Published Date: 2008-04-07 15:00:19
Subject: PRO/AH/EDR> Leptospirosis - Peru: (Loreto), new species
Archive Number: 20080407.1279
LEPTOSPIROSIS - PERU: (LORETO), NEW SPECIES
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Sun 6 Apr 2008
Source: Science Daily [edited]
While investigating the tropical disease leptospirosis in the
Peruvian Amazon, an infectious disease specialist from the University
of California, San Diego School of Medicine has uncovered new,
emerging bacteria that may be responsible for up to 40 percent of
cases of the disease. Patients with severe forms of leptospirosis
have jaundice, renal failure, and lung hemorrhage, with high fatality rates.
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 Lima, Peru, and others,
headed the study that led to discovery of the new species in the
family of pathogens, _Leptospira_, which is spread from animals to humans.
Leptospirosis is a severe, water-borne disease transmitted from
animals to humans, with tens of millions of human cases worldwide
each year. Fatality rates can range as high as 20 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 Iquitos. There,
Vinetz leads an international team of physicians from the USA and
Peru in an NIH (National Institutes of Health)-funded training
program studying malaria, leptospirosis, and other infectious
diseases that impact disadvantaged populations in developing countries.
The researchers found that the new species, _Leptospira licerasiae_,
cultured from a very small number of patients, as well as 8 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 _Leptospira_ in order to make the
correct diagnosis," Vinetz said.
[The formal citation for this work is
Matthias MA, Ricaldi JN, Cespedes M, et al (2008): Human
leptospirosis caused by a new, antigenically unique _Leptospira_
associated with a _Rattus_ species reservoir in the Peruvian Amazon.
PLoS Negl Trop Dis 2008; 2(4): e213. DOI: 10.1371/journal.pntd.0000213
The study did find that a substantial amount of infections with this
species occurred in the Iquitos area of the Peruvian Amazon, which is
in Loreto Region. Serostudies in other regions of Peru found only 2
other regions with significant numbers reacting with this serovar,
Ucayalo and Ayacucho-San Francisco.
A map of Peru can be found at
Whether this species is present in other areas is yet to be
determined. - Mod.LL]