Agriculture Reference
In-Depth Information
ranging from 0% in Denmark, Estonia, Finland and
Luxemburg to 85.6% in Hungary (United Kingdom 3.6%).
Currently, only about 200
Salmonella
serotypes are
associated with food-borne infections in humans in any
1 year in the United Kingdom.
Salmonella virchow
and
Salmonella thompson
can be
invasive in humans and therefore may be as important as
S. enteritidis
and
S. typhimurium
.
Salmonellas gain access to a flock mainly through
feed, but infection may also arrive through contami-
nated stock, wild and feral animals and personnel. There
may also be a carry-over of infection from previous
stock. Good biosecurity is essential including an all-in/
all-out policy on farms, where all birds are of the same
age and are all brought in at the same time and disposed
of to allow for proper cleaning and disinfection between
crops. Visitors should be discouraged and only essential
staff should be allowed access. The perimeter of the farm
should be identified, preferably fenced and gated
securely, with parking facilities away from the buildings.
Good management is dependent on a clean and tidy site.
Rodent control is enhanced by the control of vegetation,
including in and around ditches, with effective general
management. There should be a rodent control pro-
gramme. Feed spillages should be avoided, and any spills
should be cleared up immediately.
Monitoring for
Salmonella
should be carried out to
help reduce dissemination and ensure decontamination.
There is a National Control Programme for
Salmonella
in broiler flocks (www.defra.gov.uk). Environmental
samples are better than faecal, and the best sites are nest
boxes, slave feed hoppers and fan outlet ducts. Other
good sites on breeder farms are egg collection trays,
walkways, egg sorting tables and mice. Spillage from egg
trays is best in layer houses. Input sampling should
include feed, residue from lorry and feed mill audit and
chicks; the chick box liners should be put into an auto-
clave bag with peptone for transport to the laboratory. In
the hatchery, trolleys and trays should be sampled as well
as fluff samples.
Sampling of cleaned and disinfected houses is essen-
tial prior to restocking. Peptone water should be put in
cracks on the wall half an hour before swabbing, and
large fist-sized swabs should be used rather than rectal
swabs. The best sites for sampling are floor sweepings,
nest box floors, slave hoppers, hydrated walls and fan
duct outlets.
Vaccination against
S. enteritidis
has been used. Other
methods of control have included competitive exclusion
(the Nurmi effect), where beneficial bacteria are given to
young chicks at day old to prevent colonisation of the gut
with harmful bacteria, and the use of acids in the feed to
kill the
Salmonella
organisms.
Campylobacteriosis
Campylobacter
is the most common cause of diarrhoea
in humans in the United Kingdom although not as seri-
ous as
Salmonella
food poisoning.
The bacteria (
Campylobacter coli
,
Campylobacter
jejuni
), once swallowed, multiply in the gut, and after
3-5 days (usually, range 1-10 days), the patient develops
abdominal pains, diarrhoea and sometimes vomiting
and fever. Although unpleasant, the illness is rarely fatal
and patients usually recover within a few days. The
definitive diagnosis is made by growing and identifying
the bacteria in the laboratory.
The main sources for campylobacter are raw meat,
especially offal, and poultry, where the bacteria may be
found in a large proportion of raw broiler chickens sold
in shops and supermarkets. Although present in food,
they do not usually multiply; therefore, it is rarely the
cause of an explosive outbreak of infection. However, the
number of bacteria required to cause illness is very small -
fewer than 500 can cause infection. About 3000 people
are admitted to hospital annually in Britain owing to the
disease. In 2003, there were 48 000 cases diagnosed.
Other cases are treated by medical practitioners, but the
actual figure for those affected in Britain each year may
exceed 500 000.
The prevention of infection in humans involves
inhibiting transmission through water, milk and food.
All animals shed campylobacters into lakes, rivers,
streams and reservoirs; therefore, all water destined for
human consumption needs to be properly treated. In
Britain, defective storage tanks have caused outbreaks
affecting up to 250 people.
Milk that is not pasteurised or heat treated may con-
tain the bacteria.
Good kitchen hygiene with the correct handling of raw
meat and animal products is essential to prevent infec-
tion. Raw poultry and other types of meat should be kept
separate from other food and should be properly cooked.
Incidence of campylobacteriosis
A survey carried out by the European Food Safety
Authority in 2008 showed an average prevalence of
campylobacter-contaminated broiler carcases in the EU
of 75.8% ranging from 98.3% in the Republic of Ireland
to 4.9% in Estonia (United Kingdom 86.3%).
In the United States, poultry is associated with 50-70%
of human cases of campylobacter infection.
C. jejuni
is
the most common isolate found in chickens. Broiler
flocks are frequently campylobacter positive and 100%
of birds tested can be positive. Chicken carcases are also
often heavily contaminated, and numbers of campylo-
bacter per carcase can exceed 10
6
(Fig. 10.21).
