Warning false widow spider bites could lead to hospitalisation as numbers rise in UK

Tuesday, 1st June 2021, 11:34 am
The species was first discovered in Britain more than 140 years ago (Photo: Shutterstock)
The species was first discovered in Britain more than 140 years ago (Photo: Shutterstock)

Spider bites from noble false widow spiders could be so severe that it could lead to hospitalisation, a new study has found.

The findings, published in the international medical journal Clinical Toxicology, confirms that some bite victims can experience symptoms very similar to the true black widow spiders, and require hospital treatment in the most extreme cases.

False widow spiders becoming more prevalent

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The noble false widow originates from Madeira and the Canary Islands, and is similar in appearance to the deadly black widow, although they are significantly less dangerous.

However, a team of scientists from the University of Ireland Galway found that the species may be more harmful than originally thought.

Scientists claim the false widow now has the potential to become one of the world’s most invasive species of spider.

The species was first discovered in Britain more than 140 years ago, but the numbers have suddenly increased in recent decades, significantly expanding its range and density.

The reasons behind the rising numbers are not clear, but scientists have suggested that a new generation mutation within the species may have made the noble false widow more adaptable to new environments.

Human movement has largely contributed to the spread throughout Europe, North Africa, West Asia and parts of North and South America, with the spiders able to move around through the likes of shipping containers and crates across the globe.

In parts of Britain and Ireland, the noble false widow has become one of the most common species of spider found in and around urban habitats.

Dr. Michel Dugon, head of the venom systems lab at NUI Galway and senior author of the study, said: “In addition to their medically significant venom, Noble False Widows are extremely adaptable and competitive in the wild.

“Two decades ago, this species was almost unknown in Ireland, the UK or in continental Europe. We still have much to learn about its genetics, origin, behavior, and development.

“One thing is certain though: this species is here to stay, and we must learn how to live with it.”

Painful symptoms

With the increasing numbers of false widows around homes, bites are now becoming more prevalent and scientists are beginning to realise the full medical importance of these spiders.

The study found that almost all bites occurred in and around the home, with 88 per cent happening when the victim was asleep in bed or when the spider was trapped in clothing.

Envenomation (the process by which venom is injected) symptoms from a false widow bite can be both localised and systemic, and range from mild to debilitating pain, and mild to intense swelling.

Some bite victims have experienced tremors, reduced or elevated blood pressure, nausea and impaired mobility.

In some rare instances, victims have also developed minor wounds at the site of the bite, or had to be treated for severe bacterial infections.

The research team at NUI Galway have established a DNA database to allow clinicians dealing with cases to confirm the species identity using genetic analysis. This is especially important when the spider has been squashed so an accurate identification of the species can be made.

Dr. John Dunbar, postdoctoral researcher at the venom systems lab at NUI Galway and lead author of the study, said: “We only compiled envenomation cases where we had a clear identification of the spider responsible for the bite. We had to rely on DNA extraction and genetic profiling to confirm some cases.

“We are encouraging people to capture a photograph of the spider immediately after being bitten.

“Our latest study confirms without a doubt that Noble False Widows can cause severe envenomations. This species is increasing its range and population density which will undoubtedly lead to an increase in bites.

“While most cases will have a mild outcome, we need to continue to closely monitor bites by the Noble False Widow to understand the potential range of symptoms and to treat severe cases when they occur.”

The team are encouraging members of the public to email them at [email protected] if they think they may have been bitten.