Rats spreading new plague

Research suggests that brown rats may be carrying a type of bacteria that can cause serious illnesses in humans.

Professor Chao-Chin Chang and colleagues have discovered that brown rats are carrying several species of Bartonella bacteria. The discovery is concerning as the bacteria are classed as emerging zoonotic pathogens, and can cause serious illnesses including endocarditis (inflammation of the heart), enlargement of the spleen, and neuroretinitis (inflammation of the retina and optic nerve). More than 20 species of Bartonella bacteria have been discovered since the early 1990's, and at least eight are known to be pathogenic to humans.

The researchers took samples from 58 rodents, including 53 brown rats, 2 mice, and 3 black rats. Results showed that 6 (10.3%) of the rodents were carrying Bartonella bacteria, and five out of six of the carriers were brown rats. Four of the rodents were carrying B. elizabethae, which can cause endocarditis in humans. The researchers also identified a species of Bartonella that had not previously been identified in rodents. Further tests showed that the species was closely related to B. rochalimae, which is pathogenic to humans. Exactly how the bacteria are being spread to humans in uncertain, however the researchers are confident that, just like the plague, infections are spread by fleas.
 
Professor Chang concluded: “Several different Bartonella bacteria are surely transmitted by rodents. These results raise concerns about the existence of other reservoirs and vectors for this emerging infection. This certainly warrants further investigation."

Lin JW, Chen CY, Chen WC, Chome BB, Chang CC. Isolation of Bartonella species from rodents in Taiwan including a strain closely related to ‘Bartonella rochalimae' from Rattus norvegicus. J Med Microbiol. 2008;57:1496-150. DOI: 10.1099/jmm.0.2008/004671-0

News release: Scientists discover 21st century plague. Society for General Microbiology. November 24th 2008.