YOUR LEG ACHES as heavy beads of sweat drip from your brow. It’s been hours since you began hiking and your water is warm and far from refreshing. You arrive at a seemingly pristine creek and the urge to fill your canteen is overwhelming. The water is cool and fast-moving – you assume it’s safe to drink. A week later, however, you realise your mistake. A quick streamside sip could leave you doubled over with abdominal pain, vomiting, fever — and worse.
Although scooping water straight from a river can be tempting, it is important to consider the entire catchment. Bacteria, viruses and chemicals can contaminate even remote water sources in wilderness areas.
Any site downstream from a town, camping ground or recreation area may be contaminated with raw sewage and street overflow. Further away, agricultural run-off can leach through the soil, eventually filtering into distant water bodies. Mining introduces chemicals, heavy metals and sediments into waterways, and naturally occurring chemicals, such as arsenic, can be there, irrespective of human activity.
Although suspicious colours, odours or suspended particles may warn us that water is bad, the organisms that do the most harm are microscopic.
“Even in areas where the risk of encountering harmful waterborne contaminants may be low, the severity of the potential outcome is high,” says Matt McClelland, director of Bushwalk Australia, an online resource and e-mag.
Waterborne contaminants fall into three categories: chemicals, algal blooms, and pathogens (including viruses, bacteria and protozoa). Ingesting chemicals will not usually cause significant harm after one exposure. But algae, which flourish when exposed to nitrogen- and phosphorus-rich fertilisers, can be toxic. Cyanobacteria, or blue-green algae, accumulate in warm, stagnant, nutrient-rich water. They produce toxins that are among the most potent of poisons and pose a variety of health risks when ingested, inhaled, or touched. Symptoms can include rashes, abdominal pain, vomiting, liver swelling, kidney damage, and respiratory paralysis.
Waterborne viruses, including hepatitis, rotavirus and enterovirus, can occur if there are human settlements within the catchment area. “Viruses are only found near sources of human faecal contamination,” says Greg Jackson, director of the Queensland Department of Health’s Water Program. “You won’t find viruses in a natural source unless there’s a septic tank upstream. Since viruses are unprotected bundles of DNA, they won’t survive long outside a host.”
Bacteria such as Escherichia coli and Campylobacter are common in Australia and can be spread between species. Transmission occurs when faecal matter from animals or humans enters a water supply. Bacteria associated with dead animals near water can also make you ill. Consuming bacteria by drinking, cooking with or swimming in contaminated water can result in a violent case of gastroenteritis.
Protozoa are single-celled organisms that draw nutrients from their hosts. Some are harmless, but others can be life-threatening: Giardia and Cryptosporidium, for example, can survive outside a host for long periods.
Collect water that is running, clear and free of debris – and all water needs to be filtered. “With filtration, the water must be fairly clean to start with, or else the materials that are filtered out will collect in the filter and provide a medium for bacterial proliferation,” Greg says.
After filtration, water should be boiled, treated with chemicals, or exposed to UV radiation. “Boiling is the only method that achieves 100 per cent removal of all pathogens,” Greg says. “At 85°C, nearly all disease-causing organisms are killed.”
If boiling is impractical, adding iodine or chlorine tablets is a common way to treat filtered water. “Many chemical treatments don’t kill the organisms, but, rather, render them sterile so that they cannot reproduce in your gut,” Matt says. “[But] the amount of chemical added and the length of time that the water is exposed to it must be precise.”
When using UV treatment, the water must be very clear to begin with, because UV light can’t easily pass through cloudy fluids. The light can be administered by inserting a UV pen torch into your water bottle for a minute. The radiation deactivates bacterial DNA, which prevents micro-organisms from reproducing and causing disease.
Common threats in untreated water
Viruses and chemicals are rare in outback waterways, but bacteria, parasites and algal blooms are more common. In national parks, sources of contamination include roads, camping grounds and visitors centres.
Cyanobacteria range in colour from green–blue, to brown–red and form surface mats of scum or foam. They release cyanotoxins, which, on contact with skin, can cause rashes, hives or blisters. When inhaled, the bacteria can cause cold- or asthma-like symptoms. Ingestion causes gastroenteritis, as well as liver, kidney and nervous system toxicity. In severe cases, patients may require intensive care and artificial respiration.
2. Cryptosporidium parvum
This parasite is found in the faeces of infected humans and cattle. Ingesting it can cause cryptosporidiosis. Symptoms include diarrhoea, abdominal cramps, fatigue, loss of appetite, nausea and vomiting. These can persist for several weeks. The parasite consists of a single cell, known as an oocyst , which is protected by a tough shell. Once oocysts enter the body, they release sporozoites which reach the intestines and lungs. Here, they reproduce rapidly, and may or may not cause illness.
3. Giardia lamblia
A common waterborne parasite around the world, Giardia affects 200 million people each year. Symptoms include diarrhoea, dehydration and abdominal pain. The hardy, spore-like cysts are resistant to UV, iodine and chlorine, and as few as 10 can cause infection. Giardia begins to wreak havoc in your gut 1–3 weeks after digestion. Stomach acids break down the hard shells of the cysts, releasing ‘trophozoites’ into the small intestine. Here, they reproduce and attach to the intestine. Treatment involves antibiotics and hydration therapy.
4. Campylobacter jejuni
Campylobacter releases toxins in the gut , causing diarrhoea, fever, stomach cramps and vomiting. Generally, the bacteria cannot survive outside the gut for long. Symptoms may appear 1–10 days after ingestion and may last six days. This is a common precursor to Guillian-Barré syndrome, an autoimmune condition that causes paralysis.