The new genealogy of parasites

Antti Lavikainen has chased tapeworms in Siberia and on the heels of bear hunters. In his research, he rewrote their phylogenetic history, forcing his colleagues the world over to update the textbooks in the field.

“The parasitic flatworm known as the tapeworm used to be considered a weight-loss aid,” explains Antti Lavikainen, a clinical instructor at the University’s Haartman Institute.

Transmitted through improperly cooked fish, the tapeworm was still quite common in Finland in the first half of the 20th century. One could even have called it our national parasite. Inside the intestine, the worm could grow to an impressive 20 metres in length.

Currently tapeworms are rarely found in Finns.

Lavikainen received the University of Helsinki Dissertation Award for his dissertation on the phylogenetic history and taxonomy of Cestoda worms.

Lavikainen’s colleagues around the world are currently rewriting textbooks based on his findings. Species recognition has traditionally relied on morphological (i.e., anatomical) observations, but Lavikainen used new methods such as DNA analysis.

Brains or guts

“Maybe the biggest thing was the discovery of the Taenia arctos, a worm that cycles between bear and elk hosts,” the researcher muses.

About forty species of Taeniidae are known worldwide, three of which can live in humans in their adult form.

Many more species of Taeniidae can use humans as intermediate hosts for their larval stage, even though we are a poor choice for the parasite, a dead end. Once inside the body, the unwelcome guest digs into tissues and can develop into a parasite cyst.

The most unpleasant genus is Echinococcus. This variety usually damages the liver or lungs, but can bore into other organs as well, even the brain.

Bullet-riddled worms

As a student, Lavikainen was an enthusiastic wilderness hiker. In 2003, he combined his love for the outdoors with science and set out to find specimens of Echinococcus in the voles of central Siberia. He found none of that variety, but discovered another – the Taenia mustelae.

“While studying the specimens, I found that the species was very unlike the genus Taeniidae. This led to T. mustelae being described as a separate genus named Versteria.”

In the autumn of 2010, Lavikainen was working in Ilomantsi during bear hunting season.

“I pitched my field laboratory under a tarp to shelter myself from the rain. The structure eventually collapsed on me.”

Only one bear had tapeworms, and they had been damaged by bullets, but there it was: a new species! It was called Taenia arctos, the bear tapeworm. The last time a new species in the Taenia genus was discovered was in the 1990s in America.

“Discovering a species was an exciting experience overall and combined happy coincidence with hard work and planning. The work progressed like the scientific process does at its finest and left me feeling like a winner,” Lavikainen grins.