Bartonella

B. henselae is the most common Bartonella bacterium that causes infection and is commonly referred to as “cat-scratch disease.” Historically, the B. henselae bacterial infection was thought to have been transmitted through an infected cat’s scratch or bite. However, recent research suggests that vectors such as ticks, chiggers, and mosquitoes can also infect humans with B. henselae. Fleas from infected cats can also transmit the bacteria to humans. == B. quintana ==

B. quintana is also a common Bartonella pathogen that infects humans, often referred to as “trench fever.” B. quintana primarily spreads through body louse. This bacterium is known to only infect humans. While B. henselae is the most common Bartonella bacteria, B. quintana still sees new cases of the infection every year globally. == B. bacilliformis ==

B. bacilliformis is a bacteria that humans can contract various Bartonella infections from. Specific parts of South America have vectors that can transmit this infection, such as Peru and the Andes Mountains. This bacterium is spread through the bite of sandflies that have B. bacilliformis. However, research about the cycle of this disease is unknown. This bacterium is responsible for acute and chronic Bartonella, also referred to as Carrion's disease, and can cause serious health complications. ==History==

Bartonella species have been infecting humans for thousands of years, as demonstrated by Bartonella quintana DNA being found in a 4000-year-old tooth. The genus is named for Alberto Leonardo Barton Thompson (1871–October 26, 1950), an Argentine-born Peruvian scientist. The numerous Bartonella species have different origins. For many Bartonella species discoveries, dental pulp was the body source where the bacteria was found. Bartonella henselae, B. quintana, and Bartonella tribocorum are just some of the species discovered through dental pulp. While the discoveries of the various bacteria are different, B. henselae, B. quintana, and Bartonella bacilliformis have the most researched origins. B. henselae The B. henselae pathogen was discovered in 1990 by researchers through biological experiments involving skin lesions. Carrion's disease has two distinct phases, Oroya fever and verruga peruana. Oroya fever occurs after one’s initial exposure to the B. bacilliformis bacteria and is considered the acute phase of the illness. Then, verruga peruana can occur after one’s recovery from the bacteria and is considered the chronic phase of the disease. ==Infection cycle==

Bartonella species are well-known to be transmissible to both animals and humans through various other vectors, such as fleas, lice, and sand flies. Bartonella bacteria are associated with cat-scratch disease, but a study in 2010 concluded, "Clinicians should be aware that ... a history of an animal scratch or bite is not necessary for disease transmission." All current Bartonella species identified in canines are human pathogens. Mammal hosts, cat bites, and cat saliva have also been shown to spread the bacteria. The arthropod Bartonella infection cycle starts through the bite of an insect, typically a flea, lice, or other common blood-sucking arthropods. The infected arthropod’s bite causes the Bartonella bacteria to enter the host–human or animal. In the early stages of the bite, Bartonella cannot infect red blood cells immediately, causing the host to show no symptoms or signs of infection. Instead, the bacteria must find a “primary niche”, or a temporary place of existence in the body to prepare for the next stage of infection. From the primary niche, the Bartonella bacteria is able to move into the bloodstream. However, there is no specific research that indicates that Ixodes ricinus ticks, or other tick species, have transmitted their Bartonella infection to humans, making it an area of ongoing research. As of 2025, the Centers for Disease Control and Prevention states that there is no evidence of ticks being able to transmit Bartonella to humans. One study in Austria found Bartonella DNA present in Ixodes ricinus ticks, but the study concluded that ticks are not a risk factor for humans in developing Bartonella species such as Bartonella henselae or Bartonella quintana. Since there are various ticks and Bartonella species, more research is needed to make causal links between tick species and Bartonella in animals. == Acute Bartonella and Chronic Bartonella ==

Acute and chronic Bartonella are two different infections that individuals can develop after contracting the Bartonella bacilliformis bacteria. Acute Bartonella Acute Bartonella, also referred to as Oroya fever or Carrion's disease, is an infection caused by the Bartonella bacteria species, B. bacilliformis. Animals that have acute Bartonella may also experience the same symptoms as humans; however, it varies based on the animal species. Bartonella’s various bacterial species can also have different symptoms with varying degrees of severity. Chronic Bartonella Humans and animals that are infected with any strain of the pathogen can also develop chronic Bartonella, but it is particularly prevalent and associated with the B. bacilliformis pathogen. While different, acute and chronic Bartonella are sometimes both treated by antibiotics. The type of antibiotic and duration is dependent on the Bartonella species. Heart inflammation is the most serious complication from Bartonella infections. Those with comorbidities or autoimmune diseases can also experience Bacillary angiomatosis, which is a medical condition that can create cysts on organs and bones in the human body. These cysts can develop on the skin and can appear red or dark. Bacillary peliosis can also occur, causing liver problems. == Risk factors for developing Bartonella ==

Various lifestyles and pre-existing medical conditions can put someone at a higher risk for being infected with Bartonella. Bartonella is a zoonotic bacteria and can increase farmers', or those who work with livestock, likelihood of being infected with it. Insect vectors that can transmit Bartonella, such as fleas, can be present in some farm animals, leading to farmer exposure. In one case, a sheep farmer contracted B. quintana after handling sheep. == Vaccine ==

Currently, a vaccination for Bartonella does not exist. In one study done on mice, the CFA, or CAMP-like autofactor transporter that is specific to Bartonella, was found to protect mice against the Bartonella tribocorum species. However, CFAs, or a bacterial protein that the immune system targets, vary greatly across different Bartonella species. While mice could receive a B. tribocorum vaccine and be protected from the bacterium, humans and mice would not be protected against other Bartonella bacteria. Since Bartonella vaccinations are not available for humans or animals, some actions and methods can prevent someone or something from contracting the bacteria. == Preventative measures ==

Bartonellosis infections from Bartonella bacteria can be prevented in various ways. Pets should be protected from fleas and lice, and wounds should be covered during direct animal contact, specifically when handling cats. These preventative methods include keeping pets indoors, avoiding contact with fleas and cats that have fleas, and stray cats. ==Pathophysiology==

Bartonella infections can produce a wide range of symptoms. The course of the diseases (acute or chronic) and the underlying pathologies are variable. ==Treatment==

Treatment is dependent on which species of Bartonella is found in an individual. While Bartonella species are susceptible to a number of standard antibiotics in vitro—macrolides and tetracycline, for example—the efficacy of antibiotic treatment in immunocompetent individuals is currently not known. ==Epidemiology==

Homeless intravenous drug users are at high risk for Bartonella infections, particularly Bartonella elizabethae. Bartonella elizabethae seropositivity rates in this population range from 12.5% in Los Angeles, to 33% in Baltimore, Maryland, 46% in New York City, and 39% in Sweden. ==Phylogeny==

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN). }} == References ==