3. Intracellular parasite that infect vertebrates including
humans.
Belongs to Apicomplexa an obligate parasitic group of
Eukaryotes.
Species of cryptospordium parasitize specific host
tissues such as stomach, small intestine or trachea.
Cryptosporidiosis is a self limiting disease in healthy host but
represents a life threatening problem in immunocompromised
individuals for which there is no effective method.
4. The life cycle of this
parasite is complex,
showing both asexual
and sexual stages.
The persistence of
oocysts in environmental
compartment can be
influenced by their age
and chemical
disinfectants.
Under natural conditions,
fecal matter shelters
oocysts from desiccation
and increase
impermeability of the wall
to small molecules, thus
reducing their exposure
to lethal environmental
factors.
The resistance of oocysts
in a solid matrix such as
soil has become a crucial
parameter in
understanding their
transfer to lower layers.
5. Oocyst can remain viable and infectious in
water for several months at temperatures
ranging from 0 to 30c.
Boiling water can kill cryptosporidium
oocysts in less than a minute.
Exposure to sunlight had no effect on the
viability of cryptosporidium oocysts but UV
at 265nm & black light at 365nm lead to a
reduction in the no. of viable oocysts.
Oocysts resistance
6. Filtration
Methods
Membrane
Filtration
Cartridge
Filtration
Woven Acrylic Polyethersulfone
Chemical
Flocculation
Another method is elution &
its efficiency depends on
turbidity of sample, the type
of filter & the method
chosen. Oocysts trapped by
filter are eluted by detergent
solutions that break
hydrophobic interactions
b/w oocysts, sediment
particles and filter fibers.
Now centrifuge the eluate to
improve separation of
desired oocysts. Use
solutions containing
dispersive agents i.e, EDTA
increases the average % of
cryptosporidium oocysts
recovery.
7. NRC 1983 defines risk evaluation of toxic
characteristics of a chemical product and
conditions of human exposure to this
product.
Health risk evaluation relies on an
epidemiological approach.
Evaluating health risk is based on four steps:
Identifying the danger
Dose response relationship
Estimating exposure
Characterizing the risk
8.
9. Water distribution were analyzed at different
periods by sampling at least 100L.
Samples were taken from 8 reservoirs, 7
points of city drinking water network and 3
public fountains.
The exposed population was divided into 4
categories:
1
• Immunocompetent aged 5 & over low
risk of infection.
2
• Immunodepressed aged 5 & over with
severe illness linked to HIV.
3
• Immunocompetent under 5 years old
high risk of illness.
4
• Immunodepressed under 5 years old
leads to high risk of illness.
Number of persons
contaminated by HIV in
Haiti is estimated to be
about 400,000 i.e, 5% of
the total population.
Following equation was used to determine the
probability of infection:
Pr = 1- exp(-rD)
Where:
P= probability of infection of an individual exposed
to Dose D of oocysts
r= the probability of survival of oocysts in drinking
water ingested by the host
D= ingested Dose
10. Highlighted the presence of cryptosporidium
oocysts in the surface and ground water of
the coastal city of Cayes.
The watershed is divided by 3 distinct types
of Aquifers: Alluvial unconfined underground,
karastic and cracked and segmented
carbonate.
Water samples were taken from 15 sites in
September, November and December 2007,
i.e at the end of rainy season and at the
beginning of the main dry season.
6 sites were found
to be positive for
cryptosporidium
oocysyts per 100L
and elution method
used .
9 oocysts/ 100L
were obtained from
water samples from
public water supply
service of Cayes.
11. A risk factor is an
element belonging to an
individual or originating
from an environment
liable to cause an
illness, trauma or
another negative impact
on the development of
human organism.
The exposure of
consumer to
contaminated water is a
major health risk factor.
There is no control for
quality of the water of
the water distributed by
public services.
Urban areas lack basic
services for the
collection and treatment
of wastewater and solid
wastes and the removal
of excreta.
Chlorination is the only
method used to treat
raw water but it is
ineffective in
inactivating oocysts.
12. Conclusion:
Risk assessment is not a goal but there is an
decision making for risk management of oocyst
hazards and risks for human health.
