Tortoise Upper Respiratory Tract Disease: Workup and Treatment

PublishedAugust 18, 2026Reading time9 minExoticRx Editorial

Editorially reviewed against published veterinary references. Awaiting credentialed clinical reviewer — our editorial process.

A tortoise with nasal discharge is the reptile-medicine presentation you'll see most often this year if you do exotic work. Most are some flavour of upper respiratory tract disease (URTD). The complication is that "URTD" is a syndrome, not a diagnosis — Mycoplasma agassizii and M. testudineum are the headline pathogens but they're not the only ones, and the management changes meaningfully when you identify the agent.

This article is the workup and treatment guide. It assumes you've already taken the patient on (a tortoise with nasal discharge isn't a 5-minute consult), and walks through what to test, what the results change, and what to dispense.

The differential

Causes of URTD-like signs in chelonians:

• Mycoplasma agassizii — most common in desert tortoises and some box turtles; well-characterised; chronic/recrudescent
• Mycoplasma testudineum — a separate pathogen, less common; similar clinical picture
• Herpesvirus (testudinid herpesvirus, THV) — severe, often with diphtheritic plaques in oral cavity and stomatitis. Different management.
• Mycoplasma testudineum + Pasteurella testudinis + secondary aerobes — mixed infections common in chronic cases
• Iridoviruses (Ranavirus) — emerging concern; rapid progression, multi-system disease
• Picornavirus / Tortoise Virus X — particularly in European tortoise rescues
• Foreign body / nasal trauma — unilateral discharge in a previously well animal
• Husbandry-driven: low temperature, dry environment, poor ventilation, poor diet (vitamin A deficiency in particular)

Husbandry is on the differential because suboptimal POTZ + dehydration + vitamin A deficiency produces clinical signs that look identical to infectious URTD and respond to husbandry correction without antibiotics. Always assess husbandry first.

Clinical signs

The presentation:

• Bilateral nasal discharge (clear → mucoid → mucopurulent as disease progresses)
• Nasal crust formation at the nares
• Conjunctivitis, often bilateral, sometimes with palpebral edema
• Open-mouth breathing in severe cases
• Stomatitis (oral plaques) — particularly suggestive of herpesvirus
• Anorexia, lethargy, decreased basking
• Loss of body condition in chronic cases
• History of being a recent rescue, attending a tortoise show, or being added to a multi-tortoise enclosure — significant for the infectious differential

Workup — what to do, in order

Husbandry assessment first

Get the husbandry history before you go to diagnostics. The most useful questions:

• POTZ (preferred optimum temperature zone) for this species, and what the owner is actually providing — measure the basking spot temperature directly if possible
• UV-B source — type, age, distance from basking spot. Most owners under-replace UV-B bulbs.
• Hydration access — bath frequency, drinking water visible
• Diet — fibre source, calcium-to-phosphorus ratio, vitamin A sources (dark leafy greens, squash, etc.)
• Recent additions to the enclosure — new tortoises, new substrate, new plants
• Temperature swings overnight
• Outdoor housing — recent cold snap?

A patient with a 3-month history of nasal discharge whose owner recently moved them indoors with no UV-B and a 4-year-old MVB bulb may need husbandry correction more than antibiotics.

Physical exam

• Body weight (compare to known healthy weight if possible)
• Conjunctival tissue swelling/ocular discharge
• Oral exam — look for diphtheritic plaques, glossitis, stomatitis. Vitamin A deficiency produces metaplasia of the squamous epithelium with characteristic plaques. Herpesvirus also produces plaques but with more necrosis.
• Lung auscultation — useful in larger chelonians; bring a stethoscope to the cranial pleural space. Limited in small tortoises.
• Body temperature — measure cloacally; many anorexic chelonians are hypothermic and need warming before workup proceeds.

Bloodwork

Minimum useful set:

• PCV — anemia in chronic infection
• Total protein — usually elevated in chronic chelonian infection
• White cell estimate / differential — heterophilia + monocytosis suggests bacterial infection; eosinophilia in some parasitic causes
• Uric acid — assess renal status before fluoroquinolone or aminoglycoside dosing
• Glucose — hypoglycaemia in severe debilitation
• AST / bile acids — chronic infection may have hepatic compromise

In a debilitated tortoise, the bloodwork also screens for the comorbidities that change anesthesia tolerance for biopsy/lavage.

Diagnostic samples

This is where management diverges. The two highest-yield tests:

PCR panel for chelonian URTD pathogens: nasal flush, choanal swab, or conjunctival swab. Most reference laboratories offer combined panels covering M. agassizii, M. testudineum, herpesvirus, ranavirus, and sometimes picornavirus. The test is the standard of care for any tortoise with chronic or recrudescent URTD. It changes management — herpesvirus management is supportive only, ranavirus has reportable-disease implications, mycoplasma gets specific antibiotic targeting.

Bacterial culture + sensitivity of nasal flush. Pasteurella testudinis and various Gram-negatives are common secondary or co-pathogens. Culture sometimes returns Pseudomonas or other resistant organisms that change drug choice.

Cytology of nasal flush or oral plaque: cheap, fast, sometimes diagnostic (intranuclear inclusions in herpesvirus, intracytoplasmic vacuoles in some other agents). Usually adjunct to PCR.

Biopsy of oral plaques (under sedation): histopathology of plaques separates herpesvirus (intranuclear inclusions, ballooning degeneration) from vitamin A deficiency (squamous metaplasia, hyperkeratosis) from chronic mycoplasma (lymphoplasmacytic infiltrate). This is the gold-standard differentiation in advanced cases.

Imaging

• Plain radiographs (DV, lateral, craniocaudal) — useful for lower respiratory involvement (pulmonary infiltrates) and for rule-out of foreign body. Routine in any patient with deep cough or open-mouth breathing.
• CT — high-yield for nasal cavity disease; available in larger referral centres. Identifies bony erosion in chronic Mycoplasma cases.
• Endoscopy of the choanae and trachea — high-yield in the symptomatic patient where flush samples are non-diagnostic; allows directed biopsy.

Treatment — by pathogen

Mycoplasma agassizii or M. testudineum positive

Enrofloxacin: 5–10 mg/kg PO or SC q24h × 4–6 weeks. The first-line drug. SC route preferred over IM (IM is irritating in chelonians). Long courses are necessary — Mycoplasma in chelonians is recrudescent rather than curable, and short courses produce relapse.

Doxycycline: 5 mg/kg PO q24h. Alternative or adjunct, particularly in patients where fluoroquinolone toxicity is a concern. Can be used long-term in chronic cases.

Marbofloxacin: 2 mg/kg PO q24h. Alternative fluoroquinolone with better gram-negative spectrum if culture also returns Pasteurella.

Tylosin: 5 mg/kg SC q24h × 4–6 weeks. Older protocol; still used in some referral practices. Macrolide spectrum.

Local treatment: nasal flush with sterile saline twice daily, for 7–14 days at start of therapy. Reduces bacterial burden and improves the patient's comfort. Most chelonian patients tolerate this well after the first or second flush.

The patient is typically not "cured" — they're treated to clinical resolution, then monitored. Recrudescence with stress, husbandry decline, or co-infection is common. The owner should expect a chronic management framework, not a one-shot cure.

Herpesvirus positive

There is no specific antiviral approved or well-characterised in chelonians. Management is supportive:

Acyclovir at 80 mg/kg PO q24h has been described, with mixed evidence. Some sources recommend it; its in-vivo activity in chelonians is unclear. Reasonable to trial in severe cases.

Supportive care:

• Warm, hydrated, optimal POTZ environment
• Force-feeding via syringe or E-tube (see Reptile Force-Feeding)
• Local oral care for diphtheritic plaques — chlorhexidine gel applied 1–2× daily
• Pain control: meloxicam 0.2 mg/kg PO q24h
• Vitamin and supportive injections

The patient is usually a chronic carrier even after clinical recovery — they should not be added to a multi-tortoise group.

Ranavirus positive

No specific antiviral. Reportable disease in some jurisdictions — check local rules. Supportive care similar to herpesvirus management. Strict isolation; the virus is highly contagious in chelonian groups.

Vitamin A deficiency presentation

If the workup points to husbandry-driven URTD with squamous metaplasia rather than infection:

Vitamin A: 1000–2000 IU/kg IM weekly × 4 weeks, OR oral cod-liver-oil supplementation. The IM route is faster, but iatrogenic hypervitaminosis A causes epidermal sloughing, dry/flaky skin, and dysecdysis if overdosed; use the lower end and the shorter course where possible, and prefer dietary or oral correction when feasible.

Diet correction: dark leafy greens, squash, moderate carrot. Long-term — vitamin A deficiency reflects months of dietary inadequacy.

Mixed infections

Most chronic URTD cases have mixed flora. Empirical treatment in absence of culture: enrofloxacin + doxycycline for 4–6 weeks, with nasal flushing at start. Repeat PCR at the end of therapy to confirm reduction in pathogen load.

Supportive care for any URTD patient

Hydration: SC fluids 15–25 mL/kg warm Hartmann's daily for the first week if patient is dehydrated. Daily soaks (20–30 minutes warm water) are owner-friendly and effective for ongoing maintenance.

Temperature: confirm POTZ is being achieved. A patient with confirmed mycoplasma but inadequate basking won't respond to antibiotics until the husbandry is fixed.

Force-feeding when appropriate (see force-feeding article). Don't initiate in the hypothermic or dehydrated patient — fix those first.

Analgesia: meloxicam 0.2 mg/kg PO q24h for any patient with conjunctivitis, oral plaques, or evidence of significant inflammation. Continued for the duration of clinical signs.

Eye care: ocular lubricant (artificial tears) 2–4× daily for affected eyes. Antibiotic eye drops (e.g., ofloxacin 0.3% q8h) for confirmed bacterial conjunctivitis.

Quarantine and biosecurity

URTD pathogens transmit between tortoises. The standard quarantine for a tortoise with confirmed or suspected URTD:

• Strict isolation from other chelonians for the duration of treatment + 6 months
• Separate substrate, food/water bowls, equipment
• Hand-washing and equipment disinfection (chlorhexidine) between handling
• PCR retest at end of treatment and at 6 months to confirm clinical clearance (with the caveat that mycoplasma can remain detectable at low levels long-term)
• New additions to a tortoise group should be quarantined and PCR-tested before introduction

This is the conversation owners often resist; have it early. The cost of breaching quarantine in a 4-tortoise collection is 4 sick patients.

Quick reference

For per-drug data and dose-by-weight, browse the tortoise formulary or run a calculation.

Sources

• Mader DR, Divers SJ, eds. Mader's Reptile and Amphibian Medicine and Surgery, 3rd ed. Elsevier, 2018.
• McArthur S, Wilkinson R, Meyer J, eds. Medicine and Surgery of Tortoises and Turtles. Blackwell, 2004.
• Brown DR, Schumacher IM, McLaughlin GS, et al. Application of diagnostic tests for mycoplasmal infections of desert and gopher tortoises. Chelonian Conservation Biology. 2002;4(2):497–507.
• Marschang RE. Viruses infecting reptiles. Viruses. 2011;3(11):2087–126.
• Jacobson ER, Schumacher J, Telford SR. Pathogenesis and clinical signs of upper respiratory tract disease in tortoises. Vet Clin North Am Exot Anim Pract. 2014;17(3):395–419.
• Carpenter JW, Marion CJ, eds. Carpenter's Exotic Animal Formulary, 6th ed. Elsevier, 2023.
• Plumb DC. Plumb's Veterinary Drug Handbook, 10th ed. Wiley, 2024.