Vector transmission of Bartonella species with emphasis on the potential for tick transmission

[Risk of infections among orienteers]

BACKGROUND

Research on orienteers is useful for assessing the risk of infections associated with physical activity in the forest. In this paper four types of infections are reviewed, and the efficacy of preventive initiatives is discussed.

MATERIAL AND METHODS

The paper is based on literature retrieved from a non-systemic search in PubMed.

RESULTS

Hepatitis B infection was more prevalent among orienteers before they were obliged to use protective clothing. In the 1980s, there was an increase of sudden unexpected death among young Swedish orienteers. Bartonella infection was later suggested as an underlying cause. No unexpected deaths have occurred among young orienteers after 1992 when specific advice was given regarding training and competitions. Orienteers do not seem to be affected by lyme borreliosis or tick-borne encephalitis (TBE) more often than others, but only two old studies have been performed.

INTERPRETATION

Orienteers may be at risk of acquiring infection from lyme borreliosis and TBE in Norway in the future, as the incidence of these contagions is increasing. Norwegian medical personnel should consider TBE vaccination of orienteers and others who wander in areas with a high prevalence of infected ticks.

Cross-contamination in the Molecular Detection of Bartonella from Paraffin-embedded Tissues

The genus Bartonella comprises a group of gram-negative, fastidious bacteria. Because of diagnostic limitations of culture and serologic testing, polymerase chain reaction (PCR) has become a powerful tool for the detection of Bartonella spp. in blood and tissue samples. However, because many wild and domestic animals harbor Bartonella spp., transfer of Bartonella DNA during sample collection or histologic processing could result in false-positive PCR test results. In this study, we describe evidence of Bartonella DNA dissemination and transfer in the necropsy room and during the subsequent processing of formalin-fixed paraffin-embedded tissues. Bartonella DNA was amplified from different areas of the necropsy room, from the liquid paraffin in the tissue processor, and from different parts of the microtome. Unless stringent procedures are established and followed to avoid cross-contamination, the molecular detection of Bartonella spp. from tissue samples obtained at necropsy or processed in a multispecies histopathology laboratory will not be reliable.

Prevalence of Bartonella infection in cats and dogs in a metropolitan area, Thailand

The prevalence of Bartonella infection was studied in 312 cats and 350 dogs in the Bangkok metropolitan areas, Thailand, between June 2001 and February 2003. Bartonella was isolated from 47 (16.3%) of 288 stray cats, but from none of the 24 pet cats studied. Of the 47 Bartonella-positive cats, 45 animals were infected with only B. henselae, one was infected with only B. clarridgeiae, and one with both B. henselae and B. clarridgeiae. 16S rRNA typing showed that 40 cats were infected with B. henselae type I, four with B. henselae type II, and one with both B. henselae types I and II. These results indicated that B. henselae, especially type I, was prevalent in stray cats that constituted a large Bartonella reservoir in Bangkok. B. clarridgeiae was isolated for the first time in Asia from one of 350 dogs.

Reviewing molecular adaptations of Lyme borreliosis spirochetes in the context of reproductive fitness in natural transmission cycles

Lyme borreliosis (LB) is caused by a group of pathogenic spirochetes – most often Borrelia burgdorferi, B. afzelii, and B. garinii – that are vectored by hard ticks in the Ixodes ricinus-persulcatus complex, which feed on a variety of mammals, birds, and lizards. Although LB is one of the best-studied vector-borne zoonoses, the annual incidence in North America and Europe leads other vector-borne diseases and continues to increase. What factors make the LB system so successful, and how can researchers hope to reduce disease risk – either through vaccinating humans or reducing the risk of contacting infected ticks in nature? Discoveries of molecular interactions involved in the transmission of LB spirochetes have accelerated recently, revealing complex interactions among the spirochete-tick-vertebrate triad. These interactions involve multiple, and often redundant, pathways that reflect the evolution of general and specific mechanisms by which the spirochetes survive and reproduce. Previous reviews have focused on the molecular interactions or population biology of the system. Here molecular interactions among the LB spirochete, its vector, and vertebrate hosts are reviewed in the context of natural maintenance cycles, which represent the ecological and evolutionary contexts that shape these interactions. This holistic system approach may help researchers develop additional testable hypotheses about transmission processes, interpret laboratory results, and guide development of future LB control measures and management.

A confusing case of canine vector-borne disease: clinical signs and progression in a dog co-infected with Ehrlichia canis and Bartonella vinsonii ssp. berkhoffii

Bartonella spp. are important pathogens in human and veterinary medicine, and bartonellosis is considered as an emerging zoonosis that is being reported with increasing frequency. Of 22 known species and subspecies of Bartonella, seven have been isolated from dogs, causing disease manifestations similar to those seen in human beings. The wide variety of clinical signs and the possible chronic progression of disease manifestations are illustrated in the case of an infected Labrador retriever. Here, the authors discuss the seemingly diverse spectrum of disease manifestations, the co-infections of Bartonella spp. with other vector-borne pathogens (mainly Ehrlichia spp. or Babesia spp.) and the difficulties in microbiological confirmation of an active Bartonella infection, all of which make the disease pathogenesis and clinical diagnosis more problematic.

Molecular documentation of Bartonella infection in dogs in Greece and Italy

This study reports the occurrence of "Bartonella rochalimae" in Europe and the presence of Bartonella vinsonii subsp. berkhoffii genotypes II and III in dogs in southern Italy and provides DNA sequencing evidence of a potentially new Bartonella sp. infecting dogs in Greece and Italy.

Ecological fitness and strategies of adaptation of Bartonella species to their hosts and vectors

Bartonella spp. are facultative intracellular bacteria that cause characteristic hostrestricted hemotropic infections in mammals and are typically transmitted by blood-sucking arthropods. In the mammalian reservoir, these bacteria initially infect a yet unrecognized primary niche, which seeds organisms into the blood stream leading to the establishment of a long-lasting intra-erythrocytic bacteremia as the hall-mark of infection. Bacterial type IV secretion systems, which are supra-molecular transporters ancestrally related to bacterial conjugation systems, represent crucial pathogenicity factors that have contributed to a radial expansion of the Bartonella lineage in nature by facilitating adaptation to unique mammalian hosts. On the molecular level, the type IV secretion system VirB/VirD4 is known to translocate a cocktail of different effector proteins into host cells, which subvert multiple cellular functions to the benefit of the infecting pathogen. Furthermore, bacterial adhesins mediate a critical, early step in the pathogenesis of the bartonellae by binding to extracellular matrix components of host cells, which leads to firm bacterial adhesion to the cell surface as a prerequisite for the efficient translocation of type IV secretion effector proteins. The best-studied adhesins in bartonellae are the orthologous trimeric autotransporter adhesins, BadA in Bartonella henselae and the Vomp family in Bartonella quintana. Genetic diversity and strain variability also appear to enhance the ability of bartonellae to invade not only specific reservoir hosts, but also accidental hosts, as shown for B. henselae. Bartonellae have been identified in many different blood-sucking arthropods, in which they are typically found to cause extracellular infections of the mid-gut epithelium. Adaptation to specific vectors and reservoirs seems to be a common strategy of bartonellae for transmission and host diversity. However, knowledge regarding arthropod specificity/restriction, the mode of transmission, and the bacterial factors involved in arthropod infection and transmission is still limited.

A longitudinal study of Bartonella infection in populations of woodrats and their fleas

Rodent-borne bartonellae have been identified as human pathogens. Little is known about Bartonella infections in woodrat hosts and their fleas and how woodrat-flea associations may affect the dynamics of Bartonella infections. We collected blood samples and fleas from two species of woodrats (Neotoma micropus and N. albigula) from Santa Fe County, NM, from 2002-2005. The most predominant flea species were Orchopeas sexdentatus and O. neotomae. Bartonella prevalence in woodrats was 64% overall, with a lower prevalence occurring in the pre-reproductive period compared to the early and late reproductive periods. A negative correlation between Bartonella prevalence in N. micropus and weight of N. micropus was observed. Flea load in Neotoma species was highest in the early reproductive period compared to the pre- and late reproductive periods and was higher in N. micropus compared to N. albigula. Bartonella prevalence in fleas was highest in the early reproductive period and lowest in the late reproductive period, and it was higher in fleas collected from N. micropus than in fleas collected from N. albigula. Abundance of O. sexdentatus was significantly higher in N. micropus compared to N. albigula, and abundance of O. sexdentatus and O. neotomae was highest in the early reproductive period. No direct correlations were found either between Bartonella prevalence in woodrats and in fleas or between Bartonella prevalence in woodrats and flea loads. Out of 25 partially characterized Bartonella isolates from Neotoma woodrats, 24 belonged to one genogroup based on sequencing of the gltA gene.

Bartonella sp. bacteremia in patients with neurological and neurocognitive dysfunction

We detected infection with a Bartonella species (B. henselae or B. vinsonii subsp. berkhoffii) in blood samples from six immunocompetent patients who presented with a chronic neurological or neurocognitive syndrome including seizures, ataxia, memory loss, and/or tremors. Each of these patients had substantial animal contact or recent arthropod exposure as a potential risk factor for Bartonella infection. Additional studies should be performed to clarify the potential role of Bartonella spp. as a cause of chronic neurological and neurocognitive dysfunction.