DRINKING WATER -- PARASITES
Drinking water Bacteria and Viruses
EFFECTIVENESS OF WATER TREATMENT PROCESSES ON PARASITES
Acanthamoeba
Several factors, including pH, temperature, and biological and biochemical demands that influence the growth of
amoebas also influence the amoebicidal effects of chlorine and other disinfectants. Scattered reports based on
experimental laboratory data suggest that Acanthamoeba spp. are more resistant to chlorine than Naegleria spp.
Isolated reports of resistance of A. culbertsoni to high levels (40 mg/L) of chlorine exist; however, other reports indicate
that chlorine levels of 1.25 mg/L chlorine is enough to kill Acanthamoeba, including A. culbertsoni. Of the four
disinfectants used, deciquam 222 (a quarternary ammonium compound) was found to be the most effective amoebicide,
followed by chlorine, chlorine dioxide, and ozone. Another compound, Baquacil (a 20 percent solution of
polyhexamethylene biguanide [PHMB]), used in the disinfection of swimming pools in New Zealand, has been found to
be a good amoebicidal agent. Purified PHMB is now being used therapeutically in AK cases.
Ascaris (protozoa)
Effective coagulation and filtration processes remove Ascaris ova. Chlorine and chloramine disinfectants are ineffective
against Ascaris ova. Exposure to UV light early in embryonation destroys the developing embryo. Conventional sewage
treatment processes are not effective in destroying ova. Ova need to be retained for 10 to 12 months in septic tanks,
cesspools, or other sewage detention facilities before they are destroyed.
Balantidium coli (helminth)
The same direct microscopic examination approach used for other protozoan parasites (amoebas and flagellates), can
be used for B. coli; however, the same potential problems exist. These problems include lack of specific monoclonal-
based reagents for high specificity and recovery problems related to low organism numbers. Many species of ciliates
live in water and can be found in fecal specimens contaminated by water containing these organisms. They usually
belong to the genera Chilodon or Cyclidium and can be confused with B. coli when compared morphologically.
Blastocystis hominis (protozoa)
No information on documented waterborne outbreaks is available.
Cryptosporidium (protozoa)
Utilities should consider all surface water to be contaminated with Giardia or Cryptosporidium. Watersheds should be
managed to limit the introduction of Cryptosporidium into drinking water supplies. Continuous optimization of plant
performance for turbidity and particle removal are key monitoring parameters that should be used by utilities to signal
possible problems. Treatment conditions (e.g., sedimentation, coagulation, and filtration) should be optimized to
produce a filter effluent turbidity of 0.1 ntu or less. When filter effluent turbidity ranged between 0.1 and 0.3 ntu,
Cryptosporidium presence was as much as 90 percent (1 log) greater than when filter effluent turbidity was 0.1 ntu or
less.
Cyclospora (protozoa)
Epidemiological evidence strongly suggests water can transmit Cyclospora, especially because of the one- to two-week
sporulation time. Most reports of infection have come from predominantly coastal cities or regions. Consumption of
untreated water or reconstituted milk has led to infection. Indigenous Cyclospora infections in many countries including
the United States have been described in patients with no travel history.
Accidental ingestion of contaminated water while siphoning water from a tank or cleaning a flooded basement were
reported as possible sources of infection. Epidemiological evidence suggested that water from a rooftop reservoir was
responsible for an outbreak involving 20 individuals, most of whom were physician residents in a Chicago hospital. In
another instance, 12 of 14 British soldiers and dependents stationed in Nepal developed diarrhea. Examination of the
chlorinated drinking water, consisting of river and municipal water, at the camp demonstrated the presence of
Cyclospora oocysts.
During May and June of 1996, approximately 850 cases of cyclosporiasis were confirmed in the United States and
Canada, nearly all in areas east of the Rocky Mountains. Epidemiological investigation suggested the infections were
due to eating strawberries and raspberries. During 1997 Cyclospora outbreaks were reported in Virginia, Maryland, the
District of Columbia, and Canada. These outbreaks were associated with the consumption of raspberries and basil. In
1998 importation of G18S ribosomal RNA Guatamalan raspberries was not permitted in the United States and no cases
of cyclosporiasis were reported during that year. Canada reported some cases of Cyclospora that were associated with
imported Guatamalan raspberries. Infections have been observed in the hot and humid season.
Dracunculus medinensis (worm)
Apparently it does not occur in the U.S.??????n b
Few symptoms are seen before the skin lesion appears. When the initial blister appears, about 12 months after
infection occurs, generalized symptoms may develop, including nausea, vomiting, diarrhea, and intense itching at the
site of the lesion. Severe inflammation of the tissues surrounding the worm may result from the worm being broken
during attempts at extraction. Also, secondary bacterial infection of the lesion is common, especially when the lesion is
on the foot. Persons are often incapacitated for several months after the lesion forms in the skin. In some cases, worms
may become calcified in a joint, knee, or ankle, and lead to stiffness or a fixed joint.
Definitive diagnosis can be made by observing the worm emerging from the skin. Exposing the lesion to water and
observing the discharge of larvae confirms the diagnosis. Roentgenologic examination may be needed to reveal
calcified worms.
Traditional treatment consists of removal of the worm by systematically and slowly extracting it, a few centimeters a day.
Care must be taken to prevent breaking the worm or increased inflammation will result. Metronidazole is the drug of
choice; 250 mg is given three times a day over 10 days. The drug reduces inflammation and is said to facilitate the
removal of the worm.
Entamoeba (protozoa)
Before E. histolytica and E. dispar were distinguished, it was estimated that as much as 10 percent of the world's
population had amebiasis. In some parts of the world, pathogenic E. histolytica are commonly found. In the United
States, E. dispar is probably much more prevalent than E. histolytica, particularly among native-born residents.
Amebiasis is most commonly reported among recent immigrants, travelers, gay men, and institutionalized persons, but
many of these may be harmless E. dispar infections.
Amebiasis was common among homosexual men in the pre-AIDS era, but prevalence has probably declined in recent
years. The vast majority of amebic infections in gay men are probably E. dispar. In contrast to cryptosporidiosis,
amebiasis is not a detectably increased risk for immunocompromised individuals.
In 1989, amebiasis was reportable in 47 of the 50 states. Only a very biased subset of infections are reported; however,
surveillance data are difficult to interpret. Surveillance tallies lump E. dispar and E. histolytica infections, as they are
rarely distinguished by clinical laboratories. Many infections are never diagnosed or reported, and even reported cases
may get little or no followup by public health agencies. Absent high attack rates, even large, communitywide outbreaks
of amebiasis could escape detection.
Giardia (protozoa)
Filtration processes, including diatomaceaous earth filtration, slow sand filtration, and coagulation—filtration, when
applied appropriately, can remove Giardia cysts at levels of 99 percent or more. Chemical disinfectants, such as free
chlorine, chloramine, chlorine dioxide, and ozone are known to inactivate, when appropriate conditions of pH,
temperature, disinfectant concentration, and contact time (CT) are used. Disinfectant C x T (disinfectant concentration
multiplied by contact time) required to inactivate 99 percent of Giardia cysts range from 9 to 342. Because all surface
water is subject to contamination by Giardia cysts, a multiple-barrier approach to water treatment is the most prudent
policy. In addition to good filtration and disinfection, this multiple-barrier system also must include watershed protection
and distribution system maintenance as part of any plan designed to protect the health of the water consumer.
Gnathostoma (worms)
Does not occur in the U.S. ???????? a rare disease -- infects less 200,000 in U.S
Immature worms of Gnathostoma migrate through the cutaneous tissues in various parts of the body over a few days to
many months. Intermittent migratory swellings (creeping eruptions) that are mildly to severely painful are characteristic
of this infection. Usually, the swellings are inflamed and an elevated peripheral eosinophilia is present. Infrequently,
worms may invade the eye, pulmonary tract, central nervous system, or visceral organs. The disease produced in
infections with species other than G. spinigerum is essentially the same.
Diagnosis is usually based on the distinct clinical features of the infection and a history of eating raw or inadequately
cooked flesh of freshwater fish, chicken, snake, frog, or small mammal, or drinking water from an unprotected source.
However, definitive diagnosis can only be made by recovering the worm from the tissues and identifying it as G.
spinigerum or some other species of Gnathostoma.
Gnathostomiasis is endemic throughout Southeast Asia and in Japan, but the prevalence is highest in Thailand.
Sporadic cases have been reported in Ecuador and Argentina, and in recent years more than 200 cases have been
reported from several states in Mexico.
Isospora belli
Disinfection studies have not been carried out, but effective coagulation and filtration or slow sand
filtration should be effective.
The oocysts of coccidia can withstand exposure to various chemical and physical agents that harm most organisms.
The oocyst wall is remarkable in its ability to protect the oocyst contents. Studies indicate that sunlight for as short a
time as 4 hours and freezing below about —7° C were lethal for a relative, Eimeria zuernii, and survival was directly
proportional to relative humidity. Environmental infectivity studies using oocysts from chickens have demonstrated that
E. acervulina could be recovered from soil plots as long as 86 weeks. E. tenella and E. maxima oocysts of /. belli
disappeared from all experimental soil plots in less than a year's time. No severe infection with any of the three species
was produced after 34 weeks.
Microsporidia
Disinfection studies have not been carried out
A dozen microsporidian species infect humans. The disease and associated symptoms vary considerably, and depend
on the species organism causing the infection. The most commonly reported species are those that infect the intestinal
tract (with! diarrhea and wasting as the presenting symptoms) and ocular infections causing a keratoconjunctivitis.
Among the organisms producing these two clinical syndromes are disseminating species that can cause a myriad of
other clinical symptoms. The incubation period is not known. Diagnosis is by microscopic observation of the spore stage
collected in fecal samples, biopsies, scrapings, or body fluids. Scattered data on prevalence averages around 25
percent for chronic diarrhea patients.
Naegleria fowleri
Disinfection studies have not been carried out
N. fowleri is transmitted through the nasal passages. The trophozoites and possibly the flagellates enter the nostrils
during swimming, diving, splashing while wading, or waterskiing in lakes and other bodies of fresh water. The
trophozoites make their way into the olfactory lobes through the cribriform plate and cause an acute hemorrhagic
necrosis that destroys the olfactory bulbs and the cerebral cortex.
Most cases of PAM have occurred in children and young adults who have had a history of swimming, diving, wading,
and waterskiing in swimming pools, lakes, ponds, rivers, thermally polluted water, and hot springs. A series of PAM
cases involving 16 young persons in Czechoslovakia between August 1962 and September 1965 was traced to a
swimming pool that received heated river water treated with chlorine. Several cases of PAM in the Richmond, Va., area
were all traced to one of three lakes in that area. N. fowleri has also been isolated from the drinking water in Australia.
Schistosomes (flat worm)
Disinfection studies have not been carried out
Two methods are used to control swimmer's itch. The traditional method is to apply a molluscicide in mid-June to break
the life cycle by destroying the snail intermediate host. This type of treatment has met with mixed results and the long-
term effects of this toxin on aquatic ecosystems is a concern. A new method of control focuses on capturing and
treating the birds with an antihelmitic drug, Praziquantel. Seed-eating birds can be fed treated corn or bread.
Spirometra (tapeworm)
Disinfection studies have not been carried out
Disease in humans, sparganosis, is caused by sparganum migrating through the tissues. The cutaneous tissues in
various parts of the body are most frequently involved. The worm produces a nodule or swelling that may or may not be
painful. The lesion may disappear at one site and reappear at another days or weeks later. The most serious
complications are when the sparganum enters the brain (cerebral sparganosis) or tissues near the eye
(ocular sparganosis). The only available treatment is surgical removal of the worm.
Diagnosis is usually made by finding and identifying the sparganum in the affected tissues after surgical removal or at
necropsy. About 68 cases of sparganosis have been reported from the United States, mostly from the Southeast, but
sporadic cases have occurred throughout the country. Sparganosis occurs worldwide but is most frequently seen in
Southeast Asia.
Taenia solium (tapeworm)
Disinfection studies have not been carried out
Adequate filtration should remove this organism.
Reports of this parasite in the United States are sparse. T. solium is cosmopolitan and is most common in
underdeveloped regions where personal hygiene is poor and water is contaminated with fecal material. T. solium cases
are most common in I eastern Europe, Africa, Mexico, Central America, Asia, Spain, and Portugal, published data exist
on the length of survival of this particular parasite in the! environment. The ova of most taenids can persist for years,
depending on weather | conditions, and adult worms can reside in the intestinal tract for years.
Toxoplasma gondii
T. gondii oocysts are highly resistant to environmental influences and survive freezing and drying. They are also
resistant to ammonia, chlorine, and commonly used disinfectants, including formalin. They are killed by heat
(70° C) but will survive for 30 minutes at 56° C. They are killed by 0.30 KgY gamma irradiation. Irradiation may be a
practical way of decontaminating fruits and vegetables contaminated with oocysts.
Human beings and other animals become infected primarily by ingesting food oil water contaminated with oocysts or by
ingesting infective animal tissues that contain I tissue cysts of T. gondii. During pregnancy of infected hosts, T. gondii
can multiply inl the placenta and spread to fetal tissues. Although such transplacental infection canj occur during any
stage of gestation, the fetus is affected most severely when pregnant female becomes infected during the first half of
gestation. Soil contaminated by feral cats is probably a greater risk than soil contaminated I by cats housed indoors. T.
gondii infection is higher in feral cats than in domestic cats because they hunt birds and small mammals in which a
sylvatic cycle of T. gondii is | found.
Trichuris trichiura (whipworm)
Effective coagulation and filtration processes remove ova.
Because the embryo develops into the infective larva outside the host, Trichuris ova are well-suited to prolonged
survival in the environment. Embryo development and survival in the environment depend on aerobic metabolism;
however, these ova can also survive in anaerobic conditions. Under conditions of ambient temperature (22 to 35° C),
moisture, shade from ultraviolet (UV) light and oxygen, Trichuris ova take 11 to 38 days to become infective. At 15° C,
Trichuris ova may take four to six months to develop to infectivity. Infective ova of Trichuris can remain viable for
several months, with about 20 percent viable for more than 18 months. However, exposure for short periods of time
(hours) to temperatures above 37° C will kill developing embryos.