Page 710 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Respir atory system: 3.3 Medical conditions of the upper respir atory tr act 685

VetBooks.ir (at least three) of nasopharyngeal swabs (nasal swabs welfare in early cases with pyrexia and depression,
especially foals, and in cases with respiratory distress,
are not suitable) or nasopharyngeal washes, collected
at weekly intervals and submitted for qPCR testing.
metastatic abscessation, purpura haemorrhagica and
in guttural pouch carriers. The antimicrobial of
Management choice is penicillin (22,000–44000 IU/kg i/m q12 h
The three aims of managing an outbreak of strangles or i/v q6 h). Although other antimicrobials, for
are (1) to prevent spread of infection to new prem- example cephalosporins, are effective and are used
ises, (2) to limit the spread of infection within the as alternatives by some practitioners, cephalosporins
infected premises and (3) to ensure that carriers are are not an appropriate choice under antimicrobial
identified and treated at the end of the outbreak. stewardship. Trimethoprim– sulphonamide combi-
Movement of horses on and off the infected prem- nations are ineffective in the presence of pus, mak-
ises should be suspended in order to reduce the risk ing these an inappropriate choice for strangles cases.
of infection spreading elsewhere. Personnel should In-contact horses can also be treated with antimi-
be briefed about the risk of indirect transmission crobials provided they can be moved to a clean area
and precautions taken with hand washing, clothing, and are not subsequently exposed. This approach is
footwear and tack. Management of clinical cases fraught with problems (for example horses treated
requires strict isolation and barrier nursing. On sus- while incubating disease may develop clinical signs
picion of S. equi infection, the yard should be seg- once treatment stops, or horses may become infected
regated into different risk groups in separate areas, once treatment stops if biosecurity precautions are
which can be in buildings or outside. A separation inadequate) and should be avoided in most out-
zone of at least 5 m (ideally 10 m) should be main- breaks. Antimicrobials should not be used in horses
tained between groups. An easy-to-operate system with developing abscesses; these should be managed
is to designate a red (infected) group, a yellow (in- by hot fomentation and encouraged to burst. For the
contact) group and a green (not exposed) group and same reason, extended courses of NSAIDs should be
to colour code each area, including feed utensils, avoided. Large retropharyngeal abscesses may need
forks, brushes and barrows, using electrical tape. In needle or surgical drainage under ultrasound guid-
many livery/shared yards, it is not possible to safely ance (Fig. 3.141).
designate a green group because of cohandling and Nasal shedding may not begin until 1–2 days
mixing of horses. Rectal temperatures should be after onset of fever, so transmission can be lim-
monitored and recorded from all horses twice daily ited by isolation of early cases. In most cases, nasal
and once a diagnosis has been confirmed by labora- shedding persists for 2–3 weeks. Screening for car-
tory tests, any horses developing fever, even if just riers should begin 4–6 weeks after the end of the
a single fever spike, should be considered infected. outbreak. Carriers can be successfully treated by
Horses will need to be moved from green to amber guttural pouch lavage and antimicrobial treatment
groups and from amber to red on the basis of fever using penicillin instilled locally into the guttural
or other clinical signs. The movement of personnel pouch. Chondroids should be removed endoscopi-
must be from green to amber to red, never the other cally before starting antimicrobial treatment. If the
way around, and horses can never move from red to affected pouch contains liquid, or semi-liquid, pus,
amber or amber to green while the outbreak is in it should be lavaged daily with approximately two
progress. litres of saline via an indwelling Foley catheter until
Antimicrobial treatment of clinical cases is con- there is no visible pus, before starting antimicrobial
troversial, with some clinicians advocating antibiot- treatment. Benzyl penicillin formulated as a gel with
ics should never be used for fear of prolonging the gelatin, or as a proprietary penicillin poloxmer gel
clinical disease, reducing immunity or increasing the with reverse thermodynamic properties (liquid when
risk of metastatic abscessation. However, there is no cold and semi-solid when warm), is instilled into the
evidence in the literature to support these concerns. pouch after each lavage at weekly intervals until the
Antimicrobials and NSAIDs may be used to promote pouch is negative on qPCR. Infusion of antimicrobial