Contributed Papers: Oral Presentations
Mixed Cocciodiosis Control: Drugs and Vaccines |
Comparison of
drug-sensitivity and species composition of Eimeria
isolated from poultry farms utilizing either anti-coccidial
drugs or a live oocyst vaccine to control avian coccidiosis.
M.C. Jenkins1, S. Klopp2, G. Wilkins1,
K. Miska1.
1Animal Parasitic Diseases Laboratory, ARS, USDA,
Beltsville, MD, USA. 2Townsends, Inc., Georgetown,
DE, USA. mjenkins@anri.barc.usda.gov.
The purpose of this study
was to compare drug resistance and species composition
of Eimeria isolated from two types of poultry operations
that differed in the means of controlling avian coccidiosis
(i.e. drugs vs. live oocyst vaccine). Poultry litter
was collected from 10 different broiler operations;
5 utilizing anti-coccidial drugs, 5 utilizing a live
oocyst vaccine. The number of species present in vaccine-control
facilities was greater than in drug-control operations,
with all 6 species present in the former, and 3-4
species present in the latter. The pathogenicity of
oocysts propagated from the vaccine-using farms was
greater than in the drug-utilizing farms, in that
3.5 times fewer oocysts were needed to cause similar
levels of weight depression. Eimeria propagated from
drug-utilizing operations displayed greater anti-coccidial
resistance, as measured by lower weight gains, higher
intestinal lesion scores, and poorer feed conversion
ratios, compared to Eimeria recovered from farms using
a live oocyst vaccine. Only one drug, Avatec, provided
greater than 90% weight gain protection against coccidiosis
in broilers challenged with oocysts recovered from
drug-utilizing farms. In contrast, three drugs-Coban,
Biocox, and Avatec, provided greater than 90% protection
against challenge with oocysts recovered from vaccine
farms. Quite unexpected was the partial resistance
to two drugs, Clinicox and Monteban, observed in oocysts
isolated from vaccine-using farms. These results suggest
that conventional drug treatment leads to lower Eimeria
species diversity coincident with slightly greater
drug resistance. The mechanism by which non-vaccine
drug-resistant species are introduced into vaccine-utilizing
farms remains to be determined.
