Biology Reference
In-Depth Information
CONTROL
Once A. suum is present on a farm, it is rather challenging to completely
eliminate its presence. Although the aim of control programs against this
parasite should be to eradicate the parasite completely, a significant
reduction in transmission intensity will readily result in a marked
decrease of adverse effects on the health and productivity of the pig herd.
To effectively control parasitic infections on farms, control-by-treatment
alone will not suffice unless supported by good general farm manage-
ment and increased hygienic standards. 40,48
Chemotherapy
Before the advent of broad-spectrum anthelmintics in the 1960s,
treatment of worm infections in pigs was hardly ever applied. Since then,
the control of parasitic infections on pig farms has become increasingly
reliant on mass treatment with anthelmintic drugs. When selecting a drug
for the control of Ascaris infections, several things need to be taken into
account. Namely, (1) the margin of safety of the used compound, (2) the
efficacy of compound against the different stages of A. suum , (3) the
spectrum of activity, (4) the mode of administration, and last but not least
(5) the cost of the drug. All of the modern anthelmintics are found to be
very safe. Treatments with doses exceeding the recommended dose did
not show any clinical effect in pigs. 49 An overview of trials testing the
effectiveness of different anthelmintic drugs used for treating pigs with
Ascaris infections is shown in Table 16.2 . For the effective control of
helminth infections on a pig farm it is advantageous to select an anthel-
minticic that kills the larval stages and has a broad spectrum of activity.
All compounds presented in Table 16.2 have proven to be highly effective
against adult roundworms in pigs. Pyrantel, fenbendazole, flubendazole,
and levamisole also have shown activity against migrating stages of A.
suum . 50 e 53 Piperazine and pyrantel have restricted activity against the
other common nematode infections ( Trichuris suis and Oesophagostomum
spp.) 49 and are therefore not the drugs of choice when co-infections with
these parasites are present on a farm. Anthelmintics of the macrocyclic
lactone family (e.g. ivermectin, doramectin) have a significantly longer
residual effect in comparison with the other anthelmintics and are also
highly efficient against ectoparasites like mange mites ( Sarcoptes scabiei
var suis ) and hog lice ( Haematopinus suis ). 54 e 58
Anthelmintics are available in a variety of formulations. Administra-
tion of the drug in either water or feed is the easiest and most economical
way, but has a major disadvantage in variable dosages being delivered
when numbers of pigs are being treated in groups from a single source
of medication. Delivery by injection, on the other hand, is more accurate
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