This document summarizes various respiratory diseases and conditions in veterinary pathology. It describes the typical locations of particle deposition in the respiratory tract. It then covers different types of pneumonia like bronchopneumonia, lobar pneumonia, and interstitial pneumonia. Specific conditions discussed include rhinitis, sinusitis, laryngitis, bronchitis, bronchiectasis, atelectasis, and emphysema. It also covers circulatory issues, tumors, pneumoconiosis, and pleuritis. Hemorrhagic septicemia caused by Pasteurella multocida is explained in detail.

1. Veterinary Pathology of Respiratory
System

2. • Most of the agents are removed in the air
passages,mainly in the upper respiratory
passage .
• Particals of 1-2 micrometer mostly
deposited at broncho alveolar junction , air
velocity here is zero .Bigger particals are
trapped in the upper respiratory passages.

3. Routes of Respiratory insults
1.Aerogenous routes
Nasal passages & upper air way: irritants ,highly
soluble gases , infectious agents
Distal air ways : Fine particles ,weakly soluble gases,
infectious agents
2. Hematogenous routes: alveolar septa and
pulmonary interstitium
Toxins /infectious agents
3. Trauma

4. Terminology of Respiratory System
Rhinitis :It is the inflammation of mucous
membrane of nose.
Sinusitis :It is inflammation of sinus .
Pharyngitis :It is inflammation of pharynx.
Trachitis : It is inflammation of trachea .
Bronchitis : it is the inflammation of bronchi
Bronchiectasis :It is the dilatation of one or

5. • Brochostenosis: narrowing of bronchial
lumen
• Atelectasis: incomplete distension of
alveoli
• Emphysema: accumulation air leading to
distension

6. Rhinitis
• Injury to the mucous membrane - irritant
gases, dust, excessive dryness of the
weather
• Immunodeficiency
• Nonspecific stress
• Viruses, bacteria, fungi, allergens,
parasites (Myiasis, schistosoma nasalis)

7. • Acute or chronic
• Serous, cattarhal, purulent, ulcerative,
pseudomembranous, hemorrhagic, or
granulomatous (Aspergillus fumigatus,
Cryptococcus neoformans)
• Specific rhinitis
– Strangles
– Glanders
– Melioidosis – Pseudomonas pseudomallei
– Infectious Bovine Rhinotracheitis – bovine herpes
– Feline viral rhinotracheitis – feline herpes virus

8. These diseases usually starts as acute
mucous (cattarahal ) inflamation of the
respective mucous membrane & later tend
to become purulent or fibrinous
,depending on the nature of infectious
agent, like the human “cold “starts as
rhinitis and then spread to lower part of
respiratoy system depend peon the
etiological agent virulence and suseptibility
of host.

9. Acute infections localizing upper
Respiratory system
• Equines : strangles (streptococcus equi)
,equine rhinopneumonitis,influenza.
• Bovines :pasteurellosis(HS) ,malignant
catarrhal fever(MCF),Infectious Bovine
rhinotrachitis (IBR)and calf diphtheria.
• Canines :canine distemper
• Feline : feline viral rhinotrachitis
• Poultry :ND ,IB,ILT,fowl cholera, infectious
coryza etc.

10. Sinusitis
• Acute sinusitis 7-21 days (7 days viral
illness)
• Spontaneous resolution of ARS -40%
• The most common pathogens: strep
pneumonia-30%,
• non typeabale hemophilus infl.-20%,
moraxella catarrhalis.(20% in children)
• Staph aureus- 30%
• Anaerobes- rare

11. Larynx and Trachea
• Laryngitis can occur as part of oral
necrobacillosis (Fusobacterium
necrophorum) – calf diphtheria

12. Bronchi and Bronchioles
• Inflammation
• Bronchiectasis – permanent abnormal
dilation of bronchi and bronchioles
– Secondary to bronchitis
• Saccular – focal necrotizing bronchitis,
emphysema
• Cylinderical – chronic suppurative bronchitis of
bronchopneumonia in cattle

13. Atelectasis
• Incomplete expansion of lungs
– Congenital – stillborn animal, minor degree of
incomplete expansion – miconium
– Acquired – associated with obstruction,
compression

14. Emphysema of Lungs
• Alveolar
• interstitial

18. Circulatory Disturbances of
Lungs
• Pulmonary Edema –
cardiogenic due to
left atrial pressure or
bilateral cardiac
failure
• Pulmonary
hemorrhage
• Embolism,
thrombosis,
infarction

19. Pneumonia / pneumonitis
Inflammation of substance of lung.
Pneumonia is common in animals
especially in weak and young animals in
colder weather.
Classification of pneumonia :
Morphologic : bronchopneumonia
(lobar,lobular )
Interstitial ,focal ,diffuse.
Exudate : fibrinopurulant ,granulomatous

20. Bronchopneumonia
It is perhaps the most common cause of
pneumonia in animals .it is usually
exudative lesions originating at
bronchoalveolar junction.The infection
entrer through aerogenous route ,it has
cranioventral distribution .
Causes :bacteria ,virus ,fungus ,aspiration
,forced feeding, gastric intubation,vomiting
,regurgitation ,neurological disease

21. Gross & microscopic appearance
• Affected lung is firm and
consolidated(hepatized ) may be dark red
,grey or pale depending upon the age
,nature of lesions . Cut surface is
edematous and purulent exudates may be
expressed from bronchioles. It may be
lobular or lobar pneumonia

22. Bronchopneumonia

23. Lobular Pneumonia ; it is patchy in nature
and involve individual lobules.it is
generally less severe and slowly
progressive in nature .it shows checker
board appearance.
Lobar pneumonia :whole lobe of lung is
involved in this type. It is severe and
rapidly progressive in nature.it is typically
caused by manhemia hemolytica (Shiping
fever ) in cattle .

24. Results of pneumonia
1. In an uncomplicated case exudation is
removed by absorption & expectoration
and recovery take place.
2. If condition persist ,it become chronic
there is fibrosis which lead to permanent
dilatation of bronchi i.e bronchiectasis
3. If there is introduction of pus forming
bacteria , then there will be pus formation
which lead to gangrene and necrosis.

25. Pathogenesis of pneumonia
There are four successive stages with out
any clear demarcation
1.Congestion
2.Red hepatization
3.Grey hepatization
4.Resolution

26. Congestion
There is serous exudate ,swollen
,hyperemia, piece of lung still float in
water. under microscope blood vessels &
capillaries distended and engorged with
blood ,alveoli are filled with serous
exudate . This condition may develop in 2
minutes to 2 hours depending upon the
virulence and nature of etiological agent.

27. Red hepatization
Here is fibrinous exudate ,the affected area
of lung show consolidated or hepatized
(firm like liver ).Completely hepatized lung
sink in water. under microscope blood
vessels & capillaries distended and
engorged with blood ,alveoli are filled with
fibrinous exudate (inflammatory cells &
fibrin )which lead to hepatization of lungs
.this stage is reached in two days .

28. Grey hepatization
Slowly fibrin and WBCs number increased
at the specific site , no of RBCs
decreased in number which give lungs
grey appearance .there is greyish fibrinous
exudate in alveoli. This stage stats at 5th
day .

29. Resolution
• If etiological agent is destroyed by immune
response or therapy ,the lesions are
resolved ,neutrophils undergo apoptosis,
fibrin & exudates is engulfed by
macrophages .Remaining exudate is
removed through coughing. Lungs return
to normal in 3-4 days .

30. Special type of pneumonia
1. Gangrenous pneumonia /Aspiration
pneumonia
2. Pneumonia of shipping fever
3. Granulomatous pneumonia

31. Special forms of pneumonia
• Gangrenous – penetration of foreign
bodies
• Aspiration
• Lipid – inhalation of lipids
• Uremic – edema
• Garnulomatous pneumonia –
Actinobacillus, Actinomyces, or Norcardia
spp., tuberculosis, fungal (Aspergillus
fumigatus

32. Gangrenous pneumonia
It is type of pneumonia in which ultimate
reason is gangrene of pulmonary tissue .it
is also called aspiration pneumonia
,drenching pneumonia foreign body
pneumonia , medication pneumonia , rapid
pneumonia. It is caused by aspiration of
foreign material often liquid. Lesion will
depend upon the nature , quantity and
irritation ability of medicine or other
chemical.

33. Drugs are most dangerous because of
there irritation and presence of oil in their
composition . Oil based medicine are not
absorbed ,stay longer in lungs and cause
more problems. Recumbancy,
regurgitation, pharyngeal paralysis,
dysphagia & bucket milk feeding to
young calves can also lead to aspiration
pneumonia

34. Aspiration Pneumonia (medicine )

35. Exogenous Lipid Pneumonia

36. Pneumonia of shipping fever
It is also called respiratory syndrome and
fairly common in young cattle. It is usually
associated with transportation of cattle
from one place to other, from one feed lot
to other feed lot. When animals is
transported, the bacteria normally present
in buccal cavity, drain down to trachea due
to gravitational force. The bacteria grow
and release lipopolysaccharides (LPS) or
endotoxins which initiate very sever

38. Granulomatous inflamation
It is characterized by granulomatous lesions
as a result of chronic inflammation .
Granulomatous infections involving lungs,
like actinomycosis, actinobacilosis,
tuberculosis, histoplasmosis etc. have a
long coarse body react slowly to produce
granulomatous inflammation rather
exudative.

39. Tuberculosis

40. Giant cell in tuberculosis

41. Tuberculosis

42. Aspergillus hyphae

43. Pneumoconiosis
Pneumoconiosis are lung diseases
caused by inhalation and retention of
inorganic dust. It is characterized by
fibrosis and granulomas.eg.
Anthracosis, asbestosis and silicosis

44. Pleuritis
• Secondary to
pneumonia
• Exterior
• Serofibrinous
• Purulent
• granulomatous

45. Pleuritis / pleurisy
• It is inflammation of pleura of lungs. The ordinary
form of pleurisy belong to acute exudative
inflammation. If pleuritis accompanies pneumonia
, then condition is called pleuropneumonia. There
is serofibrinous creamy white exudate& adhesion
between parietal &visceral pleurae. Infection
reaches lungs through blood, lesions such as
bronchopneumonia, aspiration pneumonia or
abscess, penetration of chest wall, penetration of
foreign bodies from reticulum ( hard wear
disease )

46. • Microscopic appearance
• Infiltration with WBCs and other
inflammatory cells ,thickness of pleura
increased many folds, lymphatic become
prominent, fibroblast ,fibrous tissue

47. Hemorrhagic Septicemia
• It is also called pastruelosis .It is caused by
bacterium Pastrella multocida.it is very
common disease of young cattle & buffalo. It
is per-acute disease rarely subacute ,
primarily affect respiratory system .it is
characterized by three lesions
1.Edema of subcutaneous tissue
2.Severe pleuropneumonia
3.Severe gastroenteritis

48. • There is severe edema, petechial
hemorrhages through respiratory
membranes, animal can not breath and
death occur in few hours in acute cases.
• Etiology :pasteurella multocida type B &
E. Most prevalent in tropical & subtropical
areas like Pakistan ,India etc. Primarily a
disease of buffalo .Out breaks are
common in rainy season. Normal
inhabitant of nasopharynx .

49. • Stress factors cause rapid multiplication
and dissemination including septicemia.
High mortality in clinically affected animals
(100%).
• Bacterial toxins are major cause of death.
There is high fever ,profuse drooling
,frothing in mouth. Petechial hemorrhages
on serous membranes .there is acute
fibrino hemorrhagic interstitial pneumonia
.Death caused by asphyxiation .

50. Pathogenesis of HS
• As bacteria are G-ve in nature and
produce LPS which lead to septic shock.
These bacteria are normal inhabitant of
nasal cavity .
• Stress ….. Multiplication ……
LPS/toxins…….hypothalamus……..high
temperature …..fever …..hemorrhages
• Stress may be due to any viral disease,
poor nutrition ,poor housing, weather
stress etc

51. HS in fish

52. Bronchopneumonia
• Cattle
– Pasteurella spp., Actinomyces pyogenes
• Horse
– Streptococcus spp., Rhodococcus equi
• Dog
– Bordetella bronchiseptica, Klebsiella spp.,
streptococci, staphylococci, E. coli
• Cat
– P. multocida and other gram-
• Predisposing causes:
– Transport stress, irratant gases, dust,
congregation of animals, immunodeficient states,
dehydration, chilling, viral infections, anesthesia,
uremia, acidosis

53. • Gross appearance
– Cranioventral portions mostly affected
– Consolidation, emphysema, congestion,
atelectasis
• Microscopic appearance
– Bronchioalveolar junctions
– Cell debris, mucus, fibrin, macrophages
– Epithelium – necrotic to hyperplastic
– Capillaries engorged
– Chronic suppuration and fibrosis, particularly in
cattle

54. Lobular Pneumonia

55. Lobar Pneumonia
• Whole or part of the lobes is uniformly affected
• Fulminating and often aggressive form of
bronchopneumonia – uniform appearance
• Pasteurella hemolytica, Hemophilus somnus,
Acinobacillus pleuropneumoniae, streptocococci,
Rhodophilus equi
• Aspiration pneumonia
• Fibrinous
• Congestion, Red hepatization, grey hepatization,
Resolution
• Pleuritis and pericarditis may be cause of death

56. Interstitial Pneumonia
• Viral pneumonia, chemicals, shock,
septicemia, high concentration of oxygen
used as therapeutic agent
• Acute respiratory distress syndrome
• Great involvement of dorso-caudal region
• Blood born insult in most of the cases

57. Cont…..