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Plague is a highly infectious disease caused by bacteria. Plague is primarily a disease of rodents, but humans and their pets (dogs and especially cats) can also become infected. Infection can occur when humans or pets live in or visit areas where wild rodents are naturally infected or if the disease is transferred to domestic rats that live closely with people.

The Vector Control Program routinely collects fleas and blood samples from squirrels in our local mountains and campgrounds. If tests come back positive for plague, park rangers are notified, squirrel burrows are treated for fleas, and warning signs are posted to inform the public on how to avoid fleas and protect themselves and their pets from this serious disease.

Plague Symptoms 
In humans, the initial symptoms of plague include chills, fever, headache, muscle aches, weakness and most commonly swollen and tender lymph nodes (called buboes). This stage is called the bubonic plague.  Plague symptoms usually appear 2 to 6 days after infection. Plague is treatable when found early.

An animal with plague will become very ill, may stop eating and will have a fever. Swollen lymph glands may occur, generally in the neck area. INFORM YOUR VETERINARIAN IF A PET BECOMES SICK FOLLOWING A VISIT TO A PLAGUE AREA.

Animals That Carry Plague

Do not bring fleas home with you!  Flea control products should be used on pets before taking them to a known plague location.  The most important wild rodents that can carry the disease are ground squirrels, chipmunks, wood rats and mice. Rabbits, carnivores and wild pigs can also get plague but usually recover. Domestic animals, such as cats and rats can also carry plague and pose a direct threat to humans.


Magnified Flea with Plague Mass

Exposure To Plague- How You Get It

People can get the disease from animals in several ways. The most important routes of transmission are:                                                            

  1. Flea bites from infected rodents:  Hungry fleas will leave a sick or dead rodent to find new blood meals from humans.

  2. Direct contact with sick or dead animals:  The plague bacteria in the blood, urine or saliva of an infected animal can enter cuts and abrasions on human hands.

  3. Pet involvement: (1.) Infected rodents fleas can be brought into a home or campsite by a dog or cat.  (2.) Plague pneumonia can be transmitted by a sick cat that is coughing and sneezing.

General Precautions:

  • Avoid known plague areas
  • Avoid contact with wild animals and their fleas, especially sick or dead rodents
  • Use caution when handling a sick pet that has been in a plague area
  • Avoid face-to-face contact with sick pets or sick humans
  • Report sick or dead animals to park rangers or the Vector Control Program
  • Contact a physician immediately if you become ill within 7 days after being in a plague area 

Controlling Plague

  • State and local vector control programs monitor plague activity. Rangers, park employees are trained to watch for sick or dead rodents.            
  • Warnings will be posted by park rangers or health officials in areas where plague is found.  People should use caution when entering these areas.
  • Flea powder may be used to control fleas carrying plague. Flea powder is applied into rodent burrows (rodents get the powder in their fur after entering their burrow, killing fleas inside the burrow). This is very effective, uses a minimum of flea powder and does not harm rodents.

Plague Activity

2014 Plague Activity
DateCommunity AreaLocationSpecies
07/15//2014PalomarCamp PalomarOtospermophilus beecheyi
07/15//2014PalomarCamp PalomarOtospermophilus beecheyi
07/15//2014*PalomarCamp PalomarOtospermophilus beecheyi
07/15//2014*PalomarCamp PalomarOtospermophilus beecheyi
07/15//2014Palomar Cedar Grove CampgroundOtospermophilus beecheyi
07/15//2014*PalomarCedar Grove CampgroundOtospermophilus beecheyi
07/15//2014PalomarFry Creek CampgroundOtospermophilus beecheyi
07/15//2014PalomarDoane Valley CampgroundOtospermophilus beecheyi
07/15//2014PalomarDoane Valley CampgroundOtospermophilus beecheyi
06/30/2014PalomarCamp PalomarOtospermophilus beecheyi
06/30/2014PalomarCamp PalomarOtospermophilus beecheyi

 *Denotes the re-capture of a previously tested positive squirrel. 


2013 Plague Activity
DateCommunity AreaLocationSpecies
09/17/2013*PalomarCedar Grove CampgroundOtospermophilus beecheyi
09/17/2013Palomar  Cedar Grove CampgroundOtospermophilus beecheyi
09/17/2013Palomar Cedar Grove Campground Otospermophilus beecheyi
06/13/2013PalomarFry CreekOtospermophilus beecheyi
06/12/2013PalomarDoane CampgroundOtospermophilus beecheyi
06/12/2013PalomarCedar Grove CampgroundOtospermophilus beecheyi
06/12/2013PalomarCedar Grove CampgroundOtospermophilus beecheyi
05/09/2013PalomarCedar Grove CampgroundOtospermophilus beecheyi

*Denotes the re-capture of a previously tested positive squirrel.


2012 Plague Activity
DateCommunity AreaLocationSpecies
07/26/2012PalomarDoane CampgroundOtospermophilus beecheyi
07/25/2012PalomarCedar Grove CampgroundOtospermophilus beecheyi
07/25/2012PalomarCedar Grove CampgroundOtospermophilus beecheyi
04/12/2012PalomarCedar Grove CampgroundOtospermophilus beecheyi


2010 Plague Activity
DateCommunity AreaLocationSpecies
05/06/2010PalomarDoane CampgroundOtospermophilus beecheyi


2009 Plague Activity
DateCommunity AreaLocationSpecies
06/11/2009PalomarDoane CampgroundOtospermophilus beecheyi 
06/11/2009PalomarDoane Campground Otospermophilus beecheyi 
04/02/2009 PalomarDoane Campground Otospermophilus beecheyi


2008 Plague Activity
DateCommunity AreaLocationSpecies
 10/22/2008 PalomarDoane Campground Otospermophilus beecheyi 
 10/22/2008Palomar Doane Campground Otospermophilus beecheyi 
 09/24/2008Palomar Doane CampgroundOtospermophilus beecheyi 
 08/04/2008 PalomarCedar Grove CampgroundOtospermophilus beecheyi 
07/18/2008PalomarDoane CampgroundOtospermophilus beecheyi
07/15/2008PalomarDoane School Camp / Palomar Mtn.Otospermophilus beecheyi
06/26/2008PalomarDoane CampgroundOtospermophilus beecheyi
 06/05/2008 PalomarDoane CampgroundOtospermophilus beecheyi
06/05/2008 PalomarDoane CampgroundOtospermophilus beecheyi

Plague Activity Map (2008 through 2011)

For More Information On 
Plague Or Other Vectors Contact: 
(858) 694-2888
 Vector Control Program