Crossing The Species Barrier
Crossing the Species Barrier
The “species barrier” is defined as an imaginary barrier that prevents diseases in one species from infecting other species. The barrier has been thought to prevent the transmission of bacteria from livestock to humans, but recently researchers found
alarming evidence that in some cases diseases from different organisms may infect other
species, including humans. The majority of these infectious agents are "zoonotic", meaning that their usual host is a nonhuman vertebrate. Humans come into contact with these zoonotic diseases thru contact with animals. This phenomena has been increasing more and more in recent years and most researchers feel that its is due to an increase in urbanization worldwide, encroachment on previously uninhabited forest and desert land and a mobile human population traversing oceans at jet speed provide ample opportunities for diseases to emerge - or re-emerge, occasionally in more virulent forms - just about anywhere.2
One example of a species crossing disease is mad cow disease, bovine spongiform encephalopathy (BSE). BSE is a progressive neurological disorder in cattle, which is believed to have caused a fatal brain disease known as variant Creutzfeldt-Jakob disease (vCJD) in humans. The infectious agent linked to both BSE and vCJD is unknown -- current theories point towards a mutation in certain protein molecules known as prions. An outbreak of BSE in Great Britain in the 1990s appears to have been caused by the consumption of animal feed contaminated by infected sheep and/or cattle meat and bone meal.
The new variant of CJD has an incubation period of several years before symptoms emerge. It tends to affect younger people -- as of October 2000, the median age of death was 27.5 years. The first symptoms include serious psychological or sensory problems, followed by poor muscle coordination and mental confusion. The illness lasts for at least six months, with...
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