I have a building where there was a similar problem.
I had someone come in and seal up the complaining apartments behind the stove, sink, dishwasher, heat risers, molding gaps, etc.. he also poisoned and used steel wool (not brillo). In addition, every basement hole was filled with poison and then sealed; all garbage and open food MUST be removed ASAP from the areas.... In addition to this, I purchased the sonic plugins for several apartments.. they did work very well.

You will get a foul odor for several days, but that is a good thing, because the smell and the mice will soon be gone!

note: many people state that the plug-ins do not work well, it is because the mice get used to the sound. The frequency must be changed every few months for them to remain effective.

Smaller note: Typically and as a rule of thumb, if you have mice, you do not have rats and visa versa… for some reason they do not like to cohabitate. If you do have both, there is a greater problem.

~AR

Actually, the reason they don't cohabitate is that rats eat mice.

I've always found that the best weapon against both is the oldest weapon against both: If there's a cat around, you do not get mice or rats. You may find one out in the open early on -- likely with its head bitten off -- and after all, all the other rodents get the message. Works every time.

A cat lives in the unit where there is a problem-what's up with that? I can't get a cat, I'm allergic. How can the exterminator get to the holes behind cabinetry? Ripping it out and renovating is not an option for me. They have done all the things you mentioned except for the plug ins. I guess I will try that. And maybe we need to find a new exterminator to get a fresh pair of eyes on the problem?

Another pair of eyes is always a good idea. Very odd that the cat you mention apparently doesn't go after the mice -- maybe it's old, blind, etc.? That happens.

Hypoallergenic cats exist, but they're very expensive so that's not option for most people. Less expensive are cat-allergy medications, but unless one is a dyed-in-the-wool cat-lover (definitely not me, by the way), that's an awful lot of trouble, expense and dedication.

The most reassuring thing I can offer is that the board is facing a warrant of habitability issue, not to mention most likely NYC Dept. of Health issues, and is responsible for fixing the problem. If the only way to fix it is to rip out and replace the walls, then that's at the board's expense.

If your board is balky, get in touch with Dept. of Health. Rats and mice have spread pandemics, and NYC history is full of localized outbreaks related to rodents. This is a serious issue that goes beyond one building, and the board has to step up its game.

JB, I am on the Board and the other members are aware of the situation. If I present them with ripping my kitchen cabinets out to get to the walls and fill all holes, I'm wondering who pays for what? There's the demo work, then the patching and then I would need carcasses and cabinets for the cabinets, new sink, washing machine, countertops etc. We're looking at a $10K cost here for new half a kitchen and I think that would be my expense. I just don't have that kind of $$ to take that expense on. And a cat is not an option--my dog would not like that one bit.

"The unit below me will not let our exterminator in" - If the unit below you has mice, they need to have an exterminator visit!

Pest control is the problem of the whole co-op, and shareholders who refuse to cooperate are in the wrong. Check your by-laws, but I'm willing to bet the co-op board has the right to force them to let an exterminator in.