disease.com – Disease

Ebola

With the distant memory of mad-cow disease now in the proverbial rear view mirror of people worldwide, the recent outbreak of swine flu, or H1N1, has caused a significant panic.  To people all over the world, swine flu is just another example of a number of deadly infectious diseases that have hopped species, whether from animal to human or human to animal.

Pathogens such as bacteria and viruses that cause infectious disease are quickly evolving and adapting entities, causing medicine to constantly update to keep up with the evolutionary changes of such pathogens.  Pathogens that usually cause disease in an animal can quickly evolve and infect another species.  These diseases have been noted throughout history to make a big impact on all of the species involved.

This sort of cross-species disease can originate from farms or markets, where infection can quickly spread between species, evolving their genes to develop the ability to infect humans.  These types of diseases are called zoonoses, or zoonotic diseases.  There are dozens of zoonotic diseases that humans can catch through the touching of animals, and dozens more of these diseases are transferable through bites.

The rest of this article will focus on 5 diseases that evolved into multi-species diseases:

1.  Crabs

Gorillas are the culprits of pubic lice in humans.  In 2007, scientists concluded that humans contracted pub lice, or crabs, from gorillas about 3 million years ago.  It is important to mention that humans did not sleep with gorillas, but instead, ate the gorillas and slept in their nests.  Humans are unique in that we are hosts for two types of lice, head lice and pubic lice.  Chimpanzees host head lice, while gorillas host pubic lice.

2.  Polio, Syphilis, and Anthrax

Originally a human disease, scientists have speculated that polio was transferred from humans to chimps.  Reports also show that gorillas may have contracted a disease similar to syphilis, but is not sexually transmitted from humans.  Both chimps and gorillas in West Africa were killed by anthrax, possibly fro cattle herded by humans.

3.  Ebola

Ebola is a deadly disease transmitted to humans through the ingestion of infected animals.  It is now transferable between humans through blood or bodily fluids, and can kill up to 90% of people infected with it.  Symptoms include sudden fever, intense weakness, vomiting, diarrhea, impaired bodily functions, and death.  It may be carried in bats as well, as they do not die when they contract the disease.

4.  Toxoplasma gondii

Contracted from cats, the parasite Toxoplasma gondii is estimated to infect more than half of the human population.  It is speculated that the disease increases the risk of neuroticism and schizophrenia.  The microbe reproduces sexually in house cats, making the human owners prove to pick it up.  The disease never goes away, and usually only hosts flu-like symptoms.  One study found that countries with high levels of Toxoplasma gondii infection have high neuroticism scores.

5.  The Flu

Influenza has been the ultimate example of cross-species diseases throughout history.  While swine flu outbreaks have caused a few deaths in the past year, it is nothing compared to what the flu has done throughout history.  In 1918, a flu pandemic killed 50 million people.  During the year of the pandemic, the average life expectancy dropped 12 years in the United States.