the link is an intresting read , seems to me that if you treat/vacinate it itself is a waiste of time for the following reasons 1 the live vaccine is the best treatment , and if you treat them more birds may be infected with the disease , 2 if a live vaccine is used then the live infection is shed via the dropings making more birds exposed to paratyphoid , so using this vaccine when birds not ailing could set any loft further back by further exposing more birds to paratyhoid , so in my mind theres the answer people treating for this are doing more to make this disease stronger and there birds immune systems weaker by treating healthy birds , i have never had to treat for paratyphoid and hope never have to , regular screening of your birds and removing weak birds will limit the risks of most diseases in any loft , nature does this by natural sellection and only the strongest and the fitest survive in the wild , in a pigeon loft any sign of weakness then these birds should be removed and not continuously proped up with medication , birds that ail always fail