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THE UNIVERSITY OF TENNESSEE COLLEGE OF VETERINARY MEDICINEDEPARTMENT OF <<INSERT DEPARTMENT NAME HERE ON MASTER SLIDE>>
Diane Hendrix, DVM, DACVO
Professor of Ophthalmology
University of Tennessee
Parasites
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Toxoplasma gondii
Neospora caninum
Encephalitozoon cuniculi
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Toxoplasmosis• Toxoplasma gondii• Affects most warm-blooded animals• Obligate intracellular protozoa• The cat is the definitive host
cmgm.stanford.edu/.../boothroydlabdesc.html
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Asexual life cycle
Animals (including cats)→ ingest bradyzoites → transform to tachyzoites → penetrate intestinal mucosa → spread throughout the body → cause disease → encyst and become bradyzoites
Toxoplasmosis
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Sexual life cycle• Limited to the cat
• In cats →ingestion of bradyzoites → transform to tachyzoites → penetrate intestinal mucosa → start intra-epithelial cycle of sexual proliferation →oocysts→shed in the feces
Toxoplasmosis
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Immunity
• Tissue damage
• Cellular immune memory
• T-cell mediated immunity
• IgM, IgG, IgA and IgE are produced against both the membrane and intracellular proteins.
Toxoplasmosis
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Ocular disease in humans
• Reactivations of congenitally acquired infection
• Retinitis is pathognomonic
• Anterior uveitis is rare
Toxoplasmosis
Progress in Retinal and Eye Research 39 (2014) 77e106
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Disease in cats
• Clinical signs vary
• In adults illness is usually subclinical.
Toxoplasmosis
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In kittens, tachyzoites spread systemically & cause:– Interstitial pneumonia– Myocarditis– Hepatic necrosis– Meningoencephalomyelitis– Chorioretinitis– Lymphadenopathy– Myositis
• Immunocompromised adult animals are susceptible to developing acute generalized toxoplasmosis.
Toxoplasmosis
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Ocular lesions in cats
Toxoplasmosis
• Multifocal chorioretinitis
• Anterior uveitis
• Optic neuritis
• Histopathology
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The role of toxoplasmosis in causing anterior uveitis in cats
without systemic illness is controversial.
Toxoplasmosis
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• Diagnosis
– Isolation – Histologic
identification– Serologic evaluation
– C value of >8 – PCR
• Treatment
– Clindamycin
Toxoplasmosis
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• Approx 4 mos old female DSH
• Underweight, aged via dental exam
• Menace – OU, dazzle - OU
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• In both retinas there were areas of – active chorioretinitis with hyporeflectivity and
retinal hemorrhages
– hyperreflectivity with inactive chorioretinitis.
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• TV=0=positive (either acute infection or antibodies from the queen)
• + for cystoisospora on fecal
• Ponazuril (50mg/ml) oral suspension @ 15mg/kg PO SID for 28 days
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• Within 3 weeks – Weight gain
– Minimal vision had returned
– Lesions were all inactive
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Encephalitozoon cuniculi
• Obligate intracellular microsporidium• Wide host distribution• Primarily affects rabbits• Opportunistic in immunocompromised
humans• Eyes, CNS, and kidneys are predilection
sites
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Pathogenesis
• Sporulating eukaryotic protozoa– Infective spores are shed in the urine.– The spore survives in the environment and is
the transmissible agent.
• Infection has occurred via intravenous, intracerebral, oral, nasal, and rectal routes and vertical transmission.
• Dwarf rabbits and NZW may be more susceptible.
Encephalitozoon cuniculi
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Clinical disease in rabbits
• Phacoclastic uveitis
– Cataracts– Whitish/yellowish
intraocular masses (granulomas)
– Anterior uveitis – Hyperemia– Unilateral
Encephalitozoon cuniculi
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Other clinical disease in rabbits
– Granulomatous encephalitis– Nephritis with kidney failure
• Typical disease pattern is a subclinical, chronic, persistent infection.
Encephalitozoon cuniculi
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Diagnosis
• Histopathology and demonstration of organisms is required to confirm infection.
• Tentative diagnosis made on clinical signs in combination with serological testing.
Encephalitozoon cuniculi
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Treatment for Phacoclastic Uveitis
• phacoemulsification• steroids have little to no
effect• fenbendazole PO QD • enrofloxacin or
oxytetracycline may be used in rabbits showing neurological signs
• +/- corticosteroids
Encephalitozoon cuniculi
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Prognosis
• Rabbits with phacoclastic uveitis do not show other symptoms and survive.
Encephalitozoon cuniculi
• ½ the rabbits with neurological signs recover
• Those with kidney failure die
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Histopathology (Ocular)
• Pyogranulomatous infiltration• Zonal inflammatory pattern• The anterior uvea is relatively spared• Organisms are only found within
liquefied lens cortex• Microsporidia are apparent with silver
stain and are Gram + and acid-fast• Immunohistochemistry
Encephalitozoon cuniculi
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Encephalitozoon cuniculi
Disease in Cats
• Diagnosed in several cats
• Median age 3.5 years
• Most bilateral
• Cataracts varied from incipient to mature
• Treated with phaco and fenbendazole
• Diagnosed on histopath and PCR
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VO pp 37-47, 16 SEP 2011
Encephalitozoon cuniculi
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Encephalitozoon cuniculi
Other species• Blue fox - cataracts
• Mink - cataracts
• Humans develop keratoconjunctivitis, keratitis, uveitis and endophthalmitis.
• Snow leopard
Vet Ophthalmol. 2015 Jan;18 Suppl 1:143-7
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PARASITIC FLAGELLATES
Trypanosoma sp.
Cryptobia (T.) salmositica
Leishmania infantum
jcs.biologists.org/.../issue12/cover.shtml
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Trypanosomiasis
• Trypanosoma sp.• Hemoflagellate
protozoan• Transmitted by the
tsetse fly• Flies inoculate the skin
web.indstate.edu/.../parasitology/PROTOZHO.HTM
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• Immune complexes cause inflammation
• When antibodies are made against the surface-coat glycoproteins the trypanosomes die.
• Trypanosomes have multiple genes that code for different surface-coat glycoproteins that are not vulnerable to the immune response resulting in persistence of the organism.
Trypanosomiasis
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Disease in dogs and cats
• Trypanosoma brucei
– corneal opacification
– blepharitis
– conjunctivitis
– ciliary body cysts may contain organisms
• The disease occurs in Africa
http://pathmicro.med.sc.edu/parasitology/blood-proto.htm
Trypanosomiasis
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Disease in dogs and cats• Trypanosoma evansi
– corneal opacities
– conjunctivitis
– blepharitis
– anterior uveitis
– endophthalmitis
• transmitted by biting flies
• North Africa, the Middle East, Asia, the Far East, and Central and South America
Trypanosomiasis
http://congohounds.gorillacd.org/2012/04/08/bloodhound-teams-learn-to-deal-with-common-nuisances-tsetse-flies-and-trypanosomes/
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Disease in livestock• Sub-Saharan Africa, Asia
and South America
• Relapsing hypopyon
• Eyelid edema
ww
w.u
ogue
lph.
ca/~
pwoo
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mal
tryp
.jpg
Trypanosomiasis
• Histologic examination• trypanosomes in the
fibrin of the anterior chamber and anterior uvea
• mononuclear inflammatory infiltrate
• Aqueocentesis may demonstrate trypanosomes
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Leishmaniasis• Flagellate organism• Leishmania infantum• Endemic on Mediterranean shore and
in parts of east Africa, India, and Central and South America.
• +/- USA– Domestic and wild members of Canidae
serve as reservoir hosts– Intermediate host, a sandfly (Phlebotomus
spp.), is also found in USA
geo.arc.nasa.gov/.../diseases/images/leish.gif
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Ocular signs
Arq. Bras. Med. Vet. Zootec. vol.58 no.5 Belo Horizonte Oct. 2006
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Systemic signs• Lymphadenopathy• Splenomegaly• Hepatomegaly• Renal failure• Anemia• Thrombocytopenia• Muscular weakness• Cachexia• Abnormal locomotion• Varying non-pruritic dermatologic conditions
www.liv.ac.uk/.../issue18/images/W046387R.jpg
Leishmaniasis
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Histopathology
• Vasculitis and intense inflammatory zones
• Amastigotes are seen in the ciliaryprocesses, ciliary body, limbus, lacrimal duct and histiocytes.
Leishmaniasis
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Diagnosis and Treatment
• ID on histopathologic or immunoperoxidase evaluation of biopsies
• ELISA and IFA
• PCR
• Allopurinol
Leishmaniasis
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Disease in cats
• Conjunctivitis
• Blepharitis
• Keratitis
• Amastigotes are found within macrophages and giant cells
Leishmaniasis
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OTHER PARASITIC INFECTIONS
Habronemiasis
Ocular filariasis
Ocular larval migrans
Onchocerciasis
Ophthalmomyiasis
Thelaziasis
Cuterebra
Vet Parasitol. 2015 Feb 28;208(1-2):84-93
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Habronemiasis
• Parasite of the equine stomach
– Draschia megastoma– Habronema muscae– Habronema microstoma
• Adults are 13 mm to 25 mm long
• Normal life cycle goes through the stomach
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Cutaneous Habronemiasis
• Initial rapid production of granulation tissue
• Does not resolve during fly season
• Sulfur granules
• Severe pruritus
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Habronema conjunctivitis
• Ulcerated nodules
– Contain caseo-calcareous foci – Located near the medial canthus– Tend to abrade the cornea
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Treatment
• Surgical removal if irritating• Ivermectin is the treatment of choice• Fenbendazole
Habronemiasis
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• Adult dromedary camel
• Non-healing, severely pruritic, ulcerative fibrotic plaque
• Degenerating nematode larvae within eosinophilicgranulomas
• Treatment
– repeated debridement – injectable ivermectin– anti-inflammatory
therapies– injectable and topical
antibiotics
Habronemiasis
Veterinary Dermatology, 21, 527–530
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Habronema in a rhino• A captive female square-lipped rhinoceros • Intermittent signs of bilateral conjunctivitis and
conjunctival proliferation• Treatment with antibiotics and glucocorticosteroids
was ineffective, as were repeated dewormings. • Biopsies in 2000 & 2006 only showed eosinophils • After progression to vision loss aggressive
resection was done.• 2013 biopsy showed severe allergic conjunctivitis,
eosinophilic granuloma, and habronematid(Habronema or Draschia) larval infection.
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VO 28 MAR 2015 DOI: 10.1111/vop.12269
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Ocular nematodiasis
• Intraocular nematodiasis is infrequent
• Includes two distinct conditions
– ocular filariasis
• Dirofilaria immitis
• Angiostrongylus vasorum
– ocular larval migrans
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Ocular filariasis
• aberrant migration of immature nemotodes
• dogs and humans• +/- concurrent
microfilaremia• ocular signs result
from aberrant migration • German Shepherds
may be predisposed
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• Ocular involvement is unilateral
• Worm is usually in AC
– Anterior uveitis (signs worsen with exam)
– Severe corneal edema – Mild to severe corneal
opacity
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• Uveitis
• Antigen-antibody complex formation may play a role
• Typically, one 5- to 10-cm filaria is seen undulating in the anterior chamber
• Light stimulation increases motility of the filaria
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Prognosis for nematodiasis
• Favorable with anti-inflammatory therapy and manual removal of the filaria.
• Presurgical adulticide therapy is not advised
• Microfilaricide administration causes increased activity of the filaria and transient exacerbation of clinical signs in one case
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Mid East Afr J Ophth. 2014;21:312-6. doi: 10.4103/0974-9233.142267.
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Ocular larval migrans• Aberrant ocular migration of Toxocara spp.
• T. canis is most commonly involved
• Public health significance, as the nematode causes OLM and VLM in children
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Aberrant migration
• L3 form which typically migrates to the lung from the stomach aberrantly migrates to the eye
• Toxacara has propensity for the eye
• OLM causes inflammation primarily of the retina and vitreous Image and text copyright © Dennis Kunkel
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Ophthalmoscopy
• Hyperreflectivity• Hyperpigmentation• Vascular
attenuation• Small, solitary
focal granulomas• Orbital cellulitis• Rare anterior
uveal involvement
http://cueflash.com/decks/17_-_Nematodes
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http://www-ncbi-nlm-nih-gov.proxy.lib.utk.edu:90/pubmed/14641832#
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Onchocerciasis
http://www.mectizan.org/lifecycle.asp
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Disease in dogs
• O. lupi
• Acute ocular signs
• Chronic ocular signs
– Granulomatous nodules – Masses in the conjunctiva, nictitans, and
sclera – Uveitis– Periorbital swelling– Exophthalmos
Onchocerciasis
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Onchocerciasis
Courtesy: Dr. Nancy McLean
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Onchocerciasis
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VO 2015 DOI: 10.1111/vop.12277 characteristic ridges on the cuticle Greece
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Parasit Vectors. 2015 Feb 8;8:89
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Vet Parasit, Vol 203, 1–2, 2014, 91–95 asymptomatic dog pos on skin snip test.
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Disease in horses
• Small (<1 mm), raised, white nodules
• Depigmentation temporal bulbar conjunctiva
• Corneal edema and punctate/streaking opacities of the stroma
• May be an association with the microfilariae and ERU
Onchocerciasis
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Histopathology
• Pyogranulomatous nodules with eosinophils
• Lymphoplasmacytic uveitis
• Microfilariae in the uteri of females
• Can be isolated from skin biopsy specimens
Onchocerciasis
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Histopathology
Onchocerciasis
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Treatment
• No treatment is effective against the adults.
• Ivermectin and moxidectin -microfilarae
Onchocerciasis
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Disease in cats
• Orbital disease
• Western US
• Posterior episcleral parasites
• No suspicion of disease
• O lupi
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Ophthalmomyiasis
• Order Diptera• Ophthalmomyiasis externa
• Ophthalmomyiasis interna anterior
• Ophthalmomyiasis interna posterior
• Aberrant ocular migration of fly larvae
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• Thought that fly larvae cross the conjunctival surfaces
• Seen as an incidental finding
• Can be found in the acute stages with uveitis
• Diagnosis – visualization of the larvae in
the anterior or posterior segments
– wandering tracks in the fundus
Ophthalmomyiasis
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Ophthalmomyiasis interna posterior
• Dogs, cats, and humans• Characteristic lesion is
road-map-like subretinal tracts that may be active or inactive– Active disease may be
associated with uveitis, retinal detachment, and hemorrhage
– The larva may be visible in active infections
Ophthalmomyiasis
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Treatment
• Inactive infections require no therapy
• Active disease
– Anti-inflammatory therapy– Organophosphates – The larva may spontaneously depart – Physical removal of the larvae from the
anterior chamber – Laser therapy or killing the larvae while in
the eye is not recommended
Ophthalmomyiasis
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Ann Emerg Med. 2015 Jun;65(6):e7-8.
Man with pain in left eye. Ophthalmomyiasis from the sheep nasal bot fly, Oestrus ovis. Endemic in Israel.
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VO 17, 6, pages 448-453, 3 SEP 2014 DOI: 10.1111/vop.12210
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Can J Ophth 46;6, 2011, 553–554
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Thelaziasis
• Milky-white worms ~ 10-14 mm long
•http://path.upmc.edu/cases/case279/images/fig01a.jpg• Multiple species.
• Western USA, Europe and southeast Asia
• Lateral serrations of the cuticle cause mechanical damage
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Life Cycle
• 1st stage larvae are ingested by flies
• Then after undergoing 2 molts, the 3rd stage larvae are transferred back to the eye when the fly feeds.
• Adults live under the eyelids or behind the nictitans
Thelaziasis
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Dogs
• T. callipaeda and T. californiensis
Dr. Rebecca Burwell
Thelaziasis
• Clinical signs• Unilateral or bilateral
purulent conjunctivitis
• Blepharospasm• Epiphora• Conjunctivitis• Keratitis• Intense lacrimal
secretion
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T. californiensis
• North America
• Dogs, mule deer, and others.
• The vectors: Musca spp. and Fannia spp.
• Increased international trade and travel
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Dogs
Treatment
– Topical levamisol (2% aqueous solution)– SQ ivermectin– Physical removal of the nematodes– Prophylactics – spot on formulation vs
collar vs milbemycin oxime/proziquanteltablets
Thelaziasis
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Cats
Vet Parasitol. 2014 Jul 14;203(3-4):287-93
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Horses and Cattle
Horses - T. lacrymalis
Cattle - T. gulosa, T. skrjabini, and T. rhodesii
Thelaziasis
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Horses and Cattle
• Lacrimal glands and ducts
• Superficial locations on the cornea, in the conjunctival sac, and under the eyelids and nictitating membrane.
• Worms may also be found on the periorbital hair or skin during anesthesia or following migration after death of the host.
Thelaziasis
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Horses and Cattle• Often asymptomatic
• Invasion of the glands and ducts may cause inflammation and necrotic exudation.
• Conjunctivitis and blepharitis are common.
• Keratitis may develop in severe cases, particularly with T. rhodesii infections in cattle.
• Subconjunctival cysts may also develop in cattle.
Thelaziasis
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Diagnosis• Gross inspection of the
eyes (esp for T. rhodesii)
• Others tend to be more evasive
• Topical anesthetics allow for tissue manipulation
• Microscopic examination of tears for embryonatedeggs or larvae may be done
Thelaziasis
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THE UNIVERSITY OF TENNESSEE COLLEGE OF VETERINARY MEDICINEDEPARTMENT OF <<INSERT DEPARTMENT NAME HERE ON MASTER SLIDE>>
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