AN importent disease affecting our livestock industry in INDO PAK region

1. HAEMORRHAGIC SEPTICAEMIA
Aetiology,Epidemiology,Diagnosis andPrevention
AETIOLOGY
Pasteurella multocida.Order:Pasteurellales.Family:Pasteurellaceae
The disease iscausedbycertainserotypesof Pasteurella multocida,aGram-negative
coccobacillus residingmostlyasacommensal inthe nasopharynx of animals. The AsianserotypeB:2
and the Africanserotype E:2correspondingtothe newer6:B and 6:E classificationare mainly
responsible forthe disease
Otherserotypes,namelyA:1,A:3,have beenassociatedwithaHS-like conditionincattle and
buffaloesinIndiawithmainlypneumonialeadingtodeath. The letterdenotesthe capsularantigenand
the numberstandsfor the somaticantigen
Resistance to physical and chemical action
P. multocidaissusceptibletomildheat(55°C),mosthospital disinfectantsand cansurvive forhoursand
probablydaysinthe moistsoil and water.
EPIDEMIOLOGY
Haemorrhagicsepticaemia(HS) isa majordisease of cattle andbuffaloescharacterisedbyanacute,
highlyfatal septicaemiawithhighmorbidityandmortality
In manyAsiancountriesHSdisease outbreaksmostlyoccurduringthe climaticconditionstypical of
monsoon(highhumidityandhightemperatures)
Hosts
Cattle andwater buffaloes(Bubalusbubalis) are the principal hostsof hemorrhagicsepticaemia,anditis
widelyconsideredthatbuffaloesare the more susceptible,insheep,goatsand swine;itisnota frequent
or significantdisease.Infrequentcaseshave beenreportedindeer,camels,elephants,horses,donkeys
and yaks.
Laboratory rabbitsandmice are highlysusceptibletoexperimental infection
There are noreportedcasesof humaninfection Cattle,waterbuffalo,andbisonappeartobe the
reservoirsof infection
Transmission
P. multocida istransmittedby directcontactwithinfectedanimalsandonfomites
Cattle and buffalobecome infectedwhentheyingestorinhale the causativeorganism, whichprobably
originatesinthe nasopharynx of infectedanimals.Inendemicareas,upto5% of cattle and waterbuffalo
may normallybe carriers.The worstepidemicsoccurduringthe rainyseason,inanimalsinpoorphysical
condition.Stressessuchasa poorfoodsupplyare thoughtto increase susceptibilitytoinfection,and
close herdingandwetconditionsseemtocontribute tothe spreadof the disease
P. multocida can survive forhoursand possiblydaysindampsoil orwater;viable organismsare not
foundinthe soil or pasturesafter2–3 weeks. Bitingarthropodsdonot seemtobe significantvectors
Sources of the agent
Blood:septicaemiainHSoccurs at the terminal stage of the disease,therefore,bloodsamplestaken
fromsick animalsbefore deathmaynotalwayscontain P.multocida organisms
Nasal secretions: organismsare alsonot consistentlypresentinsickanimals
Occurrence
Hemorrhagicsepticaemiaisanimportantdisease inAsia,Africa,some countriesinsouthernEurope,and
the Middle East.It has neverbeenconfirmedinMexico,Central orSouthAmerica
DIAGNOSIS
Some characteristicepidemiologicandclinical featuresaidinthe recognitionof HS.Of particular
significance isahistoryof earlieroutbreaksandarecentfailure tovaccinate
Sporadiccasesare more difficulttodiagnose clinically

2. The seasonof the year,rapidcourse,and highherdincidence,withfeverandoedematousswellings
indicate typical HS. Characteristicnecropsylesionssupportthe clinical diagnosis;confirmationrequires
the isolationandcharacterisationof the pathogenusingconventional andmoleculartechniques
The incubationperiodvariesfrom3–5 days.
In experimental infectionswithlethal doses,cattle orbuffalodevelopclinicalsignswithinafew hours
and die within18–30 hours. Morbiditydependsonimmunity andenvironmental conditions,including
bothweatherandhusbandry;morbidityishigherwhenanimalsare herdedclosely,inpoorcondition,or
exposedtowetconditions. Mortalityisnearly100% unlessthe animal istreatedveryearlyinthe
disease;few animalssurvive once theydevelopclinical signs.
Antibiotictreatment is effective ifit is started very early,duringthe pyrexic stage. Variousvaccines
can provide protectionfor6–12 months
Clinical diagnosis
Acute or per acute;A fever,dullness, andreluctancetomove are the firstsigns.Salivationandaserous
nasal discharge develop,andoedematousswellingsbecome apparentinthe pharyngealregion;these
swellingsspreadtothe ventral cervical regionandbrisket. Mucousmembranesare congested
Respiratorydistressoccurs,andthe animal usuallycollapsesanddies6–24 hoursafterthe firstsignsare
seen.Eithersuddendeathora protractedcourse up to 5 days isalsopossible.Animalswithclinical
signs,particularlybuffalo,rarelyrecover. Chroniccasesdonot seem to occur
Buffaloesare generallymore susceptible toHSthancattle and show more severe formsof disease with
profoundclinical signs. Inendemicareasmostdeathsare confinedtooldercalvesandyoungadults
Massive epizooticsmayoccurin endemicaswell asnon-endemicareas. Inthe recentpast,HS has been
identifiedasasecondarycomplicationincattle andbuffalosfollowingoutbreaksof footandmouth
disease (FMD).Case fatalityapproaches100% if treatmentisnotfollowedatthe initial stage of infection
Lesions
Widespreadhaemorrhages,oedema,andhyperaemia,consistentwithsevere sepsis. Oedemaconsists
of a coagulatedserofibrinousmasswithstraw-colouredorbloodstainedfluid. Swellingof the head,
neck,and brisketoccursinnearlyall cases.Similarswellingscanalsobe foundinthe musculature
Subserosal petechial haemorrhagesmayoccurthroughoutthe body,and the thoracic andabdominal
cavitiesoftencontainblood-tingedfluid Scatteredpetechiae maybe visible inthe tissuesandlymph
nodes,particularlythe pharyngeal andcervical nodes;thesenodesare oftenswollenandhemorrhagic
Pneumoniaorgastroenteritisoccasionallyoccurs,butusuallyisnotextensive.
Atypical cases,withnothroat swelling andextensive pneumonia,are sometimesseen. Thereare no
microscopicfeaturesthatare specificforhemorrhagicsepticaemia –all lesionsare consistentwith
severe endotoxicshockandmassive capillarydamage
Differential diagnosis
ShippingfeverisoftenmistakenlyconfusedforHS,buthas a multifactorial aetiology(oftenMannheimia
haemolytica),isnotsepticaemic,anddoesnotcause multisystemicpetechial haemorrhages
The peracute nature of the disease andthe extensive oedemaandhaemorrhage make itdifficultto
differentiatefromblacklegandanthrax.
Acute salmonellosis,mycoplasmosis,andpneumonicpasteurellosisshouldalsobe considered
Laboratory diagnosis
Samples
P. multocida isnot alwaysfoundinbloodsamplesbefore the terminal stage of the disease,andisnot
consistentlypresentinnasal secretionsorbodyfluidsof sickanimals. Infreshlydeadanimals,a
heparinisedbloodsampleorswabshouldbe collectedfromthe heartwithinafew hoursof death,and a
nasal swab. A longbone shouldbe takenfromanimalsthathave beendeadfora longtime.Other
visceral organsmayalso be sampled if anecropsyisnot feasible,bloodsamplescanbe takenfromthe

3. jugularveinbyaspirationorincision;bloodsamplesshouldbe placedinastandardtransportmedium
and transportedonice packs.Spleenandbone marrow provide excellentsamplesforthe laboratory,as
these are contaminatedrelativelylate inthe post-mortemprocessbyotherbacteria. Tipsof ears(from
live animal only)
Procedures
Identificationofthe agent
Serological tests
Serological testsare notnormallyusedfordiagnosis;however,hightitres(1:160or higherby indirect
haemagglutination) insurvivingin-contactanimalsare suggestive of the disease
For more detailedinformationregardinglaboratorydiagnosticmethodologies,
PREVENTION AND CONTROL
Sanitaryprophylaxis
Vaccinationisroutinelypracticedinendemicareas.Avoidingcrowding,especiallyduringwetconditions,
will alsoreduce the incidence of disease.
Medical prophylaxis
Antimicrobialsusceptibilitytesting(AST) isparticularlynecessaryfor P.multocida forwhichresistance to
commonlyusedantimicrobial agentshasoccurred
The followingagentshave proventheirclinical efficacy:penicillin,amoxicillin(orampicillin),
streptomycin,gentamicin,spectinomycin,florfenicol,tetracycline,sulfonamides,
trimethoprim/sulfamethoxazole,erythromycin,andnorfloxacin
Inactivatedvaccines
Vaccination is routinely practiced in endemic areas
Three preparationsare used – dense bacterinscombinedwitheitheralumadjuvantoroil adjuvant,and
formalin-inactivatedbacterins;the oil adjuvantbacterinisthoughttoprovide protectionforupto one
yearand the alum bacterinfor4–6 months
Maternal antibodyinterfereswithvaccine efficacyincalves
Live attenuated vaccines
A live HSvaccine preparedusinganavirulentP.multocidastrainB:3,4(Fallow deerstrain) hasbeenused
for control of the disease incattle andbuffaloesover6monthsof age inMyanmar since 1989; it is
administeredbyintranasal aerosol application(atrial of the vaccine hasbeencompletedinIndonesia).
PUBLIC HEALTH
There are noconfirmedreportsof humaninfectionswithP.multocidaserotypesB:2andE:2; however,
otherserotypesdocause humaninfectionsandprecautionsshouldbe takentoavoidexposure