Escherichia Coli Infection in Young Calves

Also known as

Enterotoxigenic Escherichia coli (ETEC),  Septicemic Colibacillosis

Description

Escherichia coli is a bacterium that occurs commonly in the environment and in the digestive tracst of animals and humans. There are many different strains, some of which are non-pathogenic and some that cause disease, especially in young animals. Since these bacteria are common in manure, young calves born in crowded conditions are extremely susceptible. They may pick up these pathogens soon after birth if they are born in a dirty pen, barn stall or pasture contaminated with manure, or if they nurse a dirty udder or lie in manure and then lick themselves.

There are basically 2 forms of Escherichia coli disease in calves, possibly caused by different strains. The enteric form involves the digestive tract, damaging the intestinal lining and causing acute diarrhea. This most commonly occurs in calves less than 3 days old. Since a young calf dehydrates quickly, severe diarrhea may be fatal within a short time unless treated swiftly--with frequent administration of fluid and electrolytes.  

The enteric form of this infection usually appears in the first week of life. The calf has moderate fever but the first sign noticed is diarrhea. He quits nursing and may also have abdominal pain. Dehydration occurs quickly, due to fluid loss from watery diarrhea. Without treatment, the calf soon becomes weak and usually slips into a coma and dies within 2 to 5 days. Most calves that are affected get sick within 12 to 48 hours of birth.

The other form of Escherichia coli infection causes acute septicemia rather than diarrhea. In calves that develop septicemia, the disease may be so acute that the animal dies before there’s much sign of diarrhea, or may become extremely weak and wobbly after a short bout of diarrhea. The toxins circulating through the bloodstream attack various organs, and unless quickly reversed with proper treatment, the calf goes into shock and dies.

Signs

• Acute diarrhea in very young calves
• Signs of shock and dehydration

Cause

E. coli is probably the single most important cause of severe bacterial scours in young calves. Diarrhea caused by enterotoxigenic Escherichia coli occurs during the first few days of life.

There are numerous kinds of E. coli. Research indicates that the majority of E. coli strains that are able to cause diarrhea can colonize in the intestine, adhering to the gut lining by means of tiny hair-like protrusions known as pili. These pili utilize the K99 antigen. E. coli strains possessing the K99 antigen are called enterotoxigenic E. coli (ETEC).

Enterotoxigenic simply means ability to produce toxins in the intestines. Some ETEC have a different type of pili known as the K88 antigen. Some other features of scour-causing E. coli are known as “capsular antigens,” but the K99 antigen is the most common characteristic of ETEC.

These bacteria colonize the small intestine and produce an enterotoxin that invades and destroys the deeper layers of the intestinal lining, causing release of blood and mucus, and excessive secretion of fluid—pulling fluid from the bloodstream into the intestine and causing diarrhea and dehydration.

These enterotoxigenic Escherichia coli are shed into the environment via feces of infected animals in the herd (often mature animals that have immunity and are not sick) and ingested by newborn calves soon after birth. Cattle have some natural immunity to enterotoxigenic Escherichia coli but this immunity often fails to protect calves born and raised in confined, contaminated areas.

Severe outbreaks of diarrhea caused by E. coli may affect calves as young as 12 hours of age. The younger the calves, the greater the risk for death from progressive, severe dehydration.

The K99 strain of Escherichia coli causes diarrhea by impairing ability of the intestinal lining to digest and absorb milk nutrients. This K99 strain, however, is only capable of causing scours in calves less a week old. After that, the calf’s intestine becomes resistant to its effects.

In other instances, certain strains of these bacteria proliferate in the gut and damage the intestinal wall, enabling the bacteria and their toxins to move through it and into the bloodstream, producing septicemia--which can also kill a calf quickly. This acute and highly fatal infection can kill calves up to several weeks of age.

This problem is called sepeticemic colibacillosis and is caused by another serotype of ETEC. This is an acute disease with very few diagnostic signs (the calf often dies before signs are noticed). This is one of the most common causes of acute, fatal illness in young calves.

Depressed, weak animals initially have a fever but become hypothermic (subnormal temperature) rapidly as they go into shock. Mortality rates are high and survivors are often affected by localization of infection in other parts of the body, such as the joints (arthritis/joint ill), the brain (meningitis) or the lungs (pneumonia). Inadequate transfer of passive immunity from the dam is considered the main risk factor for colibacillosis.

Calf scours are often caused by two or more pathogens working together. The severity and duration of diarrhea is related to the number (dose) of each pathogen involved, and the extent of intestinal destruction or malfunction created by each pathogen; their effects are cumulative Different strains of each pathogen differ in their capacity to induce severe disease.

Severity of disease also depends on amount and quality of colostrum consumed by the calf (how much protection the calf received). The severity of other stresses (wet, cold, weather, inadequate nutrition, or deficiencies of certain trace minerals or vitamins) can also play a role.

The fluids lost through diarrhea quickly deplete the calf’s reserves of water and salts, producing signs of dehydration--sunken eyes, weakness, dry mucous membranes in nose and mouth. As the calf loses body fluid through diarrhea, blood volume drops, making it harder for the heart to deliver blood to the body, and the calf’s extremities become cold.

The loss of salts via diarrhea creates an imbalance in the normal pH of the calf’s body, causing acidosis. As a result, these calves become weak and uncoordinated, with a drunken, wobbly gait if they try to walk. Suckle response is poor--often just a weak chewing motion. As acidosis worsens, the calf is lethargic and can no longer stand up.

Advanced cases become comatose. The function of the heart and lungs is greatly impaired due to acidosis, and many advanced cases die of cardiac arrest and shock if they are not treated in time to reverse the condition.

Prevention

Prevention involves having clean areas for calving, clean uncrowded pastures for cows with young calves, and making sure every calf receives an adequate amount of colostrum within the first hour of life. Older animals have developed resistance to E. coli; the cow has protective antibodies in her colostrum that she passes to her calf if he nurses soon after he’s born.

Some types of E. coli infection that affect calves early in life can be prevented by vaccinating the cow ahead of calving, so her antibody levels are high. The protective antibodies are transferred passively to calves through the colostrum.

This will only help, however, if the calf gets a full nursing of colostrum soon after birth.  There are commercial antibody products that can be given orally to newborn calves, but these must be given immediately after birth to be effective (before the calf encounters the pathogens in his environment), and they only protect against a few strains of E. coli.

Clean calving areas minimizes exposure. There are numerous ways to improve sanitation, which include cleaning barn stalls and pens between occupancy (and adding new, clean bedding), sanitizing calf treatment equipment between uses and isolating scouring calves from the rest of the herd.

Make sure the calf gets enough colostrum. This is the single most important way to improve the calf’s immune status. Calves that don’t get adequate colostrum have a 3 to 10-fold increase in risk of becoming sick. Proper cow vaccination against E.coli and rotavirus and coronavirus can increase the antibodies she passes through her colostrum to the calf.

Even if you vaccinate the cows and make sure calves nurse promptly, if the environment in which the calves are born is heavily loaded with scours pathogens, this can overwhelm the calf’s immunity and scours will still occur.

Treatment

Treatment of scouring calves involves correcting fluid deficit and electrolyte imbalance.

The key to proper therapy is to understand the magnitude of fluid loss. A 100-pound calf that is 10% dehydrated needs 10 pounds of fluids to just correct the immediate deficit. A gallon of fluid weighs 8 pounds, so the calf needs about 1.25 gals.

Giving a calf 2 quarts of fluid orally (by stomach tube or esophageal feeder probe) two to four times a day is often necessary to correct and maintain fluids. In cases of severe diarrhea in very young calves, fluid may need to be administered every 4 hours until the calf starts to recover.

Most calves with diarrhea will be acidotic. Oral electrolyte solutions with an alkalinizing agent such as bicarbonate are necessary to correct this imbalance. Read labels to choose products that contain bicarbonate.

Severe dehydration (in which the calf is too acidotic—and in shock, unable to stand) cannot be corrected with oral fluids because there is not enough blood circulation to the gut for adequate fluid absorption.

Fluid treatment is usually successful if begun early, before the calf is dehydrated, weak, or in shock. Immediate administration of oral fluids containing electrolyte salts can be given if the calf is still on his feet, able to absorb fluids via the digestive tract. Fluid should be given every 4 to 6 hours, depending on age of the calf and seriousness of diarrhea.

If he is too weak to stand or his legs are cold, this means blood circulation to his extremities is already shutting down and his gut is also impaired--too compromised to absorb fluids. If he is this weak, or in shock, he needs intravenous electrolyte fluids.

Antibiotics may also be necessary, in cases of bacterial scours such as E.coli. Consult your veterinarian for proper treatment and appropriate antibiotic. Some of the older medications that worked very well (such as furazolidone) are no longer on the market for scours in young animals and something else must be used.