Identifying secondary sites of infection
If the innate immune system is incapable of controlling the infection as septicemia progresses, secondary sites of infection
may develop. With the bloodstream serving as the conduit, essentially all tissues of the body are susceptible to secondary
infection. Tissues that receive a large portion of the cardiac output and experience turbulent, slow or unique blood supplies,
are targeted first and include physes, synoviae, the uveal tract, meninges, endocardium, liver, kidney and skin/muscle.
Photo 3: Petechial hemorrhages inside the ears is a reliable clinical sign associated with septicemia.
Any neonatal foal that has joint swelling, periarticular edema, lameness or prolonged recumbency should be carefully evaluated
for sepsis. The cardinal signs of uveitis are blepharospasm, epiphora, miosis, aqueal flare, edema of the iris and hypopyon
(Photo 5). These signs most often manifest bilaterally in septic foals, though unilateral presentation can occur.
Foals with meningitis often have an altered mental status, ataxia, seizures and a stiff, "guarded" neck and gait. Endocarditis
is an infrequent complication of septicemia in foals. Tachycardia, tachyarrhythmia, lethargy, murmurs, jugular pulsation and
dependent edema may be signs of endo-carditis.
Healthy neonatal foals commonly have a low-grade systolic murmur over the semilunar valves over the left heart base. However,
loud murmurs over the semilunar valves, murmurs over the mitral or tricuspid valves or those that are accompanied by other
signs of cardiac disease should be investigated further by echocardiography.
Hepatic, splenic and renal abscessation may occur secondary to septicemia, though secondary infection in these anatomic locations
rarely cause localizing clinical signs.
When the systemic pro-inflammatory response to infection is uncontrolled and malignant, the clinical state of shock and MODS
(Multiple Organ Dysfunction Syndrome) ensue.
Photo 4: Uveitis, characterized by cloudiness, aqueal flare or fibrin (arrow) in the anterior chamber, is a sign of advanced
Septic shock is defined as hypotension accompanied by signs of hypo-perfusion (altered mental status, hypothermia, hypotension,
shivering, cold extremities, mucous membrane pallor, bradycardia or tachycardia, poor capillary or jugular vein refill, poor
pulse quality, oliguria and ileus) that is induced by the presence of sepsis, is the result of systemic vasodilation and
persists, despite adequate fluid resuscitation.
The manifestations of MODS are vast and the signs reflect the organs that are predominantly affected. These may include mental
deterioration, ataxia, seizures, oliguria, coagulo-pathy, dyspnea, tachypnea, tachycardia or bradycardia, colic and/or ileus.
Ultimately, identification of clinical signs or physical findings of secondary infection, shock or MODS is significant. These
conditions not only identify an advanced and improperly controlled disease state, but they also are associated with a poor
Finally, when evaluating a neonatal foal for any reason, consider that any primary disease can induce a state of immunosuppression
and/or cause loss of integrity of local protective barriers that subsequently welcomes infection. For example, other common
diseases during the neonatal period, such as neonatal isoerythrolysis, neonatal encephalopathy, uroperitoneum, neonatal asphyxia
syndrome, meconium impaction, diarrhea or any cause of colic, may be complicated by concurrent infection.
Photo 5: Basophilic cytoplasm, vacuolization Dohle bodies (arrow) in neutrophils, are reliable signs of bacterial infection.
Michelle Henry Barton is the Josiah Meigs Distinguished Teaching Professor at the University of Georgia's College of Veterinary
Medicine, where she is a large-animal internist in academic practice. She received her DVM from the University of Illinois
in 1985, her PhD in physiology at the University of Georgia in 1990 and became an ACVIM diplomate in 1990.