While travelling through a small rural village, a couple of university students spot a street vendor selling sausages. They are hungry, and the price is cheap. One student comments, "I wonder where those came from. There isn't any supermarket here, and I haven't seen a butcher shop." Hunger is the deciding factor. The sausages taste good, even though they're cold. They move on to their next destination. However, two days later, they both develop abdominal pain, nausea, and diarrhea. One of them notes a mild fever. These symptoms subside, but a week later both students have muscle pain, weakness, and fever.

The image reveals an encysted larval form of Trichinella spiralis.

Answer: E The findings suggest trichinosis, an infection by Trichinella spiralis. The ingested meat contains cysts that release larvae on digestion which migrate to intestinal mucosa and mature to mate. The female worms release larvae into vascular channels that are then carried throughout the body to enter skeletal muscle fibers. Larvae tend to be concentrated in the most active muscles.

Answer: C Cooking destroys the encysted larvae in the infected meat.

Answer: E Historically, the domestic pig has been the source for most human infections, though wild animals such as boar or bear can be a source. Animals must be omnivores to serve as a host. Regulation of meat production practices (not feeding uncooked animal parts to other animals) has markedly reduced the incidence of trichinosis in places where such regulations are in force.