Hind Limb Edema in Four White’s Tree Frogs (Dryopsophus caeruleus) A Clinical Case Involving Bacterial Culture and Therapeutic Adjustment

Summary

In January 2025, four White's tree frogs housed in a controlled environment simultaneously developed swelling localized in their hind limbs. An examination conducted by the team of biologists at the sanctuary revealed an accumulation of lymphatic fluid in the thighs. Initially, two possibilities were considered: a fungal or bacterial infection. The case presents clinical interest as it marks a first at Éducazoo and shows varying responses to infection among the four individuals, from treatment success to persistent infection in one of them. This article outlines the different stages of management, the microbiological analysis, and the treatment adjustment for one of the frogs.

---

Case Presentation

Symptoms and Initial Observations

Four White’s tree frogs (Dryopsophus caeruleus), housed in three different enclosures (one pair and two individuals housed alone), were observed with edema in both hind limbs. The animals remained active and were feeding well, but a significant swelling was visible and appeared to progress rapidly. The fluid accumulation suggested a disruption in lymphatic drainage, possibly of infectious origin.

---

The Role of the Lymphatic System

The lymphatic system plays a crucial role in maintaining proper bodily function. It helps regulate fluid balance, supports immune defense, and aids in the elimination of cellular waste. It works in parallel with the circulatory (blood) system. In amphibians, this system is particularly important as it regulates tissue pressure and helps combat skin infections. Their thin and delicate skin makes them more susceptible to such infections, especially given their preference for humid environments—conditions that are ideal for the growth of infectious microorganisms.

---

Isolation and Preventive Measures

As soon as symptoms appeared, each frog was placed in individual isolation in our quarantine room. This decision aimed to reduce the risk of inter-individual transmission and prevent potential spread of microorganisms to healthy amphibians. Although the exact nature of the infectious agent affecting the frogs could not be determined at this stage, all necessary precautions were taken to contain the infection to these four individuals.

---

Veterinary Consultation and Initial Treatment

A veterinary consultation took place on January 23, 2025. Based on the symptoms and the absence of severe systemic signs, the veterinarian prescribed a broad-spectrum antibiotic known to be effective against a wide range of microorganisms. Treatment with Baytril (enrofloxacin) was initiated topically, meaning it was applied directly to the skin between the shoulder blades. After application, the amphibians were kept in empty holding enclosures for at least one hour to allow proper absorption of the medication. Daily health monitoring was conducted and recorded in each individual’s care log.

The protocol recommended by the veterinarian called for prolonged treatment as long as clinical improvement was observed.

---

Clinical Progression: Resolution in Three Individuals

Over the following weeks, all four frogs showed noticeable improvement, with a steady reduction in lymphatic fluid in the hind limbs until full resolution. Treatment was continued until no signs of infection were present for several consecutive days. In the absence of relapse or recurrence, treatment was discontinued on March 4, 2025, for all four individuals. To this day, no return of symptoms has been observed in three of the frogs, whose condition remains stable.

---

Relapse and Further Investigations

In one of the frogs, symptoms reappeared on May 2, approximately two months after treatment was stopped. In this case, Baytril alone had not been sufficient to eliminate all microorganisms. A follow-up veterinary visit was arranged. On May 8, a sample of lymphatic fluid was aspirated directly from the site of the edema and sent to the lab for precise identification of the pathogens responsible for the infection.

---

Culture Results and Treatment Adjustment

Bacterial culture revealed the presence of three opportunistic pathogens:

• Citrobacter freundii

• Acinetobacter sp.

• Myroides sp.

Some of these microorganisms are known for their resistance to standard antibiotics—particularly Baytril.

Based on the results, the treatment was adjusted to ensure greater efficacy by selecting an antibiotic specifically targeting the identified bacteria: trimethoprim-sulfamethoxazole (TMS), recognized for its effectiveness against several Enterobacteriaceae and Gram-negative bacilli.

---

Current Status and Prognosis

The affected frog remains under treatment with TMS. Partial reduction of the swelling has been observed, and the frog’s condition continues to be monitored daily. Its behavior remains normal, it is feeding well, and no systemic symptoms have developed. The short-term prognosis is guarded, but we remain hopeful that this new antibiotic will succeed in eradicating the three pathogens.

---

Conclusion

This case highlights the importance of:

• Rigorous monitoring of animals housed in groups;

• Early isolation when unexplained symptoms appear;

• And most importantly, the value of bacterial culture in diagnosing infectious diseases when initial treatment proves ineffective.

---

Acknowledgments

We thank the attending veterinarian for their availability and expertise, and we extend our gratitude to the animal care team for their diligent daily monitoring, which contributed to the swift recovery of most of the affected individuals.