Assessment of the Prevalence of Angiostrongylus cantonensis Infection in Gastropods of Puerto Rico

Biological infections of the zoonotic nematode Angiostrongylus cantonensis have caused neuroangiostrongyliasis (NAS) in many people around the world and have impacted the neurological health of various wild and domestic animals. Several Caribbean countries have reported cases of NAS caused by the rat lungworm; however, the most recent study in Puerto Rico was in 1984. Here, we conducted quantitative polymerase chain reaction (PCR) to evaluate levels of A. cantonensis DNA in 205 gastropod samples from 20 different species across eight sites in Puerto Rico. An overall estimate of 35.6% (n = 73/205) was determined to be positive. We found that approximately 67.2% (n = 45/67) of Parmarion intermedius and Parmarion martensi were PCR positive for A. cantonensis DNA. Parmarion spp. and Caracolus spp. samples contained significantly greater concentrations of A. cantonensis DNA by several orders of magnitude than all of the other species tested, suggesting higher infection levels. Gastropods collected from three sites on the northwestern side of the island yielded significantly less A. cantonensis DNA than midregion sites, suggesting lower infection levels. Angiostrongylus cantonensis was found in several areas across Puerto Rico, with the highest nematode prevalence found at somewhat higher elevations (471-532 meters). An extensive temporal study of A. cantonensis in gastropods as well as in the definitive rat host would provide a better understanding of the widespread prevalence and biogeography of this parasite in Puerto Rico, and thus, it would provide a better estimate of infection risks to humans and other animals.