Histopathological and Parasitological Evaluation of Ocular Lesions in Tehran Zoo Kangaroos: Diagnostic Findings and Clinical Implications

Subject Areas :

shadab meschian ¹ , peyman mohammadzadeh ² , siamak kakekhani ³

1 - . DVM Graduate, Faculty of Veterinary Medicine, Islamic Azad University, Sanandaj Branch, Sanandaj, Iran.
2 - Department of Pathology, Sa.C., Islamic Azad University, Sanandaj, Iran. [e-mail]
3 - Department of Pathology, Sa. C.Islamic Azad University, Sanandaj

Received: 2025-07-04 Accepted : 2025-09-13 Published : 2025-09-21

Keywords: Kangaroo, Tehran Zoo, ocular toxoplasmosis, eye lesions, parasitic infections,

Abstract :

Given the growing concerns regarding wildlife health and the potential impact of parasitic infections on zoo animals, a comprehensive assessment of ocular conditions in kangaroos was conducted to identify common lesions and their underlying causes. This study involved the examination of four kangaroo carcasses from the zoo’s refrigeration unit and 26 live red kangaroos at Eram Zoo, aged 2–10 years, stratified by sex. Under general anesthesia, ocular evaluations were performed using diagnostic tools such as an ophthalmoscope and retinoscope. Lesions were biopsied, and cytology slides were prepared for pathological assessment. Additional tests included Schirmer’s tear test, intraocular pressure measurement, and conjunctival fluorescein evaluation. istopathological assessments were specifically conducted on a male kangaroo carcass that tested positive for Toxoplasma gondii. Cytological evaluations revealed inflammatory cells, necrotic cells, and debris, indicating significant ocular surface pathology. The most common ocular lesions identified in 23 live kangaroos and 3 wallabies included eyelid trauma (4 cases), foreign body trauma (1 case), eyelid swelling due to vitamin A deficiency (8 cases), and corneal ulcers (13 cases). Notably, all 30 collected blood samples tested positive for Toxoplasma gondii, confirmed via PCR. Statistical analyses showed a significant difference in Toxoplasma load between blood and tissue samples (*p* < 0.01), with a strong correlation between PCR-positive results in blood and tissue homogenates.This study highlights the prevalence of ocular lesions in kangaroos associated with parasitic infections, particularly Toxoplasma gondii.

References:

1. Akula JD, Esdaille TM, Caffé AR, Naarendorp F. The scotopic electroretinogram of the sugar glider related to histological features of its retina. Journal of Comparative Physiology A. 2011;197:1043-54.
2. Arrese C, Dunlop S, Harman A, Braekevelt C, Ross W, Shand J, et al. Retinal structure and visual acuity in a polyprotodont marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata). Brain behavior and evolution. 1999;53(3):111-26.
3. Arrese CA, Hart NS, Thomas N, Beazley LD, Shand J. Trichromacy in Australian marsupials. Current Biology. 2002;12(8):657-60.
4. Ashton N. Ocular toxoplasmosis in wallabies (Macropus rufogriseus). 1979.
5. Attwood H, Woolley P, Rickard M. Toxoplasmosis in dasyurid marsupials. Journal of Wildlife Diseases. 1975;11(4):543-51.
6. Bakal-Weiss M, Steinberg D, Friedman M, Gati I, Avni-Magen N, Kaufman E, et al. Use of a sustained release chlorhexidine varnish as treatment of oral necrobacillosis in Macropus spp. Journal of Zoo and Wildlife Medicine. 2010;41(2):371-3.
7. Bermúdez R, Faílde LD, Losada AP, Nieto JM, Quiroga MI. Toxoplasmosis in Bennett’s wallabies (Macropus rufogriseus) in Spain. Veterinary parasitology. 2009;160(1-2):155-8.
8. Canfield P. A survey of urinary tract disease in New South Wales koalas. Australian Veterinary Journal. 1989;66(4):103-6.
9. Canfield P, Hartley W, Dubey J. Lesions of toxoplasmosis in Australian marsupials. Journal of Comparative Pathology. 1990;103(2):159-67.
10. Connolly J, Krockenberger M, Malik R, Canfield P, Wigney D, Muir D. Asymptomatic carriage of Cryptococcus neoformans in the nasal cavity of the koala (Phascolarctos cinereus). Medical Mycology. 1999;37(5):331-8.
11. Dubey J, Ott-Joslin J, Torgerson R, Topper M, Sundberg J. Toxoplasmosis in black-faced kangaroos Macropus fuliginosus melanops. Veterinary Parasitology. 1988;30(2):97-105.
12. Funnell O, Johnson L, Woolford L, Boardman W, Polkinghorne A, McLelland D. Conjunctivitis associated with Chlamydia pecorum in three koalas (Phascolarctos cinereus) in the Mount Lofty Ranges, South Australia. Journal of Wildlife Diseases. 2013;49(4):1066-9.
13. Govendir M. Review of some pharmacokinetic and pharmacodynamic properties of anti‐infective medicines administered to the koala (Phascolarctos cinereus). Journal of veterinary pharmacology and therapeutics. 2018;41(1):1-10.
14. Hanger J, Loader J, Wan C, Beagley KW, Timms P, Polkinghorne A. Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus). The Veterinary Journal. 2013;195(3):391-3.
15. Hirst LW, Brown AS, Kempster R, Hall J, Woolcock JB. Keratitis in free-ranging koalas (Phascolarctos cinereus) on Magnetic Island, Townsville. Journal of Wildlife Diseases. 1992;28(3):424-7.

16. Hooper P, Lunt R, Gould A, Hyatt A, Russell G, Kattenbelt J, et al. Epidemic of blindness in kangaroos‐evidence of a viral aetiology. Australian Veterinary Journal. 1999;77(8):529-36.
17. Johnson A, Roberts H, Munday B. Prevalence of Toxoplasma gondii antibody in wild macropods. Australian veterinary journal. 1988;65(7):199-201.
18. Kern T, Colitz C. Exotic animal ophthalmology. 2012.
19. Krockenberger M, Canfield P, Malik R. Cryptococcus neoformans var. gattii in the koala (Phascolarctos cinereus): a review of 43 cases of cryptococcosis. Medical Mycology. 2003;41(3):225-34.
20. Labelle AL, Low M, Hamor RE, Breaux CB, Langan JN, Zarfoss MK, et al. Ophthalmic examination findings in a captive colony of western gray kangaroos (Macropus fuliginosus). Journal of Zoo and Wildlife Medicine. 2010;41(3):461-7.
21. Liddle VL. Electroretinography in the normal koala (P hascolarctos cinereus). Veterinary Ophthalmology. 2015;18:74-80.
22. Miller DS, Faulkner C, Patton S. Detection of Toxoplasma gondii IgG antibodies in juvenile great grey kangaroos, Macropus giganteus giganteus. Journal of Zoo and Wildlife medicine. 2003;34(2):189-93.
23. Miller MA, Ehlers K, Dubey J, Van Steenbergh K. Outbreak of toxoplasmosis in wallabies on an exotic animal farm. Journal of Veterinary Diagnostic Investigation. 1992;4(4):480-3.
24. Oria AP, Raposo AC, Araujo NL, Romano JV, Martins-Filho EF, Gomes D, et al. Evaluation of tear production in juvenile opossum using three different methods. Pesquisa Veterinária Brasileira. 2019;39(01):61-5.
25. Parameswaran N, O'HANDLEY R, Grigg M, Wayne A, Thompson R. Vertical transmission of Toxoplasma gondii in Australian marsupials. Parasitology. 2009;136(9):939-44.
26. Portas TJ. Toxoplasmosis in macropodids: a review. Journal of Zoo and Wildlife Medicine. 2010;41(1):1-6.
27. Speight KN, Polkinghorne A, Penn R, Boardman W, Timms P, Fraser T, et al. Prevalence and pathologic features of Chlamydia pecorum infections in South Australian koalas (Phascolarctos cinereus). Journal of wildlife diseases. 2016;52(2):301-6.
28. Stanley RG. Marsupial ophthalmology. Veterinary Clinics: Exotic Animal Practice. 2002;5(2):371-90.
29. Suedmeyer WK, Pearce J, Persky M, Houck ML. Peters anomaly in a red kangaroo (Macropus rufus). Journal of Zoo and Wildlife Medicine. 2014;45(3):715-8.