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 Leptospirosis or Weil's disease
Sometimes they transmit disease indirectly, for
example, fleas biting first an infected rat, then a
Human cases of this disease are seldom fatal. The
person. Following are some of the more important
disease organisms are spread from rat urine into water
diseases associated with rats:
or food, and enter humans through mucous membranes
or minute cuts and abrasions of the skin.
Plague
The "Great Plague" of London killed half of the
Trichinosis
city's population. The "Black Death" of Europe lasted
Trichinosis results from a nematode, or tiny
50 years in the 14th Century and killed 25 million
roundworm, that invades intestines and muscle tissue.
people. In the first quarter of this century, an
Both people and rats get the disease from eating raw
estimated 11 million people died in Asia from plague.
or undercooked pork infected with the nematode. Rats
The disease is transmitted primarily to man by the
help spread trichinosis when hogs eat food or garbage
oriental rat flea. The flea bites an infected rat, and
contaminated with infested rat droppings.
then, feeding on a human, inoculates them with the
bacteria that cause the disease.
About Rabies - Never
Although no major urban outbreak of plague has
Rats have never been found to be infected with
occurred since 1924, this is not a disease of the past.
rabies in nature. Rabies transmission from rats to
A reservoir of plague exists in some populations of
humans has never been documented in the United
wild rodents in several Western states. Humans
States. The U.S. Public Health Service recommends
contacting these rodents could contract the disease. As
against anti-rabies treatments in the case of rat or
suburbia expands into undeveloped areas, wild rodents
mouse bites.
can transmit the disease to urban rats. There is a
danger that an outbreak of urban plague can occur in
the United States.
KINDS OF RATS
Murine Typhus Fever
In the United States the two most important pest
Murine typhus occurs in California and in
rats are the Norway rat (Rattus norvegicus) and the
southeastern and Gulf Coast states. It is a relatively
roof rat (Rattus rattus). The Norway rat is also called
mild disease in humans. As with plague, murine
the brown rat, house rat, sewer rat, and wharf rat. The
typhus is transmitted from rats to humans by a rat flea.
Norway rat is generally considered the most important
In this case, however, the disease organism enters the
rat in the U.S. It is found in every state.
bloodstream when feces of infected fleas are scratched
The roof rat is also called the black rat, ship rat,
into a flea-bite wound.
and Alexandrine rat. Roof rats are found primarily in
coastal areas of the United States, including California,
Rat-Bite Fever
Washington, and Oregon, the Southeast and Middle
Rats bite thousands of people each year; most
Atlantic States, and the Gulf States.
bites occur in inner cities. [In some cases victims,
The two species look much alike but there are
particularly infants and bed-confined elderly, are bitten
noticeable differences. In general: (see field
in the face while sleeping.] A small percentage of
identification chart)
those bitten develop rat-bite fever. The bacteria that
A Norway rat looks sturdier than the
causes the disease is carried in the teeth and gums of
roof rat; the roof rat is sleeker.
many rats. Although the disease exhibits mild
A mature Norway rat is 25 percent
symptoms similar to flu in most cases, it can be fatal.
longer than a roof rat, and weighs twice
It is of particular risk to infants.
as much.
A Norway rat's tail is shorter than the
length of its head and body combined;
Salmonella Food Poisoning
a roof rat's tail is longer than its head
Rats frequent sewers, rotting garbage, cesspools,
and similar sites where Salmonella bacteria thrive. The
and body;
A Norway rat's ears are small, covered
bacteria also thrive in the intestinal tracts of rats. If
with short hairs, and cannot be pulled
infected rats travel to stored food, or dishes and
over the eyes; a roof rat's ears are
silverware, or food preparation surfaces, their
droppings can transmit Salmonella food poisoning to
large, nearly hairless, and can be pulled
over the eyes.
humans.
Module Three Chapter 2, Pg 2
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