59 – Pneumonias of horses

Glanders (farcy, malleus)

Topics – morphological categorization

• (Broncho)interstitial pneumonia– equine influenza, EHV-1, EHV-4 infection

• Bronchopneumonia– catarrhal-purulent bronchopneumonia

– fibrinous bronchopneumonia, pleuropneumonia• Streptococcus equi ssp. equi, ~ zooepidemicus; Bordetella

bronchiseptica, Klebsiella pneumoniae, Staphylococcus sp.

– necrotic/gangraneous bronchopneumonia• aspiration pneumonia

• Focal/multifocal pneumonia– septic thromboembolism related pneumonia

• (Pyo)granulomatous pneumonia– Rhodococcus equi infection

– glanders (Burkholderia mallei infection)

– fungal pneumonias• aspergillosis, pneumocystosis

(Broncho)interstitial pneumonia

• Equine influenza

– Type A virus, two subtypes

• A/equi/2 – H3N8; A/equi/1 – H7N7

– Clinical signs

• Coughing, serous to purulent oculonasal discharge,

fever, weakness

• Rarely sytemic involvement and death

– Lesions

• Hyperemia, focal erosions in the upper respiratory tract

• Bronchointerstitial pneumonia

– edema

– necrosis of bronchiolar epithelium

– secondary bacterial pneumonia

Interstitial pneumonia

EIV infection, donkey

(Broncho)interstitial pneumonia

• Equine herpesviruses (EHV-4, EHV-1)– Mild upper respiratory signs

– Secondary bacterial bronchopneumonia

– Systemic lesions in neonates!

• Rhinovirus, reovirus, equine arteritis virus, adenovirus– similar clinical signs and lesions

– predisposing factors for heaves (COPD)?

• African horse sickness– severe edema, vascular damage (Reoviridae, Orbivirus)

• Hendra virus– syntitial giant cells (Paramyxoviridae, Morbillivirus)

• Clamydophila psittaci

• Idiopathic proliferative interstitial pneumonia– sequel: pulmonary fibrosis, toxicosis / viral infection?

Pulmonary fibrosis, horse

Bronchopneumonia

• Catarrhal-purulent pneumonia

• Fibrinous (pleuro)pneumonia

– cranioventral consolidation

– predisposing factors

• stress, viral infections etc.

– secondary bacterial infection

• Streptococcus equi ssp. equi, ~ zooepidemicus;

Bordetella bronchiseptica, Klebsiella pneumoniae,

Staphylococcus sp.

Chronic purulent bronchopneumonia, horse

Bronchopneumonia

• Necrotic/gangrenous pneumonia

– aspiration pneumonia• anatomical predisposition

– „tracheal puddle”

• iatrogenic– nasogastric tubing

• CNS involvement!!!!!!!!– rabies, WNV or other viral encephalitides, lead

poisoning, fumonisin toxicosis etc.

– usually unilateral, foul smell, rapid autolysis, necrosis predominates, mixed bacterial flora

Aspiration pneumonia

Aspiration pneumonia, horse

Pyogranulomatous pneumonia

• Rhodococcus equi infection

– Rhodococcus equi• Facultatively intracellular bacterium, complex lipids

in its cell wall

• Normal inhabitant of soil and intestinal tract of different species

• Disease in foals of 1-6 months of age

• Pathogenesis is incompletely understood

– Clinical signs• Fever, cough, nasal discharge, increased

respiratory rate

• High mortality

Pyogranulomatous pneumonia

• Rhodococcus equi infection

– Lesions• Lungs and tracheobroncial lymphonodes

– Multiple large, firm nodules of various size

– Caseation necrosis without fibrous capsule formation (not a proper abscess!)

– Predominantly pyogranulomatous inflammation

• Intestinal tract– Ulcerative enterocolitis, involvement of mesentarial

lymphonodes

• Arthritis, dermatitis, hepatitis, vertebral osteomyelitis, ulcerative lymphangitis

Rhodococcus equi pneumonia, horse

Rhodococcus equi pneumonia, horse

Rhodococcus equi pneumonia, horse

Granulomatous pneumonia

• Mycobacteriosis

–Mycobacterium avium complex

–Mycobacterium tuberculosis

–Mycobacterium bovis

• Predominantly proliferative

tuberculosis

Granulomatous pneumonia

• Fungal pneumonias

–Pulmonary aspergillosis

• secondary to mucosal damage

– intestines! ulcerative fungal colitis

• systemic lesions

–brain, lungs, skin

• severe disseminated fibrinonecrotic to

granulomatous pneumonia

Pulmonary aspergillosis, horse

Pulmonary aspergillosis, horse

Pulmonary aspergillosis, horse

Granulomatous pneumonia

• Fungal pneumonias

– Pneumocystosis

• Pneumocystis carinii fungus

• Secondary to immunosuppressive agents / immunodeficiencies

– SCID

– Viral infections, Rhodococcus equi inf.

• Histological diagnosis– foamy structure within alveoli

– Gömöri’s Methenamine Silver stain (GMS)

– minimal inflammatory changes

Pneumocystosis, H-E stain

Pneumocystosis, GMS stain

Pyogranulomatous pneumonia

• Glanders (malleus, farcy)

• Burkholderia mallei– Gram-negative, obligate aerobic, nonmotile,

obligate pathogen

– Zoonotic agent, bioterrorism!

• Occurrence– Asia, North-Africa, (far-far) East-Europe (?),

South-and Central America

• Susceptible species– Equidae (solipeds), carnivores, guinea-pig,

hamster, goat, man

Glanders - history

• 3rd Century BC

– Described by Aristotle

• 1664: Contagious nature recognized

• 1830: Zoonotic nature suspected

• 1891: Mallein test developed

• 1900: Control programs implemented

Glanders - history

• World War I

– Suspected use as biological agent to infect

Russian horses and mules

• Affected troops and supply convoys

– Large number of human cases in Russia

during and after WWI

Glanders - history

• World War II

– Japanese infected horses, civilians and POW’s

– U.S. and Russia investigated use as biological

weapon

Glanders

• Way of infection

– per os

• contaminated feed, water, carcasses of

infected dead animals

– percutaneous or conjunctival, aerogenical

– asymptomatic carriers

Glanders

• Pathogenesis

– the disease develops through several

successive stages, each is characterised

by distinctive clinical signs and lesions

– outcome depends on the immunological

status of the host

– p. os uptake: primary complex in the

alimentary tract

• early generalisation: lungs, spleen, liver etc.

• late generalisation: septicaemia, nasal mucosa,

skin

Glanders

• Incubation time– Few days to several months

• Clinical forms and signs– Acute form

• donkeys, mules, certain horses, carnivores, (man)

• coughing, fever, nasal discharge

• septicaemia, (pyemia), bronchopneumonia, death in days

– Chronic form• certain horses, mules, (man)

• granulomatous changes in the lungs, in the nasal mucosa, in the skin

• subclinical infection does occur (mallein-test)

Glanders,

intradermo-palpebral test

Glanders,

Strauss reaction,

male guinea-pig

Draining fistulous tracts

in the skin

Glanders, nasal and dermal lesions

Glanders

• Lesions– Different lesions might be present in the

same animal• Lungs

• Nasal mucosa, paranasal sinuses, lips

• Skin (lymphatics)

• Lymphonodes

• Testicles, liver, spleen

• Basic forms of lesions– Malleotic nodule (granuloma)

– Predominantly exsudative form

– Predominantly proliferative form

Malleotic nodule

• Exsudative development– pathogen in the centre, surrounded by PMNs,

exsudation and hyperemic ring around

– later histiocytes and giant cells appear

– the center becomes necrotized, fibroblasts appear on the perimeter

• Proliferative development– pathogen in the centre, surrounded by

epitheloid cells and giant cells

– more epitheloid cells accumulate

– the center becomes necrotized, fibroblasts appear on the perimeter...

Malleotic nodule

• Developed malleotic nodule

– pyogranuloma with narrow demarcation zone

• colliquated or caseous centre with occassional calcium salt deposition, surrounded by epitheloid cells, giant cells and granulation tissue

• poppy seed to pea sized nodules with

greyish-yellow dry or liquid centre

Malleotic nodule, lung

Malleotic nodules, nasal septum, horse

Malleotic ulcer

• Malleotic ulcer– nodules close to the surface

• mucous membranes, skin– nasal cavity, trachea, larynx

– necrosis, shedding of the necrotized part

– shallow to deep erosions – ulcers• uneven margin

• undermined edge

• covered with egg-white like material

– healing with scar formation

„Farcy”,

ulcerative lymphangitis

Different stages of malleotic nodules and ulcers, nasal septum, horse

Malleotic ulcer on the lip,

donkey

Malleotic nodules and ulcers, nasal septum, horse

Chronic malleotic ulcers, nasal septum, horse

Chronic malleotic ulcers, nasal septum, horse

Predominantly exsudative glanders

• Lungs, other tissues

– serofibrinous inflammation around the pathogen

• bronchopneumonia

– necrosis with caryorhexis, colliquation

– healing with proliferation of malleotic granulation tissue

• may contain dry areas with calcium deposits

Disseminated pyogranulomas, bronchopneumonia

Thrombosis, necrotizing rhinitis

(„Zahn-lines” in the thrombus)

Fibrinous vasculitis

Predominantly proliferative glanders

• Mucous membranes

– proliferation of malleotic granulation

tissue

• fibroblasts

• histiocytes, giant cells

– barley seed sized greyish-white firm

nodules on mucous membranes

Proliferative malleotic nodules, trachea, horse

Glanders

• Differential diagnosis

– Strangles• Streptococcus equi ssp. equi

– Epizootic lymphangiitis • Histoplasma sp.

– Ulcerative lymphangiitis• Corynebacterium pseudotuberculosis

– Melioidosis• Burkholderia pseudomallei

– Blastomycosis, cryptococcosis• Blastomyces sp., Cryptococcus sp.

Rhodococcus equi enterocolitis

• Ubiqitous bacterium, common in animal manure

• Gram-positive, partially acid-fast, facultatively intracellular organism

• Potentially zoonotic – HIV!

• Clinical disease in foals under 6 months– Predisposing factors

• helminthiasis,

• immunosuppression,

• immunodeficiency

• Sporadic or endemic occurrence

Rhodococcus equi enterocolitis

• Intestinal tract– Pyogranulomatous ulcerative enterocolitis

• Macrophages, giant cells proliferate in the propria– intracellular organism!

• Coagulation necrosis, epithelial ulceration

• Pyogranulomatous lymphadenitis

• Other organs– Subcutaneous abscesses, purulent lymphadenitis,

suppurative arthritis, pleurisy, suppurative pneumonia with abscessation, purulent osteomyelitis

Rhodococcus equi colitis, horse

Rhodococcus equi colitis, horse

Rhodococcus equi colitis, horse

Rhodococcus equi colitis, horse