Cleaning and biosecurity in a Salmonella Dublin outbreak

Dr. Cynthia Miltenburg, Ministry of Agriculture, Food, and Rural Affairs

Dr. David Renaud, Ontario Veterinary College, University of Guelph

The introduction of Salmonella Dublin (S. Dublin) to a dairy or calf-raising facility with naïve animals can cause an explosive disease outbreak resulting in a high number of calves becoming sick. Typically calves that are ill from S. Dublin develop pneumonia that fails to respond to antibiotic treatment. Other presentations include calves that deteriorate very quickly without other signs and die, or calves that present as septic.

S. Dublin can be confirmed by submitting tissue samples for bacterial culture to a veterinary diagnostic laboratory. Once a farm has received a diagnosis of S. Dublin, it can be difficult and intimidating to bring in new calves again. Proper cleaning of the environment is critical to prevent future calves from becoming infected. One common question posed by many producers is, “which disinfectant product should I choose?” The answer to this is that there are many appropriate products that can be chosen, but it is possible to use each one incorrectly so that they are ineffective. A proper cleaning and disinfection protocol includes several steps to ensure the environment is safe for new calves.

S. Dublin is typically introduced to a farm through the purchase of infected cattle. The infected animal sheds the bacteria in manure and other bodily excretions which contaminate the environment and put other calves at risk of infection. Salmonella bacteria survive well in the environment for months or even years under the right conditions.

Before beginning disinfection, it is important to note that S. Dublin is a zoonotic agent, meaning it is possible for the bacteria to cause illness in people as well as animals. For this reason, precautions should be taken when cleaning. It is advised to wear personal protective equipment (PPE) including gloves, coveralls, and a mask. These are good practices for handling chemicals as well. As Salmonella bacteria can be aerosolized by pressure washing, a typical dust mask is not enough protection and you should contact your family doctor or local Public Health Unit for PPE recommendations if utilizing a pressure washer. Pressure washing is also a risk to infect other animals if the barn is not empty.

There are two areas to address for cleaning and disinfection: equipment used in the barn and the pen or housing itself. The first step in cleaning is the removal of all visible organic material. This includes removing manure, bedding, and feed, followed by sweeping with a dry broom. The presence of organic material, especially manure, will inactivate most disinfectants so it is critical to be thorough. Removing the material also removes much of the bacteria present so fewer need to be killed by the disinfectant.

The second step is to wash all surfaces with water and a detergent cleaner. Attention should be given to all feeding surfaces such as buckets, bottles, troughs, automatic feeders and waterers, pen dividers, walls, and floors. Corners and floor drains can be reservoirs for bacteria, so should be done last. After washing, the area should be thoroughly rinsed to remove all detergent and then allowed to fully dry. Fans and sunlight are ideal for quick drying.

Once the area has completely dried, the third step is to apply an appropriate, effective disinfectant as soon as possible after the barn is dry. Allowing the barn to dry too slowly or extending the time to the disinfection step can allow re-growth of bacteria. Appropriate choices for a disinfectant include a phenol, quaternary ammonium compound, or an oxidizing agent. When choosing a product, it is best to contact your veterinarian for advice to ensure the product has a label claim and is effective against the correct Salmonella species. Each product will have instructions for diluting the product to the appropriate concentration as well as the contact time required to kill the bacteria. For example, Virkon® requires dilution to a 2% solution and a contact time of 10 minutes to be effective. S. Dublin bacteria may not be destroyed if the product is used in any way other than indicated on the label. After the contact time has been reached, the disinfectant should be rinsed, and the area dried with fans and sunlight if possible. It is important to note that disinfectants are most effective on non-porous surfaces. Porous surfaces like wood are difficult to fully disinfect and may need to be removed.

Don’t forget about tools such as scrapers, brooms, and shovels which can spread manure and disease between groups; these tools will also need to be cleaned and disinfected. It is best to assign tools for each age group that are not shared.

After cleaning, biosecurity measures should be taken to prevent introduction of disease to new, naïve calves. Sourcing calves from known farms and making sure to quarantine newly arrived animals from others on the premises is an important biosecurity measure. One major consideration to protect new calves is to avoid transferring manure from older animals to younger animal pens. This should include changing or washing boots as well as hands before and after attending to young calves to protect calf health as well as human health. A physical barrier like a bench or signs can help remind all those on the farm to adhere to this practice.

Salmonella Dublin is a disease agent with real human and animal health concerns. The best plan is to work with your veterinarian to develop the biosecurity and disinfection protocols that will work best on your farm.

We thank Sam Leadley, Attica Veterinary Associates P.C., for his discussion and contributions to this article.

References:

Multi-drug Resistant Salmonella Dublin in Cattle. (2018, October 15). Retrieved from https://www.vet.cornell.edu/animal-health-diagnostic-center/news/multi-drug-resistant-salmonella-dublin-cattle

Disinfecting Using Chlorine Dioxide. Attica Vet. Assoc. 2019 http://atticacows.com/library/newsletters/DisinfectingusingChlorineDioxideR1960.pdf

Disinfection 101. Center for Food and Public Health. (2008 May). http://www.cfsph.iastate.edu/Disinfection/Assets/Disinfection101.pdf