Keeping one step ahead of Salmonella this Autumn...

Around the Autumn Equinox we often see an increase in Salmonella cases with greater inclement weather and closer cow contact. Vicky goes through why and how best to keep on top of it in the coming weeks.

The main cost of Salmonella infection comes from decreased milk yield in subclinically affected cows who typically give 316kg less in a 305 day lactation.

Salmonella is acquired though ingesting faeces containing the bacteria. The severity of clinical signs depends on the amount eaten. Some exposed cows will become chronically infected, intermittently displaying clinical signs and shedding the bacteria in their faeces, particularly at stressful times like early lactation.

Salmonella warning signs

Clinical disease is most commonly seen in calves between two weeks and three months old and concurrent disease makes calves more susceptible to salmonella. Clinical signs that may indicate the presence of Salmonella:

Increase in sick calves-diarrhoea, pneumonia, joint infections and damage to extremities (loss of eartips, tails or toes)
Sudden deaths
Abortions
Diarrhoea in adults
Poor reproduction

Diagnostic tools for Salmonella

There are several tests available to identify the current or historic presence of Salmonella including milk and blood antibody tests, bacterial culture of faeces, abortion tissues and calf post mortem tests.

Treatment

Treatments are available for sick animals however a full return to perfect health is difficult to achieve and we must remember that this does not prevent shedding of Salmonella to others, so control is still important. Your farm vet can advise you on the best treatment for individual sick animals tailored to your farm.

Salmonella control & prevention

Hygiene and cow management are the most import factors for limiting the cost of disease and many parallels can be drawn to Johnes disease control measures.

1. Cow Management

Identify and cull individually affected cows, though chronic intermittent shedders may not be easy to identify. It may not be economically viable when prevalence is high, in which case these cows should be managed to avoid bacterial spread.
Managing chronically infected cows includes snatch calving, cleaning calving areas between cows, reducing stocking densities and not putting sick cows in group calving pens.
Feed good quality clean unpooled colostrum to calves and avoid feeding waste milk. Use separate clean utensils for feeding calves.
Keep group sizes small and stable, avoid mixing in sickly calves. This can be a challenge when using automatic calf feeders.
Minimising stress, providing clean individual young calf pens and a suitable diet to maximise the calves’ immunity.

2. Vaccination

(must be used alongside a robust management plan!)

Vaccination can reduce the intensity and duration of clinical signs. It can also reduce the shedding from chronic carrier cows so less bacteria are available to infect others.

3. Hygiene and biosecurity

Hygiene at calving-put calving cows in separate pens. Wear ‘calf only’ clothes and wellies, or clean and disinfect on entry and exit to the calf shed.
Avoid introducing infected animals into the herd: Buy from Salmonella free herds, implement a strict protocol of testing and isolation for new purchases.
Restrict livestock access to external sources of infection e.g. double fence perimeters, no co grazing with neighbouring cattle.
Restrict visitor access and provide a cleaning & disinfection point.
Have a vermin and parasite control plan to limit other animals spreading the disease.

4. Salmonella is a zoonotic disease so can be passed onto humans!

In order to help minimise the risk to family workersvisitors, appropriate PPE (gloves, wellies, outer clothing) and cleaning facilities should be available. Unpasteurised milk should not be drunk and people with compromised immune systems (very young, old, infirm) should avoid animal areas on the farm.