Waste

To the basics. . . the most fundamental reason for building a latrine is to separate humans from human waste.  Human waste has some nasty stuff in it.  If you want a lot of detail, read this.  Otherwise, here’s my summary. 

First off, to establish my lack of decorum, I’ll refer to solid waste as poop, shit or feces depending on my mood.  Liquid as pee or urine.  Together, I’ll call is waste.  Exposure to human waste exposes one to contact with myriad communicable diseases: intestinal infections, cholera, typhoid, dysentery, diarrhea, hookworm and shistosomiasis, to name a few.   These come in the form of Bacteria (E.coli, cholera, typhoid, leptospirosis), Viruses (poliovirus, rotavirus), Protozoa (giardia) and Parasites (hookworm, roundworm, tapeworm, schisto, liver fluke).  All of these are in feces.  Schisto, e.coli, typhoid and leptospirosis can come in the urine—it’s perhaps not as ‘sterile’ as people might have you think. 

Some of this will become more relevant later, but protozoa and parasites are big, bacteria are medium-sized and viruses are small.  Once all these bugs exit the human body, their life spans are limited.  As a rule of thumb, bacteria and protozoa are relatively fragile and can last from days to a few months.  Viruses and parasites are more robust and can last from months to years.  If they stay in the wastewater, their lives are longer than if they move into soil.  In soil, they lose their ideal conditions and die or are replaced by other, more mundane bugs.  Soil also physically inhibits the movement of the bugs.  When moving through soil, the big bugs are captured before the smaller bugs and thus less likely to contaminate ground water.  Dry conditions are typically more hostile to the bugs than wet conditions.  There are aerobic bacteria (meaning they need oxygen in addition to a food source to survive), anaerobic bacteria (thrive in no oxygen environments) and facultative bacteria (bacteria that can survive in both environments by switching their metabolic processes). 

None of these bugs matter, however, unless humans come into contact with them.  The vectors of transmission include fecal-oral, skin penetration and insect and rodent.  In essence, we get sick via drinking contaminated water, by touching food or our mouths with contaminated hands, by flies moving from feces to food, by mosquito bites from mosquitoes that have bred in waste, by swimming and bathing in contaminated water and by walking on contaminated soil.  

Nearly all of this can be prevented by incredibly simple latrines.