Biology Reference
In-Depth Information
as they forage in the same infected environment. This, again, emphasizes
the importance of reducing the infection intensity on a farm.
Both the fact that infections usually seem to occur in the fattening units
and the fact that anthelmintic treatment has limited persistent activity
against recurring infectious larvae lead to the belief that the common
practice of treating pigs prior to, or upon arrival in, the fattening units
might be superfluous. In two experiments, it has been reported that
a single anthelmintic treatment of fatteners at the start of the fattening
period is not justified on economic grounds. It was shown to be ineffective
in reducing parasite prevalence and it did not have a positive effect on
performance results, nor did it influence the incidence of other lesions like
white spots.
40,48,71
More importantly, Roepstorff
66
showed that, depend-
ing on the infection status, it might sometimes be more economically
beneficial to switch from a routine anthelmintic treatment program to the
conditional usage of anthelmintics, treating only when necessary. This
should, however, be supported by routine diagnostic screening of pigs
from different age categories and is probably only applicable to farms
with moderate to highly intensive management.
Alternative Control Strategies
Over time, questions have been raised concerning the long-term
impact of the massive application of these highly efficacious, broad-
spectrum anthelmintic compounds on the environment. Due to the
marginal absorbance rate of some of these drugs, high percentages of
these substances are being excreted unchanged after oral or systemic
administration.
72,73
Decomposing animal excrement/waste is spread all
over our land for increased crop productivity, thereby also spreading the
anthelmintic drugs and their residues. However, we remain oblivious to
what the possible long-term ecological effects of these drugs and their
residues are on pasture fauna and flora.
74
This concern, among others, is
stimulating the need for alternative, more biological measures of parasite
control.
In organic farming, the use of traditional synthetic drugs is
not allowed and therefore farmers prefer a phytopharmaceutical
approach for the control of parasitic infections on their farms.
75
Although many plants are suggested to have some nematocidal
effects,
76
recent studies, e.g. by van Krimpen et al.,
75
could not show
any significant reduction on the worm load of infected pigs after
treatment with a herb mixture (
Thymus vulgaris
,
Melissa officinalis
,and
Echinacea purpurea
),
Papaya
fruits,
Bolbo
leaf or complete
Artemesia
plants in comparison with untreated controls. Nevertheless, continued
efforts could be made to standardize the plant extracts with good
anthelmintic activity and formulate the best alternative herbal
