The infectivity and antigenicity of Toxocara canis eggs can be retained after long-term preservation

• Published in: Annals of tropical medicine and parasitology Vol. 98; no. 3; pp. 251 - 260
• Main Authors: Chung, L.-Y., Fang, B.-H., Chang, J.-H., Chye, S.-M., Yen, C.-M.
• Format: Journal Article
• Language: English
• Published: Leeds Taylor & Francis 01.04.2004; Maney Publishing
• Subjects: Animals; Antibodies, Helminth - biosynthesis; Antigens, Helminth - immunology; Biological and medical sciences; Cytokines - biosynthesis; Electrophoresis, Polyacrylamide Gel; Eosinophils - pathology; Formaldehyde; General aspects; Human infectious diseases. Experimental studies and models; Infectious diseases; Larva - growth & development; Leukocyte Count; Liver - parasitology; Medical sciences; Mice; Mice, Inbred BALB C; Preservation, Biological - methods; Toxocara canis - growth & development; Toxocara canis - immunology; Toxocara canis - pathogenicity; Toxocariasis - immunology; Toxocariasis - parasitology; Zygote - growth & development; Toxocara canis; Egg; Infectivity; Helmintha; Tropical medicine; Nemathelminthia; Invertebrata; Nematoda; Long term
• ISSN: 0003-4983; 1364-8594
• DOI: 10.1179/000349804225003280

Suspensions of fertilized eggs of Toxocara canis were mixed with 2% neutral formalin and preserved at 4°C. When, after storage for 0, 12, 18, 21 and 24 months, samples of the eggs were incubated at 30°C for 12 days, 96.8%, 92.6%, 74.1%, 51.0% and 19.3% of the eggs in the samples were found to embryonate. The embryonated eggs produced from the fertilized eggs preserved (in 2% neutral formalin at 4°C) for 0, 12, 18 and 21 months were then tested for their infectivity to BALB/c mice, each mouse being given 800 embryonated eggs. The numbers of larvae recovered from the mice and the sites from which they were recovered, 2 or 14 days post-infection, appeared unaffected by the length of storage of the eggs. The infected mice all had similar eosinophil counts in their peripheral blood and similar serum titres of Toxocara-specific IgM and IgG antibodies, and cultures of their spleen cells produced similar amounts of interleukin-4, interleukin-5 and interferon-γ when stimulated with concanavalin A. The results of SDS-PAGE indicated that egg preservation for at least 21 months had no effect on the excretory-secretory antigens in samples of medium from cultures of infective larvae released from the eggs. In summary, at least 50% of the fertilized eggs preserved in 2% neutral formalin at 4°C for 21 months could fully embryonate and then had the same infectivity and antigenicity as embryonated fresh eggs.