Chronic Wasting Disease: A New Threat To Pennsylvania Deer, No Gun Required

Dinner. Unless he has CWD. Source, Wikimedia Commons, (C) USDA, Agricultural Research Service

This post was originally published at Mind the Science Gap on Nov. 29, 2012.

In early October a deer tested positive for Chronic Wasting Disease for the first time in Pennsylvania. The positive result, which was found in a farm herd, resulted in the quarantine of all the deer on the property. Earlier this month, a deer escaped the quarantine and was running free in Pennsylvania. Two days ago that deer was shot and killed to prevent further disease transmission. That doe is still undergoing testing to determine if she was infected. As a result of all of these events unfolding, Pennsylvania has swiftly put plans into action. Chronic Wasting Disease (CWD) is nearly impossible to eradicate once it establishes itself in a population, and in order to save PA’s deer herds, they needed to act fast.

Chronic Wasting Disease is endemic (established in wild populations) in Colorado and Wyoming. It has also been reported in wild herds in Illinois, Kansas, Maryland, Minnesota, Missouri, Nebraska, New Mexico, New York, North Dakota, South Dakota, Texas, Utah, Virginia, West Virginia, and Wisconsin. CWD has been found in captive herds in other states, such as Iowa. States with no confirmed cases often have CWD task forces and policies to prevent introduction of the pathogen. For example, Washington recently began requiring hunters returning from CWD-endemic areas to undergo testing and processing to remove infectious material.

CWD is a type of transmissible spongiform encephalopathy (TSE), a group of disease that includes Bovine Spongiform Encephalopathy (Mad Cow), Scrapie (a disease commonly found in sheep), Creutzfeldt-Jacob disease (a neurodegenerative disease in humans), and Fatal familial insomnia (a disease where protein misfolding results in insomnia which progresses to delusions and eventually death). TSEs are all caused by a pathogenic organism known as a prion. Prions are rather unique in that they are not a virus or bacteria, but a protein with an abnormal structure. These prions can be infectious and transmissible (like CWD and Mad Cow) or inherited (like the fatal insomnia). Continue reading

Eastern Equine Encephalitis: The Mosquito that bit the Snake

A Copperhead. (C) Greg Hul, Flickr Creative Commons

This post was originally published at Mind the Science Gap on Oct. 11, 2012. This post was also cross-posted at Aetiology on Oct. 17, 2012.

Last week a new study regarding Eastern Equine Encephalitis (EEE) was published online (Bingham et.al.). EEE is a mosquito-borne virus that can cause serious, and sometimes deadly, disease in humans and equines. In warmer parts of North America, the virus is spread year-round, but in areas where mosquitoes get killed off in the winter it has been something of a mystery as to how the virus makes it from year to year. Humans and equines are both dead-end hosts, which means that a mosquito can not be infected from biting an infected person or horse. Researchers in Alabama found that wild snakes in the Tuskegee National Forest were positive for  Eastern Equine Encephalitis virus (EEEV), which could explain how EEE was maintained after the first frosts killed off infected mosquitoes. Essentially, what would happen is that an infected mosquito bites a snake, probably during the summer or early fall, and the snake harbors the virus in its blood during the winter. Then, in the spring, an uninfected mosquito (which overwinters as a larva) bites the snake and acquires the virus. This now-infected mosquito can bite a horse or a human, who can then get sick. (I’m sensing a Chad Gadya theme here. Just me? Ok…) Continue reading