Cat Scratch Disease(CSD) or Bartonellosis in Cats : An Emerging Bacterial Zoonosis of Public Health Significance
Cat Scratch Fever in Cats
Bartonellosis or Cat Scratch Disease (CSD) is defined as an infectious, benign illness that in most cases results from the scratching, licking or biting of animals carrying the bacterium Bartonella henselae. This is a zoonotic disease, meaning that it can be transmitted between animals and humans. In cats, the disease is generally transmitted through contact with flea feces. The bacterium is excreted through the flea and into its feces, which it leaves on the cat’s skin. The cat, through grooming itself, ingests the bacteria, thereby becoming infected with the Bartonella strain. Humans do not acquire this infection from flea reservoirs. It is important to note that this bacterial infection can also be transmitted to humans and cats by ticks.
Although cats generally do not suffer from the infection, beyond possible fever, swollen glands, and some muscle aches, cat scratch fever can be passed to a human host when the infected cat scratches or bites a human. Saliva can also be a conduit for transmission, such as when an infected cat licks a skin abrasion or open wound on a human.
What is Bartonellosis?
Bartonellosis is a group of diseases caused by species of the genus Bartonella and is primarily associated with fleas and lice. However, studies have found that certain Bartonella species are carried by the same ticks that carry Lyme disease, and ticks are likely the chief source of human bartonellosis infection. Therefore, Bartonellosis can be seen as an emerging tick-borne infection.
How is Bartonellosis transmitted?
Cat scratch disease, is most often transmitted to humans from a bite or scratch of an infected cat. Cats contract B. henselae from the bite or droppings of cat fleas. Cat fleas are thought to amplify the B. henselae reservoir and not directly transmit the disease to humans. In recent years it has been believed that B. henselae may also be a tick-borne pathogen and can be present in the same Ixodes ticks that transmit pathogens causing Lyme disease, Tick-Borne Relapsing Fever, Babesiosis, and Ehrlichiosis.[4] Trench fever, caused by B. quintana, is transmitted from cats to humans and from humans to humans by the body louse, Pediculus humanus humanus.[5] Carrion’s disease, caused by B. bacilliformis, is transmitted to humans through the bite of the female sand fly, Lutzomyia verrucarum. The disease presents in two distinct phases, with the bacteria invading the erythrocytes during the acute phase and the endothelial cells during the chronic phase.[6] Recently, scientists have determined the transmission of Bartonella to mice via ticks.
The animals listed in the table below can harbor infected fleas or ticks that carry Bartonella. The disease occurs most frequently in children under 15 years.
| Species of Bartonella | Reservoir | Vector |
| B. henselae | Cat | Flea and Tick |
| B. quintana | Human/ cat | Louse |
| B. elizabethae | Rat | Flea |
| B. washoensis | Ground squirrel | Flea |
| B. vinsonii arup | Mice | Tick |
| B. vinsonii berk | Cat | Tick |
| B. koehlare | Cat | Flea |
| B. alsatica | Rabbit | Scratch |
| B. bacilliformis | Human | Sand Flies |
What are the symptoms of Bartonellosis?
The symptoms of Bartonella can vary from mild to severe, and usually begin 5 to 14 days after infection. Common symptoms include fever, headaches, fatigue, poor appetite, brain fog, muscle pain, and swollen glands around the head, neck, and arms.
Symptoms specific to CSD comprise enlarged lymph nodes, a papule or pustule at the inoculation site, and on the rare occasion, complications affecting the brain, eye disorders, severe muscle pain, hepatosplenic infection, osteomyelitis, and encephalitis. These rare manifestations are more common in children younger than five years due to their weakened immune systems. Infection by B. quintana, the causative agent of Trench fever, specifically includes symptoms of skin rashes, recurrent fevers, and rarely, heart failure. In immunocompromised patients such as those with HIV, the potentially fatal disease bacillary angiomatosis, caused by B. henselae or B. quintana, can occur. The symptoms of Carrion’s disease, caused by B. bacilliformis, present in two distinct phases: Oroya fever and Verruga peruana (Peruvian warts). Oroya fever is very similar to malaria, characterized by high fever, sweating, headaches, chills, and weakness. Whereas, Verruga peruana develops in the second stage of Carrion’s disease and is characterized by reddish, purple skin lesions.
Some other symptoms of Bartonellosis include photophobia, tachycardia, bowel problems, OCD behavior, anxiety, rapid relapse off of antibiotics, psychiatric problems, pain behind the eyes, and no response to previous antibiotic treatments.
How is Bartonellosis Diagnosed?
The diagnosis of Bartonellosis, should be considered in patients bitten by a tick or flea or scratched by small animals and are experiencing any of the symptoms typical of Bartonella infections, even mild ones. Cases of CSD can usually be diagnosed via the patient’s symptoms and history. However, laboratory tests such as IFAs (Indirect Immunoflurescent Assay), Western Blots, PCRs (Polymerase Chain Reaction), and FISH (Fluorescent In-Situ Hybridization) tests are important to confirm the diagnosis
The Human Disease
Infection with Bartonella henselae in an immunocompetent person (i.e. a normal, healthy person) person leads to cat scratch disease. The inoculation site, a scratch from a claw containing bits of flea dirt, develops a small red bump called a papule. About 2 to 3 weeks following contact with the infected cat, the lymph node in the area will swell and become painful, and a fever will develop. These signs generally resolve on their own and the condition is minor though lymph node enlargement can persist for several months.
If the patient does not have a competent immune system (in other words, they are very old, very young, debilitated from another condition, etc.), one of several far more serious syndromes can result. The infection goes deeper into the body and causes spleen enlargement, and potentially encephalitis, heart valve infection, and other conditions. These syndromes are rare, but they are potentially quite serious.
Treatment for Cats
An assortment of antibiotics have been used against Bartonella henselae in cats: clavulanic acid-amoxicillin combination, azithromycin, doxycycline, and quinolone class medications (enrofloxacin, marbofloxacin, etc). Efficacy has been mixed and Bartonella henselae rapidly becomes resistant to therapy. Treatment is currently recommended for cats showing symptoms of disease or for cats living with immune-compromised individuals. Treatment lasts a minimum of three weeks.
Preventing Human Infection of Bartonella: Guidelines from the Centers for Disease Control and Prevention
Guidelines for Prevention of Human Infection
The following guidelines have been published by both the CDC and the European Advisory Board on Cat Diseases:
- Immune-suppressed people should adopt only apparently healthy cats less than 1 year of age.
- Immune-suppressed people should not adopt from the shelter or from multi-cat homes.
- Cats belonging to immune-compromised people should be kept indoors only and should not have contact with cats that go outdoors.
- Claws should be kept trimmed.
- Cat scratches should be promptly washed. (This goes for everyone, not just immune-compromised people.)
- Flea control should be strict.
Preventing Disease
No data support chemoprophylaxis (i.e. preventive drug treatment) for Bartonella-associated disease. In simpler terms, if a suspicious cat scratch has occurred, there is no point in using medication to prevent infection.
EDITED BY-DR. ROHIT RAJ, CANINE CONSULTANT,KOLKATA
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