Agriculture Reference
In-Depth Information
thinning of the flock, more campylobacter are found in
the older birds. There can also be a significant increase
in the numbers after transport to the plant. The number
of organisms found in the inside of the bird is relevant to
that found on the outside.
In the poultry plant, raising the pH of the scald tank
with caustic soda or reducing it with acetic acid has no
significant effect. Carcase washes and irradiation have
yet to prove successful.
In addition, independent investigations have isolated
C. jejuni
from aseptically taken muscle samples. In epi-
demiological studies, there has been no effect noticed on
the rate of infection in poultry units with concrete floors
and surrounds as against those with earthen floors.
Farm studies carried out in Sweden showed that 16%
of flocks were colonised with campylobacter. There was a
seasonal variation with more positive flocks in late sum-
mer and autumn. There were differences in occurrence
between farms delivering chickens to different processing
companies. This might indicate different levels of farm
hygiene and management. Generally, only one serotype
was found in each flock, which would indicate only one
source at a time, instead of infections from several differ-
ent reservoirs. The most common serotypes in chickens
were also the most common serotypes isolated from the
surroundings, for example, ditchwater and faeces of wild
birds. In general, no campylobacter, or new serotypes,
were isolated in the following flocks, indicating that the
infection was not permanent in the buildings and that the
washing and disinfection of houses between flocks was
sufficient to eliminate campylobacters.
Chickens were not colonised with campylobacter
before 2 weeks of age. No connection was found between
serotypes in broiler flocks and in broiler parents from
which the eggs were taken. Broiler parents carried sev-
eral serotypes in each flock. These epidemiological stud-
ies excluded buildings, feed, straw and day-old chicks as
the source of campylobacter infection to the broiler
flock. It was thought unlikely that water would be a
source for the Swedish chicken flocks.
Chlamydiosis (psittacosis/ornithosis)
Chlamydiosis is sometimes referred to as psittacosis
when it affects humans, mammals and birds of the par-
rot (psittacine) family and as ornithosis for birds other
than psittacine. The cause is the intracellular parasite
Chlamydia psittaci
, which belongs to the Group B
chlamydias - organisms of uncertain status occupying a
position between bacteria and viruses but probably more
related to the former.
The disease is worldwide in distribution, affecting all
types of poultry and wild birds. It has a serious public
health significance in that man may become affected,
usually from close contact with birds of the parrot
family. Infection occurs by inhalation of particles of
infected dust (Fig. 10.22).
Lesions.
The disease may be either acute or chronic,
which tends to complicate the non-specific post-mortem
findings. The lesions range from airsacculitis with thick-
ened inflamed air sacs containing yellowish-white exu-
date to pneumonia, pericarditis, perihepatitis and
enlargement of the liver and spleen.
Judgement.
Affected carcases should be totally con-
demned. Diagnosis can be established only by laboratory
examination, and cases should be reported to the regula-
tory authorities. Birds suspected at ante-mortem inspec-
tion of being affected with ornithosis must not be
slaughtered because of the disease risk to operatives.
Control of campylobacteriosis
A strict and well-applied hygiene barrier seems to be the
most important factor for preventing chicken flocks
from campylobacter colonisation, under the assumption
that the chicken house is a closed unit. It was considered
that the elimination of disinfectant footbaths and the
introduction of changing footwear at a well-defined
hygiene barrier, 40 cm high, is essential for keeping
campylobacter out of broiler farms. As campylobacter may
enter from multiple sources outside the rearing units, it
is important to prevent all possible ways of transmission
into the house. In the United Kingdom, the main sources
are the environment outside the houses, drinking water,
rodents and wild birds. The organism has been found
in flies, which could carry it from house to house, and
people. Biosecurity of the premises is essential.
Chickens appear to become infected at around 3 weeks
of age when the number of
Salmonella
in a flock peaks.
However, the number of campylobacter continues to
increase. When a flock becomes positive, the organism
transmits to 90% of the birds in less than 1 week. After
Miscellaneous conditions
Dead on arrival
These birds must be condemned and not processed. It is
important that the catching team recognise birds which
are unfit for slaughter and euthanise them on the farm.
Bruising and fractures
Causes include improper handling by the catching
team and, at the poultry plant, careless shackling
and defective stunning techniques and wing flapping.
Any parts of a carcase with localised bruising are
rejected. Severe generalised bruising indicates total
condemnation.
