Chronic Wasting Disease

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White tailed deer

Chronic Wasting Disease (CWD) is a neurological disease caused by a prion found in cervids. The prion is a transmissible spongiform encephalopathy (TSE) that is similar to bovine spongiform encephalopathy (BSE), or “mad cow disease,” in bovines. The disease is thought to be non-zoonotic, but it is still advised that people not consume infected venison. It is also not thought to have an effect on livestock. The disease was first found in captive populations in the 1970’s, with later speculations about wild origins going back more than 40 years prior. Little is known about this disease, how it is transmitted and its impact on animal populations, so research is being conducted to attempt to answer these questions. CWD is more common in adults but is not isolated from yearlings; it is a progressive disease and is always fatal.

Mechanism

Little is known about transmission, but it is thought to be contagious through direct contact between animals or possibly through contaminated water or feed sources. However, once infected, the prion works on the central nervous system to convert normal cellular proteins into abnormal proteins. Because of its small size, it does not instigate any inflammatory responses from the immune system like other infections normally would. This means the disease is undetectable by the immune system, making it especially hard to know if an animal is infected during early onset. The long incubation time of at least 16 months causes further uncertainty.

Symptoms

  • Long-term weight loss due to gradual disinterest in food
  • Excessive drinking and urinating (late stages)
  • Decreases sociability
  • Lethargy/listlessness
  • Lowered head and blank look
  • Repetitive walking in patterns
  • Over-excitability and nervousness (elk)
  • Brain, lymphoid and tonsillar lesions (once deceased and necropsied)
  • Aspiration pneumonia (not confirmed but a common associated disease; might be the actual cause of death)

Range

CWD is currently endemic to northeastern Colorado and southeastern Wyoming. It has been found in a few states east of the Mississippi River, but is concentrated primarily in the central and midwestern U.S. In total, CWD has been recorded in 21 U.S states and 2 Canadian providences. The range is expected to grow.

cwd_map

CWD range in North America

Species of Concern

Cervids, a group of unguilligates (hoofed animals), consist of species of deer, moose and elk. Species of concern for CWD in the U.S include:

  • White-tailed deer: Most of the country and southern Canada, excluded in very southwestern states in the U.S
  • Mule deer: Western North America
  • Elk: Primarily in western North America
  • Moose: Northwestern U.S and almost all of Canada

Significance

There is no known cure or clinical test in living cervids for CWD. Although CWD is not thought to be transmissible to humans through meat handling or consumption, it is still recommended that infected meat not be consumed. Little understanding of the prion makes long-term effects of CWD and how it will effect population management, hunting and environmental management are unknown. Uncertainty in diseases, especially one as fatal and undetectable as CWD, present extreme risk for population, environmental and, possibly, human health. Hunting is also a source of revenue for state governments, and cervids are America’s most popular game species. Effects on population would have effects on hunting quotas, licensing and ultimately state economies. More research is being conducted to better understand this disease, however it is not know what damage may have already been done.

Sources

CDC. (2015, February 06). Chronic Wasting Disease (CWD). Retrieved April 21, 2017, from https://www.cdc.gov/prions/cwd/index.html

Chronic Wasting Disease Alliance. (n.d.). Chronic Wasting Disease FAQ. Retrieved April 21, 2017, from http://cwd-info.org/faq/

NWHC. (2016, May 19). Chronic Wasting Disease (CWD). Retrieved April 21, 2017, from https://www.nwhc.usgs.gov/disease_information/chronic_wasting_disease/

Hantavirus

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Deer mouse

Hantavirus is a virus that infects rodents. Although the disease lies dormant in the rodent host, it can infect humans, leading to a disease called Hantavirus Pulmonary Syndrome (HPS) or Hemorrhagic Fever with Renal Syndrome (HFRS). HFRS has not been seen in the U.S, but HPS is very common as a result to Hantavirus exposure and can be fatal. The strain of Hantavirus that causes the majority of HPS infections is called Sin Nombre virus. This virus is not contagious in the U.S, but is easily contracted.

Transmission

Hantavirus is spread though rodent urine, feces and saliva. Most often, it is contracted as an airborne infection when a person breathes in contaminated air. There are other methods of transmission. The first is through a bite from the infected rodent, although this is not common. The second is believed but not 100% confirmed by researchers: touching a contaminated surface and then touching one’s nose or mouth. The third is also speculated: eating food that has been contaminated. After infection, the virus then causes lung congestion and fluid accumulation that can lead to death in about 38% of people.

hantaviruses

Symptoms

Before HPS onset, minor illness from a Hantavirus may begin 5 to 42 days after infection and may include:

  • Fever/chills
  • Fatigue
  • Head, abdominal and muscle aches
  • Dizziness
  • Nausea/vomiting/diarrhea

More serious symptoms indicating HPS may arrive after 10 days of initial illness and may include:

  • Coughing
  • Shortness of breath
  • Difficulty breathing (from fluid accumulation in the lungs)

Range

Although Hantaviruses have been recorded across the world (the first being discovered in Korea) the only Hantaviruses found in the U.S are not contagious and only cause minor infections to HPS, not HFRS. As of 2016, 690 cases of HPS have been recorded, 659 of which from 1993 onward. The majority of cases reported occur in states west of the Mississippi River.

HPS_US_ByStateOfExposure

Species of Concern

  • Deer mouse: throughout nearly all of America; primarily woodlands
  • Cotton rat: southeastern, central and southern America; shrublands and tall grasslands
  • Rice rat: southeastern and southcentral America; marshy/wetland areas
  • White-footed mouse: north and mideastern, central and southwestern America; wooded and brushy areas

Prevention

The best way to avoid Hantavirus infection is to avoid close contact with rodents and deny them access to buildings. Keeping all food products stored in tight containers with sturdy garbage containers, mowing tall grasses, placing all gardens or other shelter areas away from the building, and sealing the building are all effective ways to avoid rodent infestation. If an infestation has occurred, several options are possible to safely exterminate the rodents. First, be sure that all of the proper preventative measures are followed. Then, a professional exterminator can be called or one can manage the problem themselves using snap traps, rodenticide that is environmentally safe and used according to specific directions and disinfecting contaminated surfaces with diluted bleach or phenol-containing disinfectants (i.e Lysol). Do not sweep or vacuum before disinfecting so the virus is not allowed to go airborne. Wear rubber gloves and a mask/respirator while managing the contamination to avoid infection.

Significance

Contracting HPS may be relatively uncommon, but a mild infection of Hantaviruses are fairly easy to contract. This virus is found internationally and is widespread throughout the U.S. While the likelihood of the disease developing into HPS is low, 38% of people with HPS die. There is no vaccine for the Hantavirus, making an easily contracted contaminant that could result in severe sickness or fatality. A species like the deer mouse has incredible range over the whole of the U.S and into Mexico and other species of host rodents could become invasive in the U.S. This means there is a small but existing chance of contagious versions of HPS or even HFRS becoming a new threat to the U.S. Awareness and proper management of rodent infestations can help one avoid a Hantavirus infection and prevent spreading.

Sources

IDPH. (n.d.). Hantaviruses. Retrieved April 21, 2017, from http://www.dph.illinois.gov/topics-services/diseases-and-conditions/diseases-a-z-list/hantavirus

CDC. (2017, April 06). Hantavirus. Retrieved April 21, 2017, from https://www.cdc.gov/hantavirus/index.html

Davis, C. P., MD. (2015, October 22). Hantavirus Symptoms, History, Transmission & Treatment (M. C. Stoppler MD, Ed.). Retrieved April 21, 2017, from http://www.medicinenet.com/hantavirus_pulmonary_syndrome/article.htm

Histoplasmosis

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American crow

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. This fungus grows primarily in soil that has been contaminated with bat or bird droppings. Typically, H. capsulatum is most viable in areas with large concentrations of feces and often does not result in an infection. However, this disease has become endemic to some regions of the U.S and is zoonotic, meaning it can transfer from animals to humans. Infections can be mild to severe chronic conditions depending on several factors including the number of spores inhaled and individual immune capacities. While this disease is mediated by animals, it is not contagious or zoonotic (transferrable from animals to humans). This is not to say that animals cannot become infected by histoplasmosis, but that it cannot spread once contracted like WNS or SFD can.

Mechanism of Action

H. capsulatum spores are released into the air once contaminated soil is disturbed. In a  person with a compromised immune system or an area with high concentrations of spores, an infection is likely to occur from inhalation of disturbed spores. Although infections are typically acute, there are chances of systemic spread to other parts of the body. This occurs after the spores in the lungs are allowed to form into yeast. The yeast would then travel into the lymph nodes and then to the bloodstream. The blood could then carry the infection to other organs of the body.

Species of Concern

  • American crows
  • Rock pigeons
  • European starlings
  • Gregarious bats (big brown, tricolored, etc.)
  • Flocking birds

Symptoms

Symptoms can appear between 3 and 17 days after first inhalation of spores. Most acute cases may result in:

  • Mild fever/chills
  • Cough
  • Chest/joint/body pain
  • Red bumps on lower legs
  • Fatigue

More severe cases may result in:

  • Excessive sweating
  • Shortness of breath
  • Coughing blood
  • Serious chest pain
  • High fever
  • Stiff neck and headaches

Range

H. capsulatum can be found anywhere in the world, but is most common in North and Central America, with particularly high concentrations in southeastern and central U.S. The Ohio and Mississippi River Valleys are the areas of highest concern.

histoplasmosis-lifecycle-maps-300px

Prevention

Those with known suppressed immune systems should avoid doing activities cohesive with histoplasmosis infection. Some activities include disturbing soil with droppings on it, cleaning chicken coops, exploring caves, construction or remodeling houses. Some occupations may be high risk such as construction, farming, pest control, demolition, roofer or landscaper. A respirator should be used when working in situations where infection is likely to occur.

Significance

Although histoplasmosis often does not result in serious infection, there are still locations in America where histoplasmosis is highly endemic. It can infect pets as well as humans and can be very problematic for those with weakened immune systems. Many people are at risk of infection, even in urban areas where flocking birds like pigeons and crows are highly common. Although breathing in spores often does not result in symptomatic infection, there are still easily avoided risks surrounding this disease. Histoplasmosis is opportunistic and may infect up to 30% of HIV/AIDS patients, resulting in more serious, systemic infections. Small children and seniors may also have high risk of infection and are at a greater risk for serious infection.

Sources

Delgado, A. (2016, January 19). Histoplasmosis (D. Weatherspoon Ph.D, Ed.). Retrieved April 20, 2017, from http://www.healthline.com/health/histoplasmosis#risk-factors5

CDC. (2015, November 21). Fungal Diseases. Retrieved April 20, 2017, from https://www.cdc.gov/fungal/diseases/histoplasmosis/index.html

Kauffman, C. A. (2007). Histoplasmosis: a Clinical and Laboratory Update. Clinical Microbiology Reviews, 20(1), 115-132. Retrieved April 20, 2017, from http://cmr.asm.org/content/20/1/115.short

White Nose Syndrome

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Gregarious bat with WNS

White Nose Syndrome (WNS) is a fungal infection identified by its characteristic white appearance on the noses of aggregating bat species. The fungus that causes WNS is called Pseudogymnoascus destructans, or Pd. It thrives in cold environments, which aligns perfectly with bat hibernation times and locations. Gregarious bats will hibernate communally in a dark and typically moist environment to wait out the cold winter. However, this is a great breeding ground for Pd. Many bats in close proximity to large amounts of infectious fungus allows the disease to spread rapidly and infect an entire colony over the winter. Large strains have already been placed on bat populations, from wind turbines to habitat destruction to other diseases, such as rabies. WNS only adds to the decimation of bat populations across almost half of the country.

Transmission

In the wild, the mode of transmission begins with fungal spores attaching to the nose or other bare areas on the bat, such as the wings. Because hibernating bats are in close proximity to each other, even if the spores fail to infect one individual, it is very easily spread from one infected individual to another. Nose to nose contact is typical in gregarious bats and permits easy transmission throughout an entire colony.

Symptoms

The main symptoms of WNS are:

  • Characteristic white nose from fungal growth
  • Fungal growth on the tail, ears and wings
  • More frequent arousal and arousal at abnormal times/temperatures (during the day at below/near freezing temperatures)
  • Clustering near the opening of their hibernation cavity
  • Emaciation
  • Wrinkled skin/dehydration

Range

WNS was first documented and confirmed in 2007 and has since spread westward across nearly half of the country. It began in northeastern America, but has since spread to the midwest, and has even been recorded in Washington. Recently, WNS has been spreading southward with its first documented case being discovered in Oklahoma just this year.

wnsspreadmap_4_17_2017

Range map of WNS documentation by year

Significance

Although there are no known dangers of infection from bat to person, scientists feel more research must be done to more fully understand the disease and associated bat populations. WNS typically results in the death of the individual, potentially causing entire colonies to be destroyed over on winter. Bats in northeastern America have been estimated to have declined by about 80% since the fungus’ emergence in 2007. WNS has also been recorded in 7 different species of bats in the U.S, two of which are listed as “endangered” and one that is listed as “threatened”. Nearly half of all bat species in the U.S and Canada are reliant on hibernation to survive the winter. With such a wide reach already, it is clear that this could seriously effect many bat species, especially those that are endangered. While it may be easy to see bats as creepy pests, they are actually some of nature’s best pest controllers. Most bats in the U.S are insectivores and have a significant impact on farmers in temperate climates across the nation. Without bats helping to control insect populations, there could be billions of dollars lost to crop damage or increased costs for insecticides.

Sources

WNS.org. (2017, April 17). Bats affected by WNS. Retrieved April 19, 2017, from https://www.whitenosesyndrome.org/about/bats-affected-wns

NWHC. (n.d.). White-Nose Syndrome (WNS). Retrieved April 19, 2017, from https://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/

WDNR. (2016, July). White-Nose Syndrome. Retrieved April 19, 2017, from http://wdfw.wa.gov/conservation/health/wns/

Claim: Climate is causing a Rapid Rise in Lyme Disease Infections

Watts Up With That?

This "classic" bull's-eye rash is also called erythema migrans. A rash caused by Lyme does not always look like this and approximately 25% of those infected with Lyme disease may have no rash. This “classic” bull’s-eye rash is also called erythema migrans. A rash caused by Lyme does not always look like this and approximately 25% of those infected with Lyme disease may have no rash. By Photo Credit: James GathanyContent Providers(s): CDC/ James Gathany – This media comes from the Centers for Disease Control and Prevention‘s Public Health Image Library (PHIL), with identification number #9875.Note: Not all PHIL images are public domain; be sure to check copyright status and credit authors and content providers.English| Slovenščina| +/−, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2546074

Guest essay by Eric Worrall

Zoonotic disease researcher Katharine Walter has claimed that climate is causing a massive rise in human cases of potentially debilitating Lyme Disease. But there are a few problems with this theory.

Deer tick invasion

Encounters with ticks didn’t always cast a dark shadow over North American summers. Cases of…

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Snake Fungal Disease

Snake Fungal Disease (SFD) is a fungal infection in the skin of snakes. This disease is though to be caused by a fungus, Ophidiomyces ophiodiicola, that can survive at a wide range of temperatures and pH’s. O. ophiodiicola typically is found living on a variety of materials, but can also survive in the epidermal and, in some severe cases, dermal layers of snake skin. With such a wide range of suitable conditions, it is no surprise that this fungus has spread rapidly across eastern and midwestern U.S. There is, however, little known about the actual cause of SFD and more research is needed to be sure that O. ophiodiicola is the true cause of SFD. In any case, SFD may play a large role in decreasing the number of free-ranging snakes across the U.S. Although only found in snakes, it has infected a variety of species, making this especially problematic for endangered or threatened species.

Mechanism for Infection

The fungus seems to infect snakes by two methods. The first is a substrate to skin contact, where the snake’s epidermis or an abrasion on the epidermis (the outermost layer of the skin) permits direct contact with the fungus that is living on detritus. The second is through snake to snake contact, where an infected snake has direct contact with a healthy snake. Although thought to be solitary animals, snakes will congregate to reproduce and hibernate (in some cases) allowing easy transmission. Both modes result in a launched immune response and ultimately in a crusty, thickened lesion on the snake’s skin.

Symptoms

  • Scabs/crusty scales
  • Skin nodules (tumor-like lesions)
  • Premature molting/shedding
  • Cloudy eyes
  • Localized crusting or thickening of the skin
  • Ulcers, swelling or deep tissue nodules in the head

Range

SFD has been documented in free-ranging snakes from Canada to Louisiana, indicating a wide-spread case of infectious disease. Recorded instances are concentrated at the eastern and midwestern parts of the country, but it is thought that the actual range might be larger and expanding.

Significance

Very little is known about O. ophiodiicola and what its exact relationship with SFD is. Scientists do not know if this fungus is invasive or a naturally occurring but uncontrolled pathogen. Many species of snakes are effected by this, some of which are listed as “at risk”. Because so little is known about the fungus and how it effects these species, other variables such as climate change and habitat loss only complicate the matter further. Some species appear to be handling the disease well with minimal effects, but others have been severely impacted. High infection rates, high variability in effects and little understanding of SFD and O. ophiodiicola makes for a concerning concoction that may have drastic effects we have yet to see.

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A northern water snake with SFD

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A healthy northern water snake

Sources

NWHC. (2016, May 19). Snake Fungal Disease. Retrieved April 18, 2017, from https://www.nwhc.usgs.gov/disease_information/other_diseases/snake_fungal_disease.jsp

Lorch JM et al. 2016 Snake fungal disease: an emerging threat to wild snakes. Phil. Trans. R. Soc. B 371: 20150457. https://pdfs.semanticscholar.org/27e2/a971b5ecfebaffc363c242c3986e2ed270c5.pdf

CWHC. (n.d.). Snake Fungal Disease. Retrieved April 18, 2017, from http://www.cwhc-rcsf.ca/docs/fact_sheets/SFD_FactSheet.pdf

Tetzlaff, S., Allender, M., Ravesi, M., Smith, J., & Kingsbury, B. (2015). First report of snake fungal disease from Michigan, USA involving Massasaugas, Sistrurus catenatus (Rafinesque 1818). Herpetology Notes, 8, 31-33. Retrieved April 18, 2017, from https://www.researchgate.net/profile/Sasha_Tetzlaff/publication/280134562_First_report_of_snake_fungal_disease_from_Michigan_USA_involving_Massasaugas_Sistrurus_catenatus_Rafinesque_1818/links/55ac3bd008aea3d08685ebb6.pdf.

Glorioso, B. M., Waddle, J. H., Green, D. E., & Lorch, J. M. (2016). First Documented Case of Snake Fungal Disease in a Free-Ranging Wild Snake in Louisiana [Abstract]. Southeastern Naturalist, 16(1), N4-N6. Retrieved April 18, 2017, from http://www.bioone.org/doi/abs/10.1656/058.015.0111