In veterinary parasitology there are serological tests for a variety of helminth, arthropod and protozoan parasites. The tests depend on the detection in the blood of either parasite antigen or of antibodies produced by the host to parasite antigen. In Canada, serological testing of animals for parasites is probably most commonly used for Toxoplasma (in a variety of hosts), for Neospora (especially in cattle), for Trichinella screening (in pigs), and for feline heartworm (Dirofilaria immitis), for which a variety of commercial kits are available. In addition, serological tests for a variety of other parasites are available as research tools.