Fundamentals II: 11:00-12:00Scribe: Kristina Hixson

Thursday, October 28, 2009Proof: Jennifer Grimes

Dr. BenjaminDental Optometry ParasitologyPage 1 of 8

Dental Optometry Parasitology [1]
Ok today I’m going to talk about a bunch of my friends and most of these guys don’t really want to become pathogenic they want to live in us as long as they can and produce lots of kids and we will look at some of them.
Important Points for Parasites [2]
What is important for parasites that you should remember are the life cycle, some of these have very complex life cycles and we’ll try to stay away from having you all memorize any of the real detailed ones. Definitive host is the one that is the host where the organism spends the sexual part of its life cycle and that parasite really doesn’t want to cause damage so most of these guys really will live with us for a long time and not cause any trouble. Malaria is one where we are the intermediate host; the mosquito is the sexual host, so it doesn’t really mind causing us to get sick as long as it can get to the next mosquito. So we are the intermediate host for malaria.
A reservoir host is kind of anthromorphic* because that is the host that the organism lives in until it gets into a human. A lot of those are accidental parasites in humans. They aren’t normal in humans and it is a dead end they really don’t get from one to the other and we will discuss those in a little bit.
A vector is again anthromorphic* term and that is what gets the organism to us. Mosquitoes are the vector for malaria even though (he said intermediate host but I’m pretty sure he meant definitive host) they are the intimidate host for malaria.
What I’m interested in is how humans are infected. If you go overseas someplace with a lot of parasites you could figure out how to get a good parasite to bring home to me and if you would rather not bring me then maybe you will get an idea of how not to bring me one!
Migration patterns and where adults live in humans: So a lot of these organisms migrate from a lot of places in the tissue and some of them do damage while migrating and once they are adults they don’t cause as much damage after that.
Diagnostic form is humans is what I am interested in when they send me specimens I am suppose to diagnose what parasite these people have. I work in the lab and look for things and we look real hard to find not much.
Geographical distribution: so malaria is very rarely caught in the United States, occasionally every few years we will have a cases or two that is transmitted in the United States. In places you would expect like Michigan and New Jersey transmission of malaria has occurred there. So someone came in that was infected and infected the mosquitoes that were in the area and the mosquito infected other people. For the most part we do not have malaria being transmitted in the United States.

Sedimentation concentration [3]
A lot of our specimens are stool and this is how we work with stool. We get a cup of stool and you kind of mush it around and filter it through some filter paper. Now a days we have gloves so this is an old picture that I thought was good and when I started out we didn’t use gloves. So you filter it through some gauze and then centrifuge it and parasites mostly go here (top) and we extract the fatty part of the stool that goes to the top and this is formed once every thing is killed in here and you put this on a microscope slide and look at it and that is how you see the parasite.

Floatation concentration [4]
Another way to do it, even you can do it if you have access to a microscope is to make a saturate saline solution so use the sodium chloride and saturate it with water, then mix stool with that solution and then the organism will float. Then put a cover slip on them and the meniscus of the tube of the container and all of the parasites will be there. Then you pick up the cover slip up and put it on a slide then look at that under a microscope and you can see the eggs and the worms that you may have and you can do this with your dog or yourself.

Classification of Parasites [5]
Classification of Parasites: there are a lot of different kinds of parasites; one thing that is important is that they are all eukaryotes: all have a nucleus and that differentiates them from the bacteria that are also parasites that we call eukaryotic parasites and bacteria.
Protozoa are the single celled eukaryotes. We have Giardia lamblia which is a flagellate, this name is not important. Sarcodina which is Entamoeba histolytica which is the example that we use here and these are the amoeba, so amoeba is good enough. Sporozoa are a mixed bank, Toxoplasma is the cat one that everyone is worried about a cat transmitting to pregnant women, Cryptosporidium which is a GI organism and malaria which is Plasmodium. These are all 3 organisms which are in the same family but some of them live in the blood and some of them live in tissue and some of them live in the gut.
Helminths are what we think of when we think of parasites, these are the real worms. They are large. Some of them are 30cm long or so. Nematodes are the round worms and the example that we will use are Ascaris and if you read the book it says very common in the South East U.S.It is one of the organisms that cause a lot of trouble as long with hookworm because it zaps the energy out of the southern people. In reality though I haven’t seen a case contracted in Alabama since I’ve been here for 15 years or so.
Platyhelminths are the flats worms. They are divided into 2, the trematodes that are flukes. We have very few flukes in this part of the world that are transmitted to people, there are only a few. Cestodes are the tapeworms that we do see occasionally here. I’ve seen several cases of different kinds of tapeworm.

Entamoeba histolytica [6]
So we will start with a pathogen. This is Entamoeba histolytica which causes amoebic dysentery that is a severe disease in a lot of parts of the world, very uncommon here. I’ve seen it in a few people that have traveled recently to Africa and that is about all that I have seen. The infective form is a cyst and it has 4 nuclei in it and this is what we look for in the stool, to be able to see it. Actually the trophozoites in the stool, all of these forms will be seen in the stool (sorry confusing). We stain it and we are looking for something very small like this. It is 10 or 15 bacteria cross that is kind of the size. So it is bigger than a lot of bacteria and there are a lot of bacteria in the background here, but even though it is bigger it still mixes in with some of the stuff in the stool.
We can see then that it gets/eats and exists in the gut and the little guys come out and grow in the gut and invade the tissue of the epithelium of the gut and that can cause a lot of damage.

Entamoeba histolytica/dispar [7]
There are two things that look the same E. histolytica and dispar. Morphologically these look the same, so when we send out a report we are not sure if it is a pathogenic one histolytica or the non-pathogenic one dispar. There are further tests that can be done, but since we see so few here we only do the visceral* test.
Humans are the only host, so there is no reservoir host of E. histolytica so over the world, over where it is common where water is not handle well there is fecal contamination of water born. That is a problem and here we do not seem to eat uncooked stool very often so we wind up not transmitting these neat organisms.
The diagnostic form of the cysts or throphs cause amoebic dysentery and invades and likes the tissues in either the colon or it can actually escape the GI tract and can wind up causing abscess in the liver or brain or something like that which is for the more severe but usually pretty rare. It usually stays in the gut and causes dysentery.

Entamoeba histolytica/dispar [8]
This is a picture. These are the stool. This is a trophozoite so this is a stained organism that was moving before we stained it.

Non pathogenic ameba [9]
The really big problem is differentiating the non-pathogenic amoeba from the E. histolytica; it is really the main one that causes trouble. So E. dispar as we have discussed is morphologically identical. E. hartmanni, Entamoeba coli, Iodamoeba butschlii, E. nana, we do not need to remember those names, we just need to remember that there are a lot of other amoebas that we can see in stool and we actually report these out even though they really shouldn’t be treated but it indicates that person ate some stool that wasn’t cooked before he ate it and that indicates that there could be other things, other then that non-pathogenic amoeba so that is just a heads up for the clinician.

Entamoeba coli cysts [10]
This is Entamoeba coli which look a lot like E. histolytica; it really is difficult to differentiate. You can see that it has 8 nuclei which you have to focus up and down to see them in a cyst. It can be a little larger but for the most part it is similar to E. histolytica. I’ve known people who’ve had that and they have no trouble at all.

Giardia lamblia [11]
Giardia lamblia: this is the most common parasite that we’d find in the United States. This is a protozoa again, single cells, transmission are fecal, oral or water born. This is the one that if someone has been out in nature, way above where anyone could contaminate the water they could still get infected because their reservoir hosts are beavers and other animals. Where you think it is nice and clean water, the beaver has Giardia which can infect you. There are probably not many other things that beaver has that could infect you, but Giardia will. If you are taking a board test or something and someone is taking a bike ride in the mountains of Montana you don’t have to read any further because it is Giardia and that makes it easy.
Transmission is fecal and oral. Day care centers are real common. Mother-in-law went to work at the day care when her grandkids went to the day care and everyone got Giardia. When I sent her pictures of Giardia she wasn’t at all happy. Apparently it was unpleasant when she had it.
50% of people that are infected with Giardia are asymptomatic and they will shed the organism and be infectious to other people, but remain asymptomatic. A lot of places, 2-15% of stool that they look at areGiardia. Ours is much lower. We see about .6% of stools that we look for parasites in will have Giardia. We see it once every month or two.
Symptoms are that it causes malabsoption, so you don’t absorb food, you digest it but you don’t absorb it and this causes fatty frothy diarrhea. When I was 1st going in a lab, one of the techs was lining all of the stools up that we did, lots of kids stools that we did then, and he would pick out the Giardia. You could tell by their fatty, frothy, often not very dark colored, light colored and you would look at those and it was very accurate looking at just the consistency of the stool and being able to see Giardia.
Diagnostic forms are cysts and trophozoites that you see in the stool. It does not invade further then that, just in the small intestine and it prevents you from absorbing. Classically it was thought that they encoated the whole intestines so that you couldn’t absorb anything, but probably there is some toxin that they secrete that will also cause the inflammation and the decreased ability to absorb nutrients.

Giardia lamblia [12]
This is what Giardia looks like. It has 2 eyes in the trophozoite. It has flagella and it is really flat, so if you look at it you can see that it is flat and often if you look at specimens you can see them on their edge and see where they are. This is the cyst and it is the infectious form and it goes into the trophozoite and then go through binary fission to multiply and it just sits in there and is happy and there are lots of reservoir hosts for this, remember that.

Giardia lamblia [13]
This is what some of the cysts look like. They have 4 eyes actually.

Chilomastix mesnili: non-pathogenic flagellate [14]
This is a non pathogenic flagellate. We don’t need to remember the name. It is called Chilomastix and we see this very rarely here. We see very few non-pathogenic ones here.

Toxoplasma gondii [15]
This is an important organism, Toxoplasma gondii, this is the one where we worry about pregnant women handling litter boxes, because they can get infected and infect the fetus and cause all kinds of congenital problems. Miscarriage, mental retardation, and blindness are all things that Toxoplasma can transmit. The definitive host is the cat and this is where the sexual stage takes place. The organism multiplies in the gut. The cat’s feces contain sporozoites which are infectious and they infect other animals. The list of other animals that can be infected are essentially anything that travels around that you can see, so from rodents to pigs to cows to sheep and everything else. We can get infected 2 different ways, we can either eat the cat feces or we could eat an animal that has a latent infection. Once you are infected then you are infected pretty much for life. So these cysts will be in you and not multiplying, just sitting there because your immune system holds it in check, but as soon as something happens and your immune system goes bad then your immune system multiplies and causes lesions. This is very common cause of brain lesions in AIDS patients; it is much more common now then we have ever seen before. So you can see there we are infected by those cysts or by food. It proliferates then. If a woman is infected before she is pregnant and has the latent infection there is no risk to the infant/fetus, but if she is infected for the 1st time during the pregnancy then the organism will go to the infant and if it is early in the infection it will cause a miscarriage.

Diagram [16]
Another picture that shows kind of the same thing but is more graphic. Cats are the definitive host, pigs, and everything else are reservoir hosts and cats are I guess also reservoir hosts for humans. Tissue cysts are contained in meat and we eat those and we get tissue cysts in the brain and in muscles. Accidental transmission: transplantation can cause it.
People here in this part of the world get infected about 1% per year. So you can calculate how old you are and that is a percent, your risks of being infected are depending on how close you have been to cats and how rare you like your beef and pork. It is accumulative over life.
A primary infection during pregnancy or shortly before conception: it goes to the placenta and could infect the kid. Children and adults then 10% have lymphadenitis and is really rarely diagnosed as being a disease. You don’t feel good and have mononucleosis type symptoms, though sometimes it could be pretty severe. I know some adults here that have had pretty bad symptoms for nearly a year and she was diagnosed by a biopsy.
90% are asymptomatic and they don’t even know when they’ve been infected and they are asymptomatic, latently infected for the rest of their life, because they are immunosuppressed with transplants or HIV or something like that.

Congenital Toxoplasmosis [17]
During pregnancy this is what happens. If you are infected during the 1st trimester it rarely, a low percent, go to the fetus, but if it does then you will have severe sequelae so stillbirths.
In the 2nd trimester more of them go to the fetus but less sequelae.
In the 3rd trimester it will be often transmitted to the kid but it is really pretty rare that they will have sequelae. So early in the pregnancy there is a low transmission rate but if it does transmit to the kid it is usually pretty bad.
In France they had a custom that raw meat juices were good drink during pregnancy. Women or girls wouldn’t eat raw meat juices until they were pregnant and then they would eat raw meat juices and this caused a huge amount of Toxoplasmosis in France. This happen 20-30 years ago, but since then they’ve had very good public announcement about health and so incentive to get people to eat their raw meat juices earlier.

CNS lesions found in immunosuppressed patients [18]
This is what the CNS lesions looked like.