Entamoeba invadens Myositis in a Common Water Monitor Lizard (Varanus salvator)

Abstract

Abstract. Amoebiasis is one of the most common protozoal diseases of reptiles, but amoebic myositis has not been reported in any animal species. An 11-year-old, male common water monitor lizard (Varanus salvator) was found dead with several subacute ulcerated skin wounds. Gross examination revealed multiple discrete to coalescing, white-yellow to gray, caseous foci scattered in the skeletal muscles and liver. The mucosa of small intestine was thickened, red, and contained many variably sized, dark red ulcers, with depressed and hemorrhagic centers. Histopathologic examination revealed severe necrotizing and granulomatous myositis, hepatitis, and enteritis accompanied by large numbers of intralesional, 10-20-mm diameter, periodic acid-Schiff-positive, amoeboid protozoa. Gene sequence analysis of a 136-bp region of the 18S ribosomal RNA amplified by polymerase chain reaction revealed 98-100% similarity with Entamoeba invadens. Aside from intestinal and hepatic involvement, no other internal organs were affected. The muscular infection by E. invadens likely resulted from a combination of direct invasion of trophozoites via skin wounds and hematogenous spread.

Clinical Update on Diagnosis and Management of Disorders of the Digestive System of Reptiles

“…36 Gastric ulcers can also be associated with infectious organisms (e.g., bacterial and fungal). 37 The presumptive diagnosis of gastric ulceration is based on clinical signs and anemia, but for confirmation gastroscopy is required. To treat the clinical signs of gastric ulceration, sucralfate and H 2 -blockers are recommended, in addition to reducing stress.…”

“…infections have also been reported to lead to GI tympany. 37 Fungal infections are usually secondary opportunistic infections.…”

Diagnostic Challenge

“…2 Infection is also common in chelonians and crocodilians, but rarely causes disease in these species. 3 One case of amoebic myositis with intestinal and hepatic lesions in a water monitor has been reported.² Another case series described amoebiasis in 4 ball pythons (Python regius), suspected to be infected after introduction of turtles to the zoo.…”

“…7 The life cycle of E. invadens is direct with 2 distinct life stages: (1) labile trophozoite (mobile form) and (2) resistant cyst form. 2 The host ingests the cysts via fecally contaminated food or water. 6 Upon reaching the large intestine, the cysts transform into motile trophozoites that undergo reproduction by binary fission.…”

“…However, risks can be decreased by preventing mixing of chelonians and crocodiles with snakes and lizards. 2 Additionally, appropriate quarantine periods should be used for reptiles entering a collection, and repeated clinical and fecal examinations should be performed. 8 Avoidance of mixing reptiles from different geographic areas, control of mechanical vectors, and appropriate disinfection are also recommended preventative measures.…”