Pasteurellosis is an acute zoonotic infectious disease of bacterial origin. It proceeds with the involvement of the skin, subcutaneous tissue, joints and bones. The condition is manifested by high fever, severe intoxication, damage to internal organs; cases of chronic course are described. Diagnosis of pathology is carried out mainly by bacteriological methods, serological techniques are used as auxiliary. Treatment includes etiotropic antibacterial therapy, detoxification, antipyretic and other symptomatic agents.
Pasteurellosis (hemorrhagic septicemia) refers to infections with a contact transmission mechanism. Nosology was first described in 1878. The bacterial nature of the pathogen was established in 1880 by Louis Pasteur, after whom this infectious pathology was named. Pasteurellosis is widespread everywhere, there is no clear seasonality in people, the incidence is mainly sporadic. Risk groups are agricultural workers, veterinarians, elderly people, patients with diabetes mellitus, cirrhosis of the liver, COPD, HIV infection in the AIDS stage, pathologies of the cardiovascular system and malignant neoplasms, as well as patients undergoing hemodialysis. It is believed that people aged 10-19 years are most susceptible to pasteurellosis, the disease is more often registered among women.
The causative agent of the infection is the bacterium Pasteurella multocida, which produces exotoxin. Pasteurelles are stable in the environment, they persist in water and manure for up to 2-3 weeks, and in animal corpses and frozen meat for up to 4-12 months. They die when exposed to sunlight, boiling, treatment with disinfectants. Sources of infection are bacterial carriers and sick agricultural, domestic animals and birds. Most often, pasteurellosis is registered in cattle, chickens, rabbits and buffaloes, while pasteurellosis is observed in 80% of cats, 70% of cows, 50% of sheep and rabbits, 45% of sheep, 35% of chickens in dysfunctional farms. Pasteurels are excreted with feces, urine, nasal discharge, blood, milk of an animal, human infection usually occurs when cats and dogs bite and scratch the skin. Airborne and transplacental pathways of infection are described; the possibility of transmissible transmission of pasteurellosis by bites of infected horseflies is assumed.
When bacteria enter through damaged skin and mucous membranes, a primary focus of inflammation is formed. The active reproduction of pasteurella, the release of exotoxin and microbial waste products provoke the accumulation of immunocompetent cells, the development of purulent process, thrombosis of small vessels, edema. The penetration of infectious agents deep into the dermis and underlying tissues leads to the spread of the process to bones and joints, the occurrence of arthritis and osteomyelitis. Hematogenic dissemination of pasteurella is observed when the walls of blood vessels are involved and pathogens enter the systemic circulation. If a large amount of exotoxin, decay products of bacteria and immune cells enter the bloodstream, an infectious and toxic shock may develop. In the internal organs, pasteurels continue to multiply actively, disrupting the structure of cells and tissues, which leads to critical functional disorders.
Pasteurellosis is acute or chronic. Usually, the changes are localized within the entrance gate of the infection or take the form of a sluggish inflammatory purulent process. Hematogenic spread of the pathogen is possible only when the body’s defenses are depleted. The classification is based on the degree of invasiveness of pathology:
- Skin form. The most common type of disease. It is a purulent lesion of the skin at the site of a bite, salivation or scratch, other damage to the skin left by a sick animal, with a tendency to spread deep into the underlying tissues.
- Pulmonary form. With the aerogenic mechanism of infection, it can occur primarily, but more often it is a consequence of hematogenic dissemination of the pathogen. The clinical picture is caused by inflammation of the bronchial wall, damage to the alveolar tree and connective tissue.
- Septic form. A life-threatening condition in which an organism is contaminated with massive bacteremia. Dysfunctional changes develop in the affected organs up to the complete cessation of activity.
The incubation period is 1-5 days. The disease begins acutely with a rise in body temperature to 38-38.5 ° C and above, chills, weakness. In the area of damage, puffiness, hyperemia, soreness are detected, pustules with purulent contents are formed, after opening which crusts are formed. An increase in regional lymph nodes is detected. With the spread of the purulent process, there is inflammation of subcutaneous tissue, muscles, bones, joints, the appearance of soft tissue abscess and extensive phlegmon. Pulmonary manifestations are possible – cough with purulent sputum, chest pain, moderate shortness of breath.
With insufficient immune resource of the body, the pathogen spreads through the body with the formation of visceral purulent foci. Fever intensifies, acquires a wave-like character. Signs of intoxication are increasing, severe headache, disturbances or changes in consciousness are noted, convulsions and paralysis are possible. Shock often occurs, accompanied by a sharp decrease in blood pressure, loss of consciousness, lack of urination, sometimes spontaneous bleeding.
The most common complications of pasteurellosis are purulent lesions of the skin, muscles, subcutaneous tissue (abscesses, phlegmons), joints and tendon-ligamentous apparatus (bursitis, tendovaginitis, arthritis), bone structures (osteomyelitis). Chronic bronchiectasis leads to amyloidosis of internal organs. Septicopyemia with the formation of purulent foci in various organs, thrombohemorrhagic manifestations, infectious and toxic shock is possible. Isolated cases of fulminant purpura with high mortality have been described. In the outcome of purulent arthritis (especially knee joint lesions), there is often a violation of function that causes the need for endoprosthetics.
The diagnosis is made by an infectious disease specialist. Depending on the existing symptoms, consultations with a therapist, a dermatovenerologist, or a surgeon may be required. If the respiratory tract is affected, an examination by a pulmonologist, a phthisiologist is necessary, and in the presence of life–threatening conditions, a resuscitator. The list of diagnostic measures includes the following objective, laboratory and instrumental methods:
- Physical examination. In the lesion with the cutaneous form, a site of hyperemia, sharp soreness, swelling of the skin, a pustule with cloudy contents, a scab is found, fluctuation is often determined. When the joints are affected, there is an increase in their size, restriction of movements, forced position of the limb. Interstitial pneumonia during auscultation is manifested by hard breathing, crepitation, shortening of the percussion sound. With bronchiectasis, there is a diffuse weakening of pulmonary respiration with an abundance of moist wheezing, which decreases with coughing.
- Laboratory tests. In a general blood test with pasteurellosis, leukocytosis with a rod–shaped shift to the left, an increase in ESR, often thrombocytopenia, anemia are detected. Changes in biochemical parameters include an increase in ALT, AST, total bilirubin, CRP, urea, creatinine, a decrease in total protein, disorders of the coagulation system. General clinical examination of urine confirms an increase in density, microhematuria, leukocyturia, less often pyuria. Neutrophil pleocytosis, cell-protein dissociation is detected in the cerebrospinal fluid in paterellosis meningoencephalitis.
- Identification of infectious agents. The main technique is PCR. Bacteriological methods of culture media seeding are used with any biological material obtained from the patient (separated skin ulcers, blood, cerebrospinal fluid, abscess punctate), including sectional. ELISA and other serological techniques are necessary for the retrospective diagnosis of pasteurellosis, since they require the study of paired sera with an interval of at least 14 days to detect the growth of antibody titer.
- Radiation diagnostics. In case of respiratory tract lesions, chest radiography is prescribed. Ultrasound of soft tissues, joints, and bone structures is often performed in order to detect purulent processes in a timely manner. Ultrasound of the abdominal cavity, kidneys, and pelvis is used to visualize septicopyemic foci in the area of internal organs. MRI and CT scans of the brain are used for symptoms of CNS damage, especially in immunodeficient individuals.
Differential diagnosis is carried out with infectious diseases: anthrax, cutaneous and visceral leishmaniasis, erysipeloid. In addition, the symptoms of pasteurellosis are similar to the clinic of listeriosis, toxoplasmosis, erysipelas. Generalized lesions are possible with tuberculosis, organ mycoses and syphilis, can be observed with tularemia, cytomegalovirus, pneumococcal infection. Sepsis can be caused by staphylococci, streptococci, cocciella. In some cases, differentiation with obliterating endarteritis, trophic ulcers, bacterial purulent lesions is required. Somatic diseases similar to pasteurellosis are bronchiectatic disease, malignant neoplasms of the central nervous system, hemorrhagic strokes. Sometimes it is necessary to exclude skin diseases: staphyloderma, psoriasis, eczema.
Patients with hemorrhagic septicemia are indicated for inpatient treatment, especially if they belong to a risk group. Bed rest is observed for up to 3-4 days with a stable normal body temperature. The diet involves limiting hard-to-digest food, abstaining from alcohol. It is mandatory to increase the amount of liquid consumed for the purpose of oral detoxification. If there are signs of arthritis, it is recommended to apply bandages, orthoses, fixing bandages using an elastic bandage.
Etiotropic treatment includes antibacterial agents. The most effective drugs are penicillins (ampicillin + sulbactam, amoxicillin + clavulanic acid), cephalosporins of the 2nd and 3rd generation, tetracyclines, fluoroquinolones, co-trimoxazole. In patients suffering from pasteurellosis infection due to contamination of the dialysis catheter, cases of relapse have been recorded during the course of monotherapy with aminoglycosides, therefore their use as the only treatment is doubtful.
The treatment plan for pasteurellosis may also involve infusion of solutions to reduce the severity of intoxication syndrome (glucose-salt, succinate-containing solutions, acesol), taking antipyretic and analgesic drugs. Surgical treatment is indicated when limited or diffuse purulent processes occur. Usually, an autopsy and drainage of purulent foci is performed. With severe lesions, amputation of the limb is required.
Prognosis and prevention
The prognosis for uncomplicated pasteurellosis and uncomplicated premorbid background is favorable. According to studies, about 70% of cases of septic course of the disease were observed in people over 50 years old and only in 21% of cases – in patients 20-50 years old. Mortality in animals reaches 80%, in humans – 1.79%. The average duration of the disease is 8 days. In the presence of purulent lesions of joints and bone structures, long–term rehabilitation is possible (more than 1-2 months), in case of amputation of a limb – disability.
Specific prevention exists in the form of vaccines and hyperimmune serum for animals; vaccine preparations for humans have not been developed. Measures of non-specific prevention include strict veterinary control, isolation of sick animals, a ban on the sale of milk and meat from foci of pasteurellosis. It is necessary to use personal protective equipment (masks, shields, gloves) when working with animals, treat bites, scratches with antiseptic agents, thoroughly wash hands with soap after contact with animals.