Environmental Engineering Reference
In-Depth Information
Typhoid bacilli may be found in the feces and urine of cases and carri-
ers. Typhoid immunization is reported to be about 70 to 90 percent effective,
depending on degree of exposure,
8
,
9
and then only against small infectious doses.
Routine typhoid vaccination is indicated only when a person is in intimate con-
tact with a known carrier or travels in areas where there is a recognized risk
of exposure, but precautions should still be taken with water and food. Routine
vaccination of sewage sanitation workers is warranted only in areas with endemic
typhoid fever. There is no reason to use typhoid vaccine for persons in areas of
natural disaster such as floods or for persons attending rural summer camps.
8
,
9
There are currently two typhoid vaccines available in the United States, an oral
live-attenuated vaccine (Vivotif Berna) and an injected capsular polysaccharide
vaccine (Typhim Vi). Both vaccines have been shown to protect 50 to 80 percent
of recipients. Boosters are required, every five years for the oral vaccine and
every two years for the injected form.
10
Before choosing to forgo typhoid vacci-
nation, travelers should be advised that a marked increase in antibiotic resistance
by
S. typhi
has been documented in recent years and that the geographic location
of the more resistant strains may be related to the frequency of antibiotic use.
11
Cholera vaccine is not available in the United States. It has not been rec-
ommended for travelers because of the brief and incomplete immunity it offers.
Currently, this issue is somewhat controversial; however, it is generally agreed
that effective deployment of vaccines for cholera should take place in areas or
countries of high endemic level of cholera, and 50 to 70 percent of the suscepti-
ble population must be immunized. Antibiotic resistance to tetracycline has been
found in some
V. cholerae
isolates. However, widespread acquisition of antibiotic
resistance has not been reported as in the case of
S. typhi
. No cholera vaccination
requirements exist for entry or exit of any country. Yellow fever vaccine offers
protection for at least 10 years and possibly up to 35 years. A certificate of vac-
cination is required for entry into some countries.
10
The WHO is recommending
the use of five antihelminthic agents — albendazole, mebendazole, diethylcarba-
mazine, ivermectin, and praziquantel — to control parasitic worm infections that
affect over 25 percent of the world's population.
12
Good housing, sanitation (water, sewerage, solid wastes, and vermin control),
and personal hygiene provide long-term protection against many diseases whereas
an immunization protects only against a specific disease and must be repeated to
remain effective. Individual and community performance, environmental hygiene,
and economic levels are also improved,
13
in addition to the quality of life. This is
not to minimize the importance of immunization against the childhood diseases
and epidemic control where indicated.
Typical Epidemic Control
Outbreaks of illnesses such as influenza, measles, dysentery, poliomyelitis, and
other diseases can still occur. At such times, the people become apprehensive
and look to the health department for guidance, assurance, and information to
calm their fears.
