Hepatobiliary Ascariasis in a Piglet

Abstract

Purpose: Ascariasis caused by the helminth Ascaris suum is the most common parasitosis of swine worldwide and it may involve all age categories of pigs. The present study reports an unusual localization of A. suum worms in the biliary system of a piglet slaughtered for human consumption.

Methods: The liver was subjected to ultrasound scan and pathological examination. The isolated worms were morphologically examined and the DNA was extracted for the molecular identification of the species involved.

Results: A total of 43 preadult nematodes were found within the gallbladder and the bile ducts. Parasites were morphologically identified as belonging to the genus Ascaris and molecularly as A. suum. At gross examination, the liver was moderately enlarged, with the bile ducts severely dilated. A chronic inflammatory infiltrate was noted, often centered around ectatic bile ducts (up to 5 mm in diameter), lined by hyperplastic epithelium and filled with sections of nematodes. The worm sections showed smooth cuticle, coelomyarian musculature, and an intestinal tract lined by columnar, uninucleated cells within a pseudocoelom. The ex vivo ultrasonographic examination of the liver allowed the visualization of several nematodes in the bile duct lumen and could be suggested for in vivo diagnosis. Unfortunately, the absence of the intestine did not allow to define the pathogenesis of the infection.

Conclusion: Although, given the unusual nature of this finding, it is difficult to identify predisposing factors for this A. suum localization, it suggests that ascariasis should be considered in the differential diagnosis of pigs with hepatobiliary disease.

Keywords: Ascaris suum; Bile ducts; Parasitology; Pig; Ultrasound.

Fig.1

Gross examination of the liver, with several preadult specimens of 7 cm mean length (A), and a detail of nematodes occupying the bile ducts (B). The scale bar in A has centimeter (cm) as unit

Fig.2

Ex vivo ultrasound image of the liver. The white arrows indicate a longitudinal parasite section, white arrowheads indicate the thickened walls of the bile ducts. *Liver parenchyma

Fig.3

Transverse (A) and longitudinal (B) histological sections of nematodes with a smooth cuticle, coelomyarian musculature, intestinal tract lined by columnar uninucleated cells within a pseudocoelom. H.E bar 100 µm