Toxoplasma gondii: Sheep and Goats Have a Vaccine Against It. Why Don't We?
It''s becoming apparent that Toxoplasma gondii is responsible for an awful lot of human suffering around the world. The parasitic organism causes birth defects and spontaneous abortions, neurolgical impairment, eye damage and is increasingly suspected in Alzheimer's, schizophrenia and Parkinson's.
T. gondii infects human cells and reproduces within them eventually setting up shop in cysts throughout the central nervous system, heart, muscle, bone marrow and other organs. Persons infected are infected for life. Human infection is most commonly the result of consuming un-/under-cooked cyst-bearing meat though contact with the feces of animals, especially cats, T. gondii's ultimate host, are another avenue of exposure.
While 11% of Americans are infected with the parasite, that figure rises to as high as 70% in some South American countries. The European Food Safety Authority, worried that foodborne infection by T. gondii is on the rise and is responsible for significant yet underreported and undetected diseases within the EU, has recommended Toxoplasma monitoring of lifestock. Recent estimates of the impact of T. gondii-induced disease reveal it to be "one of the most significant causes of foodborne disease worldwide."
The good news is that thanks to demand from sheep and goat producers there's a vaccine that works well in sheep and goats. The problem is that it's a live cell preparation like the Sabin vaccine discussed during oral argument in Bruesewitz, et al v. Wyeth, Inc.,. So what's the problem? The problem is that while it works really well, much better than bits of a dead organism, it's more likely to cause adverse effects. Meanwhile, finding all the bits of a dead organism that prime the immune system while weeding out those that might produce harm is a terribly complicated and expensive process. Add to that the threat posed by litigation over the inevitable errors in science's slow but steady progress through trial and error and it ought not be surprising that sheep and goats get protected while human suffering due to T. gondii spreads.
For a new, free and enlightening paper on the topic see "Vaccination Against Toxoplasma gondii: An Increasing Priority for Collaborative Research?"
