The world’s press reports how doctors removed a live worm from a woman’s brain at a Canberra hospital. The woman had previously been admitted to hospital with digestive symptoms, a dry cough and night sweats. A few months later, she had suffered from depression and memory loss which led her to perform a brain scan.
In the case study published in the journal Emerging Infectious Diseases, doctors describe removing an 8cm-long live nematode (roundworm) from the brain of the immunocompromised 64-year-old woman. The worm has been identified as O. robertsi, native to Australia, where it lives on carpet pythons. The woman was said to have come into contact with worm eggs via snake droppings while foraging for green vegetables.
It is important to note that this is an extremely rare event even though the headlines may seem alarming. However, there are more common parasites that can infect your body and brain. And there are ways to minimize your chances of getting infected.
What are common pests and how do they get in?
Parasitic infections are extremely common. Perhaps the most common type is the pinworm (Enterobius vermicularis, also called threadworm), which is thought to be present in more than a billion people worldwide, especially children. Pinworms are about 1 cm long and are specific to human hosts. They cause intense itching and are transmitted from person to person. A myth says that it could be developed by pets.
Giardia (Giardia duodenalis) is also very common and can contaminate food, water and surfaces. This waterborne parasite is associated with poor sanitation and causes gastric symptoms such as diarrhea, cramping, bloating, nausea, and fatigue. Giardia cysts (little sacs of immature parasites) spread disease and are passed in the stool, where they can remain viable in the environment for months before being consumed by someone else. They can also be ingested through raw or undercooked foods (such as mutton).
Two types of hookworms – Necator americanis and Ancylostoma duadonale – are found in soil. Only Ancylostoma duodenale is a problem in Australia and is generally found in isolated communities.
When a person is infected (usually barefoot or contaminated shoes), these worms enter the bloodstream and then reach the lungs. From the bronchi located in the upper part of the lungs, they are swallowed with secretions. Once in the intestine and small intestine, they can cause anemia (low iron). This is because they consume nutrients and affect iron absorption. They also release an anticoagulant which prevents the human host’s blood from clotting and causes minute blood loss.
Fortunately, these very common parasites do not infect the brain.
Worldwide, it is estimated that 30 to 50% of people are infected with Toxoplasma. Most people will be asymptomatic, but many show signs of infection.
Parasites can stay in the body for years as tiny tissue cysts. These cysts can be found in the brain, heart, and muscles. Infants can be born with severe eye or brain damage if their mother is infected during pregnancy. People with weakened immunity – for example due to AIDS or cancer treatment – are also at risk of illness from infection from pet cats or raw meat.
Then there are tapeworms and amoebas
Tapeworms can infect different parts of the body, including the brain. This is called neurocysticercosis and is the leading cause of epilepsy worldwide. Neurocysticercosis is rare in the Western world and infection is usually through the consumption of raw or prepared pork by someone infected with tapeworm (Taenia solium). This is more likely in places where pigs come into contact with human feces via sewers or waterways.
Tapeworm larvae can infect muscles and soft tissues. Brain tissue can harbor the larvae because it is soft and easily accessible via blood vessels. Brain infection can cause headaches, dizziness, seizures, cognitive impairment, and even dementia, due to increased cerebrospinal fluid pressure.
Additionally, Naegleria fowleri is an amoeba found in lakes, rivers and springs in warm climates, including Australia. People who swim in infected waters may have the parasite enter their body through their nose. It then travels to the brain and destroys brain tissue. The condition is almost always fatal.
4 Ways to Avoid a Parasitic Infection
We know that being infected with a snake parasite is very rare – finding one alive in someone’s brain is even rarer. But parasites are all around us. To minimize your risk of infection, you can:
1. Avoid undercooked or raw pork. Freezing the meat first can reduce the risk (although home freezers aren’t cold enough) and it should be cooked to a high internal temperature. Avoid pork if you are traveling to places with poor sanitary conditions.
2. Avoid jumping or diving into warm, cool bodies of water, especially if they are known to contain Naegleria fowleri. Even if only a handful of cases are reported each year, you must assume they are present.
3. Practice good hand hygiene to reduce the risk of rare and common infections. This means washing your hands thoroughly and often, using soap, scrubbing for at least 20 seconds, rinsing and drying thoroughly. Trim and clean under nails regularly.
4. To avoid soil-borne pests, wear shoes outdoors, especially in rural and remote areas, wash shoes and leave them outside.
This article was written by researcher Vincent Ho and published on the site The Conversation.
