Baylisascaris procyonis occurs naturally as a parasite of raccoons (Procyon lotor), and may cause visceral larva migrans and CNS disease in humans, other mammals and birds.
Early third-stage larvae measured 49-60 u in diameter and 928 1059 u in length. Late third-stage larvae measured 75-84 u in diameter and 1479-1676 u in length. The head was rounded and slightly swollen, while the lips were ill-differentiated and not pro tuberant. The esophagus was clavate, strongyliform, terminated in a pyriform bulb, and constituted about 1/8 of the total length. The lateral alae were well developed. The tail was dorsally curved and hook-like. B. procyonis third-stage larvae were studied by scanning electron microscopy. Three small poorly differentiated lips appeared surrounding the anterior tip of the esophagus. Four primitive button-like flat cell masses were seen on the primary lips corresponding to the external ring of the labial papillae. Three pairs of pulp cells appeared apically on the growing primary lips corresponding to the internal ring of primary labial papillae. Two amphidial pores were located laterally on the primary subventral lips. A dorsal cervical median crest was present on the anterior 1/6 of the body length, flanked by a submedian groove on each side. A dorsal median groove extended along the body to the anal region. The tail was sharply curved dorsally, narrowly and deeply segmented, with a blunt rounded terminal knob.
Somatic migration of the second-stage larvae in occurred exper imentally injected guinea pigs, with development of larval granulo maslomas. The second moult occurred within 10-21 DAI. Small mammals as intermediate hosts may be necessary to the life history of B. procyonis.