As the rains fall harder and the water table rises, a dark, disturbing presence emerges from Dublin’s drains. Scrabbling, clawing and gnawing, rats are scurrying towards us.
But fear not: if you fall victim to an infestation in the capital, help is at hand from the Health Service Executive’s Pest Control Team.
“We would we get between 16,000 and 17,000 callouts a year in Dublin city and county, it’s a very busy service,” says Catriona Stack, principal environmental health officer.“We get complaints about infestations in dwellings, vacant houses, derelict houses and sites, people complaining about their neighbours – that vermin have come from a neighbouring property into their property – rats on green space, rats coming from construction activity.
“Also, internally within the HSE we get referrals from social workers in relation to vulnerable persons who might be hoarding materials, and we would work holistically with the HSE and other services to try and support the individual back to a safe way of living.”
After receiving the initial call, members of the pest control team will visit the location of the suspected infestation.
“The pest control staff are very highly trained. There’s a professional qualification which is overseen by the Department of Agriculture, Food and the Marine, and we do follow guidelines by CRRU – the Campaign for Responsible Rodenticide Use. One of their main focuses is ensuring we don’t end up with secondary poisoning of our wildlife [with] the rodenticide we use.”
If rodenticide is deemed to be required in a particular location, it is put in locked boxes that residents are instructed not to move.
“If after 35 days the problem is not going away, we carry out another survey to see if we missed something. We don’t lay bait and just leave it. It’s only left for the amount of time we’re doing our treatment, then it’s removed.”
Dealing with the infestation that triggered the call is just the start. What’s more important, Stack says, is figuring out why rats inhabit an area, and ensuring they don’t come back.
“If you attract them, they will come,” she warns. “If they can get access into your home, that’s what they will do. If they can find food and water when they’re in your home, they’ll happily set up residence.”
First, try to eliminate sources of water and food outside your home, she says.
“Rats are different to mice. Mice will get moisture from food they eat, but rats need to consume water, so don’t give them a water source. Make sure you don’t have any stagnant water outside, no defective pipes that could be leaking water.”
Even a tiny puddle could be enough for them to drink at, she says. “If you’ve got concrete outside and it’s wearing a bit and there’s pooling of water that’s sitting for a while, they like that.”
Look up at the facade of your home and at any trees and foliage growing near it – keep them trimmed back, because rats can climb
— Catriona Stack, principal environmental health officer, HSE
Consider what food sources you might be unwittingly offering. If you have pets, don’t leave their food bowls outside at night, and clean up any spillages from bird feeders, Stack says. But it’s not just animal feed they like – rats will eat almost anything.
“Most people would know about the risk of refuse not being stored hygienically prior to collection, but one thing I think people don’t think about is animal waste. If you have a dog or a cat, rats will actually eat their waste.”
If you have a garden, consider whether you might have made it a rat haven by leaving building materials or other debris around that they could use for shelter. “Also, any drains you have in the garden – if the lids are defective have them replaced, because rats will rise from the sewers.”
Above all, don’t invite them into your home.
“There are lots of older buildings in Dublin, and if entrance doors aren’t flush with the ground, vermin will be able to get through even very small spaces into your home. If you notice any sort of gap, fit the likes of a bristle strip at the bottom of the door.
“Fill gaps around waste pipes leading outside from bathrooms or from the kitchen. Use steel wool in gaps, because rats don’t like that. If their teeth go near it, it aggravates them, so things like scouring pads, you can use those around any gaps or holes and then finish that off with mortar and seal it off that way. They can eat through some expanding foams, so if you do use expanding foam it’s really important to put steel wool in first.”
[ Direct provision residents in Sligo complain of ‘rat infestation’Opens in new window ]
It’s not just pipes coming out at ground level you need to worry about, Stack says. “Look up at the facade of your home and at any trees and foliage growing near it – keep them trimmed back, because rats can climb. They climb up trees and get into the eaves of your home that way, believe it or not.”
If you follow these rules, you should be able to keep your home free from invaders, she says. “If a rat does wander into your space and it’s not finding the things it needs to live – doesn’t have the water, doesn’t have the food, doesn’t have harbourage, it will move on to another place.”
There aren’t any times of year rats are more prevalent in Dublin, but excessive rain can drive them above ground, Stack says. “If there is a lot of rain, if the water is rising in the sewers, that will bring them out.”
Stack has a practical, analytic attitude towards the unpopular rodents. “I’m not terribly squeamish, I have to say – I’d be more thinking, ‘How did that rat get here?’ and the investigation hat is on. To be honest with you, leave your squeamish feelings outside the door when it comes to doing the job.”
However, that doesn’t mean she lacks compassion.
“Rats can carry diseases and cause damage, but I think the main problem is the great distress they cause to people. Your home is your sanctuary. You want peace in your home. If you have vermin running around your home, and you can hear them at night, when you’re lying in bed, it really is extremely distressful.”
Rats Stats
While it isn’t possible to quantify the number of rats in the country, estimates put the national population at about 10 million, with about 4 million of them living in Dublin.
The HSE service dealt with 16,921 callouts in 2022 and 16,223 in 2023. The service is available to householders in Dublin city and county only, with infestations outside of the capital dealt with by private companies or, in some cases, local authorities.
While numbers of complaints in relation to rats have remained reasonably stable in recent years, Dublin’s local authorities reported significantly higher rat prevalence during the strict lockdown phases of the Covid pandemic, when footfall was low and “rats became much braver”, according to Dublin City Council.
Uisce Éireann says it carries out repairs as required to the public sewer network, but has “had no evidence of a significant increase in rodent issues associated with public sewers recently”.
There are further issues to consider if afflicted with these animals also. Rats spread zoonotic diseases – ailments that can be transmitted to humans – including Leptospirosis, also called Weil’s disease, and salmonellosis. They also carry fleas and ticks, which in turn can spread disease.
Their teeth grow constantly, requiring them to gnaw upon various objects, which can cause structural damage, and obvious dangers if they chew through cables.
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