Human Bartonellosis: An Underappreciated Public Health Problem?
Bartonella spp. bacteria can be found around the globe and are the causative agents of multiple human diseases. The most well-known infection is called cat-scratch disease, which causes mild lymphadenopathy and fever. As our knowledge of these bacteria grows, new presentations of the disease have been recognized, with serious manifestations. Not only has more severe disease been associated with these bacteria but also Bartonella species have been discovered in a wide range of mammals, and the pathogens’ DNA can be found in multiple vectors. This review will focus on some common mammalian reservoirs as well as the suspected vectors in relation to the disease transmission and prevalence. Understanding the complex interactions between these bacteria, their vectors, and their reservoirs, as well as the breadth of infection by Bartonella around the world will help to assess the impact of Bartonellosis on public health. View Full-Text
Figure 1 The Clinical Manifestations of Bartonellosis
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Known diseases caused by Bartonella infections include:
- Carrion’s disease
- cat-scratch disease
- chronic lymphadenopathy
- trench fever
- chronic bacteraemia
- culture-negative endocarditis
- bacilliary angiomatosis
- bacilliary peliosis
- uveitis [1,2,4,6,7,9,10,11].
Recently, Bartonella infections have been linked to more diverse manifestations such as:
- weight loss
- muscle fatigue
- partial paralysis
- pediatric acute-onset neuropsychiatric syndrome (PANS)
- other neurological manifestations [6,8,10].
A few case studies have also documented Bartonella in tumors, particularly vasoproliferative and those of mammary tissue [12,13,14]. The potential involvement of this pathogen in breast tumorigenesis is both disconcerting and warrants significantly more research.
Bartonella spp. are zoonotic pathogens transmitted from mammals to humans through a variety of insect vectors including the sand fly, cat fleas, and human body louse [4,5]. New evidence suggests that ticks, red ants, and spiders can also transmit Bartonella [15,16,17,18]. Bed bugs have been implicated in the transmission cycle of B. quintana and have been artificially infected . B. quintana was found in bed bug feces for up to 18 days postinfection . The diversity of newly discovered Bartonella species, the large number and ecologically diverse animal reservoir hosts, and the large spectrum of arthropod vectors that can transmit these bacteria among animals and humans are major causes for public health concern.
3.2. Arachnids (Spiders and Ticks)
Ixodid ticks, also known as hard ticks, appear to be the main type of tick associated with these bacteria. Tick cell lines have been used to show that Bartonella can replicate and survive within:
- Amblyoma americanum (Lone Star Tick)
- Rhipicephalus sanguineus (Brown Dog Tick)
- Ixodes scapularis cells  (Deer Tick)
In California, questing ticks of
- Ixodes pacificus (Western Black legged Tick)
- Dermacentor occidentalis (Pacific Coast Tick)
- Dermacentor variabilis (American Dog Tick)
were collected when in the adult and nymphal stages and tested for Bartonella by PCR for the citrate synthase gene. . All types of ticks were found to contain Bartonella DNA, although in varying percentages and locations. These data alone do not prove that ticks can transmit Bartonella spp. Bacteria; however, the results do show Bartonella DNA occurring naturally in these wild ticks.
- Hyalomma spp. (Genus of hard-bodied tick) found in Asia, Europe, & North and South Africa.
- Haemphysalis spp. (The Asian Long-horned tick is an example)
- Rhipicephalusspp. (Hard-bodied tick native to tropical Africa)
ticks were collected from domestic animals and tested by PCR for the Bartonella intergenic transcribed spacer (ITS) region . These ticks were infected with 4 strains of Bartonella: B. rochalimae, B. chomelii, B. bovis, and B. koehlerae . While this study tested a collection of ticks found on domestic animals, the results suggest that individuals in close contact with these animals should be aware of the potential for transmission through tick bites.
Interestingly, the highest rate of both Borrelia spp. (63.2%) and B. henselae (10.3%) was found in Ixodes affinis ticks collected from North Carolina.
A recent One Health perspective review on Bartonella indicated that the overall presence of Bartonella in ticks (combining evidence from multiple surveillance studies) was approx. 15% .
Concerns such as these related to vector competence and transmission can only be quelled by repeated studies utilizing multiple strains of Bartonella and differing tick species.
I think we can safely state that Bartonella IS an under appreciated health problem.