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Schistosome Research: Using basic biological research to fight schistosomiasis

Although schistosomes are thought to kill an estimated 250,000 people every year, perhaps the greatest tragedy is the chronic disability associated with infection. Those with the most serious symptoms are often children who can suffer from malnutrition, anemia, stunted cognitive and physical development, physical pain/discomfort, and chronic inflammation. Diseases like schistosomiasis may also enhance the probability of contracting diseases like HIV/AIDS though sexual contact. The cumulative effect is that those who are chronically infected are effectively robbed of their ability to lead productive lives, condemning themselves (and likely their families) to a life of poverty. Being impoverished…

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 The Schistosomes

Trematodes from the genus Schistosoma that live in the blood vessels of humans and other mammals. Adults have separate sexes (different from other trematodes). Disease called schistosomiasis or Bilharziasis, named after Theodore Bilharz. Can cause acute and chronic disease, a disease-complex. Most important helminth infection in terms of worldwide distribution, prevalence and morbidity.

Articles of Interest

What is a Schistosome or a blood fluke?

Schistosomes cause the disease schistosomiasis also known as Bilharziasis and Snail fever. Cases of schistosomiasis begin when the body is invaded by the parasite in its infective stage, known as cercaria. Cercariae are released by the freshwater snails and swim freely in open bodies of water. The cercariae penetrate the skin of bathers in lakes and ponds where snails abound and cause a dermatitis often referred to as "swimmer's itch." The cercariae then mature into another larval form known as schistosomula.

New Tools for Old Questions: How Strictly Human Are “Human Schistosomes”—And Does It Matter?

Human schistosomiasis has been documented in Egyptian mummies from the time of the early Pharaohs. Efforts to control it in endemic areas have been ongoing since the discovery of the main species of human schistosomes in the early part of the 20th century. Many of these early efforts focused on control of the snail hosts and water engineering, due to the lack of an easily applied, field-applicable drug. During that first golden age of parasitological discovery, there were many investigations to determine whether human-infecting schistosome species were zoonotic and which, if any, other vertebrates could be definitive hosts.

Schistosoma

Unlike all other trematodes, schistosomes are not hermaphroditic but dioecious, forming separate sexes. Adult worms have elongate tubular bodies, each male having a unique gynecophoral canal (schisto-soma = split body) in which a female worm resides. They live inside visceral blood vessels and are commonly known as blood flukes. They have digenetic life-cycles involving aquatic snails as obligate intermediate hosts.

Schistosoma spp.

Transmission occurs in water contaminated with feces or urine. Free swimming cercariae directly penetrate through the skin to infect humans.

Schistosome: Its Benefit and Harm in Patients Suffering from Concomitant Diseases

Schistosoma spp., blood flukes, are parasitic helminths found mainly in developing countries with a tropical or subtropical climate and affect 200 million people worldwide.

Schistosomes and Other Trematodes

Free-swimming larvae (cercariae) are given off by infected snails. These either penetrate the skin of the human definitive host (schistosomes) or are ingested after encysting as metacercariae in or on various edible plants or animals (all other trematodes).

The sex lives of schistosomes; complexed mixing of genomes

Schistosomes are diverse parasites with many described species. They are transmitted in different parts of the world, their distribution being largely dependent on the presence of their specific snail hosts. In Asia, schistosomiasis is known to be zoonotic, which considerably hampers control efforts and emphasises the need for a One Health approach, and now this scenario could be evolving in Africa facilitated by inter-species hybridisation.

Tropical Disease: Dissecting the schistosome cloak

Schistosomes belong to the animal clade called neodermata, which consists of approximately 100,000 species of parasitic flatworms (Littlewood, 2006). The key evolutionary innovation defining this clade is a skin-like structure called the tegument that allows the parasites to withstand particularly harsh environments, such as the human digestive system and the bloodstream. It also helps the worms to absorb nutrients and attach to their hosts, important adaptions that potentially enabled the worms to become parasites.

Resources

Schistosome Snail Resource

The Schistosome Snail Resource (SSR) is an open access biomedical resource that aims to generate and make freely available live schistosome life-cycle stages, snail intermediate hosts and related material for schistosomiasis research. It’s main focus will be to provide bespoke material, species and strains, not currently available in laboratory life-cycle systems in the UK.

Schistosomiasis Control Initiative

The Schistosomiasis Control Initiative (SCI) is a systematized capacity building approach established on rigorous data that seeks to achieve schistosomiasis control and elimination in high-endemic, low-income countries.