Affiliation:
1. Merck Institute for Therapeutic Research, Rahway, New Jersey 07065
Abstract
When given to sheep as a single oral dose at 0.1 mg/kg, the B
1a
component of the avermectins caused a reduction of >95% in the numbers of
Haemonchus contortus, Ostertagia circumcincta
(including inhibited L
4
larvae),
Trichostrongylus axei, Trichostrongylus colubriformis, Cooperia oncophora
, and
Oesophagostomum columbianum
. When given to cattle as a single oral dose at 0.1 mg/kg, avermectin B
1a
was >95% effective in reducing the numbers of
Haemonchus placei, Ostertagia ostertagi
(including inhibited L
4
larvae),
T. axei, T. colubriformis, C. oncophora, Cooperia punctata, Oesophagostomum radiatum
, and
Dictyocaulus viviparus
. Avermectin B
1a
was similarly effective, with the exception of a detectable loss in activity against adult
C. oncophora
, when administered to cattle as a parenteral injection. Some of these ruminant parasites were fully susceptible to dosages of avermectin B
1a
at 0.025 mg/kg, e.g.,
D. viviparus, O. radiatum, O. ostertagi
, and
H. contortus
. Avermectin B
1a
removed 83 to 100% of
Ancylostoma caninum
from dogs given a single oral dose of 0.003 to 0.005 mg/kg. The poultry nematodes
Capillaria obsignata
and immature
Ascaridia galli
were effectively removed by avermectin B
1a
at 0.05 and 0.1 mg/kg, respectively, but 0.1 mg/kg was not effective for
Heterakis gallinarum
. Thus, the avermectins would appear to have unprecedented potency and spectrum of biological activity.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Reference10 articles.
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