Disinfection of calf sheds affected by cryptosporidiosis: A Review
For a Formal Review on Cryptosporidium Disinfection: Refer to Casemore & Watkins (1998).
For a comprehensive review of the extensive research, methodologies and limitations of studies the most useful work has been completed by Casemore & Watkins (1998). This fails to find a practical method for use under field conditions. It does however identify many disinfectants such as Virkon that have failed to provide useful activity even after repetitive trials under different conditions of concentration and time.
Recommendations for on-farm Management:
Two reviews have been included with some additional footnotes (in italics); one from Scotland; Innes & Wright (2008) and the other from Wisconsin by Sockett (2012). Each review has different emphasis and each highlights that disinfection is part of an overall strategy.
Reduction of Oocyst Contamination:
Please remember that the goal is to achieve a dramatic reduction in infective dose. This will reduce the severity of the infection and is reflected in a slower start to scouring which will appear also to be more mild. The same benefits are also observable with some some sub-genotypes of Cryptosporidium as reported by Thomson (2012). If all else fails in protecting the healthy status of a calf, the back-up plan is to use EXAGEN on all calves from soon after birth. EXAGEN reduces the internal challenge once oocysts have been ingested and enables normal feeding to continue even if some calves show scours.
Use of Chemical Disinfectants
Caution: Any product which claims to have activity against cryptosporidial oocysts should be carefully checked for actual field test results. Even extensive laboratory testing may not have significant impacts on the risk of infection in the field. With combination strategies some risk may be reduced but research results have sometimes been disappointing when faced with field challenges (Keidel & Daugischies, 2008).
Moredun Research Institute in Scotland has emphasised that disinfection options are very limited. In their opinion ammonia based disinfectants or steam cleaning are the most effective methods of cleaning contaminated pens or utensils.
They also recommend that cattle slurries and manure are well fermented or composted prior to application on to pasture with correct disposal of animal wastes will reduce environmental contamination with viable oocysts.
(this may be of importance for waste management of shed effluent in New Zealand, especially that from calf sheds).
The basis of this recommendation is that cryptosporidial oocysts are killed by heat above 55- 60 °C and increasing ammonia concentration.
Oocysts are also killed by drying out (Innes & Wright, 2008).
Prior to the calving season check the actions. These are broken into segments of farming practice that may aid the usefulness of the information
Purchasing in stock:
Where young replacement stock are purchased (preferably from reliable, disease free sources. Even farms used in the past can change their personnel and farm practices) they should be placed in quarantine, well away from other stock, for at least 7 days to see if scouring occurs.
Any animals which scour should be kept indoors in isolation, which should continue for at least 1 week after the diarrhoea has ceased to ensure oocyst shedding has stopped.
Market purchased animals are often a prime importer of infections, including Cryptosporidium. Either infected prior to going to market or infections picked up during transit. Bought in calves should have their own feeding bucket which is regularly disinfected.
Animals (cows) about to give birth should be cleaned of faecal contamination before their offspring are born (McGuirk 2004 for a disinfection Programme). There are numerous references which refer to this risk to manage.
(Northern hemisphere) Adequate fresh bedding should be provided in the delivery area. Clean the bedding between cows.
Move calves and mothers as soon as practicably possible after each birth.
All new born livestock should received colostrum, as weaker animals are generally more susceptible to infections. But this applies to the secondary bacterial infections rather than to the primary infectious agents of the cryptosporidial infections. Colostrum management also requires active participation in the other practices around the period of a cow delivering a calf e.g. Clean utensils.
Any movement of calves in carry trays behind tractors should be in clean carry pens which have had the highest hygiene standards between calves being moved. Every cow should be suspect of being a carrier with an infected calf incubating Cryptosporidium beside it.
The risk of infecting the newly born calves should be minimised by ensuring teats are clean, and calves should be allocated disinfected individual feeding utensils (see Rockett below for specifics).
This is one factor that management has some control over. This is a routine which has been shown to have an impact on transference risk. So daily checking to see it is implemented can be important.
Scouring or quarantined animals should be handled after the healthy stock to prevent transmission of oocysts on soiled clothing or equipment.
Where possible, an ‘all in all out’ policy should be employed, whereby pens and feeding troughs are either steam cleaned or treated with an appropriate disinfectant.
If this is not possible, placing newly born animals in clean disinfected pens may help reduce the risk of transmitting infection.
Individual penning of calves, avoiding animal to animal contact, can be helpful. This may not be practical in New Zealand, but is recommended as important in many farming areas..
Calf pens should be liberally bedded with straw to minimize seepage of wastes. Keep fresh bedding in the pens. Beware of pens where there are multiple mixed calves potentially cross-contaminating water supplies with calf faeces.
Other animal species may be risk factors for spread e.g. rats/mice/birds; attracted by the availability of food.
Good hygiene and disinfection remain the most effective strategy to reduce contamination.
Disinfection of contaminated premises, pens and feeding utensils can be problematic since Cryptosporidium oocysts are resistant to commercial agricultural disinfectants, such as ionophores and even formalin.
Ammonia based products, such as ‘Oocide’, originally developed to kill coccidia in poultry houses, are extremely effective, but cannot be used where livestock are still present because of the caustic ammonia fumes generated.
Beware though that residual organic matter can inactivate some chemicals (hydrogen peroxide).
And many chemicals have significant health and safety issues so instructions must be followed carefully.
Gross decontamination is the first stage followed by superficial disinfection. Steam cleaning can be an effective way of “sterilizing” buildings, pens and feeding troughs. (Sterilization is a goal – not achievable in animal sheds).
Oocysts can survive for many months under favourable conditions – they prefer a cool, moist environment, and do not survive drying out.
Disinfection of Cleaning Utensils:
Follow these steps to ensure calf feeding equipment is properly sanitized:
|1||Rinse||First, using warm water, about 90-100 degrees F, rinse dirt and milk residues off both the inside and outside of feeding equipment. Do not sure hot water to rinse.|
|2||Soak||Next, soak the calf feeding equipment for 20-30 mins in a mixture of hot water greater than 130-135 degrees F and 1 percent (pH 11-12) chlorinated alkaline clean in place (CIP) detergent.|
|3||Wash||Then, thoroughly wash inside and outside of the feeding equipment with a brush. You can also wash bottles and buckets in an industrial dishwasher. Fats melt at temperatures greater than 110 degrees F, so keep the water temperature above 145 degrees F during washing.
Manually wash bottle nipples with a brush. Do not wash nipples in a dishwasher, as they fail to properly clean nipples and this can lead to high bacteria counts in the milk. While manually washing nipples, check for any visible cracks and signs of wear and tear. Replace those that are worn. Cracked nipples can harbor bacteria.
|4||Rinse Again||Rinse for about 5 minutes using warm water (about 100 degrees F) that contains 50 ppm of chlorine dioxide, thoroughly rinsing inside and outside of the calf feeding equipment. Then rinse the equipment with acid (pH 3-4) to control milk stone once or twice a week. After rinsing the nipples, keep them in a covered container filled with a 50 ppm sanitizing solution of chlorine dioxide solution until they are used.|
|5||Dry||Then, allow the equipment to drain and dry before using again. Avoid stacking upside down on a concrete floor or on boards, as this can inhibit proper drying and drainage.|
|6||Final preparation||Lastly, spray the inside and outside of equipment with a 50 ppm solution of chlorine dioxide two or less hours before use. Allow a minimum of 60 seconds of contact with equipment.|
After all six cleaning steps have been completed and the equipment is dry it should be ready to use again. The above steps refer directly to calf milk feeding equipment, but the same considerations for cleaning and sanitization should be given to the water and starter buckets. At a minimum calf water buckets and starter buckets should be cleaned and sanitized between groups of calves.
|Figure 1: The pH of household bleach (sodium hypochlorite) is 13-14. When bleach is added to water it forms both hypochlorus acid and the hypochlorite ion. The relative amounts of each are affected by the pH of the solution; a problem with using bleach as a disinfectant.|
For example, at a pH of 8.5 roughly 10% of the bleach exists as hypochlorous acid and at a pH of 6.5 roughly 90% of the bleach exists as hypochlorous acid. Hypochlorous acid is a very good disinfectant (biocide) having approximately 80 times more killing power than the hypochlorite ion. A ten percent household bleach solution has a pH of 10-11 depending on the acidity of the water. When the pH is greater or equal to 10 there is virtually no hypochlorous acid present in the solution.
A note of caution, the pH of the solution should never be less than 5.5. When the pH of the solution drops below 5, large amounts of chlorine gas are created.
Producers must get in the habit of using commercially available test strips to verify their concentrations of chlorine dioxide are right prior to use.
|Figure 2: The table shows the concentration and contact time needed for different types or classes of disinfectants to kill >99% of Cryptosporidium parvum oocysts at room temperature. We want to ensure the solution is strong enough to kill Cryptosporidium parvum oocysts since they have a very high resistance to chemical germicides; higher than microorganisms such as M.tuberculosis and Staphylococcus.|
Innes E, S Wright (2008). Cryptosporidium and Cryptosporidiosis.The Moredun Foundation New Sheet Vol 4, No. 18
Crockett DC (2012). Dairy Basics altagenetics.com/iraq/DairyBasics
Casemore DP, J Watkins(1998). Review of Disinfection and Associated Studies on Cryptosporidium. Report commissioned by the Department of the Environment, Transport and the Regions (DETR), managed by the Drinking water Inspectorate (DWI), from Yorkshire Environmental Alcontrol, UK p56
Keidel J, A Daugschies (2013) Integration of halofuginone lactate treatment and disinfection with p-chloro-m-cresol to control natural crytosporidiosis in calves. Veterinary Parasitology 196, 321-32
McGuirk SM, (2004). Trouble Shooting Calf Health Concerns. Proceedings of the WBC Quebec, Canada. Published www.ivis.org