# Clinical Theileriosis in an Endangered Malayan Tapir Diagnosed Using a Molecular Technique with Successful Treatment and Recovery

## TL;DR

A Malayan tapir in Thailand was diagnosed with Theileria orientalis using molecular techniques and successfully treated with drugs and blood transfusion.

## Contribution

This is the first confirmed case of clinical theileriosis in a Malayan tapir, demonstrating successful treatment and highlighting the need for wildlife surveillance.

## Key findings

- Theileria orientalis was confirmed in a Malayan tapir via PCR and sequencing of the 18S rRNA gene.
- Treatment with diminazene aceturate and blood transfusion led to full recovery within 42 days.
- An 80% apparent prevalence of Theileria infection was found in sampled tapirs, with only one showing clinical signs.

## Abstract

This report describes the first confirmed case of clinical theileriosis (Theileria orientalis) in a captive Malayan tapir in Thailand. Although this pathogen is typically endemic in cattle in Asia, where it often causes asymptomatic infection, it can lead to severe clinical signs in immunocompromised animals. The affected tapir was successfully treated with an anti-protozoal drug and blood transfusion. This case highlights the importance of long-term management, routine monitoring, and effective tick control for vulnerable wildlife species.

A 12-year-old female captive Malayan tapir (Tapirus indicus) in Thailand presented with clinical signs including depression, anorexia, pale mucous membrane, dark-brown urine, dry feces, and tick infestation. Hematological analysis revealed severe anemia (packed cell volume, PCV = 9%), and blood smear examination suggested blood parasite infection, which was subsequently confirmed as Theileria orientalis using PCR targeting the 18S rRNA gene and sequencing. Treatment consisted of the administration of diminazene aceturate (2.5 mg/kg, IM, q14days for three doses), whole-blood transfusion, fluid therapy, and other supportive care. Clinical improvement was observed within three days post-treatment, including normalization of urine color and a progressive increase in PCV. By Day 42, the PCV had returned to normal (33%), with no observed complications from the medication or blood transfusion. Further screening using PCR targeting the 18S rRNA gene of piroplasmid parasites revealed an 80% apparent prevalence of Theileria infection among sampled tapirs in the same facility, although only one individual exhibited clinical signs. These findings indicate that asymptomatic carriage of T. orientalis can be observed in tapirs and that clinical disease could emerge under stress or immunocompromised conditions. Given the presence of ticks and potential contact with other susceptible species in zoo settings, routine surveillance and preventive tick control are essential for mitigating transmission risks.