First record of larvae of Hysterothylacium (Nematoda: Anisakidae) with zoonotic potential in the pirarucu Arapaima gigas (Osteichthyes: Arapaimidae) from South America

Abstract Third-stage larvae (L3) of Hysterothylacium sp. were collected by the first time in juveniles of pirarucu Arapaima gigas farmed in the Rio Preto da Eva, Amazonas state. Ninety-eight (98) out of 100 examined fish showed to be parasitized. Five hundred and ninety larvae of Hysterothylacium sp. were collected from the intestines, stomach and pyloric caeca. The mean intensity of parasite indexes was 6.02 (±5.75) ranging from 1 to 40 larvae per host and the mean abundance was 5.9 (±5.76). The A. gigas is the new host record for larvae of Hysterothylacium sp. in Brazil, and this is the first record of larvae of Hysterothylacium (Nematoda: Anisakidae) with zoonotic potential in the pirarucu from South America.