While investigating the tropical disease leptospirosis in the Peruvian Amazon, an infectious disease specialist from the
Joseph Vinetz, MD, professor of medicine in UC San Diego’s Division of Infectious Diseases – working in collaboration with colleagues from Universidad Peruana Cayetano Heredia in
Leptospirosis is a severe, waterborne disease transmitted from animals to humans, with tens of millions of human cases worldwide each year. Fatality rates can range as high as 20 percent to 25 percent in some regions, and it is particularly prevalent in tropical countries where poor people live under highly crowded condition, or in rural areas where people are exposed to water contaminated by the urine of Leptospira-infected animals such as rats.
The new species reflects Amazonian biodiversity, according to Vinetz, and the pathogen has apparently evolved to become an important cause of leptospirosis in the Peruvian Amazon region of
The researchers found that the new species, Leptospira licerasiae – cultured from a very small number of patients, as well as eight rats – is significantly different from other forms of the bacteria at a genomic level and has novel biological features.
“This strain has fundamentally different characteristics,” said Vinetz, adding that the next step is to sequence its genome. “We think that hundreds of patients are infected with this pathogen, which is so unique that antibodies for the disease don’t react to the regular tests for leptospirosis.”
In testing 881 patients in a prospective clinical study of fever, the researchers found that 41 percent of them had antibodies that reacted only to this new strain of the bacteria, showing a much higher incidence of leptospirosis than previously suspected.
“This observation is relevant to other regions of the world where leptospirosis is likely to be common, because it’s necessary to identify the right strain of the Lepstospira in order to make the correct diagnosis,” Vinetz said.
Since isolation of the new Leptospira in people was rare despite the high prevalence of antibodies to this strain of the bacteria in the Amazonian population, Vinetz theorizes that the individuals with positive cultures may have a previously undiscovered immune system defect, making them more susceptible to the disease.
Additional contributors to the paper include Michael A. Matthias, Jessica N. Ricaldi, Kailash Patra, and Mayuko Saito of UCSD, Manuel Cespedes of the National Institute of Health in
Source: University of