Biology Reference
In-Depth Information
and viral diseases in pigs (e.g. salmonellosis, mycoplasma infection,
Aujeszky's disease, PRRS virus, etc.). However, for
Ascaris
, a commercial
serological test is currently not available. The use of a serological method,
however, could in theory overcome the difficulties associated with the
traditional methods (examination of feces or livers) of diagnosing asca-
riasis in pigs.
It can be assumed that all pigs within a unit are exposed to a similar
amount of migrating larvae as they reside in the same infective envi-
ronment. In contrast, only few pigs in the population will eventually
harbor adult worms in their intestine.
11,25
Moreover, pig performance has
shown to be negatively associated with the amount of larvae migrating
through the body of the host.
18
Hence, serological diagnosis should be
aimed at detecting larval exposure rather than the presence of adult
worms.
Several studies have previously described the use of an Enzyme
Linked ImmunoSorbent Assay (ELISA) for the detection of anti-
Ascaris
antibodies in the sera of swine. In this regard, the use of different
adult and larval extracts or excretory/secretory products has been
evaluated.
37,38,43
e
47
Although most of these tests have been shown to be
effective in diagnosing
A. suum
infections, the sensitivity and specificity of
these tests are unclear. The reason for this is that traditional methods, like
the detection of parasite eggs in the stool or white spots on the liver at
slaughter, were used to categorize the pigs used for the validation of the
serodiagnostic test. Due to the lower sensitivity of these traditional
methods (see previous sections) there is a significant chance to include
false negative samples in the evaluation of the ELISA.
Recently, for the validation of an experimental ELISA, Vlaminck
et al.
47
used sera from 190 pigs that were trickle-infected twice a week
for 14 weeks, thereby ensuring that no false negative samples would be
included for the validation of the ELISA test or the determination of its
cut-off value. In the same study it was also advised to test serum
samples from older fattening pigs, as the number of seropositive pigs
increases with time.
47
This would reduce the chance of including false
negatives when screening a farm for the presence of
Ascaris
infection
using this serodiagnostic technique. This ELISA is currently being used
to investigate whether or not the serological response to
A. suum
can be
coupled to different production parameters of the investigated pig farm.
If so, test results could appeal more to the farmer. It would help improve
his awareness on the topic and convince him of the fact that a more
effective helminth control program could significantly improve farm
profitability. In this way, serological testing could serve as a cost-
effective, supportive tool for the veterinarian to assess the worm
status of a farm and to evaluate whether changes in worm-control
management are necessary or not.
