Addressing the risk factors for next year.
Buying in Calves
The key feature to manage scours in calves associated with cryptosporidiosis is to reduce the severity and intensity of infection i.e. primarily to reduce the availability of cryptosporidial oocysts at two levels
- Reduce the Intake – any environmental contamination before oocysts become established. Hygiene practices require to be reviewed and changes made.
- Prevent the natural recycling of the oocysts in the intestinal lining by knocking these out before the re-cycling occurs (beta-cyclodextrin activity of KRYPTADE and EXAGEN).
The key features which make environmental control difficult:
- Calves can be infected at birth from the cow’s natural excretion.
- Calves are ‘dropped’ into contaminated areas.
- Calves can excrete extremely high numbers of oocysts into the environment before showing any signs of scours.
- Only low numbers of oocysts are required for an infection to be set off.
- Once scouring, calves excrete massive numbers of oocysts.
- Scours may start 2 -3 days after the infection occurs. With lower oocyst intakes this may be 4 – 6 days. With mixed infections there is also a delay in signs of 4 – 6 days.
- Calves will excrete crypto oocysts before scouring starts, and commonly all calves will excrete some oocysts in the first 4-6 weeks even without signs. This the sub-clinically infected group. It emphasises the importance it is to prevent cross infection. Anything that is done to reduce this is important. Even high pressure hosing creates vapour droplets aiding oocyst spread, but is better than leaving dung to infect new calves.
- While cleaning is desirable (to reduce availability of oocysts) total removal of all the oocysts is not achievable. Lowering the number of oocysts infecting a calf will reduce the probability of signs of scours.
- Many calf systems do not feature concrete pens that can be decontaminated with water.
- There are no recognised disinfectants in New Zealand that will quickly and easily decontaminate an infected environment. Hydrogen peroxide at 6% concentration. This should be used after physical removal of contaminated faecal material. Allow for minimum of 20 minutes contact.
- Deeper layers of bedding reduce the risk of calves becoming infected. Freshen weekly.
- Beware of ‘vermin’ and contaminated water, as possible sources of infection.
Refer to Disinfection Part 1 – especially the importance of Hygiene management, and Part 2 Practical Disinfection
Cryptosporidiosis Risk Factors: A Scientific Report on Shed Transmission Studies