CASE REPORT

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STREPTOCOCCUS EQUl INFECTION AS A CAUSE OF PANOPHTHALMITIS IN A HORSE

S. M. Barratt-Boyes; 1 R. L. Young, DVM; 1 D. D. Canton, DVM; ~ and F. C. Mohr DVM, PhD 2

S U M M A R Y

Streptococcus equi was isolated from a corneal ulcer in a horse. The ulcer developed as an extension of septic uveitis subsequent to submandibular lymphadenopathy. The condi- tion was refractory to therapy and panophthalmitis ensued. The affected eye was enucleated and S. equi was isolated in pure culture from the anterior chamber. S. equi should be considered as an etiologic agent in cases of uveitis in the horse, especially if there is a recent history of strangles.

INTRODUCTION

Streptococcus equi is the causal organism of the conta- gious upper respiratory tract disease of Equidae commonly referred to as strangles .2.4.22 The disease manifests itself as an acute febrile disorder, with inflammation of the nasal and pharyngeal mucous membranes and subsequent swelling and abscessatation of the submandibular and retropharyngeal lymph nodes. 3,19,24 Documented complications associated with S. equi infection are numerous and, with the exception of purpura hemorrhagica, generally are the result of local, hematogenous or lymphatic spread of bacteria to other sites. 6,a°,2~

Authors' addresses: 1The Veterinary Medical Teaching Hospital, and aDe- partment of Pathology, University of California, Davis, CA 95616.

The case reported here describes septic panophthalmitis caused by S. equi infection in a horse. To our knowledge this manifestation of S. equi infection has not previously been described in the literature.

CASE HISTORY

An eight year old gelding of mixed breed was referred to the Veterinary Medical Teaching Hospital with a history of uveitis of tl~ee weeks duration. The gelding and its only stablemate, an aged mixed breed mare, had previously par- ticipated in a day-long ride with 150 other horses. Fourteen days after the ride the mare had submandibular lymphad- enopathy, a purulent ocular discharge and pyrexia. Therapy prescribed by the referring veterinarian consisted of procaine penicillin G a (18,000 IU/kg, IM, daily for 5 days) and topi- cally applied genmmicin sulfate ointmenP (os, q 6 h, for 7 days). Clinical signs resolved without complication. The gelding subsequently presented with submandibular lymph- adenopathy, purulent nasal discharge and pyrexia. Procaine penicillin G therapy was instituted (18,000 IU/kg, IM, daily for 5 days). Clinical signs in the gelding apparently resolved by the completion of this therapy, however, 10 days later acute anterior uveitis was diagnosed. At that time clinical signs included blepharospasm of the left eye with marked

aPfi-Pen G; Pfizer, NY, NY. bGentacin ophthalmic ointment; Schedne Corp, Kenilworth, NJ.

Volume 11, Number 4, 1991 229

hypopyon, mucopurulent discharge from the left eye and left nostril and pyrexia (T = 39.5°(3). The cornea appeared nor- mal and did not retain topically applied fluorescein dye. c Over the following two week period the gelding was treated with procaine penicillin G (18,000 IU/kg, IM, daily), topi- cally applied neomycin-dexamethasone ophthalmic ointment d (os, q 6 h) and 1% atropine sulfate ophthalmic solution ° (os, q 6 h). Concurrently, the gelding was treated with dexamethasone f (0.04 mg/kg, IM q 12 h, for 5 days) followed by prednisoloneg (1 mg/kg, PO, q 12 h, for 7 days, then decreasing doses for 14 days). Pyrexia and nasal dis- charge ceased within a few days of starting this therapy, however, the condition of the eye deteriorated. The cornea became edematous and three stromal abscesses developed, later coalescing to form a single, large abscess with punctate holes in the overlying epithelium. Topical gentamicin sulfate therapy (os, every 6 h) was instituted. The gelding was referred to the VMTH 3 days later, which was 3 weeks after initiation of therapy for uveitis.

Clinical findings Physical examination. On presentation to the VMTH

the gelding was clinically normal except that the left eye showed marked blepharospasm with a purulent discharge. Menace response was absent. Detailed examination of the eye revealed severe keratitis with marked vascularization. A 1.5 x 1.0 cm stmmal abscess with an overlying 0.4 cm 2 corneal ulcer was present. The internal structures of the globe could not be evaluated due to corneal opacification resulting from keratitis. The prognosis for return of vision in the affected eye was judged to be extremely poor. However, the owner elected further evaluation and therapy in an attempt to save the eye.

Clinical pathology. A scraping and swab of the cornea were harvested for cytologic and microbiologic evaluation, respectively. Cytologic examination of the scraping revealed acute, septic inflammation with long chains of gram positive cocci present. Incubation of the swab on blood agar yielded very small numbers of S. equi colonies.

Treatment and course Of condition At the time of hospitalization a subl~alpebral lavage

system was placed in the upper eyelid 9 and the following medications administered via this system; gentamicin sulfate h (0.5 ml of a 16.5 mg/ml solution, q 2 h), cefazolin i (0.5 ml of a 33 mg/ml solution in artificial tear~, q 2 h) and atropine sulphate (0.5 ml, 1% q 6 h). Flunixin meglumine k (0.5 mg/kg, PO, 1 12 h) was administered concurrently. This drug regimen was maintained throughout the course of therapy.

A corneal swab taken on day 7 of hospitalization cul-

CFluor-I-Strip; Ayerst Labs Inc, NY, NY. dNeodecadron; Merck, Sharpe & Dohme, West Point, PA. °Allergan; Irvine, CA. fDexasone; Tech America, Fermenta Animal Health Co, Kansas City, MO. gBurns Vet Supply, Biocraft Labs Inc, Elmwood Park, NJ.

tured very small numbers of Pseudomonas aeruginosa sus- ceptible to gentamicin (MIC=I ug/ml). Microbiologic ex- amination of a corneal swab harvested on day 10 of hospital- ization was negative. Despite continued therapy keratitis progressed and phthisis bulbi developed. The owner autho- rized enucleation which was performed on day 13 of hospi- talization using a standard transpalpebral procedure. 8 The globe ruptured during enucleation releasing a thick, purulent material from which S. equi was isolated in pure culture. This isolate was highly susceptible to penicillin G (MIC < 0.03 mg/ml) and cephalothin (MIC < 0.5 mg/ml), a first genera- tion cephalosporin with a similar antimicrobial spectrum to cefazolin. 15 Post-operatively the gelding was treated with procaine penicillin G (18,000 IU/kg, IM, q 12 h, for 8 days) and flunixin meglumine (0.5 mg/kg, PO, q 12 h, for 5 days) and was discharged 9 days after surgery. Eighteen months after hospitalization the gelding and its stablemate had no further signs of disease.

Pathology Histopathologic examination of the enucleated eye re-

vealed extensive ulceration of the cornea which was ruptured in two areas and severely distortexi by a combination of edema, fibrin deposition, neutrophilic infiltrates and penetra- tion by new blood vessels. The anterior chamber was obliter- ated by accumulations of neutrophils, erythrocytes and macrophages and by the forward displacement of the iris and ciliary body, both of which were distorted by hemorrhage and cellular infdtrates. The posterior chamber, retina and choroid were similarly affected. The pathologic diagnosis was severe suppurative panophthalmitis with hemorrhage and comeal rupture.

DISCUSSION

Reported complications ofS. equi infection in the horse are numerous. They include metastatic abscesses in the mes- entery, 6,2°,21 kidney 11 and brain, TM 8 as well as periorbital 6,al and paravertebral ~ 7 abscesses. Reported respiratory compli- cations include upper airway obstruction, e,2~ guttural pouch empyema, 12,~4,2°,2~ lung abscessation, 8 pneumonia and pleuropneumonia.8.2~ Tenosynovitis,lS endocarditis,6 myo- carditis6.13 and laryngeal hemiplegia secondary to damage to cranial or recurrent laryngeal nerves 23 may occur. Pupura hemorrhagica is a serious and potentially fatal sequela to streptococcal infection. 1,3:°,m,2~ The etiology of this condi- tion remains to be conclusively documented; however, im- mune complexes containing IgA and S. equi - specific anti- gens have been detected in the sera of affected horses indicat- ing it may be an immune complex-mediated disease/

hGenoptic; Allergan, Irvine, CA. 'Kefzol; Eli Lily & Co, Indianapolis, IN. JAkwa Tears; Akom Inc, Abita Springs, AL. kBanamine granules; Schering Corp, Kenilworth, NJ.

230 EQUINE VETERINARY SCIENCE

The two horses in this report had no history of strangles nor any contact with other horses for five months prior to participating in the ride. It is likely, therefore, S. equi infec- tion was acquired from an infected horse at this event. The mare probably transmitted the infection to the gelding in which the initial manifestation of infection was lymphad- enopathy followed by septic uveitis.

Septic uveitis likely resulted from hematogenous spread of bacteria to the eye and not from direct spread via the cornea as hypopyon was present long before any corneal defect was detected. It is possible infection of the eye oc- curred early in the disease course with concurrent antibiotic therapy delaying the onset of septic uveitis. Progression of septic uveitis to panophthalmitis may have been facilitated by extended parenteral corticosteroid lreaunent. Topical cefazolin treaUnent late in the disease course may have only cleared the superficial cornea of streptococci. Pseudomonas aeruginosa, transiently isolated from the affected eye during antibiotic therapy, probably arose as an opportunistic patho- gen due to the altered flora of the cornea bat was eliminated by continued gentamicin therapy. The ocular discharge ob- served in the stablemate may have been due to S. equi infection, however, the actual cause of this discharge was not determined.

CONCLUSION

This case describes an unusual manifestation of S. equi infection in a horse. Septic uveitis caused by S. equi infection may be confused with non-septic uveitis in the early phases of disease.

REFERENCES

1. Baker GJ: Strangles, in Robinson NE (ed): Current Therapy in Equine Medicine, ed. 1. WB Saunders, Philadelphia, pp.24-27,1983.

2. Bazeley PL: Studies with equine streptococci V. Some relations between virulence of Streptococcus equi and immune response in the host. Aust VetJ 19:62-85,1943.

3. Blood DC, Radostits OM: Veterinary Medicine, ed. 7. Bailliere "findall, London, pp.562-565,1989.

4. Bryans JT, Doll ER, Shephard BP: The etiology of Strangles. Cornell Vet 54:198-205,1964.

5. DeLahunta A: Veterinary Neuroanatomy and Clinical Neurology. WB Saunders, Philadelphia, pp.274,360,1977.

6. Ford J, Lokai MD: Complications of Streptococcus equui infection. Equine Prac 2:41-44,1980.

7. Galan JE, ~money JF: Immune complexes in purpura hemorrhagica of the horse contain IgA and M antigen of Strepto- coccus equi. J Immunol 135:3134-3137,1985.

8. Gellatt KN, Wolf ED: Textbook of Large Animal Surgery Ed. 2. Williams and Wilkins, Baltimore, pp.655-657,1988.

9. Glaze MB: Ocular therapeutic techniques, in Robinson NE (ed): Current Therapy in Equine Medicine, ed. 2. WB Saunders, Philadelphia, pp.436-439,1987.

10. Gunson DE, Rooney JR: Anaphylactoid purpura in a horse. Vet Pathol 14:325-331,1977.

11. Jubb KVF, Kennedy PC: Pathology of DomesticAnimals. Academic Press, New York,pp. 160-161,358-359,1970.

12. KnightAP, Voss JL, McChesney AE, Bigbee HG: Experi- mentally-induced Streptococcus equi infection in horses with re- sultant guttural pouch empyema. Vet MeoYSmall Anim Clin 70:1194-1199,1975.

13. Monlux WS: Sudden death in the horse due to myocardi- tis. Iowa State Univ Vet 29:40-41,1961.

14. Nation PN: Epistaxis of guttural pouch origin in horses. Pathology of three cases. Can Vet J 19:194-197,1978.

15. National Committee for Clinical Laboratory Standards: Performance Standards for Antimicrobial SusceptibilitY Testing. NCCLS, Pennsylvania, 6 M100-S, M7-A-Sl,1989.

16. Raphel CF: Brain abscesses in three horses. JAm Vet Med Assoc 180:874-877,1982.

17. Rooney JR: Sequelae of strangles. Mod Vet Prac 60:463-464,1979.

18. Rossdale PD, Ricketts SW: Equine StudFarm Medicine, ed. 2. Balliere "findall, London, pp.430-432,1980.

19. Sweeney CR, Benson CE, Whitlock RH, Meirs DA, Bamingham SO, Whitehead SC: Streptococcus equi infection in horses - Part 1. Comp Cont Ed Prac Vet (Equine Prac) 9:689- 693,1987(a).

20. Sweeney CR, Benson CE, Whitlock RH, Meirs DA, Whitehead SC, Bamingham SO: Streptococcus equi infection in horses - Part 2. Comp Cont Ed Pract Vet (Equine Prac ) 9:845- 851,198 7(b).

21. Sweeney CR, Whitlock RH, Meirs DA, Whitehead SC, Bamingham SO: Complications associated with Streptococcus equi infection on a horse farm. JAm Vet MedAssoc 191:1446- 11448,1987(c).

22. Todd AG: Strangles. J Comp Pathol Therapeut 23:212- 229,1910.

23. Wilson WD: Streptococcus equi infections (strangles) in horses. Equine Prac 10:12-25,1988.

24. Yelle MT: Clinical aspects of Streptococcus equi infec- tion. Equine Vet J 19:158-162,1987.

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