Ireland’s most venomous spider bites can result in hospitalisation

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A team of scientists from NUI Galway have published a new study showing that Ireland’s most venomous spiders can deliver a bite that requires hospitalisation.

The threat posed by the Noble False Widow spider has been debated among spider and healthcare specialists for many years.

It has now been confirmed that some bite victims experience symptoms very similar to the true black widow spiders and some severe cases require hospitalisation.

Originating from Madeira and the Canary Islands, the Noble False Widow spider Steatoda nobilis, now has the potential to become one of the world’s most invasive species of spider.

It was first documented in Britain over 140 years ago, but in recent decades the species has suddenly increased in numbers, significantly expanding its range and density.

Envenomation symptoms can be both localised and systemic, ranging from mild to debilitating pain and mild to intense swelling.

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

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

Dr Michel Dugon, Head of the Venom Systems Lab at NUI Galway and senior author of the study, said that 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,” said Dr Dugon.

“We still have much to learn about its genetics, origin, behaviour and development. One thing is certain though: this species is here to stay, and we must learn how to live with it.”

Dr John Dunbar, Postdoctoral Researcher at the Venom Systems Lab at NUI Galway and lead author of the study, added that speculations around the potential severity of the bites by the Noble False Widow have been debated for many years.

“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 (the process by which venom is injected).

“This species is increasing its range and population density which will undoubtedly lead to an increase in bites (since submitting our study in March we have already received further confirmed bite cases).

“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.”

Aiste Vitkauskaite, MSc student in Toxicology at NUI Galway and joint lead in the study, said: “Approximately ten species of Irish spiders have fangs large enough to bite through human skin, yet over the past five years, we have never heard of anybody being bitten by any of the native species.

“Within the same period, we have recorded dozens of confirmed or probable False Widow bites. These spiders will become increasingly common and so will their bites.”