Toxocara canis is a nematode with a biological cycle that includes a
definitive canine host and diverse paratenic hosts. These hosts include humans, rats,
rabbits, birds, and pigs. This parasite is the causal agent for toxocariosis, which is an
important parasitic infection in tropical and subtropical regions. Infection of BALB/c
mice with T. canis elicited a Th2 response; however, this infection did not significantly
alter the Th1 immune response. An appropriate animal model must primarily imitate the
human host, the parasite’s responses to the human host or the way that both the host and
parasite interact. The knowledge of the immunological response in toxocariosis is
relevant for understanding the protective mechanisms developed by the host against the
parasite and the immune modulation effect on these mechanisms by the larvae. These
parasite-host interactions could culminate in the success of the infection, the
development of the disease, the destruction of the parasite or the interruption of its
pathogenic mechanisms. This knowledge allows to design the methods of
immunodiagnosis based on the detection of specific antibodies against parasite antigens
and/or the detection of the parasites’ antigens. Finally, the identification of the
protective immune response mechanisms could serve in the development of strategies
for the prevention, treatment and more adequate management of patients. In this
chapter, we review certain aspects of the immunological responses that participate in
the infection and in the disease, the relevant aspects of the humoral immunological
response for the design of immunodiagnostic methods and for the development of
vaccines.
Keywords: Toxocariosis, Toxocara canis, helminth, nematode, worm, immunity,
immune response, immunoparasitology, Th1, Th2, cytokines, drug design,
immunodiagnosis, epidemiology.