The translation to Italian of this article can be found here.
A dozen of the 21 species of bacteria belonging to the genus Bartonella is potentially able to generate symptomatic infections in humans, with manifestations that may have varying severity: from diseases that resolve spontaneously to conditions that endanger the patient’s life. The duration may also vary from acute infections of a few days to chronic infections (Mogollon-Pasapera E et al. 2009).
Cat scratch disease and other manifestations
The best known of these diseases is perhaps the “cat scratch disease” due to Bartonella henselae and transmitted to men by cats, through bites or scratches. Cat-to-cat transmission occurs through fleas (Ctenocephalides felis) and 50% of domestic cats are healthy carriers of this pathogen (Massei F et al. 2005). In general, the cat’s scratch disease is limited to having a local manifestation and resolves itself; in other cases, it may have systemic manifestations such as fever, headache, fatigue, and loss of appetite. Treatment – if required – can range from 5 days of azithromycin for mild forms, to a combination of doxycycline (or erythromycin) and rifampicin for 1-2 months, for neurological forms (Klotz SA et al. 2011). A review of the major human diseases associated with Bartonella, of transmission pathways, and of recommended antibiotic therapies can be found in Table 1 (Mogollon-Pasapera E et al. 2009). As can be seen, depending on the species of Bartonella involved, clinical manifestations may include retinitis, endocarditis, angiomatosis (vascular proliferation), Carrion’s disease (fever, anaemia, jaundice), adenopathy, and Quintana fever (high fever with myalgia, headache, fatigue).
Bartonellosis or borreliosis?
A recent French study has suggested the possibility that a chronic disease characterized by fatigue and myalgia, with or without headache, may be due to a Bartonella infection (especially from B. henselae) and may be transmitted by ticks (Vayssier-Taussat M et al. 2016). The study considered 66 people who had reported the appearance of chronic symptoms following a tick bite; the patients were all seronegative for Borrelia burgdorferi, the etiological agent of Lyme disease. Their blood was cultured for 45 days on soil enriched with sheep’s blood. Six of the 66 samples saw the formation of bacterial colonies ascribable to the genus Bartonella: in three cases it was possible to identify genetic material of B. henselae, in the other 3 of three other species of Bartonella (Table 2). The same test conducted on the blood of 70 healthy donors was negative in each sample. This study suggests (but does not demonstrate) that nonspecific symptoms, such as fatigue and myalgia, as a result of tick bites, may be due to a Bartonella infection (particularly to B. henselae) rather than being an expression of Lyme disease. The presence of Bartonella henselae in the stomach of Ixodes ricinus (the vector of Lyme disease in Europe) has recently been reported in France, Portugal and Germany (Dietrich F et al 2010), but not in Italy (Mancini F et al. 2014).
In agreement to the French study, an article from the Open Medicine Institute has recently reported a case of Lyme disease (erythema migrans) refractory to treatments, characterized by fatigue, headaches and difficulty in maintaining the balance, in which a culture on blood highlighted the presence of Bartonella henselae. Treatment with rifampicin and clarithromycin for 5 months resolved the symptomatology. The study authors pointed out that the patient’s serology for Bartonella was negative, and only the 21-day cell culture performed by the Galaxy Diagnostics laboratory was able to detect B. henselae infection (Kauffman DL et al. 2017).
Bartonellosis might be a further tick-borne infection transmitted by tick bites, but more studies are warranted. The main symptoms of this tick-borne infection seem to be non-specific (fatigue, myalgias, headaches) and they do not respond to treatments usually administered for Borrelia burgdorferi infections. Tick-borne bartonellosis could, therefore, account for at least some of the cases of post-treatment Lyme disease syndrome, a chronic condition refractory to treatments, towards which evolves 10-20% of cases of acute Lyme disease.