Hunters’ Guide to Health Risks

Hunters’ Guide to Health Risks: Understanding Brachyspira Exposure in Northern Australia 

By wildlife ecologist Joanne Heathcote 

Hunting feral vertebrate species in northern Australia can be an exhilarating adventure, offering a unique connection with nature and the thrill of the chase. However, this passion comes with certain health risks, particularly from zoonotic parasites such as the Brachyspira species. Two species of anaerobic intestinal spirochaetes, Brachyspira  (formerly Serpulina) pilosicoli and Brachyspira aalborgi, can colonise the human large intestine. Both species are associated with a condition known as intestinal spirochaetosis (IS), in which a thin carpet-like layer of spirochaetes is found attached by one cell end to the colorectal surface epithelium. 

The presence of IS has been documented microbiologically throughout Africa, Australia, India, Indonesia, and much of the Western world for decades, particularly where living standards are low. Although IS has been historically considered relatively rare, recent studies suggest that it might be more widespread than previously thought. Carriage of spirochaetes is going unrecognised in Australian laboratories, as current protocols do not specifically target their detection, and existing medical opinions remains ambivalent about their significance. 

In the veterinary world, IS has been linked to diarrhoeal illness in swine, poultry, dogs, cats, opossum, non-human primates, and guinea pigs. The disease causes significant economic losses when it affects large numbers of swine. In Australia, feral pigs are known reservoirs for Brachyspira. 

Colonisation of humans by intestinal spirochaetes is less well documented. Invasion of spirochetes beyond the colorectal surface epithelium can be associated with gastrointestinal symptoms; whereas individuals who don’t experience these symptoms may be mostly asymptomatic. Rare cases of spirochetemia and multiple organ failure have been reported in critically ill patients with IS. This is especially concerning for individuals with compromised immune systems, who may experience severe health complications from opportunistic infections like Brachyspira.  

Given the often-challenging environments and physical demands associated with hunting, individuals with compromised immune systems are particularly susceptible to health complications from opportunistic infections like IS. 

Routes of exposure 

Hunters can inadvertently expose themselves to Brachyspira through several pathways. The most common include: 

• ingestion of contaminated food or water 

• direct contact with infected animals or their faeces 

• poor hygiene practices, especially after handling game. 

The gold standard for diagnosis of human IS worldwide is confirmed through colorectal biopsies, where direct histological examination can reveal the presence of the bacteria. Detection by culture, microscopy, or polymerase chain reaction (PCR) is not difficult, and could be implemented in Australian laboratories to examine faecal specimens during investigations of individuals with chronic diarrhoea of unknown aetiology. 

Recognising symptoms 

Symptoms of Brachyspira infection have been linked to a variety of intestinal disorders and can include: 

• abdominal pain 

• chronic and intermittent watery diarrhoea 

• rectal bleeding 

• weight loss 

• malnutrition. 

These symptoms often resemble those of more common gastrointestinal illnesses, making proper diagnosis difficult if a doctor is not aware of this condition.  

Preventive measures for hunters 

For those engaged in hunting or any outdoor activities, strict hygiene practices are essential. 

Here are key strategies to minimise the risk of Brachyspira infection: 

• Hygiene first: Always practice meticulous handwashing after handling animals or their remains. 

• Cook meat thoroughly: Ensure that all game meat is cooked to an internal temperature of at least 75°C. 

• Water safety: Refrain from drinking untreated water while in the field to avoid exposure to pathogens. 

• Animal faeces awareness: Avoid contact with animal faeces, which can harbour numerous parasites and pathogens. 

You want to do everything in your power to avoid IS.  

Human intestinal spirochetosis - Case presentation 

A 46-year-old female experienced one year of the following symptoms: 

Accelerated oro-anal transit with “porridge-like diarrhoea”, intermittent supra-umbilical pain with loose mucoid bowel movements, uncontrollable weight loss, increased food intolerances, reflux esophagitis and arrhythmias. 

Physical examination was significant for audible borborygmi, with tenderness but no organ enlargement. 

The patient has a family history of irritable bowel syndrome (IBS), which she herself suffers from. She was not immunosuppressed and subsequent laboratory workup for all other infectious pathogens including HIV and inflammatory bowel disease (IBD) was negative.  

Self-prescribed medications included daily probiotics, and Gastrostop Plus when symptoms were severe. The use of Esomeprazole for reflux symptoms increased. 

February 2024 – Blood, urine and stool samples ruled out illnesses. 

March 2024 – Scope and biopsy procedure were undertaken.  

Random colonic biopsies confirmed the diagnosis of intestinal spirochetosis (IS). 

A colonoscopy revealed two small polyps. Esophagogastroduodenoscopy (EGD) revealed gastritis and a small hiatus hernia. 

No specific treatment was prescribed initially by the Centre of Digestive Diseases (CDD) due to diagnostic error; her specialist missed the diagnosis of intestinal spirochetosis (IS) in her report.  

25 April 2024 – The patient’s symptoms worsened, and she was admitted to Katoomba hospital. Because of the severity of her symptoms, she was promptly put on intravenous antibiotics. The doctor in charge discussed her case with the Head of Infectious Diseases at Nepean hospital. He advised that IS can be treated with antibiotics but commented that it is usually an incidental finding, and antibiotics do not always help the symptoms. He prescribed metronidazole 2g daily to be taken in divided doses (400mg morning, 800mg midday and 800mg night) for 10 days. She also took azithromycin as recommended by CDD.  

Symptoms improved markedly after a week on antibiotics. The patient is now addressing her malabsorption issues with a clinical nutritionist from Designer Diets in Sydney as result of the damage to her gastrointestinal system from IS.