Friday, February 14, 2014
Pathogenicity and Virulence
A Reoccurring Concern
Spanish Flu, Bird Flu, Pig Flu, Ebola(diseases). Every so often it seems as if a new disease is going to be the next pandemic, with the exception of the Spanish flu that proved to be a pandemic. Somehow many of us survive to face the next one. Conspiracy theorists say the government is behind it. Though there is possibility that they are right, the correct answer lies within a deeper understanding of how pathogens function. The pathogen’s ability to infect and the magnitude of the infection play a significant role in its success. When a pathogen finds the perfect balance, it will be very successful.
A pathogen is defined as a microorganism that causes disease. The pathogen has two important characteristics. The first is pathogenic character, which is defined as the pathogen’s ability to cause disease in its host. The second characteristic is virulence, which is defined as the magnitude at which the disease occurs. Pathogenicity is a quality that is either on or off. The virulence factor measures the level of pathogenicity. There are multiple virulence factors, such as attachment, destructive enzymes and toxins. Virulence factors allow for the pathogen to be more successful within a limit. To explain, if a pathogen has zero virulence then it is no longer actually a pathogen by definition because it is not causing disease. On the other hand, if the virulence factors are too high then the pathogen will be so efficient at killing its host that it may deplete its reservoir, the host it infects, and no longer reproduce.
Chestnuts No More
Chestnut trees(host) were one of the most utilized trees in
It was used for the durability of its bark and the tastiness of its chestnuts.
However, this only lasted up until the 1900.This is when the Chestnut blight took
place. A fungus, Cryphonectria parasitica that originated in China and only infected dying twigs and pieces of bark, was introduced to America around 1893. In the fungus' native region there existed a different kind of chestnut tree which was resistant to the fungus. Once introduced t the American chestnut tree it only took 40 years to wipe out all the chestnut trees in America. Cryphonectria parasitica spread up to 50 miles of chestnut forestry a year. Once the chestnut trees were decimated the fungus' reproduction rate plummeted, without a host to provide the nutrients and a habitat it's reproduction was halted. 
No Need to worry
The perfect balance the pathogen seeks to find can only be successful if they successfully infect their host. If the pathogen is successful in reaching a balance, there is a multitude of ways that interaction with a pathogen can be avoided. If interaction still occurs your body has mechanisms that are in place to deal with the pathogen. If the mechanisms fail the human population is a genetically diverse species and a resistant human can exist and survive. The host and pathogen have an eternal struggle that is an evolutionary arms race. The victory has yet to be decided.
Posted by nicholas reynolds at 10:19:00 AM