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Extinction by Design: Rinderpest

The views expressed are those of the author and are not necessarily those of Scientific American.


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Blogger’s note: I am going to be out of blog contact for the next several weeks as I get hitched (yay!), honeymoon (double yay!), and move (goodbye Colorado! Very sad to leave). In the meantime, I will be bringing you some classic Artful Amoeba.

This post originally appeared on January 13, 2010. Since I wrote this blog post back in 2010, rinderpest was indeed eradicated. On August 8, 2011, the UN declared rinderpest officially eliminated from the world, making it only the second disease in history after smallpox to vanish at our hands.

Extinction has a flip side: eradication. We did it to smallpox (or rather, almost did it; a few samples survive in U.S. and Russian labs), and though the ethics of that are interesting to think about as an intellectual exercise, there is no question that it has relieved the suffering of millions. Scientists are on the verge of doing it again with two organisms: another virus and an infamous parasitic worm. The obliteration of either one would mark only the second time this has happened in human history, and the first in 30 years.

Rinderpest is a vicious livestock virus that has sickened hundreds of millions of cattle in Eurasia and Africa since ancient times. In herds that have never encountered the disease, it can fell nearly every animal, and it’s not a pretty death: weeping mouth and urogenital ulcers, constipation followed by diarrhea, and a struggle to breathe. Though the virus affects only cattle and related wild animals like wildebeest and giraffes, when millions of cattle die, their keepers starve.

The rinderpest virus, a paramyxovirus in the “genus” Morbillivirus, seems to be related to the measles, mumps, and canine distemper viruses. Rinderpest is an RNA virus, which means it uses the material we normally use to translate DNA into proteins as its hereditary material. For the bio geeks out there, it’s a negative-sense virus, which means the genome has to be translated into the positive sense by an RNA polymerase conveniently packed into the virion. The positive sense strand then acts as mRNA and can make all the virus’s hijacking, lockpicking, and get-out-of-cell-free proteins. When the virus is done replicating, new negative-sense RNA and a sampler of the appropriate proteins are then enveloped by a membrane spiked with fusion and attachment proteins that help the virus get into cells.

Every paramyxovirus has  but a single strand of RNA, on which a mere 6-10 genes lie. In Morbilliviruses, there are exactly three nucleotides (A(denine)s, G(uanine)s, C(ytosine)s, or U(racil)s) between each gene, which is incredibly efficient packaging for those of us familiar with the thousands and millions of non-coding nucleotide bases between genes in be-celled life. The order of the genes is conserved too because the virus practices “transcriptional polarity”, a phenomenon in which genes closest to the “beginning” of the RNA strand are transcribed more often than the ones at the end. That’s probably because the protein that translates the strand — the RNA polymerase — has a tendency to fall off before it’s finished. This provides cheap and easy transcription regulation, but also a strong incentive not to shuffle your genes. What I’ve told you so far applies to Morbilliviruses and Paramyxoviruses in general, but other than its mug shot, above, I can’t find out much more online about Rinderpest’s particular modus operandi.

Strangely, in spite of its prowess, the virus never succeeded in reaching the Americas. And in spite of a reliable vaccine and the near elimination of the virus from Africa in the 1970s, we didn’t finish the job, and tens of millions of livestock were dying again in the early 1980s. Finally, in 1993 the UN Food and Agriculture Organization had enough and decided it was time to bring it to the virus. 17 years later, the end game is at hand. You can read more about the history of the virus and eradication effort and how close we are here (subscription required) and here to only the second intentional extinction on Earth.

Next time: Reason # 1,356 to be thankful for your local water treatment plant: Guinea Worm.

 

Jennifer Frazer About the Author: Jennifer Frazer is a AAAS Science Journalism Award-winning science writer. She has degrees in biology, plant pathology/mycology, and science writing, and has spent many happy hours studying life in situ. Follow on Twitter @JenniferFrazer.

The views expressed are those of the author and are not necessarily those of Scientific American.





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