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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

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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>>