Category Archives: Parasites

Friday Fellow: H. pylori

by Piter Kehoma Boll

I already introduced three species of bacteria here, all of them free-living and/or friendly little ones. But we all know that many bacteria can be a real annoyance to us humans, and so it’s time to show some of those, right?

I decided to start with one that I thought to have living inside me some time ago (but it happened that I don’t), and this is the ill-tempered Helicobacter pylori, which as usual lacks a common name, but is commonly called H. pylori for short by doctors, so that’s how I’ll call it.

empylori

Electron micrograph of a specimen of H. pylori showing the flagella.

The most common place to find the H. pylori is in the stomach. It is estimated that more than half of the human population has this bacterium living in their gastrointestinal tract, but in most cases it does not affect your life at all. However, sometimes it can mess things up.

H. pylori is a 3-µm long bacterium with the shape of a twisted rod, hence the name Helicobacter, meaning “helix rod”. It also has a set of four to six flagella at one of its ends, which make it a very motile bacterium. The twisted shape, together with the flagella, is thought to be useful for H. pylori to penetrate the mucus lining the stomach. It does so to escape from the strongly acidic environment of the stomach, always penetrating towards a less acidic place, eventually reaching the stomach epithelium and sometimes even living inside the epithelial cells.

In order to avoid even more the acids, H. pylori produces large amounts of urease, an enzyme that digest the urea in the stomach, producing ammonia, which is toxic to humans. The presence of H. pylori in the stomach may lead to inflammation as an imune response of the host, which increases the chances of the mucous membranes of the stomach and the duodenum to be harmed by the strong acids, leading to gastritis and eventually ulcers.

The association between humans and H. pylori seem to be very old, possibly as old as the human species itself, as its origin was traced back to East Africa, the cradle of Homo sapiens. This bacterium is, therefore, an old friend and foe and it will likely continue with us for many many years in the future.

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References:

Linz, B.; Balloux, F.; Moodley, Y. et al. (2007) An African origin for the intimate association between humans and Helicobacter pyloriNature 445: 915–918. https://dx.doi.org/10.1038/nature0556

Wikipedia. Helicobacter pylori. Available at < https://en.wikipedia.org/wiki/Helicobacter_pylori >. Access on August 5, 2017.

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Filed under Bacteria, Friday Fellow, Parasites

Friday Fellow: Operculate Acrochaete

by Piter Kehoma Boll

Last week I introduced a red alga, the Irish moss. Today I’m bringing another alga, this time a green one, but this is not an ordinary green alga, but a parasite of the Irish moss! So let’s talk about Acrochaete operculata, or the operculate acrochaete as I decided to call it in English, since obviously there would be no common name for an alga parasite of another alga.

Discovered and named in 1988, the operculate acrochaete is an exclusive parasite of Chondrus crispus. The infection occurs when flagellate zoospores of the parasite settle on the outer cell wall of the Irish Moss, where they start their development and digest the cell wall, penetrating the tissues of the host. In sporophytes of the Irish moss, the operculate acrochaete digests the intercellular matrix and spreads through the frond, while in gametophytes the infections remains localized, forming papules. The damages caused by the green alga lead to secondary infections by other organisms, especially bacteria, and the infected fronds end up falling apart, completely degradated.

ccrispus

A frond of the host (Chondrus crispus) to the left and the parasitic Acrochaete operculata that infects its tissues to the right. Photo extracted from chemgeo.uni-jena.de

As mentioned last week, the sporophytes and gametophytes of the Irish Moss have different forms of the polysaccharide carrageenan and this seems to be the reason why the parasite infects both forms differently. The sporophytes have lambda-carrageenan, which seems to increase the virulence of the parasite, while the kappa-carrageenan of the gametophyte seems to limit the green alga’s spread.

Since its discovery, the operculate acrochaete and its interaction with the Irish moss has been studied as a way to both reduce its damage on cultivated crops of the red alga and as a model to understand the relationship of plants and their pathogens.

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References:

Bouarab, K.; Potin, P.; Weinberger, F.; Correa, J.; Kloareg, B. (2001) The Chondrus crispus-Acrochaete operculata host-pathogen association, a novel model in glycobiology and applied phycopathology. Journal of Applied Phycology 13(2): 185-193.

Correa, J. A.; McLachlan, J. L. (1993) Endophytic algae of Chondrus crispus (Rhodophyta). V. Fine structure of the infection by Acrochaete operculata (Chlorophyta). European Journal of Phycology 29(1): 33–47. http://dx.doi.org/10.1080/09670269400650461

Correa, J. A.; Nielsen, R.; Grund, D. W. (1988) Endophytic algae of Chondrus crispus (Rhodophyta). II. Acrochaete heteroclada sp. nov., A. operculata sp. nov., and Phaeophila dendroides (Chlorophyta). Journal of Phycology 24: 528–539. http://dx.doi.org/10.1111/j.1529-8817.1988.tb04258.x

 

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Filed under Algae, Botany, Disease, Friday Fellow, Parasites

Friday Fellow: B. coli

by Piter Kehoma Boll

It’s time to give more space for parasites, including human parasites! So today our fellow comes right from the stool of many mammals, including humans. Its name is Balantidium coli, or B. coli for short.

B. coli is a ciliate, i.e., a member of the phylum Ciliophora, a group of protists that have their cells covered by cilia, which are nothing more than very short and numerous flagella. Most ciliates are free-living organisms, and in fact B. coli is the only ciliate known to be harmful to humans, but not only to humans. Many other mammals are also known to host this fellow, especially pigs.

balantidium_coli

The red elongate macronucleus of B. coli makes it look like a bad guy, don’t you think? Photo extracted from http://www.southampton.ac.uk/~ceb/Diagnosis/Vol2.htm

The typicall habitat of B. coli is the large intestine of mammals. The protist lives there in an active phase called trophozoite (seen in the image above) and feeds on the natural bacteria that live in the gut. When facing dehydration, which happens in the final portion of the intestine or after the organism is released with the feces, B. coli changes to an inactive phase called cyst, which is smaller than the trophozoite and covered by a thick wall. The cysts released in the environment may be ingested by a new host and reach their intestine, where they will return to the trophozoite form.

balantidium_coli2

A cyst of B.coli. Photo extracted from http://www.southampton.ac.uk/~ceb/Diagnosis/Vol2.htm

Symptoms of infection by B. coli, also known as balantidiasis, include explosive diarrhea every 20 minutes and, in acute infections, it may cause perforation of the colon and become a life-threatening condition.

Fortunately, infection in humans is not that common. The most affected country nowadays are the Philippines, but you may get infected anywhere. The best way to reduce the infection risks is by having good sanitary conditions and personal hygiene. However, as pigs are the most common vectors of the disease, it will likely continue to exist as long as humans raise pigs.

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ResearchBlogging.orgReferences:

Schuster, F., & Ramirez-Avila, L. (2008). Current World Status of Balantidium coli Clinical Microbiology Reviews, 21 (4), 626-638 DOI: 10.1128/CMR.00021-08

Wikipedia. Balantidium coli. Available at <https://en.wikipedia.org/wiki/Balantidium_coli&gt;. Access on February 23, 2017.

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Filed under Friday Fellow, Parasites, protists

Friday Fellow: Cute bee fly

ResearchBlogging.orgby Piter Kehoma Boll

Recently the appearance of a new pokémon, Cutiefly, has brought a lot of attention to the real world species in which it is based. So why not bring it to Friday Fellow so that you may know a little more about this creature? Its name is Anastoechus nitidulus, which I will call here “cute bee fly”, as most people find it very cute.

The cute bee fly is indeed very cute. Photo extracted from modernhorse.tumblr.com

The cute bee fly is indeed very cute. Photo extracted from modernhorse.tumblr.com

The cute bee fly belongs to the family of flies called Bombyliidae and commonly known as bee flies. The name comes from the fact that adults usually feed on nectar and polen, just like bees, and some of them are important pollinators.

Feeding. Photo extracted from reddit, posted by usar AnanasJonas.

Feeding. Photo extracted from reddit, posted by user AnanasJonas.

Unfortunately, just as many species, the cute bee fly may be very popular among laypeople and you find a lot of nice pictures of it on the web, just as the one above. However, scientifically, very little is known about its ecology.

Nevertheless, on thing is certain: despite its cuteness, it is not such a lovely creature. Its adult life flying from flower to flower hides a dark and evil past. During their period as larvae, bee flies are predators or parasitoids, meaning that they grow up by eating another animal alive, from inside out, in something that is certainly very horrible for the poor victim.

In the case of the cute bee fly, things are not that terrible. They feed on the egg-pods of grasshoppers, especially of the genus Calliptamus, so we can say that they are parasitoids of eggs instead of adults, but then you realize that eggs have embryos, so they are actually baby-eaters!

O_O

O_O

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References:

Brooks, A. (2012). Identification of Bombyliid Parasites and Hyperparasites of Phalaenidae of the Prairie Provinces of Canada, with Descriptions of Six Other Bombyliid Pupae (Diptera) The Canadian Entomologist, 84 (12), 357-373 DOI: 10.4039/Ent84357-12

Jazykov (Zakhvatkin), A. (2009). Parasites and Hyperparasites of the Egg-pods of injurious Locusts (Acridodea) of Turkestan Bulletin of Entomological Research, 22 (03) DOI: 10.1017/S0007485300029904

Wikipedia. Bombyliidae. Available at < https://en.wikipedia.org/wiki/Bombyliidae >. Access on July 26, 2016.

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Filed under Entomology, Friday Fellow, Parasites, Zoology

Friday Fellow: Heartworm

by Piter Kehoma Boll

Life is not composed only by beautiful and cute creatures. Parasites form a big part of life. In fact, it is likely that there are more parasitic species than non-parasitic ones.

The heartworm (Dirofilaria immitis) is one of these not-so-cute species. A species of roundworm, it infects small mammals, especially dogs, and is spread by mosquitoes.

The name heartworm comes from the fact that this worm lives in the heart and pulmonary arteries of dogs during its adult stage. The result of the infection may be heart failure and damage on the heart and the arteries, but some infections may pass completely unnoticed, especially in sedentary dogs.

Not a pleasant view. Heartworms in a dog's heart. Photo by Alan R Walker*.

Not a pleasant view. Heartworms in a dog’s heart. Photo by Alan R Walker*.

After males and females mate in the heart of the dog, females give birth to live larvae called microfilariae. These are released in the bloodstream and await for being transfered to a bloodsucking mosquito during a bite. Over 60 species of mosquitoes are known to serve as intermediate hosts of microfilariae.

Inside the mosquito, the microfilariae grow from the larval stage L1 to the larval stage L3 and then migrate to the mosquito’s salivary glands and, once it bites another dog, they are transferred to it and develop under the skin at the site of the bite to the stage L4. Now the L4 larve migrate to the dog’s muscles and develop into the stage L5. Finally, they start to migrate through the bloodstream until they reach the heart and the pulmonary artery, where they mold into adults and the cycle is complete.

We may find such worms disgusting, but we must admit that they have a complex and amazing life.

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References:

Wikimedia. Dirofilaria immitis. Available at: < https://en.wikipedia.org/wiki/Dirofilaria_immitis >. Access on June 7, 2012.

Ludlam, K. W.; Jachowski, L. A.; Otto, G. G. 1970. Potential vectors of Dirofilaria imiitis. Journal of the American Veterinary Medical Association, 157: 1354-1359.

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*Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

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Filed under Friday Fellow, Parasites, worms