WATER

1
WATER MILK-BORNE DISEASES

• Shigella, Hepatitis A, Giardia intestinalis,
  Cryptosporidium parvum

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Shigella

• Shigellosis (bacillary dysentry)
• The organism G-ve, facultatively anaerobic,
• non-motile,
  rod-shaped bacterium,
• Family
  Enterobacteriaceae
• Four species S. dysenteriae (developing
• 
  countries)
• S. sonnei
  (developed countries)
• Very similar to E. coli

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Shigella

• Characteristics
• - survives freezing
• refrigeration
• - it can grow in the absence
• of oxygen

4
Shigella

• CCPs hurdles
• - inactivated at low pH
• - sensitive to Gamma radiation

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Shigella

• Pathogenesis
• - bacteria invade colonic epithelial
  cells
• - death of infected host cells
• - spread of focus of infection
• - abscess formation
• - cell death tissue destruction result
• in intense inflammatory reaction

6
Shigella

• The illness
• - incubation 12 hrs to 4 days
• - abdominal pain, watery diarrhoea
  fever
• - progresses to stools with blood
• mucous, tenesmus
• - complications HUS, toxic megacolon,
• intestinal
  perforation

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Shigella

• The illness, continued
• - infective dose 10 to 100 cells
• - susceptible children lt 6 yrs,
  people
• in nursing homes prisons
• - Rx oral replacement fluids,
  antibiotics

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Shigella

• Sources
• - human primary reservoirs/carriers
• - animal only primates
• - food contaminated (water, soiled
  hands)
• - environment contaminated water

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Shigella

• Outbreaks/incidents
• NZ
• - between 100 250
• cases p.a.
• Overseas
• - dips, lettuces, salad
• parsley

10
Hepatitis A virus (HAV)

• Hepatitis A
• The organism single stranded RNA virus,
• Family Picornaviridae, genus
  Hepatovirus
• Single serotype and 7 genotypes four
• 
  found in humans

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Hepatitis A virus

• Characteristics used for control
• - grows in primate cell lines (does not grow
  in food water)
• - HAV is very stable (resistant to heat,
  acids solvents)
• - infectivity decreased by alcohol,
  chlorine,
• hypochlorite, iodine formalin
• - inactivated by UV radiation

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Hepatitis A virus

• Pathogenesis
• - infection of hepatocytes
• - elevation of liver enzymes
• inflammation of the liver
• - cytotoxic T cell response
• destruction of infected
  hepatocytes
• - virus particles released into bile duct
• - excreted in faeces

13
Hepatitis A virus

• The illness
• - incubation 4 weeks
• - initially fever, headaches, fatigue,
• anorexia, nausea
  vomiting
• - later viraemia, jaundice hepatitis

14
Hepatitis A virus

• The illness, continued
• - infective dose not reported
• - all age groups susceptible
• - Rx - rest low fat diet

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Hepatitis A virus

• Sources
• - human human faeces main reservoir
• - animal primates
• - food contaminated food (food
  handlers)
• - environment soil water contaminated
• 
  with human faeces

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Hepatitis A virus

• Outbreaks/incidents
• NZ
• - contaminated food
• water
• Overseas
• - contaminated well
• water, bread, salads,
• shellfish, berries

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Giardia intestinalis

• Giardiasis
• The organism protozoan
• parasite
• Simple direct life-cycle
• Trophozoites cysts

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Giardia intestinalis

• Characteristics
• - no growth outside animal host
• - cysts survive in cool, moist
  environments

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Giardia intestinalis

• CCPs hurdles
• - cysts destroyed by heat
• - milk pasteurization destroys cysts
• - freezing of cysts for longer periods
• inactivates
• - cysts need gt chlorine levels than E. coli
• - physical removal of cysts by filtration

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Giardia intestinalis

• Pathogenesis
• - ingestion, excysts in duodenum
• - trophozoites formed by binary fission
• - establishment of infection in host
• - trophozoites attach to epithelium of
• upper small intestine
• - some encyst pass out with faeces

21
Giardia intestinalis
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Giardia intestinalis

• The illness
• - incubation 1 to 3 weeks
• - nausea, inappetance, fatigue
• - foul smelling watery diarrhoea
• - flatulence abdominal distension
• - infective dose as few as 10 cysts
• - all age groups susceptible
• - Rx chemotherapy, vaccination

23
Giardia intestinalis

• Sources
• - human asymptomatic carriers
• - animal some isolates from mammals,
  birds, reptiles
• amphibians
  pathogenic to humans
• - food agricultural products subject to
  faecal
• contamination
• - environment faecally contaminated water

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Giardia intestinalis

• Outbreaks/incidents
• NZ
• - 46/100 000
• - peak in autumn
• Overseas
• - contaminated water,
• salad, raw sliced
• vegetables, etc.
• - contaminated by food handlers

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Cryptosporidium parvum

• Cryptosporidiosis
• The organism protozoan parasite, life cycle
  resembles that of other coccidia
  

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Cryptosporidium parvum

• Characteristics
• - grows only in host
• - oocysts survive in river drinking
  water

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Cryptosporidium parvum

• CCPs hurdles
• - milk pasteurization destroys oocysts
• - temperatures gt 73 deg. C
• - eventual die-off of oocysts at 150C
• - sensitive to UV in sunlight

28
Cryptosporidium parvum

• Pathogenesis
• - oocysts ingested
• - release of sporozoites
• - series of developmental stages in
  micro-
• villi of small intestine epithelial
  lining
• - parasitise cells, deriving essential
  nutrients
• from host cells for growth
  development
• - oocysts formed pass out with faeces

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Cryptosporidium parvum
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Cryptosporidium parvum

• The illness
• - incubation 3 to 11 days
• - watery diarrhoea, vomiting, anorexia,
• malaise, cramping weight
  loss
• - symptoms last 2 to 4 days
• - immuno-deficient patients infected for
  life
• 
  

31
Cryptosporidium parvum

• The illness, continued
• - infective dose lt 10 oocysts
• - all individuals susceptible
• - no effective Rx

32
Cryptosporidium parvum

• Sources
• - human main source
• - animal C. parvum disease in calves
• - food raw milk, meat, raw fruits
• vegetables
• - environment faecally
• contaminated water

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Cryptosporidium parvum

• Outbreaks/incidents
• NZ
• - 21/100 000
• - peak in autumn
• Overseas
• - raw milk in Tasmania
• - chicken salad, apple
• cider fermented milk
• drink