Test for subclinical coccidiosis and take steps to prevent its spread and impact on calf health and performance. Don’t wait for clinical cases to take hold – be proactive.
TEXT HANNAH WILSON
Coccidiosis is a common cause of scour in calves on UK units, but can easily go undetected. And it can lead to significant production losses, according to Westpoint Farm Vets’ Tim Potter.
“Coccidiosis could be found on most units if producers regularly tested for it,” he says. “But because not all producers are aware of the negative impact it can have on calf health and performance, it often goes undetected or undiagnosed.”
Coccidiosis in calves is caused by three Eimeria parasites. These shed disease-causing oocysts that multiply rapidly in the gut. They are spread via environmental faecal contamination and can be picked up orally.
“The first signs of coccidiosis are often extremely subtle, with calves appearing outwardly healthy at first. But performance then begins to dip. This is known as subclinical coccidiosis,” says Dr Potter.
Sub-clinically infected calves still excrete oocysts, meaning the disease can spread to other calves. Infected calves generally do not gain weight as normal and their coats may have a dull appearance. Up to 64% of economic losses occur at this sub-clinical stage. Dr Potter explains that in more severe clinical cases, scouring will be seen and become progressively worse, often containing blood, and calves will be seen straining to pass faeces. Symptoms also include weight loss, lack of appetite and apathy.
Diagnostic test
To confirm a suspected case, a diagnostic test is required. “But there’s no on-farm test for coccidiosis, so your vet will need to take faecal samples and look for disease oocysts under a microscope. Results should be back in less than 48 hours,” he says.
The best course of coccidiosis treatment will vary from farm to farm, so producers should work with their vet to develop suitable treatment protocols to suit the needs of their herd and unit.
“If producers suspect coccidiosis then it’s likely that other calves in the group are also infected, as it spreads rapidly through faecal contamination. So the whole group of calves should be treated with a toltrazuril-based, or similar, drench to kill the parasite in the gut,” explains Dr Potter.
Subtle signs: calves with subclinical coccidiosis often appear outwardly healthy
Treatment should be swift, to minimise the disease’s impact on calf health and growth rates, and to prevent symptoms from becoming more severe.
“Coccidiosis often occurs during times of stress. This often leads to the assumption that slow growth rates are a result of the stress caused by changes to management, whereas there’s a substantial risk that it’s actually subclinical coccidiosis beginning to show.
Monitor growth
“So I’d recommend regularly monitoring growth rates throughout the calf-rearing process, and testing for coccidiosis if animals aren’t hitting target growth rates,” says Dr Potter.
Dehydration can be a significant problem in calves suffering from clinical cases of coccidiosis, so producers must assess their hydration status. Symptoms of dehydration can include reluctance to stand, sunken eyes.
Producers can quickly evaluate hydration status by ‘skin tenting’ – pinching a fold of skin on the calf’s neck and counting how long it takes to return to normal. If the calf is hydrated the skin should ‘flatten’ in less than two seconds.
“Electrolyte therapy is important to help rehydrate calves – never underestimate how much fluid has been lost. Not only will calves be losing fluid through scouring, but also through reduced appetite, so losses are likely to be greater than expected,” adds Dr Potter. Cases of severe dehydration can be difficult for calves to recover from. But, he adds, if administered properly, prompt rehydration is an effective way to bolster a scouring calf.
“The sooner electrolytes are administered, the better chance the calf will have of surviving. Performance losses can be minimised.”
Prevention measures
Ultimately, coccidiosis is present on most units, but the worst cases of disease are seen in calves with poor immunity. So Dr Potter says it’s vital to ensure newborn calves receive enough quality colostrum, as quickly as possible, and certainly during the first six hours of life. While keeping stress to a minimum cannot prevent the spread of disease, it can help reduce the risk of a subclinical case becoming clinical. Stress can be caused by, among other things, high stocking density, disbudding, extreme weather, and re-housing or grouping. “I’d also encourage producers to develop strict and thorough calf-house cleaning protocols. Producers must set aside time for cleaning and disinfecting housing between groups of calves. Anything that comes into contact with the calf poses a contamination risk, so it’s worth running through protocols with your vet to ensure all bases are covered,” adds Dr Potter.
Where possible, he also urges producers to design calving pens so they’re easy to clean, with stock board or dairy paint. And set them up so staff can ‘flow’ easily through the calf house, minimising the risk of cross contamination between clean and dirty areas.
“Choose an appropriate disinfectant – one that will kill the coccidiosis parasite’s oocysts in the environment, as not all products do this. So be sure to use a disinfectant labelled as ‘oocidal’.”