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Date Posted: 16:01:11 10/17/99 Sun
Author: clover
Subject: Re: purifying water...page 4
In reply to: clover 's message, "purifying water" on 18:14:46 10/15/99 Fri

Medical Treatment

Three drugs are available in the United States to treat giardiasis:
quinacrine (Atabrine*), metronidazole (Flagyl*), and furazolidone
(Furoxone*). All are prescription drugs. In a recent review of drug trials
in which the efficacies of these drugs were compared, quinacrine produced
a cure in 93% of 129 patients, metronidazole cured 92% of 219, and
furazolidone cured 84% of 150 patients (4). Quinacrine is generally the
least expensive of the anti-Giardia medications but it often causes
vomiting in children
younger than 5 years old. Although the treatment of giardiasis is not an
FDA-approved indication for metronidazole, the drug is commonly used for
this purpose. Furazolidone is the least effective of the three drugs, but
is the only anti-Giardia medicatio n that comes as a liquid preparation,
which makes it easier to deliver the exact dose to small children and
makes it the most convenient dosage form for children who have difficulty
taking pills. Cases of chronic giardiasis refractory to repeated courses
of therapy have been noted, one of which responded to combined quinacrine
and metronidazole treatment (5).

(*) Use of trade names is for purposes of identification only.

Etiology and Epidemiology

Giardiasis occurs worldwide. In the United States, Giardia is the parasite
most commonly identified in stool specimens submitted to state
laboratories for parasitologic examination. From 1977 through 1979,
approximately 4% of 1 million stool specimens sub mitted to state
laboratories were positive for Giardia (6). Other surveys have
demonstrated Giardia prevalence rates ranging from 1 to 20% depending on
the location and ages of persons studied. Giardiasis ranks among the top
20 infectious diseases that ca use the greatest morbidity in Africa, Asia,
and Latin America (7); it has been estimated that about 2 million
infections occur per year in these regions (8).

People who are at highest risk for acquiring a Giardia infection in the
United States may be placed into five major categories:

1) People in cities whose drinking water originates from streams or rivers
and whose water treatment process does not include filtration, or
filtration is ineffective because of malfunctioning equipment. 2)
Hikers/campers/outdoorspeople. 3) International travelers 4) Children who
attend day-care centers, day-care center staff, and parents and siblings
of children infected in day-care centers. 5) Homosexual men.

People in categories 1, 2, and 3 have in common the same general source of
infections, i.e., they acquire Giardia from fecally contaminated drinking
water. The city resident usually becomes infected because the municipal
water treatment process does not include a filter that is necessary to
physically remove the parasite from the water. The number of people in the
United States at risk (i.e., the number who receive municipal drinking
water from unfiltered surface water) is estimated to be 20 million. International travelers may also acquire the parasite from improperly treated
municipal waters in cities or villages in other parts of the world,
particularly in developing countries. In Eurasia, only travelers to
Leningrad appear to be at increased risk. In prospective studies, 88% of
U.S. and 35% of Finnish travelers to Leningrad who had negative stool
tests for Giardia on departure to the Soviet Union developed symptoms of
giardiasis and had positive tests for Giardia after they returned home
(10,11). With
the exception of visitors to Leningrad, however, Giardia has not been
implicated as a major cause of traveler's diarrhea. The parasite has been
detected in fewer than 2% of travelers who develop diarrhea. Hikers and
campers risk infection every time they
drink untreated raw water from a stream or river.

Persons in categories 4 and 5 become exposed through more direct contact
with feces of an infected person, e.g., exposure to soiled diapers of an
infected child (day-care center-associated cases), or through direct or
indirect anal-oral sexual practices in the case of homosexual men.

Although community waterborne outbreaks of giardiasis have received the
greatest publicity in the United States during the past decade, about half
of the Giardia cases discussed with staff of the Centers for Disease
Control in the past 2 to 3 years have a
day-care center exposure as the most likely source of infection. Numerous
outbreaks of Giardia in day-care centers have been reported in recent
years. Infection rates for children in day-care center outbreaks range
>from 21 to 44% in the United states and
from 8 to 27% in Canada (12,13,14,15,16,17). The highest infection rates
are usually observed in children who wear diapers (l to 3 years of age).
In one study of 18 randomly selected day care centers in Atlanta (CDC
unpublished data), 10% of diapered children were found infected.
Transmission from this age group to older children, day-care staff, and
household contacts is also common. About 20% of parents caring for an
infected child will come infected.

It is important that local health officials and managers of water utility
companies realize that sources of Giardia infection other than municipal
drinking water exist. Armed with this knowledge, they are less likely to
make a quick (and sometimes wrong) assumption that a cluster of recently
diagnosed cases in a city is related to municipal drinking water. Of
course, drinking water must not be ruled out as a source of infection when
a larger than expected number of cases are recognized in a community, but
the possibility that the cases are associated with a day-care center
outbreak, drinking untreated stream water, or international travel should
also be entertained.

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Replies:

Re: purifying water...page 5 -- clover, 16:47:00 10/17/99 Sun