micro sheet #8 of Dr 7assan - Sura Al-Amar & Yasmin Hzayyen

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micro sheet #8 of Dr 7assan - Sura Al-Amar & Yasmin Hzayyen

Post by Shadi Jarrar on 14/5/2011, 10:06 pm

بسم الله الرحمن الرحيم

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http://www.4shared.com/document/vmC9e_uO/Micro_8.html
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By the Name of God
Lecture 8 - Microbiology 8/5/2011
Dr. Hassan


In the previous lectures we discus the types of worms (multicellular parasite); which are Nematodes and Platyhelminthes, and we classified platyhelminthes to tapeworms and Trematodes (flukes). Our lecture today will be about Tapeworms (Cestodes) and Type of Trematodes which is Schistsoma.

Tapeworm (Cestodes)

Tapeworms in general are composed of two major parts…
* Head (scolex) which composed of suckers, hooks (Rostellum) or sucking grooves.
* Proglottids which are multiple segments represent the flat body of the worm; those proglottids are of three types:

-- Immature proglottids (start immediately after the neck).
-- Mature proglottids (in the middle portion, composed of male and female sexual apparatus).
-- Gravid Proglottids (in the distal end, which is Uterus full of eggs).

The sizes of Tapeworms differ from (1cm - 10m), and the size determine the number of proglottids of the worm; the smaller ones have only 3 proglottids while the largest composed of more than 2000 proglottids. They are Hermaphrodites that the female and male sexual apparatus are present in the same proglottid which is the mature proglottid.

Human usually acquire the infection of Cestodes when undercooked flesh containing larvae is ingested. There are four medically important cestodes; two of them are under the genus Taenia which are; Taenia Solium, Taenia Saginata, the other two are Diphyllobothrium Latum and Echinococcus Granulosus.

Taenia

Most of the Taenia has the same morphology of the eggs with some exception in some species. The egg has striations on the outer border and inside it we have six-hooked embryo (Hexacamp).

Generally all Taenia require an intermediate host except one. It’s as tissue Nematodes (Filarias) which require intermediate host, not as the luminal Nematodes which don’t require.
In the intermediate host, the morphology of the worm (lesion) is called Cysticercus which is balloon or sac of yellowish fluid with an invaginated Rudimentary scolex.
Among Taenia, the most common are Taenia Solium and Taenia Saginata.
1. Taenia Solium (Pork tapeworm)

It’s composed of four suckers and circle of hooks. Its length is 1000 proglottid and the intermediate host is Pig.
Humans which are the a dead-end intermediate host and a Primary Host, are infected by eating undercooked pork OR by ingested the worm's eggs found in food or water contaminated with human feces.

Life Cycle
1. A person have Taenia solium lives usually in the jejunum and may extend to the lower parts, Now the eggs of T.solium are not released inside GIT (gastrointestinal tract) instead the Gravid Proglottid (that contain the eggs) detach daily from the jejunum and passed in the feces. When eggs pass into feces there are two possibilities to happen; either eggs going to grass (or anything eaten by pig) OR going to water and food eaten by humans.




2. Now when the pig accidentally eat the grass contaminated by eggs, the hexacamp (six-hooked embryo present inside egg)emerge from each egg in the pig’s intestine, attaching to the intestinal wall and penetrate it, then carried by the blood stream to be distributed all over the body of Pig especially the skeletal muscles and viscera of Pig.
When hexacamp reaches the muscles and viscera, it will give rise to Larvae (cysticercus) where they remain until eaten by a human.

3. Now a human eat undercooked pork, so taken the cysticercus present in the muscles of pig, the Cysticercus attach and invaginated to the wall of small intestine, and from the neck region of larvae, they will get proliferated to become an adult Taenia solium (one worm) live in the jejunum of the human. And By this the Life Cycle Complete


The symptoms are connected to the GIT but they are not really very well marked, sometimes it will live 20 years with no symptoms or very little symptoms such as abdominal pain and maybe cause little malnutrition.

! SO as a conclusion, Pigs are infected by warm eggs. But we found in pigs Cysticercus.
! Humans infected by eating Cysticercus in pork OR eating eggs with contaminated food.

In more Serious Condition, which called Cysticercosis, human can infected by Taenia solium when ingest the worm eggs found in food or water contaminated with human feces. The eggs give hexacamp which is release in your small intestine, attach there and will become distributed in your body and become Cysticercus in the organs because there is such similarity between human flesh and pig flesh. Here u might have more than one worm
because you ingest eggs.

! So as a GENERAL RULE, if you ingest Cysticercus you'll have one worm otherwise if you ingested eggs so more than one worm.
! Pigs are not the source of the eggs that cause human cysticercosis.




That Cysticercus in organs will calcify (die) after couple of years and when they die they produce an inflammatory reaction whenever they are, and produce nodules in the muscles. They will produce an inflammatory reaction in the Brain and eye.

In the Brain they cause fibroid lesion, which is mainly lead to Focal Epilepsy (meaning by this focal lesion, electrical irritation and discharge electricity occur) but it will become small and local meaning epilepsy in the arm or leg only, and it's the major symptom of cysticercosis.

In The Eye, the Cysticercus will produce Partial blindness (Corioretentities) in which part of the retina destroys.


2. Taenia Saginata (Beef tapeworm)

The major difference between Taenia Solium and Taenia Saginata is the intermediate host and they also differ in the length, suckers and hooks. The differences are…

* The intermediate host here is the cattle. Human is Primary Host ONLY.
* It’s composed of four suckers but NO hooks.
* Its length is around (2-3m) so longer than Taenia solium.

The life cycle is similar to That of Taenia Solium but ….
* The human infected when eaten undercooked beef contain larvae (Cysticercus) OR eat eggs and it will not produce malnutrition.

* It doesn’t cause cycticercosis in human because when you eat eggs and the eggs produce hexacamp, the hexcamp in Saginata will NOT produce Cysticercus because the environment of human differ from that of cattle. So human will NOT be an Intermediate host for Saginata even if you eat eggs, the eggs will not able to produce Cysticercus so no cysticercosis.

3. DiphylloBothrium Latum (Fish tapeworm)

It’s the longest Tapeworm of all types; its length is about 10m and that’s why it will extend to the terminal ileum. It’s composed of head (scolex) differ from other tapeworms that its elongated and composed of two sucking grooves instead of four suckers, and the proglottid are the same.

It has two intermediate host and Human Is the Primary Host. The eggs of fish Tapeworm differ from the previous ones, its resemble trematodes egg, it's composed of operculum and that’s why it must go to water.

Life Cycle
1. The egg of DiphylloBothrium come from feces of infected human and go to fresh water to produce ciliated embryo which swim in water and this embryo will be eaten by small animals as Copepod Crustacea ( 1st Intermediate Host) and after that this will be eaten by Fish (2nd Intermediate Host).

2. Now if you eat undercooked fish you will take the tapeworm which will go to your small intestine and this will Cause Vitamin B12 deficiency so Malnutrition occurs.
Vitamin B12 deficiency leads primarily to Megaloblastic anemia and secondly leads to neurological complication such as peripheral neuropathy, posterior column of spinal cord will be affected as well as the proprioception and balance of leg will be affected.





4. Echinococcus Granulosus (Dog Tapeworm)

It’s a tapeworm of canine animals (primary host) as Dogs. The Intermediate Host is Herbivores mainly the sheep and humans become accidentally intermediate host. Its very small and even one of the smallest Tapeworm (1cm in length and composed of 3 proglottid). Have scolex, Suckers and hooks.

Life Cycle

1. The worms are present in the Dog’s intestine, liberate eggs into the Grass by defecating, the eggs will ingested by sheep (or human), hexacamp will release in Intestine of sheep (Intermediate host) and give rise to cyst (Lesion or Morphology of worm in Intermediate host) in different organs mainly in the liver so cause tumor in the right hypochondria, and 2nd most to be affected is the lung, also affect Brain, kidney, Bone and under skin.

These Cysts start as small cyst measures about 1 cm and Get bigger and bigger to be 10-15 cm in diameter. This Cyst is composed of 2 layers…:
- Outer Layer (Laminated) its acellular layer, no Nuclei, like a capsule.
- Inner layer (Germinal Layer), Cellular of Single cells.

How Does the Cyst Get Bigger and bigger?
1. Now the Cyst starts as Mother Cyst (composed of 2 layers). From the inner aspect of the Germinal Layer of the Mother Cyst -That Present in the Intestine of the intermediate host- you will get budding of new cysts known as Daughter Cysts (composed of 2 layers)

2. Now from inner aspect of the Germinal Epithelium of daughter cyst we will have budding of new cysts known as Granddaughter Cysts (composed of 2 layers).

3. Now inside Daughter Cysts or Granddaughter Cysts, we get a single layer germinal epithelium known as Brood Capsule (single layer cyst) and NO laminated layer.

4. Now from brood capsule we get invaginations develop into small Protoscolices (called hydatid sand) and appear under the microscope similar to sand.

This LARGE cyst which composed of Mother Cyst, Daughter Cysts, Granddaughter Cysts and Protoscolices is called Hydatid Cyst which acts as a space occupying lesion and cause Hydatid disease in the Intermediate Host.


2. Now Dog ate sheep which has hydatid cyst, this cyst go inside dog and each hydatid sand which is protoscolex will produce scolex and cause disease in Dog.
By that the life cycle complete





But if human eat this sheep so no problem because our small intestine differ from that of Dog so no disease will develop.


3. Humans become accidentally intermediate host, because the eggs are present in the saliva and feces of Dog, so anyone come in contact with dog or touch the saliva or feces of dog, this will result in eggs on human's hands and skin, leading to ingested eggs with food and disease is developed. Shepherd and children are the most to be affected.

Treatment
You can use Drugs to treat with or without surgery, and when remove be sure that u don’t rupture the cyst, if so, two complications will appear:
- Will produce type 1 hypersensitivity (anaphylaxis)
- Rupture will produce Secondly spread disease to other organs because of the distribution of the hyadatid sands.

Hydatid cyst really resembles the tumor that the cyst; grows in size, proliferates and metastasized from liver to lung. Its not cancer but resemble cancerous characteristic.




Trematodes, also called flukes

General characteristics of the Trematodes:
-Leaf-shaped worms; flat.
-They have two suckers, bifurcate blind-ended GI tract.
-They are hermaphrodites; having both female and male organs.
-Their eggs are large, oval and they have an operculum.

Some of them live in the liver/ lung/ intestine… We are interested in SCHISTOSOMA, it causes Bilharzias. -Egypt has a lot of Bilharzias cases; schistosomiasis is endemic there.
Schistosoma is an exceptional group; the worm is not leaf-shaped…

((Now, the Dr suddenly realized that he already talked about Schistosoma, so we asked him to give us a revision, since it’s already been explained. Don’t forget to refer to one of the last H.Os the Dr gave us))

So from the beginning Schistosoma is exceptional; it is different than the other worms in the group Trematodes:

1. It has separate sexes; there are males and there are females as well.
Like other Trematodes, they have a bifurcate blind-ended GI tract, two suckers and a tegument with spines on it.
2. They look more like Nematodes than Trematodes with their leaf-like shape.
The Dr is showing a female Schistosoma and a male that is a little flat but elongated, they live together in pairs all their lives. They live in the blood stream.
They are three species:

1. Schistosoma H/Ematobium  in the bladder.
2. Schistosoma Mansoni  in the large intestine.
3. Schistosoma Japonicum  in the small intestine.

Depending on Schistosoma species they live in the post capillary venules either in the small intestine or large intestine or bladder.

They live quite happily in the blood stream, because they camouflage themselves; they cover themselves with MHC molecules and ABO blood group antigens, that’s why they are not recognized by the Immune System.

So they can live there for about 15 years and sometimes even more (no immunological reaction against them). When they die the story becomes different; they produce an inflammatory reaction, but as long as they’re alive, they are covered by these molecules and are not bothered by the Immune System.

What do they do?
They lay eggs which are immunogenic.
((Look at figure 13-3))

They don’t have an operculum, but they do have spines.

The Schistosoma h/ematobium species has a terminal spine. While, Schistosoma mansoni has a lateral spine and Schistosoma japonicum has a spine but it’s really rudimentary and it’s located lateral as well.

The eggs are laid in the blood stream, but because of the spines they stick to the wall of the venules and penetrate through the wall of them into the wall of the organ. Eventually, they will reach the lumen of the organ; because they want to get out of the body.
They can come out through feces (Mansoni and Japonicum) or through the urine (h/ematobium).

Now figure 13-2 (The life cycle of three main species of human Schistosoma)

Somebody is defecating or urinating in the water  the egg disintegrates
It releases the Miracidium that goes to an intermediate host (fresh water snail) it goes through the snail  multiplies through the sporocysts or radia  then gives rise to cercariae  cercariae released from infected snails into the water and everybody who come in contact with the water infected by cercariae either by washing your clothes or by swimming or irrigating your feet, whatever happens these cercariae will penetrate through the skin (by this they will produce itching and skin rash)  they will start their development in the body. (Skin subcutaneous tissues  blood  liver). In the liver they will start their maturation, they need few weeks to become adult worms (2.5 cm in length)  then they will pair (each male will choose a female)  they will migrate “retrogradely” عكس تيار الدم and they will go to their respective organ (post capillary venules of the small intestine/ large intestine/ bladder). As we said before, they won’t produce an immunologic reaction.

During their development, the human could show symptoms of an acute illness (fever, malaise, headaches, unwell feeling, nausea… things like this) this will be called as acute Schistosomiasis (Katayama fever), this is only experienced in the early stages of infection, a generalized illness, but once these worms mature and settle in the post capillary venules of the organs, there are no symptoms. The symptoms will be really localized to the position of the eggs(general features of chronic Schistomiasis):

- H/ematobium species  Eggs deposited in the wall of the bladder  inflammation of the wall of the bladder; (1) Dysuria. (2) Inflamed bladder. (3) Fibrosis may actually obstruct the ureters. (4) Haematuria. (5) Hypo erythrosis. (6) They may cause inflammation in the uterine tubes. (7) May invade the prostate or other places and produce inflammations there. (8) If it is diagnosed too late, it may develop into a bladder carcinoma (when there is haematuria of course).

- Japonicum and mansoni are not so much cancerous; (1) Abdominal pain. (2) Blood in feces. (3) Diarrhea… all of these are local symptoms to the inflammatory process that would take its place in the intestines.


Sometimes, the eggs may be carried away with the blood stream; in case of japonicum and mansoni, they will go to the portal circulation to the liver. They will settle in the liver and start their inflammatory fibrotic process and this is mainly periportal; the liver is not affected, the liver cells do not die, fibrosis obstructs the blood flow ( NOT CIRRHOSIS; as it destructs the hepatocytes), this will produce back pressure that is known as “portal hypotension”; the blood will try to escape from the portal circulation to the systemic circulation, wherever this happens in the anastomosis, it will produce dilatation in the veins, i.e. varicose, and this can happen in three areas in the body (wherever there is anastomosis between the portal circulation and the systemic circulation) 1. Rectum hemorrhoids (not so serious because most people would end up with hemorrhoids anyway !) 2. Esophagus  esophageal varices; the problem is that they bleed… a lot, and it’s hard to stop such bleeding, it can cause death. 3. Umbilicus  caput medusa.

When the eggs go to the systemic circulation, they will go to the lungs  fibrosis in the lungs  pulmonary hypertension  right-sided heart failure ( cor pulmonale); R-sided heart failure could be secondary to left-sided heart failure or due to lung pathology.

Diagnosis: eggs in the urine or feces.















Sura Al-Amar & Yasmin Hzayyen
Lecture 8 for Dr Hassan
08.05.11 Microbiology
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Shadi Jarrar
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عدد المساهمات : 997
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Re: micro sheet #8 of Dr 7assan - Sura Al-Amar & Yasmin Hzayyen

Post by Dyala Al-Armouti on 27/5/2011, 8:53 pm

by sura,, thanx 4 her :

"Correction for sheet 8 Micro, Dr.Hassan...

- page 4 line 17 , the right sentence is " the human infected when eaten undercooked beef contain larvae(cysticercus) ONLY Not by eating eggs because eggs will not produce cysticercus.
- page 6 line 27 , " Granddaughter cyst, Brood Capsule and protoscolices"

Sorry for that , nd Good luck all"
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Dyala Al-Armouti

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