Bartonellosis is an infectious disease caused by Bartonella bacteria, and it can affect the skin, lymph nodes, eyes, liver, heart, or nervous system. Early symptoms of Bartonellosis may include fever, fatigue, headache, and tender swollen lymph nodes, but some people have mild or no symptoms. Illness can last weeks to months, and in people with weakened immunity it can be more severe and longer. Most otherwise healthy people recover with antibiotics, and doctors tailor treatment to the Bartonellosis type and organ involvement. Severe complications are uncommon with timely care, but people with HIV, recent transplants, or heart valve disease face higher risks and need close follow-up.
Overview
BartonellosisSymptoms
Early symptoms of bartonellosis often look flu-like: fever, headache, fatigue, and swollen lymph nodes, sometimes with a small bump at a scratch or bite. Severe cases may bring bone pain, eye problems, rash-like skin bumps, anemia, or heart valve infection.
Outlook and prognosis
Most people with Bartonellosis improve with timely antibiotics and supportive care, though recovery can be gradual. Fatigue and nerve or joint discomfort may linger for weeks to months, especially after severe or prolonged illness. People with weaker immune systems may need longer treatment and closer follow-up.
Causes and risk factors
Bartonellosis stems from Bartonella infection spread by cat scratches, fleas, body lice, or sandflies. Risk increases with flea-infested cats, homelessness or crowded living, Andean travel, animal-handling work, and weakened immunity, especially in children.
Genetic influences
Genetics plays a minimal role in Bartonellosis. This infection is driven by exposure to Bartonella bacteria, not inherited risk. Small variations in immune genes may influence severity or recovery, but environment and vector exposure matter far more.
Diagnosis
Doctors diagnose Bartonellosis using history of animal or insect exposure, exam findings, and tests. Blood tests (antibody or PCR), cultures, and sometimes imaging or tissue biopsy support the diagnosis of Bartonellosis and rule out look-alike infections.
Treatment and drugs
Bartonellosis is usually managed with targeted antibiotics, often a combination, chosen by the infection’s type and where it’s affecting the body. Treatment length can range from 2–12 weeks, guided by symptoms and follow-up tests. Supportive care—pain control, hydration, and managing complications like lymph node swelling or heart involvement—helps recovery.
Symptoms
Day to day, Bartonellosis can show up as fever, tiredness, and tender, swollen lymph nodes, often after a scratch or bite from an animal. Symptoms vary from person to person and can change over time. Early symptoms of Bartonellosis may be mild and easy to miss, then become more noticeable over days to weeks. Some people develop skin changes or eye trouble, and rarely, deeper organs or the heart can be affected.
Fever is common in Bartonellosis and may come and go. It can be low-grade or high, sometimes with chills and night sweats. It often starts within days to weeks of a scratch or bite.
Tender lumps appear near the scratch or bite, such as in the armpit, neck, or groin. Clinicians call this lymphadenopathy, which means enlarged lymph nodes. The skin over the area may feel warm or sore.
A small red bump or blister can appear where the skin was scratched or bitten. It may crust or scab and then fade over a week or two. In Bartonellosis, this is often the first sign people notice.
Many feel unusually tired and low on energy. Fatigue can linger even when the fever improves. Daily tasks may take more effort than usual.
How people usually first notice Bartonellosis?
Many people first notice bartonellosis after a scratch or bite from a cat, dog, or a tick exposure, when a small bump or blister appears at the site and nearby lymph nodes become swollen, tender, and warm over days to weeks. Others recognize the first signs of bartonellosis as a persistent low-grade fever, fatigue, headache, or body aches that don’t match a typical cold, sometimes with a streak-like rash or eye irritation if the infection involves the eye. In people with weaker immune systems, how bartonellosis is first noticed can be more sudden and severe, with higher fevers, widespread symptoms, or unusual skin or eye changes that prompt urgent medical care.
Types of Bartonellosis
Bartonellosis can look different from one person to the next because several Bartonella species infect humans, and each tends to favor certain tissues. People may have mainly fever and fatigue, skin changes from insect-bite sites, or swollen lymph nodes after a cat scratch. In more severe cases, blood vessel growths or heart valve infection can develop, especially in those with weaker immune systems. Clinicians often describe them in these categories:
Cat scratch disease
Usually caused by Bartonella henselae after a cat scratch or bite. It often brings a tender, swollen lymph node near the scratch, low-grade fever, and fatigue. Some develop eye irritation or nerve symptoms, but most recover with time and treatment.
Trench fever
Typically due to Bartonella quintana spread by body lice. It causes relapsing fevers, severe headaches, and shin bone pain that can come and go. People experiencing homelessness or living in crowded settings are at higher risk.
Carrion’s disease
Caused by Bartonella bacilliformis and spread by sand flies in parts of the Andes. It has two phases: an acute fever with severe anemia, then later wart-like skin lesions. Without prompt care, the early phase can be life-threatening.
Bacillary angiomatosis
Overgrowth of small blood vessels in skin or organs, usually from B. henselae or B. quintana. It appears as red-purple bumps or internal lesions and can bleed easily. It mainly affects people with weakened immune systems and needs targeted antibiotics.
Bartonella endocarditis
Infection of the heart valves by Bartonella species, often with negative standard blood cultures. Symptoms include fevers, weight loss, shortness of breath, and signs of heart failure over weeks to months. Early recognition matters because treatment differs from typical endocarditis and may require valve surgery.
Ocular bartonellosis
Eye involvement that can occur with several Bartonella species. People may notice blurred vision, floaters, eye pain, or light sensitivity, sometimes with a recent cat exposure. Prompt eye evaluation helps prevent lasting vision problems.
Neurologic involvement
Nerve and brain effects that can occasionally follow Bartonella infection. This can include headaches, confusion, seizures, or weakness, with symptoms ranging from mild to severe. Not everyone will experience every type.
Hepatosplenic disease
Liver and spleen involvement that can follow cat scratch disease. People may have fever, belly pain, and tender or enlarged liver or spleen, sometimes seen on imaging. This pattern is more common in children and often improves with appropriate antibiotics.
What genetics can tell you about symptoms
Certain Bartonella gene differences may influence how strongly the bacteria stick to blood vessel lining, linking to more prominent fever, rash, and eye irritation, and longer-lasting symptoms. Variants affecting immune signaling can tilt responses toward swollen lymph nodes, fatigue, and more severe, relapsing pain.
Causes and risk factors
Bartonellosis is an infection from Bartonella bacteria spread by cats, fleas, body lice, or sand flies in some areas such as the Andes.
These exposures raise your chance of Bartonellosis and of early symptoms of Bartonellosis after a scratch or bite.
There is no known inherited genetic risk, but weak immunity from HIV, cancer treatment, or transplant medicines raises the chance of severe illness.
Doctors distinguish between risk factors you can change and those you can’t.
Flea control, lice treatment, gentle cat handling, and travel precautions can lower exposure, while age and home region are not easily changed.
Environmental and biological risk factors
Bartonellosis develops after contact with certain animals or the insects that bite them, so risk often depends on your surroundings. Doctors often group risks into internal (biological) and external (environmental). Internal factors like a weak immune system or heart valve problems can raise the chance of a serious infection, while external factors center on where you live, work, or travel. Below are common biological and environmental risks to know.
Close contact with cats, especially kittens, raises exposure to Bartonella carried on claws or in saliva. Scratches or bites can move the bacteria through the skin.
Cat fleas can carry Bartonella between animals, and flea dirt on claws can contaminate scratches. Areas or seasons with heavy flea activity raise the chance of Bartonellosis.
Bartonella can spread through body lice that live in clothing seams. Crowded conditions or limited access to washing allow lice to multiply and increase risk.
In parts of the Andes in Peru, Ecuador, and Colombia, sandflies transmit Bartonella. Travel or residence in these valleys raises the risk of Bartonellosis.
Genetic risk factors
Bartonellosis is caused by bacteria, but your genes can influence how your body handles the infection and whether complications develop. When we talk about genetic risk factors for Bartonellosis, we’re usually referring to inherited conditions that change how the immune system works. Carrying a genetic change doesn’t guarantee the condition will appear, but it can make infection more severe or longer-lasting. Research is still growing, yet a few well-recognized inherited disorders clearly raise risk.
Primary immunodeficiencies: People born with inherited immune system conditions face a higher chance of severe or unusual Bartonellosis. These conditions weaken key defenses that normally keep Bartonella in check.
Chronic granulomatous disease: Changes in genes that power the chemical burst white blood cells use to kill germs can limit control of Bartonella. People with CGD have documented severe Bartonellosis, such as liver or spleen abscesses or bloodstream infection.
T-cell immune defects: Inherited problems that lower T-cell number or function reduce protection against bacteria that live inside cells. In this setting, Bartonellosis may last longer or lead to complications like skin or organ involvement.
Family history clues: Having close relatives with a known primary immunodeficiency increases the chance you carry the same condition. If present, this can raise your risk for severe Bartonellosis and may warrant earlier evaluation if early symptoms of Bartonellosis appear.
Lifestyle risk factors
Several day-to-day behaviors influence your chance of getting bartonellosis and how severe it becomes. The main lifestyle risk factors for bartonellosis involve how you handle cats and manage insect exposure, plus timely wound care and symptom follow-up. Diet plays a smaller role, mainly by affecting immune resilience and recovery.
Scratches or bites from kittens increase the chance of Bartonella entering the skin. Gentle handling and avoiding rough play lowers exposure.
Skipping flea prevention on cats or dogs sustains flea populations that can carry Bartonella. Regular veterinary flea control reduces infected fleas and contaminated claws.
Not washing cat scratches or bites promptly can let bacteria persist in the wound. Immediate soap-and-water cleaning and covering can cut infection risk.
Jobs or volunteering with cats raise contact with scratches and flea dirt. Wearing gloves, long sleeves, and using bite–scratch protocols reduces exposures.
Risk prevention
Bartonellosis is most often spread from cats (through scratches, bites, or fleas), body lice in crowded conditions, or sand flies in parts of the Andes. Prevention is about lowering risk, not eliminating it completely. Simple home habits, safer pet care, and targeted steps during travel can cut your chances of Bartonellosis. People with weaker immune systems may need extra care because infections can be more severe.
Avoid rough play that leads to scratches or bites. Use toys to play instead of hands.
Use regular, vet-recommended flea prevention for cats. Wash pet bedding on hot cycles and vacuum floors to reduce fleas at home.
Wash hands after playing with cats or cleaning litter boxes. Don’t let cats lick open cuts or broken skin.
Wash any scratch or bite right away with soap and water. Watch for early symptoms of Bartonellosis like fever or tender, swollen lymph nodes and contact a clinician if they appear.
Transmission
Bartonellosis spreads through insects and animal scratches rather than everyday contact. The most common route is a scratch or bite from a cat carrying Bartonella henselae; the bacteria are usually in flea dirt on the cat’s claws or teeth, and a lick to broken skin can also pass it on.
Other types are passed by specific insects: body lice can spread Bartonella quintana between people, and sand flies in some Andean regions transmit Bartonella bacilliformis. Bartonellosis is not airborne, and it does not spread through casual touching, coughing, or sharing food; how contagious bartonellosis is depends on exposure to these vectors and is generally low without them.
When to test your genes
Consider genetic testing only if a clinician suspects an inherited immune issue, unusual severity, or repeated Bartonella infections despite treatment. For most people, Bartonellosis is infectious, not genetic, so routine gene testing isn’t needed. If you have strong family history of immune disorders or severe, atypical disease, ask about immunogenetic evaluation.
Diagnosis
Bartonellosis often comes to light when everyday activities start feeling harder because of fever, tender lymph nodes, or new eye or skin changes. Doctors usually begin with a careful history, a physical exam, and targeted tests based on your symptoms. Because early symptoms of Bartonellosis can mimic other infections, the diagnosis of Bartonellosis typically combines exposure clues, exam findings, and lab evidence.
Your provider will ask about recent cat scratches or bites, flea exposure, body lice, or travel and housing conditions. These details help estimate the chance of Bartonella infection and guide which tests to order.
The exam looks for tender, swollen lymph nodes, fever, skin bumps, or eye findings. In some people, signs of heart infection or liver and spleen tenderness may point testing in a specific direction.
A complete blood count and inflammatory markers can suggest an active infection. Liver enzyme tests may be added if there are abdominal symptoms or imaging concerns.
Blood tests that measure Bartonella antibodies (IgG/IgM) can support the diagnosis when levels are elevated. Rising levels over time are more convincing than a single result, and cross-reactions with other germs can sometimes occur.
Stages of Bartonellosis
Bartonellosis does not have defined progression stages. This umbrella term includes different Bartonella infections that behave in distinct ways—some are sudden, some occur in two phases, and others stay localized or come and go. Different tests may be suggested to help confirm the cause, including a physical exam for skin bumps or swollen lymph nodes, blood tests (antibody or PCR), and, in certain situations, a blood smear, heart ultrasound, or imaging if organs are involved. Doctors often consider recent animal or insect exposure and early symptoms of Bartonellosis like fever, fatigue, and a tender lump near a scratch when deciding on next steps.
Outlook and prognosis
Many people ask, “What does this mean for my future?”, especially after being told they have bartonellosis. For most healthy adults with cat-scratch disease (a common form), the outlook is good: swollen lymph nodes and fatigue usually ease over weeks to a few months, and lasting problems are uncommon. When infection spreads to the eye, liver, spleen, or nervous system, recovery can take longer and may require targeted antibiotics and follow-up to watch for complications.
Doctors call this the prognosis—a medical word for likely outcomes. People with weaker immune systems, such as those on chemotherapy or with advanced HIV, face a higher risk of severe illness like bacillary angiomatosis or blood-culture–positive infection; they may need longer treatment and sometimes maintenance antibiotics to prevent relapse. Mortality is low in otherwise healthy people with bartonellosis, but in severe, untreated cases—especially in immunocompromised individuals—the risk of serious complications and death rises. Early symptoms of bartonellosis like fever, tender nodes, eye redness, or new skin lesions should prompt timely care, because early antibiotics can shorten illness and reduce complications.
Everyone’s journey looks a little different. Most people fully recover and return to normal activities, though fatigue can linger for a while. Keep regular appointments—small adjustments can improve long-term health. Talk with your doctor about what your personal outlook might look like, including how your immune health, exposure risks (such as cats or fleas), and any other conditions may shape recovery and the chance of relapse.
Long-term effects
For most people with Bartonellosis, the infection clears within weeks to months, and life returns to normal. While early symptoms of Bartonellosis may be mild, a small number of people develop issues that last longer or show up later. Long-term effects vary widely and depend on the species involved and your overall health.
Tiredness and low energy can linger after the infection settles. It may ebb and flow for weeks or months before fading.
Swollen or tender lymph nodes can take a long time to shrink. Some may stay slightly enlarged after Bartonellosis even when you feel well.
Inflammation of the retina or optic nerve can leave blurred vision or small blind spots. Many recover fully, but a few have partial, lasting changes.
Headaches, concentration trouble, or balance issues can persist after severe nerve involvement. These usually improve with time, though rarely they can last longer.
How is it to live with Bartonellosis?
Living with bartonellosis can range from a short, annoying stretch of fever, swollen lymph nodes, and fatigue to a longer phase of aches, brain fog, and low stamina that makes work, school, and exercise feel harder than usual. On flare days, people may pace themselves, rest more, and plan around medical visits or antibiotics, which can ripple into family routines and social plans. Those close to you may take on extra tasks, help with childcare or pets, and need reassurance that the infection is treatable and not a sign of something more dangerous. Many find that clear communication, gradual return to activity, and support at home and work ease the disruption while recovery continues.
Treatment and drugs
Bartonellosis treatment focuses on clearing the infection and easing symptoms so daily activities become manageable again. Doctors usually prescribe antibiotics, often for several weeks; common choices include doxycycline, azithromycin, rifampin, or combinations, with the exact plan depending on the Bartonellosis type, your age, pregnancy status, immune health, and whether organs like the liver, heart, eyes, or nervous system are involved. Supportive care can make a real difference in how you feel day to day, which can include fluids, pain and fever reducers, eye care if vision is affected, and treatment for complications such as endocarditis, which may require prolonged antibiotics and occasionally surgery. Treatment plans often combine several approaches, and people with weaker immune systems (including those with HIV) may need longer courses or additional medicines. Keep track of how you feel, and share this with your care team, especially if you notice side effects or if early symptoms of Bartonellosis don’t improve within a few days of starting therapy.
Non-drug treatment
Alongside medicines, non-drug therapies can ease discomfort, protect affected areas, and support healing. These steps focus on restful routines, careful skin care, and tailored activity so daily life feels more manageable. They may also reduce the chance of complications while you’re waiting for antibiotics to work or recovering afterward. These steps also help when early symptoms of Bartonellosis are mild and you’re watching and waiting.
Wash cat scratches or bites with soap and water for at least 20–30 seconds, then rinse well. Pat dry and cover with a clean bandage. Watch for spreading redness, pus, or increasing pain.
Use warm compresses on tender, swollen nodes for 10–15 minutes several times a day. Avoid squeezing or massaging swollen areas, which can worsen irritation. Gentle neck or arm movement helps reduce stiffness.
Plan short activity blocks with breaks to prevent “push‑and‑crash” fatigue. Prioritize sleep and keep a regular schedule. What feels difficult at first can become easier as your energy returns.
Sip water or oral rehydration drinks regularly to replace fluid lost with fever or sweating. Choose balanced meals with protein, fruits, vegetables, and whole grains to support recovery. Smaller, frequent meals may be easier when appetite is low.
Your genes may have an impact on how drugs work for you
Even before a pill reaches your bloodstream, your genes can shape how quickly you break it down and how strongly you feel its effects. In bartonellosis, genetics may influence antibiotic response and side‑effects, guiding dose choices or alternative medications when needed.
Pharmacological treatments
Antibiotics are the mainstay for bartonellosis, chosen based on how severe the infection is and where it shows up in the body. Even when early symptoms of bartonellosis are mild, antibiotics may be used to shorten swollen lymph nodes or prevent complications. More serious disease—like eye involvement, widespread skin lesions, or heart valve infection—usually needs combination therapy and longer courses. Not everyone responds to the same medication in the same way.
Often used when lymph nodes are tender and swollen in cat-scratch disease. It can shorten the time lymph nodes stay enlarged and is commonly used in pregnancy or in younger children.
A first choice for more severe bartonellosis, including eye disease, bacillary angiomatosis, or suspected spread beyond lymph nodes. Doctors may combine it with rifampin for tougher infections or use it for several weeks.
An alternative when doxycycline isn’t suitable, including for bacillary angiomatosis. It is also a pregnancy-friendly option for bartonellosis when treatment is needed.
Added to doxycycline for severe or deep-seated bartonellosis, such as eye, neurologic, or liver/spleen involvement. It is not usually used alone and can interact with many other medicines.
Genetic influences
Genetics don’t cause Bartonellosis; exposure to infected cats, fleas, lice, or sand flies does. Your genes generally don’t decide whether you get infected, but they can influence how strongly your immune system responds and how quickly you recover. People with rare inherited immune system conditions, or those taking immune‑suppressing medicines, are at higher risk for severe or persistent Bartonellosis. Scientists are also studying common gene differences tied to the body’s early defenses—like how efficiently certain immune sensors recognize bacteria—which could play a small role in genetic susceptibility to Bartonellosis, though current evidence is limited. Having a genetic risk is not the same as having the disease itself. If several family members have had unusually severe infections, consider sharing that pattern with your clinician so you can discuss whether any further evaluation, including genetic counseling, fits your situation.
Is Bartonellosis genetic?
Genetics plays a minimal role in Bartonellosis. This infection is driven by exposure to Bartonella bacteria, not inherited risk. Small variations in immune genes may influence severity or recovery, but environment and vector exposure matter far more.
Pharmacogenetics—how genetics influence drug effects
Treatment for Bartonellosis often involves antibiotics such as doxycycline or azithromycin; in severe infections, regimens may include rifampin or an aminoglycoside like gentamicin. Genetic differences can influence how your body responds to these medicines and the chance of side effects. The clearest example is with aminoglycosides: certain inherited changes in mitochondrial DNA can make people much more likely to develop permanent hearing loss even at usual doses. With macrolides such as azithromycin, people with an inherited tendency to abnormal heart rhythms (long QT syndrome) may face a higher risk of rhythm problems, so doctors may review an electrocardiogram (ECG) and other risk factors before choosing a drug. Variants in liver enzyme and drug‑transporter genes can alter how quickly some antibiotics are cleared, but in practice dosing for Bartonellosis relies more on kidney and liver function, other medications, and the severity of infection than on routine genetic testing. Genetic testing can sometimes identify how your body handles certain antibiotics or your risk for rare side effects, and it’s usually considered when an aminoglycoside is planned or there’s a personal or family history of unusual drug reactions.
Interactions with other conditions
People with HIV, those on chemotherapy, or transplant recipients may have more severe Bartonellosis, and the infection can spread beyond lymph nodes to the skin, liver, spleen, or bones. Doctors call it a “comorbidity” when two conditions occur together, and Bartonellosis alongside immune-suppressing illnesses often means longer illness and a higher chance of relapse without targeted treatment. Existing heart disease matters too: in people with damaged or artificial valves, Bartonella can trigger a hard‑to‑detect heart valve infection (endocarditis), which needs specific antibiotics and close follow‑up. Coinfections with other vector‑borne illnesses, such as Lyme disease in tick‑exposed areas, may happen and can blur the picture when fatigue, fever, or nerve symptoms overlap. Because early symptoms of Bartonellosis can look like mono or the flu, some living with other causes of swollen glands or tiredness may be misdiagnosed at first. In complex situations, coordinated care between infectious disease specialists and the team managing the other condition helps guide testing and safe treatment choices.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described feverish illnesses that followed scratches from animals or bites from insects, often with tender lumps in the armpit or neck and a lingering fatigue that didn’t make sense at the time. Families and communities once noticed patterns: a child scratched by a kitten developed a swollen node a week later, or a traveler returned from the countryside with fever and a new rash after lice exposure. These everyday stories foreshadowed what we now group under Bartonellosis.
First described in the medical literature as distinct infections tied to specific settings, the story unfolded in pieces. In the Andes, doctors in the early 1900s documented “Oroya fever” with severe anemia after sand fly bites, and later a skin eruption called “verruga peruana.” In World War I, crowded trenches brought “trench fever,” spread by body lice and marked by relapsing fevers and aching shins. Decades afterward, pediatric clinics connected “cat scratch disease” to kittens, showing how a small skin bump could be followed by swollen lymph nodes and low-grade fever. Initially understood only through symptoms, later laboratory work linked these conditions to related bacteria in the Bartonella group.
Over time, descriptions became more precise as culture techniques, serology, and then DNA methods identified the species behind different patterns of illness. What once seemed like separate conditions—cat scratch disease, trench fever, and Carrion’s disease—were recognized as parts of the Bartonellosis family. With each decade, clinicians also learned who was most at risk: people living with weaker immune systems, those in crowded conditions with lice, travelers to regions with sand flies, and anyone in close contact with young cats.
In recent decades, knowledge has built on a long tradition of observation. Molecular tests clarified that Bartonella henselae commonly causes cat scratch disease, Bartonella quintana underlies trench fever and some bloodstream infections in people experiencing homelessness, and Bartonella bacilliformis drives the Andean illness carried by sand flies. Doctors also recognized new manifestations—such as eye inflammation, liver and spleen lesions, and heart valve infection—in both children and adults.
Despite evolving definitions, the arc of Bartonellosis follows a familiar path in medicine: careful bedside notes, clues from everyday life, and then laboratory proof. Today’s understanding blends those early field observations with modern microbiology, helping doctors match symptoms and exposure history with accurate tests and targeted treatment. Looking back helps explain why Bartonellosis can appear so differently from one person to the next—and why asking about pets, travel, and insect exposure remains a key part of the medical history.