Embryonation and infectivity of Ascaris suum eggs isolated from worms expelled by pigs treated with albendazole, pyrantel pamoate, ivermectin or piperazine dihydrochloride
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Abstract
The effect of anthelmintic treatment of pigs on the embryonation and infectivity of
Ascaris suum eggs isolated from expelled worms was investigated. Four groups of two
naturally infected pigs were dosed with albendazole, pyrantel pamoate, ivermectin
or piperazine dihydrochloride, respectively. Following worm expulsion, the eggs were
removed from the uteri of female worms and embryonated in sulphuric acid. The infectivity
of the embryonated eggs was tested through mouse inoculation. Egg development appeared
normal in cultures from worms of the piperazine. pyrantel and ivermectin treated groups.
In the albendazole cultures, egg development was largely arrested at the one-cell
stage (81%). Where development occurred, irregular cell division was observed and
only 7% of the eggs in the culture developed into fullgrown larvae. Following mouse
inoculation with 2500 embryonated eggs, significantly lower lung larval counts on
day 8 post inoculation (p.i.) were observed for mice in the piperazine and pyrantel
treated groups (P < 0.01) compared to untreated controls. The larvae that developed
in the eggs from ivermectin and albendazole treated groups appeared fully infective
for mice. It was concluded that ovicidal activity of albendazole in vivo inhibits
subsequent A. suum egg development in vitro; albendazole is, therefore, not suitable
to obtain worms for egg embryonation to produce experimental inoculums. The anthelmintic
treatment of pigs with ivermectin had only a limited effect on both embryonation and
infectivity of A. suum eggs isolated from expelled worms.