With the breeding season now upon us, the paddocks will soon be filled with bouncing happy, healthy foals. The birth of a new foal is usually a very emotional time for owners, as the arrival of the newest member of the equine family often brings with it huge expectations and dreams of future successes. Sadly, for some, the joys of a new foal are short-lived when within hours to even days or weeks the foal becomes ill and dreams are shattered, and the overwhelming concern becomes whether the foal will live or die.
Septicaemia is an infection caused by the presence of bacteria or small microorganisms in the bloodstream that can trigger a response by the body’s immune system, resulting in sepsis. Sepsis occurs when the body releases chemicals into the bloodstream in response to the infection. These chemicals bring about a deluge of inflammatory reactions in multiple organs of the body that can be so profound they lead to multi-organ failure and death. It is one of the major causes of deaths in foals.
Neonatal (newborn) foals are particularly vulnerable to septicaemia as they are born with little or no protection from bacterial invasion. Foals rely on the mare’s colostrum to get enough immunoglobulins, amongst other factors, to protect them for the first few months of life, by which time their immune system is mature enough to develop their own antibodies. A foal that does not receive enough colostrum at birth – termed “Failure of Passive Transport” (FPT), is at a higher risk of developing septicaemia than a “normal” foal. There are two major reasons for FPT to occur in a foal; one being the mare doesn’t have the colostrum to give the foal, and the other being the foal doesn’t drink sufficient colostrum within 24 hours of being born.
If we look at the maternal causes, the mare not providing enough colostrum, this occurs if the colostrum is lost before the foal suckles or if the mare does not produce enough good quality colostrum. This is a common scenario seen in mares that run milk for several days before the foal is born (premature lactation). Colostrum is only produced once per pregnancy, and once made there is no opportunity for more to be produced. The mare begins to produce immunoglobulins in the two to four weeks before foaling but selectively accumulates these immunoglobulins into the mammary gland, in the form of colostrum, in the final five days before birth. In cases where the mare runs milk before the foal is born, it is the colostrum that is lost first, leaving only milk for the foal to consume. The other causes of FPT are due to foal causes and include the foal’s failure to drink enough colostrum due to an injury or illness, or the foal’s failure to absorb the colostrum from its intestinal tract due to an intestinal disturbance.
BLOOD TEST
A foal can only absorb the immunoglobulins from its gut for the first 18-24 hours of life; after this time, the specialised cells that allow absorption of these large complexes through the gut wall and into the blood stream disappear. Therefore, it is imperative that any foal delivered from a mare that has run milk, or any foal that has had any difficulties in drinking in the first 24 hours of life, should have a blood test performed to check if FPT has occurred. This blood test can be performed via a few different methods but is commonly referred to as an IgG test. The level of IgG in the foal’s system is determined and foals having FPT (<400mg/dl IgG) or partial FPT (400-800mg/dl), can be identified as high or moderate-risk candidates for septicaemia and other associated illnesses.
If a low or negligible amount of IgG is detected, it is strongly recommended that a supplementary source of IgG be given to the foal to help reduce the risk of the foal becoming septic. This is usually done using hyperimmune plasma that is available commercially and given intravenously. In cases where a low IgG is predicted based on the mare’s history (previous foals, running milk before the birth), it is advisable to access colostrum from another mare to give the foal orally (or via a stomach drench) within the first 24 hours of life. Many larger studs have a bank of frozen colostrum available for use in foals that are at risk of not obtaining enough colostrum for reasons already discussed. In healthy mares that have had a normal pregnancy with no history of having lost colostrum pre-foaling, about a cup of colostrum-rich milk can be milked and banked in a freezer without compromising the safety of the newborn foal.
An IgG test can be performed any time after 8 hours from birth, although it is common to wait until after 18 hours to allow every opportunity for the level to be above 800mg/dl. I often perform this test in the window between 8-18 hours, particularly if I know the foal has behaved normally from birth and had several hours of good drinking before the blood is taken. These IgG results in normal healthy foals are frequently over 800mg/dl, but in cases where the level is <400mg/dl, I will stomach-tube the foals with additional colostrum, rather than wait to reassess their IgG level after 24 hours and then need to administer IV plasma if the level is still low. Foals with levels between 400-800mg/dl should be retested after 24 hours, as the level will continue to rise as further colostrum is ingested and absorbed.
Bacteria can gain access into the foal’s system several ways, including via the gastrointestinal system, through the umbilical cord, the respiratory system and via skin wounds. In some circumstances, the foals are born septic due to bacteria gaining access through the mare’s placenta. Infection via the gastrointestinal tract is not surprising if you watch a foal in the first few hours after birth. A healthy foal has a strong suckle reflex at birth and will suck on anything and everything as it searches for the udder. The proximity of the udder to the perineum, where placental fluid and faecal contamination is often high due to the birthing process, increases the bacterial load a foal may ingest as it searches the hindquarters of the mare for the udder.
“The early signs of sepsis can be subtle.”
CLEAN ENVIRONMENT
Foals born in less-than-ideal hygienic environments are at bigger risk of bacterial infections due to the increased levels of bacteria that can be ingested or invade the umbilicus. Therefore, anyone foaling down their mare should be conscious of providing a clean environment for the newborn as well as practise good hygiene when handling the mare and foal. Mares with a history of delivering septic foals or having foals become septic shortly after birth, should be washed around the perineum and udder after the birth, to remove faeces and foetal fluids that may contain harmful bacteria before the foal starts to suckle.
The early signs of sepsis can be subtle but can progress quickly, often presenting as a depressed recumbent foal, requiring immediate veterinary intervention. Clinical signs include lethargy, depression, loss of suckle reflex or not drinking, sunken eyes, diarrhoea, poor regulation of body temperature (so hyperthermia and hypothermia), petechia (pinpoint haemorrhages visible in the membranes), weakness and prolonged periods of lying down. Depending on the organs and systems involved, other clinical signs can include coma, seizures, pneumonia, and lameness. Often, one of the earliest indications that there is something amiss with the foal, is the mare’s udder is distended and the mare is uncomfortable, or even dripping/running milk. A swollen and distended udder should always alert an owner that there is a problem; it may not be sepsis but close attention should be paid to the foal’s health, as it is vital to identify any signs of illness that has decreased the foal’s milk intake. If sepsis is recognised and treated promptly, it can be resolved before a major issue ensues.
For those foals that are born with septicaemia, the clinical signs may be a little harder to identify. The foal will be slow to stand (normally they stand within the hour), the suckle reflex will be reduced or absent and the foal will be lethargic. These symptoms are not specific to sepsis and can be seen with several foal diseases. For this reason, a sepsis score chart was developed and is used by vets to help differentiate those foals that are septic from those foals that have other illnesses that required a different treatment plan. It is predominantly used in referral hospitals and relies on blood tests, clinical examination, and historical data to acquire a score and then uses the total score to predict the likelihood that the foal has sepsis.
Septic foals that are identified and treated promptly have a much better prognosis for survival than those that are left for days without any intervention. Ideally, foals with sepsis would have a blood sample taken and cultured to identify the offending bacteria and select the best antibiotic before any treatment is administered. However, the success rate of growing a bacterium from the blood is not very high and it generally takes 2-3 days before a result is achieved. Therefore, a broad-spectrum antibiotic or combination of antibiotics is used initially and then, if necessary, changed to a more specific antibiotic if the blood culture is successful and identifies a superior medication, or if the foal fails to respond to the initial course of antibiotics.
FLUID THERAPY
Fluid therapy is generally essential for any foal with sepsis as foals quickly become dehydrated, as the demand for fluid, especially in a neonatal foal, is higher relative to their size. Foals have a higher surface area to body weight and a higher respiratory rate than adults, increasing their fluid losses relative to adults. Foals also have a high urinary output and if diarrhoea accompanies the sepsis, the rate of dehydration can be rapid and fatal. Fluid is often replaced via an intravenous drip, using a balanced electrolyte that is titrated according to the foal’s needs. The IV drip may contain glucose as well, especially in neonates, as foals have very little energy reserves and bacteria increase the demand that is required for glucose. If foals are not given glucose or a similar energy source when septic, they quickly lose weight and become weak and unable to function.
Depending on the status of the gut, milk may or may not be given to the foal as a source of nutrition. Foals with mild sepsis can often receive milk via an indwelling nasogastric tube. If there is evidence the gut is not functioning correctly (little or no gut motility), or diarrhoea is present, then feeding milk is not a viable option. Instead, parenteral nutrition may be required, especially if the foal has gone more than 48 hours without being able to drink around 10% of their body weight in milk. Parenteral nutrition is the term for providing the nutritional requirements to an animal via the intravenous route. These are typically centred on providing glucose, amino acids, and lipids at a level calculated to provide the required kilojoules to maintain and increase the foal’s body weight. Having a foal on total parenteral nutrition is an expensive exercise and is usually done in a hospital environment, as these foals often require intensive care nursing and access to frequent laboratory monitoring.
Other medications used for septic foals are often related to specific clinical symptoms that are present because of the body organs involved in the sepsis process. Foals showing diarrhoea can be given anti-ulcer medications such as omeprazole and sucralfate to protect the gut from gastric ulceration. In foals with seizures, an anticonvulsant such as diazepam (Valium) may be used. In foals displaying signs of pain, particularly abdominal pain, a NSAID (nonsteroidal anti-inflammatory drug) with selective COX-2 inhibition (meloxicam) can be given, as this is less harmful to the foal than the more commonly known NSAIDs, phenylbutazone or flunixin.
In septic foals, the bacteria can spread via the bloodstream (haematogenous spread) and localise in one or more joints, causing an infection in the joint colloquially called “joint ill”. This can be devastating to many owners as the foal becomes significantly lame, sometimes non-weight bearing lame, which is traumatic to see by the owner and requires prompt, aggressive therapy to minimise the destruction in the joint and maximise the chance of a full recovery so the horse can fulfil the role it has been born into as an adult horse. EQ
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