Signs of a Septic Foal
by: Erica Larson, News Editor
There's nothing more exciting than watching a newborn foal scampering around a pasture with his dam. Conversely, there's nothing more heart-wrenching than watching a newborn foal fight for his life after being diagnosed with septicemia: the potentially deadly presence of bacteria or bacterial toxins in the bloodstream. According to Mary Rose Paradis, DVM, MS, Dipl. ACVIM, an associate professor in the Department of Clinical Sciences at Tufts University's Cummings School of Veterinary Medicine, in North Grafton, Mass., diagnosing and treating a septic foal can be a challenge. She spoke about the different manifestations and treatment options at the 2011 Western Veterinary Conference, held Feb. 20-24 in Las Vegas, Nev.
A broad spectrum of clinical signs characterize septicemia, Paradis said. Early in the illness a foal might be lethargic, nurse less, exhibit increased heart and respiratory rates, and possibly have a fever. As the infection progresses, he might become depressed and exhibit shock, prolonged capillary refill time, low blood pressure, and a thready pulse (a light that is barely perceptible).
Paradis explained that as the infected blood travels throughout the body, it can--and likely will--manifest in several locations.
"The most common manifestation of septicemia we see is in the respiratory system," Paradis said, adding that this is likely because the foal's respiratory system is very vulnerable to infection. Such a manifestation generally presents as pneumonia in equine neonates, an illness that's a major cause of mortality in foals.
Diagnosing septicemia early means the veterinarian can get a head start on effective treatment, but confirming this can be difficult in the respiratory form: "The problem with respiratory involvement is that it can be difficult to recognize," she noted. "Sometimes (in a foal with an infection) you'll just hear normal (lung) sounds. Even with really a severe disease you can have a 'silent lung.' Foals don't give us a hint with a cough or nasal discharge." But in some septic foals, abnormal lung sounds and difficulty breathing generally point toward pneumonia.
Paradis suggested that veterinarians use a combination of blood/gas analysis (i.e., testing oxygen and carbon dioxide levels in the blood), chest X rays, and thoracic ultrasound to determine whether a foal is suffering from septic pneumonia.
Typical treatments for foals suffering from septic pneumonia include systemic antibiotics, intranasal oxygen, and possibly time on a ventilator.
Paradis added that in some cases, veterinarians will perform a type of physical therapy is called coupage, where the chest is percussed with a cupped hand to loosen up the secretion in the lungs.
It's important, Paradis added, to ensure the pneumonia is completely gone before ceasing treatment.
Septic Arthritis and Osteomyelitis
"The second most common manifestation of septicemia we see is foals with septic arthritis," Paradis said. This can present in a variety of joints, she noted, adding that the most common locations she deals with are the stifle, the hock, the carpus (knee), the fetlock, and the shoulder. More than one joint can be affected in a case.
She went on to describe the three different types of septic arthritis that can be found: infection in the synovial (joint) fluid, the physis (growth plate), or the epiphysis (the end of the long bone). The most severe type is that in the epiphysis or physis, commonly referred to as osteomyelitis (bone infection).
Paradis explained that, typically, an affected foal is suddenly lame with fluid swelling of the joint that is commonly mistaken for an injury sustained on account of the mare: "Owners sometimes say their clumsy mare might have bumped the foal, which is why the foal is lame. Sometimes that's the case, but often times the foal has septic arthritis."
Testing fluid from a joint tap in septic arthritis cases reveals large numbers of white blood cells, particularly neutrophils (a type of white blood cell capable of engulfing and destroying bacteria and other disease agents), along with an increased protein level due to inflammation.
Paradis added that veterinarians can diagnose septic arthritis using radiographs, but these images will only reveal a problem if infection has spread to the bone, causing demineralization. She noted that in a study she conducted, she and her colleagues were able to detect septic arthritis on CT scans several days earlier than on radiographs.
As with septic pneumonia, aggressive treatment is necessary to give the foal the best chance of survival. Two techniques that Paradis favors are joint lavage (flushing out the joint, in less severe cases) and regional limb perfusion (in more severe cases), in combination with systemic and intra-articular (joint) antibiotics.
"A joint lavage is important because these foals have a lot of (debris) in their joints," Paradis said.
Regional limb perfusion involves placing a tourniquet on the limb and injecting antibiotic into a vein below the tourniquet. Isolating the blood supply via the tourniquet for a brief period (usually 30 minutes or so) keeps the antibiotic in the lower limb long enough for it to migrate into limb tissues.
Although each horse response to treatment is unique, Paradis said that prognosis for survival is generally fair for foals with septic arthritis: Many are sound enough as adults to lead a productive life, although likely not at the top level of any sport, she added.
Septicemia can also manifest as an umbilical infection, uveitis, or bacterial meningitis, although these are less common.
A foal with an umbilical infection might not show any outward clinical signs (except those of septicemia), but an umbilical abscess develops on occasion. According to Paradis, ultrasonography is the preferred method for diagnosing this manifestation. Treatment includes systemic antibiotics plus or minus surgical removal of internal abscesses. Paradis noted that surgery is not always necessary, as some foals respond well to antibiotics.
A foal with uveitis, or inflammation of the uvea of the eye, caused by septicemia might initially show a sensitivity to light, tearing from the eyes, pupillary contraction, floaters in the eye, and squinting. Paradis said that as the infection progresses, other signs might appear including hypopyon (accumulation of pus in the eye), hyphema (bleeding in the eye), fibrin (a protein in the blood that forms an essential part of blood clots), and cataract formation.
Paradis treats these foals with a steroidal ointment (only if a she confirms the ocular surface is free of ulcers--steroids can cause major problems if there's a break in the surface of the eye, so it's important this type of ointment not be used unless directed by a veterinarian, topical anti-inflammatory ointment, and systemic non-steroidal anti-inflammatory drugs). She added that foals with a large amount of fibrin buildup will likely need an intracameral injection (an injection directly into the eye) of tissue plasminogenase--an enzyme that will break down the fibrin and clear the way for healing. This injection should be administered under anesthesia, she concluded.
Finally, septicemia can manifest as septic meningitis. Paradis said that research indicates only about 10% of septicemic foals will develop meningitis. These foals appear severely depressed and exhibit a stiff neck. Most veterinarians diagnose septic meningitis CSF analysis.
Foals with septic meningitis can also present with seizures, and seizure control is one of the most important aspects of treatment, Paradis said. Systemic antibiotics that can cross from the blood into the central nervous system should be used to treat the bacteria causing the meningitis. Prognosis is guarded for these cases.
Foals can recover and lead a healthy and productive life despite beginning life with septicemia. Paradis noted that time and patience are key in helping the foal recover.
"The course of your foal's disease (can be) like a roller coaster," Paradis says to clients with septic foals. "One day it may have pneumonia, the next diarrhea, and maybe a septic joint or two. We need to work through each manifestation as it comes. Early recognition of the problem is the key to a successful outcome."