Oxyurid Infection in Indian Star Tortoises (Geochelone elegans)

Introduction

The Indian Star Tortoise (Geochelone elegans) is a well-recognized terrestrial reptile species endemic to the Indian subcontinent. Its most distinguishing feature is the star-like pattern formed by radiating yellow lines on a dark brown or black carapace. This cryptic coloration is not only attractive but also serves as camouflage in its natural habitat. The species is widely distributed across India, particularly in the semi-arid regions of Gujarat, Rajasthan, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, and Odisha. It inhabits dry scrublands, thorn forests, and grasslands, often relying on seasonal vegetation and scattered water sources. Ecologically, the Indian Star Tortoise plays a vital role as a seed disperser and grazer, aiding in vegetation control and habitat dynamics. However, its populations are increasingly threatened due to habitat destruction, illegal wildlife trade, and unsustainable capture for the exotic pet market. Consequently, the species is listed as "Vulnerable" by the IUCN Red List and is protected under Schedule IV of the Wildlife (Protection) Act, 1972 in India. Apart from anthropogenic threats, infectious and parasitic diseases also pose significant but often underappreciated risks to wild and captive tortoise populations. Parasitic infections are particularly important in chelonians due to their coprophagic habits and frequent contact with contaminated substrates, especially in confined environments. Among various gastrointestinal parasites, nematodes of the family Oxyuridae are frequently reported in tortoises and other herbivorous reptiles. Oxyurids, such as Pharyngodon and Tachygonetria spp., reside in the large intestine and cloaca and typically follow a direct life cycle, involving the ingestion of embryonated eggs from the environment. Though often subclinical, heavy infestations can lead to cloacal inflammation, prolapse, secondary infections, and poor condition in stressed or immunocompromised individuals (Frye, 1991; Jacobson, 2007) [2,3] . This report presents a case study of oxyurid egg detection in Indian Star Tortoises screened between 2023 and 2025 during routine health surveillance activities at a wildlife rehabilitation facility in central India.

Case Reports: A total of fifteen Indian Star Tortoises (Geochelone elegans) were examined between April 2023 and March 2025 at the Wildlife Research and Training Centre (WRTC), Gorewada, Maharashtra including samples submitted by various rescue centres and zoos of Maharashtra state. These tortoises had been rescued from illegal trade operations, relocated from urban conflict zones, or transferred from temporary shelters. The animals were maintained under controlled conditions with adequate space, basking platforms, clean water access, and a vegetarian diet consisting of greens, vegetables, and seasonal fruits. To assess parasitic burden, faecal samples were collected non-invasively from each tortoise over a two-day period. The fresh droppings were placed in labelled sterile containers and transported to the parasitology laboratory under refrigerated conditions. Samples were processed within 6-12 hours of collection using standard faecal flotation techniques. Approximately 2 grams of faeces was homogenized in saturated sodium chloride solution (specific gravity ~1.20) and transferred to test tubes. Cover slips were placed on the meniscus and left undisturbed for 20 minutes before microscopic examination under 10× and 40× objectives. Out of the fifteen samples analyzed, six (40%) were found positive for oxyurid eggs. The eggs appeared oval to ellipsoidal with smooth, thick shells, a single operculum at one pole, and measured around 80-100 µm in length. The internal embryo occupied most of the egg space, consistent with descriptions of Tachygonetria and Pharyngodon spp. No other helminth ova or protozoan oocysts were observed in any of the samples. Notably, all six tortoises harboring oxyurid eggs were clinically normal at the time of examination. They displayed good appetite, active movement during basking hours, and no signs of weight loss, diarrhoea, cloacal prolapse, or discharge. The enclosures housing these individuals were regularly cleaned, but the reuse of soil substrate was noted, which could serve as a source of reinfection.

Discussion

Oxyurid infections in tortoises have been frequently reported across both wild and captive populations. In Indian contexts, Acharjyo (2004) [1] reported gastrointestinal helminths including oxyurids in reptiles from zoos in Odisha. More recently, Mohanty et al. (2016) [4] documented the presence of Tachygonetria spp. in captive chelonians at Nandankanan Zoological Park. Globally, oxyurids have been described in various tortoise species including the Greek tortoise (Testudo graeca), Russian tortoise (Agrionemys horsfieldii), and Redfooted tortoise (Chelonoidis carbonarius). Wellehan and Gunkel (2004) [5] emphasized the re-emergence of parasitic infections in captive reptiles due to increased animal movement, stress, and biosecurity lapses.

Although oxyurid infections are often asymptomatic in healthy reptiles, their pathogenic potential increases under poor husbandry, immunosuppression, or high parasite burdens. These nematodes can cause mechanical irritation of the cloaca and lower intestine, leading to inflammation and, in severe cases, prolapse. Secondary bacterial or fungal infections may ensue if mucosal damage occurs. Chronic infections may also contribute to weight loss and delayed growth in juveniles. However, in the present study, all infected tortoises remained asymptomatic, suggesting a low to moderate parasitic burden and good overall host condition. The detection of oxyurid eggs in 40% of the examined tortoises is significant for multiple reasons. First, it confirms the endemic presence of oxyurids in captive Indian Star Tortoise populations. Second, it highlights the potential for parasite persistence and spread within enclosures, particularly if sanitation is suboptimal. The coprophagic and groundforaging nature of tortoises increases their exposure to contaminated fecal material. Third, since infected individuals may appear clinically normal, the role of routine fecal examinations as part of preventive veterinary care cannot be overemphasized.

Management of oxyurid infections includes regular fecal screening, rotational enclosure cleaning, and use of safe anthelmintics. Fenbendazole (50-100 mg/kg PO once daily for 3-5 days) is commonly used and effective against adult oxyurids and migrating larvae. Hygiene measures such as removal of old substrate, minimizing overcrowding, and individual quarantine of new arrivals reduce the risk of reinfection. Additionally, as molecular tools become more accessible, PCR-based identification of parasite species can help monitor parasite diversity and detect emerging strains. From a conservation perspective, parasitic monitoring is essential, especially in facilities engaged in rehabilitation, conservation breeding, or reintroduction of threatened species.

Infections that are benign in captivity may become exacerbated post-release in wild populations or contribute to pathogen spill over into sympatric wildlife. In conclusion, this case report contributes to the growing body of evidence on parasite ecology in Indian reptiles. It underscores the importance of non-invasive surveillance and responsible husbandry in ensuring the health of Indian Star Tortoises, a species already under stress from anthropogenic pressures.

Acknowledgement

AcknowledgementsThe authors are thankful to the Director, Wildlife Research & Training Centre, Gorewada, Nagpur, for facilitating the research work. The authors gratefully acknowledge the kind approval of the Hon'ble Principal Chief Conservator of Forests (Wildlife) & Chief Wildlife Warden, Maharashtra State, for permitting the conduct of this research. We extend our sincere thanks to the Forest Development Corporation of Maharashtra Ltd., Nagpur, and the Office of the CEO, FGZ Ltd., and Divisional Manager, Gorewada Project, Nagpur, for providing necessary facilities for the study. We acknowledge the ResQ CT, Pune for the submission of samples for routine health examination.

References

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