Soil-transmitted parasitic nematodes infect over one billion people and cause devastating morbidity worldwide. Many of these parasites have infective larvae that locate hosts using thermal cues. Here, we identify the thermosensory neurons of the human threadworm Strongyloides stercoralis and show that they display unique functional adaptations that enable the precise encoding of temperatures up to human body temperature. We demonstrate that experience-dependent thermal plasticity regulates the dynamic range of these neurons while preserving their ability to encode host-relevant temperatures. We describe a novel behavior in which infective larvae spontaneously reverse attraction to heat sources at sub-body temperatures and show that this behavior is mediated by rapid adaptation of the thermosensory neurons. Finally, we identify thermoreceptors that confer parasite-specific sensitivity to body heat. Our results pinpoint the parasite-specific neural adaptations that enable parasitic nematodes to target humans and provide the foundation for drug development to prevent human infection.