Worm genome unlocks disease clues
Cracking code It may not receive as much attention as malaria or tuberculosis, but roundworm infections affect more than one billion people around the world.
Now an international team of scientists led by Dr Aaron Jex from The University of Melbourne have sequenced the genome of the common roundworm (Ascaris suum).
The team hope the genetic roadmap of the giant worm, which infects pigs, can lead to the development of treatments for both animals and humans.
"The main reason we sequenced this [parasite] is that although it's an important parasite in pigs in its own right, it's a very, very close relative and excellent model for a really important parasite in humans which is Ascaris lumbricoides," explains Jex.
"We use this as a model for both parasites so it's important for the pig industry but also very important for human medicine," he says.
Their results appear in today's issue of Nature.
While Ascaris suum causes major losses in the pig industry, Ascaris lumbricoides causes a disease called ascariasis, which kills around 135,000 people — mainly children — each year in developing regions of South East Asia, China, South America and Africa.
The worms are accidently ingested from contaminated food or water and hatch inside the host's intestine causing malnutrition. This in turn leads to long-term physical and cognitive problems especially in children.
The researchers generated a genome sequence for A. suum, from the larval and adult forms of the parasite. They then compared the sequence, which was 273 million bases long, to sequences from other parasitic and non-parasitic round worms including C. elegans to reveal genetic features that may contribute to the parasite's success.
"[The genome] reveals a lot about the basic biology of the parasite — so we can understand how it goes about its life, how it reproduces in terms of the genes that are involved in that process," says Jex.
"In addition, we also learned from this study that ascaris … seem to have an ability to manipulate how the immune system of the host responds against the parasite."
The results for the worm that infects humans is "likely to be similar, if not the same," he adds.
As a result, Jex says sequencing of A. suums could lead to the development of new treatments in both humans and animals.
"Although developing a vaccine against these types of parasites is extremely difficult to do, the hope is the more you understand about that interaction between the parasite and the host at the immune level, the more likely it is that you could try to develop vaccines."
"At least with this information you are a step closer."
With only one drug currently used to treat humans and three for animals, Jex says it is critical that new treatments are developed.
"There haven't been huge advances in developing drugs for these things for quite some time."
"If [the parasites] become resistant to [existing] drugs, we don't have an alternative."
"By sequencing the genome … we can hopefully develop new drugs. If and when these [parasites] become resistant to [existing] drugs we have a back up. Without that, we have no mechanism to control the parasite."