Biosecurity Tips:
Rodent Monitoring and Control
September, 2000
Why should I worry about
rodent monitoring and control?
Rodents contribute to the introduction and spread of
diseases in livestock and poultry production facilities.
Rodents, especially rats and mice, can spread diseases
within a facility or from an infected facility to
neighboring facilities. They can also infect incoming
animals.
Rodents also contribute to feed losses and facility
damage. A single rat can eat 20 to 40 pounds of feed
per year and contaminate up to 300 pounds of feed
with its feces and urine. Rodent infestations cost
agriculture $1 to 3 billion each year in feed losses
alone. Rats and mice will also gnaw on concrete,
glass, metal, wood, and electrical wires, causing facility
damage.
Research on one poultry ranch chronically infected with
Salmonella enteritidis revealed that most of the mice
were carriers of the bacteria. Salmonella enteritidis
was also found in mouse fetal tissue, showing that the
disease can be transmitted from parent to offspring.
Droppings from mice on this ranch were able to infect
three-week-old chicks.
Diseases spread by rodents:
 Salmonella enteritidis
 Encephalomyocarditis
 Foot and mouth disease
 Bordetellosis
 Leptospirosis
 Swine dysentery
 Transmissible gastroenteritis
 Swine erysipelas
 Toxoplasmosis
 Trichinosis
 Ectoparasites – mites and lice
So what can you do to protect your facility
from rodent infestation?


Know where the rodents are (monitoring).
Make your facility less appealing.
o Restrict rodent access to food and water.
o

Eliminate rodent entry sites to your facility.
Institute an elimination program.
Monitoring
Inspect your facility regularly for signs of rodent
infestation. These include live rodents and rodent
carcasses, gnaw marks, droppings, and burrows. Keep
records of where these were observed in your facility.
Some companies offer software programs that enable
you to input this data, as well as your facility’s floor
plan, to better identify the problem areas in your facility.
Most common rats and mice:
 Norway rat
 Roof rat
 House mouse
Facility Improvements
Rodents need three things to survive: food, water, and
shelter. Restricting access to these essentials may
make them move to another location. This may
minimize the need for elimination using traps or
poisons.
First, if possible, don’t allow rodents into the buildings
where your animals and food are housed. Rodents can
enter buildings through holes as small as ¼ inch. Be
sure that doors to the facility fit tightly, screen
ventilation openings, and inspect the outside of your
building for small holes around the foundation. Plug up
any potential rodent entry sites.
Second, reduce rodent access to water around your
facility. Fix leaky spigots and faucets and fill in any lowlying areas on your property that regularly accumulate
water.
Third, rodents find shelter in places with ample cover
(tall grasses, piles of trash, under equipment or
buildings). Cut down weeds and tall grass around your
buildings. Store scrap and trash away from your
buildings in covered containers or sealed bins. Don’t
give the rodents a place to hide!
Rodent Elimination
Facility improvements and restricting or minimizing
rodent access to food and water may control rodent
levels. However, if these measures are not successful,
elimination of the rodents may be necessary.
Rodent elimination usually comes in two forms: traps
and poisons. Traps may be humane (non-lethal) or
lethal. Release sites for rodents caught in humane
traps should be far enough from the facility to prevent
the rodent from returning.
Most traps require baits, which may attract pets or
young children. If using bait, use a covered trap
accessible only to rodents. Rodents are not attracted
to traps with spoiled or low-quality foods. Baits that are
similar to the foods rodents are used to eating are best.
To determine which bait rodents are most likely to eat,
place a small amount of several non-toxic baits one foot
apart in several locations where rodent activity was
noticed, and check the baits regularly.
Once you determine which baits the rodents prefer, you
can mix those baits with rodenticides, or rodent
poisons. When using rodenticides, precisely follow the
manufacturer’s directions and only use bait that has
been approved by the Environmental Protection
Agency (EPA). The use of chemical rodenticides is
most effective in conjunction with the environmental
controls previously discussed.
Rodenticides are available in many forms, including
powder, loose meal, pellets, wax, and extruded blocks
(large pellets). Rodents less commonly accept wax
and blocks, and may find loose meal and pellets more
palatable.
Multiple feed anticoagulants
Warfarin (Final®)
Pindone (Pival®, Pivalyn®)
Chlorophacinone (RoZol®)
Diphacinone (Ramik®, Ditrac®)
Single-feed anticoagulants
Brodifacoum (Talon®, Havoc®)
Bromadiolone (Maki®, Contrac®)
Other rodenticides
Bromethalin (Assault®, Vengeance ®, Trounce ®)
Cholecalciferol (Vitamin D3, Quintox®, Rampage®)
Zinc phosphide
Rodenticides are classified into two groups:
anticoagulants and other compounds, also called nonanticoagulants.
Anticoagulants prevent blood from clotting and damage
the blood vessels, causing the rodent to die of internal
bleeding. They are slow acting, which reduces the
ability of the rodent to associate the bait with poison
and allows time to administer the antidote to animals or
people who accidentally ingest the bait.
Anticoagulants can be classified into two categories:
multiple feed and single feed.
Multiple feed
anticoagulants require multiple feedings over several
days to produce death. Single feed anticoagulants can
result in death after a single feeding, if a sufficient
amount of bait was ingested.
Other rodenticides are useful for rapid reductions in the
rodent population. Bromethalin causes central nervous
depression and paralysis. Cholecalciferol breaks down
bone and causes high blood levels of calcium, which
disrupts body functions.
Zinc phosphide causes
convulsions, paralysis, coma, and death.
Reasons for rodenticide failure:
 Too short a period of bait exposure
 Insufficient bait
 Too few bait stations
 Too small a control area
 Poor bait choice
 Improperly placed bait stations
 Access to other food sources
 Unappealing bait
Environmental measures and the use of rodenticides
should be monitored for effectiveness. Track the
location and number of dead rodents seen on the
property or the number caught in traps. Analyze
changes over time to determine the success of your
program.
Cats
Cats are not an alternative to a rodent control program.
They are not effective against heavy infestations of
mice and may not attack rats. They may also become
a reservoir for diseases and spread diseases from the
rodents to your animals. Barn cats have been shown to
infect swine with the parasitic infection toxoplasmosis.
For more information on rodent monitoring and control, contact your
county agricultural commissioner or county cooperative extension agent.
Developed by HJ Hamlen for the California Department of Food and
Agriculture, Animal Health Branch, Emergency Programs, 1220 N Street,
Room A-107, Sacramento, CA 95814.