Bartonella henselae and the Potential for Arthropod Vector-Borne Transmission

Abstract

Introduction:

Bartonella henselae, the causative agent of the illness referred to as cat scratch disease, is a common infection, particularly in children, and clinicians need to be aware of its potential transmission to humans by arthropod vectors such as fleas and ticks in addition to animal bites and scratches. The absence of a vertebrate bite or scratch does not preclude infection with B. henselae.

Materials and Methods:

Literature regarding arthropod transmission of B. henselae was reviewed.

Results:

B. henselae appears to be transmitted among cats and dogs in vivo exclusively by arthropod vectors (excepting perinatal transmission), not by biting and scratching. In the absence of these vectors disease does not spread. On the other hand, disease can be spread to humans by bites and scratches, and it is highly likely that it is spread as well by arthropod vectors.

Discussion:

Clinicians should be aware that a common illness, infection with B. henselae, can be transmitted by arthropod vectors and a history of an animal scratch or bite is not necessary for disease transmission.

M any zoonotic infectious diseases worldwide are poorly understood with respect to host reservoirs and interspecies transmission. Bartonella henselae is a bacterium identified as the cause of human cat scratch disease only within the past 20 years and the acquisition of the disease by humans is not yet completely understood (Regnery and Tappero 1995, Sanogo et al. 2003, Gouriet et al. 2007, Billeter et al. 2008, Cotté et al. 2008). The Bartonella species as a whole are emerging as more common pathogens than previously suspected, with studies revealing a worldwide distribution of seroreactivity to Bartonella in both humans and various animal species (Noah et al. 1997, Skerget et al. 2003, Chomel et al. 2006, Chmielewski et al. 2007, Zhang et al. 2008). Traditionally regarded as transmitted by direct contact between animals and humans, increasing evidence suggests that Bartonella species are directly transmitted by arthropod vectors both within host reservoirs and between human and animal species (Chang et al. 2001, Guptill 2003, Sanogo et al. 2003, Bown et al. 2004, Podsiadly et al. 2007, Cotté et al. 2008, Matsumoto et al. 2008). Evidence supporting significant human Bartonella exposure as well as the potential for vector-borne disease transmission suggests that physicians should consider more frequent screening for Bartonella as well as other arthropod-borne disease.

Bartonella species are gram-negative, facultative intracellular bacteria associated with disease in human and animal species, including both domestic animals (cats, dogs, and cattle) and wildlife species (coyotes, foxes, rodents, and various deer species) (Chang et al. 2001, Sanogo et al. 2003, Skerget et al. 2003, Bown et al. 2004, Reeves et al. 2006, Abbot et al. 2007, Li et al. 2007, Billeter et al. 2008, Breitschwerdt 2008). The known human pathogenic species or subspecies of Bartonella include B. henselae (cat scratch disease), Bartonella quintana (Trench Fever), Bartonella bacilliformis (Carrion Disease/Bacillary Angiomatosis), Bartonella clarridgeae, Bartonella koehlerae, Bartonella vinsonii subsp. berkhoffi, B. vinsonii subsp. arupensis, Bartonella tamiae, Bartonella rochalimae, Bartonella washoensis, Bartonella alsatica, Bartonella schoenbuchensis, Bartonella grahamii, and Bartonella elizabethae (Regnery and Tappero 1995, Kordick and Breitschwerdt 1998, Chomel et al. 2006, Breitschwerdt et al. 2007a, Inoue et al. 2008, Kosoy et al. 2008). Additional Bartonella species have been isolated from human blood (Bartonella melophagi) with unknown clinical relevance (Maggi et al. 2009).

In humans, cat scratch disease was first described in 1931, but the causal agent was not definitively identified as B. henselae until 1992 (Regnery and Tappero 1995, Chomel et al. 2006). Infection with the bacterium typically causes a variety of disease manifestations (see Table 1), including fever, lymphadenopathy, malaise, and splenomegaly, that can persist for several months. Less commonly, more serious complications occur, including angiomatosis, ocular involvement, encephalitis, meningitis, myelitis, glomerulonephritis, and endocarditis (Janier 1999, Dehio 2005, Chomel et al. 2006, Gouriet et al. 2007, Cherinet and Tomlinson 2008). In addition to neurologic presentations, psychiatric disorders such as agitation, acute panic disorder, and depression have been attributed to Bartonella (Schaller et al. 2007). Atypical presentations can occur in up to 25% of cases (Windsor 2001).

Table 1.

Clinical Signs Associated with Bartonellosis in Humans

Fever

Lymphadenopathy

Malaise

Splenomegaly

Angiomatosis

Polyarthritis

Hepatic granulomas

Splenic granulomas

Ocular disease/uveitis

Encephalitis

Neuropathies

Meningitis

Myelitis

Anemia

Guillain-Barre

Glomerulonephritis

Endocarditis/myocarditis

Erythema multiforme

Erythema nodosum

Psychiatric disorders

Despite the original difficulties in identifying B. henselae as the agent responsible for cat scratch disease, newer immunologic diagnostic techniques now enable clinicians to rapidly identify Bartonella species. Diagnosis typically requires the use of polymerase chain reaction (PCR) and/or serologic antibody testing, since bacteremia is not commonly detected in immunocompetent persons and conventional blood cultures often do not yield positive results. However, bacteremia and septicemia may in fact be present in some patients, and can be identified using more recently introduced enrichment blood cultures (Breitschwerdt et al. 2010a). The presence of bacteremia may be more common in immunocompromised patients such as those with AIDS, but can occur in any individual (Chomel et al. 2006, Breitschwerdt et al. 2010). Genetic variation between strains of B. henselae does exist and detection can prove to be elusive (Windsor 2001). Unless specifically screened for, B. henselae may remain undetected in patients and it is likely that disease resulting from infection with the bacterium will be under diagnosed. Screening of human blood donors has yielded a seroprevalence to B. henselae of 3%, and further studies have found a 3%–6% seroprevalence in healthy control populations (Skerget et al. 2003, Gouriet et al. 2007). Given this relatively high percentage of seroreactivity, it is therefore likely that many persons with primary B. henselae infection remain asymptomatic or the infection remains undetected (Gouriet et al. 2007, Breitschwerdt et al. 2010, Kosoy et al. 2010).

Recent studies, however, provide evidence that in certain human populations the prevalence of exposure to B. henselae may be significantly higher than 3%, particularly in those with direct animal contact. In Poland, antibodies to B. henselae were detected in 45% of veterinarians and 53.3% of cat owners in a 2007 study (Chmielewski et al. 2007). A Japanese study found that 15% of veterinarians in that country had seroreactivity to B. henselae, whereas a survey of U.S. veterinarians found a 7% seroprevalence to either B. henselae or B. quintana (Noah et al. 1997, Kumasaka et al. 2001). In North Carolina, a 2007 study of 14 immunocompetent persons who had >10 years of reported occupational animal exposure revealed that 57% of participants had seroreactivity to one of three Bartonella antigens (B. henselae, B. quintana, and B. vinsonii subsp. berkhoffi) and that B. henselae or B. vinsonii subsp. berkhoffi could be directly isolated or detected in all study participants (Breitschwerdt et al. 2007a). A 2008 study of farm workers in the People's Republic of China found a 9.6% seroprevalence to B. henselae (Zhang et al. 2008). The above studies would indicate that direct regular contact with animal species in an occupational or recreational setting is associated with a significantly higher likelihood to develop antibodies toward B. henselae after exposure to the microorganism, but a 2003 Austrian study did not find a statistically significant correlation between domestic pet ownership and seroprevalence with respect to B. henselae. In a study of 376 individuals, 23% of participants were seropositive for B. henselae, but there was not a difference between those with and those without domestic pets (Skerget et al. 2003). Thus, the above studies provide conflicting data regarding the development of antibodies toward B. henselae in humans with direct animal contact, nor do these studies identify the routes of exposure in those individuals seropositive for B. henselae. The presence of seroreactivity does not necessarily indicate active infection; however, and clinicians may wish to consider more specific testing through the use of PCR or enriched blood cultures to identity bacteremia. Detection of bacteria directly from culture would provide an unambiguous diagnosis and eliminate any potential issues regarding interpretation of serology results from different laboratories.

In domestic cats, the known reservoir of B. henselae, the vast majority of carriers do not develop clinical disease despite bacteremia, although fatal illness can occur infrequently (Abbott et al. 1997, Chomel et al. 2003). Feline intraspecies transmission is regarded as vector-borne and several studies have failed to demonstrate either seroconversion or bacteremia in uninfected cats living in prolonged association with infected cats but in an ectoparasite-free environment (Chomel et al. 1996, Kordick and Breitschwerdt 1998, Guptill 2003, Bradbury and Lappin 2010). Direct transmission between cats experimentally has also failed (Chang et al. 1999). In cats, the presence of arthropod vectors appears to be necessary for horizontal disease transmission (Abbott et al. 1997, Guptill 2003). Transmission in cats has typically been associated with the cat flea (Ctenocephalides felis) via fleas acquiring B. henselae during a blood meal from an infected carrier and then later regurgitating infected saliva while feeding on an uninfected individual (Guptill 2003). Cats can also be infected with other species of Bartonella, including B. quintana, B. koehlerae, B. clarridgeae, B. vinsonni subsp. berkhoffi, and Bartonella bovis, of which all with the exception of B. bovis are known human pathogens and have been detected in cat fleas by PCR (Rolain et al. 2003, Varanat et al. 2009). Infection of cats with nonreservoir-adapted Bartonella species may be associated with increased morbidity (Varanat et al. 2009). It is estimated that up to 40% of healthy cats are infected with at least one Bartonella species, with some areas of the United States reporting up to 90% prevalence (CDC 2010, Jameson et al. 1995). In both the United States and Europe, a higher seroprevalence occurs in warm, moist climates compared with colder, drier climates and is assumed to correlate with the ectoparasite prevalence in these regions (Jameson et al. 1995, Skerget et al. 2003, Solano-Gallego et al. 2006). Attempts to eliminate the carrier state within individual cats have been unsuccessful, as antimicrobial therapy has not been proven to eliminate the infection in seropositive individuals. Reduction of the prevalence of infection will depend on reducing or eliminating ectoparasites known or suspected to be involved in transmission between cats.

Domestic dogs are frequently reported to be accidental hosts for B. henselae, yet surveys in the United States have found seroreactivity rates of 10.1% in apparently healthy dogs and 27.2% in sick dogs (Solano-Gallego et al. 2004). As in cats, higher seroprevalence rates are noted in warmer climates. Transmission to humans is known to occur directly via dog bites, and oral swabs of dogs have confirmed at least four Bartonella species (B. henselae, B. quintana, B. vinsonii subsp. berkhoffi, and B. bovis), of which all but B. bovis are zoonotic (Skerget et al. 2003, Chomel et al. 2006, Duncan et al. 2007). Dogs may in fact be a reservoir for B. vinsonii subsp. berkhoffii, with seroprevalence rates worldwide ranging from <5% in the United States and Europe to 65% in parts of sub-Saharan Africa (Chomel et al. 2006). Despite the low rates in the United States in domestic dogs, several retrospective studies in California reported a 76% seroprevalence to B. vinsonii subsp. berkhoffi in coyotes (Canis latrans) and at least one human case has been reported in association with a coyote bite (Chang et al. 1999, 2000). As in cats, intraspecies transmission in dogs is believed to rely on arthropod vectors (Chang et al. 1999, Guptill 2003). Dogs with seroreactivity to B. vinsonii subsp. berkhoffi have been reported to be significantly more likely to have heavy flea and/or tick exposure (Pappalardo et al. 1997, Chang et al. 1999).

Humans have been assumed to acquire B. henselae infection when flea fecal material is introduced through the skin via a cat scratch or cat or dog bite (Skerget et al. 2003) and screening for the disease in clinically ill patients has centered on those with a known history of direct animal contact via occupational exposure or through pet ownership. Given this assumption, it would be expected that a higher disease prevalence would exist in households with pet ownership or in rural populations with more frequent contact with nonhuman animal species (Comer et al. 2001). The 2003 Austrian study discussed above did not find data to support any differences in seroreactivity to Bartonella with respect to urban versus rural populations nor with respect to pet ownership or lack thereof. The overall seroprevalence to B. henselae was 20% in humans who did not own pets for at least 1 year, suggesting either previous animal exposure with continued antibodies to B. henselae long after exposure, or an alternate route of transmission (Skerget et al. 2003). Recent evidence suggests that iatrogenic transmission to humans via accidental needle stick may occur, as well as perinatal transmission (Breitschwerdt et al. 2010b, Oliveira et al. 2010). Chronic B. henselae infection lasting years in humans has been reported, and may account for some cases in which no known recent animal exposure has occurred (Stockmeyer et al. 2007).

Despite the known flea vector-borne status of B. henselae in cats, it has long been suspected that other arthropod vectors are involved in transmission of B. henselae both with respect to intraspecies transmission in animal species as well as with respect to interspecies transmission, specifically human disease acquisition from animals (Chang et al. 1999, Guptill 2003, Rolain et al. 2003, Morozova et al. 2005, Chomel et al. 2006, Breitschwerdt et al. 2008, Cotté et al. 2008). Bartonella species are Proteobacteria in the family Bartonellacae. Other Proteobacteria, the Rickettsiaceae, includes the genera Ehrlichia, Coxiella, Anaplasma, and Rickettsia. These other rickettsial diseases are known to be transmitted by arthropods and several species are associated with zoonoses (Rolain et al. 2003, Dehio 2004, Brouqui et al. 2005, Billeter et al. 2008, Chomel et al. 2009, Otranto et al. 2009).

Likely due to their arthropod vectors, the Bartonella and rickettsial diseases have commonly affected individuals from rural environments. However, certain species (Ehrlichia chaffeensis, Anaplasma phagocytophilia, Rickettsia felis, and B. elizabethae) have been able to make the transition to survival in urban environments due to the adaptation of their sylvan hosts and their respective ectoparasites to urban areas (Comer et al. 2001, Brouqui and Raoult 2006). Human body louse (Pediculus humanus corpus) vector-borne diseases traditionally found in equatorial regions at higher elevations are becoming increasingly common in urban areas with louse infestations, specifically among populations of the homeless and those from lower income inner city areas. Three louse-borne diseases are recognized, and include Trench Fever (B. quintana), Typhus (R. prowazekii), and a relapsing fever resulting from infection with Borrelia recurrentis (Regnery and Tappero 1995, Brouqui and Raoult 2006, Billeter et al. 2008). At least one of these (B. quintana) has been detected in the dental pulp of domestic cats and a 2005 report described two human patients from France that had clinical disease associated with B. quintana but no evidence of body lice infestation (La et al. 2005). Neither patient had poor hygiene, but both did have direct contact with cats. A previous 1997 report from the United States identified two human cases of B. quintana infection in which no previous louse exposure was known, and a case report exists from a woman in whom B. quintana was detected after bite wounds from two feral cats that also were blood culture positive for the bacteria (Breitschwerdt et al. 2007b).

Although insufficient research has been done to definitively prove human infection with B. henselae via arthropod vectors, several randomized studies have identified various Bartonella species in various species of blood-sucking arthropods that also can feed on humans as atypical hosts (Rolain et al. 2003, Schabereiter-Gurtner et al. 2003, Brouqui and Raoult 2006). A 2003 study identified B. henselae in 11.1% of cat fleas collected throughout France as well as B. clarridgeiae (67.9%), B. quintana (17.3%), and B. koehlerae (3.7%), all of which are zoonotic (Rolain et al. 2003). A later 2004 study identified B. henselae in a biting stable fly (Stomoxys sp.) from a dairy barn in California (Chung et al. 2004), and a Polish study in 2007 identified B. henselae in 4.9% of sheep ticks (Ixodes ricinus) removed from dogs (Podsiadly et al. 2007). In the latter study (involving the most common hard tick species in Western Europe), for the first time, B. henselae had been isolated in ticks still attached to their canine hosts, but the probability of tick-borne transmission of Bartonella in Canis species had been long suspected. The 1999 California study identifying B. vinsonii subsp. berkhoffi in sylvan coyote populations had noted that the distribution of Bartonella was not apparently random but instead aligned well with the geographic distribution of two tick species (Ixodes pacificus and Dermacentor variablis) that feed on both coyotes and domestic dogs (Chang et al. 1999). A later 2001 study also in California identified Bartonella in 19.2% of I. pacificus ticks randomly collected via flagging vegetation, with various Bartonella strains, including B. henselae, B. quintana, and B. vinsonii subsp. berkhoffi detected, all of which are pathogenic to humans (Chang et al. 2001).

The presence of positive seroreactivity to B. henselae and/or positive identification of the bacteria has been demonstrated in numerous other mammalian species, including cattle, horses, Florida panthers, Beluga, and porpoises (Table 2) (Rotstein et al. 2000, Maggi et al. 2005, 2008, Cherry et al. 2009, Jones et al. 2008). It is not established what, if any, clinical disease may be induced by infection with B. henselae in these species nor is the route of exposure known, but the detection of B. henselae in cattle and horses as well as in biting stable flies may suggest arthropod transmission. Other Bartonella species pathogenic to humans have been definitively established as vector-borne. Trench Fever/Bacillary Angiomatosis (B. quintana) is transmitted by the human body louse but is also suspected to have other routes of transmission (see above). Carrion disease (B. bacilliformis) is transmitted by sand fly bites (Regnery and Tappero 1995, Billeter et al. 2008). Other known species of Bartonella pathogenic to humans have not been confirmed as vector-borne but have been demonstrated in arthropod species that occasionally feed on humans (Chang et al. 2001, Rolain et al. 2003). Rat fleas (Xenopsylla cheopis) can be infected with B. elizabethae, a human pathogen (Sanogo et al. 2003). Other rodent fleas (Ctenophthalmus nobilis) have been demonstrated to be capable of transmitting Bartonella taylorii and B. grahamii, the latter zoonotic (Bown et al. 2004). Detection of infection with both B. henselae and B. schoenbuchensis (also zoonotic) has been confirmed in deer keds (Lipoptena mazamae and Lipoptena cervi) (Dehio et al. 2004, Reeves et al. 2006, Matsumoto et al. 2008). Finally, other studies have identified Bartonella infection in arthropod species such as honeybees (Apis mellifera capensis and Apis mellifera scutellata), as well as novel Bartonella species in bat flies (Trichobius major) and bat bugs (Cimex adjunctus) (Jeyaprakash et al. 2003, Reeves et al. 2005).

Table 2.

Species in Which Bartonella henselae Seroreactivity or Bacterial Isolation Is Known

Domestic cats

Domestic dogs

Coyotes

Cattle

Horses

Florida panthers

Beluga

Porpoises

Cat fleas

Sheep ticks

Western black legged ticks

Stable flies

Deer keds

Beyond the Bartonella species established as arthropod vector-borne, there are other Bartonella species that have been detected in humans for which the method of transmission is unknown. A 2006 study in the southwestern United States identified five human patients hospitalized for febrile illness in which seroreactivity was noted to Bartonella species known to infect rodents. Interestingly, two of these patients also showed cross-reactivity to B. henselae, B. quintana, or B. elizabethae (Iralu et al. 2006). Another 2007 report from Thailand identified B. tamiae in three hospitalized patients who had described a history of finding rats in their homes, two of whom reporting exposure to rats within the 2-week time period preceding the development of clinical disease (Kosoy et al. 2008).

A tick vector for B. henselae was suspected in a 1992 report in which human patients bacteremic for B. henselae did not have previous direct contact with cats but did have a history of tick bites (Sanogo et al. 2003). More direct evidence to support the argument that ticks that feed on both humans and canine species may be responsible for transmission of Bartonellosis to humans was provided in a 2010 study in which B. henselae DNA was detected in up to 40% of sheep ticks at four locations in Europe, as well as a 2003 Italian study in which B. henselae was detected in 1.48% of sheep ticks (I. ricinus) removed from asymptomatic persons (Sanogo et al. 2003, Dietrich et al. 2010). In the Italian study, the initial source of B. henselae was not identified, and none of the human hosts were determined to have acquired the disease from the attached ticks (Sanogo et al. 2003). However, the sheep tick feeds on numerous sylvan species as well as humans, and has already been determined to be the vector responsible for the transmission of the agent of several human infectious diseases, including A. phagocytophilia (granulocytic anaplasmosis), Borrelia burgdorferi, Rickettsia helvetica, Babesia species, and the tick-borne encephalitis virus (Sanogo et al. 2003). Additionally, it is not uncommon for both ticks and their respective hosts to have dual infections with both Bartonella species as well as the established tick-borne pathogens (e.g., A. phagocytophilium and B. burgdorferi), and transmission of multiple infectious agents is an area of concern (Chomel et al. 2006, Holden et al. 2006, Billeter et al. 2008, Cotté et al. 2008).

Confirmation of B. henselae in sheep ticks still attached to human hosts provided at least one potential arthropod vector for Bartonellosis in individuals with no direct contact with cats or other vertebrate species, but did not establish that Ixodes was capable of transmitting B. henselae. However, the capability of a tick species (Dermacentor andersoni) to experimentally transmit B. bacilliformis between nonhuman primates was confirmed over 80 years ago when naive monkeys became infected after being bitten by ticks that had previously fed on monkeys already carrying the disease (Sanogo et al. 2003, Cotté et al. 2008). The potential for I. ricinus ticks to transmit B. henselae in vitro was established in a 2008 study in which sheep ticks were fed infected blood and then able to multiply the bacteria across developmental stages and then transmit viable B. henselae to naive blood (Cotté et al. 2008). However, the relevance of this finding has been questioned due to the use of a nonrepresentative B. henselae strain at ingested doses much higher than would likely occur in vivo (Telford and Wormser 2010).

Although infection of a human patient with B. henselae via a tick-borne vector has not yet been clearly identified, there is increasing scientific evidence that the arthropod route of transmission may be accounting for the many human cases of Bartonellosis in which no occupational exposure nor pet ownership is described in the patient history. Specific evidence is accumulating to support the potential for ticks of various species to act as vectors for interspecies transmission of this pathogen as well as other Bartonella species. Given the wide variety of rickettsial diseases that are transmitted by ticks, it may be advisable for both veterinarians and physicians to consider PCR or enriched blood culture screening of their respective patients if there is any history of exposure to ectoparasites and in cases of positive seroreactivity. In the case of human illness in which persistent fever or lethargy is present or the clinical picture is consistent with possible rickettsial disease, physicians may wish to consider screening for Bartonella if there is any previous direct animal contact even without a history of trauma. Additionally, although inconsistent in the literature, various studies have found much higher seroprevalence rates for Bartonella associated with occupational exposure than for the general populace, and primary care physicians may wish to consider screening for Bartonella in these individuals. Veterinarians and pet owners should consider implementing ectoparasite eradication and prevention programs to reduce the risk of B. henselae infection both to their pets and themselves, as well as reducing the risk of infection with other confirmed tick-borne diseases (Guptill 2003, Skerget et al. 2003, Breitschwerdt 2008).

Although infection with B. henselae is considered self-limiting in the majority of human patients (Breitschwerdt et al. 2007a), oral treatment may be considered for individuals with mild to moderate disease (Stevens et al. 2005). Efficacy, however, may be less than desirable. Inconsistencies in the response to treatment of the immunocompetent may be the result of the intracellular sequestration of B. henselae by the immune system (Chomel et al. 2006). Despite concerns over antibiotic efficacy, initiating treatment is recommended when disease attributable to B. henselae or other rickettsials is suspected and the associated clinical signs indicate a higher risk of mortality. This is especially true given the increasing amount of evidence in the literature that B. henselae may not in fact be self-limiting and may lead to recurring bacteremia in host species (Chomel et al. 2006, Breitschwerdt et al. 2007a, Gouriet et al. 2007). Rapid identification and directed treatment may decrease morbidity and mortality and alleviate the need for more invasive diagnostic testing.

An overall picture is emerging in which Bartonella species are becoming increasingly implicated in disease of various manifestations in both humans and nonhuman animal species. The previous idea that infection is largely confined to a small number of reservoir species and limited in terms of transmission is rapidly falling by the wayside and being replaced by a model in which the Bartonella species, like other rickettsial organisms, are transmitted by direct traumatic contact as well as by a variety of insect species (Table 3). Physicians should be aware that despite the name “cat scratch disease,” human illness caused by infection with B. henselae is not limited to individuals who have had any contact with cats whatsoever. In fact, it appears as though B. henselae is joining the ranks of other global pathogens in which rapid human and animal travel has the potential to cause widespread disease transmission and with the majority of cases going unrecognized and therefore untreated (e.g., Borrelia, Trichinella, Trypanasoma, Anaplasma, West Nile Virus, Hantavirus, Avian influenza, and Swine influenza) (Chang et al. 2001, Cotté et al. 2008). It is also likely that we have only scratched the surface in terms of information regarding not only B. henselae but also other intracellular pathogens as well, and future studies are likely to reveal a complex web of previously unknown global rickettsial disease in which reservoirs, susceptible host species, and arthropod vectors overlap. Given the ability of individual ticks in particular to carry and spread multiple pathogenic organisms simultaneously (Chomel et al. 2006, Billeter et al. 2008, Cotté et al. 2008), it is also likely that individuals testing positive for one pathogen may also be infected with other microorganisms that are either unrecognized thus far by the scientific community or are unable to be tested for at this time.

Table 3.

Known Routes of Transmission of Bartonellosis to Humans

Cat scratch

Cat bite

Dog scratch

Dog bite

Organ transplantation

Blood transfusion

Arthopod vector (human body louse, sand fly, other)

Perinatal

Iatrogenic

Footnotes

Acknowledgments

No funding of any kind was provided for this literature review article.

Disclosure Statement

None of the authors are aware of any financial, personal, political, or academic conflicts of interest. None of the authors maintain any commercial associations that might create a conflict of interest.

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