Tag Archives: epidemics

Friday Fellow: Amphibian chytrid fungus

by Piter Kehoma Boll

Today I’m bringing you a species that is probably one of the most terrible ones to exist today, the amphibian chytrid fungus, Batrachochytrium dendrobatidis, also known simply as Bd.


Several sporangia of Batrachochytrium dendrobatidis (spherical structures) growing on a freshwater arthropod. Photo by AJ Cann.*

The amphibian chytrid fungus, as its name says, is a chytrid, a fungus of the division Chytridiomycota, which include microscopic species that usually feed by degrading chitin, keratin in other such materials. In the case of the amphibian chytrid fungus, it infects the skin of amphibians and feeds on it. It grows through the skin forming a network of rhizoids that originate spherical sporangia that contains spores.

The infection caused by the amphibian chytrid fungus is called chytridiomycosis. It causes a series of symptoms, including reddening of the skin, lethargy, convlusions, anorexia and excessive thickening and shedding of the skin. This thickening of the skin leads to problems in taking in nutrients, releasing toxins and even breathing, eventually leading to death.


An individual of the species Atelopus limosus infected by the amphibian chytrid fungus. Photo by Brian Gratwicke.**

Since its discovery and naming in 1998, the amphibian chytrid fungus has devastated the populations of many amphibian species throughout the world. Some species, such as the golden toad and the Rabb’s fringe-limbed treefrog, were recently extinct by this terrible fungus. This whole drastic scenario is already considered one of the most severe examples of Holocene extinction. The reason for such a sudden increase in the infections is unknown, but it may be related to human impact on the environment.

We can only hope to find a way to reduce the spread of this nightmare to biodiversity.

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Fisher, M., Garner, T., & Walker, S. (2009). Global Emergence of Batrachochytrium dendrobatidis and Amphibian Chytridiomycosis in Space, Time, and Host Annual Review of Microbiology, 63 (1), 291-310 DOI: 10.1146/annurev.micro.091208.073435

Wikipedia. Batrachochytridium dendrobatidis. Available at <https://en.wikipedia.org/wiki/Batrachochytrium_dendrobatidis&gt;. Access on March 4, 2017.

Wikipedia. Chytridiomycosis. Available at <https://en.wikipedia.org/wiki/Chytridiomycosis&gt;. Access on March 4, 2017.

Wikipedia. Decline in amphibian populations. Available at <https://en.wikipedia.org/wiki/Decline_in_amphibian_populations&gt;. Access on March 4, 2017.

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*Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 2.0 Generic License.

**Creative Commons License
This work is licensed under a Creative Commons Attribution 2.0 Generic License.


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Filed under Disease, Extinction, Friday Fellow, Fungi

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.


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.


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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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

Zika virus and the negligence towards health research in poor countries

ResearchBlogging.org by Piter Kehoma Boll

About a year ago, almost nobody on the whole world was aware of the existence of a virus named Zika virus and the illness it may cause in humans, the Zika fever or Zika disease. But is this a new, previously unknown virus? Where did it come from and why is it suddenly of so much concern?

The Zika virus, or ZIKV, is a virus in the genus Flavivirus, which also include other viruses, such as the ones responsible for the dengue fever and the yellow fever. The name Flavivirus means “yellow virus” in Latin, due to the yellow fever. All the three diseases are transmitted to humans throughs mosquitoes, especially the widespread Aedes aegypti.

The mosquito Aedes aegypti is currently the main vector of the Zika virus. Photo by James Gathany.

The mosquito Aedes aegypti is currently the main vector of the Zika virus. Photo by James Gathany.

The Zika virus was discovered in 1947 in Uganda in a febrile rhesus monkey in the Zika Forest, hence the name. From 1951 on, serological studies indicated that the virus could also infect humans, as antibodies against the virus were found in the blood of humans in several African and Asian countries, such as Central African Republic, Egypt, Gabon, Sierra Leone, Tanzania, Uganda, India, Indonesia, Malaysia, the Philippines, Thailand and Vietnam.

In 1968, in Nigeria, the virus was isolated from humans for the first time. During the following decades of the 20th century, the virus was detected via serological evidence or isolated directly in many humans. However, despite the confirmation of this virus in humans, research developed very slowly, most likely because the affected countries don’t have enough resources to conduct the necessary studies and richer countries are not at all interested in the health of the poor ones.

There was a small increase in concern over the virus after it was detected outside Africa and Asia for the first time, in 2007, in the Yap Island, Micronesia. After that, some epidemics occurred in several archipelagoes in the Pacific.

Since last year, the Zika virus has been dectected in South America and started to spread rapidly across the countries. It was suggested that the virus reached Brazil in 2014 during the World Cup. (Thanks, FIFA!). By November 2015, the disease has reached Mexico, which means it is about to reach the United States! Now suddenly it started to be of a major concern worlwide.

Currently known distribution of the Zika virus in humans. Map of the United States Centers for Disease Control and Prevention.

Currently known distribution of the Zika virus in humans. Map of the United States Centers for Disease Control and Prevention.

Common symptoms of the Zika fever include mild headaches, fever, joint pains and rash. It was not considered a serious disease, as it usually fades quickly after a week, until recently, when it was linked to the development of microcephaly in fetuses of mothers infected by the virus during the first trimester of pregnancy.

I wonder how many children were born with microcephaly in Africa and Asia during the last decades because there was no investment to study the virus. Now that it suddenly became a worldwide threat, there is no vaccine, no adequate treatment and most physicians are unable to identify the illness through the symptoms.

And there are a lot of other viruses forgotten in poor tropical countries just waiting for the right opportunity to spread and scare North America and Europe. No one cares while they remain among poor African and Asian people, but global warming is here and tropical diseases love it more than anything else.

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Gatherer, D. & Kohl, A., (2015). Zika virus: a previously slow pandemic spreads rapidly through the Americas Journal of General Virology DOI: 10.1099/jgv.0.000381

Hayes, E. B. 2009. Zika Virus Outside Africa. Emerging Infectious Diseases, 15(9): 1347-1350.

Vasconcelos, P. (2015). Doença pelo vírus Zika: um novo problema emergente nas Américas? Revista Pan-Amazônica de Saúde, 6 (2), 9-10 DOI: 10.5123/S2176-62232015000200001

Wikipedia. Zika virus. Available at: <https://en.wikipedia.org/wiki/Zika_virus&gt;. Access on January 25, 2016.



Filed under Conservation, Disease, Virus