Page 1363 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1338 CHAPTER 14

VetBooks.ir efficiency of the innate immune system, subsequent is not balanced by the compensatory anti-inflam-
matory response syndrome. Uncontrolled SIRS or
to the lack of absorption of complement and other
factors. Sepsis occurs in foals when the bacterial
dysfunction and death. The major factors that con-
challenge exceeds the host immune response, due to sepsis rapidly leads to a syndrome of multiorgan
either the magnitude or pathogenicity of bacterial tribute to this include circulatory collapse, from
challenge, or a reduced host response. endothelial dysfunction and myocardial suppression,
The most common route of entry for bacteria into and coagulation dysfunction with the formation of
the foal’s circulation is via the intestinal tract. The microthrombi in the blood vessels within various
enterocytes designed to allow pinocytosis of immu- tissues. The most common bacteria implicated in
noglobulin are non-specific and can rapidly trans- neonatal sepsis are all environmental pathogens and
port bacteria in addition to immune factors directly include E. coli, Enterobacter spp., Staphylococcus spp.,
into the circulation. Other routes of pathogen entry Streptococcus spp., Actinobacillus spp., Klebsiella spp.,
include the respiratory tract, the placenta in utero and Pasteurella spp., Salmonella spp., Clostridium spp. and
the umbilicus. Following invasion of the pathogen a Enterococcus spp. In many foals, sepsis is caused by
cascade of events is initiated, which is responsible for mixed infections.
most of the clinical signs seen with SIRS and sepsis.
Pathogen associated molecular patterns (PAMPs), Clinical presentation
present on bacteria, activate both the innate and Clinical signs are variable. They may range from sub-
adaptive immune systems. Leucocytes and other tle, non-specific and insidious in onset to acute and
inflammatory cells release cytokines that cause fur- fulminant. They may include: less frequent feeding
ther upregulation of the immune system. The cas- or complete anorexia; lethargy and increasing peri-
cade initiates a wide variety of effector organs and ods of recumbency; increased heart and respiratory
tissue types including the coagulation system, endo- rates; increased respiratory effort; respiratory dis-
crine system and endothelial cells. tress; raised or subnormal temperature; congestion
In a well-balanced immune response, activation and petechiation of mucous membranes; coronary
of the inflammatory cascade causes removal of the band hyperaemia (Fig. 14.5); altered mental status
bacterial pathogen from the circulation and a return such as depression and seizures; diarrhoea; colic
to normal homeostasis. However, in many situa- and abdominal distension; uveitis with ocular pain
tions, the immune response becomes excessive and (Fig. 14.6); hypovolaemia; bone or joint infections

14.5 14.6

Fig. 14.5 Distinct hyperaemia of the coronary band Fig. 14.6 A septic uveitis of the left eye of a foal with
can be an indication of sepsis. septicaemia. Note the marked miosis of the pupil.