Published: January 14, 2014
Author: Geoffrey Mohan
http://www.latimes.com/science/sciencenow/la-sci-sn-lice-primates-genome-20140107,0,4712848.story#axzz2q7FuTgKM
Summary:
When humans diverged from chimpanzees, the lice on the two species became relatively isolated from each other. Recently, it was discovered that the lice on humans evolved 14 times faster than the lice that lives on chimpanzees. Geneticists studied the DNA of the lice and found that there were roughly 1,500 substitutions in the DNA. Most of the substitutions were silent mutations. They concluded that the faster the host's DNA evolved, the faster the lice's DNA evolved. Julie Allen, an author of the paper, made a second conclusion that there are common "selective pressures" on certain genes in the lice, humans, and primate species. Lice evolve rapidly because they don't live very long, which explains why they can undergo many evolutionary changes in a short amount of time.
Connection:
This article about lice includes two different units we have studied this term. The article tells how the there was a divergence between the human and chimpanzee species. The lice on humans had become isolated from the lice on chimpanzees, therefore causing the lice to evolve at different paces. The lice that live off of chimpanzees are not a separate species than the lice that live on humans because they still fill similar niches. We talked about the concept of divergence, convergence, and isolation in class many times in class notes. This article also connects to our molecular genetics unit. It mentioned that many base pairs of the lice's DNA were mutated by substitutions. We learned earlier in the term about different kinds of mutations and how they can cause totally different amino acids to be synthesized.
Scientists are currently researching to find antibiotics that would lead to the death of lice, and currently have an antibiotic that is not yet confirmed if it fully does its job. Would there be any use to finding an antibiotic to kill the lice if they evolve so fast? Would antibiotics be a long term possibility for killing head lice in humans, or would it be short term due to their ability to evolve so fast? If the antibiotics are supposed to kill bacteria inside the lice and lead to their death, would the antibiotics still be effective?
ReplyDeleteThere are three types of lice that live on humans (head lice, body lice and crab lice) the most common being head lice. On humans, head lice lay about 10 eggs a day. To treat the lice, pharmacies do have over the counter products to kill the eggs and the lice that excessively stimulating the nervous systems of the lice and the eggs. This is the most common way to get rid of head lice. But sometimes the medication does not successfully kill all the lice. There are several medications where resistance has been reported but only in certain countries. If this is the case, the person with lice can get a prescription. Because most of the time the over the counter medication works, the prescription medication works. Also some medications lubricate the subjects already-wet hair to make it easy to comb out the lice and the eggs. The lice die after about two days without a host. So, to answer your question directly, it is worth scientists time to find an antibiotic because it would be used as a last resort to solve the problem of lice infestations. The antibiotic you are talking about is a combination of trimethoprim and sulfamethoxazole. This antibiotic works by killing bacteria in the lice's gut which leads to their death almost instantly. The downside is this antibiotic is that it is still being tested in small trials and is potentially neurotoxic. It has only been approved in Canada. The question has been raised whether or not it should be approved in the US and other countries because of the possibility of bacterial resistance if widely used. If the antibiotic is approved, it is likely it would be very hard to get due to the potential risks of using it. Therefore I think that the antibiotic would be a longer term solution.
Deletehttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC1070891/ http://www.licemd.com/pediculicide-lice-treatment.php http://www.cps.ca/documents/position/head-lice