Page 709 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

684 CHAPTER 3

VetBooks.ir lymph-node abscesses bulging under the floor of Ultrasonography can be used to investigate retro-
pharyngeal abscesses and to perform guided aspira-
the medial compartment of the pouch, and for
tion and drainage (Figs. 3.140, 3.141). Radiography
sampling of this site using lavages (Fig. 3.139).
is an alternative means of assessing the retropharyn-
geal region and the guttural pouches and can be use-
ful for identifying pus or chondroids in the guttural
3.139
pouches and paranasal sinuses.
Identifying carriers is not cheap or easy and
requires detection of bacteria in either nasopharyn-
geal and guttural pouch samples. When managing
an outbreak, it is therefore important to preserve
some budget to fund the diagnostic sampling at the
end. Serology using the duplex iELISA is a cost-
effective and highly sensitive and specific method
of separating groups of horses into those which
have been exposed to infection (and so need follow-
up sampling to determine their carrier status) and
those which have not (and so do not need follow-up
Fig. 3.139 Strangles infection in a guttural pouch sampling). The preferred, and usually most cost-
showing the medial compartment on the left side of the effective, method of identifying carriers is to collect
picture and the lateral compartment on the right side. guttural pouch lavages endoscopically from both
In between is the stylohyoid. The mucosal lining of the pouches as well as a nasopharyngeal swab, and to
guttural pouch is thickened and inflamed. The pouch test these by qPCR (the samples can be combined to
contains a small amount of mucopurulent secretions reduce costs, if desired). If guttural pouch endoscopy
and multiple stone-shaped inspissated pus (chondroids). is not feasible, carriers can be identified using a series

3.140 3.141

Fig. 3.140 An ultrasonographic image of a
retropharyngeal abscess following an infection with
strangles (left is dorsal and right ventral). The abscess
measures approximately 9 cm deep from the skin into
the throat area. It has a heterogeneous echogenicity Fig. 3.141 Purulent secretion draining from
and a capsule can be identified around it. Medially the retropharyngeal abscess after a stab incision
(ventral on image) the hypoechoic circular structure through the skin. The optimal point of incision was
is the carotid artery. determined using ultrasonography (see 3.140).