The infectivity and antigenicity ofToxocara caniseggs can be retained after long-term preservation

Abstract

Suspensions of fertilized eggs of Toxocara canis were mixed with 2% neutral formalin and preserved at 4 degrees C. When, after storage for 0, 12, 18, 21 and 24 months, samples of the eggs were incubated at 30 degrees 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 degrees 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-gamma 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 degrees C for 21 months could fully embryonate and then had the same infectivity and antigenicity as embryonated fresh eggs.

Toxocara canis larvae viability after disinfectant—exposition

“…Nevertheless, Ayçiçek et al (2001) proved that sodium hypochlorite had no effect on T. canis eggs, thus confirming the results of Juris and Breza (1988). Likewise, at least 50% of the fertilized eggs preserved in 2% neutral formalin at 4°C for 21 months could fully embryonate and then have the same infectivity as embryonated fresh eggs (Chung et al 2004).…”

Human toxocariasis: contribution by Brazilian researchers

“…In addition, CHUNG et al 30 observed a greater survival rate when the eggs were maintained at 4 o C. However, certain environmental factors can influence the evolution of Toxocara eggs in the soil 48,54 . Under experimental conditions, QUEIROZ et al 85 concluded that low temperatures, lack of luminosity and low levels of humidity are deleterious to the development of Toxocara canis eggs.…”