Saturday 29 March 2014
Monday 3 March 2014
Giardiasis
Infectious agent:
Giardia lamblia is a flagellate protozoan which lives in the
duodenum and jejunum.
Identification:
Clinical features :
Giardia infection is usually asymptomatic but may
present as acute or chronic diarrhoea associated with abdominal cramps,
bloating, nausea, vomiting, fever, fatigue and weight loss. Fat malabsorption
may lead to steatorrhoea. Symptoms usually last one to two weeks or months. The
rate of asymptomatic carriage may be high.
Method of diagnosis:
Stool microscopy for cysts or trophozoites can be used for
diagnosis of Giardia however a negative test does not preclude
infection.
Incubation period:
The incubation period is usually one to three weeks but it can
be longer. It is on average seven to ten days.
Public health significance and occurrence:
Occurrence is worldwide and endemic in most regions. Over 800
cases are reported in Victoria each year. Infection is detected more frequently
in children than adults. It is readily transmitted in institutions such as day
care centres among children who are not toilet trained. Other risk factors for
infection include travel to high risk areas, immunosuppression, male to male
sexual intercourse and achlorhydria.
Reservoir:
Reservoirs include humans and animals as well as contaminated
waters.
Mode of transmission:
Transmission occurs person to person and animal to person via
hand to mouth transfer of cysts from infected faeces or faecally contaminated
surfaces. Waterborne outbreaks may occur due to faecal contamination of public
water supplies or recreational swimming areas.
Period of communicability:
Food or water-borne Illness
Infectious agent:
The most frequent causes of food or water-borne illnesses are
various bacteria, viruses and parasites. Refer to specific sections for detail
on the more common agents. Non-infective agents:
• heavy metal poisoning, including, cadmium, copper, lead, tin
and zinc
• fish toxins that are present in some shellfish or fish like
paralytic shellfish poisoning or ciguatera
• plant toxins which occur naturally in some foods such as toxic
fungi and green potato skins
• toxic cyanobacteria (blue green algae) overgrowth in water. Bacteria:
• toxin produced in food:
– Staphylococcus
aureus
– Clostridium
botulinum
– Bacillus cereus
• damage to gut wall and/or systemic infection:
– Salmonella spp.
– Shigella spp. – Clostridium perfringens
– Campylobacter spp.
– E. coli.
– Helicobacter
pylori
– Vibrio cholerae/V.
parahaemolyticus
– Yersinia
enterocolitica
– S.typhi/Paratyphi
– Brucella spp.
– Listeria
monocytogenes
Viruses:
• Hepatitis A and E viruses
• Noroviruses and other small round
structured viruses (SRSV)
• Rotavirus
Parasites:
• Cryptosporidium spp.
• Entamoeba
histolytica
• Giardia lamblia
Identification:
Clinical features :
Symptoms vary with the causative agent and range from slight
abdominal pain and nausea to retching, vomiting, abdominal cramps, fever and
diarrhoea. Fever, chills, headache, malaise and muscular pains may accompany
gastrointestinal symptoms. Vomiting, with or without diarrhoea, abdominal
cramps and fever are common symptoms of viral disease or staphylococcal intoxication.
Certain foodborne
illnesses can present with meningitis or septicaemia
(listeriosis) or with neurological symptoms ((paralytic
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