Download Заголовок слайда отсутствует

Diarrhea, caused by
waterborne Entamoeba,
Giardia, Cryptosporidium
and Cyclospora
Paul R. Earl
Facultad de Ciencias Biológicas
Universidad Autónoma de Nuevo León
San Nicolás, NL 66451, Mexico
These waterborne protozoa have cysts and of
course trophozoites (mobile forms). They are not
killed by the common chlorine treatment of drinking
water. Then we are concerned with water
management and drainage from the public health
point of view.
Cryptosporidium parvum is a parasite with cysts
smaller that a red blood cell of 7 microns, whereas
Cyclospora, Entamoeba histolytica and Giardia
lamblia have cysts of 10 or more microns. All 4 of
these protozoans can cause diarrhea and are
resistent to chlorination. Except for the flagellate
and the ameba, the 2 other protozoans belong to
the Order Eimeriida.
Water management.
There are 2 traditional ways of treating wastewater:
a) it is left in stabilization ponds (settling tanks) until
the solid matter it contains has settled as sediment,
and b) as activated sludge where air is blown
through the water so that microbes convert more
organic matter. In both cases, black sludge
accumulates, therefore look for a better way.
These parasitic diseases sometimes may seem
remote from the massive problem of supplying
cities with enough clean water, and sometimes
supplying the countryside with safe fertilizer.
Soil erosion is another major problem related
to water management. Silt in rivers by high
runoffs as from mountains and high
sedimentation rates leads to senescent lakes
that are eventually filled in. The diversion of
country waters to the cities by deep wells and
canalization makes the land drier, i. e.,
sometimes creates more desert. Many lakes,
dams and rivers contain overloads of sewage
(human feces) that make them a health
hazard. In Spanish this drainage is called
aguas negras. Enormous deep green algal
blooms result from intense sunlight.
The final problem is that as human populations
rise, and water resources remain constant so
that recycling is encouraged. Will the French
drink up the Seine? New dams may be needed
for various population expansions. What
happens when the aquifer is empty? You wait
for rain. Eventually, everyone will feel
competition for water.
Actinomycetes, microfungi and yeasts, sulfatereducing bacteria, sulfite-reducing bacteria,
iron-precipitating bacteria and finally pathogens
all contribute to the quality and taste of drinking
water. Water may best be surveyed using gas
chromatography.
Tropical countries short of water and
having very high evaporation rates may
not benefit much from sludge systems. To
successfully recycle contaminated water
may require a biofilter as used in Chile
consisting of boulders, smaller rocks,
sawdust and a 20-40 cm soil layer with
earthworms (Eisenia andreis) at 500010000 worms per m3. The water from this
system at depth 1 cm passes a UV lamp
of 30 watts per m3/sec that kills all
bacteria. This small system can be scaled
up.
In Chatham county, North Carolina,
USA, wastewater is cleaned for
reclamation and reuse using , and a
greenhouse containing. It not only
purifies water and reclaims nutrients,
but also reuses water, and therefore
RECYCLES WATER. Nutrients from
the wastewater are captured to be
used later as fertilizer for plants.
Making soil-containing filters in North Carolina.
Biodegrader at work in Colombia.
Is bottled water safe ?
Crypto by its small size is causing us to
become reeducated in clean water
technology. Look for a filter that will
remove particles that are less than or
equal to 1 micron in diameter. There are
two types of these - "absolute 1 micron"
filters and "nominal 1 micron" filters. The
absolute 1 micron filter will more
consistently remove Cryptosporidium than
a nominal filter. However, how long will a
filter last before cloging in such rigid
conditions?
Fertilization and ozonation.
In other projects with potable water, sediment
cartridges are used to catch dirt, sand,
mineral or metal particles. They are available
in 20, 10, 5 or 1 micron sizes. Lower micron
ratings mean smaller particle removal. Try 5
microns or less. Replace when the filter plugs
up or reaches the 3-4 month lifespan or
purchase a reusable cartridge. These are all
10 inch tall cartridges for standard canisters.
Flow is 3-4 gallons/minute. Material:10 inch
pleated polyester.
Cyst-forming Protozoa have eluded chlorine
as the main disinfectant of civic drinking water
for over a century. Perhaps the pathogenic
ameba Entamoeba histolytica causes
undectected low levels of infection constantly,
at least in some countries. Cryptosporidium
parvum on the other hand has scored
resounding epidemics. The most dramatic
failure of water supply protection in
Milwaukee, Wisconsin in the spring of 1993
allowed a diahrrea involving 400,000 people,
50 of whom died.
Cryptosporidium oocysts are currently found
in surface waters. Their incomplete removal by
sand filtration and their high resistance to
chlorinated disinfectants make possible
waterborne cryptosporidiosis outbreaks after
drinking treated water. Ozone is an alternative
to chlorine for final drinking water disinfection,
important as chlorine does not kill protozoan
cysts.Therapeutic and laboratory grade
ozonation systems utilizing the low frequency
(50/60Hz) corona discharge ozone production
process have dominated the field of Ultra Pure
Ozone Applications for the last 20 - 30 years.
Avoid being the victim.
Cyclospora infection can be prevented by
avoiding water or food that may be contaminated
with feces. Uncooked fruits and vegetables
should be washed thoroughly before eaten.
Always thoroughly wash hands with soap and
water before handling food, after using the toilet
or changing diapers, after handling animal stools
(feces), and after gardening or other direct
contact with soil. Do not drink water directly from
streams, lakes, springs or swimming pools. Boil
water for 1 minute at a rolling boil whenever you
are unsure of the safety of the water supply.
THE PARASITES
The taxonomy.
The Kingdom Archezoa Haeckel, 1894 contains
3 phyla one of which is Metamonada Grassé,
1952. Giardia belongs to the order
Diplomonadida Wenyon, 1926 class
Trepomonadea Cavalier-Smith, 1993 of
Metamonada. The other 3 genera of parasites
belong to Kingdom Protozoa Goldfuss, 1818.
Phylum Sporozoa Leukart, 1897 (= Apicomplexa
Levine, 1970) contains the class Coccidia
Leukart, 1879 and the order Eimeriida Léger,
1911, containing Cryptosporidium and
Cyclospora.
The sexual stage.
The key to parasite survival is of course the
resistent cyst. Giardia is a flagellate and Entamoeba
an ameba that do not have sexual cycles, and the
others are eimerians. The cyst is a life cycle stage,
not related to any sexual phase. Most Protozoa
have a haploid set of chromosomes which is to say
that they are haplonts. Upon the union of male
(microgamont) and female (macrogamonts) nuclei,
the karyosome (zygote) is doubled (2n) and
immediately reduces to half that is the haploid
number (n). The female gamont becomes the
macrogamete without division. Microgametes can
be many with 2-3 flagella.
Although the number of bodies like
merozoites may be different in stages
Type1-3, the number of chromosomes
each has is presumably the same. The
macro- and microgametes fuse to form
the karyosome (zygote) that
immediately reduces its chromosome
number as in 2n = n + n. This is zygotic
meiosis, sometimes called haploid
meiosis.
Symptoms may include intermittent
diarrhea and constipation, increased gas
(flatulence), and cramping abdominal
pain. The abdomen may be tender when
touched, and the stool may contain
mucus and blood. The person may have a
slight fever. Between attacks, symptoms
diminish to recurring cramps and loose or
very soft stools. Wasting of the body
(emaciation) and anemia are common.
Four-nucleated cyst with rounded chromatin
bodies. Nothing more CLASSIC is found.
Giardia lamblia is the most common of
these parasites generally, although E.
histolytica is more frequent in some areas.
These 2 important parasites are omnipresent in
many countries, and much more frequent than
Cryptosporidium parvum and Cyclospora that
occur episodically.
A small fraction of Giardia cysts can withstand a
single freeze-thaw cycle. They can survive for
2-3 months in water temperatures of less than
10/ C, and at 21/ C, cysts have remained viable
for almost one month. Cysts are killed in 10
minutes at a water temperature of 54 C.
Giardia is a common protozoan parasite of farm
animals, especially calves and lambs. Dogs are often
found infected; cats less frequently, yet pets are not a
transmission problem. Wild animals are often infected.
Each year 4,600 persons with giardiasis are estimated
to be hospitalized in the US. Hospitalized cases are
primarily children under 5 years of age, and
dehydration is the most frequent codiagnosis.
A potentially serious consequence is nutritional
insufficiency which may result in impaired growth and
development of infants and children. Other reported
associations with giardiasis in children include
malabsorption of iron, allergic reactions, inflamation
of the synovial membranes of major joints.
Two trophozoites of Giardia lamblia,
one of which is in metaphase of mitosis,
having about 14 chromosomes.
Cryptosporidium parvum Tyzzer, 1911.
Cryptosporidium belong to a group of protozoa
occurring in the dung of farm animals which can be
washed from agricultural land into nearby rivers. It is
normally spread through contaminated water or
contact with an infected person - but unpasteurised
milk and offal can also carry cysts.
Cryptosporidiosis is most common in children
between 1 and 5 years and is often associated with
farm visits, as when a child has cuddled a lamb. The
disease is known in cattle, sheep, goats, dogs, cats
and in birds. Outbreaks also occur in children's
nurseries. Larger outbreaks are linked to
contaminated water in both the water supply and in
swimming pools.
Cyclospora Ortega, Gilman & Sterling, 1994
has 8-10 micron diameter about twice that of
Cryptosporidium parvum. Oocysts can be
identified in fecal samples by examination of wet
mounts under phase microscopy, use of modified
acid-fast stains (oocysts are variably acid-fast),
or demonstration of autofluorescence with UV
epifluorescence microscopy. However, these
procedures are not routine for most clinical
laboratories, and confirmation of the diagnosis
by an experienced reference laboratory is
recommended.
Cyst of Cyclospora
Although DNA sequencing as in the polymerase
chain reaction (PCR) is available for both
Cyclospora and Cryptosporidium, it is uncommon
and likely limited to reference laboratories. If a
laboratory has a fluorescent microscope,
autofluorescence as in green protein will prove very
useful, even though ancient staining techniques also
serve for identifying any sporozoans.
Demonstration of sporulation provides definitive
evidence for the diagnosis. Infection with Cyclospora
can be treated with a 7-day course of oral
trimethoprim (TMP)-sulfamethoxazole (SMX) (for
adults, TMP 160 mg plus SMX 800 mg twice daily;
for children, TMP 5 mg/kg plus SMX 25 mg/kg twice
daily).
Comparison of the 2 eimerian parasites