Season 3, Episode 7: One hand washes the other
Still mourning Joanna’s death from the C. difficile infection, David and Carlos head to California to track down the source of the bacteria and uncover how it became antibiotic resistant. It would appear that nature – lightning, in particular – played a role in creating this new “bug.” But the NorBAC scientists also find many signs suggesting that human activities may share some of the blame for how the bacteria came to be, and for why people are getting – and staying – sick …
It’s only natural – or is it?
In the last installment of ReGenesis: Science & Society, we touched on the fact that infectious diseases seem to be “popping up all over the place.” You might say, “it’s only natural” – evolution, after all, is a natural process and this is no less the case for viruses and bacteria than for other organisms.
But just as our actions can impact upon our environment and the macro-organisms that are a part of it, human activities can affect viruses and bacteria in profound ways: We can intentionally kill undesirable microbes, and we can unwittingly make them stronger. We can control their spread, and we can cause them to spread in ways and to distances that they normally would not. In this episode, we see examples of each of these cases.
Clean up the mess
While investigating the California farm, David and Carlos came upon a pit toilet that was not exactly what you would consider a model of good sanitation. Bacteria from human waste – like C. difficile and E. coli – was escaping the pit and contaminating the surrounding soil and groundwater. Poor farming practices can have much the same effect. As the workers learned the hard way, drinking contaminated water is a sure way to pick up infectious diseases.
This is a real world problem – a human problem more than a bacterial one – and an all too common one at that. Improper sanitation and contaminated water are the cause of countless infections every year all over the world, particularly in developing countries. We could try to treat everyone who becomes infected as a result, but wouldn’t it be better if the infections didn’t happen in the first place?
Public health infrastructure and effective sanitation programs are among the keys to such prevention. If, and when, those initiatives fail, scientists can lend a hand through the development of innovative approaches to decontamination, from chemical water treatment to bioremediation, and by creating more effective vaccines to protect against infection.
Good to the last pill
Of course, even with clean water, good sanitation and effective public health initiatives in place, infections will happen. And when they do, they can often be effectively treated with antibiotics or antiviral drugs. But antimicrobials also have a dark side – by killing off susceptible microbes, they select for resistant ones, increasing the relative abundance of these “die hards.”
In this episode, the NorBAC team has evidence to suggest that residual antimicrobial chemicals from hand soap and other home cleaning products caused the selection of antibiotic-resistant bacteria in the farm’s soil. The same sort of thing can happen in people taking antibiotics, particularly if they stop taking the drugs once they no longer feel infected.
A full course of antibiotics is meant to kill all of the bacteria infecting a person, from the weaker, more susceptible bacteria, to the hardier, more resistant bacteria. By taking only a part of that course – for example, three days of a six-day regimen – a person may kill off only the weak bacteria, leaving some of the more robust bacteria alive and capable of reproducing. The result: a bacterial community made up largely of more resistant bacteria.
Selection like this steers bacterial evolution and can bring about the emergence of strains made up entirely of highly resistant bacteria. The resistance is natural, but in some cases people’s actions – more so than nature’s influences – are responsible for the selection and increased abundance of that resistance. In effect, the very drugs that help us, used incorrectly, can cause a great deal of harm down the road.
Should I stay or should I go?
In order for vaccines or antibiotics to work, people first need to go to a doctor to acquire them. This seems obvious enough, but it’s not as straightforward an issue as it might seem.
For some people, going to the doctor can be frightening. Perhaps they are afraid of needles and fear the pain that comes with vaccination. Or maybe they find certain tests uncomfortable or embarrassing. Perhaps they fear something far worse – like being arrested, or harassed, or discriminated against. Sometimes these fears stand in the way of people seeking health care even when doing so would be prudent.
In this episode, Carlos is approached by Elvia, the daughter of a farm worker, Felipe, who is ill and showing symptoms similar to those Joanna had. Felipe needs a doctor, but won’t go to the clinic. Like most of the workers on this farm, Felipe is living and working illegally in the US and he’s afraid of being caught – some other sick workers went to the clinic but did not return because, as Elvia says, “Immigration watches the place.” Indeed, studies have shown that illegal immigrants often avoid seeking health care, including emergency care, out of fear that doing so may lead to deportation.
Sometimes, getting health care requires that we incur some costs – economic, social, even emotional costs. But think about the costs of avoiding necessary health care. In this case, the infection claimed Felipe’s life, but because it was not contagious, no one else got sick as a result of his reluctance to go to a doctor. But what if it had been contagious? By not seeking medical attention, for any reason, a person infected with a contagious disease could end up spreading the disease to many people in his or her community.
What’s the common thread here? Human action or inaction can have a huge impact on the emergence and spread of infectious diseases. We look to science to help us to combat infections in numerous and fantastic ways, but when it comes down to it, we also need to look to people to help themselves and each other, and to help science work its magic.
More food for thought
Q: What other ways can people influence the emergence or spread of infectious diseases? What can be done to prevent or limit those influences?
Q: Where vaccines are available, are individuals morally obligated to be vaccinated against contagious infectious diseases? Why or why not?
Want to read and learn more?
To read more about drinking water and ways to ensure its safety, visit these sites:
www.hc-sc.gc.ca/ewh-semt/water-eau/drink-potab/index_e.html
www.epa.gov/ebtpages/watedrinkingwater.html
To learn about antibiotic resistance and its causes, go to:
www.hc-sc.gc.ca/iyh-vsv/med/antibio_e.html
To read more about infectious diseases, including those that are preventable through vaccines, visit:
www.phac-aspc.gc.ca/id-mi/index.html
