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Cat Scratch Disease

Cat scratch disease (CSD), also called Cat Scratch Fever, is a bacterial infection passed on to people from cats that are infected with Bartonella henselae bacteria, one of the most common bacteria in the world. The Bartonella genus encompasses at least 11 species out of which 4 cause infections in human. They are responsbile for diseases such as bacillary Angiomatosis.

When the cat infected with Bartonella henselae bacteria scratches or bites the person or saliva of an infected cat enters an open sore or wound of the person, the bacteria gets transmitted causing cat scratch disease. Cats are believed to contract these bacteria from infected fleas and nearly 40 percent of cats carry the bacteria at some time in their life span. When compared to adult cats, kittens are more prone to carry the bacteria and transmit the disease. Cat's sharp teeth result in deep puncture wounds which can get serious infections if left untreated.


The first symptoms of cat scratch disease surface after three to 14 days of coming into contact with the infected cat. Cat scratch disease can cause serious symptoms in people with impaired immune system such as cancer patients and HIV patients. The infection may be fatal and lead to inflammation of brain, spleen, liver, lungs, and bone marrow. Hence such cases require immediate medical attention and early treatment in case of suspicion.

  • Papular lesion of the skin, at the site of the injury
  • Swelling of lymph nodes near the bite. Most often lymph nodes located under arms, groin or neck are affected.
  • Tired feeling
  • Headaches
  • Low-grade fever
  • Loss of appetite
  • Weight loss


It is difficult to establish the diagnosis of cat scratch disease as causative bacteria cannot be easily cultured from human lymph node samples. Therefore diagnosis is done based on the history of contact with a cat and the presence of a scratch or primary lesion of the skin, eye or mucous membrane. Serological test and epidemiological, histological findings are taken into consideration before conforming the diagnosis.


Cat scratch disease is self limiting and usually regresses over few weeks. The condition does not require antibiotic treatment unless the patient is suffering from weakened immune system. Analgesics along with local heat application are recommended to relieve the pain of enlarged lymph nodes.


Cat scratch disease is not contagious from person to person. The bacteria is transmitted only by the scratch or bite of an infected cat, most often kitten. Keep your pet cats free of fleas. Avoid rough play with the cats. Scratches from cat, if any, should be washed immediately and cats should not be allowed to lick open wounds.

Cat Behavior

Cats are solitary predators unlike dogs which are pack or herd animals.In consequence, Cats don't treat humans as authority figures in the same manner the dogs do. A cat's visual cortex contains more neurons than the equivalent area of a human brain. Typically a cat's brain weighs about 30 gm which is just under 1 percent of its total body weight. Compare this to a human brain which is 2 % of the body weight or to a dog which is 1.2 %. However, the cortex of the cat's brain has high Cortical folding which significantly increases the amount of the cerebral cortex. As a result, a cat has a well developed area of the brain responsible for interpreting sensory information. It can use its paws almost like humans. Cat's night vision is exceptional and their binocular vision is attuned to see in depth and to judge distances accurately. Their night vision is further enhanced by a layer behind the retina called as tapetum lucidum which is the reason why a cat's eyes shine bright golden or green disk when struck by a light. Their eyes detect motion better than actual sharp details. With large eyes it takes more time to focus sharp.

Most cat bites occur because of fear on the cat’s part or a phenomenon known as petting-induced aggression. Petting induced aggression is a behavior in which a cat - usually younger cats that has been apparently enjoying contact with a human suddenly turns on the human and bites. In elderly cats, the aggression may have been induced by pain due to pressure on arthritic joints.

Inflammation is probably the most common sign of infection from an animal bite. The skin around the wound may turn red and warm and over a period of time the wound may exude pus. Nearby lymph glands may become swollen. If not treated in time, complications may arise when the infection spreads deep or to the blood stream. Live disease causing bacteria within the bloodstream or in the tissues may cause major complications further away from the wound site. Such complications include meningitis, brain abscesses, pneumonia, lung abscesses and heart infections which can be fatal at times.

Cat scratch disease is caused by Bartonella Henselae), previously known as Rochalimaeaquintana, a type of bacteria in cat saliva. Infection may occur with a bite or a scratch. As per CDC, in USA alone there are 22000 reported cases. The Cat scratch disease is not normally severe in people with healthy immune systems. However, it can become sever in immunocompromised individuals - acquired immune deficiency syndrome (AIDS) or those undergoing chemotherapy.

Prevention: Cat bites can easily be avoided by learning about a cat’s body language and recognizing the signs of impending aggression. Look out for signs such as:

  • dilating pupils
  • a low growl
  • stiffening of the body
  • wagging/flicking tail - increasing frequency denotes increasing anger
  • twitching of the tail
  • flattening the ears backward against the head
Cat scratch disease

Warning Stance: When a cat stands with his rump raised or back arched, it feels threatened and it is a warning that it is about to strike/attack. Sometimes the hair on its body may also be raised. A cat's tail is probably the most significant signal:

Tail SignalInterpretation
Flicking from side to sideIrritated
Curved like an “N” or low to the ground and flickingFeeling aggressive
Strong lashing movementsDon't mess with me! Will attack at the first chance
Arched over the backAll right! I am going to attack now. You asked for it
Hair fluffed out and standing on end OH ! I am anxious and threatened now
Horizontal or slightly low to the floor All is well
Erect or with a curl at the tipI feel friendly now. How are you doing ?
Pointing straight up and vibrating Quivering with joy and excitement
Tucked between the legsI am submissive now. Please don't hurt me

A healthy cat tends to be friendly. An ailing cat can be aggressive or scratch you unintentionally.
Vital signs of Cats

  • body temperature : 100.5 - 102.5°F (38 - 39°C).
  • Pulse rate: 110 - 180 beats per minute
  • Respirations : 20 - 30 per minute
  • Time for gum to regain pink color after being blanched by gentle pressure with finger(Capillary refill time): < 2 seconds

Erythema Nodosum

Inflammation of the skin that shows up as painful reddish tender lumps is called Erythema nodosum. This inflammation is usually located in a part of the fatty layer of skin (subcutaneous fat). The size of the lump could vary in size from 1 to 5 cm. The inflammation causes nodular swelling. The inflammation remains for about a week and then becomes flat leaving behind a bruised appearance. They usually show up on the shins (front portion of the legs, just below the knee). Erythema nodosum is a type of panniculitis, i.e. inflammation that can cause nodules below the surface of the skin. The condition is more common among youngsters aged between 12-20 years.

Erythema nodosum settles down on its own after a period of three to six weeks. It may leave behind a temporary bruised appearance or a chronic indentation in the part where the fatty layer has been injured. Though the condition is annoying and painful, the condition does not cause any damage to the internal organs of our body. In adults, the condition is more often seen in women than in men. In kids, it affects boys and girls equally. In a few people the trigger can be identified and in yet a few it cannot be identified. However identifying the trigger becomes very important as it needs to be treated.

Erythema nodosum causes

Erythema nodosum may show up on its own or may occur in association with other conditions. In about 30-50% of cases, the cause is unknown. However the common triggers that may cause Erythema nodosum include:

Erythema nodosum symptoms

  • Painful nodules are commonly seen on the shin and sometimes on the arms, thighs and trunk of the body. The nodule when it first appears is red, hot and firm to touch and becomes flat over a few days. It appears as bruise that is blue in color and later turns yellowish as it fades. A person may develop just a couple of nodules or much more.
  • Flu-like feeling before the appearance of lumps.
  • Aching joints and legs before the appearance of lumps. Ankle, knee and wrist joints are the most affected.
  • Loss of weight.
  • Symptoms may vary depending on the underlying trigger that caused the condition.

Erythema nodosum diagnosis

  • By means of physical examination
  • Biopsy of the affected area
  • Blood test to identify the trigger
  • Chest X-ray in case of TB or sarcoidosis induced condition
  • Throat swab

Erythema nodosum treatment

  • Cortisone injection
  • Oral cortisone
  • Anti-inflammatory drugs
  • Bed rest
  • Compression bandages
  • Cool wet compresses

Tags: #Cat Scratch Disease #Cat Behavior #Erythema Nodosum
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Collection of Pages - Last revised Date: May 25, 2024