Egg-cellent breakthrough in Parasite Research

Schistosome Egg

Electron microscope image of Schistosome egg after Smp14 protein has been inhibited. Egg contents are ‘leaking out’ of the holes formed due to eggshell defects. Image credit: Marcelo Rosado Fantappie.

There is a recent paper in PLOS Pathogens (Open Access) which represents a really interesting development in parasite control. You can read the full paper here.

✤ Schistosomiasis is a disease caused by parasitic worms of the Schistosoma genus. It affects over 200 million people worldwide, and kills an estimated 300,000 people each year.

✤ Currently there is only one drug (Praziquantel) to treat infections caused by all the different species of Schistosoma. Use of this drug does not prevent reinfection and is not effective against juvenile worms. Understandably, the development of drug resistance is a big worry. Therefore any alternative methods for controlling infections would be very useful.

✤ The life cycle of the parasite is somewhat complex; eggs are eliminated with faeces into the environment, and they hatch under optimal conditions. Once the eggs hatch, the larvae (known as miracidia) swim and infect specific snail intermediate hosts. Once inside the snail they grow further into another larval stage known as cercaria. The cercariae are infective, and are able to penetrate the skin of the human host. Once inside humans, they develop into adult worms, and migrate into the organs to have lots of sexy time. This produces up to 300 eggs per day per reproductive pair.

✤ Obviously, egg production is therefore important in the life cycle of the Schistosoma. Could this be a way to control Schistosome infections? Researchers focused on the mechanism of eggshell development at the molecular level. They found that one of the key proteins involved in eggshell development is Smp14. The gene for Smp14 is the most abundant RNA transcript in sexually mature females.

✤ Remember that generally speaking, DNA makes RNA makes protein (see here for a more detailed explanation of this pathway). Preventing the translation of Smp14 RNA transcript into Smp14 protein would therefore be a valid approach for disrupting egg production.

✤ Indeed, this was the case. Inhibiting the production of Smp14 protein resulted in disrupted eggshell formation. The eggs that were produced had severe defects – they had holes on their surface, which resulted in the egg contents ‘leaking’ out (see image).

✤ By decreasing the number of viable eggs deposited in the environment, it is possible to limit the transmission of the parasites. This work therefore represents a very attractive route for the development of more effective treatments for the disease.

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