Dimorphic fungi

Importance of Dimorphic fungi in Veterinary.

1. DIMORPHIC FUNGI
Dr.RashmiL
Assistant Professor
Department of Veterinary Microbiology
Veterinary college,Gadag.

2. DIMORPHICFUNGI
Blastomyces
Coccidioides
Histoplasma
Sporothrix

3. Blastomyces

4. Blastomycesdermatitidisindogsandhumans.
Source:soilenrichedwithdecayingorganicmaterials.
(buddingyeast)
Epidemiology:PrimarilyNorthAmericawithsporadiccasesreportedfromIndia,
AfricaandtheMiddleEast.
ClinicalSigns:
•Acutepulmonarydiseasewithcough,pleuriticpain,chills,andlow-gradefever.
•Chronicpulmonarydiseasewithproductivecough,fever,weightloss,
dyspnoea,andfatigue.
•Disseminationtoskin,boneandgenitourinarytractmayalsooccur.
Lesions:pyogranulomatouspneumonia,pleuritis, peritonitis, and cutaneous
abscessation.

5. B.dermatitidisdoes not remain viable for lengthy periods in clinicalmaterials
sofungal cultures should be initiatedimmediately.
Colonies range from flatand glabrousto cottony white or tan, and may have
concentricrings.Aerialmycelia, may be evident within 1 week. Older cultures
become brownish tan with a reverse tan pigment.
Treatment:Amphotericin B or Ketoconazole.

6. COCCIDIOIDES IMMITIS

7. Coccidioidomycosisisusuallyabenign,inapparent,ormildlysevereupper
respiratoryinfectionthatresolvesnaturally.
Onoccasion,thediseasemaybecomeanacuteorchronic,disseminating,fatal
mycosis.
Theetiologicagent,Coccidioidesimmitis,isthemostvirulentofthefungal
pathogens.Inhumansitmayremainviableinlesionsforupto15years’
postinfection.
ItisendemicinthesoilsoftheSouthwestUnitedStatesandCentralSouth
America.
Duststormsincreasetheincidenceofdisease.

8. Speciesaffectedaredogs,horse,cats,swine,sheep,cattle,humanand
nonhumanprimates,andsome30speciesofnon-domesticmammals.
Inthesoil,C.immitisisamouldmadeupofslenderseptatehyphaethatgive
rise,thickersecondarybranches,tochainsofinfectiousarthroconidia
(arthrospores,arthroaleuriospores,arthroaleurioconidia).
Thesearebulging,thick-walledcells,separatedbyemptycells,throughwhich
breaksoccurwhenarthroconidiaaredispersed.

9. Intissue,arthroconidiagrowintosphericalsporangiawithbirefringentwalls,
"spherules",whichbyinternalcleavageproduceseveralhundred"endospores".
Thewallsdisintegrate,allowingdisseminationofendospores,eachofwhich
mayrepeatthecycleor,onanonlivingsubstrate,giverisetomycelialgrowth.
Thoughonlyarthroconidiaarenaturallyinfectious,endosporescan
experimentallyinitiatedisease.Sexualsporesarenotknown.

10. Culturecharacter
OnSabouraud'sorbloodagar,at25°Cor37°C,1-2weeksamoistwhite
colonydevelopsthatlateriscoveredwithafluffymycelium.
Bovinebloodagarishemolyzed.
Arthroconidiaareproducedin5to7days.Themycelialformofthisorganism
isextremelydangerous,henceculturesaretubedthanplating.
Mycelialgrowthshouldbeevidentwithinaweekandisexaminedforpresence
ofarthroconidiainalactophenolcottonbluewetmount.

11. Theisolatecanbereconvertedtothesporangialphasebyanimalinoculationor
cultivationinaspherulemedium.
Thesporangialphaseisproducedat40°Cinmediacontainingcaseinhydrolysate,
glucose,biotin,glutathioneandasaltmixture.
Arthroconidiaresistdryingandtolerateheatandsalinitybetterthandocompeting
soilorganisms.
Diagnosis:ExaminationofspherulesinexudatesbyKOHmountmethod.
LatexagglutinationandComplementfixationtest.
Coccidioidin:FiltrateofC.immitisbrothcultures,largelypolysaccharide,but
containssomeaminoacidnitrogen.Itisusedincutaneoushypersensitivityand
serologictests.

12. HISTOPLASMA

13. HistoplasmosisorDarling’sdiseaseorreticuloendothelialcytomycosis.
Histoplasmosisisachronic,granulomatousdiseasecausedbyHistoplamsa
capsulatumvarcapsulatum.
Histoplasmacapsulatumvar.farciminosumis the cause of the subcutaneous
mycosis and epizooticlymphangitisin horses and mules.
Theorganismsbecomeheavilyconcentratedinthefecesofbirds(particularly
blackbirds,seagulls,starlingsandpigeons);batsarealsoimportantvectorsofthis
disease.Thus,thefungushasbeenisolatedfromsoilinbatcaves,chickenhouses,
andsilosinhabitedbypigeons.
Theorganismsarefacultative,intracellularparasitesofmacrophages.
Infectionusuallyoccursthroughinhalationofsporesofthedimorphicfungus.
Histoplasmosismayoccurcommonlyinanimalsinendemicareas.

14. ThetissueformcellsofH.capsulatumvar.capsulatumappearassmall,oval
yeastcellswithorwithoutbuds.
Daughtercellsareattachedtomothercellsbyanarrowattachmentpoint.

15. H.Capsulatum-Sabouraudagarwith
chloramphenicolbutwithoutcycloheximideat
25°Coronbrainheartinfusionagarwithbloodat37°C.
At25°C,themycelialphasehastwotypesofconidia:
small,roundmicroconidiaandlarge(7-18µm)
thick-walled,macroconidiawithknob-likeprojections.
Theyeastphasegrowsat37°Conbloodagar.
EndemicinAmerica,partsofAfricaandAsia.RareinAustraliaandEurope.
Dogsareparticularlysusceptible,butthediseasehasalsobeenreportedincattle,
cats,swine,horses,sheepandwildanimals.
Thediseasehasnotbeenreportedinbirds.Histoplasmacapsulatumisnot
contagious.

16. Thediseasemayvaryfromsmallgranulomatousnodulestoanacute,
disseminating,rapidlyfatalform.
Usually,thediseasemanifestsitselfeitherasapulmonaryorintestinal
infection,andmaybeinapparentorsubclinical,mild,acute,chronic,or
disseminated.
Ulcerationsandtuberculosis-typelesionsmayoccurinmanyoftheorgan
systems.
Followinginhalationofspores,macrophagesphagocytizetheorganismsandan
inflammatoryresponseensues.
Thefungusiseitherkilled,orlocalgranulomasformwithcalcification.
Hostimmunityandthenumberofsporesinhaleddeterminewhichformthe
diseasemanifests.

17. Themacrophagesmaycarrytheorganismstovariousbodysitesandactuallyhelp
todisseminateit.Thus,histoplasmosishasbeenreferredtoasadiseaseofthe
reticuloendothelialsystem.
Enlargementoftheliverandspleen,andnodulesonthetongue,ocular
involvement,andabortionhavealsobeenreported.
Clinicalsigns.
Mostinfectionsareasymptomaticorbenignandselflimiting.
Symptomaticformswithfever,nightsweats,weightlossandhemoptysis.
Indisseminatedcaseshepatomegalyandsplenomegalydevelop,withanemiaand
leucopenia.
Chronicpulmonaryinfectionsassociatedwithcough,dyspnea,chestpain,
hemoptysisandweightloss.

18. Lesions
Epithelioidandgiantcellgranulomasofthelungarecharactersitic.
Invasionofcellsofthereticuloendothelialsystemintheadrenalglands,bone
marrow,gastrointestinaltract,liver,lymphnodeandspleen.Lesionstendtobecome
calcified.
Diagnosis
Specimens(CSF,biopsies,bonemarrow,lymphnodes,orbuffycoat)stainedwitha
varietyofhistologicalstains(GomorimethanamieorPeriodicacid-schiffstains)
revealtheorganismswithinmacrophages.
Skintest.
Immunodiffusiontest
Latexagglutinationtestandfluorescentantibodytest
Complementfixationisconsideredtheconfirmatorytest.

19. Treatment.
AmphotericinBisthedrugofchoice,butketoconazole,sulfonamides,andethyl
vallinatemayalsobeeffective.
UlcerativelymphangitisinHorse.
Ulcerativelymphangitisresemblethose of equinefarcy consistofulcerated
discharging nodules usually located alongthe courseof thickened, hard lymphatic
vessels.
Regional lymphadenopathyis often present.
Yeast cells ofH.farciminosumare found in large numbers inlesions mainlywithin
macrophages.
Organisms presentin discharges, can be spread by biting insects and through
contaminatedfomites.
Treatment : Surgical excision.
Test and slaughter.

20. Sporotrichosis

21. Sporotrichosis
Sporotrichosisis caused by the dimorphic fungusSporothrixschenckii.
The disease is characterized by nodular lesions that suppurate, ulcerate, drain,
and involve the cutaneous and subcutaneous tissues and the adjacentlymphatics.
The fungus is widespread in nature, found in soil, on wood, and on other
vegetation.
The organism gains entrance to the skin through wounds or by traumatic
implantation.
Occasionally (especially in dogs), the infection may spread to involve bone,
muscle, the central nervous system, lungs, or the genitourinary tract.
Infections are common, particularly in horses and dogs. In dogs, the disease is
more likely to disseminate and result in a fatal infection.

22. In horses, the disease must be differentiated from epizooticlymphangitis(caused
byHistoplasmafarciminosum).
Thelymphocutaneousform may benonsuppurative, or may result in ulcerations
and pus that discharge at several sites along the lymphatic channel, which serves
as a means of transmission for the organism within the animal.
Laboratoryrodents are highly susceptible to experimental infection, indicating the
virulence of this organism is greater than that of the opportunistic fungi.
The disease is infectious, but not contagious, and is chronic.
This dimorphic fungus can be isolated from lesions on brain heart infusion agar,
blood agar, orSabouraudagar withcycloheximideand chloramphenicol.
Themoldis white when young, then turns brown toblack.

23. Thehyphaeareseptateandfine,andthemicroconidiaforminclustersatthe
hyphaltipsorassessileformsatthesidesofthehyphae.
Differentiationfromsimilarlookingfungiisbyconversionofthemoldtothe
yeastphase.
Single-celled,cigar-shapedyeastsmayormaynotbeseeninpusfromlesions.
Fluorescentantibodyenhancesvisualizationandconfirmationofthedisease.
Serologicaldiagnosiscanbemadebydemonstrationofariseincomplement-
fixingantibody.
Potassiumiodide,AmphotericinB,ketoconazoleandmicoconazoleareeffective
fortreatment.