Health

Here’s How Worms Get Into Your Brain And How To Prevent It

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The Internet blew up recently on reports that Robert F. Kennedy Jr. had a worm in his brain.

Unfortunately, this medical problem, called neurocysticercosis, caused by larvae of the pork tapeworm, Taenia solium, is common worldwide. There are approximately 1,000 hospitalizations each year in the United States due to neurocysticercosis.

Unlike the fictional worms in “Star Trek2: Wrath of Khan,” that crawl into the brain through the ear, the real larvae in this situation are ingested and can reach not only the brain, but also multiple other organs of the body. Whether or not they cause a problem depends largely on where they end up.

How Does This Happen?

The phenomenon of cysticercosis occurs due to the interesting life cycle of the pork tapeworm, where humans can be infected two ways, which have very different effects. The first way, which leads to a tapeworm, is when humans ingest raw or undercooked pork, called “measly pork,” that contains live larval cysts. The pork meat digests in the bowel, thus releasing the larvae, which attach to the wall of the small intestine and mature into a tapeworm. In this situation, the human becomes a definitive host, because the tapeworm will spend its remaining days (up to two decades) living in the human intestine and producing thousands of eggs intermittently. Those eggs are passed in the feces and either go down the toilet, or if people don’t have toilets, the eggs can contaminate the local soil. The eggs can survive in soil for months, where they can be ingested by pigs.

The eggs hatch in the pigs into larvae, which creates cysts in the muscles (i.e. creating measly pork) and other organs. The life cycle is completed when humans eat the measly pork.

The second method of human infection leads to cysticercosis, which is called neurocysticercosis when the brain is involved. In this situation humans ingest food contaminated with human stool and tapeworm eggs. The food can be contaminated by food preparers who have a tapeworm and don’t wash their hands thoroughly after a bowel movement. Similarly, someone who already has a tapeworm can infect themselves by ingesting eggs if they don’t wash their hands before eating. The eggs hatch into larvae inside the human and travel throughout the body. In this situation, the human becomes an intermediate host, and the larvae never leave the body.

What Are The Manifestations Of Cysticercosis
Many people with cysticercosis are asymptomatic. Once the eggs are ingested, the larvae hatch in the bowel, penetrate the bowel wall and migrate through the blood to multiple areas of the body, frequently to areas that are immune “privileged,” such as the brain, eye, spinal cord. They can also be found in muscle and even the heart. CT scans of humans with a lot of larvae in their brains can look moth-eaten or like Swiss cheese. While alive, the larvae have a way of evading the immune system, so many individuals with cysticercosis can remain asymptomatic for several years.

Larvae in less risky parts of the body calcify when they die and may only be noticed incidentally on an imaging study, such as an x-ray or CT scan, taken for an unrelated purpose. However, when the larvae die, problems can occur due to the body’s inflammatory response, leading to local swelling. The inflammation can lead to seizures if the larvae are in the brain. This has caused significant morbidity, as neurocysticercosis is the number one cause of seizures worldwide.

An Interesting Story
RFK Jr.’s story reminded me of an article I read years ago in the New England Journal of Medicine about four patients in an Orthodox Jewish community in New York City with recurrent seizures. All four patients were diagnosed with neurocysticercosis. This was somewhat surprising, because these individuals and their families would not generally be at risk, as they adhered to strict dietary restrictions against eating pork. Only one patient had come from a country where neurocysticercosis is endemic. So, what was the cause of the infection? The families of the four patients employed housekeepers who were recent immigrants from countries in Latin America, where cysticercosis occurred regularly. Two housekeepers had serologic evidence of prior infection and one had eggs found in her stool, so they were the likely sources of infection, probably while preparing food. The important lesson here is: know the hygienic practices of whomever is making your food.

How Is Cysticercosis Treated?
If someone only has a tapeworm, they should be treated with one of several effective drugs, such as praziquantel or albendazole. Neurocysticercosis is more challenging. Treatment needs to be tailored to the individual patient, and is based on the location of the larvae, and whether the larvae are alive. If someone is asymptomatic, it may be reasonable to leave well enough alone, reassure the patient and not treat them. Anthelminthic (anti-worm) treatment may be needed for multiple larval cysts if they are still alive and causing a problem, possibly in conjunction with steroids to reduce inflammation and swelling. Antiepileptic medicines are used for patients with seizures. Surgery may be required if the larvae are in particularly problematic places, such as inside the ventricular spaces of the brain, because they could obstruct the flow of cerebrospinal fluid. Medications are not effective against dead, calcified larvae.

The consequences of pork tapeworm infections emphasizes key aspects of the importance of public health, as cysticercosis is a preventable infection. First, measures such as meat inspection and sanitation systems play a big role in preventing cysticercosis, and the reason it occurs mostly in less developed areas of the world where these may be lacking. Second, this is just one of the many reasons you want to cook your meat thoroughly, especially pork. Third, your mother was right. It is important to wash your hands before eating, but this goes beyond our mothers and our own habits. You have no doubt noticed those signs in the bathrooms of restaurants that say, “Workers are required to wash their hands before returning to work.” The hygienic practices of those who are making your food matters. Your health really does depend on it, because you don’t want larvae worming their way into your brain.

 

 

 

 

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