Cryptosporidium oocysts transmission in the aquatic environment of Haiti

Introduction

Liquid Effluent

• Organic pollutants

• Inorganic pollutants

• Biological contamination

• Pathogenic microorganisms

Neighborhood Pollution

• Rainwater • Urban waste water

Underground water

• Highly polluted effluent discharges

• Waste water and runoff water

Pollution in aquatic environment

Biological pollution oocysts of cryptosporidium detected in surface water of

Port-au-Prince which used as an drinking water.Cryptosporidia are responsible for 17.5% of

acute diarhreas in infants under 2 aged and 30% of chronic diarrheas in patients infected by HIV

Biology Of Cryptospordium

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.

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.

Life Cycle Of Cryptosporidium

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

Filtration Methods

Membrane Filtration

Cartridge Filtration

Woven Acrylic Polyethersulfone

Chemical Flocculation

Detecting oocysts in Aquatic EcosystemsAnother 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.

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:

Microbiological Risk Assessment in the drinking water in Haiti

Identifying the danger

Dose response relationship

Estimating exposure

Characterizing the risk

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:

Case study of PORT-AU-Prince

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

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.

Case study of the City of Cayes

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.

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.

Risk Assessment for Contamination

Conclusion:Risk assessment is not a goal but there is an

decision making for risk management of oocyst hazards and risks for human health.

Elaboration or adoption of National drinking water guidelines.• Monitoring

Protection of groundwater resource.• Sanitary

inspection• Control of

cryptosporidium contamination in water resource

Treatment of raw water to drinking water.• Remove

heavy metals • Upgrade the

quality of drinking water.