Dr. Pavulraj.S5246

M.V.Sc., ScholarDivision of Pathology

Indian Veterinary Research Institute, Izatnagar, India

Introduction

• Horse – a symbol of bravery and power

• Total population of equids in India is 1.18 million(2007)

– Horses – 52%

– Donkey – 37%

– Mule – 11%

• In India, diseases like glanders and equine influenza re-emerged

among equines in 2006-09

• There are many bacterial and viral diseases are endemic in India

• Many new emerging diseases threatening our equine health

List of diseases

Viral diseases• Hendra• Equine influenza• Equine herpes virus• Equine infectious

anemia• African horse

sickness • Equine viral arteritis• West Nile fever• Equine encephalitis• Rabies

Bacterial diseasesGlandersStranglesTetanus Rhodococcus equiLeptospirosisBotryomycosis

Hendra

• Acute febrile respiratory infection of horses

• Characterized by increased respiratory rate, profuse nasal

discharge, jaundice and neurological signs with fatal outcome

• Paramyxoviridae – genus Henipavirus (equine morbilivirus), don’t

agglutinate RBC

• Horses – only species naturally infected

• Fruit bat – Pteropus Sp., reservoir host

• Zoonotic

• First recognized in 1994, caused acute respiratory disease

Vanarsa Guillaume et.al.,

50% seroprevalence of HeVantibodies in flying foxes in Australia

Satellite telemetry hasshown that old world fruitbats can travel more than2000 km in 1 year

Epidemiology • Low transmission rate – not persist in environment for long time

• I.P – 5 to 10 days, disease last for 2 days

• Low morbidity, high mortality

• BSL-4 pathogen

• Human infection form infected horse

• Horse – nasopharynx inoculation. Shed virus in urinary tract

Pathogenesis

• Pneumotropic and neurotropic virus

• Animal and human died after showing resp. signs

• Virus isolated from all the organs of the body including

blood

• Affect vascular endothelium – cause pulmonary edema

• Lesions in lung and brain – similar to CD, measles

Vanarsa Guillaume et.al.,

Clinical signs

• Pyrexia, dyspnea, frothy/haemorrhagic nasal discharge, neurological signs,

ataxia, muscle trembling

Lesions

• Diffuse pulmonary edema and congestion

• Hydrothorax and hydropericardium

• Congestion of LN, S/C hemorrhages

Mic

• Interstitial pneumonia, alveolar edema, necrosis of alveolar walls and

thrombosis of blood vessels, Non suppurative encephalomyelitis

• Vascular lesions in visceral organs

• Syncytial cells in blood vessels – unique featureVanarsa Guillaume et.al.,

Interlobular edema Petechial hemorrhages over lung

Brain vasculitis ovary vasculitis Lymphadenitis with syncytial cell formation. IHC staining of HeV N protein

Equine influenza

• “Flu” or “two-year-old cough”

• Highly contagious respiratory viral disease of equines

• RNA virus – Influenzavirus A – family Orthomyxoviridae

• Two subtypes viz. H7N7 and H3N8

• H3N8 spreads very rapidly, cause severe clinical disease

• Characterized by pyrexia, dyspnea, dry hacking cough,

serous nasal discharge, edema of LN

• Re-emerged in India in last week of June, 2008 in Jammu

and Kashmir, 20 years after the first outbreak in 1987

• Entered to india by importing army horses for France

Vandanajay Bhatia et. al.,

Nithin virmani et. al.,

Current status(2008-09)

Nithin virmani et. al.,

Transmission

• Short I.P - <48hrs

• Morbidity – 60-90%

• Mortality - <1%

• Outbreak – close contact

• Direct contact – nasal secretion - Droplet

infection

Pathogenesis

Attachment of virus to airway epithelial

cells(HA to Sialic acid residue)

Receptor mediated

endocytosis

Acidification of endosomal

compartment

Conformational change of HAFusion of viral

and cellular membrane and release of RNP

Entry of RNP into nucleus

Synthesis of viral proteins

Assembly and release

Inhalation

Ljubo Barbic et.al.,

Pathogenesis

Lesions

• Inflammation of resp tract

• Erosion of upper respiratory mucosa

• Pulmonary consolidation, pneumonia

• Myocarditis

Mic

• Hyaline membrane formation on

bronchiolar and alveolar epithelium

• Peribronchitis, bronchitis,

bronchopneumoniaLjubo Barbic et.al.,

Exudate in the bronchial lumen and infiltration of inflammatory cells in bronchial epithelium and lamina propria

The alveolar architecture is obliterated by the presence of MNC, neutrophils, erythrocytes, and edema fluid in the alveolar lumina.

IHC for equine influenza A virus respiratory tissue

EI in India

• The vaccination against EI is not practiced in India.

• The rise in HI antibodies against EIV, in the naive population in the country

which had not experienced any outbreak since 1987, indicated that the

animals were infected recently with EIV.

• NRCE regularly conducts routine sero-surveillance against infectious

diseases of equines from various parts of the country.

• The occurrence of the EI infection was confirmed in all the places by either

virus isolation or by demonstration of fourfold or more rise in serum HI

antibody titres.

Nithin virmani et. al.,

Equine herpes virus

• Important cause of abortion, neonatal death, respiratory disease and

neurological diseases

• Caused by Equine herpesvirus (EHV1 &EHV4)

• Narrow host range – single target species

• Infect multiple types of cells

• Lytic and latent cycle

• Latency – trigeminal ganglia and CD8+ cells

• EHV-1 - major cause of neonatal foal mortality in a number of breeding

studs located in the Haryana, Punjab and Uttar Pradesh States of India. Tiwari S.C, et al.,

Epidemiology and Transmission

• Horse - to – horse

• Ingestion and inhalation

• Aborted material, semen, aerosol droplet

• Reservoir – latently infected horses

• Stress, transport can reactivate latency

• Less persistent in environment

• Infection acquired in first weak of birth

Pathogenesis

Inhalation

Replicate in upper resp. tract mucosa

In uterus – vasculitis– abortion

Disseminated in all organs including trigeminal ganglion,

CNS, uterus during viremia

Enter to lamina propria, endothelial

cells, CD8+ cells

Brain – vasculitis, thrombo-ischemia,

encephalopathy

Virus

Tiwari S.C, et al.,

Clinical signs

• EHV1 – resp signs, abortion, neurological

signs

• Nasal discharge, conjunctivitis,

lymphadenopathy, no cough

• Abortion – last trimester

• Neonatal infection – fatal

• Stallion – poor semen quality

• CNS – ataxia, paralysis, bladder

dysfunction, incontinence

• EHV4 – resp signs

Neurological form of EHV1

Nasal discharge

Multifocal hemorrhages, rubbery lung

Multiple necrotic foci in liver

Hemorrhage and necrosis of brain stem

Aborted fetus, enclosed in amnion

Lesions

Necrotic foci in liverEosinophilic inclusions in hepatocyte

Vasculitis in CNS

Nuclear debris in splenicfollicle lymphocytolysis

EHV-1 particles nucleus. Organelles of the cytoplasm degeneration hydropic dilation of sER,mitochondria, detached ribosomes of rER

Equine infectious anemia• Swamp fever, Coggins disease

• Equine infectious anemia virus, genus Lentivirus Family Retroviridae

• Contains reverse transcriptase (RNA dependent DNA polymerase)

• Characterized by icterus, anemia, edema of subcutis of ventral abdomen,

thrombocytopenia

• World wide distribution

• Transmitted mechanically by mosquito or biting fly or by infected blood

Maria Teresa Scicluna et al.,

Current status

Transmission

• Blood from infected animal – source of infection

• Mechanical transmission by Tabanus and Stomoxys

calcitrans (with in short time <4hrs, in short distance)

• Vertical transmission – in utero/colustrum feeding

• Venereal transmission – semen

• Iatrogenic – blood contaminated productsMaria Teresa Scicluna et al.,

Pathogenesis

Kidney glomeruli have thickened basement membrane and mesangium with neutrophilicinfiltration and contained deposits of immune complex

Anemia – immune mediated destruction, intra & extra vascular hemolysis

Thrombocytopenia – suppression of platelets production and immune mediated destruction

Increase in proinflammatory cytokines causes fever, lethargy, inappetence

Infection of macrophages induces upregulation of TNFα, IL-1 and IL-6

Active infection of liver, LN, BM, lung, adrenal gland, kidney, brain

Viremia

Virus infect macrophages in spleen, tissue

Maria Teresa Scicluna et al.,

Clinical signs

Pyrexia, edema of lower abdomen, sublingual and nasal haemorrhage

Anaemia, thrombocytopenia

Chronic form develop after the pass of acute form

Lesions

Acute disease

Icterus, haemorrhages on serous membrane

Edema of subcutis of abdomen, base of heart, perirenal and sublumbar fat

Hepatomegaly, splenomegaly, lympadenopathy

Chronic disease

Hypertrophy of spleen and bone marrow

Heart – haemorrhage in epicardium and pericardiumSpyrou et al.,

Enlarged grey red liver showing lobular pattern

Replacement of BM fat with dark red hemopoietic tissue - erythroid hyperplasia

Pale cardiac muscle, focal white areas of myocardial degeneration

Kidney – infracts

Microscopically

Edema, hyaline degeneration and lymphocyte infiltration around blood vessels.

Glomerular nephritis

Liver - lymphocytic infiltration, dilation of

sinusoids, haemosiderin pigment in kupffer

cells, centrilobular necrosis.

Periportal - lymphocytes and plasma cells.

Interface hypereosinophilic hepatocytes

with loss of cellular detail - piecemeal necrosis

Hyperplasia of BMSpyrou et al.,

African horse sickness

• Non contagious, infectious, insect borne disease of equine

• Caused by African horse sickness virus, belong to genus – Orbivirus,

family – Reoviridae, Nonenveloped

• Transmitted by Culicoides spp.

• 9 antigenic serotypes

• Characterized by pyrexia, edema of lungs, pleura, S/C tissue and

hemorrhage of serosa of internal organs

• In 2006 - WOAH declared India free of African horse sickness

Kazeem.M.M et al.,

Epidemiology

• Mortality rate - 70-95%

Transmission

• Not contagious

• Culicoides spp., - biological vector

• Occasional - mosquitoes - Culex, Anopheles and Aedes spp.; ticks - Hyalomma, Rhipicephalus

• Moist and warm temperatures favour the presence of insect vectors

• Virus movement over long distances via windborne infected vectors

Sources of virus

• Viscera and blood of infected horses

• Semen, urine and all shed and secreted products

• Viraemia up to 18 days Kazeem.M.M et al.,

Pathogenesis

Cardiac form (serotype9)- degeneration and necrosis of myocardium, hydropericardium

Foals and naïve horses develop – peracute pulmonary form

Secondary viremia

Primary viremia – disseminate to endothelial cells of target organs – endothelial cell damages

Effusion in body cavities, serosal, hemorrhages

Initial multiplication in regional LN

Inoculation of virus

Gomez J.C. et al.,

Pulmonary & cardiac form

AHS - Foam from nares due to pulmonary edema

Bilateral supra orbital edema –cardiac form Congestion and edema of conjunctiva

Lesions

• Respiratory form: edema of the lungs, froth in trachea, hydro

pericardium, oedema of thoracic LN, petechiae in pericardium

• Cardiac form: S/C and I/M gelatinous edema, epicardial and

endocardial ecchymoses, myocarditis, haemorrhagic gastritis,

petechiae in ventral surface of tongue Gomez J.C. et al.,

AHS - Pulmonary edema (distended interlobular septa)

edema in intermuscular fascia of neck

S/C edema

Petechial hemorrhages on serosa Petechial hemorrhages on the diaphragm

AHS - Hydropericardium Subendocardial hemorrhagesSubcutaneous edema

Microscopically

• Widening of interlobular septa

• Alveolar edema

• Perivasculitis

• Focal myocardial hemorrhage

• Degeneration of myocardial

fibers

Pulmonary edema

Myocardial necrosis

Equine viral arteritis

• Infectious disease

• Caused by Equine arteritis virus belong to genus Arterivirus, family Togaviridae

• Characterized by depression, edema of limbs, intense pink or red conjunctiva, palpebral edema,

enteritis, pneumonic complications and abortions

• Principal lesions is degenerative and inflammatory changes in the endothelium and tunica media

of small arteries

• Serological survey indicate wide spread infection but clinical disease is not that common

• About 80% abortion during clinical disease

• The virus which causes EVA was first isolated from horses in Ohio in 1953

• India – one case in 1989

Holyoak G.R., et al.,

Transmission

• Via respiratory route or by ingestion

• Venereal transmission by stallions

• Tissues and fluids of aborted fetus contained large mass of virus

• Virus shed in the urine Holyoak G.R., et al.,

Pathogenesis

Ocular edema and conjunctivitis (pink

eye)

Excess lachrymation

Urticarial type skin reaction - due to

lesions in blood vessels

Lesions

• Congestion, petchiae in conjunctiva, resp tract and guttural

pouches, S/C tissue

• Hydrothorex, petichae in pleura, heart, pericardium and lungs,

• Ascites

• Enlargement of LN

• Petichae on endocardium, epicardium, mesentery

• Small intestine, caecum and colon oedematous and congested Holyoak G.R., et al.,

Pulmonary hemorrhagesInterstitial pneumonia and emphysema

Enteritis with sub-serosal and sub-mucosal hemorrhages

Microscopically

• Small arteries and necrosis and

deposition of eosinophilic mass in

tunica media with cellular

infiltration in adventitia

• Platelet thrombi in lumen

• Abortion -necrotizing myometritis

West Nile virus: the Indian scenario• West Nile virus - arthropod borne flavivirus

• Causes a mild infection in human and horses

• Mosquitoes are the principal vectors

• Various Culex species - Transovarial transmission

• Very few clinical cases of human encephalitis due to WNV are observed - Neuroinvasive disease

• WNF in horses has not been documented in India.Paramasivam, et al.,

Glanders

• Fatal, contagious and zoonotic disease

• Caused by Burkholderia mallei , Gram -Ve, non-motile, non-

sporulating obligate aerobic

• Acute or chronic form

• Characterized by nodular lesions in the lungs and nodular or

ulcerative lesions in the respiratory tract mucosa and skin

• Occupational disease of veterinarians, farriers and animal

workers

• Last report on glanders outbreak in India - June, 1985,

recently from july, 2006

Purulent nasal discharge

2010

Bazargani T.T, et al.,

Transmission

• Excretions and discharges of affected animals skin and nasal mucosa

• Oral - chronic respiratory disease

• Intranasal - acute disease

• Virulence and immuno-evading factors

– Intracellular status

– Capsule and capsular LPS

– High level of genomic alterations in the host – such rapid genomic variation upregulate

virulence gene expression in B. mallei

– Genomic instability has had impact on vaccine development

• Pathogenesis not fully understood Bazargani T.T, et al.,

Pathogenesis

Oropharynx or intestine

Bacteria penetrate the

mucosa and reach regional LN

Spread hematogenously

to the internal organs and lungs

From nasal cutaneous lesions

Other visceral organs also the sites of typical

nodules

Terminal signs -bronchopneumonia

Death is caused by anoxic anoxia

Clinical signs and lesions

• Acute - cough and nasal discharge, ulcers on nasal mucosa

and nodules on the skin of lower limbs or abdomen.

• Chronic - chronic cough, epistaxis . Nasal and skin form

occur together

• Cutaneous lesions - medial hock

• Lymphadenopathy and cording of lymphatics

• Milliary nodules in lung

Microscopically - pyogranulomatous lesionsBazargani T.T, et al.,

Mucopurulent nasal discharge

cutaneous nodules on legsUlcers and farcy buds along facial lymphatics.

Leg - non-ulcerated farcy buds.

Epistaxis

Enlarged submaxillary LN and nodules rupture, release pus and ulcerate

Nodules of lymphatic vessel tracts in cervical region

Nodules in nasal mucosaLungs numerous gray, hard, small (2-10 mm) milliary nodules (resembling millet seeds)

Erosion in nasal mucosa

Necrosis and inflammation of nasal mucosa and thrombosis of nasal vessels

Vessel wall infiltrated by degenerate neutrophils and fibrin

Nodules with necrotic debris, hemorrhage, epithelioid macrophages, neutrophils

Pyogranulomatous central necrosis

Strangles

• Acute infectious disease of horses - Equine

distemper

• Caused by the bacterium Streptococcus equi

sub-species equi (S. equi)

• Characterized by abscess in pharyngeal and

maxillary LN, pericarditis, pleuritis,

suppurative pneumonia, presence of

abscesses on liver, kidney and spleen

Andrew S.Waller et al.,

Pathogenesis

Attach to cells of crypts of lingual and palatile tonsils

Mandibular and suprapharyngeal LN

Failure of N to kill ( due to hyaluronic acid capsule, antiphagocytic SeMproteins, Mac proteins

Bacterial enzymes –Streptolysin, Streptokinase –cause abscess formation ( By damaging cell membrane and activating plasminogen

Spread to other organs

Abscess in LN, thorasic and abdominal organs – Bastard strangles

Andrew S.Waller et al.,

Guttural pouch empyema

• LN swell, abscess and rupture either externally through the horse’s skin

• In retropharyngeal LN, usually internally into the guttural pouch.

• This air-filled sack is an enlargement of the eustachian tube that drains

into the nasal cavity.

• Drainage of abscess material into the nasal cavity from the guttural pouch

contributes to the mucopurulent nasal discharges commonly observed

during strangles.

• Residual pus becomes inspissated to form chondroids

Edematous swelling of pharyngeal region

Rupture of submandibular abscess

Guttural pouch empyema

Acute suppurative lymphadenitis

Bastard strangles – mesentric LN

Metastatic abscess (brain)

Tetanus

• Tetanus - lockjaw caused by exotoxins produced

by Clostridium tetani, motile, anaerobic, G+ve

bacilli

• Soil/intestinal inhabitant

• Horse – most sensitive animal to toxin

• Associated with deep puncture wound, naval

stump infection in foals

• Reduced oxygen tension promote the growth

Shoeing

Peter Reichmann, et al.,

Pathogenesis

• Two toxins – tetanolysin, tetanospasmin

Peter Reichmann, et al.,

Clinical signs

• I.P – 7-10days

• Rigidity of muscles around head and neck

• Trismus

• Prolapse of nictitating membrane

• Rigidity extend to limbs, elevated tail

• Saw horse

• Death due to asphyxia

Lesions

• Intramuscular hemorrhages, tendon avulsion, fracture of

long bones, aspiration pneumonia

Rhodococcus equi

• Causes disease in young foals

• Pyogranulomatous pneumonia

• Pleomorphic, aerobic, non-motile, G+ve,

intracellular pathogen

Pathogenesis

Organism multiply in macrophages R.equi activate

alternate pathway of complement and bind

to macrophage complement receptor

– CD3Large number of cells attracted –

granuloma formation - pneumonia Enter in to

macrophage through complement

receptor mediated phagocytosis

Phagosome –Lysosome fused, due

to lack of acidification –

organism multiply and kill host cell

Lesions

Mesentric lymphadenitis Multifocal ulcerative colitis

Subcapsular splenic abscessesMultiple firm nodules in lung

About NRCE

• NRCE has contributed a great deal towards diagnosis/management/ elimination of

diseases like

• Equine influenza outbreaks in India during 1987-1989 and 2008-2009

• Equine infectious anaemia 1991-1998

• Glanders outbreaks during 2006-2007, 2010, and in 2011-12.

• NRCE involved in nation-wide monitoring and sero-surveillance of important

equine infectious diseases with a view to manage, control and eradicate diseases

• Performing molecular characterization of equine pathogens

• Preparation of diagnostic kits for equine diseases

• preparation of vaccines against equine diseases

Seroprevalence of various equine diseases in India 2010-11 (NRCE)

Conclusion

• Many diseases are emerging and re-emerging in these days

• Understanding the pathogenesis, molecular characterization of the organism and

epidemiology of these diseases are very important for the implementation of

preventive and control measure.

• Spreading of diseases in the farm can be effectively prevented by good biosecurity

measures.

• Surveillance and monitoring of important equine diseases including emerging and

existing diseases is needed to avoid production losses

• Development of effective, affordable diagnostics and immunoprophylactics against

important diseases threatening equines in India