NEONATAL SCOURS, ANTIBIOTICS, AND DAIRY CALVES

Calf management practices play a very important role in the health of dairy calves. As a part of antimicrobial stewardship, it is essential for veterinarians to understand the calf management practices that can reduce the need for antibiotics, which in turn may reduce the emergence of antimicrobial drug resistance. This module describes the presentation, treatment, and impact of calf scours, as well as health management practices that can avert or reduce the need for antimicrobial drugs in addressing this disease.

LEARNING OUTCOMES

• Describe the management practices that can prevent scours in calves, such as high-quality colostrum management, sanitation, and proper isolation procedures.
• Explain the proper role of antimicrobial agents in treating calves with scours.

Sections

• Farm Background
• Calf Records
• Physical Exam and Necropsy
• When to Use Antibiotics
• Calf Scours
• Colostrum Management
• Treatment Plant
• Module Summary
• References

It was a busy Tuesday morning at the Dairy Solutions Veterinary Clinic. Dr. Karl, the owner, walked into the office and the receptionist immediately handed him a message from Chuck Erby, a local dairyman. The message said that Chuck wanted to talk to Dr. Karl about a diarrhea (scours) problem in his dairy calves.

Dr. Karl picked up the phone and called Mr. Erby. “Hey Chuck, this is Dr. Karl. I hear you have a scours problem. What’s going on?”

“For the past two weeks I’ve been treating several scouring calves with sulfa tabs and electrolytes," Chuck responded, "with little to no response. Now I've switched to tetracycline pills. To top things off, this morning I had one die and several are looking very sick."

“Sounds like you have your hands full. I'll be out this morning to see what we can do. I’ll probably necropsy the one that died this morning,” Dr. Karl replied and hung up the phone. He grabbed his boots and keys, and then he and Gretchen headed to his truck.

Dr. Karl gave Gretchen an overview of Majestic Farms as they drove to investigate the calf diarrhea problem. Majestic Farms has been a family farm for over 50 years, and Mr. Erby is a longtime client of Dr. Karl. The farm is a small dairy with a 60-cow stanchion barn on 200 acres. In the past few years, Mr. Erby has had some problems with scours among the calves at Majestic Farms, but only a couple of calves have died from it. He has tried various approaches to prevent scours, but little has worked. Despite the history of a scours problem, he has been reluctant to make improvements in his calf management as suggested by Dr. Karl.

KNOWLEDGE CHECK

Calf Management

Currently, all calves receive a bottle of colostrum at birth for at least one feeding and then are placed on milk replacer, which contains antibiotics. Multiple feedings of colostrum are not consistently provided to calves. There is no testing of colostrum to ensure that it is of adequate quality, and no testing of sera from the calves to validate adequate colostrum intake by the calves. Calves are tied to a wall or pen in the barn and receive ad libitum grain, with a coccidiostat added by the manufacturer. Calves are not given milk or milk replacement products after approximately 60 days of age, at which time the calves are placed in group housing.

Scours History

Majestic Farms has had a problem with scours among calves on the farm for the last two to three years, but typically the calves recover to good health. Today, the problem is a renewed concern because of the death of a five-week-old calf. The calf first became ill with scours about two weeks ago and was treated for 10 days with fluids with electrolytes, sulfa tablets, and two injections of tetracycline. When the calf died, Mr. Erby realized he needed help and called Dr. Karl. According to Mr. Erby, 13 of 22 calves born in the last two months have become ill with scours. Mr. Erby treated all 13 calves, but he feels that the antibiotics are not very effective because the symptoms persisted.

Examine the Calf Records: Like most producers, Mr. Erby writes down the calf's number followed by the treatment given.

February

March

April

May

Farm Tour

The farm buildings are original and few changes have been made to the structures. The milk house is small and cluttered with various tools and supplies. The medicine cabinet is packed with various pharmaceutical agents, cleaning solutions and other supplies. The poorly lit and ventilated tie-stall barn houses the 60-cow milking herd. A walkway traverses the middle of the barn and cows are tied facing the walls on each side. Three calves are tied at one end of the tie-stall barn, while 21 calves are in two pens on a manure pack and one end of the barn. Breeding-age heifers and dry cows are located outside in a wet and muddy lot, with a lean-to serving as protection from the weather.

KNOWLEDGE CHECK

Prior to the death of the calf this morning, Mr. Erby had 22 calves less than 60 days of age, of which 13 have already been treated for scours. You perform physical examinations on the four calves that appear the most ill. The other ill calves have scours but do not appear as depressed.

Diagnostic Specimens

Common infectious agents of calf scours include coccidia, coronavirus, Cryptosporidium, Escherichia coli, rotavirus, and Salmonella. Understand that any and all of these agents can cause scours when host immunity is low and environmental conditions create stress and high rates of transmission. These disease agents are mostly opportunistic, in that they are often present on farms with scours problems and also on farms without scours problems. Management and environment are often the factors that are most easily changed to control the disease problem.

KNOWLEDGE CHECK

Necropsy

Dr. Karl says to Gretchen, “Don’t forget about biosecurity. You should not handle live calves after performing a necropsy because you could spread infectious agents from the dead calf to the live ones.”

Necropsy findings

External Examination

• Wet and soiled perineum region
• Dull and rough hair coat
• Thin calf

Internal Examination

• Excessive peritoneal fluid
• Fibrin tags over the intestines
• Intestines were congested and fluid filled
• Mesenteric lymph nodes were enlarged
• Hemorrhages on the mesenteric lymph nodes
• Intestinal contents were fluid to mucoid consistency, with some mucosal shreds and blood in the colon
• All other organs appeared normal

To get a better understanding of what may be going on, the most severely ill calf was humanely euthanized and necropsied.

External Examination

• Wet and soiled perineum region
• Dull and rough hair coat
• Thin calf

Internal Examination

• Excessive peritoneal fluid
• Intestines were congested and fluid filled
• Thickened ileum and colon wall was slightly thickened with hemorrhage on the mucosa
• The bowel felt thick when palpated and the intestinal vessels were congested

Antibiotic Selection

Empirical treatments are experience-based, therapeutic regimens generally administered prior to confirmatory diagnosis. Veterinarians rely on empirical antibiotic treatments when therapy is urgent and cannot wait for laboratory testing, but empirical treatments may fail when the pathogen has gained resistance.

KNOWLEDGE CHECK

Calves with bacteremia are candidates for antibiotic treatment. These calves are generally recognized by persistent systemic signs, such as fever, depression, and lethargy. For example, depressed calves with a temperature above 104.0°F should probably be given an antibiotic. Clinical judgment is needed for deciding when to treat a calf that has a lower temperature. Importantly, calves should be treated with antibiotics only when it is necessary. Unnecessary antibiotic treatment creates a selective pressure for the dissemination of bacteria resistant to that particular antibiotic, and perhaps others that are genetically linked. Resistant bacteria can greatly complicate the treatment of scours.

Anti-inflammatory drugs

Banamine® can reduce fever and inflammation in calves and is indicated in cases with endotoxemia.

Fluids

Determine the amount of dehydration before administering fluids. Dehydration in a calf can be estimated by using a “skin tent” technique, assessing the appearance of the eye of the calf, and determining whether or not the calf is alert and has a suckling response. The skin tent technique is done by pinching and releasing the skin in the neck area and estimating the number of seconds it takes for the skin to return to normal. The appearance of the eye is assessed as normal or depressed (e.g., enopthalmia).

Fluid Administration

If the calf has mild dehydration (5 percent or less dehydrated), fluids for rehydration can be administered orally or systemically (subcutaneously or intravenously). Fluids should be administered systemically if the calf has moderate or severe dehydration. After determining the administration route for rehydration therapy, decide what type of fluids to use for rehydration.

If the calf has mild dehydration (5 percent or less dehydrated), fluids for rehydration can be administered orally or systemically (subcutaneously or intravenously). Fluids should be administered systemically if the calf has moderate or severe dehydration. After determining the administration route for rehydration therapy, decide what type of fluids to use for rehydration.

Choosing the appropriate fluid for rehydration is determined according to the estimated osmolality and concentrations of sodium and potassium in the calf's serum. Lactated Ringer's, which best matches the electrolyte content, pH, and osmolality of serum, is the best choice for rehydration (when analysis of serum electrolytes are not available). Oral electrolyte solution is an excellent choice if the animal is less than 8 percent dehydrated and has a good suckling response. Electrolyte solutions contain sodium, potassium, chloride, bicarbonate, glucose, and glycine, and the majority have an alkalinizing ability.

KNOWLEDGE CHECK

The three calves on this farm are given systemic rehydration and they perk up somewhat after receiving these replacement fluids. You decide to wait until the culture results are back to determine whether antibiotics are necessary. As for the other calves that are ill with scours, it is best not to treat them with antibiotics since they are not depressed or dehydrated. Each calf should be monitored for any changes in clinical signs.

A recent study found that a treatment algorithm for calf diarrhea reduces antibiotic use in diarrheic calves by 80 percent, with no impact on calf health.¹

There are four treatment pathways after diarrhea is noted, all based on clinical signs and mentation. Diarrhea is defined as loose feces that stays on top of bedding or watery feces that slits through bedding. The first pathway is a dashed line that leads right to hematochezia and requires treatment of OES, NSAIDs, and antimicrobial agents.

The second pathway is used if the calf is BAR and drinking well, which requires monitoring of demeanor and milk intake.

The third pathway is used if the calf is dull, drinking slowly or <30% than expected. If there is a fever you administer OES, NSAIDs, and antimicrobial agents, but if there is not a fever, then you give OES, NSAIDs, and monitor demeanor.

The last pathway is used if the calf is markedly depressed and drinking <50% of expected or completely off feed. If there is a fever then you treat with OES or IV fluids, NSAIDs, and antimicrobial agents; if there is not fever then treatment involves OES or IV fluids, NSAIDs, monitoring demeanor, and treatment 12 hours later.

Recommended algorithm for treatment of diarrhoea in calves <30 days of age

If needed, administer oral electrolyte solution (OES) by tubing.

BAR (bright, alert and responsive); NSAIDs, nonsteroidal anti-inflammatory drugs; IV, intravenous; °T, temperature.¹

• Can be economically devastating to a producer
• Increased morbidity and mortality of calves
• Decreased growth of calves
• Typically involve opportunistic pathogens
• Opportunistic infections are usually caused by organisms that typically do not cause disease in healthy animals, but affect animals with a suppressed immune system
• You can rarely diagnose a causative agent without clinical laboratory support
• Remember that cases, or even healthy animals, may have two or more opportunistic pathogens diagnosed

Biosecurity

• Use management procedures to prevent disease transmission
• Handle calves by moving from youngest calves first, and working your way toward the oldest calves
• Handle calves by moving from healthy calves to sick calves

• Wear gloves when examining sick calves
• Locate calf barns away from human and cow traffic
• Minimize the number of people who go through the calf barn
• Isolate the sick calves from all other animals

Fluid Therapy

• Remember that diarrhea typically leads to metabolic acidosis and electrolyte imbalances
• Types of fluids used:
• If analysis of serum electrolytes is not available, choose a fluid that has similar electrolyte content, pH, and osmolality as does the body’s serum, e.g., lactated Ringer's solution
• If analysis of serum electrolytes is available, choose the fluid type based on the sodium and potassium concentrations
• Sodium concentration:
• If sodium is normal, a balanced isotonic electrolyte solution for volume replacement should be used, e.g., NaCl
• If sodium is decreased, a 0.9 percent isotonic saline solution should be used
• If sodium is increased, a 2.5 percent dextrose in half-strength lactated Ringer's or saline, 0.45 percent saline, or 5 percent dextrose in water should be used
• Potassium concentration
• If potassium is normal, a balanced electrolyte solution should be used, e.g., NaCl
• If potassium is decreased, lactated Ringer's should be used
• If potassium is increased, 0.9 percent saline should be used

• Routes of administration

• Oral

• Excellent for mild dehydration (5 percent dehydrated or less)

• Subcutaneous

• Used to deliver fluids over an extended time for mild dehydration
• May be used with mild or moderate dehydration (8 percent dehydrated or less)

• Intravenous

• May be used for moderate dehydration (8 percent dehydrated or less)
• Used for severe or critical dehydration (greater than 8 percent dehydrated)

Discussion with Client

Dr. Karl has sufficiently assessed the situation on the farm. He has collected specimens (blood and fecal matter) from three sick calves and specimens (fecal matter, intestinal contents, sections of large and small bowel, and mesenteric lymph nodes) from the two dead calves. He will submit these specimens to his state veterinary diagnostic laboratory.

Before leaving the farm, Dr. Karl instructs Mr. Erby to give one liter of lactated Ringer's solution under the skin (subcutaneously) and two liters of oral electrolytes two hours post-feeding, twice a day, to each of the three affected calves. Dr. Karl explains that these will replace the fluids, electrolytes, and bicarbonate lost with the diarrhea. He leaves Mr. Erby two boxes of oral electrolytes to use for the next few days. Dr. Karl also tells him to keep observing the other scouring calves for any changes in their clinical signs. Since they are not depressed or dehydrated, Dr. Karl thinks it would be best to only monitor these calves at this point.

Mr. Erby may be disappointed that Dr. Karl is not going to give antimicrobial agents to all of the calves with scours. Dr. Karl explains that giving antibiotics when treating an unknown disease could potentially make the situation worse. Empiric therapy with antimicrobial agents is only acceptable when systemic signs are present (fever, depression, lethargy).

Dr. Karl also discusses Mr. Erby's management practices and how they might be updated. He stresses the importance of a good colostrum management program and ensuring that calves receive the highest quality colostrum at birth.

Key components to a colostrum management program

1. Quality: Give high-quality colostrum containing 50 mg/ml of IgG or with a specific gravity of > 1.010 using a colostrometer.
2. Quantity: Give four liters of colostrum at the first feeding to achieve a serum immunoglobulin level of >1000 mg/100 ml, which can be tested 24 hours after feeding using an immunoglobulin snap-test. The snap-test measures the levels of immunoglobulins in the calves' blood.
3. Promptness: Feed colostrum within the first two to six hours of life.
4. Cleanliness: Use fresh colostrum, collected by using clean milking technique and equipment, in order to minimize bacterial contamination.

Laboratory Results

Animal Diagnostic Center
911 Incinerator Road
Big Town, WA 96742-4419
Later, Dr. Karl reviews the following results from the lab.

Submitter

Necropsy Results:

Calf #1 that died prior to Dr. Karl’s arrival:

• Rota/coronavirus ELISA negative
• Histopathology of the tissues is still pending
• Cultured Salmonella from intestines

Calf # 2 that was euthanized after Dr. Karl’s examination:

• Rota/coronavirus ELISA negative
• Histopathology of the tissues still pending

Comments:

• Report Sent: Aug 19
• Likely Pathogens: Crytosporidium and Salmonella

Later in the week, Dr. Karl stops by the farm to see Mr. Erby and to share the diagnostic laboratory results. “Chuck, I am fairly confident that we are dealing with a Cryptosporidium problem on your farm, which is complicated by an occasional Salmonella infection,” Dr. Karl explains. Since both of these agents are zoonotic, Dr. Karl cautions Chuck to use personal protection (e.g., gloves) and good hygiene (e.g., hand washing) when working with the calves.

Dr. Karl continues, “The Salmonella strain isolated from your calves is multidrug resistant. This means that one or more of our antibiotics will not be effective. The resistance of this bacterium may be due, in part, to the previous use of antibiotics. This secondary Salmonella infection was probably the cause of the first calf's death.”

“All right,” says Mr. Erby. “So what do we do to treat these calves and make them feel better?”

With regret Dr. Karl says, “The underlying cause of the scours in your calves is Cryptosporidium. Unfortunately, no specific treatment will eliminate this protozoa. Therefore, the only treatment is supportive therapy, including fluids and oral electrolyte solutions. Furthermore, to control Cryptosporidium and prevent its spread to other calves, management changes are essential, such as isolating sick calves, cleaning the environment, and using an all-in-all-out system for raising calves.

Common Pathogens in Calf Scours

Facts about Cryptosporidium and Cryptosporidiosis

• Caused by protozoan
• Can infect most domestic mammals
  • Found commonly in calves less than four weeks of age
• Zoonotic
  • Outbreaks occur among veterinary caregivers
• Clinical signs in calves:
  • Diarrhea (loose to watery)
  • Tenesmus
  • Blood or mucus in stool
  • Bile color in stool
• High morbidity (>30%), low mortality (<5%)
• Pathogenesis:
  • Invade enterocytes in distal small intestines and large intestines
  • Live just under cell membrane
  • Destroy villi, which can lead to villi fusion
  • Oocyst excystion begins with the first signs of diarrhea, therefore infected animals should be isolated as soon as possible to hinder transmission and prevent shedding and contamination of the environment

Facts about Salmonella

• Typically disease of dairy and veal calves
• Typically causes infection in calves less than four weeks of age
• Zoonotic
• Can be subtyped by serotyping:
  • Common serotypes of cattle include Typhimurium, Newport, and Dublin
• Clinical signs:
  • Depressed
  • Fever
  • Profuse diarrhea
  • Swollen joint(s)
• Low morbidity (<10%), high mortality (>50%)
• Commonly resistant to several antimicrobial agents
• Pathogenesis:
  • Colonize distal small intestine or colon
  • Fimbriae attach to enterocytes
  • Invade and destroy cells
  • Carrier state is possible

Management Recommendations

KNOWLEDGE CHECK

Dr. Karl says, “Do you have any thoughts on improving the management of your calves and heifers?”

As Mr. Erby comes to grips with admitting that changes need to be made on his farm, he goes into great detail about how he has already improved calf housing at the end of the barn. “I have already cleaned it, put lime down, and added fresh bedding. I found a water pipe leaking and have fixed that, so the soil will hopefully dry up. I am going to fence in a yard and try to keep the bedding dry and clean.”

Dr. Karl is pleased to hear Mr. Erby has already made some changes, but he also hopes Chuck realizes that there are still many other things that need to be done to improve biosecurity and preventive medicine practices on his farm. Mr. Erby stands by, looking somewhat pleased with his effort, but still confused. ”So… are you going to give me some antibiotics for these little guys, or what?”

Dr. Karl now realizes that he has not communicated as well with Mr. Erby as he thought. "No, Chuck! Antibiotics may be helpful for a few individual sick calves with evidence of systemic infection, such as high fever. Antibiotics are not necessary for the other calves that have scours with no other symptoms. We have to look to improved management to help them, and try to prevent these types of infections from occurring in the future.”

Mr. Erby sputters, “When is using an antibiotic beneficial and necessary?”

Dr. Karl explains that antimicrobial treatments should be reserved for when an animal shows signs of a systemic infection (elevated temperature, off feed/depressed) that is likely due to a bacterial infection. When choosing an antimicrobial treatment, culture and susceptibility testing should be performed to ensure the appropriate antimicrobial treatment is being used. Empiric therapy can be initiated while waiting for laboratory results to come back if systemic signs are present. Oxytetracycline is labeled for the treatment of calf scours.

You are not really helping your client by focusing on which antimicrobial treatment(s) to use for calves with scours. Calves with diarrhea die from dehydration, electrolyte loss, and metabolic acidosis. Fluid and electrolyte replacement should be the mainstay of treatment for diarrhea. The ultimate solution for calf scours lies in preventive medicine, specifically in improving management practices.

As of November 2017, the Centers for Disease Control and Prevention are investigating an ongoing 2-year, 15-state outbreak of multidrug-resistant Salmonella Heidelberg infections in people linked to sick dairy calves.

Follow this link for more information: https://www.cdc.gov/salmonella/heidelberg-11-16/index.html

• Short-term treatment and control of scours is often difficult. Antimicrobials should only be used for scours when an individual calf is showing signs of a systemic infection. Rehydration is the most effective treatment for scours.
• Proper management can go a long way to control scours (clean maternity pens, quality colostrum management, good milk replacer, individual isolated hutches, proper vaccinations, good biosecurity measures, and isolation of new or sick animals). The quality and quantity of colostrum given within the first six hours of birth is crucial to getting calves off to a good start. Have a high-quality colostrum management program and place the calf in a clean, stress-free environment to reduce the likelihood of them becoming sick and needing antimicrobial treatments.
• By following these guidelines, you will be providing the calves with a clean, low-stress environment and adequate nutrition to fight off opportunistic infections when they occur.
• Keys to preventing scours in calves:
  • Employ an excellent colostrum management program.
  • Cleanliness is essential in maternity pens, hutches and calf stalls.
  • Caretakers must employ proper hygiene to prevent transmission among calves.
  • Provide an adequate level of nutrition in milk replacer and grain.
  • Fresh clean water should always be available.
  • Reduce stress and transmission with a comfortable environment—spacious, dry, clean, and ventilated.
  • Employ consistency in caretaker duties and feeding schedules.
  • Use an appropriate vaccination program for calves.
  • Regulate the traffic flow—very few people need access to the calf-raising area. When examining or caring for calves, reduce transmission of disease agents by moving from young to old and from healthy to ill.

1. Gomez, Diego E., Luis G. Arroyo, Zvonimir Poljak, Laurent Viel, and J. Scott Weese. "Implementation of an algorithm for selection of antimicrobial therapy for diarrhoeic calves: Impact on antimicrobial treatment rates, health and faecal microbiota." The Veterinary Journal 226 (2017): 15-25.