Introduction
Cat scratches, especially from stray cats, are concerning because they can transmit diseases. Cats can harbor bacteria under their claws that can be transferred to humans through scratches. One of the main diseases transmitted by cat scratches is cat scratch disease (CSD), caused by the bacteria Bartonella henselae. Though most cat scratches do not lead to major illness, CSD can cause fever, headache, fatigue, and swollen lymph nodes in some people. In rare cases, cat scratches may also transmit rabies, plague, tularemia, and other serious illnesses. For these reasons, cat scratches should not be taken lightly, especially if the scratch is from a stray cat with an unknown health history.
Transmission of Diseases
Stray and feral cats can transmit diseases to humans through scratches and bites. One of the main diseases transmitted this way is cat scratch disease, which is caused by a type of bacteria called Bartonella henselae. According to the Centers for Disease Control and Prevention, around 12,000 cases of cat scratch disease are reported each year in the United States. The disease is transmitted when cats lick their claws or bite humans, transferring infected fleas and flea feces into the wound (Zoonotic Disease: What Can I Catch from My Cat?). Cat scratch disease causes swollen lymph nodes near the scratch or bite site and sometimes fever, fatigue, and loss of appetite. While cat scratch disease is usually not serious in healthy adults, it can be more dangerous for children, the elderly, and immunocompromised individuals.
Stray cats may have an increased risk of carrying certain diseases compared to owned house cats. Strays have more exposure to other cats, wildlife, and fleas or ticks carrying diseases. They are also less likely to receive regular veterinary care and preventative treatments like vaccines and deworming. Diseases stray cats may disproportionately carry include rabies, ringworm, toxoplasmosis, flea-borne typhus, and internal parasites (Outdoor cats spread diseases and harm public health). So while any cat scratch or bite can transmit disease, there is an increased risk from stray cats of unknown health status.
Cat Scratch Disease
Cat scratch disease (CSD), also known as cat scratch fever, is a bacterial infection caused by Bartonella henselae that can be transmitted from cat scratches, bites, or saliva. According to the Centers for Disease Control and Prevention (CDC), there are approximately 12,000 cases of CSD reported each year in the United States [1].
The symptoms of CSD typically appear 3-14 days after exposure and include fever, headache, poor appetite, and swollen lymph nodes near the original scratch or bite. The infected area may also appear swollen and red with round, raised lesions that can contain pus [2]. In rare cases, CSD can lead to more serious complications such as infection of the liver, spleen, joints, bones, or central nervous system if left untreated.
While most people recover fully from CSD, the swollen lymph nodes can persist for months after other symptoms subside. CSD is usually diagnosed based on symptoms and exposure history, but blood tests and cultures can also detect Bartonella henselae antibodies and bacteria [3]. Most cases of CSD can be treated effectively with antibiotics.
Other Diseases
Cat scratches can also transmit other diseases besides cat scratch disease, though the risks are generally low if the cat is domesticated and properly cared for:
Rabies – Rabies is an extremely rare disease transmitted through the saliva of infected animals. Cats can contract rabies if they are exposed to rabid wildlife like bats or foxes. Scratches from a rabid cat require immediate medical attention to prevent a fatal infection.
Plague – Cats can become infected with plague bacteria from fleas or rodents. Though rare, scratches from cats with plague may transmit the bacteria to humans, leading to bubonic or septicemic plague. Prompt antibiotic treatment is needed.
Tularemia – Also called rabbit fever, tularemia is a bacterial disease cats can pick up from rodents, rabbits or ticks. Infected cats can potentially transmit tularemia to humans via scratches. However, this is very uncommon.
Risk Factors
Certain people are at higher risk of developing an infection or illness from a stray cat scratch. According to the CDC, those at highest risk include https://www.cdc.gov/healthypets/diseases/cat-scratch.html:
- People with weakened immune systems, such as those with HIV/AIDS, those undergoing chemotherapy, or taking immunosuppressant medications.
- Young children, especially those under 5 years old.
- People with open wounds, cuts, or scratches that a cat could directly lick or scratch.
Those with compromised immune systems have a harder time fighting off infections. Young children’s immune systems are still developing. And existing open wounds provide a direct route for bacteria to enter the body. Taking precautions around stray cats is especially important for these higher risk groups to avoid potential illnesses.
Preventing Infections
There are several steps you can take to minimize the risk of infection when scratched by a stray cat:
Thoroughly clean the wound as soon as possible. The CDC recommends washing cat scratches with soap and running water for at least 5 minutes. This helps remove bacteria and decrease the risk of infection (CDC).
Apply an antibiotic ointment after cleaning the wound. Ointments like bacitracin or Neosporin can help prevent bacterial infections (Cleveland Clinic).
Get medical attention, especially if the scratch is deep or you develop any signs of infection. Your doctor can assess the wound, prescribe antibiotics if needed, and provide tips for proper wound care and monitoring for infection.
You may need a tetanus shot or rabies vaccine depending on your medical history. Your doctor can help determine if these are recommended.
In severe cases, antibiotics may be prescribed to prevent cat scratch disease, even if there are no signs of infection yet. However, antibiotics are not routinely recommended for all cat scratches (Johns Hopkins).
By thoroughly cleaning cat scratches right away, applying antibiotic ointment, and seeking medical care when appropriate, you can take steps to prevent problematic infections.
Signs of Infection
If a cat scratch becomes infected, there are some key signs to watch out for:
- Redness around the scratch site
- Swelling around the wound
- Pus or other drainage from the scratch
- Increased pain or soreness
- Fever or flu-like symptoms
- Red streaks extending from the wound
These symptoms typically show up within a few days of the initial scratch or bite. The area around the wound will become inflamed and warm to the touch as the infection takes hold. Pus and drainage indicate bacteria have entered the wound.
You should seek medical attention if any of these signs of infection appear. Left untreated, the infection can spread to the bloodstream and other areas of the body. Cat scratches near joints or over bones can be especially problematic if they become infected.
Testing and Diagnosis
If a doctor suspects cat scratch disease, there are several tests that can be done to confirm the diagnosis:
Blood tests can detect antibodies to the Bartonella henselae bacteria that causes cat scratch disease. High antibody levels indicate a current or past infection. This is considered the standard diagnostic test (https://my.clevelandclinic.org/health/diseases/23537-cat-scratch-fever).
PCR (polymerase chain reaction) tests that detect the DNA of Bartonella henselae in blood or tissue samples can also diagnose a current infection. However, these tests are not widely available (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8682836/).
If the infection has spread to the liver, spleen, or other organs, an ultrasound or CT scan can detect enlarged lymph nodes and organs. A lymph node biopsy may be done to confirm the diagnosis by growing the bacteria in a culture (https://www.aafp.org/pubs/afp/issues/2011/0115/p152.html).
Skin tests are sometimes used to assess exposure by injecting proteins from the bacteria under the skin. A reaction indicates the person’s immune system has responded to the bacteria before. However, skin tests are not completely reliable for diagnosing active infections.
Treatment
The treatment for infections or diseases resulting from cat scratches depends on the specific condition. Here is an overview of the main treatment options:
For mild cases of cat scratch disease, no treatment may be necessary as the infection often resolves on its own. Symptoms can be managed with over-the-counter medications like acetaminophen or ibuprofen. In more serious cases, antibiotics may be prescribed. According to the American Family Physician, azithromycin is commonly used to treat cat scratch disease (https://www.aafp.org/pubs/afp/issues/2011/0115/p152.html). Other antibiotics like rifampin, ciprofloxacin, gentamicin, or trimethoprim-sulfamethoxazole may also be effective.
If an abscess forms at the scratch site, it may need to be drained and cleaned out by a doctor. Antibiotics are usually prescribed after draining an abscess.
For other types of infections, appropriate antibiotics will be prescribed based on lab testing to identify the specific bacterium. Broad-spectrum antibiotics may be used initially until test results pinpoint the pathogen.
In rare cases of severe infection or complications, hospitalization may be required for intravenous antibiotics and supportive medical care.
It’s important to finish any prescribed antibiotic treatment as directed, even if symptoms improve, to fully clear the infection.
Conclusion
In summary, while the vast majority of stray cat scratches do not lead to any harmful effects, there is a small risk of developing an infection from bacteria that live on cats’ claws. The most common infection is cat scratch disease, caused by the bacterium Bartonella henselae. Less commonly, stray cat scratches can transmit rabies, plague, tularemia and other diseases. People with weakened immune systems are at higher risk of complications. To prevent infections, it’s important to wash wounds thoroughly with soap and water after a stray cat scratch. Signs of infection include redness, swelling, pain and pus at the scratch site. If these symptoms develop, promptly seek medical attention for testing and treatment with antibiotics. While stray cat scratches rarely lead to disease, it’s important to monitor all animal scratches carefully and get medical care if signs of infection appear.