Page 4 - Clinical Connections - Spring 2022

 

 

 

 

 

Page 4 - Clinical Connections - Spring 2022
P. 4

 RESEARCH    STUDY    VETERINARY SERVICES       .AC.UK
         Equine
        RESPONSIBLE ANTIMICROBIAL USE IN
        HORSES


        Bettina Dunkel, Head of  Equine and Professor in Equine Internal Medicine, Emergency and
        Critical Care
               any  diseases  in  horses  are   and  neoplastic  conditions  –  or  following   of negating a treatment success often leads
               associated with bacterial infection.   administration of corticosteroids – and is   to prolong use of antimicrobials in clinically
        M Unfortunately, viral or fungal    therefore also of limited use. As immediate   apparently recovered patients. In the past,
        infection, bacterial toxins, tissue damage or                           return to normal haematologic parameters
        neoplasia also cause systemic inflammation                              or normal concentrations of acute phase
        and clinical signs are indistinguishable from                           proteins have been used as markers to
        bacterial infection.                                                    safely  discontinue  antimicrobial  treatment.
          Although  not  effective  against  viral,                             Return to normothermia, improved appetite
        inflammatory  or  neoplastic  conditions,                               and return of normal demeanour might be
        antimicrobials  are  often  used  in  these                             better indicators that further treatment is not
        cases as it can be difficult to conclusively                            necessary.
        rule out a bacterial infection. Due to
        increasing  microbial  resistance,  pressure
        on  veterinarians  is  mounting  to  adhere  to
        responsible use of antimicrobial drugs.
          Clinical  examination  findings  are  often   A foal at the  Equine Referral Hospital
        non-specific  and  while  the  presence  of  a
        fever  increases  suspicion  of  an  infection,   treatment is usually required, clinicians
        it  is  not  conclusive  as  inflammation,   need to make an educated guess whether
        hyperthermia, neoplasia or tissue trauma   bacterial infection is likely.
        can also lead to an increased temperature.   Many equine  viral  and some bacterial
        Equally, the absence of a fever does not rule   diseases can be diagnosed by polymerase
        out even severe infection.          chain reaction (PCR) with results often being    Equine Referral Hospital
          Haematology and acute  phase  protein   available the following day. Cytological
        concentrations,  such  as  fibrinogen  or   samples can be of great value when trying   It  is  also  common  practice  to  initially
        serum  amyloid  A  (SAA),  can  be  difficult   to rule out an infectious aetiology, as results   treat systemically ill horses with injectable
        to interpret as increases are triggered by   are available much quicker than culture   antimicrobial drugs for 48-72h followed by
        infectious  and  non-infectious  inflammatory   results. In cases where clinicians have   continued oral treatment. In most cases, this
        conditions 1, 2 . In adult horses, leucopaenia   already initiated antimicrobial treatment,   is not necessary. An alternative approach is
        is  commonly  observed  with  inflammation,   but  PCR  or  cytology  do  not  support   stopping antimicrobial treatment after 48-72h
        often  originating  from  the  gastrointestinal   a bacterial infection or identify a viral   and monitoring the patient for another 24h
        system. It does not necessarily indicate   cause,  antimicrobial  treatment  should  be   closely. Should signs of infection re-occur,
        the presence of infection or the need for   discontinued immediately.   such as recurrence of a fever, a decrease in
        antimicrobials.                       The old concept that “a course of   appetite or change in demeanour, treatment
                                            antibiotics  needs  to  be  finished  to  avoid   can easily be re-initiated – but this is rarely
                                            development of resistance” is obsolete and   necessary.
                                            not supported by evidence. To the contrary,
                                            reducing  the  length  of  treatment  has  a
                                            significant  effect  on  decreasing  previously   References
                                            existing resistance  while increasing the   1.  Westerman, T.L., et al., 'Evaluation of serum
                                                           3
                                            length of antimicrobial use increases the risk   amyloid A and haptoglobin concentrations as
                                                                                  prognostic indicators for horses with inflammatory
                                            of resistance development . In most cases   disease examined at a tertiary care hospital', Am J
                                                                4
                                            a short duration of antimicrobial therapy,   Vet Res, 2015. 76(10): p. 882-8.
                                            ranging  from  a  single  dose  (for  example   2.  Long, A. and R. Nolen-Walston, 'Equine
                                                                                  Inflammatory Markers in the Twenty-First Century:
                                            pre-operatively) to 24-72h, is sufficient, with   A Focus on Serum Amyloid', A. Vet Clin North Am
                                            long-term treatment being rarely required.  Equine Pract, 2020. 36(1): p. 147-160.
                                              Recent studies in people have shown   3.  Dona, D., et al., 'Implementation and impact of
                                                                                  pediatric antimicrobial stewardship programs: a
                                            impressive reductions in antimicrobial   systematic scoping review', Antimicrob Resist
                                            resistance with a reduction of not only   Infect Control, 2020. 9: p. 3.
                                            overall use but also with a decrease in days   4.  Llewelyn, M.J., et al., 'The antibiotic course has
                                                                                  had its day', BMJ, 2017. 358: p. j3418.
         A horse at  Equine              of antimicrobial therapy, highlighting the
                                            importance of shortening treatment . Limiting     For equine referrals, please call: 01707
                                                                      3
          Leucocytosis in mature horses can be   the duration of antimicrobial treatment in   666297
        observed  with  inflammatory,  infectious   proven infections can be challenging. Fear     Email:
                                                                                     equinehospital@rvc.ac.uk

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