IMPORTANCE TO MAN
a. Many of the native North American rodents are of considerable economic
importance to man--some for their pelts and others because of the damage they cause.
However, the three imported, commensal rodents are far more destructive to man and
his property than are the native rodents. One or more of these three are found almost
everywhere that man dwells.
b. The Armed Forces are concerned with rodents primarily because these
animals act as reservoirs of some of the most serious diseases affecting man.
Nevertheless, the economic aspects of a rodent population are also of considerable
significance. The monetary losses encountered through consumption and
contamination of foodstuff and through damage to buildings and property amount to
millions of dollars annually.
c. Many other rodents are of military importance. Noteworthy of these are the
Polynesian Rat (Rattus exulans) found from Southeast Asia to New Zealand and Hawaii
and the lesser bandicoot (Bandicota bengalensis) found throughout Southern Asia.
MEDICAL IMPORTANCE--RODENT-BORNE DISEASES OF PRIME
a. Plague. Plague ranks first in importance among rodent-borne diseases.
Essentially a disease of rats and other wild rodents, this bacterial disease may be
transmitted to man by a flea, which previously has fed on an infected rodent. The
bacteria (Yersinia pestis) enters the human body when the flea attempts to feed. Cases
originating in this way are termed bubonic plague. Cases or even epidemics of
pneumonic plague may develop from a bubonic case by means of the respiratory
discharges of the victim and without any relationship to rodents. The explosive
epidemics of plague are of the pneumonic type. This was the historic "Black Death"
which killed millions of people in Europe, Asia, and Africa, following the sweep across
Europe and into commerce of an exploding population of rats. No serious outbreaks of
human plague have occurred in the United States (US) recently; however, sporadic
cases of sylvatic plague (coming from the reservoir of wild rodents) do occur. This
reservoir of plague exists without contact with domestic rodents, and with man entering
the cycle only occasionally. However, the danger is always present that wild rodent
fleas will infect domestic vertebrate hosts, and thence that the fleas from these will
infect man with the plague bacteria. The disease is usually fatal to the fleas and the
rodent, as it is to man when treatment is delayed. Vaccines have been developed and
have been used extensively to protect troops in plague areas.
b. Endemic or Murine Typhus. This rickettsial disease also is transmitted to
man by the feces of an infected rat flea and occasionally by inhalation of dust containing
infected particles of flea feces. Murine typhus is endemic throughout the Southwestern
and Gulf Coast States in the US, through southern Texas, and west into California. It
has been reported also from Hawaii, Mexico, parts of South America, Southern and