Human case of gastric infection by a fourth larval stage of Pseudoterranova decipiens (Nematoda, Anisakidae) Relato de parasitismo por nematódeo Anisakidae em homem

Only three cases of human infection by anisakid nematodes have been reported in Chile since 1976. In the present case, an anisakid worm, identified as a fourth-stage Pseudoterranova decipiens larva, was removed with a gastroendoscopic biopsy clipper from the stomach of a 45 year-old man from southern Chile. The patient, who presented acute epigastric pain and a continuous sensation of having an empty stomach, reported having eaten smoked fish. The worm was fixed in 70% ethanol and cleaned in lactophenol for morphological study. The morphometric characteristics of the worm are described and drawn. Anisakid larvae in fish flesh can be killed by freezing or cooking. Nematode infections. Anisakiasis.

Human case of Pseudoterranovosis Mercado, R. et al.

Infecciones por nematodos. Anisakiasis.
In Chile, four food-borne helminthic zoonoses are associated with the consumption of raw, smoked or undercooked fish. Two of those infections are caused by the nematodes Anisakis simplex and Pseudoterranova decipiens, and the other two are produced by the cestodes Diphyllobothrium latum and Diphyllobothrium pacificum. Except for D. latum which infects salmonids and authocthonous fish introduced into sweetwater 16 , other parasites are transmitted to man by his eating sea fish 9,15,17 .
Human infections produced by larval stages of P. decipiens are commonly named anisakiasis in the broad sense 5 , codworm anisakiasis 12 or Pseudoterranovosis according to standardized nomenclature of animal parasitic diseases 6 . Although third or fourth stage larvae of anisakid worms can produce human infections, the latter are only rarely found 4,5 .
To the present day in Chile, only three cases of human infection produced by anisakid worms have been reported 1,14,20 . It is described a new case of human infection, produced by a fourth larval stage or P. decipiens in a patient who resided in the south of Chile.
A 45 year-old man, living in Coihaique City (45 o 33'S Lat., 72 o 06'W Long) travelled periodically to Santiago on business. In June 1995, he presented acute epigastric pain and a sensation of an empty stomach which continued for three days. No other symptoms were registered. He was given a gastric endoscopy without any other laboratory exams and had no morbid antecedents. The patient reported having eaten smoked fish. Endoscopic study showed a nematode fixed to the slightly, hyperaemic gastric mucous in the posterior region,whence it was removed directly with a gastroendoscopic biopsy clipper.
The nematode was fixed in ethanol 70% and was later cleaned in lactophenol for morphometric studies (Figure). Measurements are in mm: the body of the larva was 32.2 in length; greatest diameter near midbody was 0.72. The mouth had three lips: a dorsal one showed two double papillae and each subventral lip presented a single double papilla. Interlabia and boring tooth were absent. Excretory pore opened between two subventral lips. Nerve ring was 0.41 from anterior end. Esophagus or preventricule measured 2.2 in length and 0.27 at maximum width. Ventricule and intestinal cecum were 1.1 in length. The tail was 0.2 in length with a knoblike process.
The morphometric characteristics of the recovered larva corresponded to a fourth stage of P. decipiens 4 and it is the first report of this larval stage in a human case in Chile.
Nagano 10 reported that human cases of infection produced by P. decipiens in Japan involved the stomach of the patients. Our observation is in agreement with that finding.
About 18 species of marine fish (Table) have been reported as hosts of the third larval stage of codworm    18 . Genetic studies of P. decipiens recovered from sea mammals captured in the north Atlantic and Norwegian and Barents seas showed that P. decipiens is a complex of at least three sibling species 13 . Sapunar et al. 14 described the first case of anisakiasis in Chile in a women of 35 years old from Santiago. In this case one larva of Anisakis sp. was expectorated by the patient and an other was eliminated with the faeces after treatment with mebendazole. Apt et al. 1 described a second case in a female of Japanese ancestry. A worm was removed with the biopsy forceps from the stomach of the patient. It was identified as a Pseudoterranova sp. larva. Verhamme and Rauher 20 described a case of intestinal anisakiasis in a Belgian tourist who probably acquired the infection in Chile. Worms were not recovered from this patient.
Anisakid larvae present in fish flesh would be killed by freezing at -20 o C for 60 hrs 9 . According to Margolis 7 cooking 3 cm-thick fish fillets of at 70 o C or 60 o C for 7 or 10 minutes, respectively, should kill any codworm larvae present.