Parasites of this genus, and related genera, infect a variety of mammals. All can be serious pathogens. The large adults (20-30 long) live in the tissues, including the musculature and central nervous system, so can cause damage to the tissues they inhabit. In addition, the female deposits eggs into the bloodstream, which often hatch there, and the first stage larvae are trapped in the capillary beds of the lungs. There they break through into the air spaces. Each larva is small and causes minimal damage, but millions of larvae per day may be produced in a heavy infection and the cumulative damage can cause pneumonia or death. Related genera are known to be transmitted transplacentally.