Pest control experts were contacted over 800 times by health trusts across Northern Ireland over a year, it emerged today.
The figures, for the period between April 2007 and March 2008, were obtained by the BBC under the Freedom of Information Act.
Mice were found in theatres at Craigavon Hospital and rats in Whiteabbey.
However, the trusts said they look after hundreds of buildings across the province, many of which are very old.
Maggots were found in a ward at Lagan Valley Hospital in Lisburn and cockroaches in the Causeway Hospital at Coleraine.
Mice were found in theatres at Craigavon Hospital and rats in Whiteabbey
Meanwhile, dead rats, maggots, mice and cockroaches have been found in more hospitals in the Republic.
Fourteen more hospitals have admitted they experienced pest problems over the past seven years.
Last night there were calls for stricter sanctions on hospitals that do not maintain standards when it comes to controlling pests.
Previously it was revealed how pest control companies were called in to tackle cockroach, ant and rodent infestations at 21 Health Service Executive and voluntary hospitals in the Republic.
Additional reports reveal even more alarming incidents — many detailing how rats and mice are stalking hospital corridors. Incidents included a rat in the darkroom of an X-ray department, a mouse in the light fixture of an operating theatre, and a dead mouse in a cardiac investigations unit.
The details were obtained by a Freedom of Information request which was sent out to all HSE and voluntary hospitals around the country.
Many voluntary hospitals refused to respond, but almost all of the HSE hospitals reported some type of infestation.
The scale of the problem will raise fresh concerns about the cleanliness of hospitals and the spread of disease to patients on the wards.
Between all hospitals that responded, it emerged pest control companies were called out up to 700 times by hospital authorities to deal with sightings of pests over the past seven years.
Together with routine service contract calls, the bill between all of the hospitals to control insect/rodent infestation topped €800,000.
The reports come after a hygiene audit revealed some weeks ago that patients continued to be at "significant risk" of infection at the country's hospitals.
Fine Gael Health spokesman Dr James Reilly last night branded the revelations “shocking”.
Labour Health spokeswoman Jan O'Sullivan added that it was now time to “inflict pain” on hospitals that showed a litany of pest incidents.
The urine, droppings or saliva of an infected rat can cause Hantavirus pulmonary syndrome, which is a deadly virus that causes the lungs to fill with fluid.
Fleas carried by rats and mice can also cause Murine typhus which cause a rash down the trunk of the body which may last for months.
HSE regional managers sought to defend the record of the hospitals in their areas.
A spokeswoman for HSE West insisted the reports made it “plain” the HSE was taking the problem of pest control seriously.
A HSE spokeswoman for the Dublin Mid-Leinster area said there was building work at Midland Regional Hospitals in Portlaoise and Mullingar during the period in question, and that there was “a pest control programme in place for the entire hospital complex” in both cases.
Beamount Hospital — which had more than 90 call-outs — said it was satisfied it takes all appropriate steps to control pests.