Protozoan parasites information.

Background

There are many unicellular eukaryotic parasites that we use to lump into a group known as the protozoans (animal like protists). Within this larger group, protozoans were divided into smaller groups based on their locomotion, i. e. whether they used pseudopods, cilia or flagella. Classification has recently changed for all organisms. This protozoan group has been split into several groups.

Visit this page to see the new groupings for eukaryotes in general. Plants use to be considered close relatives of fungi. Now fungi are now considered more closely related to us, than to plants.

http://tolweb.org/Eukaryotes/3 Answer question one.

At one time, all old protozoan species that used pseudopods were placed in the subgroup Sarcodina. Now many species that were part of the group Sarcodina have been moved to other new groups, and we can find pseudopods through many various unicellular clades.

For example, locate the group Nuclearidae on the tree. These unicellular free-living amoeboid (with pseudopods) clade are now believed more closely related to fungi than most of the other protozoan species. They are placed in a group by themselves because of their discoidal or flattened mitochondrial cristae and other features of cell structure.

Some of the parasitic species that sometimes cause problems for human are now placed in the Amoebozoa. These are organisms that use pseudopods to move, although in some species the life cycle also involves a flagellated form. Amoebozoa is a large group containing mostly free living forms. Amoebozoa, with the fungi and Nuclearidae, belong to the Unikonts or a group that also contains the Animals.

The species among the Amoebozoa that causes the most problems for humans are species belonging to the genus Acanthamoeba. Acanthamoebae species have a world wide distribution and rarely cause fatal disease. However, infections of Acanthamoeba keratitis have been linked to contact lens use http://www.cdc.gov/parasites/acanthamoeba/epi.html + 180-183 (chapter 8). Infection can lead in rare cases to vision problems.

On even rarer occasion, species in this genus will enter and spread throughout the body damaging in the process, liver, spleen or in some cases, brain tissue (GAE or Granulomatous Amebic Encephalitis). Immuno-compromised individuals are most at risk, but sometime without explanation the disease develops in healthy individuals. http://www.cdc.gov/parasites/acanthamoeba/

Recently researchers have identified a new species, also free living, that can if gaining entry into the body. cause GAE. Balamuthia mandrillaris http://www.cdc.gov/parasites/balamuthia/

The problem with these free living amoebas that turn pathogenic is that little is known about how individuals become inflected, so little advice can be given with respect to prevention. It is fortunate that these diseases are rare, although if they lead to GAE, almost always fatal.

Answer questions 2 and 3. Pages listed in guide for your text are approximations based on my copy of the text. You will need in digital copies to search for the species mentioned, in the chapters cited section.

The Apicomplexa, an important group.

Probably the group most noted for containing human disease causing parasites is a subgroup of the Alveolates known as the Apicomplexa. This group includes Toxoplasma gondii and Crytosporidium spp. The first we have treated at some length, but you will be taking a trip with it and Crytosporidium, a smaller parasite belonging to another group through waterways and treatment facilities in Chapter 3.

The most famous member of this group, and one that was the a parasite of focus in guide one in this course, is the Plasmodium spp. responsible for malaria. http://www.cdc.gov/malaria/about/index.html

Babesia micros, mentioned in Chapter 8, pg. 186-188.(http://www.cdc.gov/parasites/babesiosis/), is also a member of this group, although it may be moved because its mitochondrial morphology is different. People who contract babesiosis suffer from malaria-like symptoms. As a result, malaria is a common misdiagnosis for the disease.

Coccidia species, which we will not discuss in detail, infect domestic fowl. You do need to know that this group is a problem for chicken farmers in North Carolina. The disease spreads quickly and a large farm can be destroyed in a short span of time, if infected individual are not quickly treated.

The Apicomplexa is an interesting group in general as it is mostly parasitic. The major defining characteristic of the this group are flattened vesicle-like structures, called cortical alveolae. which are found just underneath the plasma membrane. They are thought related to predatory flagellates that feed on unicellular algae by attaching and then sucking out the contents of the algal cell. The organ these predatory flagellates use appears similar to the apical organ used by the Apicomplexa to attach to and invade their host. Interestingly, most species of this group also exhibit a chloroplast remnant , the apicoplast, which is non-photosynthetic and may be involved in fatty acid and heme synthesis.

The life cycle is complicated and often some stages are completed in an secondary host. Plasmodium species that cause malaria will be used as an example of a typical life cycle.

The diagram below emphasizes the stages found in most complexional life cycles.

from http://sites.google.com/site/plasmodiumproblem/intro/about-malaria

After understanding the general life cycle, study the more complex life cycle diagram for malaria on the CDC website.http://www.cdc.gov/malaria/about/biology/ .

This is a complex cycle and so here are three web sites that will help you visualize important stages and answer homework questions.

Based on the life cycle of P. vivax https://www.youtube.com/watch?v=fk4tpGu8Ocg.

Based on life cycle of P. falcipaum https://www.youtube.com/watch?v=QWrYFNGYPww.

If you view these a few times, you will more easily be able to commit to memory important aspects of the CDC life cycle diagram.

Realizing that there are four species of Plasmodium that can affect humans complicates the life cycle at least in regards to detection even more. It is important to know which species is the cause of an individual's malarian symptoms as each species varies with regard to when merozoites are released. Merozoite release is associated with an episode or symptoms of malaria. If they are released every 42-47 hours it is know as tertian malaria (the day of release is counted), every 72 hours it is known as quartan malaria. P. malariae is a quartan malaria and the others are tertian species. The exception is P. vivax in which the episodes can occur daily or roughly every two days. So P. vivax can be quotidian (daily bouts) or tertian malaria.

The table below indicates other differences between the species biology and the disease they cause.

More information about the distribution and other aspects of the biology of Plasmodium that cause malaria is given at http://www.cdc.gov/malaria/about/index.html. Please review the biology and fast fact section and explore the link to Human factors and Malaria. http://www.cdc.gov/malaria/about/biology/human_factors.html

Answer questions 4-6.

 

Other important groups

Another group that contains human parasites of interest is the Excavates, which contain the subgroups Euglenozoa, Parabasalids,Heteroiobosea, and Fornicata. http://tolweb.org/Eukaryotes/3. You have already met many of these parasites.

For example Euglenozoa, a clade that contains many free living species, including the Euglenoids studied in most introductory classes, also contains trypanosomes. You have already learned about Trypanosoma cruzi. Your book considers this a potential problem parasite of the future. pgs. 173-180 and http://www.cdc.gov/parasites/chagas/

The CDC site considers Trypanosoma brucei, a parasite you were already introduced to in your text, a neglected but real problematic pathogen today, because of the economic toll and human misery inflected by sleeping sickness. http://www.cdc.gov/parasites/sleepingsickness/

Answer question 7 and 8.

Trichomonas spp. are members of the Parabasalids. You studied Trichomonas in the first assignment. This is an interesting group as it contains many of the unicellular eukaryotes that found in termites. You may remember viewing them in Bio. 181.

The Fronicata contain Naegleria fowleri, pgs. 183-185. Naegleria fowleri causes an acute meningoencephalitis leading to death in healthy children and young adults with a history of recent contact with fresh water. It is known as the brain eating amoeba. http://www.cdc.gov/parasites/naegleria/

Answer question 9.

The last species we will consider is also an Excavate, but belongs to the subgroup Fornicata. Giardia lamblia (also known as G. intestinalis) is a beautiful parasite, a preferred artist's model.

It is the most frequently diagnosed intestinal parasite. It causes as many problems for our pets as it does for humans. it is a rising problem for dogs in this state. It also is difficult to diagnose because it is such a small organism. On about page 66 of your text, a cyst of Giardia is compared to a cyst of Crytosporidium. http://www.cdc.gov/parasites/giardia/

Read chapter 3, then review the material on the CDC website on Giardia and Cryptosporidium spp.

Examine these urls to access background information on the two species,http://www.cdc.gov/parasites/giardia/ and

http://www.cdc.gov/parasites/crypto/

Chapter 3 also discusses a way a species already studied, Toxoplasma gondii, can be distributed in our waterways. I have included a url to background information on this species, but you already have copious notes on this species. Review your notes on this species.

http://www.cdc.gov/parasites/toxoplasmosis/index.html

Answer questions 10-13.