverse transcriptase, neuraminidase, fusion activities.

5. Genome organization and replication, including gene order, number and position of

open reading frames, strategy of replication (patterns of transcription, translation), and

cellular sites (accumulation of proteins, virion assembly, virion release.

6. Antigenic properties.

7. Biologic properties, including natural host range, mode of transmission, vector relationships, pathogenicity, tissue tropisms (is the cells and tissues of a host that support growth of a particular virus or bacterium), and pathology.

Viral Families A. DNA Viruses

RNA Viruses

Nomenclature of Viruses

For virus nomenclature, different approaches were followed which are summarized below:

1. Named after the diseases: [Measles virus, smallpox virus……]

2. Name after the places where the disease first reported: [ Newcastle disease virus, Ebola virus,

Norwalk virus, Bunyaviridae]

3. Host and signs of disease: [Tobacco mosaic virus, cauliflower mosaic virus brome mosaic virus]

4. Latin and Greek words: [Coronaviridae – “crown”; Parvoviridae – “small”]

5. Virus discovers: [Epstein-Barr virus]

6. How they were originally thought to be contracted: [Dengue virus (“evil spirit”), influenza virus

(the “influence” of bad air)]

7. Combinations of the above: [Rous Sarcoma virus]

The classical methods and terms used in other classification systems for other

microorganisms are not followed in virus classification, and do not obey to the

biological taxonomy.

The virus classification systems are according to the following:

a. Classical system: [Animal, Plant, Bacterial virus]

b. Genomic system: Baltimore classification

c. Serology: Classification based on Diagnostic virology [Infectious

bronchitis virus (IBV) of chickens.

Baltimore Classification of viruses

• This system was suggested by David Baltimore, and according to this system

there are seven main classes or groups of viruses. The main criteria depended

in this system are genome type and mode of replication and transcription

Class Description of genome and replication strategy Example of animal virus

I Double stranded DNA genome Herpesvirus, poxvirus

II Single stranded DNA genome Chicken anemia virus

III Double stranded RNA genome Reovirus

IV Single stranded RNA genome plus sense Poliovirus

V Single stranded RNA genome minus sense Influenza virus, Rabies virus

VI Single stranded RNA genome that replicated with DNA

intermediate

Retrovirus

VII Double stranded DNA genome that replicates with RNA

intermediate

Hepatitis B virus

Questions??? Thanks

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