Muscular Microsporidiosis in a Gecko

Kelli Boyd and Christopher R. Gregory

Departments of Veterinary Pathology (Boyd) and Small Animal Medicine (Gregory) College of Veterinary Medicine, University of Georgia, Athens, GA, USA

Abstract: A male leaf-tailed gecko was found dead at a regional major metropolitan zoo. Histologically, the lizard had diffuse myositis with intralesional microsporidia. Microsporidial organisms were not present in any other examined organ system or tissues. To our knowledge this is the first report of microsporidiosis in a gecko in the United States and the only report of strictly muscular microsporidiosis in a reptile.

Keywords: Lizard, Gecko, Microsporidiosis, Myositis

Case History

A male leaf-tailed gecko (Uroplatus henkeli) was found dead at a regional major metropolitan zoo. No clinical signs were observed prior to death. The gecko was fixed in 10% neutral-buffered formalin and submitted to the University of Georgia College of Veterinary Medicine Infectious Diseases Laboratory Zoo and Exotics Pathology Service. Grossly, the reptile appeared thin but no other abnormalities were observed.

Microscopic Examination

The normal skeletal muscle architecture was effaced by intense infiltrates of histiocytic macrophages, lymphocytes, plasma cells and heterophils. Myofibers were necrotic and fragmented and have plump oval nuclei with one or two prominent nucleoli. Macrophages contained clusters of lightly basophilic organisms with a small clear halo. These organisms were tissue gram stain and acid-fast positive. They were not observed in other organ systems including kidney, brain, lung, liver, heart, or intestinal tract.

Figure 1. Skeletal muscle 100X H&E: Extensive mononuclear infiltrate in skeletal muscle.	Figure 2. Skeletal muscle 400X H&E stain. Mononuclear inflammation and muscle necrosis and fragmentation. Arrows point to intracytoplasmic organisms in macrophages.

Figure 3. Skeletal muscle 1000X Acid fast stain. Acid fast organisms within macrophages.

Figure 4. Encephalitazoon cuniculi: extruded polar filament.	Figure 5. Encephalitazoon cuniculi: coiled polar filament, thin wall with endospore, arrow and exospore arrowhead

Discussion

Microsporidia are obligate intracellular protozoa that infect a wide variety of invertebrates and all classes of vertebrates. They enter the host cell through mechanical forces of an extruded polar filament from the sporoplasm. The sporoplasm then actively migrates through the host tissue. ¹ Organisms multiply in cytoplasmic vacuoles. The life cycle is composed of a merogonic phase and a sporogonic phase. During merongony the organisms retain a simple structure which evolves into a more complex structure during sporogeny. In histologic sections these organisms are about 2-3 µm in diameter and typically observed within the host cell cytoplasm. They will stain gram-positive and will refract polarized light. These organisms also will stain positive with tissue acid-fast stains. The single polar granule will stain positive with periodic acid-Schiff stain. Ultrastructurally, microsporidian spores have a thin wall consisting of an endospore ,an exospore, and a coiled polar filament. Diagnosis of this organism is based on demonstration of the parasite in tissue sections. ²

In the United States, this organism has been reported in bearded dragons (Pogona vitticeps). Other reports of microsporidia species in reptiles include cases in a common wall lizard (Podarcis muralis) in France, a European grass snake (Natrix natrix) in Italy, and the split keelback snake (Atretium schistosum) in India. ³ In mammals, microsporidiosis is most commonly reported in rabbits and in human patients infected with human immunodeficiency virus. ⁴ To our knowledge this is the first report of microsporidiosis in a gecko and the only report of the infection localized to skeletal muscle in a reptile. Speciation of this organism was not possible due to limited amount of tissue. Localization of this infection to muscles is unusual and may indicate that the gecko is not the natural host for this organism.

References

1. Percy DH, Barthold SW. 1993. Pathology of Laboratory Rodents and Rabbits pp. 210-214. Iowa State University Press, Ames IA.

2. Wasson K, Peper RL: Mammalian microsporidiosis. Vet Pathol 2000 Mar;37(2):113-28

3.Jacobson ER, Green DE, et al: Systemic Microsporidiosis in Inland Bearded Dragons (Pogona vitticeps). Journal of Zoo and Wildlife Medicine 29(3): 315-323, 1998.

4. Mathis A, Michel M, et al: Two Encephalitozoon cuniculi strains of human origin are infectious to rabbits. Parasitology 114:29-35 199

This Page Last Updated October 16, 2000

^  Top of page