Contributed Papers: Posters
Chemotherapy |
Relationship of E. acervulina Ionophore Resistance
to Field Problems with E. maxima
Greg F. Mathis, Southern Poultry
Research, Inc.
An
earlier study suggested that E. acervulina can interfere
with colonization of E. maxima. The object of this
study was to examine the relationship of E. acervulina
sensitivity to Salinomycin and subsequent infection
level with E. maxima. A battery cage study was conducted.
Birds fed nonmedicated or Salinomycin 60 g/t feed
were challenged with either a Salinomycin sensitive,
resistant strain of E. acervulina and/or an E. maxima
field isolate. The oocyst per bird challenge levels
were none; E. acervulina (sensitive); 50,000, E. acervulina
50,000 (resistant); E. acervulina 50,000 (sensitive)
plus E. maxima 5,000; E. acervulina 50,000 (resistant)
plus E. maxima 5,000; or E. maxima 5,000. E. maxima
alone caused 20 % weight reduction and 2.70 lesion
score. Salinomycin controlled the sensitive strain
with 5 % weight reduction and 1.25 lesion score. Salinomycin
did not control the resistant strain, with 22 % weight
reduction and 2.75 lesion score. The birds infected
with E. maxima and sensitive E. acervulina had E.
maxima lesion scores of 2.25. The birds infected with
E. maxima and resistant E. acervulina had E. maxima
lesion scores of 1.30. From the results it can be
inferred that E. acervulina interfered with development
of E. maxima. Higher anticoccidial resistance allows
more E. acervulina colonization, which appears to
interfere with colonization of E. maxima, and thus
indirectly slows E. maxima immunity development. This
increases chance for late problems with E. maxima,
possibly explaining an increase in field reports of
late E. maxima infections where Salinomycin has been
extensively used.