Septicemia is a systemic disease associated with the presence and persistence of bacteria and their toxins in the blood eventually leading to septic shock. The word septicemia literally means bacterial invasion of the blood, and it arises from a seat of infection somewhere in the body. Once a local infection opens the door for bacteria to enter the bloodstream, they travel throughout the body. This widens the circle of infection and tissue damage.
For instance, infection of the navel (umbilicus) facilitates the movement of bacteria into the blood, which then relocate to the lung causing pneumonia. Bacteria also release toxins (chemical poisons) that cause further complications, on their own. Thus, septicemia is a complex process initiated by bacterial infection and perpetuated by the spread of those bacteria and toxins to cause dysfunction and even failure of multiple organs, including the kidneys, liver, joints and lungs.
Septicemia is an important disease of neonatal (less than 14 days of age) foals. Thirty-three percent of neonatal deaths can be attributed to septicemia. In one study of 160 neonatal foals hospitalized for various reasons, septicemia was the second most common problem diagnosed. It was surpassed only by the problem of inadequate transfer of maternal antibodies from the dam's colostrum.
The foal can be exposed to bacteria in many ways. The exposure may take place while the foal is still in the mare's uterus. This is generally a consequence of the mare developing an infection of the placenta near the end of her pregnancy. Infection can also come through the blood of the mare to the fetus if the mare is severely ill (e.g. with septicemia) before birth or parturition. The foal can also get infected when exiting the birth canal. Infections that occur after the foal is born are commonly promoted by failure of the foal to get antibodies from the mare. This is called failure of passive transfer. The bacteria gain entry to the foal by inhalation, ingestion, and contamination of the umbilical stump and through wounds.
The clinical signs of septicemia are variable. They range the full spectrum from mild depression to shock and death. It is often difficult to identify the foal in the beginning of the illness. Early identification is essential in the prevention of the progression of the problem into irreversible shock. Foals usually start out with mild to moderate depression, decreased suckling frequency, and sleepiness, loss of energy, or weakness.
Because the bacteria are in the bloodstream, they can travel and settle in various organ systems causing local system infection or failure. One foal may have more than one system affected at the same time. Some of the body systems that are most affected include the following:
What to Watch For
It is not difficult to diagnose the foal that is in septic shock. These young animals are generally severely depressed to comatose. Their legs are cold and it is difficult to find a pulse. The challenge comes in diagnosing foals that are only beginning to show subtle signs of depression. Early signs include:
To recognize the early stages of sepsis, your veterinarian will attempt to get clues from a thorough perinatal history, that period shortly before and after birth, and a physical examination. This information is supplemented with some blood work, which will include a complete blood count, a serum immunoglobulin level and blood glucose. Additional blood work that is helpful if available is a blood culture, an arterial blood gas analysis, serum electrolytes and chest radiographs.
Once septicemia is suspected then treatment should start immediately. Care can be quite intensive and may require that the foal be sent to a hospital that has the ability to monitor the foal 24 hours a day. The general treatment of a septic foal should include:
Home Care and Prevention
Home care begins with prevention of septicemia. Because the largest risk factor for the development of septicemia is failure of passive transfer, owners should be extremely observant of the late pregnant mares. Any leakage of milk from the udder before the foal is born is cause for concern. High quality colostrum gives the newborn foal the tools to fight most normal bacterial contamination at birth.
It is important for owners to be present at the time of foaling as well. The mare may have excellent colostrum, but if the foal does not stand and nurse within three hours of foaling, the bacteria will have a chance of establishing residence before the foal has a chance to build his defenses. At the time of foaling, owners should disinfect the foal's umbilicus. The umbilicus can be a portal of entry to the environmental bacteria. Because ingestion is also a way that bacteria can invade a foal's systems, cleaning of the mare's udder and hind legs with a light disinfectant or soap may reduce the number of bacteria that the foal's are exposed to at birth.
Next to prevention, early recognition of septicemia is the next best thing that owners can do. The first sign of a bacterial infection in a foal may be that he is not as active as other foals. You may see him lying down more than he should. The mare's udder may be distended indicating that he is not drinking as much milk as he should. If you have any concerns about the health or behavior of the foal, insist that your veterinarian check the foal out as soon as possible. Septicemia is an emergency.
The most common cause of equine neonatal deaths is bacterial infection. Bacterial infection can be local such as an infected wound or it can be widespread throughout the body. When it is widespread in the body is usually called septicemia or sepsis and is generally spread through the bloodstream. Some bacteria also release toxins into the blood that can lead to a deterioration of the foal's condition. The causative bacteria are bacteria normally found in the environment. These same bacteria will not cause a problem if the foal receives good quality colostrum from the mare within three hours of birth. It is the unprotected foal that is at highest risk for septicemia.
The bacteria can enter the foal's body through several portals. Exposure may take place while the foal is still in the mare's uterus. This is generally a consequence of the mare developing a placentitis (infection of the placenta) near the end of her pregnancy. Infection can also come through the blood of the mare to the fetus if the mare is severely ill before parturition (birth).
Infections that occur after the foal is born are commonly associated with the problem of failure of passive transfer of maternal antibodies to the foal. The bacteria can gain entry to the foal by inhalation of infective particles, such as dust, or ingestion – in the foal's attempt to find the mare's udder, it suckles on the walls of the stall, buckets, and other parts of the mare's body. Unsanitary conditions will increase the number of bacteria that the foal ingests. Remember the foal is ingesting these bacteria before he has ingested his colostrum, and the same mechanism that facilitates the foal's absorption of the antibodies from the intestinal tract will facilitate the absorption of bacteria.
An infection of the umbilical structures can lead to the circulation of bacteria in the bloodstream and hence septicemia. These structures include two umbilical arteries, one umbilical vein and the remnant of the connection between the bladder and the allantoic sac in the fetus. The bacteria can infect one or all of these structures, forming an abscess. This type of infection is not visible on the external body wall. An ultrasound examination of the structures is needed to discover a problem here.
The most common bacteria isolated from septic foals is Eshericha coli (E. coli). Others that may be involved include Klebiella, Enterobacter, Actinobacillus, Salmonella and Streptococcus. Approximately half of the foals with sepsis are infected by a single organism and half are infected with multiple organisms. Some of the bacteria mentioned above contain a toxin in their cell walls that is called endotoxin. When endotoxin is released into the blood stream it causes the release of other chemicals in the body called cytokines. These cytokines cause the symptoms of depression, anorexia and fever.
The clinical signs of sepsis vary depending on the amount of colostrum the foal has received, the number and type of causative bacteria, and whether the foal was infected in the uterus or after birth. The earliest sign may be that the foal is slightly depressed or doesn't act as lively as other foals. This progresses to a foal that is not eating.
The severe signs may include
The reason that so many body systems can be involved either singularly or in multiples in the same foal, is that the bacteria are carried by the blood stream. This allows infection of any body system where blood flows, which means everywhere. The final stage of sepsis is shock, where the body is overwhelmed. Blood pressure drops, gums become either bright red or pale, the foals are unconscious and finally they go into cardiac and respiratory arrest.
It is not difficult to diagnose the foal that is in septic shock. The challenge comes in diagnosing foals that are only beginning to show subtle signs of depression. Because there are other causes of depression in foals, and septicemia requires special treatments, it is important to distinguish septicemia.
Dr. Anne Korterba, University of Florida, developed a scoring system in the early 1980s. This is a tool that veterinarians use to assess the likelihood of a foal being septic. Information needed for using this scoring tool includes a good perinatal history, physical examination findings and some blood work, which includes a complete blood count, a serum immunoglobulin level and blood glucose. The common results from these tests in septic foals are a low white blood cell count, a low immunoglobulin level (less than 400 mg/dl) and low blood glucose. The foal receives a numeric score for these abnormalities. Scores that are over 11 are highly suspicious of being septic. This system allows early detection of septicemia before foals develop irreversible problems.
Other diagnostic procedures include:
Once septicemia is suspected, treatment should start immediately. The general treatment of a septic foal is outlined below. Depending on which body system is affected, there is system specific therapy that needs to be started. Care can be quite intensive and may require that the foal be admitted to a hospital that has the ability to monitor the foal 24 hours a day.
System Specific Therapy
Before 1980, equine neonatal intensive care did not exist as a field of study. The philosophy of neonatal care was "survival of the fittest." It was generally accepted that sick foals would not grow up to be useful adults. The first decade of equine neonatal intensive care was characterized by a steep learning curve for the veterinarian. The increasing knowledge base and case management skills improved the prognosis of the septic foal from 25 percent to 75 percent survival that we see today.
Follow-up surveys of the survivors of neonatal septicemia demonstrate that the long-term prognosis for septic foals is often good. Owners have indicated that their foals become healthy adults that are comparable to their stablemates in weight, height, soundness and athletic ability. Foals that would have died 20 years ago, go on to become successful race horses and breeding animals. Currently ongoing studies exist that aim to determine the fate of foals surviving neonatal intensive care.
Although our increased knowledge in the treatment of neonatal sepsis has brought about these improved survival rates, sepsis is still one of the most difficult problems we face in neonatal medicine. Owners often feel like they are on an emotional roller coaster because the foal's condition can change rapidly. One day the foal has diarrhea, the next day he has developed infected joints and the third day he needs surgery to have his umbilicus removed.
Each of these problems must be taken care of one at a time. Care remains costly and labor intensive and can range from $2,500 to $5,000 for a 5 day stay in an intensive care facility. The very sick foal may have an attendant with them 24 hours a day. It is important the veterinarian, hospital staff and owner be committed to the care of the septic foal if the outcome is to be favorable.