A bite from a noble false widow can result in hospitalisation, study says

27 May 2021

Female noble false widow. Image: Dr John Dunbar/Venom Systems Lab, NUI Galway

NUI Galway researchers are studying the noble false widow spider, an invasive species to Ireland, to better understand the potential impact of its bite.

Scientists at NUI Galway have confirmed that a bite from the noble false widow spider could land you in hospital.

In a new study published to Clinical Toxicology, they said that some people who have been bitten by the spider experience symptoms similar to those who have been bitten by black widow spiders. In some severe cases, hospitalisation may be required.

The noble false widow, or Steatoda nobilis, is a relative newcomer to Irish shores but has become one of the most common species of spider found around urban habitats in parts of Ireland and the UK.

It is originally from the Canary Islands and Madeira, and has now spread to Europe, north Africa, west Asia and parts of North and South America.

“Two decades ago, this species was almost unknown in Ireland, the UK or in continental Europe,” said Dr Michel Dugon, head of the Venom Systems Lab at NUI Galway.

“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.”

‘We need to continue to closely monitor bites’

A study last year from the NUI Galway team found that the noble false widow produces a range of toxins that are also found in black widow venom.

They said that while most recorded bites from false widows were mild – causing pain, swelling or stiffness – the spider could deliver a more toxic bite than we once thought.

Bites are becoming more prevalent with the increase in false widow spiders around homes in Ireland, and the latest study from NUI Galway suggests that these could have public health implications in serious cases.

The research team has established a DNA database to allow clinicians dealing with bite cases to confirm the species identity using genetic analysis, which could help with treatment.

“This species is increasing its range and population density, which will undoubtedly lead to an increase in bites,” said Dr John Dunbar, postdoctoral researcher at the Venom Systems Lab and lead author of the study.

“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 researchers have been compiling confirmed cases of noble false widow bites. They said that almost all bites occurred in and around the home, with 88pc occurring either when a person was asleep or when the spider was trapped in clothing.

Aiste Vitkauskaite, an MSc student in toxicology at NUI Galway who was joint lead of the study, said around 10 species of Irish spiders have fangs large enough to bite human skin, but in the past five years the team has not heard reports of people being bitten by the native species.

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

Sarah Harford was sub-editor of Silicon Republic