Scientists have for the first time mapped the genomes of tapeworms, shedding light on the evolution of one of humankind's oldest parasites and revealing new possibilities for drug treatments.
DNA analysis of the tapeworms suggests that a number of existing medicines for cancer, viruses and other diseases may be able to fight serious illness caused by their larvae, which can spread through the body causing damaging cysts.
Identifying drugs already approved for other uses should save both time and money, said lead researcher Matthew Berriman of the Wellcome Trust Sanger Institute in Cambridge, eastern England.
"Having existing drugs will act as a chemical starting-point for drug companies, cutting many years off development times."
That may encourage drugmakers, even though devastating tapeworm infections, like echinococcosis and cysticercosis, occur mainly in less developed tropical countries where there is little commercial incentive for drug development.
Larval tapeworms can exist in the body for decades before eventually causing a range of debilitating illnesses and, in some cases, death. Cysts caused by the parasites proliferate throughout the body like cancer, triggering complications such as blindness and epilepsy.
Recorded by the Ancient Greeks, tapeworms were among the first known parasites of humans. Yet finding an effective cure has proved elusive.
Tapeworm cysts are treated by chemotherapy or surgery but side effects are a problem, so new approaches are badly needed.
"These are very grotesque, almost medieval, diseases," Berriman said.
By analyzing DNA from four tapeworm species, the team from the Sanger Institute - where much of the human genome was sequenced more than a decade ago - found weak spots in the animals' genes that drugs should be able to exploit.
Tapeworms have evolved to become increasingly reliant on scavenging from their hosts. The most active genes in the parasites are central to this scavenging process and disrupting their ability to work offers new options for treatment.
Existing drugs which might disrupt the genes include medicines already used for fighting cancer and viral infections, as well as some drugs that work on the central nervous system, Berriman and colleagues reported in the journal Nature.
Applying the new genome information requires further work and clinical trials, although Klaus Brehm of the University of Wurzburg in Germany, a co-author of the Nature paper, is already screening tapeworm cells in the laboratory against some drug candidates.
As well as helping human health, better understanding of tapeworms should also benefit farmers, as cystic echinococcosis in livestock causes some $2 billion in annual losses worldwide.