Identification of Bartonella infections in febrile human patients from Thailand and their potential animal reservoirs

Abstract

To determine the role of Bartonella species as causes of acute febrile illness in humans from Thailand, we used a novel strategy of co-cultivation of blood with eukaryotic cells and subsequent phylogenetic analysis of Bartonella-specific DNA products. Bartonella species were identified in 14 blood clots from febrile patients. Sequence analysis showed that more than one-half of the genotypes identified in human patients were similar or identical to homologous sequences identified in rodents from Asia and were closely related to B. elizabethae, B. rattimassiliensis, and B. tribocorum. The remaining genotypes belonged to B. henselae, B. vinsonii, and B. tamiae. Among the positive febrile patients, animal exposure was common: 36% reported owning either dogs or cats and 71% reported rat exposure during the 2 weeks before illness onset. The findings suggest that rodents are likely reservoirs for a substantial portion of cases of human Bartonella infections in Thailand.

Figure 1.

Phylogenetic relationships between the gltA sequences of Bartonella genotypes detected in 16 human patients from Thailand, previously described Bartonella species, and selected genotypes detected in mammals in Asia. The phylogenetic tree was constructed by the N–J method and bootstrap values with 1,000 replicates. Only bootstrap replicates > 70% are noted. The name and accession number of genotypes detected in human patients are outlined in the text box. Each unique Bartonella species or genotype detected in mammals is provided with the name of the type strain and its GenBank accession number.