Pasteurellosis
Synonyms and keywords: Shipping fever; bovine respiratory disease complex; fibrinous pneumonia; Pasteurella pneumonia; hemorrhagic septicemia; fowl cholera; snuffles

# Overview
Pasteurellosis is an infection with a species of the bacterial genus Pasteurella. Pasteurella multocida (subsp. septica and subsp. multocida) is carried in the mouth and respiratory tract of various animals, including cats and dogs. It is a small Gram negative bacillus with bipolar staining on Wayson stain. Pasteurella is usually transmitted via the cutaneous route to the human host.Pasteurella uses a number of mechanisms for avoiding or suppressing bactericidal responses such as lipopolysaccharides (LPS) and the bacterias capsule. It is difficult to establish the true prevalence and incidence of pasteurellosis because disease reporting is not required. In the USA, the annual incidence of dog and cat bites has been reported as 300 bites per 100,000 individuals. The most important risk factor in the development of pasteurellosis is animal exposure. Individuals with high risk of developing pasteurellosis are children and inmunosuppressed individuals. If left untreated, patients with pasteurellosis may progress to develop soft tissue inflammation. Complications of pasteurellosis include cellulitis, pneumonia, and bacteremia. Patients with cutaneous infection have the most favorable prognosis when adequately treated. Physical examination of patients with pasteurellosis is usually remarkable for erythema, warmth, swelling and pain in the affected area. The mainstay of therapy for pasteurellosis includes both cleaning the wound and antibiotic pharmacotherapy using a combination of penicillin and beta-lactamase inhibitors.

# Historical Perspective
- The genus Pasteurella is named after the French chemist and microbiologist, Louis Pasteur, who first identified the bacteria now known as Pasteurella multocida as the agent of chicken cholera.

# Pathophysiology

## Transmission
- Pasteurellosis is usually transmitted by close contact with pets, including sharing a bed, being licked by pets, kissing pets, animal scratches, or bites.
- Less commonly, pasteurellosis can be acquired by inhaling the bacteria, human-to human transmission or with unknown source of infection.
- Pasteurella can be transmitted when exposed to animals that have been exposed directly or indirectly to the animal oropharyngeal secretions through licking or sniffing.

## Pathogenesis
- The mechanisms of pathogenesis of Pasteurella infection in its natural host species and in humans are still not completely understood, and further studies are needed.
- Pasteurella is usually transmitted via the cutaneous route to the human host.
- Pasteurella uses a number of mechanisms for avoiding or suppressing bactericidal responses:
Lipopolysaccharides (LPS) and the bacterias capsule probably play a substantial role in intracellular survival
P. multocida capsule has been shown in strains belonging to serogroups A and B to help resist phagocytosis by host immune cells and capsule type A has also been shown to help resist complement-mediated lysis
The LPS produced by P. multocida consists of a hydrophobic lipid A molecule (that anchors the LPS to the outer membrane), an inner core, and an outer core, both consisting of a series of sugars linked in a specific way
Formation of stress fibers may aid in the endocytosis of P. multocida
The host cell cycle is modulated by the P. multocida toxin, which can act as an intracellularmitogen
- Lipopolysaccharides (LPS) and the bacterias capsule probably play a substantial role in intracellular survival
- P. multocida capsule has been shown in strains belonging to serogroups A and B to help resist phagocytosis by host immune cells and capsule type A has also been shown to help resist complement-mediated lysis
- The LPS produced by P. multocida consists of a hydrophobic lipid A molecule (that anchors the LPS to the outer membrane), an inner core, and an outer core, both consisting of a series of sugars linked in a specific way
- Formation of stress fibers may aid in the endocytosis of P. multocida
- The host cell cycle is modulated by the P. multocida toxin, which can act as an intracellularmitogen
- Pasteurella needs iron to grow.
P. multocida has developed mechanisms acquire iron from hemoglobin, ferritin, lactoferrin and transferrin.
- P. multocida has developed mechanisms acquire iron from hemoglobin, ferritin, lactoferrin and transferrin.

# Causes
- Pasteurellosis is caused by an infection with Pasteurella spp.
- Pasteurella is a Gram-negative, facultatively anaerobic bacteria.
- Most Pasteurella species are catalase-positive and oxidase-positive.
- Most common species that cause pasteurellosis in humans is P. multocida.
- Pasteurella is part of the normal cavity flora of many animals such as cats, dogs and frequently rabbits.
Cats oral cavity colonization of P. multocida is between 70%90%
Dogs oral cavity colonization of P. multocida is between 50%60%
- Cats oral cavity colonization of P. multocida is between 70%90%
- Dogs oral cavity colonization of P. multocida is between 50%60%

# Differentiating Pasteurellosis from other Diseases
Pasteurellosis must be differentiated from:
- Cat scratch disease
- Abscesses:
Abdominal
Brain
Liver
Lung
Perinephric
Due tu amebas, streptococcus, staphylococcus, and anaerobic bacteria
- Abdominal
- Brain
- Liver
- Lung
- Perinephric
- Due tu amebas, streptococcus, staphylococcus, and anaerobic bacteria
- Cellulitis
- Animal Bites
- Pneumonia:
Bacterial
Comminuty-adquired
- Bacterial
- Comminuty-adquired
- Abdominal sepsis
- Haemophilus spp. infections
- Actinobacillus actinomycetemcomitans infection
- Cardiobacterium hominis infection
- Eikenella corrodens infection
- Kingella spp infection
- Peritonitis
- Meningitis

# Epidemiology and Demographics
- It is difficult to establish the true prevalence and incidence of pasteurellosis because disease reporting is not required
- P. multocida oral cavity colonization in cats, dogs and other animals is common worldwide
- An estimated 4.4 million animal bites occur each year in the United States
- In the USA, the annual incidence of dog and cat bites has been reported as 300 bites per 100,000 individuals
- The case mortality rate of pasteurellosis is approximately 25-30%
- The case mortality rate of pasteurellosis patients with meningitis and neurological manifestations is approximately 17-29%
- The case mortality rate of pasteurellosis patients with bacteremia is approximately 40-63%

# Risk Factors
- Animal exposure
- Children: Among children, the rate of dog bite related injuries is highest for those 5 to 9 years old
- Men: Men are more likely than women to be bitten by a dog
- Elderly
- Pregnant women
- Immunosuppressed individuals

# Natural History, Complications and Prognosis

## Natural History
- Pasteurellosis incubation period occurs within 24 hours.
- Initial presentation usually shows as soft tissue inflammation.
- If left untreated, patients with pasteurellosis progress to develop complications.

## Complications
- Pasteurellosis complications include:
Cellulitis
Subcutaneous abscesses
Septic arthritis
Lower respiratory tract infections
Upper respiratory tract infections
Osteomyelitis
Bacteremia
Endocarditis
Meningitis
Peritonitis
- Cellulitis
- Subcutaneous abscesses
- Septic arthritis
- Lower respiratory tract infections
- Upper respiratory tract infections
- Osteomyelitis
- Bacteremia
- Endocarditis
- Meningitis
- Peritonitis

## Prognosis
- The prognosis varies with the type of infection; cutaneous infections have the most favorable prognosis with adequate treatment.
- Prognosis is generally poor for patients who develop bacteremia, endocarditis and meningitis.

# History and Symptoms

## History
- Patients with pasteurellosis most commonly report contact with pets, including sharing a bed, being licked by, or kissing the pets

## Symptoms

### Symptoms related to cellulitis (most common) include:
- Fever
- Pain or tenderness in the affected area
- Skin redness or inflammation that gets bigger as the infection spreads
- Skin sore or rash that starts suddenly, and grows quickly in the first 24 hours
- Tight, glossy, "stretched" appearance of the skin
- Warm skin in the the area of redness

### Symptoms related to pneumonia include:
- Dyspnea
- Productive cough (greenish or yellow sputum)
- Fever (high grade) with sweating, chills, and rigor
- Pleuritic chest pain
- Rapid, shallow breathing
- Shortness of breath

### Symptoms related to septicaemia include:
- High fever
- Rigor
- Vomit

# Physical Examination

## Physical examination related to cellulitis (most common) include:

### Skin
- Redness, warmth, and swelling
- Possible drainage, if there is an infection
- Swollen lymph nodes near the affected area

## Physical examination related to pneumonia include:

### Vital Signs
- Decreased oxygen saturation
- Fever
- Hypotension < 90 mm Hg
- Tachycardia > 125 beats/min
- Tachypnea

### Lungs
- Palpation
Increased tactile fremitus
- Increased tactile fremitus
- Percussion
Dullness on percussion
- Dullness on percussion
- Auscultation
Decreased breath sounds
Bronchial breath sounds
Rhonchi
Crackles, Rales
Increased vocal fremitus
- Decreased breath sounds
- Bronchial breath sounds
- Rhonchi
- Crackles, Rales
- Increased vocal fremitus

## Physical examination related to septicaemia include:

### Vital Signs
- Hypotension
- Sepsis is considered present if infection is highly suspected or proven and two or more of the following systemic inflammatory response syndrome (SIRS) criteria are met:
Heart rate > 90 beats per minute
Temperature  38 C (100.4 F)
Tachypnea > 20 breaths per minute or, on blood gas, a PaCO2 < 32 mm Hg
- Heart rate > 90 beats per minute
- Temperature  38 C (100.4 F)
- Tachypnea > 20 breaths per minute or, on blood gas, a PaCO2 < 32 mm Hg

### Skin
- Cyanosis
- Throat
- Lymphadenopathy

### Extremities
- Decreased peripheral pulses

### Neurologic
- Altered sensorium, lethargy, and coma.

# Diagnosis
- Diagnosis is made with isolation of Pasteurella multocida in a normally sterile site (blood, pus or cerebrospinal fluid)
- P. multocida  has been observed invading and replicating inside host amoebae, causing lysis in the host. P. multocida  will grow at 37 C on blood or chocolate agar
Colony growth is accompanied by a characteristic "mousy" odor due to metabolic products
- Colony growth is accompanied by a characteristic "mousy" odor due to metabolic products
- Being a facultative anaerobe, it is oxidase-positive and catalase-positive, and can also ferment a large number carbohydrates in anaerobic conditions

# Treatment
- As the infection is usually transmitted into humans through animal bites, cleaning the wound and antibiotics usually treat the infection
- Pasteurellosis is usually treated with penicillin AND beta lactamase inhibitor
- Patients with penicillin allergies or resistant to beta lactamase inhibitor should be treated with doxycycline, levofloxacin or moxifloxacin
- Therapy for patients with cellulitis infection last approximately 10 days
- Therapy for patients with tenosynovitis infection last approximately 3 weeks
- Therapy for patients with septic arthritis infection last approximately 4 weeks
- Therapy for patients with osteomyelitis infection last approximately 6 weeks

# Prevention

### Preventing dog and cat bites
- Do:
Remain motionless (e.g., "be still like a tree") when approached by an unfamiliar dog or cat
Curl into a ball with your head tucked and your hands over your ears and neck if a dog knocks you over
- Remain motionless (e.g., "be still like a tree") when approached by an unfamiliar dog or cat
- Curl into a ball with your head tucked and your hands over your ears and neck if a dog knocks you over
- Don't:
Approach an unfamiliar dog or cat
Run from a dog or car
Panic or make loud noises
Disturb a dog or cat that is sleeping, eating, or caring for puppies
Pet a dog without allowing it to see and sniff you first
Encourage your dog to play aggressively
Let small children play with a dog or cat unsupervised
- Approach an unfamiliar dog or cat
- Run from a dog or car
- Panic or make loud noises
- Disturb a dog or cat that is sleeping, eating, or caring for puppies
- Pet a dog without allowing it to see and sniff you first
- Encourage your dog to play aggressively
- Let small children play with a dog or cat unsupervised
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