Every year I treat many calves for neonatal diarrhoea, and one causative agent that I have seen become more and more prevalent over the last 15 years is cryptosporidium.
It is a tough bug to get under control, and while it will cause very serious disease on its own, it will happily team up with rotavirus or coronavirus to cause devastating diarrhoea.
Cryptosporidium parvum is a protozoan parasite that causes diarrhoea in young calves generally between one and three week.
C. parvum can also cause diarrhoea in people.
What makes it so difficult to eliminate is its ability to create microscopic oocysts, which are the thick-walled infective stage, making it highly resistant in the environment, and to many disinfectants.
The next trick it has is its infective nature.
Studies have shown that just 10 oocysts can cause severe diarrhoea, resulting in potentially billions of oocysts being shed into the environment.
The source of infection for young calves is important to determine, in order to break the transmission cycle.
Considering adults do shed C. parvum, transmission could occur directly via dams around calving or suckling, or indirectly via a contaminated calving area.
There is evidence of calves beginning to shed oocysts at only a few days of age, which suggests they were infected around the time of birth, given that the pre-patent period is around three days.
Calf-to-calf transmission, either directly or via contaminated calf accommodation, is likely to be an extremely important transmission route, given the high levels of oocysts shed by acutely infected calves, and also considering the low infectious dose needed, and the resistant nature of the oocyst in the environment.
Controlling this disease takes a multi-faceted approach.
Despite cryptosporidium being a considerable cause of diarrhea in young calves, there is only one compound licensed for its treatment.
Halofuginone lactate is licensed to be used in the first seven days of life to reduce oocyst shedding, but is less effective if administered more than 24 hours after diarrhoea begins.
There are many products that are claimed to be effective in treating cryptosporidium; however, these are anecdotal claims.
There have been studies to show that nutraceuticals are effective in controlling oocyst shedding in the laboratories, they are most effective in mild infections, and certainly have a role to play.
Colostrum management is of course the corner stone of any calf disease control, and it has been discussed at length in many articles.
Suffice to say: three litres of good quality colostrum in the first two hours of life.
The most important aspect of cryptosporidium control is farm management.
All management changes must aim to reduce oocyst build-up.
A common trend on farms is to see an increase in diarrhoea as the calving season progresses.
Changes that are undertaken on farm are many and varied, such as taking calves from dams as soon as they calve, cleaning teats before taking colostrum, moving calf pens periodically (if possible), separating older calves from younger calves, and not mixing groups.
Disinfection of calf pens effectively is paramount during the calving season, but particularly during the summer, before the autumn or spring calving season begins.
There is only a handful of disinfectants that are effective against cryptosporidium, but it is equally important to prepare the surface to be disinfected.
These disinfectants must be used at the correct concentration and correct contact time.
Steam cleaning can also be very effective, if used correctly.
With emerging diseases and challenges in the dairy sector, we need to evaluate how we approach new problems as well as old ones, and manage them effectively.
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