Differences in larval survival and IgG response patterns in long-lasting infections by Trichinella spiralis , Trichinell
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Parasites & Vectors Open Access
RESEARCH
Differences in larval survival and IgG response patterns in long‑lasting infections by Trichinella spiralis, Trichinella britovi and Trichinella pseudospiralis in pigs Edoardo Pozio1, Giuseppe Merialdi2, Elio Licata3, Giacinto Della Casa4, Massimo Fabiani1, Marco Amati1, Simona Cherchi1, Mattia Ramini2, Valerio Faeti4, Maria Interisano1, Alessandra Ludovisi1, Gianluca Rugna2, Gianluca Marucci1, Daniele Tonanzi1 and Maria Angeles Gómez‑Morales1*
Abstract Background: Domesticated and wild swine play an important role as reservoir hosts of Trichinella spp. and a source of infection for humans. Little is known about the survival of Trichinella larvae in muscles and the duration of antiTrichinella antibodies in pigs with long-lasting infections. Methods: Sixty pigs were divided into three groups of 20 animals and infected with 10,000 larvae of Trichinella spiralis, Trichinella britovi or Trichinella pseudospiralis. Four pigs from each group were sacrificed at 2, 6, 12, 18 and 24 months post-infection (p.i.) and the number of larvae per gram (LPG) of muscles was calculated. Serum samples were tested by ELISA and western blot using excretory/secretory (ES) and crude antigens. Results: Trichinella spiralis showed the highest infectivity and immunogenicity in pigs and larvae survived in pig mus‑ cles for up to 2 years p.i. In these pigs, the IgG level significantly increased at 30 days p.i. and reached a peak at about 60 days p.i., remaining stable until the end of the experiment. In T. britovi-infected pigs, LPG was about 70 times lower than for T. spiralis at 2 months p.i. and only very few infecting larvae were detected at 6 months p.i., whereas no larvae were detected at 12, 18 and 24 months p.i. At 6 months p.i., degenerated/calcified larvae and cysts were detected in the muscles by trichinoscopy and histology. The IgG pattern showed by T. britovi-infected pigs was similar to that of T. spiralis-infected pigs, although seroconversion occurred some days later. The larval burden of T. pseudospiralis was slightly greater than for T. britovi at 2 months p.i., but no larvae were detected at 6 and 12 months p.i. In T. pseudospiralis-infected pigs, seroconversion occurred slowly, as in T. britovi-infected pigs. The IgG level showed a significant drop at 6 months p.i. and declining to the cut-off value at 12 months p.i. Conclusions: The longer survival of T. spiralis in pigs in comparison with the other two species highlights its excep‑ tional dissemination potential. These results provide an explanation of the controversial data collected by parasitologi‑ cal and serological tools in the course of epidemiological investigations. Keywords: Trichinella spiralis, Trichinella britovi, Trichinella pseudospiralis, Pig, Larval burden, Immune response, ELISA, Western blot, Epidemiology
*Correspondence: [email protected] 1 Department of Infectious Diseases, Istituto Superiore di Sanità, viale Regina Elena 299, 00161 Rome, Italy Full list of author information is available
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