veterinary misc. bacteria and fungal agents
Terms
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copy deck
-
⬢ Acidfast rods, sometimes branching filaments but
easily fragmented, irregular staining (beaded). - Mycobacterium
-
• Cell walls are rich in lipids, waxes.
– Slow growth rate (2-20 hour generation time).
– Resistant to drying, some disinfectants.
– Retain viability in soil and dried feces for many months.
– Killed by sunlight, UV irradiat - Mycobacterium
-
⬢ Reservoir for pathogenic, tuberculous
mycobacteria is _________________. -
⬢ Reservoir for pathogenic, tuberculous
mycobacteria is infected animals (parasitic). -
⬢ Saprophytic (atypical) mycobacteria are
widespread in __________________. -
⬢ Saprophytic (atypical) mycobacteria are
widespread in soil and water (opportunistic). - ⬢ Tuberculosis:
-
• Tuberculosis: an infectious, granulomatous
disease causing tubercles.
– Typically a disease of captivity or domestication,
confining and crowding. - ⬢ Pathogenesis of tuberculosis.
-
• Pathogenesis of tuberculosis.
– Entry via respiratory and intestinal tracts.
– Local multiplication occurs, resistance to phagocytic
killing allows continued intracellular replication.
– Infected cells reach local lymph nodes and may
disseminate.
– Inflammatory and cell-mediated immune reactions
cause accumulation of macrophages (granuloma).
– Caseous necrosis occurs at the center of the lesion and
may proceed to calcification or liquefaction.
– Hematogenous dissemination may produce miliary
tuberculosis, involving multiple tubercle formation.
– Tubercles may enlarge, coalesce and eventually occupy
a sizable portion of the organs. - ⬢ Tubercle:
-
⬢ Tubercle: granuloma with a caseous, necrotic
center that may calcify, may become surrounded
by granulation tissue and a fibrous capsule.
when in capsule not contagious -
– Humans are primary host.
– Shed primarily in respiratory discharges.
– Transmitted by aerosols or fomites.
– Lesion found in the lungs and lymph nodes. - ⬢ Mycobacterium tuberculosis
-
Mycobacterium tuberculosis:
Progressive; Limited; Resistant animals -
Progressive:primates, dogs, elephants, Canaries, and
Psittacine birds
Limited:cattle and swine
Resistant:birds and cats -
– Cattle are the natural host.
– Wild animal reservoirs of agent include badgers in
Europe, brush-tailed opossums in New Zealand, Cape
buffalo in Africa, deer in Europe and North America.
– Excreted in respiratory discharges, fe - ⬢ Mycobacterium bovis
- ⬢ Mycobacterium bovis vaccination and treatment/control
-
– No viable vaccine for use in animals.
– Poorly responsive to treatment, test and eradication. - ⬢ Intradermal tuberculin skin test.
-
– Detect DTH response acquired through infection using
tuberculin or PPD (purified protein derivative). - ⬢ Mycobacterium bovis Progressive, Limited, and Resistant animals
-
Progressive:cattle, sheep, goats,Primates
Deer, elk, bison
Dogs, cats, swine
Llamas, badgers, opossum
Elephants, rhinoceri
Camels,and giraffes
limited:?
Resistant:birds - Current M. bovis concerns
-
• Michigan White-tailed deer
and other wildlife.
– California, Texas, and New
Mexico.
– 7 black bear, 4 bobcats, 18
coyotes, 2 opossums, 8
raccoons, and 3 red fox,
found to be infected with the
bovine TB organism. The
most likely source of infection
for these animals was
through the consumption of
tuberculous white-tailed deer.
• UK: Badger reservoir, spill-back into cattle.
• New Zealand: Brush-tailed opossums.
• Kruger National Park: infected buffalo with spillover
into predators and other wildlife. -
– Poultry are the primary hosts.
– Shed in feces.
– Acquired mainly by ingestion of contaminated food,
water and soil.
– Lesions may be found anywhere, but in birds usually
involve intestines, liver, spleen, and bone marr - ⬢ Mycobacterium avium
-
Mycobacterium avium
Progressive, Limited, and Resistant animals -
progressive:chickens and other birds
limited: cattle, sheep, goats,Primates
Dogs, cats, Swine, Deer, elk, and bison
Resistant:Psittacines - • Johne’s disease agent
-
Mycobacterium avium ssp.
paratuberculosis -
– Chronic, progressive enteritis characterized by
persistent and progressive diarrhea, weight loss,
debilitation, and eventually death.
– Disease of cattle, sheep, goats and other herbivores. -
Mycobacterium avium ssp.
paratuberculosis -
⬢ Large numbers of mycobacteria are present in
epithelioid and giant cells in the mucosa of ileum
and colon.
⬢ Mucosa becomes thickened and permanently
corrugated. -
Mycobacterium avium ssp.
paratuberculosis -
– Chronic, progressive enteritis characterized by
persistent and progressive diarrhea, weight loss,
debilitation, and eventually death.
• Organisms shed in feces, contaminate
environment, transmit primarily to young stock. -
Mycobacterium avium ssp.
paratuberculosis -
Family:______________
• Smallest and simplest procaryotes.
– Range in size from 0.2 to 0.5 μm.
– Lack genetic ability to form a cell wall, pleomorphic.
• Stain very poorly: lack cell wall and too small to observe. -
Family: Mycoplasmataceae
⬢ Mycoplasma, Ureaplasma, (Haemobartonella,
Eperythrozoon now included) -
• Occur as commensals on mucous membranes of
the upper respiratory and digestive tracts, genital
tract and bovine udder or cell-associated (RBC).
– Facultatively anaerobic to obligately anaerobic.
– Complex growth requirements f - Family: Mycoplasmataceae
-
• Infections can be endogenous or exogenous.
• Transmission by direct contact, aerosols, eggtransmitted.
• Cytoadherence to mucous membranes.
– Attachment organelle with network of adhesins. - Mycoplasma
-
• Intracellular localization.
– Potential to fuse with and enter host cells facilitates
latent or chronic infection.
• Cytotoxicity and inflammation.
– Biochemically mediated damage to adjacent host cells.
– Destroy cil - Mycoplasma
-
– Induce cytokine synthesis with pathologic
consequences.
• Infection may be primarily involving body surfaces.
– Respiratory tract, conjunctiva, genital tract, mammary
gland.
• Septicemia
• Serosal surfaces: joint - Mycoplasma
-
Mycoplasma disease
in Cattle -
– Pneumonia, mastitis, abortion.
– Also abortion, otitis media,
conjunctivitis, etc. -
Mycoplasma disease
in sheep and goats causes -
– Pneumonia, mastitis,
conjunctivitis. - Mycoplasma swine diseases
-
⬢ Swine diseases
⬢ Polyserositis, arthritis in young pigs.
⬢ Arthritis in young and feeder pigs.
⬢ Enzootic pneumonia. - Mycoplasma in dogs cause
- Pneumonia, UTI.
- Mycoplasma in rats
-
• Rats and mice, cats, horses, chickens, turkeys.
– Numerous species causing host specific infections. - – Feline infectious anemia, worldwide. agent
- Mycoplasma haemofelis
-
– Varies from mild anemia without clinical signs to severe
anemia progressing to depression and death.
– Transmission via cat fights, biting arthropods, fleas,
ingestion, transplacental infection reported.
– Deep purple, small c - Mycoplasma haemofelis
-
– Restricted to dogs.
Varies from mild anemia without clinical signs to severe
anemia progressing to depression and death. - Mycoplasma haemocanis
-
– Porcine eperythrozoonosis in US.
– Transmitted by biting arthropods and instruments.
– Usually subclinical but occasionally icteroanemia,
embryonic death and abortion.
– Small coccal or ring-forms on erythrocytes.
– O - ⬢ Mycoplasma (Eperythrozoon) suis
- ⬢ Antimicrobial susceptibility of Mycoplasma family.
-
– Tetracyclines, chloramphenicol.
– Quinolones, macrolides, lincosamides.
– Anaerobes not susceptible to aminoglycosides.
– Resistant to all cell-wall active agents. -
Order: Rickettsiales
⬢ Families: -
Rickettsiaceae and Anaplasmataceae
⬢ Minute, obligate intracellular parasites of
eucaryotic hosts (vertebrates, arthropods and
other invertebrates). -
– Transovarian and transstadial transmission.
– Transmission to mammals as a result of feeding by an
infected arthropod, etc.
• Rod-shaped, coccoid, pleomorphic.
• Poor survival outside of cells - direct transmission.
• - Order: Rickettsiales
-
• Organisms multiply by binary fission in the
cytoplasm (or nucleus) of target cells.
– Endothelium, phagocytic cells, or erythrocytes.
• Toxins: Phospholipase, hemolysins, endotoxin.
– Cell walls contain muramic acid (peptido - Order: Rickettsiales
-
Order: Rickettsiales
⬢ Diagnosis -
– Molecular detection
– Serology
– Isolation and identification - Order: Rickettsiales host range,
-
⬢ Vary from narrow to broad host range, including
some important zoonotic diseases. - Order: Rickettsiales treatment
-
⬢ Tetracyclines (doxycycline), chloramphenicol,
quinolones. -
– Rocky Mountain Spotted Fever, a disease of humans
and dogs, resulting in fever, edema, petechial and
ecchymotic hemorrhages, and neurological signs. agent:_______ - Rickettsia rickettsii
-
fever, edema, petechial and
ecchymotic hemorrhages, and neurological signs.
– Most cases occur in the Eastern US, carried by
Dermacentor andersoni and D. variablilis, seasonal. -
Rickettsia rickettsii
– Rocky Mountain Spotted Fever, -
– Ticks become infected by horizontal transmission while
feeding, transtadially and vertically by transovarian
passage.
– Replicates in tick midgut, maintained in nature in ticks.
– Ticks attach minimum of 5-20 hours to transmit -
Rickettsia rickettsii
– Rocky Mountain Spotted Fever, -
cattle and other ruminants.
– Fever, anemia, icterus (acute to chronic, incubation up
to 5 weeks).
– Tropical and sub-tropical regions, worldwide. - ⬢ Anaplasma marginale
- Family: Anaplasmataceae
- Anaplasma, Ehrlichia, Neorickettsia
-
⬢ Ticks, other arthropods, blood-sucking flying
insects, veterinary instruments.
⬢ Infect erythrocytes with a marginal distribution,
small pleomorphic forms (0.2-0.4 μm) in up to 50%
of cells.cattle and other ruminants - Anaplasma marginale,
- Ehrlichia: type of infections
- – Monocytic or granulocytic infections.
-
worldwide.
– Reservoir: Canids.
– Brown dog tick (Rhipicephalus sanguineus) is vector.
• Transstadial but not transovarian transmission. -
Ehrlichia canis
– Canine monocytic ehrlichiosis -
dogs.
Replicates in lymphocytes, monocytes and, rarely, in
neutrophils; vasculitis, thrombocytopenia, leukopenia
and anemia.
– Purple-staining cells or inclusions (morulae) in
monocytes or lymphocytes.
– No vaccine, tick - Ehrlichia canis
-
• Heartwater in domestic and wild ruminants in
Africa and Caribbean.
– Widespread edema, effusions, hemorrhage, pericardial
effusion is inconsistent. - Ehrlichia (Cowdria) ruminantium
-
– Infects reticular cells, neutrophils, and vascular
endothelial cells, short bacillary forms in cytoplasm.
cattle
• Amblyomma ticks serve as vector. - Ehrlichia (Cowdria) ruminantium
-
Ehrlichia (Cowdria) ruminantium
⬢ Heartwater in domestic and wild ruminants
⬢ A single isolate from lung, liver, and other tissues
of an aborted bovine fetus isolated in Washington,
1986. Now classified as __________________,
-
Ehrlichia (Cowdria) ruminantium
⬢ Heartwater in domestic and wild ruminants
⬢ A single isolate from lung, liver, and other tissues
of an aborted bovine fetus isolated in Washington,
1986. Now classified as Waddlia chondrophila,
and considered to belong to Chlamydiales. -
Salmon poisoning in dogs,
coyotes, foxes, bears and
ferrets in Pacific northwest
of US. - Neorickettsia helminthoeca
-
– Elokomin fluke fever agent is
a milder variant.
• Ingestion of salmon
containing the agent within
the metacercariae of
Nanophyetus salmincola.
– Mature fluke inoculates
agent, 5-7 day incubation. - Neorickettsia helminthoeca
-
• Parasitizes reticuloendothelial cells of the
lymphoid system, including macrophages.
– Fever, swollen lymph nodes, hemorrhagic enteritis
– Morulae and individual coccal cells in cytoplasm of
macrophages.
• Freeze fish ( - Neorickettsia helminthoeca
-
• Potomac horse fever in USA (1979) and Europe.
• Equine monocytic ehrlichiosis.
– Fever, leukopenia, usually diarrhea, may progress to
laminitis.
• Present in monocytes, intestinal involvement.
– Morulae in monocytes.< - Neorickettsia (Ehrlichia) risticii
-
⬢ Seasonal oral ingestion; agent in fresh-water
snails or insects infested with developmental
stages (cercaria or metacercaria) of trematodes. - Neorickettsia (Ehrlichia) risticii
- Reservoir of N. risticii
-
• Insectivorous bats and birds.
– Northern California bats and swallows serve as host for
adult trematodes (Acanthatrium or Lecithodendrium
sp.).
– N. risticii DNA identified by PCR in:
• All stages of life cycle of trematodes (snails, aquatic insects).
• Adult flukes and gastrointestinal tract of insectivores.
• Spleen of bats, liver of swallow.
• Bats and swallows may serve as natural reservoir. -
⬢ Seasonal oral ingestion; agent in fresh-water
snails or insects infested with developmental
stages (cercaria or metacercaria) of trematodes.
⬢ Accidental ingestion of snails or insects, feed or
water contaminated with secretions - Neorickettsia (Ehrlichia) risticii
-
⬢ Q fever in humans: cattle, goats and sheep are
most important reservoirs.
⬢ Worldwide: reported in 125 mammals, birds, fish and 40 ticks.
⬢ Cats and dogs may be reservoirs. - Coxiella burnetii
-
⬢ Asymptomatic infection, acute influenza-like
illness, chronic endocarditis or hepatitis.
⬢ Occasional abortions, weak offspring or infertility in ruminants
(placentitis and abortion reported in cats).
⬢ Found in milk, urine, f - Coxiella burnetii
-
⬢ Replication in alveolar macrophages; endothelium,
respiratory, renal and serosal epithelium;
fibroblasts.
⬢ Short rods within cells. - Coxiella burnetii
-
Coxiella burnetii
Biphasic developmental cycle -
• Small cell variants (SCV) – 0.2 to 0.5 um.
• Large cell variants (LCV) – > 1.0 um.
• Differences in ultrastructure, antigenicity,
metabolic capability, physical resistance and
protein composition. -
⬢ Infective aerosol dose: 1-10 organisms.
⬢ Incubation period: 10-40 days.
⬢ Clinical features:
⬢ Case-fatality rate is low, even without treatment.
⬢ Abrupt or insidious onset: fever, chills, headache,
⬢ Malaise and - Coxiella burnetii
-
Coxiella burnetii
⬢ Viability and disinfection: -
⬢ Increased resistance to heat, dessication, osmotic shock, UV
light, and chemicals (hypochlorite 0.5%, phenolics, lysol, etc.)
⬢ 2% bleach, 30 minute contact with 70% alcohol, quaternary
ammonium disinfectants. -
⬢ Obligately parasitic, coccoid bacteria, multiply
within membrane-bound vacuoles in the cytoplasm
of cells of mammalian and avian origin.
⬢ Modified cell wall - glycolipids and protein, familyspecific
LPS.
⬢ Elementary bod - Chlamydia and Chlamydophila
-
⬢ Relatively resistant, viable for several days.
⬢ Attaches to cell, enters by endocytosis, survives in phagosome.
⬢ Differentiates into RB.
⬢ Reticulate body is the metabolically active,
noninfectious, intracellular form (500 - Chlamydia and Chlamydophila
-
• Persist as subclinical
infections of the respiratory,
gastrointestinal, and genital
tract of birds and mammals.
– Carriers provide prolonged
fecal shedding.
– Transmission by inhalation or
ingestion. - Chlamydia and Chlamydophila
-
• Infect a broad range of avian and mammalian hosts.
– Disease associations, tissue tropisms, hosts by species.
– Pneumonia, abortion, rhinitis, conjunctivitis, arthritis,
enteritis, no apparent disease (carrier = asymptomatic
i - Chlamydia and Chlamydophila
- Avian chlamydiosis:
-
Chlamydophila (Chlamydia) psittaci
⬢ Avian chlamydiosis: An acute or chronic infection
of wild and domestic birds causing respiratory,
intestinal, systemic signs, or asymptomic. -
An acute or chronic infection
of wild and domestic birds causing respiratory,
intestinal, systemic signs, or asymptomic.
⬢ Entry: pharynx, eye, genital. Bacteremia, infects
brain, eye, genital, intestine, liver, lung, spleen and
- Chlamydophila (Chlamydia) psittaci
-
• 8 serovars, all transmissible to humans.
– Psittacosis: Sporadic disease in humans, other
mammals, and tortoises.
– Ornithosis (pigeons and turkeys).
– Occupational hazards in bird slaughterhouses, other
birds, mammals, - Chlamydophila (Chlamydia) psittaci
-
• Abortion - Sheep, goats, cattle.
– Enzootic abortion of ewes (EAE), worldwide. - Chlamydophila abortus
-
• Oral, nasal, genital entry, bacteremic spread.
– Placental colonization, fetal tissues, intestine.
• Women who work with sheep have suffered
sporadic, documented cases of zoonotic abortion.
• Rare cases of abortion in a hors - Chlamydophila abortus
-
• Endemic among cats worldwide
• Conjunctivitis, rhinitis, and respiratory problems.
– Also infects genital tissues and joints.
• Asymptomatic persistence not documented.
• Zoonotic infections of humans reported.
• At - Chlamydophila felis
-
• Predilection for epithelial cells of mucous
membranes.
• Latent, inactive infections cause persistent
antigenic stimulation leading to chronic
inflammation.
• Diagnosis
– Molecular detection
– Serology
- Chlamydiosis
- Chlamydiosis Antimicrobial susceptibility:
-
Antimicrobial susceptibility: Tetracyclines
(doxycycline) and chloramphenicol. -
Fungi
• Nonphotosynthetic.
– Live on ______________ in soil, water, on
plants and animals (usually dead and decaying matter).
– May have unique geographic distribution.
• Typical eukaryotic cell structure.
– Rigid -
Fungi
• Nonphotosynthetic.
– Live on complex organic nutrients in soil, water, on
plants and animals (usually dead and decaying matter).
– May have unique geographic distribution.
• Typical eukaryotic cell structure.
– Rigid cell wall of polysaccharide polymers.
• Usually chitin or cellulose.
• Ergosterol in cell membrane: target of antifungals.
• Unique cell structure, function and differentiation
resulting in sexual and asexual reproduction.
– Morphological features are important identification keys. -
Fungi
⬢ Three major morphological groups. -
– Yeasts: ovoid, budding cells.
• Typically single-celled, thick cell wall, lacking mycelia, asexual.
– Molds: mass of branching, randomly interlaced
filamentous tubes (hyphae) filled with cytoplasm,
forming a woolly, fuzzy growth (mycelium).
• Hyphae may be septate or aseptate.
– Mushrooms: true fungi that consist of an organized
network of hyphae resulting in regular shaped mycelia. -
Fungi ⬢ Asexual reproduction:
⬢ Sexual reproduction: -
⬢ Asexual reproduction: budding, hyphal extension,
asexual spores (conidia), usual clinical form.
⬢ Sexual reproduction: fusion of gametes,
subsequent division into spores (conidia). -
Fungi
⬢ Dimorphism: -
a transient adaptation.
– Can grow as either molds or yeast depending on growth
conditions (temperature, nutrients, etc.).
– Drastic changes in metabolism, morphology, antigenic
structure, methods of reproduction - ⬢ Special staining/visualization methods for fungi.
-
– Lactophenol cotton blue stain
– Silver stain
– PAS (Periodic acid-Schiff) stain
– Negative staining
– Potassium hydroxide digest - ⬢ Classes or subdivisions of fungi.
-
– Zygomycetes (Phycomycetes): Aseptate fungi.
– Ascomycetes: Sexual reproductive form.
– Deuteromycetes (Fungi imperfecti): Asexual
reproductive form.
– Basidiomycetes: mushrooms. - Fungi Pragmatic clinical classification.
-
– Yeasts: those agents primarily observed in this form.
– Dermatophytes: parasitize keratinized structures.
– Dimorphic, systemic fungi.
– Miscellaneous, opportunistic fungi. -
⬢ Oval, thin-walled, small budding yeast cells.
⬢ Normal inhabitant of alimentary tract and lower
reproductive tract of most mammals and birds.
⬢ Infections are usually endogenous on mucous
membranes, depend on compromised defen - Candida albicans
-
– Young are especially susceptible.
– Prolonged antibacterial use may predispose.
– Immunocompromised are most susceptible, may
progress to disseminated form.
• Ulceration and fibrinous plaques on membranes.
– Thrush: o - Candida albicans
-
Candida albicans
⬢ Virulence factors: -
– Adhesins, secreted proteases and phospholipases, and
morphogenesis (reversible transition between yeast,
pseudohyphae and hyphae). -
• Diagnostic characteristics:
– Small budding yeast, with occasional pseudohyphae. - Candida albicans
-
• Diagnostic characteristics:
– Readily isolated on routine bacteriological agars.
– Germ tube formation when incubated 2-4 hr. in serum.
• Filamentous extension from the yeast cell. - Candida albicans
-
⬢ Saprophytic, round, yeast (3.5-7 μm) with ability to
form a large polysaccharide capsule (up to 30 μm).
⬢ Worldwide distribution in soil, highest numbers in
pigeon droppings, inside shaded, damp buildings.
⬢ Acquired by inha - Cryptococcus neoformans
-
– Deposits in upper respiratory tract or lodges in alveoli.
• Nasal granuloma, can extend locally to the CNS.
• Pulmonary granuloma, can disseminate hematogenously, often
to CNS.
• Antiphagocytic, immunosuppressive capsule eli - Cryptococcus neoformans
- Round yeast cell; single, pinched-off buds; capsule.
- Cryptococcus neoformans
-
most common systemic
mycosis of cats. - Cryptococcus neoformans
-
cats – Nasal cavity (80%), pneumonic, meningitis, peripheral
neuritis of optic nerve, granulomatous chorioretinitis. - Cryptococcus neoformans
-
– Easily cultivated on agar plates.
– Antigen detection in serum, CSF or urine.
• Most mammals susceptible: dogs, horses, humans
• Agent may pass through digestive tract of birds
but rarely infects (inhibited above 39C). - Cryptococcus neoformans
-
⬢ Aka Pityrosporum
⬢ Saprophytic, lipophilic, monopolar yeasts that
colonize the skin and mucocutaneous regions.
⬢ Frequent colonizer of external ear canal of dogs. - Malassezia pachydermatis
-
yeast
⬢ Superficial perivascular to interstitial dermatitis
with hyperkerratosis, irregular hyperplasia of the
epidermis and follicular infundibula, epidermal
spongiosis, and lymphocyte exocytosis. - Malassezia pachydermatis
-
• Change in host immunity, altered skin
microclimate, or disruption in epithelial barrier may
predispose to clinical disease.
– Seborrheic reaction in skin allows the yeast to
proliferate. - Malassezia pachydermatis
-
• Direct exam: bottle-shaped, small budding cells.
– Bud fission, bud detaches by forming a septum. - Malassezia pachydermatis
- ⬢ Keratinophilic species of fungi
- Dermatophytes
-
– Able to penetrate all layers of the skin, but generally
restricted to the cornified nonliving keratin layer and
appendages: hair, nails (claws), horn, fur, rarely
feathers. - Dermatophytes
- ringworm.
- dermatophytosis
-
• Worldwide distribution as soil saprophytes that
have become highly host-adapted parasites.
– Geophilic still primarily inhabit soil.
– Zoophilic parasitize animals.
– Anthropophilic parasitize humans. - Dermatophytes
-
Dermatophytes
⬢ Morphology -
– Nonparasitic state, including culture, produce septate,
branching hyphae (mycelium) with asexual reproductive
units (either macroconidia or microconidia).
– Parasitic state produces only hyphae and arthroconidia. - Dermatophytes transmission and incubation period
-
• Transmitted from animals to animals, animals to
humans, humans to humans, humans to animals,
soil to either animals or humans by direct or
indirect contact.
– Conidia survive in hair, on scales and fomites for
months to years.
• Incubation period is usually 1 to 3 weeks. - ⬢ Endothrix =
- ⬢ Endothrix = arthroconidia accumulation within hair (humans).
-
Dermatophytes
• Pathogenesis
– A _________ enters a defect in the stratum corneum.
– Germination requires _________ and ________ stimuli.
– Develops into __________ branching among cornified
epithelium.
– Portions -
Dermatophytes
• Pathogenesis
– A conidium enters a defect in the stratum corneum.
– Germination requires moisture and chemical stimuli.
– Develops into mycelium branching among cornified
epithelium.
– Portions of mycelium differentiate into arthroconidia.
– Hair invasion begins with germination of a conidium
near a follicular orifice.
• Extend along outer root sheaths and invade growing hairs near
the living root cells.
• Grow in outer parts with accumulation of arthroconidia on the
surface of the hair = ectothrix, characteristic of all significant
animal dermatophytes.
• Endothrix = arthroconidia accumulation within hair (humans).
– Hypertrophy of the stratum corneum with accelerated
keratinization and exfoliation, producing a scurfy
appearance.
– Infected hair become brittle and weak, breaks-off.
– Inflammation in area of infection ranges from erythema
to vesiculopustular reactions and suppuration.
• Antifungal activity of serum and body fluids terminates infection.
– Infection may spread beyond area of inflammation,
resulting in “ring†of advancing lesion with resolution in
the center = “ringwormâ€. -
Dermatophytes
• _________ animals are predisposed to infection.
– Lack _____________, skin habitat may differ. -
Dermatophytes
• Young animals are predisposed to infection.
– Lack acquired immunity, skin habitat may differ. -
Dermatophytes
⬢ Laboratory diagnosis -
– Specimen collection from periphery of lesion, pluck hair.
• Use toothbrush to sample asymptomatic animals.
– Wood’s lamp: M. canis may show fluorescence in hair.
– Direct microscopic examination following KOH digestion
for hyphae and arthroconidia.
– Culture using Dermatophyte Test Medium (DTM).
• Dermatophytes usually appear in 7-10 days, changing pH
indicator in agar to red, produce light colored cottony mycelium. - Genera of dermatophytes of veterinary importance
-
– Microsporum spp.
– Trichophyton spp. -
⬢ Macroconidia are few or absent. If present they are elongated
and cigar or pencil-shaped, thin and smooth walls, divided into
many cells by transverse septa.
⬢ Microconidia usually numerous and borne singly along the
hyphae or i - Trichophyton spp
-
Macroconidia are large, thick-walled and divided into many cells
by transverse septa. Tend to be spindle or boat-shaped with
roughened surface.
⬢ Microconidia are relatively few or absent. If present, they are
tear-shaped and borne - Microsporum spp
-
Ringworm
– 90-98% of cases in cats; irregular patchy alopecia.
– 70% of cases in dogs; classic foci of alopecia with
follicular papules, scales, and crusts.
– Vaccine for treatment and prevention of lesion
development but n - ⬢ Microsporum canis
-
ringworm
⬢ Geophilic, 20% of cases in dogs. - Microsporum gypseum
-
Dermatophyte
Cattle and sheep; discrete, scaling patches of hair loss
with crust formation, some become thickly crusted with
suppuration, winter problem. - Trichophyton verrucosum
-
Dermatophyte
– Horses; patches of alopecia,
erythema, scaling, and
crusting; “girth itchâ€. - ⬢ Trichophyton equinum
- Dermatophytes in horses
-
• Trichophyton equinum
– Horses; patches of alopecia,
erythema, scaling, and
crusting; “girth itchâ€.
• Trichophyton
mentagrophytes
• Microsporum equinum
• Microsporum gypseum -
Dermatophytes
Environmental control -
– Thorough vacuuming and cleaning: no visible hair.
– Washing and disinfection: 1:10 household bleach
solution.
– Discard items that can’t be disinfected. -
Systemic mycoses (_______________)
⬢ Most are free-living in nature as ___________, may
have unique geographic or ecologic preferences.
⬢ Entry: primarily by _________.
⬢ Growth in tissues is primarily __________ phase;
non -
Systemic mycoses (Dimorphic fungi)
⬢ Most are free-living in nature as saprophytes, may
have unique geographic or ecologic preferences.
⬢ Entry: primarily by inhalation.
⬢ Growth in tissues is primarily yeast phase;
nonparasitic growth as mycelium.
⬢ Lesions tend to be pyogranulomatous; inadequate
CMI allows dissemination to bone, skin, CNS, or
abdominal viscera.
⬢ Shedding occurs, but very limited contagious risk.
⬢ Diagnosis based on unique morphologic
characteristics of parasitic form. -
• Coccidioidomycosis, Desert fever, San Joaquin
Valley fever.
• Endemic in the Lower Sonoran Life zones.
– Southwestern US, Mexico, Central and South America.
– Sandy, alkaline soils, high environmental temperatures.
– - Coccidioides immitis and C. posadasii
-
• Grows as mycelium in soil, arthroconidia survive.
– After rainfall, it grows near surface.
– Soil disturbances and wind disseminate spores.
• Most cases occur as a result of residence or travel
in endemic area. - Coccidioides immitis and C. posadasii
-
• Arthroconidia (<10) inhaled, grow as yeast.
• Spherule undergoes repeated internal divisions to
become filled with endospores.
– Large (10-80 μm), round, double-walled structure.
• Each endospore has the potential to bec - Coccidioides immitis and C. posadasii
-
Coccidioides immitis and C. posadisii
⬢ Most infections are _______________________________________________: cattle, humans, dogs, cats
⬢ Inadequate ____ allows dissemination of
endospores: _______,_______,_______.
⬢ Others susc -
Coccidioides immitis and C. posadisii
⬢ Most infections are inapparent and limited to lung
and hilar lymph nodes: cattle, humans, dogs, cats
⬢ Inadequate CMI allows dissemination of
endospores: dogs, humans, cats.
⬢ Others susceptible: horses, llamas, ferrets, etc. -
Coccidioides immitis and C. posadisii
⬢ Dissemination targets: -
bones, eyes, heart and
pericardium, testes, brain, spinal cord, visceral
organs. -
Coccidioides immitis and C. posadisii
⬢ Diagnostic characteristics: -
Yeast: large spherule containing endospores
– Large spherule containing endospores is conclusive.
– Serologic testing is diagnostic and prognostic.
– Do NOT attempt to cultivate.
• Produces highly infectious arthroconidia.
• Drainage contaminating bandages may provide suitable
environment for arthroconidia development.
• Arthroconidia in hyphae - ⬢ North American blastomycosis
- Blastomyces dermatitidis
-
• Endemic in Mississippi, Missouri, and Ohio River
valleys, mid-Atlantic states, and the Canadian
provinces of Quebec, Manitoba, and Ontario.
– Sporadic cases observed in other areas.
• Saprophytic mycelium, probably in soil.
- Blastomyces dermatitidis
-
• Susceptible animals.
– Dog (10x humans), cat, horse, ferret, deer, bottlenosed
dolphin, sea lion.
• Acquired by inhalation of spores.
– Enter terminal airway, grow as yeast.
• After established in lungs, may dissemina - Blastomyces dermatitidis
-
Blastomycosis
• After established in ______, may disseminate.
–______________________________. -
Blastomycosis
• After established in lungs, may disseminate.
– Skin, eyes, bones, lymph nodes, subcutaneous tissues. -
– Thick-walled, broad-based budding yeasts (5-20 μm).
– Usually a single bud. - Blastomyces dermatitidis
-
Blastomyces dermatitidis
⬢ Laboratory diagnosis: -
– Thick-walled, broad-based budding yeasts (5-20 μm).
– Serologic testing.
– Culture or PCR on tissue.
– Antigen detection in urine. -
⬢ Diagnostic test sensitivity for blastomycosis in canines.
Cytology _______ Budding yeast
Culture ____ [66-91%]
Serology (Antibody) ___ Diagnosed 6%
Cross-reacts
Antigen detection ____ in humans Cross-reacts -
Cytology 71-94% Budding yeast
Culture 12%? [66-91%]
Serology (Antibody) 40-95% Diagnosed 6%
Cross-reacts
Antigen detection 93% in humans Cross-reacts -
Blastomyces dermatitidis
• Avoid getting _________ when handling a dog with
blastomycosis.
– Accidental percutaneous inoculation results in _______________. -
Blastomyces dermatitidis
• Avoid getting bitten when handling a dog with
blastomycosis.
– Accidental percutaneous inoculation results in localized
lesion without dissemination. -
⬢ Free-living mycelial stage in soil containing
nitrogen-rich organic matter such as bird and bat
excrement under moist, humid conditions. - Histoplasma capsulatum
- ⬢ Histoplasmosis:
-
a chronic, noncontagious,
disseminated, granulomatous disease. - Histoplasma capsulatum region
- ⬢ Mississippi, Ohio, and Missouri River valleys
-
Histoplasma capsulatum
• Endemic in central US:__________________________.
– ___________ and ________ regions of the world.
– Isolated from soil in __ states. -
Histoplasma capsulatum
• Endemic in central US: Ohio, Mississippi, and
Missouri River valleys.
– Temperate and subtropical regions of the world.
– Isolated from soil in 31 states. -
• Produces macroconidia and microconidia in soil.
– Microconidia inhaled into airways.
– Ingestion leading to primary GI disease???
• Microconidia converts to yeast in lung, reproduces
by budding.
• Phagocytized by cell - Histoplasma capsulatum
-
Histoplasmosis
⬢diseases -
Histoplasmosis
• Acute pulmonary disease.
– Severity correlates with exposure level.
• Granulomatous mediastinitis.
– Enlarged lymph nodes, cough and respiratory distress.
• Progressive disseminated histoplasmosis.
– Generalized disease of reticuloendothelial system (liver,
spleen, lymph nodes), bone marrow, eyes, intestine.
• Equine abortion.
– Placental and fetal infection only. -
• Numerous organisms in tissue, contained within
mononuclear phagocytes.
– Single or multiple, small (2-4 μm) round yeast with a
light halo (staining artifact - not a capsule). - Histoplasma capsulatum
-
Histoplasmosis
⬢ Laboratory diagnosis: -
– Numerous organisms in tissue, contained within mononuclear
phagocytes.
• Single or multiple, small (2-4 μm) round yeast with a light halo (staining
artifact - not a capsule).
– Serologic testing.
– Culture on tissue.
– Antigen detection in urine. -
⬢ Diagnostic test sensitivity for disseminated histoplasmosis.
Cytology ______ Intracellular yeast
Culture _______
Serology (Antibody) ________ Cross-reacts
Antigen detection _______ Cross-reacts -
Cytology 40-57% Intracellular yeast
Culture 82-90%
Serology (Antibody) 67-85% Cross-reacts
Antigen detection 80-95% Cross-reacts -
• Infection has been described in many animals, but
is uncommon in all but dogs and cats.
– Most infections are subclinical in dogs, but those with
clinical signs usually have disseminated disease.
– Most infected cats have diss - Histoplasma capsulatum
- ⬢ Sporotrichosis:
-
an uncommon, sporadic,
chronic granulomatous disease affecting
mostly skin, subcutis, and lymphatics
caused by a dimorphic fungus -
• Worldwide distribution, primarily in soils
that are rich in decaying organic matter.
– Also isolated from dead plant materials: rose
bush thorns, sphagnum moss, tree bark, hay
bales.
• Traumatic implantation through skin< - Sporothrix schenckii
-
⬢ Sporotrichosis: an uncommon, sporadic,
chronic granulomatous disease affecting
mostly skin, subcutis, and lymphatics
caused by a dimorphic fungus. - Sporothrix schenckii
-
• Infection occurs in humans, horses, dogs and cats
– Also reported in many other species of animals.
• Dissemination is rare in all except
immunocompromised and cats.
– Copious numbers of organisms in tissues of cats. - Sporothrix schenckii
-
• In tissue, pleomorphic yeast is round, oval or
cigar-shaped and may be found intracellular or
extracellular.
– Very difficult to identify in all but feline tissues. - Sporothrix schenckii
-
Sporothrix schenckii zoonotic risk
. -
Sporothrix schenckii
⬢ Minimal zoonotic risk
except feline to human
transmission: use strict
hygiene, warn handlers. -
Subcutaneous mycoses
• In addition to Sporothrix schenckii, 100’s of
species of ___________________ cause
opportunistic infection following ____________________.
– Most have very limited invasive, spread potential.
– May -
Subcutaneous mycoses
• In addition to Sporothrix schenckii, 100’s of
species of non-dimorphic molds cause
opportunistic infection following traumatic
implantation.
– Most have very limited invasive, spread potential.
– May spread to regional lymph node.
• Produce chronic, disfiguring granulomas.
• Diagnosis: biopsy to demonstrate broad, ribbonlike
hyphae invading tissue.
• Surgical excision is frequently the most effective
treatment. -
⬢ Class of fungi that form
aseptate hyphae and produce
spores in a sac-like structure
known as a sporangium.
⬢ Most are soil organisms that
gain entrance by inhalation or
ingestion (moldy hay). - Zygomycetes
-
• Invade arterial vessels leading to thrombosis and
infarction, thromboembolic dissemination.
– Granulomatous inflammation in chronic cases.
– Abortion in ruminants due to placentitis and vasculitis.
• Two of the more common g - Zygomycetes
-
⬢ Ubiquitous saprophytic molds, opportunistic
pathogens depending on impaired,
overwhelmed, or bypassed host defenses.
⬢ Septate hyphae, conidia radiating from
conidiophore. - Aspergillus sp.
-
• Septate hyphae, conidia radiating
from conidiophore.
– Mycelium in tissues.
– Conidiophore observed only in
aerated body cavities. - Aspergillus sp
-
Aspergillus sp.
⬢ Several manifestations of
aspergillosis. -
Aspergillus sp.
• Several manifestations of
aspergillosis.
– Diffuse infection of airways, air sacs
of birds.
– Sinus infections and disseminated disease in dogs.
– Guttural pouch infection in horses. -
• A unicellular eukaryotic organism.
– Originally grouped with the protozoa.
– Number of features in common with fungi.
• No ergosterol.
• Natural reservoir unknown: considered to be
widespread in the environment. Airbo - Pneumocystis sp.
-
Pneumocystis sp.
• A unicellular eukaryotic organism.
– Originally grouped with the ________.
– Number of features in common with fungi.
• No ___________.
• Natural reservoir unknown: considered to be
widespread in -
Pneumocystis sp.
• A unicellular eukaryotic organism.
– Originally grouped with the protozoa.
– Number of features in common with fungi.
• No ergosterol.
• Natural reservoir unknown: considered to be
widespread in the environment. Airborne.
– Highly infectious, low virulence.
• Pathogenicity demonstrated for multiple species,
primarily immunodeficient animals.
• Pneumonia: interstitial infiltrates. Extrapulmonary
infection reported in a few HIV patients.
• Asymptomatic infection in immunocompetent
humans and mammals. - Pneumocystis sp.
-
Pneumocystis sp.
• Pneumocystis carinii
– P. wakefieldiae – proposed second species in animals.
– P. jirovecii – exclusive agent in humans. - Pneumocystis sp Diagnosis
-
Diagnosis primarily by direct detection/observation
of agent in tissues.
• Life cycle: forms observed in tissue.
– Trophic form: pleomorphic, 1-5 μm dia., primary
proliverative stage, asexual binary fission.
– Precyst form: 5-8 μm dia., intermediate form and
incompletely differentiated cyst.
– Cyst form: 5-10 μm dia., thick walled, contains 8
sporozoites, collapses after release of spores. -
Pneumocystis sp.
Infective stage.
⬢ Drug of choice -
⬢ Infective stage unknown.
⬢ Drug of choice: trimethoprim/sulfamethoxazole. -
Mycotoxins
⬢ Toxic metabolites of certain fungi that grow on ________.
⬢ Small, ____________, ___________, hydrocarbons.
⬢ Production influenced by substrate (____________),
temperature, moisture, aeration, pH, storage, etc.
-
Mycotoxins
• Toxic metabolites of certain fungi that grow on
animal feeds.
• Small, nonantigenic, aromatic, hydrocarbons.
• Production influenced by substrate (plant stress),
temperature, moisture, aeration, pH, storage, etc.
– Not all strains of a fungal species produce toxin.
– Toxin may be present without cultivatable fungi. -
Mycotoxins
⬢ ______, or ________ disease: effects may be
cumulative as well as toxin deposition in tissues.
⬢ Lesions of mycotoxicosis depend on the ___________; one or more of the following:
1.
2.
3.
4.
5. -
Mycotoxins
• Acute, or chronic disease: effects may be
cumulative as well as toxin deposition in tissues.
• Lesions of mycotoxicosis depend on the specific
toxin; one or more of the following:
– Necrosis and hemorrhage.
– Bone marrow suppression.
– Estrogenic.
– Immune suppression.
– Carcinogenic. - Mycotoxin decontamination and detoxification
-
Mycotoxin decontamination and detoxification
• Physical cleaning of feedstuff.
• Sort and separate moldy feed ingredients.
– Feed to non-susceptible species.
– Blend with other feed to dilute.
• Chemical detoxification: ammoniation, ozonization.
• Binding agents: add clay, zeolite, granualted
activated carbon to feed.
• Microbiological degradation. -
common for queens to transmit to kittens
may cause more serious diseaes in FeLV cats
adhere to surface of RBC - Mycoplasma haemofelis
-
Antifungals
• Target biochemical differences between ______
and ______ cells.
– Cell membrane active antifungals target __________.
• Polyenes (amphotericin B and nystatin) ____________.
• Imidazoles _____________________ -
Antifungals
• Target biochemical differences between fungal
and animal cells.
– Cell membrane active antifungals target ergosterol.
• Polyenes (amphotericin B and nystatin) bind to it.
• Imidazoles inhibit synthesis.
• Allylamines and thiocarbamates inhibit synthesis (Terbinafine –
Lamisil and naftifine).
– Inhibit fungal mitosis (griseofulvin).
– Inhibit RNA and protein synthesis (5-flucytosine).
– Inhibit cell wall (chitin or glucan) synthesis (lufenuron,
echinocandins, pneumocandins, cilofungin).
• Antifungal susceptibility testing available in
reference laboratories. -
– Fungicidal by binding to ergosterol, causing cell leakage
and cell death.
– Effective against most systemic mycoses agents and
yeasts, variable against opportunitistic fungi.
– Resistance develops slowly and does not reach hig - ⬢ Amphotericin B
-
– Fungistatic by inhibiting ergosterol synthesis.
– Broad antifungal spectrum of activity: systemic
mycoses, yeast, dermatophytes; variable activity
against opportunistic fungi, bacteria, protozoa,
helminths, etc.
– Very li -
• Imidazoles
– Miconazole, clotrimazole, ketoconazole, itraconazole,
fluconazole, etc. -
– Fungicidal: Deaminated by fungi to 5-fluorouracil,
inhibits RNA and protein synthesis.
– Active only against yeast: Candida, Cryptococcus, etc.
– Resistance emerges rapidly during treatment. - ⬢ Flucytosine
-
– Fungistatic: inhibits mitosis, but action is slow.
– Effective only as a systemic agent against
dermatophytes.
– Resistance is rare. - ⬢ Griseofulvin
- – Effective for lymphocutaneous sporotrichosis.
- ⬢ Potassium iodide
-
Antifungal recommendations for deep/systemic
infections.
Candida -
first choice:Amphotericin B, Fluconazole
second choice:Itraconazole -
Antifungal recommendations for deep/systemic
infections
Cryptococcus -
first choice:Amphotericin B, Fluconazole
second choice:5-flucytosine -
Antifungal recommendations for deep/systemic
infections
Coccidioides -
first choice:Amphotericin B, Fluconazole
second choice:Keto, Itra -
Antifungal recommendations for deep/systemic
infections
Blastomyces -
first choice:Amphotericin B, Itraconazole
second choice:Keto, flu -
Antifungal recommendations for deep/systemic
infections.
Blastomyces -
first choice:Amphotericin B, Itraconazole
second choice:Keto, Flu -
Antifungal recommendations for deep/systemic
infections.
Histoplasma -
first choice:Amphotericin B, Itraconazole
second choice:Keto, Flu -
Antifungal recommendations for deep/systemic
infections
Sporothrix -
first choice:Amphotericin B, Itraconazole
second choice:KI -
Antifungal recommendations for deep/systemic
infections
Aspergillus -
first choice:Amphotericin B, Itraconazole
second choice:Enilconazole -
Antifungal recommendations for deep/systemic
infections
Dermatophytes -
first choice:Griseofulvin
second choice:Itra, Keto -
Prototheca sp.
• _____________ algae
– Found in soil and aqueous habitats worldwide, plant and
animal sources.
• Sporadic cases of bovine _________. Cull.
• Cats: _____________ ___________ and
______________________. -
Prototheca sp.
• Achlorophyllic algae
– Found in soil and aqueous habitats worldwide, plant and
animal sources.
• Sporadic cases of bovine mastitis. Cull.
• Cats: localized infection of the dermis and
subcutis, regional lymphadenopathy.
• Dogs: systemic disease that begins in the GIT and
frequently involves CNS and eyes. Uniformly fatal. -
Prototheca sp.
⬢ Diagnosis and identification. -
– Round to oval sporangia (7-25 μm dia.), containing 2-20
sporangiospores (internal septation).
– Readily cultivatable on blood agar plates (48 hr.). -
Pythium insidiosum
• Aquatic organism – class _____________.
– Often misclassified as “___________.â€
– Also described as “________†and swamp _________.
• Differs from true fungi by:
– ____________________.
-
Pythium insidiosum
• Aquatic organism – class Oomycetes.
– Often misclassified as “aquatic fungus.â€
– Also described as “leeches†and swamp cancer.
• Differs from true fungi by:
– Producing motile, biflagellate zoospores.
– Cell walls lack chitin.
– Plasma membrane lacks ergosterol. -
⬢ Complex life cycle produces a motile zoospore as
the infective stage. Granulomatous lesion.
⬢ Encountered in Gulf Coast states and as far north
as KY, MO, IL, IN, VA, and NJ. - Pythium insidiosum
-
Pythiosis
⬢ _______ and _______ most commonly affected. -
Pythiosis
⬢ Dogs and horses most commonly affected. - – Equine pythiosis:
-
– Equine pythiosis: Cutaneous and subcutaneous
granulomatous lesions.
• Tumor-like masses with fistules and serosanguinous exudate.
• Kunkers: Stony masses containing viable organisms and
cellular debris. - – Canine pythiosis:
-
– Canine pythiosis: Cutaneous and gastrointestinal forms.
• Cutaneous lesions typically on limbs and tail.
• GI form: ingestion, granulomatous masses develop within
intestinal wall. Most common form in dogs.
– All forms may include lymphatic and vascular invasion
with metastatic spread -
Pythiosis
⬢ Diagnosis:
⬢ Treatment: -
Pythiosis
• Diagnosis:
– Direct microscopic examination (septate-hyphae).
– Culture: requires specialized procedures.
– Serology: ELISA.
– PCR-based assays applied to tissue extracts.
– Immunohistochemistry is highly specific for hyphae.
• Treatment:
– Surgical removal of lesions.
– Chemotherapy – poor success.
– Immunotherapy – vaccine.
• Best response with early diagnosis of small
lesions. Chronic cases tend to be unresponsive. -
Disinfectants
• _____________ compounds applied to inanimate
surfaces.
– Activity ranges from ________ to ______________.
• Antiseptics are applied to tissues to ___________ or
_____________ microbial infection.
• Fa -
Disinfectants
• Germicidal compounds applied to inanimate
surfaces.
– Activity ranges from sanitation to sterilization.
• Antiseptics are applied to tissues to suppress or
prevent microbial infection.
• Factors influencing the action of disinfectants:
– Organic material.
– Other physical and environmental factors.
– Concentration and contact time.
– Type and number of microorganisms. -
Selecting and evaluating disinfectants
• EPA registration number.
• Indicated use.
– Germicide kills _________.
– General purpose disinfectant kills _________ and
____________.
– Hospital disinfectant kills _______ -
Selecting and evaluating disinfectants
• EPA registration number.
• Indicated use.
– Germicide kills Salmonella.
– General purpose disinfectant kills Salmonella and
Staphylococcus.
– Hospital disinfectant kills Salmonella, Staphylococcus,
and Pseudomonas.
• Hard water and contamination effectiveness.
• Active ingredients = disinfectant.
– Alcohols, aldehydes, acids and alkalies, quaternary
ammonium compounds, phenolics.