Swine Health Quiz on Atrophic Rhinitis

Swine Respiratory Diseases

• Swine respiratory diseases are a significant concern in the swine industry
• Various pathogens contribute to respiratory issues in pigs
• Understanding disease patterns (e.g., interstitial vs. bronchopneumonia) is crucial for diagnosis
• Some diseases are highly contagious while others persist in carrier animals

Swine Respiratory System

• The respiratory system in swine includes the nasal section, trachea, and lungs

Pneumonia

• Interstitial pneumonia suggests viral infection
• Bronchopneumonia suggests bacterial etiology Normal lung histology is characterized by distinct alveoli structure

Atrophic Rhinitis

• Characterized by snuffling, sneezing, and nasal bleeding
• Nasal turbinate atrophy and distortion common
• Toxigenic strains of Bordetella bronchiseptica and Pasteurella multocida Type D are frequently associated
• Management and husbandry play a role, including dust reduction and ventilation
• Symptoms can appear as early as 1 week of age
• Diagnostics include history, lesions, clinical signs, and culturing of affected portions

Mycoplasma hyopneumoniae

• Enzootic disease, often associated with the Porcine Respiratory Disease Complex (PRDC)
• Carrier swine are a major source of infection
• Chronic persistent, non-productive cough; suppressed growth despite normal appetite are symptoms
• Morbidities are high but mortality is generally low
• Bacteria survives in pigs for months.
• Difficult to transmit to other animals

Epidemiology of Mycoplasma hyopneumoniae

• Survives poorly in environment but lasts for months in pigs
• Spread is via direct contact or aerosol transmission
• Pathogenesis involves lung consolidation, bronchitis, bronchiolitis, and airway obstruction
• Diagnosis through immunohistochemistry, PCR, and serology
• Treatment with parenteral antibiotics available

Actinobacillus pleuropneumoniae (APP)

• Actinobacillus pleuropneumoniae is host-specific to swine
• Hemolytic, Gram-capsulated coccobacillus
• 15 serotypes exist, with 1 and 5 being more virulent
• Does not persist in the environment, but can colonize and stay infectious for a long duration
• Four exotoxins (RTX toxins) are produced
• Antibodies to exotoxins are crucial for immunity

Epidemiology of APP

• Survivors can remain carriers
• Transmission via direct contact with nasal secretions or aerosols, but fomites don't remain infectious for long
• Pathogenesis involves hemolysin and toxins targeting endothelial cells, vasculitis in the lungs, thrombosis inflammation and infarction.
• Sudden death can occur from shock
• Immunity can occur gradually through colostrum
• In naïve pigs, fulminating disease is common

Clinical Signs of APP

• Acute outbreaks often lead to sudden death
• Common symptoms include prostration, high temperatures, apathy, anorexia, stiffness, vomiting and diarrhea
• As disease progresses, dyspnea with oral breathing may be accompanied by foamy bloody discharge
• Peripheral and generalized cyanosis of extremities can follow

Lesions of APP

• Lesions most often affect the respiratory tract, causing necro-hemorrhaging, fibrinous pleuritis and fluid build in thoracic cavities
• Necrosis and hemorrhage frequently observed in dorsal diaphragmatic lobes
• Bloody frothy buildup in large airways, which then may develop into inflammation and infarction
• Serofibrinous pericarditis, pharyngitis, and occasional polyarthritis may occur
• Lungs may have necrotic nodules or may be fibrous causing rib cage adhesion

Diagnosis of APP

• Sudden onset of acute widespread disease
• Isolation and identification of organism via tissue culture and PCR
• Complement fixation and ELISA also used
• Management strategies include restricting introduction of new animals, quarantines, vaccination with subunit vaccines or older types, cleaning/disinfection of facilities.
• Also depopulation/repopulation methods to control spread

Porcine Reproductive and Respiratory Syndrome (PRRS)

• Enveloped RNA arterivirus with significant heterogeneity
• Moderate resistance to environmental degradation.
• Inactivated by phenol, formaldehyde, and some disinfectants
• Replicates in macrophages, particularly pulmonary intravascular and alveolar macrophages (PIMS and PAMs) in vitro
• Variation in virulence among strains
• Interactions with other diseases, particularly Mycoplasma hyopneumoniae

Epidemiology of PRRS

• Persisting long-term carrier status in pigs (> +200 days), but most stop shedding by 60 days post-infection
• Highly contagious virus (10 virions can cause disease)
• Found in respiratory secretions, urine, semen, mammary secretions, and feces
• Boars can shed the virus up to 92 days in semen
• Aerosol spread possible
• Viral transmission occurs through direct contact and aerosol

Pathogenesis of PRRS

• Transmission via tonsils and upper respiratory system replication in lymphoid tissues persistent viremia
• Infects and compromises PIMS and PAMs function → interstitial pneumonia
• Increased host lung vulnerability to secondary pathogens

Clinical signs PRRS

• Reproductive problems in breeding animals: abortions, mummified fetuses, stillbirths, conception failure, boar sterility
• Respiratory problems in growing animals

Swine Influenza

• Type A orthomyxoviridae virus with glycoprotein spikes serving as major antigens
• Hemagglutinin (H) has 16 varieties, Neuraminidase (N) has 9 varieties
• Classical subtype in swine is H1N1, including variants like H3N2 and H1N2
• Virus persists a short period outside hosts (<2 weeks) and is easy-to-inactivate

Pathogenesis of Swine Influenza

• Attacks nasopharynx, causes inflammation, and necrosis in respiratory epithelium
• Can affect bronchial/bronchiolar structures, interlobular septa, and turbinate epithelium
• Type 2 pneumocytes affected in lungs causing lower surfactant production and impaired phagocytosis of secondary micro-organisms

Clinical Signs of Swine Influenza

• Sudden onset in infected groups.
• Fever, oculonasal discharge, prostration, weakness, anorexia, coughing
• Uncomplicated cases rarely cause death, but significant weight loss, body condition score changes and costs of medication may appear.

Diagnostic tests for Swine influenza

• Sudden onset of disease across herd
• Fluorescent antibody test on fresh lung sections
• Virus isolation from lung tissue and nasal swabs in embryonated eggs
• PCR tests on nasal swabs and/or lung tissue
• Paired serologic titers tests to monitor virus increases
• Comorbidities like Mycoplasmal pneumonia may also be present

Porcine Respiratory Coronavirus

• Not zoonotic
• May have a mild seasonal impact in some herds.
• Asymptomatic herds can be identified via serology

Porcine Circovirus

• Novel strain (PCV2) identified 1990s as distinct from non-pathogenic PCV1
• Further strain PCV3 identified in 2015 associated with high morbidity, mortality, PMWS, PDNS, reproductive failure
• PCV2 is ubiquitous in swine populations making it hard to distinguish from inapparent infections
• Will increase severity of other diseases like Mycoplasma hyopneumoniae, IAV, and PRRS
• PCV2 is consistently seen in pigs with PMWS

Epidemiology of PCV

• Nearly all US swine herds seropositive (positive antibody response) for PCV2
• Seroconversion (antibody development) by 2-4 months of age, though clinical symptoms often absent
• PMWS pigs tend to grow for a period and then decline
• Morbidity can range from 2-30% and case fatality often is high (80%)
• PCV2 Infection
• Infects macrophages and monocytes persisting in lymphoid tissues and lungs
• Chronic lymphohistiocytic/granulomatous inflammation, pneumonia, interstitial pneumonia, erosive bronchiolitis fibrosis occur in various tissues and organs
• May result in blotchy purple skin lesions/nephropathy (likely an immune response, PDNS )

PCV Clinical signs

• Pallor
• Lymph node and spleen enlargement
• Interstitial pneumonia
• Depletion of lymphoid tissues (germinal centers)
• Immune-mediated vasculitis
• Skin discoloration, kidney swelling, hemorrhage, mulitfocal nephritis

PCV Diagnosis

• PCR testing
• Immunohistochemistry
• Clinical signs and lesions observation
• Demonstration of PCV2 in tissue lesions
• Treatment with antibiotics to manage secondary infections

Porcine Dermatitis and Nephropathy Syndrome

• Other viremias to consider (ASF, CSF, and Eryisepelas Salmonella)