‘I have sometimes also seen animalcules a-moving very prettily; some of ’em bigger, others a bit less, than a blood globule, but all of one and the same make. Their bodies were somewhat longer than broad, and their belly was flatlike, furnisht with sundry little paws.”
While it’s hard not to be charmed by this description of a mysterious creature with pretty movements and sundry little paws, all is not as it seems. The comment was made by 17th-century Dutch tradesman and scientist Antonie van Leeuwenhoek, who, while peering through a homemade microscope at a speck of his own faeces, recorded what’s thought to be the first sighting of the intestinal parasite that causes giardia infection.
Van Leeuwenhoek, now known as the father of microbiology, had no idea of the link between the creature he saw through his microscope and the illness it causes. But giardia has proved immensely successful at spreading disease, infecting hundreds of millions of people around the world.
New Zealand has a higher incidence of giardia infection than other developed countries – our rates of infection are up to nine times those in similar countries.
In the year to April, 1800 people suffered the stomach cramps, diarrhoea and vomiting that make a giardia infection such a gruelling experience, according to official figures. The real number is certain to be much higher, as most people who have the infection do not see a doctor or provide faecal samples for lab testing.
The infection has been particularly common recently: 555 cases were notified in the three months to March, compared with 470 in the same quarter last year and 375 in the three months to December.
The symptoms of giardia infection usually appear about a week after exposure to the parasite. Mercifully, they tend not to last long. Most people recover within a few days, although without treatment they may remain infectious for months, and can spread the parasite to others even when they no longer have symptoms.
Last year, public health researchers from the University of Otago, Wellington (UOW) published the first comprehensive epidemiological analysis of the incidence of giardia since cases were made notifiable by law in 1996. Writing in the New Zealand Medical Journal, Associate Professor Michael Baker, from UOW’s department of public health, said the annual cost of giardia infection in healthcare and lost work time was almost $1 million – and it would be much higher if non-notified cases were included.
Giardia lives in the guts of humans, cows, sheep, cats, dogs and other animals, and is passed on in faeces. The parasite can survive for a long time in cold water, such as lakes, rivers, streams and tank water. Many New Zealand waterways have been polluted by toilet waste and rubbish, and the Department of Conservation says the chances of contracting giardia from water are increasing.
People can catch a giardia infection from contact with an infected person or animal, or by swallowing parasites living in contaminated food or water. Although it’s often assumed that farm animals are the main source of the gut infection in New Zealand, Baker’s report says giardia is usually transmitted from person to person. His study also found that about one in five people with giardia were infected while travelling overseas.
Other ways of becoming infected include drinking untreated water, taking part in recreational activities in fresh water or swimming pools, going to schools or childcare centres and eating at food outlets.
Giardia is particularly common in young children, and in people aged 30-39 – many of whom are thought to be parents of infected children, especially parents who have babies in nappies.
Dr Stephen Palmer, medical officer of health for Hutt Valley DHB’s regional public health unit, says the unit saw an increase in giardia cases at the end of January. “The weather was miserable till then, so late January was when people started going out to swim in the river.”
Palmer says there’s little public awareness of the water quality of the country’s rivers and streams, and many people have no idea of the risk of catching gut infections such as giardia, cryptosporidium and campylobacter from contaminated waterways.
Baker believes New Zealand’s high rate of giardia and its economic cost to the country justify more effort being put into preventing the disease. He suggests this should include continuing to improve the quality of drinking water, giving overseas travellers advice on avoiding giardia and providing public education about hygiene measures, such as hand-washing and nappy-changing.