Guam disease linked to eating bats
By Jan TenBruggencate
Advertiser Science Writer
LAWA'I, Kaua'i — Toxic fruit bats may be at the heart of a bizarre disease on Guam that is a combination of Alzheimer's, Parkinson's and Lou Gehrig's diseases.
Jan TenBruggencate • The Honolulu Advertiser
Fruits bats — also called flying foxes — are a rare delicacy in the U.S. territory, which lies 3,800 miles west of Hawai'i. Two scientists studying the strange malady known on the island as lytico-bodig theorize that the bats eat poisonous seeds of a cycad plant, a type of palm, and that the toxin builds up in their tissues.
Ethnobotanist Paul Alan Cox examines a Guam cycad growing in Lawa'i, Kaua'i. The plant's toxic seeds are eaten by Guam bats.
When humans eat the bats, they may get a concentrated dose equivalent to eating hundreds of pounds of the seeds, said ethnobotanist Paul Alan Cox, director of the Kaua'i-based National Tropical Botanical Garden.
Writing in the March 26 issue of the journal Neurology, Cox and famed neurologist Oliver Sacks, whose book was the basis for the movie "Awakenings" with Robin Williams, said the toxins may be accumulating in the bats' fat.
Previous scientific study identified the cycad plant as a possible suspect in lytico-bodig. The native people of Guam — Chamorros — used its seeds to make flour for tortillas, but scientists have yet to confirm that the seeds are the culprits behind the illness.
Still, the research by Cox, Sacks and others suggests a possible dietary link to the three devastating neurodegenerative diseases.
Superficially, the diseases are quite different. Alzheimer's is associated with memory problems. Parkinson's most familiarly involves tremors of the extremities, and Lou Gehrig's, or amyotrophic lateral sclerosis (ALS), involves a slow, progressive paralysis.
The Guam disease, first identified in 1945, is sometimes called ALS-PDC, for ALS with Parkinson-dementia complex.
Chamorros suffered from lytico-bodig or ALS-PDC at rates as much as 400 times higher than those in the general population. During the 1940s, it was the top cause of death among Chamorros.
Cox said the disease seemed to peak during the middle of the last century. Oddly, Chamorros who left Guam and took up an American diet did not get the disease, and people who moved to Guam, married into Chamorro families and took up a Chamorro diet, did get it.
"The only consistent thing is consumption of a Chamorro diet," Cox said.
The one thing unique in the diet is the eating of fruit bats, called fanihi on Guam, which are boiled whole in coconut milk.
"It's all sort of linked. Maybe something in cycad seeds could be bioaccumulating" in the animals, he said.
One factor that Cox said supports the theory is that the rates of the disease increased when Guamanians got guns to replace inefficient hunting techniques and began increasing their fruit bat consumption. And once the Guam bat population plummeted, the rate of the disease dropped. One of the two Mariana fruit bat species is extinct, and the other is now rare and protected, he said.
Chamorros continued eating fruit bats, importing them from Samoa and other places in the Pacific where generally cycads were not present or not a major part of the animal's diet.
A research team at the National Tropical Botanical Garden is using sophisticated chemical equipment to test preserved museum specimens of Guamanian flying foxes for toxins. They also plan to feed cycad seeds to Samoan fruit bats, which are closely related to the Guam bats, to see if they begin building up toxins in their systems.
It is possible that the toxin suspected of causing the disease is the same compound that's in the cycad seeds, or perhaps it is something that the bat's body metabolizes from the seeds, Cox said.
Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808)245-3074.
