An alternative method for producing Toxocara canis second stage larvae from a paratenic host (pigeon) for mRNA extraction purpose

Toxocara canis is a prevalent zoonotic parasite which can cause serious disease in puppies and humans. Excretory–secretory and coating antigens of the second stage larvae (L2) are the best targets for performing immunodiagnostic and also immunoprophylactic tests. Various hatching methods have been described to bring out L2 from the resistant infective egg shell; but these methods are difficult to do and have had different results when performed by different practitioners. In this study, second stage larvae were obtained from the viscera of pigeons (a paratenic host) which were infected with infective eggs. Infective Toxocara canis eggs were given to ten pigeons and live larvae were recovered from their excised livers and lungs by using the Baermann’s apparatus in the next days. Two in vitro methods for larvae hatching were also performed including a so-called physiological hatching method according to Ponce-Macotela et al. (J Parasitol 175:382–385, 2010), and a mechanical hatching method according to Alcântara-Neves and Santos (J Exp Parasitol 119:349–351, 2008) and their results were compared with the in-vivo method. Results show that averagely 36.2 % of fed larvae recovered from livers and 0.15 % from lungs. Average larvae recovery in the first day after infection (24.2 %) was significantly lower than subsequent days (39 %). Maximum larvae recovered in day 3 (55 %). In-vitro methods we carried out did not have acceptable results and only a few larvae did hatch using these methods.