reservoirs include rabbits, field mice, and dogs. The infection is passed from generation
to generation in ticks and probably is maintained by infected tick larvae feeding upon
susceptible wild rodents. It occurs throughout most of the US during Spring and
summer, but it is most prevalent in the Middle Atlantic Seaboard States. Infection also
occurs in western Canada, western and central Mexico, Colombia, and Brazil. Infection
rates in man generally are directly proportional to the contact with infected ticks.
g. Tick-Borne Relapsing Fever. The disease is caused by a spirochete and is
transmitted through the bite or the leg joint fluid of an infected tick belonging to the
genus Ornithodoros. The vector is an infected tick, while the reservoir is the wild rodent
population. The disease is widespread throughout tropical Africa. The disease also
occurs in Spain, North Africa, Arabia, Iran, India, parts of Central Asia, as well as in
North and South America. In the US, human cases have occurred in limited localities of
13 of the Western and Central States.
h. Scrub Typhus (Tsutsugamushi Fever, Japanese River Fever, Kedani
Fever, Mite-Borne Typhus). This rickettsial disease is transmitted by the bite of
infected larval mites (chiggers) of Trombicula akamushi and related species, which vary
with locality. Transovarian transmission occurs in mites, and the infection is maintained
in nature by a mite-wild rodent-mite cycle, with man being an "accidental" host. Scrub
typhus occurs in eastern and southeastern Asia, northern Australia, the Indian
subcontinent, and adjacent islands.
i. Korean Hemorrhagic Fever. This disease occurs in troops in Korea
generally near the 38th parallel. The infectious agent is a Hantaan virus suspected of
being maintained in nature by rodents with man being an accidental host. The vector is
a trombiculid mite. Recent evidence, however, has indicated that the causative
organism may be transmitted by aerosolization during the cough of a mouse.
j. Other Diseases. The bacteria, which cause various types of food poisoning
infect rats and mice and are transmitted to man through the contamination of foodstuffs
with rodent feces and urine. Intestinal parasites, such as tapeworms, may be
transmitted similarly. Trichinosis may be acquired by rodents and then maintained at a
high incidence in the wild population through cannibalism. Hogs become infected with
trichina by eating infected rodents. Man, in turn, may acquire the disease by eating
improperly cooked pork.
The importance is fourfold:
a. Destruction or contamination of foodstuffs by rodents amounts to millions of
b. Damage to buildings and manufactured goods are estimated in the millions of
dollars per annum.