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Cher, Teacher
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I live in a middle-terraced house property and I have been

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I live in a middle-terraced house property and I have been aware of an ongoing problem with mice in the property since the beginning of February 2016. In the beginning, my partner saw a mouse upstairs which kept trying to run into the bathroom whilst it was occupied. Eventually after going downstairs and back upstairs, the mouse disappeared. I started using sachets of Sorexa D (0.005% w/w difenacoum) bait in various places that I was shown by a pest controller during a previous infestation, mainly under the kitchen sink, behind washer and drying machine, behind cooker and behind the living room sofa. After three weeks, I noticed that the bait was still being eaten by the mice and I had to sweep away the husks and replenish the bait every couple of days. Cotton wool insulation under the cooker was being disturbed each day. As I was concerned about the quality of the poison and that I was simply ‘feeding’ the mice, I bought some bromadiolone (0.005% w/w) cut wheat bait from a local store. To be honest, apart from a couple of nibbles, the mice did not seem to bother with this bait. Whenever I pulled the cooker forward, a mouse would run out.
In the last week of February, I gave up and arranged for a pest controller to visit the property. My partner made an initial telephone enquiry before making an appointment and was told “once we put our food down, they’re [the mice] gone!” I was not at home on the day the pest controller visited, but he put down Sorexa D and paste bait under the kitchen plinths, under the bath, in the living room, in the kitchen storage cupboard under the stairs and on the landing. He did not explain how the poison works or how many mice we had. He just put the bait down. He claimed that any mouse poison that the customers buy from a DIY store will not work. I checked with the vendor of the bait that I had originally purchased that it was still valid to use and they said that it was one of the best mouse baits on the market and the strength of difenacoum would be the same as that in the one the pest controller had used.
The pest controller made a second visit 10 days later and I explained that I had used bird seeds for three weeks before he came. He dismissed what I was saying and said that it would have been too weak to work. I saw him with a bucket of Sorexa D and he put more food down in all the places. A week later my partner phoned him up to explain that we still had live mice, although they were not being seen around the property, but they were heard in the wall one night and they were still eating the poison. He asked the pest controller why we still had mice after the company claiming that their poison would instantly get rid of the mice. He stated that it was not him that made this claim and the programme does not work like that. I also spoke to him and said that ‘if you’ve put that much food down and they’re still in the house, then there must be a lot of mice.’ He said ‘yes.’ I asked if we had the same mice coming into the property or if they were new ones and he said that it was the same ones that were just being very persistent. He said that if we still had mice on the third visit, he would put more food down. We were not happy with this as we were meant to have only three treatment visits after which we could block up any holes. As a result of this, we were taken off the programme and never had a third visit.
After this, I thought that the mice may be resistant to the bait and bought some whole wheat bait containing bromadiolone. I used this throughout April and the beginning of May during which time the mice consumed this bait. I think over the period of weeks about four mice died as there was a bad smell in one of the bedrooms once and twice in the bathroom. One dead one was found in the living room. In the second week of May, I decided to re-start the programme and change the diet back to Sorexa D, this time putting down much larger quantities especially in the store cupboard and under the bath hoping to reduce competition for bait. There is bait available in the other places, but it is not being eaten by the mice. I regularly replenish the bait as it is eaten, but there is no sign of the infestation dying down. I was hoping that after consuming a lethal dose of the poison and waiting an extra week, the mice would start dying. The mice only eat the bait at night. There is obviously something wrong and the programme does not seem to be working. My only other option would have been to arrange for a pest controller from the local council to visit the property for half the cost of the private pest controller, but I would anticipate that they would be just repeating what I have already done.
Have I got mutant mice in the property? Are they continuing to breed? Should I just block up any holes to stop them from getting in? Will the mice try to chew their way back through the property to get in? I am afraid of stopping the programme in case they come back in the house.
Submitted: 1 year ago.
Category: General
Expert:  Shantal-Mod replied 1 year ago.
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Expert:  Cher replied 1 year ago.

Hi, Jenny.

My name is ***** ***** I will be happy to help you.

I'm so sorry you've been experiencing this problem for so long; I can only imagine your frustration.

From your description, it is my opinion that yes, the mice are breeding and that's why you're seeing more or seeing them at all, and yes, they are mostly the same mice. If the poisons put down by you and the professional exterminator are guaranteed to kill the mice, there's not reason this shouldn't be happening, unless the poison is not strong enough. They may be immune to it, if it's been used for a long time, to get rid of mice, and they may be rejecting the wheat based one, because they don't like the taste or they can smell that it is dangerous to them.

The rodenticides that are used in the U.S. can contain different types of poisons. Some work faster than others. Here is additional information about how these rodenticides work.


The bromadiolone based poisons you're using should be causing internal hemorrhaging and killing the mice, but as you can see, at the link above, this is a lengthy process and that may be why, as you suspect, you're seeing the same mice over a period of time. As you can read in the link above, there are faster ways to kill the mice in as little as 2 days. Try to find the rodenticides that kill more quickly, in your area or ask the exterminator to get it (perhaps use a different exterminator).

Instead of cotton wool, stuffing any cracks/openings with steel wool (like 'Brillo' soap pads for washing dishes/pots, but without the soap) is more effective, as the mice can't get through the tangle of steel wool.

Make sure no food or trash is left out on counters or in the house and constantly vacuum the floors to get rid of crumbs. For foods in your cupboards, in boxes, either refrigerate them or put them in plastic ziploc bags, so the cardboard can't be chewed at to get to the food.

The most important thing now, is to find where they are coming in and if they are living in the walls, a stronger approach by an experienced exterminator who deals with mice, will be necessary.

I wish you much good luck and hope over a short period of time, you will finally be rid of this problem and take precautions so it doesn't happen again!

Please be so kind as to rate my answer with positive feedback; that is the only way I receive credit for my assistance. Thank you very much!

Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply' for clarification or additional information, if needed, and I will be glad to continue.

Warmest regards,

Customer: replied 1 year ago.

Sorry I have been offline today. Please give me some more time to read the information in the link you have provided. I believe that mice sometimes avoid traps, but they can help to get rid of some when poisons do not fully control the infestation. Is it also possible that the mice are competing for the same source of food, leaving some of them untreated? I do try to put the food in various places. What is the typical life span of a mouse if they live long enough to breed?

Expert:  Cher replied 1 year ago.

Hi again,

No problem; read the information and let me know what you think.

If you put out quite a few trays of bait (poison) in locations of great activity, they should all eat the poison.

The typical lifespan of a 'house mouse' is about 2-3 years. Technically, they can breed as early as 4 weeks of age, but this usually ends up being not good for the health of the mother and the babies; however, those that survive will continue to breed and this is part of the problem of an infestation.

You can use traps, if you like (I don't believe in them), but as you said, experienced mice learn to avoid them. I'm a pet lover and know these are not your pets, but any mode of getting rid of them involve killing and it's not a quick death.

The main thing is to survey the outside and inside of your home and determine where they're getting in, so you can seal up those areas with cement, caulking or steel wool, as I mentioned yesterday. If they're living in the walls, an experienced exterminator can place poison inside the walls and this might help dispose of them more quickly.

Please remember to rate my answer with a positive rating, so I receive credit from the site for my time and assistance. Thank you very much!

You can still ask follow up questions after you rate.

Warmest wishes,


Cher, Teacher
Category: General
Satisfied Customers: 21333
Experience: Masters Level Educator,Tutor 35+ yrs.; Author, Senior Internet Researcher, Trivia Master
Cher and 41 other General Specialists are ready to help you
Expert:  Cher replied 1 year ago.

Thank you very much for your excellent rating and most generous bonus; they are highly appreciated!

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