October 2, 2022

Another invasive species in Europe. This time a parasite from the tropics causing a dangerous disease

A dangerous parasite that causes schistosomiasis, a dangerous disease that can even lead to death, has been spreading in Europe for several years. The parasite is a hybrid of two different species and seems to be more effective at infecting mammals.

Schistosomiasis is the world’s most prevalent parasitic disease after malaria. Until recently, the range of flatwormsów of sorts Schistosoma, The causative agents of this dangerous disease were limited to tropical regions of theóin Africa, Asia and South America. Recently, however, the parasite appeared in Europe.

Jerome Boissier, a parasitologist at the French Université de Perpignan, was alerted in 2014 about the twoóch almost simultaneous cases of schistosomiasis in France and Germany. Importantly, the families in whichówho were diagnosed with the disease never left Europe.

Schistosomiasis affects an estimated 230 millionóin osób all over the world. Most of the – 85 percent. – is the inhabitants of Africa. The disease can be caused by five speciesóin flukes of the genus Schistosoma and depending on the species of the parasite, whichóry infected the human body, can occur ródifferent symptoms.

Sometimes schistosomiasis is asymptomatic. There are róAlso that symptoms occur many weeks after infection. The most common of these are fever, cough, bóle abdomen or diarrhea. Transverse myelitis can also occur, and prolonged infection can lead to intestinal polyposis with bloody diarrhea, portal hypertension with bloody vomiting, chronic cystitis and urethritis and even death. Although the drug against the parasite is effective, the patient may not know for a long time that he or she is infected.

Epidemiologists traced the history of the two families and so arrived at the Cavu River in Corsica, a French island in the Mediterranean SeaóThe daytime, where the infected swam while on vacation. The researchers found that the local freshwater snail served as an intermediate host, który is essential for the complex life cycle of flatwormsów.

The Cavu River continues to be a hotspot for schistosomiasis infections. Since then, at least 120 waspsób caught the parasite, and the disease appeared throughout Corsica.

Boissier, during his analysis, showed that the culprit of infections in Europe is not a simple fluke of the genus Schistosoma, But a hybrid of the twoóch rótion of different speciesów. Recently, the compositeół scientistów led by him has discovered that this hybrid has advantages over other species. It appears to be superior to the speciesóIn the parent in infecting the zarówell snailów, as well as mammals.

One of the studentóIn Boissier, Julien Kincaid-Smith, published a reprint in the repository of theóin the articleóIn scientific „bioRxiv” sequenced the entire genome of a European hybrid.

Such hybrids, discovered róAlso in other parasitic speciesów, they could expand the species range of potential targetsóinto a parasite, complicating efforts to control them.

Humans and other mammals infected with schistosomiasis spread the parasite’s eggs with feces or urine, whichóre hatch when they reach fresh water. The larvae then seek out a snail of the appropriate species, where they mature and reproduce asexually. The resultingób subsequent larvae leave the worm. If they meet a mammal in their path, they make their way onto its skóhand and settle in blood vessels.

As Boissier stated, the parasites Schistosoma haematobium most likely entered Europe with the vector, który must have become infected elsewhere. The carrier then went to Corsica and passed feces or urine in the Cavu River. This river is home to a snail Bulinus truncatus – one of the few species ofów Bulinus, który can support flukes of the genus Schistosoma. It occurs róalso in someóThe researchers also found that the disease was present in other countries in Africa and the Middle East.

– This is a warning signal to everyone that this disease can develop wherever the right conditions exist – said immunologist Daniel Colley of the University of Georgia in Athens. Colley added that globalization and the constant subróThat around the world make such invasions of new speciesów are increasingly likely.

SyndromeóBoissier’s ł determined on the basis of a testóin the DNA on the parasite’s eggs that the European version is hybridized Schistosoma haematobium i Schistosoma bovis. The hybrids of these parasites themselvesów are also not new. In 2008, similar hybrids were found in Senegal. The researchers therefore traveled to Senegal and Cameroon to collect strains of the parentów hybrids. They took them with them to the lab to re-create the hybrid. They then tested the ability of the parentóin hybrids and the hybrid itself to infect the snail’sów. As an equivalent for humans, they used hamsterów.

During the testów it turned out that parasites Schistosoma haematobium found in Africa did not infect Corsican snailsów. Animal Variety Schistosoma bovis already did, but the hybrid did so much more readily and effectively. It also infected a related snail speciesóin Spain and Portugal. It evolved much faster róalso in hamstersów and caused them to undergo the disease more severely.

Hybrids have also appeared in other parasitic diseases, including the causative agents of malaria, leishmaniasis and Chagas disease. It is currently unclear what role similar hybrids play in parasitology, but their presence is worrisome. They appear to be becoming more prevalent as more subróry and migration.

Hybrids are more effective at infecting many species ofów. They may rómosquitoes also hide in the host’s body, staying out of the reach of drugsów. The combination of the twoóch genomeów gives the parasite more genetic variability, thanks to which itórej can adapt to new locations and hosts.

Meanwhile, schistosomiasis appears to have become well established in Corsica. Parasites continue to infect snails in the Cavu River. On top of that, róAlso in the nearby Solenzara River.