Brazil has some regions with very low education, and very little in the way of outside influence. I wonder where these folks lived. It sounds like they weren't in the deep jungle, because they mention having a car. But, nonetheless, not everywhere is as educated. They may have heard that its a 'luxury' item (it certainly seems as though they were gathering for a celebratory type meal... a chance to share 'the finer things' in life...) but didn't understand the full dimension of what makes it a luxury item.
Such a shame. Hopefully they all recover. Any updates that you've seen on the family?