Equine Neonatal Septicemia

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Equine Neonatal Septicemia

By: Dr. Mary Rose Paradis

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Section: Information In-depth

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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.

Risk Factors

Failure of passive transfer of colostral antibodies

Unhygienic environment

Severe exposure to cold

Advanced age of the dam

Pre-maturity (born too soon)

Post-

maturity (born late, prolonged pregnancy)

Poor health of the dam

Presence of foreign bacteria

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

Recumbency

Hypothermia

Increased respiratory rate and effort

Diarrhea

Seizures

Swollen joints

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.

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