Originally Posted by mrsD

Metronidazole and its cousin Tindamax, are well known causers of nerve damage.

A whole family with chronic diarrhea? Could be other causes there. But it does warrant medical evaluation.

Closely look at your foods. The gums added to most processed foods, including dairy and ice creams (carob bean gum aka locust bean gum), can cause issues for people with a gut biome that ferments this complex carb. Before embarking on the giardia research remove the "gums" from your food intake and see if there is an improvement.