RIVM: Pathogens on dairy farms shows importance of milk pasteurisation

By Joseph James Whitworth contact

- Last updated on GMT

STEC and Campylobacter were frequently found at the goat and sheep dairy farms examined in 2016. Picture: iStock
STEC and Campylobacter were frequently found at the goat and sheep dairy farms examined in 2016. Picture: iStock

Related tags: Netherlands, Raw milk, Pasteurization, Stec, Campylobacter, Milk, Pathogen

A Dutch report has emphasised the importance of consuming milk pasteurised after an analysis of pathogens on goat and sheep dairy farms.

The Dutch National Institute for Public Health and the Environment (RIVM) and the Netherlands Food and Consumer Product Safety Authority (NVWA) investigated whether dairy goats and sheep carry pathogens that cause disease in humans (zoonoses).

Results show that pasteurisation of milk and hygiene after visiting a goat or sheep dairy farm is important to prevent disease.

Transmission via direct contact with animals or via the environment is also possible.

The agencies annually investigate how often pathogens occur in different types of farms with previous work covering pigs and laying hens.

STEC and Campylobacter frequently detected

Shiga toxin producing E. coli (STEC) and Campylobacter were frequently found at the 181 dairy goat farms and 24 dairy sheep farms examined in 2016​.

STEC was detected at virtually all farms investigated. Ruminants such as cattle and sheep form an important reservoir and excrete the bacterium in manure.

Campylobacter was found at 33% of the goat farms and 95.8% of sheep farms. It was recovered much less often among farmers and family members.

Campylobacter is the cause of campylobacteriosis and is the most common foodborne infection in the Netherlands.

Of 51 typed isolates, C. jejuni made up 84.3% and C. coli 15.7% for goats and for 26 typed isolates for sheep it was 65.4% C. jejuni and 34.6% C. coli.

Listeria was detected less often: at 8.8% of the goat farms and 16.7% of the sheep farms.

However, it is a relevant pathogen since unpasteurised soft cheese is the most important source of Listeria infection in humans.

Several major outbreaks of listeriosis have been reported in recent years on sheep and goat farms.

 Milk drunk raw and sent for processing

Most milk is delivered to a factory and will be processed and sold pasteurised.

However, some goat and sheep dairy farms make items themselves including raw milk products.

No raw milk was consumed on the majority of goat farms (74%). On farms where it was drunk, this was mainly by the farmer and his/her family (85%). Raw milk was also drunk by employees, local residents or visitors to the farm (15%).

No raw milk was consumed on most sheep farms (67%). On farms where it was drunk, this was mainly by the farmer and his/her family (63%). At a number of sites raw milk was drunk by employees, local residents or farm visitors (38%).

Bacteria reside in the intestines of the animals and are excreted in manure. A small amount is enough to contaminate raw milk or unpasteurised cheese.

Visitors to the farms can become infected if they come into contact with animals or their environment. They can reduce risk by washing their hands if they have contact with animals or their environment.

Salmonella was not found at dairy goat farms but was detected at 12.5% of dairy sheep farms. On most farms, only a type of Salmonella (S. diarizonae) not transmitted to humans was found.

An estimated 60,000 people per year contract a Salmonella infection of which about 1,000 are admitted to hospital.

Extended-Spectrum Beta-Lactamase (ESBL)-producing bacteria were detected at 1.7% of goat farms and 4.2% of sheep farms.

Twenty-five goat and five dairy farmers indicated there were problems with pests or vermin with hygiene measures including clothing, disinfection mats and hygiene locks.

RIKILT and NVWA lab merger

Meanwhile, RIKILT and the Laboratory for Feeding and Food safety (LabVV) of the NVWA are to merge from January 2019. The new institute will be part of Wageningen Research.

RIKILT is the EU reference laboratory (EURL) for mycotoxins and plant toxins in feed and food and for residues of growth promoter, sedatives and mycotoxins in food of animal origin.

Carola Schouten, Minister of Agriculture, Nature and Food Quality, said the merger was essential for NVWA as the size of the current lab means it has insufficient capacity to respond flexibly to incidents and crises.

Work for third parties such as NGOs or private companies will only be done in exceptional circumstances.

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