Prions and Viroids

Ebola, HIV, and SARS (Severe Acute Respiratory Syndrome)

3 major viruses are:

Ebola (killer virus)

It is an RNA virus that spreads by close contact and kills between 25 and 90 percent of victims

There is no cure or vaccine

The Ebola virus is a zoonotic disease. Zoonotic diseases involve animals and humans

Bats are the reservoir host for the ebola virus

symptoms of early stage ebola

headache, fever, fatigue, muscle pain, and sore throat

symptoms of advanced stage ebola

Impaired liver and kidneys, diarrhea, vomiting, rash, internal and external bleeding, and bleeding from eyes, nose, and mouth

preventative measures for Ebola

Stop contact with infected animals and the consumption of their meat

Isolate the sick

Prompt disposal of victims’ bodies

Disinfect homes of dead and infected

Protective clothing for healthcare workers

There was a facility in Reston, Virginia, that had monkeys that were dying. CDC and other organizations took plane flights to examine the monkeys. They discovered that an Ebola-type virus was killing the monkeys. By this time, thousands of people had been exposed. But this was an Ebola that was only fatal to monkeys, it was not fatal to humans. If it had been Ebola that killed humans, we would have had a major outbreak in the United States

The Hot Zone is a nonfiction book dealing with Ebola in the United States.

is very dangerous because it affects the immune system. It is also an RNA virus, and it has an envelope

The Human Immunodeficiency Virus (HIV) that causes AIDS:

activate B cells that produce antibodies ad activate Killer T cells that destroy infected cells

HIV infects Helper T cells. Normally Helper T cells have two functions:

People with AIDS die of secondary infections, like pneumonia, because their immune system could not fight the infection

Without Helper T cells functioning properly, you cannot effectively fight off pathogens that can make you sick.

Severe Acute Respiratory Syndrome or SARS

Caused by SARS coronavirus

Outbreak in China in 2002-2003

No cases since 2004

Severe Acute Respiratory Syndrome symptoms

Flu-like including fever, lethargy, myalgia, and cough.

Fever above 100.4°F was the only symptom that all patients had in common

Chest X-rays for SARS show atypical pneumonia, normally with patchy infiltrates

Chest radiographs of index patient with severe acute respiratory syndrome (SARS). a, day 5 of symptoms; b, day 10; c, day 13; d, day 15.

COVID 19

A contagious respiratory disease that was first detected in China in December 2019 has spread worldwide. The 2019 novel (new) coronavirus has been named SARS-CoV-2, and the disease it causes is called coronavirus disease 2019, or COVID-19

We learned about this particular virus shortly after a cluster of severe pneumonia cases were reported on New Year's Eve 2019 in Wuhan, which is in the Hubei Province of China

This virus is really transmissible and can spread easily from person to person even before a person develops symptoms. It's carried on respiratory droplets when we talk, sneeze, and cough, and these can land on surfaces or in someone's mouth or nose. When it comes to respiratory droplets, 6 feet is the magic distance. That's how far these tiny, infected droplets can travel. Being within 6 feet of someone who is sick can get you or your personal space contaminated with COVID-19

When droplets land on surfaces, we can pick them up with our hands and transfer them to our eyes, mouth, and nose when we touch our faces. This is why hand hygiene is so important. Good hand hygiene means washing our hands not just after we're using the restroom or before we're eating, but regularly throughout the day. Respiratory secretions (like snot and sputum) are also infectious, so cover your coughs and sneezes, use disposable tissues, throw them away when you're done, and wash your hands afterward. Keep your work surfaces clean and wipe off your keyboard and your phone

prions

are infectious proteins that have no genetic material

viroids

are infectious agents with genetic material that do not have protein

neither prions or viroids are viruses

prion

a type of protein that can trigger normal proteins in the brain to fold abnormally. Prion diseases can affect both humans and animals and are sometimes spread to humans by infected meat products

prion diseases

the infected protein comes in contact with a healthy protein and transforms it into an abnormally folding protein

prion disease comparison is like a zombie in the walking dead bites someone and they turn into a zombie

Elk brain tissue

the light spots show spongy areas where tissue has been destroyed

Elk brain tissue with chronic wasting disease. The gaps in the brain tissue are because of the abnormal folding with the prion tissues

Types of prions found in animals

Bovine Spongiform Encephalopathy (BSE) - is the main one, known as mad cow disease

Chronic Wasting Disease (CWD) - affects deer

Scrapie - affects sheep

Transmissible Mink Encephalopathy - affects mink

Feline Spongiform Encephalopathy - affects cats

Ungulate Spongiform Encephalopathy - affects the group of animals, the ungulates

Bovine Spongiform Encephalopathy or BSE

A chronic, degenerative disease that affects the central nervous system (CNS) of cattle

Commonly referred to as "mad cow disease"

mad cow disease

Mad cow disease, or bovine spongiform encephalopathy, is a neurological disorder in cattle. It is caused by an abnormal protein called a prion that infects a cow's central nervous system and causes brain and nerve cells to die. Prions are passed to humans through consumption, and that can trigger the human form of the disease.

How it spreads from cows to humans

1. A person eats contaminated food. Prions are found primarily in brain or spinal cord tissue from an infected animal.

2. After a person ingests infected meat, prions spread to the brain through the body's lymph nodes and immune system, where they can remain dormant for years.

3. Disease attacks the nervous system. Outer layer of brain develops tiny holes, looks spongy. The host goes into seizures; death may occur.

Prevention of mad cow disease

Eradication: Infected farm animals are destroyed.

Regulations: Animal products containing brain or central nervous system tissue aren’t used as livestock feed.

Consumers: Avoid beef that contains parts of the cow’s main nervous system. Prions are heat-resistant, so cooking the meat will not reduce the risk.

If 1 cow had BSE out of 100 cows, and the 100 cows ate the ground-up cow with BSE, then those 100 other cows have now been exposed to BSE

After cows were slaughtered, the meat industry ground up their bones, organs, and nervous tissue to put in cow feed to feed cattle to save money.

chronic wasting disease

Prion disease attacks deer and elk in the brain and brain stem

Diseased tissue resembles a sponge; affected cells develop large holes called vacuoles

Types of prions in humans

Creutzfeldt-Jakob Disease (CJD)

Variant Creutzfeldt-Jakob Disease (vCJD) - mad cow disease has an impact on human health and can create that variant to people who have eaten cow

Kuru

Creutzfeldt-Jakob Disease (CJD)

is caused by abnormal proteins called prions that are not killed by standard methods for sterilizing surgical equipment

As prions build up in cells, the brain slowly shrinks and the tissue fills with holes until it resembles a sponge

Consequences - Those affected lose the ability to think and to move properly and suffer from memory loss. It is always fatal, usually within one year of the onset of illness

Creutzfeldt-Jakob Disease under a microscope

cerebral cortex with coarse and fine vacuolations (spongiosis)

Kuru

Identified by epidemiology in New Guinea based on anthropological research by Robert and Louise Glasse in the 1950s

1% of the Fore tribe was afflicted, mostly women, some children, few adult males

Symptoms: headache, joint pain, then 6-12 weeks later, difficulty walking, then death, usually within 12 months, always within 2 years

Disease was of recent origin: 1910-1920

Epidemiological evidence led the Glasses to suggest that endocannibalism was associated with disease

This hypothesis was not well accepted among the medical community

endocannibalism

eating a dead loved one

Viroids

Unlike viruses, only made up of genetic material (SS RNA)

No protein coat

Only a little larger than prions

Mainly in plants

Spread through contact between plants. Example is potato spindle viroid