DISCOVERY OF BARTONELLA INFECTIONS IN ANIMALS FROM VIETNAM

Hoang Kim Loan ⁽¹⁾, Cao Bao Van ⁽¹⁾, Nguyen Thai Hiep ⁽¹⁾, Nguyen Thi Kim Tien ⁽¹⁾, and Michael Kosoy ⁽²⁾

(1) Pasteur Institute of Ho Chi Minh City, Vietnam; (2) Bacterial Zoonoses Branch, Division of Vector- borne Infectious Disease, Centers for Disease Control and Prevention, Ft.Collins, CO, USA.

Bacteria of the genus Bartonella cause a number of different illnesses, most of which are thought to be zoonoses. Some species of Bartonella were recognized as human pathogens early in the 20^th century. Diseases caused by these microorganisms involve a broad spectrum of signs and symptoms, including chronic bacteremia, fever, skin lesions, endocarditis, and other manifestations of the central nervures system, liver, eye, and bone tissue. Until very recently no information existed about distribution of Bartonella organisms or their role in human pathology in Vietnam. Our objectives were to detect Bartonella bacteria in Vietnamese rodents and to characterize a genetic diversity of the Bartonella community.

From November2002 to May 2003, rats were trapped in Dongnai and Binhphuoc provinces. Blood samples from captured rats were collected in the field and kept in liquid nitrogen until they were delivered to the Centers for Disease Control and Prevention in Fort Collins, Colorado, USA. Whole blood from 100 small mammals [m1] that belongs to 3 species (Rattus norvergicus, R. exulans, and Suncus murinus) was plated on agar supplemented with rabbit blood for Bartonella culturing. Isolates were obtained from 8 animals. Bacteria cultures, were preliminary identified by bacterial morphology and later confirmed by PCR amplification of Bartonella – specific sequence of the citrate synthase gene (gltA). All Bartonella isolates obtained from Vietnamese mammals were placed on a single branch of Bartonella phylogenetic tree along with Bartonella elizabethae (Gene Bank accession No. U28072) that was a source for human endocarditis case in Massachusetts, USA. The most important result is the identity of six isolates found in Vietnam (5 from Rattus rats and 1 from with the human pathogen, B. elizabethae). One isolate obtained from Vietnamese rat was identical to Bartonella strains cultured from R. norvegicus collected in Louisiana, USA that suggests the possibility for exchange of Bartonella strains between continents by domestic rats. Bartonella strains obtained from Vietnamese rodents were used to make reagents for serological testing of human samples.

These results represent the first isolation of Bartonella species from Vietnam, and they provide an important link to on going work designed to characterize human bartonellosis in Vietnam and define ecologic associations of the different Bartonella strains with mammalian hosts. The finding of B. elizabethae in rats suggests the need to investigate whether this bacterium might be responsible for cases of endocarditis in Vietnam.