PROJECT SUMMARY
This proposed project addresses FOA: NIH RFA-FD-19-024: Conduct studies to establish
more targeted durations of use for certain approved antimicrobial new animal drugs in
food animals. Optimizing antimicrobial usages and promoting judicious antimicrobial use
are pivotal to preserving the efficacy of medically-important antimicrobials and vital to
protecting food security. The long-term goal of this work is to promote sustainable
livestock production through judicious antimicrobial use to control active infection of the
hemoparasitic pathogen, Anaplasma marginale (Am), the etiologic agent of bovine
anaplasmosis. Chlortetracycline (CTC) antimicrobials are the only FDA-approved drug to
control anaplasmosis and may currently be administered continuously during the entire
pasture-feeding season and beyond if under an active VFD. Continuous exposure to a
single drug class for prolonged periods introduces strong selective pressure for the
development of resistance. The guiding hypothesis of this proposal is that targeting
antimicrobial treatment to coincide with strategic periods in the Am transmission cycle will
effectively control active anaplasmosis and minimize risk of antimicrobial resistance.
Through integrated cooperation between scientists and clinicians, the hypothesis will be
tested, using the current FDA-approved CTC labeled dose indicated for the control of
active anaplasmosis, by answering the following questions: (i) Is the current FDA-
approved dosage of CTC effective to control active anaplasmosis? (ii) In what timeframe,
relative to infection, must CTC treatment be initiated (targeted) to effectively control active
anaplasmosis? (iii) For what duration must CTC treatment be administered to effectively
control active anaplasmosis? (iv) Can a strategic interval CTC treatment protocol, derived
from the above information, effectively control active anaplasmosis long-term?, and (v) Is
this CTC treatment protocol broadly effective against diverse Am strains? Data generated
from this proposal will provide pivotal evidence for the effectiveness of CTC, at the current
FDA-approved label dose, when administered within an appropriately-timed target
treatment window and for a defined treatment duration. Together, the goal of this proposal
is to provide pivotal data to drug sponsors, federal policy makers, and veterinarians on
an effective targeted and defined duration of use CTC treatment protocol, at the current
FDA-approved label dose, to control active anaplasmosis in cattle, while also protecting
antimicrobial efficacy through promoting judicious antimicrobial use.
