Context: In an exploratory study, the repurposed drug, an anthelmintic originally used to treat tapeworm infection, was found to show promising results in treating COVID-19.

Key Points:

  • The study was undertaken by Bengaluru-based National Centre for Biological Sciences (NCBS-TIFR) and Institute for Stem Cell Science and Regenerative Medicine (InSTEM) along with Indian Institute of Integrative Medicine (CSIR-IIIM), Jammu.
  • A long wait for drugs to treat COVID-19 may come to a close, if Phase II trials of the drug niclosamide deliver positive results.
  • It is well known that the spike protein of the receptor binding domain attaches itself to the ACE2 receptor present in the cell. This is a route the virus uses to enter the cell.
    • There is also another way (Alternative Route) of entering the cell, especially in cells that do not carry ACE2.

Alternative route:

  • The stomach and proximal intestinal epithelium have cells that do not carry the ACE2 receptor but also are infected by the virus
  • The cell line on which currently these institutes work may be a surrogate model for such a system.
  • To enter such cells the spike glycoprotein finds a different pathway using alternative binding proteins on the surface of the cell. 
    • These are not yet fully characterised.
  • This other pathway is under research.

Blocking the Virus:

  • When the virus tries to enter the cell, it is first engulfed in a membranous vesicle. 
  • This vesicle provides an environment of low pH (acidic medium) which is necessary for the virus to infect the cell. 
  • Thus, a substance that would alter the pH of the environment would block the entry of the virus. 
  • This role can be played by, for instance, niclosamide.

Related Facts

About Niclosamide:

  • It is a drug used for tapeworm treatment. 
  • Other worms, such as pinworms and roundworms, are not affected. 
  • It is taken orally so can be used right off the shelf if the dosage and efficacy is proved for Covid.

About Tapeworm:

  • Tapeworms are flat, segmented worms that live in the intestines of some animals. 
  • Animals can become infected with these parasites when grazing in pastures or drinking contaminated water.
  • Eating undercooked meat from infected animals is the main cause of tapeworm infection in people. 
  • Although tapeworms in humans usually cause few symptoms and are easily treated. 
    • They can sometimes cause serious, life-threatening problems. 
  • Tapeworm Types:
    • Six types of tapeworms are known to infect people. 
    • They are usually identified by the animals they come from -- for example; 
      • Taenia saginata from beef, 
      • Taenia solium from pork, and 
      • Diphyllobothrium latum from fish.
  • Tapeworm causes:
    • Tapeworms have a three-stage life cycle: 
      • Egg, 
      • An immature stage called a larva, and 
      • An adult stage at which the worm can produce more eggs. 
    • Because larvae can get into the muscles of their hosts, infection can occur when you eat raw or undercooked meat from an infected animal.
    • It is also possible to contract pork tapeworms from foods prepared by an infected person. 
    • Because tapeworm eggs are passed with bowel movements. 
      • A person who doesn't wash hands well after wiping and then prepares food can contaminate the food.
  • Tapeworm Symptoms
    • Sometimes tapeworms cause symptoms such as:
      • Nausea,
      • Weakness,
      • Diarrhea,
      • Abdominal pain,
      • Hunger or loss of appetite,
      • Fatigue,
      • Weight loss and
      • Vitamin and mineral deficiencies,
    • In rare cases, tapeworms can lead to serious complications, including blocking the intestine, or smaller ducts in the intestine (like the bile duct or pancreatic duct).
    • If pork tapeworm larvae move out of the intestine, they can migrate to other parts of the body and cause damage to the liver, eyes, heart, and brain. 
      • These infections can be life-threatening. 
      • Seizures are the most common symptom.
  • Treatment for Tapeworms
    • The type and length of treatment may depend on the type of tapeworm.
    • Tapeworms are usually treated with a medicine taken by mouth. 
    • The most commonly used medicine for tapeworms is praziquantel (Biltricide).
  • Preventing Tapeworms in Humans
    • Avoid raw fish and meat.
    • Thoroughly cook meat to temperatures of at least 145 degrees Fahrenheit for whole cuts of meat and to at least 160 degrees F for ground meat and poultry. 
    • Then, allow the meat to rest for three minutes before carving or consuming; 
      • The heat continues killing pathogens during that time.
    • Freezing meat to -4 degrees F for at least 24 hours also kills tapeworm eggs.
    • When traveling in undeveloped countries, cook fruits and vegetables with boiled or chemically-treated water before eating.
    • Wash hands with soap and hot water before preparing or eating foods.