Oscar G. Illanes, DVM, PhD, DACVP

Department of Pathobiology

Pathology of the Respiratory

System

Disclaimer: Images from this presentation come from different sources: Mc Gavin ‘s Pathologic Basis of Veterinary Disease, Dr. King files, Noah’s arkive ,OVC, AVC, author’s own files etc. This presentation is for teaching purposes only, please do not distribute.

General objectives

Overview of the diseases that affect the respiratory system of

domestic animals

Emphasis on:

how to recognize the morphologic changes present within

tissues in specific diseases/ conditions

most common respiratory diseases

how to arrive to the proper morphologic or etiologic diagnosis

for the lesion

Disease pathogenesis, if known

Differential diagnosis, if applicable.

References

A. Lόpez: “ Respiratory System” in Pathologic Basis of Veterinary

Disease, McGavin & Zachary, editors, 5th ed., Mosby, p458-,

2012

J Caswell & K. Williams: “Respiratory System” in JKP

Pathology of Domestic Animals, Vol 2, edited by MG Maxie, 5th

ed., Saunders, p523-653, 2007

Anatomic division of the respiratory

tract

Upper & Lower respiratory

tract. In general the upper respiratory

tract is the portion of the respiratory

system located outside the thoracic

cavity.

Physiologically the respiratory tract

is divided into three independent

but continuous systems:

1.- Conducting system: Includes the

nasal cavity, paranasal sinuses, larynx, trachea

and bronchi. The mucosa of this system

is primarily lined by pseudostratified ciliated

epithelium

and goblet cells.

2.- Transitional system : consists

exclusively of bronchioles which are

lined by Clara cells (detoxification of xenobiotics),

non-ciliated secretory cells and only a few ciliated

cells. Healthy bronchioles do not have

goblet cells.

3. Exchange system: Composed of alveolar ducts and millions of alveoli; thin-walled structures enveloped by a rich network of capillaries, the pulmonary capillaries. Alveoli are lined by epithelial type I (membranous) and type II (granular)

pneumocytes (also called pneumonocytes).

Each of these systems has a characteristic susceptibility to injury and specific type of host response and repair.

The lungs have a dual blood supply:

Through the pulmonary arteries which

conduct deoxygenated blood from

the right side of the heart, and the bronchial

arteries, which carry oxygenated blood.

In addition to gas exchange, the respiratory system is

also involved in phonation, olfaction, temperature

regulation, acid–base balance, blood pressure

regulation etc.

Several of these functions may be affected by

respiratory disease.

Pictures from Dr. Thomas Caceci’s histology

Web site.

Pictures from Dr. Thomas Caceci’s histology

Web site.

Normal Flora – Restricted only to the most

proximal region of the conductive system: nasal

cavity, nasopharynx, larynx and trachea.

The distal portions of the respiratory tract are

considered to be sterile.

Even though the majority of

the organisms of the normal

respiratory flora are harmless

others are potentially

pathogenic; e.g.: Mannheimia

haemolytica, Bordetella

bronchiseptica.

“The air that we inhale every day in a healthy environment contains billions of suspended particles, spores, bacteria, viruses and noxious gases that are constantly carried deep into the lungs”...Fortunately the lungs have a very efficient defence system to deal with the environmental hazards present under normal conditions.

Experimental studies have demonstrated that bacteria

from the nasal flora, including some potentially

important pathogens, are constantly being carried into

the lungs by inspired air. In spite of this constant

bacterial bombardment, the lower respiratory tract remains

essentially sterile due to the presence of

highly effective respiratory defence mechanisms.

Defence mechanisms of the

respiratory system

Non-specific (non immune-

mediated):

Mucous trapping

Mucociliary clearance (mucociliary

escalator)

Phagocytosis

Air turbulence (generated by

coughing and sneezing).

Specific (immune-mediated):

Antibody production

Antibody-mediated phagocytosis

Cell-mediated immunity

Pulmonary Macrophages

Alveolar Macrophages

(“PAMs”)

Intravascular

Macrophages (“PIMs”>

ruminants, cats, pigs and horses)

In dogs, humans and laboratory rodents the cells responsible for removing circulating bacteria and other particles from blood are the Kupffer cells (liver) and splenic macrophages.

..From the web

Animals suffering from a respiratory viral infection

have notably suppressed defence mechanisms which make them

susceptible to bacterial colonization within the airways.

Viruses are not the only factor known to predispose to bacterial

pneumonia, other causes are:

Stress

Dehydration

Pulmonary edema

Uremia

Ammonia

Immunosuppression/ immunodeficiency

Post-mortem examination of the respiratory

tract

Horse-UCVM-09

Thorough systematic examination and appropriate sampling are

very important. Microbiology results should always be interpreted

carefully taken into account clinical and post-mortem findings.

Pig, normal lungs, AVC

Nasal cavity

Ethmoidal hematoma – cause of

epistaxis in horses

Pedunculated tumor-like lesion in

older horses. The exact etiology of

this lesion is unknown.

Dr.King’s show & Tell

Fibrinous rhinitis – mid-sagittal section of the

head – Calf with IBR

Infectious Bovine Rhinotracheitis (formation of diphtheritic membrane)

Oestrus ovis, nasal bot in sheep

– worldwide distribution

From McGavin, Zachary.

Aberrant migration of Oestrus ovis larva, sheep-Texas A&M.

Atrophic rhinitis in pigs.

Multifactorial disease in growing pigs.

Currently is thought to be the result of a

combined infection of Bordetella

bronchiseptica and Pasteurella multocida

types D and A.

Atrophic Rhinitis – UCVM, OI Top: Normal Right: Affected pig

The toxigenic strains of P. multocida produce cytotoxins which inhibit

osteoblastic activity and promote osteoclastic reabsorption of the nasal

turbinates. “The ventral scroll of the ventral nasal turbinate is the area

most commonly and consistently affected”…

Inclusion Body Rhinitis – Porcine Cytomegalovirus (suid herpesvirus 2 [SHV-2]) infection, Pig, AVC, OI Usually in pigs 3-5 weeks of age. Fatal systemic infection occurs occasionally in younger suckling pigs (less than 3 weeks of age).

Nasal submucosal glands with large basophilic Intranuclear inclusions (SHV-2).

Feline herpesvirus 1 (Feline viral rhinotracheitis [FVR]): rhinitis, conjunctivitis

Cat, vesicles, tongue – Feline calicivirus, Noah’s Arkives Morphologic Diagnosis?

Cat, feline calicivirus – ulcerative glossitis Noah’s Arkives

Feline Calicivirus (FCV). Mild oculonasal discharge in addition to vesicular and ulcerative stomatitis - diffuse interstitial pneumonia may also occur.

Cat, diffuse interstitial pneumonia, FCV.

Granulomatous rhinitis, dog due

to Rhinosporidium seeberi (aquatic

protistan parasite), Texas A&M

University

Mature sporangia filled with endospores

Guttural pouch tympany in a foal

Strangles, Streptococcus equi, lymph node and guttural pouch involvement

http://www.equinevoices.org/horses/natural-care-corral/strangles/

Inflammation of the guttural pouch,

horse (guttural pouch empyema) due

to “strangles”-TAMU

“Chondroids”

“Inspissated” exudate

Caused by infection with Aspergillus fumigatus or other Aspergillus species.

Involvement of cranial nerves (VII, IX, X, XI, XII) is common and result in a variety of clinical signs.

Erosion of the wall of the internal carotid artery can lead to epistaxis or fatal hemorrhage

Guttural Pouch mycosis

Guttural pouch Mycosis- horse. Mdx? Multifocal, ulcerative and necrotizing eustachitis

Guttural pouch mycosis, horse

Guttural pouch mycosis, horse, AVC, Dr. A. Lopez.

Guttural pouch mycosis – AVC E24094-97, OI

Guttural pouch mycosis, AVC E24094-97 Which special stains are often used to visualize fungi within tissue sections? GMS (Gomori’s methenamine silver) stain and

PAS (Periodic Acid Shiff) stain.

Nasal Squamous Cell Carcinoma, Cat

Nasal neoplasia

Nasal carcinoma,

10 year-old dog, AVC

3 year-old German Shepherd dog –Nasal and facial deformity, UCVM-09.

Nasal FSA, 3 year-old dog, UCVM.

Enzootic nasal carcinoma, sheep

(retrovirus-induced).

Larynx

Necrotic laryngitis (Calf diphtheria)

Secondary infection by Fusobacterium necrophorum following trauma or viral infection (IBR). Can also occurs as part of oral necrobacillosis in calves and swine.

Plaques of ulceration covered by fibrinonecrotic exudate.

Larynx

Laryngeal hemiplegia

(paralysis) – “roaring”

horses. Atrophy of the left

dorsal cricoarytenoid

muscle.

Usually the result of an

idiopathic neuropathy

affecting the left recurrent

laryngeal nerve.

*From McGavin „s Pathologic Basis of Veterinary Disease book.

Trachea - bronchi

Tracheal collapse: Mainly in toy and miniature dog

breeds; occasionally seen in horses, cattle and goats.

Texas A&M

Dorso-ventral flattening of the trachea and concomitant widening of the dorsal tracheal membrane, pony May result in coughing and exercise intolerance.

UCVM-08, OI, feedlot heifer. Calf, Cornell files.

IBR, Cattle

Ulcerative and necrotizing laryngo-tracheitis

Canine infectious tracheobronchitis

(Kennel cough). A variety of infectious

agents are often isolated

from affected dogs but

there is consensus that

Bordetella bronchiseptica

usually plays a primary

role.

CAV-2, CPIV-2 and to a

lesser extend canine

distemper virus and

Mycoplasma spp., have

predisposing roles.

Horses and ponies– chronic bronchiolitis-emphysema

complex, “heaves”, “broken wind”, Recurrent Airway

Obstruction (RAO). Asthma-like syndrome (used to be

known as Chronic Obstructive Pulmonary Disease (COPD)

From: « Recurrent airway obstruction – heaves ». The Veterinary Clinics, Equine Practice, 19: 63-86, 2003. Renaud Léguillette, DMV, MSc, DACVIM. McGill University, UCVM- Canada.

Severe heaves. The head &neck are extended and the horse shows nasal flaring with mucoid nasal discharge. „„Heave line.‟‟ The hypertrophy of external abdominal oblique

muscles as a result of expiratory efforts suggests that the horse has been chronically affected by heaves.

Recurrent Airway Obstruction (RAO), Heaves.

RAO, horse, HE stained histo slide

Other similar disease in veterinary medicine : Feline asthma, a.k.a. feline allergic bronchitis.

“Hyperactive airway disease”

Lungs

Blood-Air Barrier:

Composed of the

vascular endothelium,

basement membrane of

the endothelial cell,

basement membrane of

the type I pneumocyte

and the cytoplasm of the

of the type I

pneumocyte.

Circulatory disturbances: Pulmonary

haemorrhage

Exercise-induced pulmonary haemorrhage (EIPH):

Relatively common condition in race horses.

Follows strenuous exercise.

Epistaxis is present in only 1-10% of affected horses.

Frequency increases with age and the severity of exertion.

Probably the result of marked elevations in arterial and capillary

pressures during strenuous exercise.

Haemorrhage occurs in the dorso-caudal portions of the caudal

lung lobes.

Massive pulmonary haemorrhage may be the only detectable

lesion in horses that die during exercise .

Epistaxis and pulmonary hemorrhage are relatively

common in cattle with vena cava thrombosis

* From McGavin’s Pathologic Basis of Veterinary Disease

Pulmonary edema, pig

Pulmonary edema, pig

Pulmonary edema

Main pathogenic

mechanisms:

1. ↑ hydrostatic pressure (cardiogenic edema).

2. ↑ vascular permeability: Injury to the blood-air barrier

3. Obstruction to lymphatic drainage: Neoplasia involving thoracic lymph nodes or vessels.

Horse with CHF, UCVM, OI.

Pulmonary edema, horse, UCVM

HE-stain, dark brown pigment within the cytoplasm of alveolar macrophages, UCVM

Iron (Perl‟s) stain – Hemosiderin-laden macrophages (“heart failure cells”) within alveoli – UCVM.

From McGavin’s Pathologic Basis of Veterinary Disease

Pigmentary disturbances: Pulmonary anthracosis

From McGavin’s Pathologic Basis of Veterinary Disease

Atelectasis

Incomplete expansion of the lungs or portions of the

lungs.

Pulmonary parenchyma appears dark-red and sunken in

comparison to aerated lung. Consistency is fleshy and the

lung tissue does not float.

Congenital, acquired, compressive (caused by space-

occupying lesions like hydrothorax, hemothorax,

pleuritis), massive (pneumothorax).

Pulmonary atelectasis – bovine fetus; also in stillborn animals

Aspiration of amniotic fluid

“Meconium is the dark-green mucilaginous material in the intestine of a full term fetus –a mixture of secretions from intestinal glands and amniotic fluid”

Patchy pulmonary atelectasis due to aspiration of

meconium and amniotic fluid-calf, 1 day old, AVC.

Pulmonary Emphysema

“Permanent enlargement of

air-spaces distal to the terminal

bronchiole, accompanied by

destruction of alveolar walls”

Pulmonary Emphysema

Important primary disease in humans where often co-exists with

COPD attributable to cigarette smoking.

“It is thought to be an imbalance between proteases and anti-

proteases (like α1 antitrypsin) Neutrophil-derived serine

proteases, particularly elastase and matrix metalloproteinases from

a variety of sources are the likely culprits. Their concentrations are

enhanced by neutrophil and macrophage activation induced in

chronic bronchitis” –JKP, 2007 –G Maxie, ed.

The emphysematous lung is dysfunctional since the loss of alveolar

septa reduced the alveolar surface area Reduction in gas

exchange.

Pulmonary Emphysema

In animals is always secondary to obstruction of outflow of

air or agonal at slaughter.

Frequent in animals with bronchopneumonia airflow

imbalance the volume of air entering the lungs exceeds

the volume exiting the lung during expiration.

Classified also as alveolar of interstitial (the latter mainly in

cattle).

Bullous emphysema: Large focal

air-filled spaces (bullae) rupture

may lead to fatal pneumothorax.

Cow, pulmonary edema emphysema,

``fog fever``.

Bovine, interstitial emphysema

Pneumonia

No universal classification in

veterinary medicine –quite

confusing.

Right: Diagram of common

patterns of pneumonia:

A: Normal lung

B: Suppurative

bronchopneumonia

C: Fibrinous bronchopneumonia

D: Interstitial pneumonia

E: Embolic pneumonia

F: Granulomatous pneumonia

A. Lopez, Atlantic Veterinary College

Aerogenous (airborne) route and hematogenous route.

Pneumonias in cattle: Viral pneumonias

Infectious Bovine Rhinotracheitis (IBR): Caused by BoHV-1.

Para-influenza-3 virus (PI-3 virus) and Bovine Respiratory

Syncytial virus (BRSV) cause a transient rhino-tracheitis and

broncho-interstitial pneumonia with the formation of eosinophilic

intracytoplasmic inclusions bodies in bronchial, bronchiolar and

alveolar epithelial cells and alveolar macrophages. Formation of

syncytial cells occurs in both, BRSV and PI-3 virus infection.

BRSV and PI-3 should be considered in calves with necrotizing

bronchiolitis

Diagnosis is confirmed by virus isolation, PCR or detection of

viral antigens by fluorescence antibody test (FAT) or

immunohistochemistry (IHC).

BRSV-calf, AVC

BRSV, heifer, Cornell files –Syncytial cells

BRSV. Right: IHC stains demonstrates widespread injury to the airway Epithelium.

Bovine enzootic pneumonia (chronic

suppurative bronchopneumonia.

Disease caused by a variety of etiologic agents which include respiratory viruses, Mycoplasmas, Chlamydophila, followed by opportunistic bacteria such as Pasteurella multocida, Arcanobacterium pyogenes, Histophilus somni, Mannheimia haemolytica and E.coli. Calves with bovine leukocyte adhesion deficiency (BLAD), which prevents the migration of neutrophils from the capillaries, are highly susceptible to bronchopneumonia.

Chronic suppurative bronchopneumonia, Calf, OVC.

Chronic suppurative bronchopneumonia, Calf, TS, OVC.

Suppurative bronchopneumonia, calf, A. Lόpez, AVC.

Abscessation and bronchiectasis are Common sequels of chronic suppurative pneumonia.

Pneumonic mannheimiosis (“shipping

fever”)

Acute respiratory disease that occurs in cattle several days or weeks after shipment.

Because Mannheimia haemolytica (formerly Pasteurella haemolytica) is typically isolated the term penumonic mannheimiosis or pneumonic pasteurellosis have been used.

Most economically important respiratory disease of cattle in North America, particularly in feedlot cattle.

Fibrinous bronchopneumonia, OVC.

Pneumonic mannheimiosis, steer, from McGavin.

Mannheimia haemolytica biotype A, serotype 1 is responsible for the severe pulmonary lesions (areas of necrosis etc.)

Pneumonic mannheimiosis: Marbling appearance of the pulmonary parenchyma.

What type of necrosis?

Respiratory histophilosis

Part of the Histophilus somni

disease complex (TME,

pneumonia, pleuritis,

myocarditis, arthritis, abortion

etc.,).

May cause suppurative or

fibrinous bronchopneumonia.

The later may be

undistinguishable from the

fibrinous bronchopneumonia

caused by Mannheimia haemolytica.

Fibrinous pneumonia, cattle-Cornell files

Mycoplasma bovis pneumonia

Important cause of chronic

respiratory disease in feedlot

cattle – common in Alberta.

The organism causes a chronic

necrotizing bronchopneumonia

which is quite characteristic.

M. bovis also causes severe chronic

fibrinous arthritis.

Chronic necrotizing bronchopneumonia, heifer, UCVM. Mycoplasma bovis was cultured from the lesions, OI, 2008.

Mycoplasma bovis

Necrotizing bronchopneumonia, heifer, UCVM, O.I., 2008.

What type of necrosis?

Positive immunoperoxidase staining of M. bovis antigens, from McGavin‟s, 2012

Bovine tuberculosis

Caused by M. bovis. It has been suggested

that the term TB should be limited to

diseases caused by M. tuberculosis (human)

and M. bovis (cattle); other conditions

should be referred as “Mycobacteriosis”.

In North America the disease has been

almost eliminated but there still outbreaks

that often originate from wild life (M. bovis

not only affects cattle and humans but also

deer, elk, bison etc. wild ruminants).

Lesions are more common in

retropharyngeal lymph nodes, lungs,

thoracic and mesenteric lymph nodes.

Lesions in cervids often contain prominent

suppurative exudate and may resemble

abscesses... Multifocal granulomatous pneumonia, M. bovis, cow, Dr. King-Cornell’s file.

Verminous bronchitis/ pneumonia

In cattle is caused by infection with Dictyocaulus viviparus. Varies from interstitial pneumonia (larval migration) to chronic bronchitis (intrabronchial adult parasites) to granulomatous pneumonia (eggs, dead larvae).

Cornell Files

Heifer, dictyocaulosis, OI, UCVM-2010 Dictyocaulus filaria –sheep, goats Dictyocaulus arnfieldi –equids (horses, donkeys)

Terminal bronchi from the right caudal lung lobe, pig. Slaughterhouse specimen, St. Kitts. Lung worms are admixed within slightly turbid mucoid exudate. Morphologic dx?.., etiologic dx?...

Lung worms in pigs: Metastrongylus spp.

Numerous thin and elongated worms within the terminal bronchi of the caudal (diaphragmatic) lung lobes: Metastrongylus spp. Pig, slaughterhouse specimen, St. Kitts, 2012.

Same pig as in the previous image. Numerous Metastrongylus spp. are present within a bronchus, caudal lung lobe. Possible morphologic dx: catarrhal bronchitis; Etiologic dx: Verminous (or parasitic) bronchitis; pulmonary metastrongylosis. RUSVM, OI.

Atypical Interstitial Pneumonia (AIP) of cattle

Pneumonias that did not fit any of the “classical” forms of

pneumonia

Characterized by the presence of edema, interstitial

emphysema, hyaline membranes, type II pneumocyte

hyperplasia and interstitial fibrosis with cellular infiltrates

These types of pneumonias have specific etiologies.

Investigators have proposed that these syndromes previously

clustered under AIP be named according to their specific

cause or pathogenesis.

Diffuse alveolar damage –formation of hyaline membranes – AIP, cow. From McGavin’s

Atypical Interstitial Pneumonias -

common syndromes:

Bovine pulmonary edema & emphysema (“fog fever”) Extrinsic allergic alveolitis (hypersensitivity pneumonitis) Reinfection syndrome (hypersensitivity to Dictyocaulus sp.

or BRSV). Milk allergy: type I hypersensitivity in cows sensitized to

their own milk casein and lactalbumin. Ingestion of moldy potatoes contain 4-ipomeanol which

is metabolized by mixed function oxydases in the lung (Clara cells) to a potent pneumotoxicant.

“Fog Fever”

Bovine pulmonary edema & emphysema (“fog fever”) occurs in cattle grazing “fog” pastures (re-growth pasture after a hay or silage has been cut or lush green grass). L-tryptophan present in the pasture is metabolized in the rumen to 3-methylindole → absorbed into the blood and carried to the lungs → metabolized by the mixed function oxidases of non-ciliated bronchiolar epithelial cells (“Clara” cells) into a highly pneumotoxic compound that causes extensive necrosis of bronchiolar epithelial cells and type I pneumocytes (diffuse alveolar damage).

“Extrinsic Allergic Alveolitis”

(hypersensitivity pneumonitis)

Common; mainly seen in adult dairy cows in the winter. The human

counterpart is referred to as “farmer’s lungs”.

Type III hypersensitivity reaction to inhaled organic antigens, most

commonly fungal spores present in moldy hay (local deposition of Ag-

Ab complexes in the lungs).

Gross lesions vary from subtle gray subpleural foci of granulomatous

inflammation to severe lesions in which the lungs acquire a “meaty

appearance” due to alveolar epithelial hyperplasia, interstitial

inflammation and fibrosis.

Pathogenesis of toxic and allergic pneumonias

(“AIP”) in cattlle.

* From McGavin’s pathology book

Pneumonias of Sheep

Viral pneumonias: Like in cattle PI-3 virus and RSV can produce pneumonitis in sheep.

Maedi (maedi-visna): Lifelong, persistent disease of sheep that occurs in most countries with the exception of Australia and New Zealand. It is also known as Ovine Progressive Pneumonia (OPP).

The disease is caused by a retrovirus of the lentivirus subfamily (ovine lentivirus) similar to the agent of CAE. Infection results in a lymphocytic interstitial pneumonia (LIP).

The virus may also cause a non-suppurative encephalitis (Visna), lymphocytic arthritis, lymphofollicular mastitis and vasculitis.

Maedi is characterized by dyspnea and an insidious slowly progressive emaciation despite good appetite.

In goats, CAE virus can cause a lymphocytic interstitial pneumonia

similar to OPP in sheep.

Bacterial Pneumonias - Sheep

Chronic enzootic

pneumonia:

Multifactorial disease –rarely

fatal. In general it affects animals

younger than 1-year-old.

Etiologic agents include

Mannheimia haemolytica,

Pasteurella multocida, PI-3,

adenovirus, reovirus, RSV,

Chlamydophila, and Mycoplasmas

(mycoplasma ovipneumoniae).

Suppurative bronchopneumonia, sheep – Pasteurella multocida – from McGavin’s.

Ovine pneumonic Mannheimosis: Similar to

shipping fever in cattle.

Septicemic pasteurellosis: Caused by

Mannheimia haemolytica (biotype A) usually in lambs under 3

months.

Bibersteinia (Pasteurella) trehalosi (biotype T) usually in lambs 5 to

12 months-old.

Lesions: necrotizing pharyngitis and tonsilitis, septicemia with

disseminated intravascular thrombosis and bacteremia.

u

Multifocal subpleural pneumonitis – Muellerius capillaris sheep, Cornell files

Verminous bronchitis also occurs in sheep and goats. The etiologic agent Is Dictyocaulus filaria.

Pneumonias of horses

Viral pneumonias: Equine viral rhinopneumonitis (EHV-1, EHV-

4) and equine influenza are important diseases in horses

worldwide. In addition, equine viral arteritis (EVA) virus and

equine adenovirus can also cause pneumonia in horses.

These viruses often cause only a transient broncho-interstitial

pneumonia but impair the pulmonary defences and make horses

susceptible to secondary bacterial pneumonias (P. Multocida,

Streptococcus spp., E.coli, Klebsiella pneumoniae, Rhodococcus equi etc.).

It has also been suggested that viral respiratory infections may

predispose horses to “airway hyper-responsiveness” and “chronic

obstructive respiratory disease” (COPD).

Equine Viral Arteritis (EVA) virus – Arterivirus.

Sporadic pansystemic disease of foals and horses:

May result in interstitial pneumonia with

vasculitis, pulmonary edema, hydrothorax and

hydroperitoneum.

Equine Morbillivirus (Hendra virus disease): Fatal

respiratory disease in horses and humans (high mortality rates

were seen in both horses and humans) which appeared in

1994 in Australia. Classified as a Morbillivirus, subfamily

Paramyxoviridae. Affected horses have severely edematous

lungs. Histologically there is vasculitis and the presence of

multinucleated syncytial cells, typical of morbillivirus

infections, in the endothelium of small pulmonary blood

vessels and alveolar capillaries. No inclusion bodies are seen.

Clinical signs are non-specific and include fever, anorexia,

respiratory distress and nasal discharge

Interstitial pneumonia-foal, Equine Viral Rhinopneumonitis, Texas A&M, JE.

Interstitial pneumonia due to adenovirus or Pneumocystis carinii Infection are common complication in Arabian foals with SCID (Inherited disorder- autosomal recessive trait- characterized by lack of B and T lymphocytes die before 5 months of age)

Right: Pneumocystosis, Pig, AVC. Foamy eosinophilic proteinaceous material within alveoli. Fungal organisms are detected with Gomori’s methenamine silver stain (GMS).

“Pneumocystosis is one of the most common and often fatal complications in AIDS patients”.

Jack Russell Terrier

Adenovirus infection, foal, HE.

Interstitial pneumonia due to Pneumocystis carinii infection with concomitant Rhodococcus equi infection in a foal (Arabian CID foal).

Rhodococcus equi

Important cause of morbidity and

mortality in foals worldwide.

Facultative intracellular gram positive

bacterium that causes two major

clinical syndromes.

The organism may become enzootic in

farms where the organisms has been

shed earlier by affected foals.

Virulence factors encoded by plasmids

(virulence-associated proteins) appear

to be responsible for the survival of

the organism within macrophages

(avoid phagocytosis by inducing

defective phagosome-lysosome

fusion).

6-week-old foal, Chronic pyogranulomatous pneumonia –Rhodococcus equi, Texas A&M University.

6-week-old foal, Chronic pneumonia –Rhodococcus equi, Texas A&M University. Mdx: Pyogranulomatous pneumonia

Cytokines, lysosomal enzymes and bacterial toxins are responsible for extensive caseous necrosis of the lungs and recruitment of large numbers of neutrophils, macrophages and giant cells containing numerous intracytoplasmic organisms. Affected foals develop chronic coughing and weight loss. “Any foal with bronchopneumonia unresponsive to routine broad-spectrum antibiotic therapy should be suspected of having R. equi bronchopneumonia” Equine practice, vol 14 (1): 15-18, 1992.

R. equi can infect people undergoing

immunosuppression (AIDS, chemotherapy,

therapeutically-induced immunosuppression

because of organ transplantation).

Foal, Rhodococcus equi– Texas A&M

pyogranulomatous enterocolitis/ lymphadenitis

Horse, idiopathic broncho-interstitial pneumonia. Note prominent Type II pneumocyte hyperplasia., HE

Horse, embolic Aspergillus infection (Mycotic pneumonia), Texas A&M, Dr. John Edwards.

Multifocal, necrotizing and hemorrhagic (or necro-hemorrhagic) pneumonia

Pneumonias of pigs

• Viral Pneumonias:

Porcine reproductive and respiratory syndrome (PRRS): First recognized in Europe in 1987. PRRS is characterized by late-term abortions, stillbirths and respiratory disease in young pigs (interstitial pneumonia).

Swine Influenza: Resulted from adaptation of the type A influenza virus that caused the pandemic of human influenza during World War I. Low mortality unless complicated with secondary bacterial infections. H1N1 influenza pandemic in 2009.

Postweaning multisystemic wasting syndrome (PMWS):

Causes progressive emaciation in weaned pigs. The causative agent is PCV-2. May result in interstitial pneumonia.

Porcine Respiratory Coronavirus (PRCV): Sporadic cause of mild bronchointerstitial pneumonia with necrotizing bronchiolitis.

Interstitial pneumonia, feeder pig – highly suggestive of viral pneumonia

Right: Pneumocystosis, Pig, AVC. Foamy eosinophilic proteinaceous material within alveoli. Fungal organisms are detected with Gomori’s methenamine silver stain (GMS). Infections with Pneumocystis carinii are common in pigs with PRRS and PMWS.

Pig, enzootic pneumonia-Cornell. Multifactorial disease, Mycoplasma hyopneumoniae is the main pathogen involved. The organism induces a suppurative or cattarrhal bronchopneumonia with BALT hyperplasia that is quite characteristic. This highly contagious disease of pigs is influenced by immune status and management factors such as crowding, poor ventilation, humidity and temperature fluctuation in the barns. The disease is characterized by low mortality unless complicated with secondary pathogens.

Porcine Enzootic Pneumonia : Mycoplasma pneumonia (Mycoplasma hyopneumoniae, young piglet, UCVM, O.Illanes. Multifactorial disease.

Mycoplasma pneumonia, young piglet, UCVM, OI. The bronchopneumonia is mild to moderate (low mortality) unless complicated with Pasteurella multocida, Arcanobacterium pyogenes, Bordetella bronchyseptica, Haemophilus spp., Mycoplasma hyorhinis etc.).

3-month-old pig, fibrinous pleuritis and pneumonia, may be a component of Glasser’s disease (Haemophilus parasuis) CVM, Western University of Health Sciences, O.Illanes

Porcine Contagious Pleuropneumonia, Actinobacillus pleuropneumoniae

Highly contagious often fatal fibrinous bronchopneumonia of pigs 2-5 months of age. Dorsal area of the caudal lung lobes are often affected. Lesions are severe and characterized by hemorrhage, necrosis and thrombosis. Except for the distribution lesions are similar to those of pneumonic mannheimiosis of cattle.

Cornell files

Porcine Contagious Pleuropneumonia, Actinobacillus pleuropneumoniae, CVM, Western University of Health Sciences, O.Illanes.

Top: Cut surface, contagious pleuropneumonia, pig. Nebraska Diagnostic Laboratory – From McGavin‟s 2012.

Pneumonias of Dogs

Pneumonias are not as common in dogs as in food-

producing animals.

Infectious pneumonias: Infectious tracheobronchitis

(Kennel cough) and canine distemper are the most

common.

Non-infectious: Uremia and paraquat (widely used

herbicide) toxicity are most common

• In addition to distemper, canine adenovirus type 2 (CAV-2),

canine herpesvirus 1 (CHV-1) and canine influenza virus can

produce pneumonias in dogs.

• Bacterial pneumonias are often secondary to distemper virus

infection or aspiration of gastric contents (when pulmonary

defence mechanisms have been impaired). Pasteurella

multocida, Streptococcus spp., E. Coli, Klebsiella pneumoniae and

Bordetella bronchiseptica can be involved.

Broncho-interstitial pneumonia, canine distemper

From McGavin’s Path. Basis of Vet. Disease

Aspiration pneumonia, dog.

Granulomatous pneumonia, Blastomyces dermatitidis, dog -OVC

Dog, mycotic pneumonia (granulomatous pneumonia). Left: Blastomycosis, Bottom: Histoplasmosis

McGavin’s –Path Basis of Disease

Uremic pneumonitis, dog.

Pneumonias of cats

Upper respiratory infections: Common

Pneumonias: Rare

The viruses that produce upper respiratory disease may

also induce pneumonia, but unless complicated with

secondary bacterial infections they usually do not pose a

significant clinical problem.

Cat, Dr. King, Cornell

Aelurostrongylus abstrusus

Snails and slugs are the intermediate hosts. Subpleural nodules contain larvae and eggs, HE.

Pulmonary neoplasia

In comparison to humans primary pulmonary

tumors are rare in animals

Most are malignant an appear as solitary masses

of variable size

In domestic animals they are most common in

dogs and cats.

Cat, pulmonary adenocarcinoma, HE.

Ovine pulmonary carcinoma (pulmonary

adenomatosis).

3-year-old sheep, University of Zaragoza, Spain – in McGavin’s

Caused by a transmissible retrovirus. Found around the world but not in New Zealand or Australia. Mainly seen in mature sheep. Slowly progressive signs of respiratory disease death after several months from the initial onset of respiratory signs.

Metastatic neoplasms are relatively common. Primary pulmonary neoplasms, largely carcinomas are relatively rare but more common in aged dogs and cats.

Dog, Morphologic diagnosis? Cornell Files

Hydrothorax, 8-y-old dog, AVC

From McGavin’s Path. Basis Of Vet. Disease

Chronic liver disease (end-stage liver, cirrhosis).

Pleura & pleural cavity

Hemothorax, dog with ruptured aortic aneurism.

Chylothorax, mink, WCVM

From McGavin’s Path. Basis Of Vet. Disease

Fibrnous pleuritis, horse.

Pyothorax, Pasteurella Multocida, cat

Chronic pleuritis with “sulfur granules”, nocardiosis (Nocardia asteroides), Cat.

From McGavin’s Path. Basis Of Vet. Disease

Mesothelioma – In domestic animals seen mainly in cattle – can be congenital. In humans has been associated with inhalation of asbestos (mining, construction, ship building).

Additional Information…

Fibrinosuppurative pleuropneumonia, rabbit –P. Multocida, Atlantic Veterinary College. Pasteurellosis is a common disease in domestic rabbits. P.multocida can result in rhinitis (“snuffles”), pneumonia, abscesses, reproductive tract infections, ear infections and septicemia.

Emu, AVC Mycotic airsacculitis – Aspergillus spp. infection

Emu, granulomatous pneumonia – Aspergillus, spp., AVC-1996

The End...