Neospora caninum is a cyst-forming parasite and its development involves two asexual stages-tachyzoite and bradyzoite
that occur in the intermediate host (e.
gondii is found in three morphologically different strains which are named as tachyzoite, bradyzoite
, and sporozoite.
Stage conversion between tachyzoite and bradyzoite
forms of Toxoplasma is associated with morphological and molecular biological changes, including stage-specific antigen expression and alterations to metabolism .
Scientists working in various fields, including microbiology, in Europe, the US, Japan, and Brazil contribute 26 chapters on its history and life cycle, the molecular epidemiology and population structure, human infection, ocular disease, toxoplasmosis in wild and domestic animals, animal models and therapeutics, biochemistry and metabolism, calcium storage and homeostasis, the role of secretory proteins, the parasite's structures, host immune responses, nucleotide and amino acid metabolism in comparison to other Apicomplexa, bradyzoite
development, chemical biology, cerebral toxoplasmosis, innate and adaptive immunity, and vaccination.
They travel in blood and reach different body parts and transformed into bradyzoite
cysts (5-10 um diameter) present in skeletal muscles and neural tissues.
In an effort to evade host defenses, tachyzoites switch to a slower growing bradyzoite
where they are able to lay dormant.
Toxoplasma gondii: determinants of tachyzoite to bradyzoite
The organism exits in nature in many forms: macro- and microgametes, the oocyte (which releases sporozoites), the tissue cyst, which contains and may release bradyzoite
, and tachyzoite.
Toxoplasma gondii: DNA vaccination with bradyzoite
antigens induces protective immunity in mice against oral infection with parasite cysts.
In an immuno competent individual the organism will encyst itself in the brain muscle and eye as a bradyzoite
Oocyst shedding by cats fed isolated bradyzoites
and comparison of infectivity of bradyzoites
of the VEG strain Toxoplasma gondii to cats and mice.
This may occur in the acute phase of infection or, alternatively, when there is recrudescence of encysted bradyzoites
, with possible appearance of clinical signs, such as in situations in which the immune system is affected (DUBEY, 2010).