Dark web: False widow spider sinking its venomous fangs into people all over Ireland

Noble false widow spiders can deliver a venomous bite that can cause symptoms ranging from mild to debilitating pain and mild to intense swelling. Picture: Dr John Dunbar

Irish scientists have discovered that a bite from one of the nation’s most common spiders can result in hospitalisation.

A new study from NUI Galway has found that noble false widow spiders can deliver a venomous bite that can cause symptoms ranging from mild to debilitating pain and mild to intense swelling.

Severe bacterial infections

Some victims have experienced tremors, reduced or elevated blood pressure, nausea, and impaired mobility while in rare instances, victims have developed minor wounds at the bite site or had to be treated for severe bacterial infections.

The threat posed by the noble false widow spider has been debated among spider and healthcare specialists for many years but the new study confirms that some bite victims experience symptoms very similar to the true black widow spiders – and some severe cases require hospitalisation.

Some victims have experienced tremors, reduced or elevated blood pressure, nausea, and impaired mobility while in rare instances, victims have developed minor wounds at the bite site or had to be treated for severe bacterial infections. Picture: Dr John Dunbar, Venom Systems Lab at NUI Galway.

The study authors say the spider is rapidly becoming open of the most common spiders in and around houses across Ireland.

The research team at NUI Galway has 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 spider can be made.

Trapped in clothing

The study, published in the international medical journal Clinical Toxicology, also reveals that almost all bites occurred in and around the home, and 88% of bites occurred when the victim was either asleep in bed or when the spider was trapped in clothing.

Dr Michel Dugon, head of the Venom Systems Lab at NUI Galway and senior author of the study, said Irish people will have to adapt to this venomous spider.

He 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, 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 and lead author of the study, said 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 about 10 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.

But she added: “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.” 

World’s most invasive species

The study sets out how the noble false widow spider Steatoda nobilis, which originated in  Madeira and the Canary Islands, now has the potential to become one of the world’s most invasive species of spider.

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

Scientists have ruled out climate change as the likely cause of their expansion but have suggested a new genetic mutation within the species may have made noble false widows more adaptable to new environments.

In addition, the species has benefited from an ever-increasing globalised economy, hitchhiking in containers and crates around the globe.

But NUI Galway says that in parts of Ireland and Britain, it has become one of the most common species of spiders found in urban habitats.

Significant patient morbidity

Professor Derek O’Keeffe, professor of Medical Device Technology at NUI Galway said the innovative research clearly demonstrates that noble false widow spider bites may result in significant patient morbidity that requires hospital care.

He said: “This is important, as previously we only had anecdotal evidence of its potential harms in victims and therefore this new evidence will allow the updating of clinical guidelines and protocols.

“These findings demonstrate the key importance of interdisciplinary collaboration between scientists and clinicians to improve patient care.” 

The team is encouraging members of the public to email them at [e-mail] if they think they may have been bitten.