water Flashcards
What is the most important pathogen in public water supplies?
cryptosporidium
but importantly now all cryptosporidiosis is waterborne
What type of pathogen is cryptosporidium and name others
It is a protozoa
Also
toxoplasma, giardia, Sarcocystis
Talk about cryptosporidium - different types? where found??
most important
Where shed?
• Single genus of unicellular protozoan parasites, many species (c.24), and discrete genotypes (>60)
• Forms environmentally resistant oocysts
• Several species (16) and genotypes (3) known to cause disease in man
most important two are
• C. parvum also causes diarrhoea in young animals, especially calves & lambs
• C. hominis appears to
be exclusive to man
• Adult animals
Asymptomatic
epi of cryptosporidium
– worldwide distribution – environmental contaminants
– animal contact (esp. farm visits)
• shed by animals and humans, end up in environment, then we get it by being in contact with water or veg
– person-to-person spread
- can be on veg,
What is the difference between food borne or water
Where the primary source is
What are human clinical signs of cryptosporidium
– nausea, vomiting – watery diarrhoea, dehydration – similar to campylobacter and cholera – weight loss – stomach cramps, fever – 3 weeks, usually self limiting – Immunocompromised really affected
What are the most common gastro intestinal infections in England and Wales?
Most common by far = campylobacter
then: salmonella and norovirus
Then Cryptosporidium
What increased the incidence of cryptosporidium in the uk
linked with inc in intensification of farming
When is there a higher risk of crypto In the UK?
When there is an increase in raw water turbidity
this means there are lots of solids in the water, due to heavy rainfall
crypto oocysts are resistant to chlorine treatment so UV light filters them out as damages their DNA
However UV doesn’t work well when high water turbidity as cannot penetrate
When there is a high water turbidity how do we respond?
When detected, water systems are shut down until the turbidity is lowered
when are oocysts most shed and location?
vs other protozoa
most shed by pregnant animals
oocysts in GI tract
too = muscles
how do they stop crypto in abattoirs?
ONLY portable (drinking) water used in slaughter houses
What are sources of water in slaughter houses
How is water treated in slaughter houses
natural spring, a reservoir, a well or a borehole
Delivery by closed system of pipes; blind ends on disused side-branches should not be present (likely to hold stagnant water)
Treatment:
flocculation (colloids suspended as flakes), sedimentation, filtration,
– then addition of chlorine or fluorine
– ozone treatment or UV light chlorination (aims to eliminate Cryptosporidium).
Waster water is collected and goes to a treatment plant
how is water tested in meat production premises?
- regular testing at water outlets and designated testing points- pre requisit programme
• ACC and coliforms are tested monthly, others e.g. e coli, closidio perfringes, annually or as a follow up when
ACC/coliforms exceed
what are pre requisite programmes?
practices and operational conditions that are essential for the production, handling and provision of food that is safe to eat
