PCR amplification and sequencing of B. henselae SA2 DNA from two family members, woodlouse hunter spiders, and a woodlouse collected at least three years after family members were exposed to and the children were presumably bitten by similar spiders, was unexpected. To the best of our knowledge, this is the first report of the presence of Bartonella spp. DNA in spiders or in woodlice. Although B. henselae DNA was amplified from two spiders collected 13 months apart, a woodlouse, and from serum, blood and BAPGM enrichment culture samples from two family members, these results should be interpreted with caution, as it is not clear whether Bartonella was acquired at the time of the infestation and spider bites or whether the spiders and woodlice are accidental hosts for Bartonella spp. Since the woodlouse hunter spider is thought to feed exclusively on woodlice (a land-dwelling crustacean), the amplification of Bartonella DNA from spiders and woodlice suggests that the B. henselae-infected spiders fed on infected woodlice. Preliminary results (unpublished data) obtained in our laboratory indicates that washed woodlice can become PCR-positive for B. henselae after feeding on food contaminated with the bacteria. Although the length of time that B. henselae can remain viable within the environment has not been investigated to any degree, the bacteria remains viable in flea feces for several days. Whether bacteria ingested by woodlice remain viable, whether replication can occur, how long a Bartonella sp. can be retained within the isopod and whether a spider feeding on this crustacean can acquire or transmit Bartonella are subjects for future studies. Although the family experienced a flea infestation prior to moving into the new apartment, the family dog was not seroreactive to Bartonella sp. antigens and was PCR negative in blood and BAPGM enrichment blood culture, making the dog and potentially fleas a less likely source of B. henselae transmission to family members. To date, B. henselae has not been reported in bats to the author’s knowledge, no family member experienced a bat bite, and the bat exposure occurred several months before the onset of illness in the children and mother.
Bartonella DNA has also been amplified from non-hematophagous arthropods, such as honey bees . Those authors hypothesized that honey bees ingested or acquired Bartonella organisms through environmental contact. In a recent report, a patient with neuroretinitis, a well documented ocular pathology induced by B. henselae, was diagnosed with bartonellosis following the bite (sting) of a bull ant (genus Myrmecia) in Australia . These authors suggested that B. henselae was probably transmitted to the patient via the stinger or mandibles, which provided a portal for bacterial entry into the skin. These recent publications indicate that physicians should routinely review a patient’s medical history for arthropod exposure. Based upon recent clinical and research observations, there appears to be a growing spectrum of arthropods that might serve as vectors for Bartonella species, thereby emphasizing the critical importance of and the need for additional experimentally controlled vector competence studies. In addition, localizaton of Bartonella sp. replication within arthropods, further documentation of other potential animal reservoirs, and the determination of trans-ovarian transmission in various arthropod species represent other important issues that require scientific attention.
From a clinical perspective, the non-specific symptoms reported in the mother are consistent with previous reports of Bartonella sp. bacteremia in immunocompetent patients [4, 22]. Although less well characterized, the behavioral and neurocognitive abnormalities that predominated in the older son have also been reported in Bartonella bacteremic children [14, 23, 24]. Interestingly, and as reported in a small subset of patients in two case series, B. henselae DNA was only amplified from the mother's extracted serum samples, whereas B. henselae DNA was amplified from both blood and a BAPGM enrichment blood culture from the oldest son [4, 22]. The reason(s) for these observations remain unclear, but one study has reported progressive increases in serum DNA concentration in association with prolonged sample storage times in certain pathologic conditions . Bartonella DNA was never amplified from a negative control and DNA from a B. henselae H1 strain (not B. henselae SA2 as found in this study) was used as a positive control for all PCR testing, therefore laboratory contamination is an unlikely explanation for the PCR and DNA sequencing results reported in this study. Due to the fact that B. henselae induces a relapsing bacteremia in cats  and B. birtlesii induces a relapsing bacteremia in experimentally infected rodents , three blood samples obtained at approximately 2 day intervals were tested for each patient. For the mother and oldest son, only two dates yielded positive PCR results, potentially supporting the possibility of a relapsing pattern of B. henselae bacteremia in human patients. Also, as reported previously from our laboratory , there was considerable variability in the mother’s and youngest son’s antibody titers when serum samples obtained within a one-week time frame were tested using an IFA technique. The mother had low antibody titers with up to four-fold variations in four of the six Bartonella spp. antigens over a one week period. The youngest son had identical antibody titers to B. henselae strains H1 and SA2, but seemingly seroconverted to B. vinsonii subsp. berkhoffii genotypes I, II III and B. koehlerae. Administration of IVIG ten days prior to collection of the initial blood sample may well have influenced the youngest son’s serological results, particularly if IVIG has antibacterial properties . In contrast, the oldest son’s antibody titers were identical for all six antigens at all three time points. In the context of antigenic specificity, he had antibodies to B. henselae SA2 strain, but not to a B.henselae H1 strain. All serum sample sets from each patient were tested at the same time, by the same experienced technician, using the same conjugate and IFA antigen slides. Whether these serological discrepancies are related to sample collection and storage issues, a prozone effect associated with excess antigen, IVIG or other unknown factors requires additional investigation.
Similar to the initial diagnosis in the youngest son, GBS due to neurobartonellosis was diagnosed in a 10-year-old girl, who was hospitalized due to progressive leg weakness . Seven days earlier, the girl had a self-limiting episode of fever and vomiting of 1 day duration. Four days later, she had difficulty walking, became irritable and complained of severe myalgia in the lower limbs. Laboratory findings were not remarkable. Nerve conduction studies identified decreases in motor conduction velocity and amplitude, consistent with axonal damage. An exhaustive search for known causes of GBS was negative. The girl was treated with IVIG for 5 days, and within two weeks her neurological status had normalized. There was no history of cat scratches, no palpable lymphadenopathy and no hepatic or splenic lesions on an abdominal ultrasound, however, because she lived in a rural area and played with kittens, B. henselae serology was requested. Her B. henselae IgG titer was 1:1024 and a specific IgM titer was “positive”, although a value was not reported. Her convalescent IgM titer was negative and the IgG antibody titer had decreased. To date, CIDP has not been associated with Bartonella infection. Although serology supported Bartonella exposure in the younger son, prior administration of IVIG complicates interpretation of his antibody titers and potentially his BAPGM enrichment culture PCR test results. It is possible that the source of Bartonella antibodies was the IVIG and that repeated immunoglobulin administration suppressed the level of bacteraemia below the level of successful PCR amplification. CIPD, also referred to as relapsing polyneuropathy, is a neurological disorder characterized by progressive weakness and impaired sensory function in the legs and arms. As was true in the boy in this report, CIPD is often diagnosed as the chronic counterpart of GBS. Prior infection or vaccination can precipitate GBS, and Campylobacter jejuni has become the most well recognized antecedent infection . Consideration should be given to B. henselae as an antecedent infection for GBS and CIPD. Physicians should pursue the medical history in these patients to determine if they have experienced animal bites or scratches or arthropod bites or stings.
As scientists, physicians and veterinarians learn more about the medical importance of the genus Bartonella, there has been enhanced focus on known and suspected arthropod vectors. Because of their ability to reside within erythrocytes of a diverse number of mammalian hosts in conjunction with their diverse ecological niches, there is the potential opportunity for various Bartonella spp. to be transmitted by a variety of arthropod vectors. Several blood-feeding arthropods, Lutzomyia verrucarum, Pediculus humanus humanus, Ctenocephalides felis and some rodent fleas (Ctenophthalmus nobilis) have been confirmed to be competent vectors for transmission of Bartonella species . Tick transmission of Bartonella spp. has been a controversial subject in recent years [33, 34]; however, vector competence for tick (Ixodes ricinus) transmission of a Bartonella sp. was recently demonstrated experimentally, thus supporting the possibility that Ixodes sp. ticks are transmitting Bartonella spp. throughout the northern hemisphere . Previous studies from Europe and North America have documented the presence of B. henselae DNA in Ixodes ricinusIxodes scapularis and Ixodes pacificus. In conclusion, it must be stressed that there is an important difference between the vector competence and vector potential of arthropods from which Bartonella spp. DNA is amplified. The amplification of Bartonella spp. DNA in the woodlouse hunter spiders in this study does not provide definitive proof of vector competence and may merely represent an accidental infection associated with ingestion of Bartonella-infected blood from an infected host (isopod). Although B. henselae was amplified and sequenced from woodlouse hunter spiders and from their associated prey, the woodlouse, definitively establishing the source of bacterial transmission to this family was not possible.