I've seen 'holes in the ground' latrines in W. Africa (and used them!) They don't flush, and the contents stay down in the hole for usually about a month, until the concrete tank is emptied. The stench is beyond description, and of course they harbour cholera, typhus and many other dangerous germs. Most people I met often had diarrhea and those germs too stay in the tank. Rats, cockroaches, even snakes love those latrines, and during the night you risk being bitten if you need the toilet. There's no such thing as toilet paper, you take a little plastic kettle-shaped pot of water in with you, and rinse yourself. If it rains (which in those parts it does, torrentially) the whole latrine is under about six inches of water mixed with the contents of the tank. When the lorry arrives to empty it, using a large vacuum pipe, everyone vacates the area or puts a cloth over their face. No-one is interested in keeping the surrounds of the hole clean, so any faeces or urine which lands there, stays there. My husband used a toilet like this all his life. They just don't have the funds to create a whole sewage system, such as Joseph Bazalgette designed for the London area in the 1860's. People also urinate and defecate in the street. I don't know what the answer could be without a large investment of money. Most Africans are not worried about toilets, they're trying every day to find enough to eat for themselves and their children.