Salmonella species by studying infections in laboratory animals, which will ultimately lead to improved prevention and treatment options for typhoid carriers. In 2002, Dr. John Gunn described the ability of Salmonella sp. to form biofilms on gallstones in mice, providing a model for studying carriage in the gallbladder. Dr. Denise Monack and Dr. Stanley Falkow described a mouse model of asymptomatic intestinal and systemic infection in 2004, and Dr. Monack went on to demonstrate that a sub-population of superspreaders are responsible for the majority of transmission to new hosts, following the 80/20 rule of disease transmission, and that the intestinal microbiota likely plays a role in transmission. Dr. Monack's mouse model allows long-term carriage of salmonella in mesenteric lymph nodes, spleen and liver. Vaccine development British bacteriologist Almroth Edward Wright first developed an effective typhoid vaccine at the Army Medical School in Netley, Hampshire. It was introduced in 1896 and used successfully by the British during the Second Boer War in South Africa. At that time, typhoid often killed more soldiers at war than were lost due to enemy combat. Wright further developed his vaccine at a newly opened research department at St Mary's Hospital Medical School in London from 1902, where he established a method for measuring protective substances (opsonin) in human blood. Wright's version of the typhoid vaccine was produced by growing the bacterium at body temperature in broth, then heating the bacteria to 60 °C to "heat inactivate" the pathogen, killing it, while keeping the surface antigens intact. The heat-killed bacteria was then injected into a patient. To show evidence of the vaccine's efficacy, Wright then collected serum samples from patients several weeks post-vaccination, and tested their serum's ability to agglutinate live typhoid bacteria. A "positive" result was represented by clumping of bacteria, indicating that the body was producing anti-serum (now called antibodies) against the pathogen. Citing the example of the Second Boer War, during which many soldiers died from easily preventable diseases, Wright convinced the British Army that 10 million vaccine doses should be produced for the troops being sent to the Western Front, thereby saving up to half a million lives during World War I. The British Army was the only combatant at the outbreak of the war to have its troops fully immunized against the bacterium. For the first time, their casualties due to combat exceeded those from disease. In 1909, Frederick F. Russell,