The companionship of a pet can help us be happier, and they might even let us be healthier, too. Scientists are finding more evidence that animals provide a key ingredient to human development and health that could counteract certain allergies, whether they come on in childhood or later in life.
For a long time, we've understood that many bacteria, viruses and fungi are harmful and need to be eliminated from our indoor environment. But more and more, health experts have been finding the surprising benefits of routine exposure to common micro-organisms. Scientists coined the term "microbiome" to describe the trillions of bacteria and other organisms that live within our bodies and throughout our homes. And rather than destroying them, it's becoming clear that we need to do more to protect them, as they can help our bodies function normally.
A wide variety of microscopic lifeforms call our stomachs, our skin and our floors home. These bacteria and fungi help humans digest food into nutrients, and can prevent the growth of the really bad germs. We are also learning that these bacteria might have a role to play in the development of allergies. It's now commonly accepted that as our homes and bodies have gotten cleaner, we've seen the incidence of allergies rise in children and adults.
Animals, including dogs and cats, may be a key vector for getting these good bacteria into our lives. One recent study published in The New England Journal of Medicine found that a group of Amish children, raised on a farm in close proximity to many animals, had much lower rates of allergies and asthma than another group of Hutterite children, who were not raised with animals. The kids in the study lived largely similar lives apart from their interaction with animals.
Scientists explain these findings as evidence of the microbiome in action. In general, Amish children are known to suffer from allergies far less than their typical American counterparts. Health experts think this is because of the bacteria-rich environment they are raised in, which allows their immune systems to mature normally.
Common household pets like cats and dogs are known to be among the most common causes of allergy symptoms in the U.S. The Asthma and Allergy Foundation of America estimated around 30 percent of U.S. adults experience regular allergic reactions to pets, with cats accounting for twice as many cases as dogs. However, living with these pets may introduce or aggravate nonallergic conditions in certain people, an important distinction that is often overlooked.
"Toxoplasmosis may be present in up to half of the world's population."
One particular concern involves a microscopic parasite known as Toxoplasma gondii, which causes the condition toxoplasmosis when it infects humans and other animals. T. gondii is one of the most prolific organisms known to science – up to half of the world's population is thought to be chronically infected with the parasite at any given time. However, in healthy adults, the parasite does not cause any noticeable symptoms.
T. gondii is particularly good at reproducing in cats, allowing it to be transferred to humans through incidental contact. In healthy people, toxoplasmosis may cause a brief period of mild flu-like symptoms that pass in a few days. Afterward, the parasite may lay dormant in the body for the rest of the host's life, going totally unnoticed in most people.
Treating and preventing
Problems from toxoplasmosis might arise in certain populations of people, including pregnant women, babies less than six months old and anyone with a weakened immune system (due to a disease like HIV, or following cancer treatment or an organ transplant, for example).
Pregnant women may face the most prevalent risk to toxoplasmosis, but only in women who had never come in contact with the organism prior to conception. If this is the case, T. gondii may cross the placenta and disrupt fetal development, possibly leading to birth defects or miscarriage.
For this reason, pregnant women can be tested for the parasite and take precautions if it is found they have not already been infected. These precautions would include avoiding changing a cat's litter box until it can be disinfected. Indoor cats that eat only cooked, canned food generally present the lowest risk. Families with infant children or immune-compromised residents should take the same steps.
Cats are not the only vector for toxoplasmosis infection, however. Eating undercooked meat or unwashed produce, drinking unfiltered water and gardening without gloves all increase the risk of infection. Unfortunately, there is still no known cure or vaccine against T. gondii, but researchers are working to develop one.
