Septicemia or sepsis (blood infection) is a whole-body disease in which bacteria circulate in the bloodstream. It is most commonly found in very young foals less than 4 weeks of age. Bacteria can spread through the blood to various organs, such as the lungs, intestines, eyes, central nervous system, bones, and joints causing lameness and joint swelling. The condition implies an extensive, whole body infection from single or multiple sources. The most common bacteria identified in septic foals is Escherichia coli (E. coli). Others that may be involved include Klebsiella, Enterobacter, Actinobacillus, Salmonella, Pseudomonas, and Streptococcus species. Some of these bacteria contain a toxin in their cell walls called endotoxin. When endotoxin is released into the bloodstream, or when whole bacteria are present in the blood, it causes the release of other chemicals in the body called cytokines. These cytokines cause the signs of depression, poor appetite, and fever.
The major risk factor for septicemia in foals is the failure to receive an adequate amount of good quality colostrum (the first milk produced by mares, which contains high levels of antibodies) during the first few hours after birth. Other factors that increase the risk of disease include a dirty environment, prematurity at birth (a weak foal), poor health and condition of the dam, a difficult birth, and the presence of disease-causing agents in the environment that the mare has no antibodies against.
A foal with septicemia may show evidence of single or multiple organ dysfunction. The earliest sign may be that the foal is slightly depressed or does not act as lively as other foals. This progresses to a foal that will not eat and lies down frequently. The mare’s udder is often distended with milk, indicating that the foal is not nursing with normal frequency.
In the advanced stage of illness (septic shock), the body becomes overwhelmed. Such foals are often severely depressed and dehydrated, can only rise with assistance, and have a rapid heart rate. Low blood pressure, shown by such signs as cold extremities and a weak pulse, is evident. Foals may have elevated or reduced body temperature. Gums become either bright red or pale. In the final stages, foals become unconscious and go into cardiac and respiratory arrest.
Diagnosis is based in part on a thorough physical examination and medical history. Laboratory tests are required to assess organ function and identify the type of bacteria responsible for the infection.
Foals suspected of being septic are usually given broad-spectrum antibiotics (antibiotics that are effective against a wide range of bacteria) to kill the bacteria causing the infection. In cases of neonatal sepsis, veterinarians often recommend plasma transfusions to help the foal’s immune system by supplying antibodies that were not received in colostrum. In addition, intravenous fluids may be given to help counter the effects of bacterial toxins and infection. Many septic foals have low blood sugar, so a sugar solution is often added to the fluid treatment.
Nutritional support is also important. If the foal is not nursing adequately, it should be fed mare’s milk or a milk substitute at 15 to 25% of its body weight over each 24-hour period. Sometimes, the foal does not tolerate a large volume of milk and must be fed small amounts very frequently. It may be necessary to insert a feeding tube through the nose in foals with a decreased suckle reflex. Foals should never be fed milk by a syringe, because there is a risk of inhaling the milk into the lungs (aspiration).
Other treatments that may be required include flushing out infected joints with sterile fluids and providing nasal oxygen or ventilation for foals with septic pneumonia. Surgical removal of infected umbilical cord remnants may be needed. Eye infections and ulcers on the cornea of the eye are treated with antibiotic and anti-inflammatory eye ointments.
Recovery from neonatal sepsis depends on the severity and form of the infection. Current survival rates are 55 to 75% in equine intensive care units of large veterinary hospitals. An average of 1 to 4 weeks of intensive care should be expected. Early recognition and intensive treatment of foal sepsis improves the outcome. If the foal survives the initial problems, it has the potential of becoming a healthy adult.