Federal researchers say neurocysticercosis, a brain infection caused by a pork tapeworm, is a "growing public health problem in the United States," especially in states bordering Mexico, where the disease is endemic.
Neurocysticercosis is the "most common parasitic disease of the central nervous system," according to a study jointly conducted by the federal Centers for Disease Control and Prevention and California public health officials, who reported that "international travel and immigration are bringing the disorder to areas where it is not endemic," such as this country.
"Neurocysticercosis is the primary cause of epilepsy in endemic areas. This brain worm is very serious," Victor C. Tsang, chief of the immunochemistry laboratory in the Parasitic Disease Division of the CDC said in a telephone interview.
"Oral-fecal contamination is the standard route of transmission," he said of the condition.
Neurocysticercosis refers specifically to nervous-system disorders caused by cysticercosis, an infection which can also harm eyes and muscles.
"Recent data indicate cysticercosis is an important cause of death in California," Mr. Tsang and other authors wrote in a recent report on the disease published in the European medical journal Acta Neurologica Scandinavica.
A separate report in this month's issue of the journal Emerging Infectious Diseases found that nearly 60 percent of the 221 U.S. deaths from cysticercosis between 1990 and 2002 involved California residents.
"Most patients [187, or 85 percent] were foreign-born, and 137 [62 percent] had emigrated from Mexico. The 33 U.S.-born persons who died of cysticercosis represented 15 percent of all cysticercosis-related deaths" during the study period, said University of California researchers who wrote the latest report.
Although neurocysticercosis is "especially" a problem in the Southwest, it has also surfaced in other places, such as New York, Philadelphia and Charlotte, N.C., data from other studies show.
"In Hispanics and Latinos, neurocysticercosis accounts for 13.5 percent of [U.S.] emergency-room visits for seizures," federal and California investigators wrote in their report in Acta Neurologica Scandinavica published late last year. "The growth is mainly due to immigration from endemic developing countries," they reported.
Neurocysticercosis occurs when the larvae of a pork tapeworm known as Taenia solium enter and infect the brain and spinal cord and form cysts. Another parasitic disease related to consumption of undercooked pork -- trichinosis -- was relatively common in the U.S. before meat freezing became routine. But that disease is caused by a different type of worm, the roundworm Trichinella spiralis.
A person infected with the intestinal tapeworm stage of the infection will shed tapeworm eggs in bowel movements. Tapeworm eggs that are accidentally swallowed by other people can cause infection, the CDC says in information about the disease at its Web site,Centers for Disease Control and Prevention. These eggs are spread through food, water or surfaces contaminated with feces.
"So if you have people cooking for you or handling your food who are tapeworm carriers and don't have good personal hygiene, you will be exposed to the eggs of the tapeworm" and become infected by swallowing food they touch, Mr. Tsang explained.
Carriers tend to be people from rural developing countries with poor hygiene, where pigs are allowed to roam freely and eat human feces. Mr. Tsang said the condition is rife in Mexico and other parts of Latin America and Central America and "in a large part of China and Africa."
Infection with neurocysticercosis most often causes headaches and seizures, but it can also result in mental confusion, balance difficulties and brain swelling that can kill.
Norma Arceo, a spokeswoman for the California Department of Health Services, said 65 cases of neurocysticercosis were reported in that state in 2004, compared with 44 cases in 2005 and 45 cases in the first 10 months of 2006.
