The cysticercus of the pork tapeworm, Taenia solium, in the brain causes a serious condition known as neurocysticercosis. Neurocysticercosis is major cause of acquired seizures in those infected.
Researchers at the Baylor College of Medicine, in a study published in the online journal, PLoS Pathogens, say a neuropeptide called Substance P is the cause of seizures in patients with neurocysticercosis.
In a Baylor College of Medicine news release Thursday, Dr. Prema Robinson, assistant professor of medicine notes, "It is particularly important to understand the source of these seizures (caused by neurocysticercosis) in order to develop ways to treat and prevent them."
Understanding that Substance P was involved in inflammation, Dr. Robinson set out to see if it was also involved in seizure activity.
According to the news release:
Robinson and her colleagues – including one from Tufts Medical Center in Boston – found Substance P in autopsies of the brains of patients who had the tapeworm infection. They did not find Substance P in uninfected brains.
"As long as the parasite is alive, nothing happens," said Robinson. However, once the worm dies, the body responds with chemicals that recruit immune system cells to the site of infection, causing inflammation. Her studies showed that the cells that produce Substance P are found mainly in areas of inflammation near the dead worms.
Animals injected with Substance P alone or with extracts from the areas of inflammation (granulomas) near the worms in infected mice suffered severe seizures, she said.
When the rodents received the drug that blocks the Substance P receptor, they did not have seizures, she said.
In addition, mice that lacked the Substance P receptor did not have seizures even when injected with the extracts of granulomas from infected mice. In addition, granuloma extracts from mice that lacked the cells that make Substance P did not induce seizures.
Drugs are available to block Substance P receptors, which could prove effective in treating and preventing seizures in cases of neurocysticercosis.
What is the pork tapeworm?
Taenia solium is a tapeworm that people get from eating raw or undercooked “measly pork”. The pork meat has cysticerci (the larval stage) which in the human intestine mature to an adult tapeworm. Here the tapeworm attaches to the intestine and produces thousands of eggs.
Does the pork tapeworm cause disease while in the intestine?
Most people are asymptomatic and only become aware of the tapeworm by noticing segments of the worm in their feces. Symptoms of infection, if any, are general: nausea, intestinal upset, vague abdominal symptoms such as hunger pains, diarrhea and/or constipation, or chronic indigestion.
What is cysticercosis?
Human cysticercosis occurs either by the direct transfer of Taenia solium eggs from the feces of people harboring an adult worm to their own mouth (autoinfection) or to the mouth of another individual, or indirectly by ingestion of food or water contaminated with the eggs. When the person ingests the eggs, the embryo escape from the shell and penetrates the intestinal wall, gets into the blood vessels, where they spread to muscle, or more seriously, the eyes, heart or brain.
How serious is cysticercosis?
The severity of cystercercosis depends on which organs are infected and the number of cysticerci. An infection consisting of a few small cysticerci in the liver or muscles would likely result in no obvious disease and go unnoticed. Those that form in voluntary muscle tend to be asymptomatic, but may cause some pain. On the other hand, a few cysticerci, if located in a particularly "sensitive" area of the body, might result in irreparable damage. For instance, a cysticercus in the eye might lead to blindness, or a cysticercus in the brain (neurocysticercosis) could lead to traumatic neurological damage, epileptic seizures or brain swelling that can kill.
Neurosysticercosis is the number one cause of acquired epilepsy in the developing countries of Latin America and is an increasing problem in the United States.
How long after infection do symptoms of cysticercosis appear?
It may be as short as a few weeks or up to 10 years or more.
Is it treatable?
It can be treated with anti-parasitic drugs like praziquantel and steroid therapy to control brain swelling. Occasionally surgical intervention may be required to relieve symptoms.
How do you prevent this disease?
In the U.S., laws have been passed that requires meat inspection for cysticerci prior to meat being put on the market of human consumption.
Adequate cooking of meat destroys the tapeworm larvae and will prevent infection by tapeworm. Freezing meat to -5C for 4 days, -15C for 3 days, or -24C for 1 day kills the larvae as well.
Good hygiene and hand washing after using the toilet will prevent self-infection in a person already infected with tapeworms in addition to contamination of foodstuffs by human feces.
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