Cat-scratch disease (CSD), sometimes called cat scratch fever, is an infection caused by the bacterium Bartonella henselae and is a common cat disease. While many people know it as a condition that follows a scratch from a playful kitten, the reality is more complex: the disease involves cats, humans, and even fleas as part of its transmission cycle. In humans, symptoms range from a small blister at the scratch site to swollen lymph nodes, flu-like illness, and in rare cases, serious complications involving the eyes or nervous system. Cats themselves usually act as silent carriers, rarely showing signs of disease, but they remain a key link in spreading the infection.

Understanding cat scratch disease and its symptoms is about knowing how to take care of your health, and part of knowing how to care for a cat. Learning how the bacteria spreads and how to prevent infection is essential for cat owners, families with young children, and anyone who interacts regularly with cats or kittens. This article delves into the disease in depth, from early warning signs to prevention strategies, providing a practical guide for both pet owners and patients.

What is Cat Scratch Disease?

Cat Scratch Disease, sometimes referred to as cat scratch fever, is an infectious disease or illness usually caused by the bacterium Bartonella henselae. The infection often results in swollen lymph nodes, fever, fatigue, and a small lesion at the site of a scratch or bite. CSD was first described in the 1930s, but the bacterium responsible was not identified or associated with cats until the 1950s, which eventually allowed medical professionals to understand its transmission and clinical presentation more clearly.

How the Bacteria Spreads

The primary route of transmission to humans is through scratches or bites from cats, particularly kittens, which are more likely to be infected by B. henselae and to carry it on to people. Fleas play a key role in spreading the bacteria between cats, and flea feces can contaminate a cat’s claws or fur, creating a risk for humans during play or handling. Cats can also get the disease through contact with an infected cat’s saliva or other fluids entering their eyes. Less commonly, humans can become infected if an infected cat licks an open wound, allowing bacteria to enter directly into the broken skin. 

Common Risk Groups

Specific populations are more susceptible to cat scratch Disease due to behaviour, biology, or immune status. These groups include:

1. Children: Younger individuals may receive scratches without cleaning the wound promptly. Once your child gets cat scratch disease, it's less likely for them to catch it again. 

2. Immunocompromised Individuals: People with weakened immune systems, including those with HIV/AIDS or those receiving chemotherapy, are at higher risk of severe or atypical disease manifestations, such as eye involvement.

3. Cat Owners: Owners of kittens or cats with poor flea control face a higher risk of exposure, as young cats are more likely to carry the bacteria and transmit them to humans through scratches or bites.

Understanding how Cat Scratch Disease spreads and recognizing who is at the most significant risk can help prevent infection. Preventative measures include prompt cleaning of scratches or bites, maintaining flea control for pets, and supervising children when interacting with cats.

Cat Scratch Disease Symptoms in Humans

When humans become infected with Bartonella henselae, the signs can range from mild skin irritation to more noticeable systemic illness. Early symptoms often start near the scratch or bite site before spreading to the lymph nodes and, in some severe cases, the eyes or other organs. Recognizing the symptoms of cat scratch disease in humans is essential for timely treatment. 

Early Signs

The first indication of cat scratch disease symptoms in humans is often reddening or swelling of a cat bite or scratch. The more irritated-than-normal lesion usually appears within three to ten days after exposure and may look like a minor skin irritation or pimple. It represents the body’s initial response to the bacteria Bartonella henselae introduced by the cat. 

The lesion may be mistaken for a minor skin irritation initially, but shortly after this physical symptom appears, mild fever, chills, and tiredness will accompany enlarged lymph nodes, and you’ll know there's a larger issue at play than a regular scratch. Nearby lymph nodes often become swollen, tender, or warm to the touch. This swelling is a hallmark sign of cat scratch disease symptoms in humans and typically occurs one to two weeks after the scratch. The nodes may remain enlarged for several weeks or months if untreated, serving as an important diagnostic clue.

Flu-like Symptoms

Many individuals with cat scratch disease experience flu-like symptoms, which can make the infection feel more systemic. These symptoms often appear alongside or shortly after lymph node swelling and can vary in intensity depending on the individual’s immune response. 

Common flu-like symptoms include:

1. Fever 

2. Fatigue 

3. Headaches

4. Body aches

The chart below outlines what each flu-like symptom looks and feels like when associated with cat scratch disease.

Delayed or Chronic Symptoms in Untreated Cases

If cat scratch disease goes untreated, some individuals may develop delayed or chronic symptoms. Swollen lymph nodes can remain enlarged for months, and more severe complications may arise, such as eye inflammation, nervous system involvement, or infection of internal organs. Immunocompromised patients are particularly at risk for these severe manifestations, highlighting the importance of early recognition and medical evaluation.

Cat Scratch Disease Eye Symptoms

Cat scratch disease can also affect the eyes. When the infection spreads to the eye, it may lead to a condition known as ocular bartonellosis. This is a rare but potentially serious complication that can cause redness, swelling, pain, and even changes in vision, making it essential to recognize the early signs and seek medical care quickly.

Ocular Bartonellosis

Cat Scratch Disease can extend beyond the skin and lymph nodes when Bartonella henselae bacteria enter the bloodstream. In rare cases, CDS may exhibit systemic symptoms and result in deep-rooted infections at various sites, including the eye, causing ocular bartonellosis. Ocular Bartonellosis is more common in children and young adults, presenting a range of systemic and ocular symptoms. 

Common Symptoms

There are a handful of common symptoms associated with Ocular Bartonellosis. The list below provides a detailed explanation of these symptoms. 

1. Redness: Eye redness results from inflammation of the conjunctiva and surrounding tissues, which could be mistaken for viral or bacterial conjunctivitis. However, redness linked to cat scratch disease is more persistent and may worsen despite standard antibiotic eye drops.

2. Blurred Vision: Blurred or distorted vision occurs when inflammation affects the retina or macula, interfering with light processing. Some patients describe vision that appears foggy or as if they are “looking through water.”

3. Sensitivity to Light: Light sensitivity is a hallmark of inflammation inside the eye, particularly the iris and retina. Patients often report difficulty being outdoors or in bright rooms, sometimes paired with eye pain.

4. Conjunctivitis-like Irritation: This irritation can mimic pink eye with symptoms like tearing, itching, and discharge. The difference lies in systemic symptoms. Patients may simultaneously experience fever, fatigue, or swollen lymph nodes, which help distinguish cat scratch disease eye symptoms from simple conjunctivitis.

Potential Severe Complications

There are two potential severe complications when it comes to cat scratch disease symptoms, such as:  

1. Neuroretinitis: One of the most serious complications, neuroretinitis, involves inflammation of both the optic nerve and retina. It produces sudden vision loss, sometimes in one eye, accompanied by a distinctive “macular star” pattern visible on retinal scans. Recovery may take months, and in some cases, residual vision deficits remain despite antibiotic therapy.

2. Optic Nerve Swelling: Known medically as optic disc edema, this condition occurs when an infection triggers swelling at the head of the optic nerve. If untreated, patients may notice blind spots, tunnel vision, or total loss of vision. Swelling can also cause the optic nerve fibres to sustain permanent damage, underscoring the urgency of prompt treatment by an ophthalmologist. 

Cat Scratch Disease Symptoms in Cats

Most cats infected with Bartonella henselae show no outward signs of illness, even though they can carry the bacteria in their bloodstream for weeks or months. These cats are often completely healthy in appearance, but can transmit the bacteria to humans through scratches, bites, or flea contact. Kittens are more likely to be carriers than adult cats, which explains why human infections are often linked to interactions with young cats.

Unlike humans, cats are usually asymptomatic carriers, meaning they harbor the bacteria without developing significant illness. Even though they are infected, most cats' immune systems prevent severe disease. This makes cats unique in the transmission cycle: they spread the infection but rarely suffer from it themselves. 

Rare (But Possible) Signs

Although uncommon, some cats may show mild or subtle signs of cat scratch disease. In humans, these same signs are often much more pronounced. Rare symptoms to watch for in your furry friends include:

• Lethargy: Cats may sleep more than usual, show less interest in play, or move sluggishly around the house. If your cat is experiencing lethargy, they may groom themselves less, move and play less, act withdrawn, avoid stairs or jumping, and sleep more than usual. 

• Swollen Lymph Nodes: Cats rarely develop noticeable lymph node swelling, but it can sometimes be felt near the site of scratches or bites. Areas of lymph node swelling on cats include the neck, behind the jaw, in front of the shoulders, armpits, groin area, and behind the knee joint.  

• Poor Appetite: Cats may eat less than usual or refuse favorite treats, leading to mild weight loss if prolonged. 

Fleas As A Hidden Culprit

When a flea bites an infected cat, the Bartonella henselae bacteria that it ingests can live in the flea’s gut and be passed in its feces, often called “flea dirt.” Cats can get flea dirt on their claws or fur while grooming, and if they scratch or bite a person, the bacteria can enter the skin and cause infection.

Transmission cycle:

1. Flea bites an infected cat → bacteria enter the flea’s gut.

2. Flea excretes bacteria in its feces (“flea dirt”).

3. A cat grooms itself, contaminating its claws and fur with flea dirt. Cats can also ingest infected feces while grooming.

4. Bacteria multiply in the cat: Once infected, cats (especially kittens) can carry the bacteria in their blood for weeks or months without showing any signs of illness. The fleas can also lay infected eggs, which then hatch and go into the environment, spreading the disease further.

5. A cat scratches or bites a person → bacteria enter the wound.

6. Human develops a small lesion and, sometimes, a more widespread illness.

Source

Because asymptomatic cats can carry the bacteria without showing signs, even healthy-looking kittens can transmit it. Regular flea prevention is one of the simplest and most effective ways to reduce the risk of cat scratch disease.

Difference Between Cat Scratch Disease Symptoms in Cats and Other Feline Illnesses

When clinical signs of Bartonella henselae appear in cats, they’re usually mild and nonspecific: short, low-grade fever, subtle lethargy, decreased appetite, or mild local lymph node enlargement; many of these changes can easily be indicators of other feline diseases.

This makes it essential to distinguish cat scratch disease symptoms in cats from other, more common feline illnesses:

• Upper respiratory infections (like feline herpesvirus or calicivirus): Often cause sneezing, runny nose, and eye discharge—signs you wouldn’t expect from Bartonella.

• Feline infectious peritonitis (FIP): Usually leads to persistent fever, weight loss, and sometimes fluid buildup in the abdomen—much more severe than the mild signs linked to Bartonella.

• FIV or FeLV infections: May cause repeated infections and long-term illness, whereas Bartonella rarely progresses this way in cats.

Bartonella infection in cats usually presents as mild symptoms, while other feline diseases will present these symptoms in a more serious and severe way. This is a main indicator that helps veterinarians tell whether they’re dealing with a potential cat scratch fever diagnosis or something more serious.

Treatment and Management of Cat Scratch Disease

Treatment for cat scratch disease depends on whether it’s affecting a human or a cat and how severe the symptoms are. In most humans, the infection is mild and may resolve on its own, but antibiotics and supportive care are recommended for persistent or complicated cases. Understanding proper management helps reduce discomfort, prevent complications, and limit the spread of infection.

Human Treatment

Treatment for cat scratch disease in humans depends on symptom severity. Most cases are mild and self-limiting, but medical intervention is necessary for more pronounced or persistent symptoms, especially in immunocompromised individuals.

There are a few different options for the treatment of cat scratch disease in humans:

Eye Infections (in Humans)

If ocular bartonellosis develops, prompt treatment is critical to prevent vision damage. Treatment may involve a combination of oral antibiotics and, in some cases, corticosteroids to reduce inflammation. Regular monitoring by an eye specialist ensures that complications like neuroretinitis or optic nerve swelling are addressed early.

Lifestyle Measures

Supporting overall health can help the body recover more efficiently:

• Hydration: Maintaining fluid intake helps the immune system function optimally.

• Nutrition: A balanced diet rich in vitamins and minerals supports recovery.

• Rest: Adequate sleep and reduced physical stress help resolve fatigue and strengthen immunity.

Treatment For Cats

Most cats do not require treatment since they are usually asymptomatic carriers. When symptoms such as fever, lethargy, or poor appetite appear, supportive care may be provided. However, if your cat has a weakened immune system or is experiencing severe symptoms, treatment might be needed. 

Antibiotics are rarely needed, but in severe or persistent cases, a veterinarian may prescribe doxycycline or enrofloxacin. These treatments usually consist of four to six weeks. Monitoring the cat’s overall health and maintaining flea control are essential preventative measures. To maintain flea control, your cats can be treated with topical or oral flea prevention such as Bravecto or Revolution. 

Preventing Cat Scratch Disease

While cat scratch disease is usually mild, prevention is far easier than treatment. Simple steps such as practicing good hygiene, trimming claws, using flea control, and teaching children safe handling habits can significantly reduce the risk of transmission. These measures protect not only people, especially children and immunocompromised individuals, but also improve the overall health and comfort of cats.

Good Hygiene Practices

Practicing good hygiene is the first line of defense against cat scratch disease. Immediately washing any scratches or bites with soap and warm water can significantly reduce the risk of infection. It’s also essential to clean any surfaces or objects that a cat has scratched, as bacteria may be present on their claws. Regular handwashing after handling cats is necessary, especially before eating or touching your face. 

If a cat scratch or bite occurs, it should be washed immediately with soap and running water for at least 5 minutes. Applying an antiseptic afterward can further reduce the risk of infection. Prompt attention to scratches is significant for children, elderly individuals, and immunocompromised people, who are at higher risk for developing cat scratch disease symptoms in humans.

This also goes for your cat and not just you! Keeping a cat’s claws short and well-trimmed helps prevent deep scratches that are more likely to introduce bacteria into the skin. Regular nail maintenance also reduces the risk of accidental scratches during play or handling. Using scratching posts and teaching cats proper scratching behavior can further minimize injury.

Flea Prevention for Cats

Since fleas can carry Bartonella henselae, maintaining effective flea prevention is critical. This can include monthly topical treatments, flea collars, or oral medications prescribed by a veterinarian. Controlling fleas not only protects cats from bacteria but also reduces the risk of transmission to humans. 

Teaching Children Safe Pet Handling 

Children are at high risk for cat scratch disease. Teaching them safe ways to interact with cats can prevent scratches and bites. 

Key strategies we suggest include:

• Avoid rough play, such as wrestling or teasing.

• Do not approach unfamiliar cats or cats that show signs of irritation.

• Learn to read a cat’s body language and respect its boundaries.

• Washing hands thoroughly after touching a cat, its toys, or its bedding.

Implementing these practices can dramatically reduce the likelihood of both cat scratch disease symptoms in humans and the spread of bacteria among cats.

Conclusion 

Cat scratch disease is often mild, but its ability to cause complications, especially in children, immunocompromised people, and in the eye, makes awareness critical. While cat scratch disease symptoms in humans can range from fever and swollen lymph nodes to rare but serious eye problems like neuroretinitis, the disease is usually preventable with simple measures: washing scratches promptly, trimming cat claws, and maintaining strict flea control.

For cats, the infection is typically silent, and cat scratch disease symptoms in cats are rarely seen. When symptoms do appear, they are subtle and easily confused with other feline illnesses. This makes flea prevention, routine veterinary care, and safe play habits even more critical.

The close bond between humans and cats doesn’t need to be interrupted by fear of disease. With good hygiene, responsible pet care, and prompt medical attention when symptoms arise, both people and cats can live together safely. Recognizing the role of fleas, understanding how Bartonella spreads, and knowing the differences between cat scratch disease symptoms in humans and in cats are the keys to prevention and peace of mind.

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