Experts analyze parasites to find “snail fever” drugs

Scientists have mapped out the genomes of two parasites that cause snail fever, a disease that afflicts 210 million rural people worldwide and for which there is still no vaccine.

Only one drug currently exists to fight the disease, which is also known as Schistomiasis. Experts hope that by laying out the genetic structure of the parasites, new drugs can be designed to fight them.

“We have used state of the art genetic and computational approaches to decipher the genome of this pathogen and to facilitate drug discovery,” wrote Najib El-Sayed, associate professor at the University of Maryland College of Chemical and Life Sciences.

El-Sayed led the team that sequenced the Schistosoma mansoni, one of the two major parasites that cause snail fever.

“Many promising leads for drug development targets have emerged,” he said in a statement.

The Schistosoma mansoni is found in sub-Saharan Africa, parts of the Middle East, Brazil, Venezuela and some Caribbean islands. Some 280,000 people die from snail fever in Africa alone each year.

Another team of experts led by Zhu Chen at the Chinese National Human Genome Center in Shanghai, sequenced the other parasite Schistosoma japonicum, which thrives in southern China, parts of Indonesia and the Philippines.

Both teams published their findings in the journal Nature.

AGE-OLD DISEASE

The age-old disease leaves people so weak they are unable to work. Victims suffer fever, abdominal pain, cough, diarrhea, fatigue and distended bellies in advanced stages of the illness.

People and cattle are ideal hosts of these parasites and those who are infected shed the parasites in their stools, which in turn infect freshwater snails in paddy fields and lakes.

The snails then shed larvae, called cercariae, which are well-adapted to infecting mammals—by tunneling through the tiny pores on their skin.

In China, a million people suffer from the disease, which causes the liver and spleen to malfunction so that victims are unable to expel waste, thereby causing the stomach to bloat up.

Although there is one effective drug, praziquantel, it does not stop reinfection and people get infected repeatedly because they are constantly exposed to the parasite, which thrives in paddy fields, freshwater lakes and rivers.

By Tan Ee Lyn
HONG KONG (Reuters)