Which of the following human behaviors contributes significantly to the spread of parasites?

The option highlighting poor sanitation and hygiene practices is significant in the context of parasite transmission for several reasons. When sanitation and hygiene measures are inadequate, the likelihood of pathogen survival and spread increases dramatically. For instance, improper disposal of human waste can lead to the contamination of water sources with fecal matter, which may contain a multitude of parasites such as Giardia or hookworms. Similarly, a lack of proper handwashing practices can facilitate the transmission of parasites through ingestion or contact with contaminated surfaces.

In areas where sanitation is poor, food can also become a vector for parasites. Contaminated fruits, vegetables, and undercooked meats can harbor parasites that pose health risks to individuals who consume them. In contrast, regular physical exercise, a high-protein diet, and even frequent travel to urban areas do not have the same direct and established link to the spread of parasites as inadequate sanitation and hygiene practices do. These behaviors may have varying effects on health, but they do not create the conducive environment that poor sanitation does for the propagation of parasitic infections.