Campylobacter And Raw Milk: Risk And Safety Considerations

The recent fad of raw milk, encouraging natural, unprocessed food items to go to market, has been of growing concern for microbiologists. Despite its growing population for its perceived health benefits, untreated milk, which has not undergone pasteurisation, is at high risk for multiple pathogens linked to food poisoning. Campylobacter is one of the most common bacterial contaminants in foods, causing campylobacteriosis,s resulting in bouts of sickness and diarrhoea. Without proper safety procedures, raw milk poses a significant risk of contamination, leading to sickness and outbreaks.

What is raw milk?

Raw milk describes the natural, untouched state of milk, otherwise described as non-pasteurised. Pasteurisation is the process of heating milk products to kill dangerous bacteria that may be present in the liquid, allowing safe consumption for the public.

Reasons for consumption

There are several claimed benefits of drinking raw milk, but most theories have not been thoroughly researched to make these claims viable. Some of these include

1. Raw milk lowers the risk of allergens 

A common study used to back up this claim is the PASTURE study cohort, highlighting a potential link between unpasteurised milk and lack of allergy development in early years.¹ 

However, this process is likely to be multifactorial, meaning there are too many variables to conclude that raw milk is the reason for this. It is likely that many of those who drink raw milk are associated with farmlands, increasing their interaction with other microbes and pathogens, which may explain allergic resistance. Ultimately, there is not enough evidence to back up this claim. 

2. Raw milk helps build lactose tolerance 

A study into Lactobacillus Acidophilus, a probiotic or “good bacteria” which is present in raw milk, has been shown to ease lactose indigestion in humans. However, the levels of this bacteria within pasteurised vs unpasteurised is unknown, and therefore, the benefit is difficult to quantify.²  

Another study that aimed to measure the differences in symptoms of lactose intolerance in raw compared to processed milk found no connection between raw milk and reduced symptoms.³

3. Pasteurisation reduces vitamins in milk

Some pro-raw milk groups claim reduction of Vitamin A, B12 and E during pasteurisation. A meta-analysis review of over 40 studies concluded that Vitamin B12 and E can be moderately reduced after pasteurisation. However, in most European diets, vitamin B12 is mainly absorbed from other sources such as meat and fish, and vitamin E from nuts and seeds. Therefore, reducing these vitamins in dairy does not significantly impact daily human nutrition.⁴ 

Many of these studies only paint part of the picture, with evidence suggesting consumption may be a good thing. However, current confirmed research highlights how the risks far outweigh the benefits in the case of raw milk.

Risks associated with raw milk

Although farmers and traders are held to high standards through the Food Standards Agency within the UK, there are always possibilities for contamination across different aspects of dairy farming.

Farm environment

•  Exposure to faecal  matter, contaminated water and feed
• Poor sanitation and hygiene
• Inadequate handling/storage and transportation
• Unsterile equipment

Animal health

• Bovine mastitis – inflammation in the udders from physical stress or infection – pathogens can be passed from the udders to the milk⁵
• Bovine tuberculosis – a bacterial disease caused by the Mycobacterium tuberculosis complex transmitted through milk from infected cattle. Can cause respiratory disease in  humans, which can be fatal⁶

From this contamination, other dangerous pathogens such as E.Coli, Salmonella and Campylobacter can cultivate and infect other hosts.

Campylobacter

Description

Campylobacter describes a group of related species of bacteria, otherwise called a genus. The genus Campylobacter has 14 species within the diverse group, many of which responsible for gastroenteritis in humans.⁷

Campylobacteriosis was the most commonly reported animal-transmitted disease in the EU in 2017.⁸

Transmission

Campylobacteriosis is described as a zoonotic disease, meaning it can be transmitted from infected animals or products from infected animals to humans. Most commonly, this is transferred from raw or undercooked poultry, raw milk and sometimes from physical contact with animals carrying the bacteria.⁹ 

Once within the gut, using its spiral shape like a corkscrew, it can penetrate the mucosal layer of the intestine.¹⁰

Many species of campylobacter release toxins to initiate immune responses. The irritation to the gut and the need to expel the bacteria from the body triggers diarrhoea.

Symptoms

Generally, this stomach bug will start to present itself 2-5 days after ingestion or contact with contaminants.

Symptoms include

• Nausea
• Vomiting
• Stomach Cramping
• Diarrhoea  – which may contain blood
• Fever

The recommended treatment is to rest at home until the infection clears and to drink plenty of fluids to avoid dehydration.¹¹

Complications

Incidence of campylobacteriosis is relatively high, with 44.5 cases per 100,000 reported by the ECDC, with many more going unreported. However, the risk of complications is lower, with hospitalisations occurring in approximately 24% of cases.¹²

Guillain-barre syndrome

A 2010 review study highlighted the incidence of Guillain-Barre Syndrome (GBS) of 30.4 cases per 100,000 cases of campylobacteriosis.¹³

This rare condition occurs when the body’s immune system starts attacking itself and the nerves of the peripheral system.¹⁴

This condition can present symptoms of paralysis within the arms, legs, and face, as well as muscle weakness and movement difficulties.

Campylobacter causes this condition through a bimolecular mechanism called molecular mimicry. This occurs from molecules on the bacterial surface being mistaken for the body's own nerve cells, launching an autoimmune response targeting not just campylobacter bacteria but the body's cells as well.¹⁵ The exact triggering and the predisposition to obtaining GBS are not fully understood.

Treatment for this condition often involves Immunotherapy to ease symptoms and quicken recovery. The most common is intravenous immunoglobulin (IVIG), where donated blood containing a mixture of useful antibodies is inserted directly into the body to combat the harmful autoantibodies causing infection. More information on treatments can be found here.

Safety considerations

Although all the risks of contamination are rigorously considered by local and international agencies, extra steps can be taken to ensure maximum quality and safe products reach us and our stores.

Pasteurisation

The practice of pasteurisation has been legally required in Scotland since 1983, although many vendors made this the norm as early as the 1910s, initially used to prolong shelf-life. The evidence of pasteurisation reducing infection is apparent, with a significant reduction in milk-borne infection and outbreak control. From the introduction of the law in Scotland, a 95% decrease in milk-borne pathogenic diseases was reported.¹⁶ 

Pasteurisation heats liquid products for a short period of time to remove harmful bacteria then rapidly cools to prevent further bacterial colonisation. There are 2 main types of pasteurisation used today – High-Temperature Short Time (HTST) and Ultra-High Temperature (UHT).

Comparison of HTST and UHT

Pasteurisation is essential for milk for 3 main reasons

• Kill dangerous pathogenic contaminants
• Prolong shelf-life by removing spoiling bacteria
• Safe consumption without compromising any nutritional value

Education and public awareness

It is crucial that there is awareness about the dangers of raw milk and the pathogens that can lie within it. Although procedures are in place to avoid contamination as much as possible, the extra step of pasteurisation helps ensure that there are minimal bacteria present. Although not every person who consumes raw milk will get sick, the consequences are too great to risk, especially as the potential of an outbreak is apparent. Additionally, it is the young, the elderly and the immunocompromised who will suffer the most, and therefore, we all share a public responsibility to ensure widespread safety.

Summary

The perceived benefits of drinking raw milk are not without their consequences and risks. Some studies give preliminary information that raw milk has its benefits; however, these are early studies which can be misleading or omit important information and, therefore should be treated with caution. Unlike these apparent benefits, complications and illnesses caused by contamination are established. Contaminated milk can contain nasty bacteria such as Campylobacter or E.Coli which can make you very sick, and pasteurisation is the best method to reduce the chances of infection.