Veterinary: Zoonosis can bring serious disease inside the farmhouse door

When I was a student at the Vet College in Dublin, many years ago, a fellow student ended up in St Vincent’s Hospital.

Nothing new for a student to end up in hospital, you might say.

However, this student spent three weeks in hospital, and things were touch and go for a while.

He was on the drip for two of those weeks, before finally recovering.

He had picked up Salmonella from an animal he had come into contact with.

We hear of Salmonella being a zoonotic disease, and possibly don’t understand what this means.

What the word zoonosis means is “a disease that can be transmitted to humans from animals”.

This friend of mine came into contact with an animal that had Salmonella, and he succumbed to the disease, with very serious consequences.

On our farms today, as vets, we commonly come across outbreaks of Salmonellosis whether it is an abortion storm, calf diarrhoea, pneumonia, arthritis or joint ill.

Once recovery takes place, a lot of these animals will shed the Salmonella bacteria in vast numbers, if they are stressed.

Some of these animals remain carriers for life, and will continue to shed the Salmonella intermittently for the rest of their lives.

This presents a very serious problem for the farmer and his immediate family, one which may not seem obvious at the time.

The farmer is handling his cows twice a day for most of the year.

This is serious contact time, if even one of these cows is a carrier.

The most common way of disease spread is from contaminated faeces, and something as simple as a splash into the eye can lead to infection entering the body.

You can never be too careful.

Young children, older adults, and people with a poor immune system are the ones most likely to have a severe infection. Drinking raw milk is a no-no.

There are two common subtypes of Salmonella found in cattle, Salmonella Dublin and Salmonella Typhimurium.

Salmonella Dublin is the more common one (85%), and when it causes disease in humans, it is often invasive and can be life-threatening.

Salmonellosis is usually characterized by acute onset of fever, abdominal pain, diarrhoea, nausea and sometimes vomiting.

A small number of people with Salmonella develop pain in their joints that can last for months or years, and can lead to chronic arthritis, which can be difficult to treat.

Riona Sayers at Moorepark has been doing a lot of work on Salmonella over the last few years, including cost-benefit analysis of vaccinating the milking herd.

Apart from proving an increase in milk production worth in the order of €112 per cow per year, just by vaccinating as against not vaccinating, she always stresses the importance, from a zoonotic point of view, of vaccinating against this disease, and keeping the threat of the farmer and his family becoming sick as low as possible.

We talk nowadays of biosecurity. This can be broken into two components, biocontainment and bio-exclusion.

Bio-containment is where we already have the disease on the farm, and we are trying to contain it, and restrict the damage it will do as low as possible.

Bio-exclusion is where we don’t have it on the farm and we want to keep it out.

There are various things we try to do to either contain or exclude the disease, and these form part of a herd health plan.

With Salmonella, in both scenarios, we must think of the humans as being part of the farm, and part of the biosecurity process.

Vaccination of the whole herd plays a vital part in keeping the humans on the farm safe from the perils of Salmonella.

If you have any issues or questions regarding Salmonella on your farm, just ask your veterinary surgeon, who will be only too willing to help.


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