Monday, 15 May 2017 10:36

Calf-scour pathogens: Better the devil you know

Written by  Dr Gemma Chuck

Wet, wintery weather often coincides with busy calving periods and an abundance of young and vulnerable calves. A change in weather can exacerbate the environmental challenge of many calf-scour pathogens, resulting in an increase in morbidity at this time of the year.

This article discusses appropriate and timely diagnosis of calf-scour pathogens, allowing the best outcome for both the producer and the calf.

Why is diagnosis important?

There are many pathogens causing calf diarrhoea and these affect calves at different ages. Often multiple pathogens affect an individual calf at the same time.

Common bacteria affecting young calves include E.coli and Salmonella and only these bacterial pathogens will respond to antibiotics.

Viral pathogens, including rotavirus and coronavirus, and protozoa, such as cryptosporidia and coccidia, will not respond to antibiotics.

Therefore it is essential to obtain an accurate and representative diagnosis to avoid unnecessary and inappropriate treatment. Some causes of calf diarrhoea are preventable through vaccination. However, the vaccines are very specific to the pathogen.

For example, this means that a vaccine indicated for the prevention of rotavirus will be ineffective against Salmonella and vice versa.

Accurate diagnosis of calf-scour pathogens allows more effective and targeted treatment. Remember, calves are usually infected with multiple pathogens at the same time and these may require differing treatments and/or preventative strategies.

Removing the guess-work…

Diagnosis of calf-scour pathogens is usually based on faecal analysis or samples at necropsy.

When taking faecal samples, it is important to obtain samples from UNTREATED calves early on in the disease process.

Calves that have already been treated with antibiotics should not be sampled as the antibiotic treatment can interfere with test results.

It is essential that calves are sampled before any treatment and it is useful to keep some sterile sample pots for this purpose.

Despite many calves being infected with multiple pathogens, not all of the causative pathogens will be continually present in the faeces of a scouring calf.

As a result it is prudent to take samples from at least 3 (preferably 6) calves to help isolate all of the causative pathogens and avoid inconclusive results. If only one or two calves are sampled, then pathogens can be missed and calves may appear unresponsive to treatment.

Necropsies should be performed by veterinarians as soon as possible after the calf has died to improve the chance of obtaining representative samples.

Necropsies are best performed early on in the disease process and it may be necessary to perform a sacrificial necropsy to determine the underlying causes.

How to take a faecal sample:

  1. Pre-label the sterile sample pot with a calf ID, age of calf, your name and the date.
  2. Adequate restraint of the calf is required to obtain a sample. An assistant may be necessary.
  3. Wearing disposable gloves, insert your index finger into the rectum of the calf and hold there. Patience is a virtue. Don’t be tempted to wiggle your finger around- this can cause damage to the lining of the rectum and blood may appear in the sample as a direct result of this.
  4. With your other gloved hand, hold the open sample pot below the level of the anus, to catch the liquid faeces as it passes. Careful- it can be explosive!
  5. Once the sample has been collected, secure the lid tightly and place in a zip lock bag. This will make you popular with your vet.
  6. Either drop off the samples to your vet clinic or store in the fridge for no more than 24 hours.
  7. Care should be taken when handling faecal samples as some of the calf-scour pathogens are zoonotic, meaning they can cause disease in humans.

What happens next?

Samples can be tested in-clinic or sent away to an external laboratory.

The in-clinic tests can provide a good indication of which pathogens are involved but their major limitation is that they do not test for Salmonella.

These tests will help determine viral scour pathogens, E.coli and cryptosporidia and can be done immediately upon collection of the samples.

However, if there is an outbreak of calf scours involving the sudden death of multiple calves, it is wise to get the samples submitted to an external laboratory, as Salmonella may be suspected.

The turn-around time is slower with external laboratory analysis but all the pathogens are tested for, including different Salmonella species.

Various vaccines exist to aid in the prevention of Salmonella and an accurate diagnosis is important for future stock. External laboratories will also test the bacterial pathogens for resistance to different antibiotics.

Regardless of the diagnostic tests used, it is important to record disease events such numbers of sick  and dead calves so that your veterinarian can obtain an accurate history during a disease outbreak.  

Dr Gemma Chuck is a veterinary advisor at Apiam Animal Health.

More like this

Mobile calf shed inspired by chooks

"I looked at my neighbour's farm and thought, I can do that," said Rohan Bingley.

'That' was replicating the caravans used to house chooks on the neighbouring free range egg farm. Mr Bingley was looking for a solution to raise his dairy calves.

Moving from Bega to Gippsland to pursue dream

A fierce desire to grow their equity, and the unpredictability of the Bega seasons, has seen Tom and Gemma Otton take up a share farming role with Peter and Jeanette Clark at Kongwak.

Are your milking practices "normal"?

Recent milking time visits to a number of different dairy sheds have reminded me that “normal” means different things to different people.

More from this category

Flighty cows produce  less milk

Flighty cows are likely to respond to stress, e.g. change of environment, by producing less milk. This and other intriguing points have been noted during a study of dairy cow temperament at AgResearch.

Double reward for reducing mastitis

INNOVATIONS WHICH led to a 41% mastitis reduction in their herd have earned Tasmanian dairy farmers Phil and Lis Beattie a national award and an international trip.

Cheaper than a lame cow


COWSLIPS ARE lifesavers for many cows. Without them many more cows would go to the works. This assumes the slips are put on correctly; I see many instances where they weren’t.

Hygiene underpins calf rearing program

After moving home to the family farm, following time spent living and working in the Caribbean, Annabel Mangal began rearing and selling calves to local hobby farmers in the Adelaide Hills.

Think nutrition now for better production

Farmers should be thinking now about dairy nutrition to set their herds up for better milk production and fertility during the next lactation, says InCalf’s Dr Barry Zimmermann.


Dehorning is a routine animal husbandry practice carried out to lessen the risk of injury to stock, people and other animals during handling and transport of stock.

IN MY role as President of the Australian Cattle Veterinarians, I hear about issues that are concerning cattle vets from all over Australia.

SINCE SOUTHERN Riverina dairy farmers Rob and Gai Singleton moved to the area in 1994 they have developed a strong appreciation for the value of cow comfort in their dairying operation.

Leave a comment

Make sure you enter the (*) required information where indicated.\nBasic HTML code is allowed.

» Get social

When butter and chocolate collide

TWO New Zealand companies Lewis Road Creamery and Whittakers have teamed up to deliver what must be every dairy lover’s dream: chocolate butter.

» E-Newsletter

Subscribe to our mailing list

* indicates required