KURU-The Laughing Sickness

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1) Normal human brain vs the brain of people affected by kuru

2) Normal protein holdings vs irregular prion folding

What is kuru?

In regions of Papa New Guinea around 1957, Kuru, popularly known as the laughing sickness, a fatal neurodegenerative prion disease caused an epidemic that affected around 17,000 people and killed 2,700. It is one of the highly transmissible spongiform encephalopathies.

This destructive disease is believed to originate due to the practice of cannibalism followed as a funeral ritual in certain tribes of the country.

Kuru originated in 1957, and the latest reported death was in 2005. Since the incubation time (time period it takes for symptoms of a disease to show after being affected) can be up to 40 years, it took an exceptionally long time to identify patients and treat them accordingly.

The symptoms of kuru are divided into three phases-Ambulatory, Sedentary and terminal. Some symptoms that prolong through all three phases are-

• poor coordination

• difficulty walking

• difficulty swallowing

• slurred speech

• dementia

• muscle twitching and tremors

• random boults of laughing and crying

loss of cerebellum was noticed in several patients who also experienced loss of sensory and motor control.

How is kuru caused?

Kuru was once thought to be caused by a virus, but is now confirmed that it is essentially a prion disease, ie, it is caused by infectious prion proteins found in contaminated meat, especially the brain. It can also spread through body fluids like feces, saliva, blood, or urine, either through direct contact or indirectly through environmental contamination of soil, food or water. An interesting observation was that affected mothers did not pass the disease on to their newborns, suggesting that maternal transmission does not occur. Kuru affected women and children more than males, as they were fed the leftovers of the body which included the brain while the men consumed other parts.

What are Prions?

Prions (name derived from proteinaceous infectious particle) are misfolded or abnormal proteins that have the ability to make normal proteins fold abnormally.

Overtime, prions multiply and accumulate to form amyloids and plaques (also associated with neurological disorders like dementia, Alzheimer’s, etc.) causing cell and tissue damage/death.

The protein that prions are made up of (PrP) is found throughout the body, however the one found in infectious material has a different structure.

The normal function of prions is not yet understood clearly, although it is present in every individual. Some studies conducted on mice revealed that prions have a role in activating myelin repair in schwann cells in the peripheral nerves, and in the absence of prions, the nerve cells were demyelinated. They also have an indistinct role in long time memory.

How can kuru be treated ?

Currently there is no cure for any prion disease. Normally, protein disorders are treated with proteases, the enzyme that breaks down proteins. However, prion is one of the only proteins that is resistant to proteases due to the different conformations forming aggregates, and hence cannot be used. Majority of the affected passed away in the first 24 months after the symptoms.

- Aalia Imran