**Abstract**

Swine pasteurellosis is usually observed in descript as well as nondescript pigs imparting in huge economic losses to the pig producers. The disease is characterized by pyrexia, dullness, staggering gait, anorexia, serous nasal discharge and dyspnoea. Case fatality rate may as high as 95% in adult animals and 100% in piglets. Typical lesions of oedematous swellings may remarkably visible in the pharyngeal region, these swellings spread to the ventral cervical region and brisket of pigs. Gross lesions include severe pneumonia and haemorrhages in lungs, petechial haemorrhages on serous membranes and other visceral organs. Lymph nodes usually get enlarged, oedematous and haemorrhagic. The blood smears from heart blood and tissue impression smears reveal teaming numbers of bipolar organisms indicating the presence of *Pasteurella* spp., the etiological organism. The bacteriological isolation and characterization of causative agent should be ruled out to identify by Gram' staining for purity and bipolar morphology and biochemical characterization of the organisms. Molecular characterization necessitates to confirm *Pasteurella multocida* along with capsular types of the organism. Histopathological examination of lungs usually reveals typical fibrinous bronchopneumonia, multifocal suppuration and pleural thickening. Heart of some pigs may show presence of thrombi, haemorrhages and necrosed myocardium.

**Keywords:** Swine Pasteurellosis, *Pasteurella multocida*, Haemorrhagic septicaemia, capsular types, fibrinous bronchopneumonia

## **1. Introduction**

*Pasteurella multocida* is of substantial economic significance in the livestock industry [1]. Infections by *Pasteurella multocida* have been reported in all the animals and fowls [2]. It is an important principal animal pathogen for over a century and is becoming crucial as human pathogen [3] leading to a disease process termed Pasteurellosis. *Pasteurella multocida* B:2, which causes haemorrhagic septicaemia (HS) of ruminants, is believed to enter the host via respiratory and oral routes. While the role of respiratory route of infection has been established, *Pasteurella multocida* is one of the most fascinating Gram-negative bacteria and is a commensal of the upper respiratory tract of many animal species as the

organism is also a primary or secondary pathogen and responsible for a wide range of economically important diseases in domesticated animals throughout the world. Pasteurellosis is an infection of cattle, buffalo, swine and other species of animals caused by Gram-negative coccobacillary bipolar organism, *Pasteurella multocida*. It is OIE list B disease of ruminants in the tropical countries. *Pasteurella multocida* strains express a polysaccharide capsule on their cell surfaces and the antigenic specificity of the capsule determines the serogroups: A, B, D, E or F [4]. It has long been recognized that there is relationship exist between the capsular type and disease predilection [5], which suggests that the capsular polysaccharide type plays a role in host and disease specificity. For example, the majority of cases of fowl cholera are caused by capsular type A strains. Progressive atrophic rhinitis (PAR) of pigs is associated predominantly with capsular type D isolates, bovine and porcine pneumonia are associated mainly with capsular type A strains and haemorrhagic septicaemia of cattle and water buffaloes is caused exclusively by capsular type B and E isolates [6].

Capsular types A and D cause economic losses in swine because of their association with progressive atrophic rhinitis and enzootic pneumonia [7]. Its association with acute septicemic pasteurellosis in pigs has been recognized. *Pasteurella multocida,* a part of the commensal flora in the upper respiratory tract of pigs is shown to appear intermittently in the nasopharynx and subsequently shed in nasal secretions [8]. During this period, the carrier animal act to become a source of infection for in-contact susceptible animals. The role of pig as a reservoir of *Pasteurella multocida* for the transmission of the disease between pigs and cattle has been suggested. *Pasteurella multocida* is an important pathogen of pigs. It causes pneumonic pasteurellosis and is characterized by pneumonia, purulent bronchopneumonia and pleurisy. Affected pigs may have fever of up to 1060 F, are anorectic and disinclined to move. They show significant respiratory distress, often breathing through the mouth. Death is common after a clinical course of 4–7 days. There is a marked tendency of the disease to become chronic, resulting in reduced weight gains and frequent relapses. On post mortem examination there is a chronic bronchopneumonia with abscessation. Pleuritis is common and there may also be pericarditis. Peracute cases show an acute necrotizing fibrinous bronchopneumonia. Septicaemic disease with death asymptomatic acute deaths may occur within 12 hours in piglets. In India, it is associated with infection by capsular serotype B. The disease occurs in all ages of pigs including adults and is manifested by fever, dyspnoea and congestion on serosal surfaces.

Yet, Pasteurellae have been shown to be a common microflora of the upper respiratory tract in normal animals [9]. The organisms more often than not act as secondary invaders in animals with concurrent diseases or suffering from debilitating stressful conditions. HS is a peracute disease and is considered to be one of the most economically important diseases in Asia particularly in South and South East Asia leading to huge economic loss in livestock industry. *Pasteurella multocida* type B:2 assumed to be transmitted between the animals by aerosol infection and ingestion of contaminated river water or material with *P. multocida* especially during the HS outbreak. The clinical indication of this disease is often characterized by rapid course of high fever, respiratory distress, dullness, depression followed by death [10]. Pathogenesis of *P. multocida* is a complex interaction between host specific factors and specific bacterial virulence factors; therefore, understanding the disease pathogenesis is complex and depends on the bacterial strain, the animal model and their interactions. The key virulence factors identified in *Pasteurella multocida* include capsule, lipopolysaccharides, surface adhesions, iron regulated and iron acquisition proteins [11].

**237**

*Pathological Changes Associated with Natural Outbreak of Swine Pasteurellosis*

**3. Cultural, Phenotypic and Biochemical Characterization**

**4. Genotypic Chracterization of** *Pasteurella multocida*

*Pasteurella multocida* is one of the most fascinating bacterial pathogens. It is a small, Gram-negative rod or coccobacillary, non-motile, non-spore forming, facultative anaerobe belonging to the family *Pasteurellaceae.* The organism can be identified on the bases of cultural, morphological and biochemical characteristics. The organism is a Gram-negative rod with bipolar staining characteristics, which is non-haemolytic on sheep blood agar, aerobic to facultatively anaerobic and produces indole, oxidase, catalase and produce indole and ferment carbohydrates with

Since the initial development of the PCR in 1985, the basic principle of *in vitro* nucleic acid amplification through repetitive cycling has had extensive application in all aspects of fundamental and applied clinical sciences [16]. The application of PCR technology for *Pasteurella multocida* identification was first reported in 1994 when primers constructed from the sequence of the toxA gene (encoding the dermonecrotic toxin implicated in progressive atrophic rhinitis) were used to detect toxigenic *Pasteurella multocida* strains. PCR techniques play a critical role in the clinical laboratory diagnosis as rapid and specific detection of microorganism. It has provided remarkable advances in the diagnosis of infectious agents, particularly in cases where the presence of organism is having significance. Lichtensteiger *et al.* [17] investigated the feasibility of PCR for accurate, rapid detection of toxigenic *Pasteurella multocida* from swabs. They developed a PCR protocol which resulted into amplification of an 846-nucleotide segment of the toxA gene. They developed a concordance of PCR results with (i) detection of toxA gene with colony blot hybridization, (ii) detection of toxA protein with colony immunoblot analysis, and (iii) lethal toxicity of sonicate in mice in a test set of 40 swine diagnostic isolates. Results of an enzyme-linked immunosorbent assay for toxA agreed with the other

The scope of epidemiology in modern animal husbandry practice is continuously widening. Epidemiological data provide information on various diseases which are pre-requisite for planning, execution and monitoring of disease control programmes. It is an important requirement for assessing economic impact of a disease and also for developing disease forecasting system. The disease is usually associated with wet, humid weather and increased incidence is recorded during wet, humid weather and during wet seasons. In countries where systemic epidemiological studies have been carried out, it has become evident that outbreaks do occur throughout the year but those occurring during wet seasons tend to spread presumably due to the longer survival of the organism under moist conditions [8]. Zhao *et al*. [12] examined one hundred and sixty-four clinical isolates of *Pasteurella multocida* recovered from two swine herds in Minnesota. The isolates were characterized by restriction endonuclease analysis (REA) and rRNA gene restriction fragment length patterns. They concluded that these genomic fingerprinting techniques were highly discriminatory and that capsular serotyping in combination with REA or ribotyping was an appropriate technique for epidemiological studies

*DOI: http://dx.doi.org/10.5772/intechopen.94849*

of *Pasteurella multocida* of swine origin.

slight gas production [13–15].

**2. Epidemiology**

*Pathological Changes Associated with Natural Outbreak of Swine Pasteurellosis DOI: http://dx.doi.org/10.5772/intechopen.94849*
