Presumed Tetanus in a Temminck's Pangolin (Smutsia temminckii)

Clostridium tetani is distributed worldwide, with highest prevalence in humid regions with mean daily temperatures >20 C (Cataldo 2018). Most infections are due to open-wound contamination with infected soil; deep wounds with anaerobic conditions favor C. tetani growth and toxin production (Popoff 2020). Generalized tetanus occurs when tetanus toxin is internalized to peripheral nerves, inhibiting γ-aminobutyric acid release, causing excessive excitation of neuromuscular cells and the characteristic tetanic contractions (Farrar et al. 2000). There is marked variability in the susceptibility of animal species to tetanus infection, and although it is thought that all species are susceptible, there are no previous reports in pangolins (Popoff 2020).

An adult female Temminck's pangolin (Smutsia temminckii) weighing 10.5 kg (reference range, 2.5–15.8 kg; Pietersen et al. 2019) was seized from the illegal wildlife trade (IWT) in Malawi. The pangolin ambulated normally, with an elevated tail and bipedal gait. An undermined, full-thickness dermal ulcer (2.1×2.8 cm) was present on the right forelimb (RF) palmar surface, exposing superficial flexor tendons. A small circular ulcer (0.3 cm in diameter and 0.5 cm in depth) was present on the RF lateral aspect. Isoflurane (Isofor, Safeline Pharmaceuticals, Johannesburg, South Africa) 2–3% via a facemask was used to facilitate further physical examination and treatment. Aerobic culture from the lesions produced no bacterial growth; anaerobic culture was unavailable. Hematology samples collected during this anesthesia revealed a mild lymphocytopenia (0.5×10⁹/L; reference range, 0.64–4.35; Hooijberg et al. 2021); no other hematologic abnormalities were noted. The ulcer was irrigated with povidone-iodine solution (10% solution, Zylo-P, Leben Laboratories, Akola, India) diluted to 0.3% and then surgically debrided to remove gross contamination and necrotic tissue (Fig. 1). Supplemental nutrition was provided via orogastric tube under anesthesia. The following antibiotics were administered: long-acting amoxicillin (150 mg/mL, Biocillin LA, Interchemie, Venray, the Netherlands) 15 mg/kg subcutaneously (SC) every 48 h and enrofloxacin (100 mg/mL, Baytril, Elanco, Hook, UK) 10 mg/kg SC every 24 h; analgesia was provided using butorphanol (10 mg/mL, Butador, Chanelle Pharma, London, UK) at 0.5 mg/kg SC every 12 h. Fluoroquinolone treatment before culture results becoming available was decided based on initial wound cytology showing Gram-negative bacilli; furthermore, antimicrobial resistance to first-line empirical choices appears common in IWT pangolin wound cultures and the use of fluoroquinolones for deep wounds has been proposed in other pangolin species (Thai et al. 2014).

Profound lethargy was observed 5 d after intake. Previously, the pangolin would forage during the evening for up to 2 h; it was now unable to forage for periods >20 min before falling asleep. Abnormal gait was also observed, with all four limbs and the tail used for ambulation. Repeat hematology and biochemistry samples were taken at this time, and no significant changes were observed. The next day, the pangolin was nonambulatory and had generalized stiffness that prevented it from exhibiting normal tight curl behavior (Fig. 2). Tonic spasms were observed. Differential diagnoses included tetanus, hypocalcemia, meningoencephalitis, and rabies. Presumed C. tetani infection was diagnosed due to the characteristic presentation in the absence of electrolyte abnormalities; therefore, medical treatment was initiated.

Rectal diazepam (10 mg, Diazepam Rec-Tubes, Wockhardt, Wrexham, UK) at 1 mg/kg was administered to control muscle spasms, with negligible effect. Midazolam (5 mg/mL, Midazolam, Hameln Pharma Ltd., Gloucester, UK) at 0.5 mg/kg intramuscularly every 8 h reduced rigidity and spasms. Butorphanol was administered at 0.5 mg/kg SC every 6 h for mild sedation and analgesia. Metronidazole (500 mg/100 mL, Metronidazole Kabi, Fresenius Kabi, Midrand, South Africa) was initiated at 8.75 mg/kg intravenously (IV) every 12 h; enrofloxacin was discontinued. Supportive care of IV fluid therapy with lactated Ringer solution (lactated Ringer injection, Fresenius Kabi), at 10 mL/kg every 12 h, and supplemental nutrition were provided. All drug dosages were calculated with a 25% reduction to account for scale weight because the metabolic demand of these scales is unknown (Pietersen et al. 2019). The RF wounds were irrigated daily with 1% povidone-iodine solution. The pangolin was housed in a quiet, dark environment with additional heat sources and was repositioned four times daily.

After 24 h of intensive care (6 d after intake), trismus and hypersalivation developed; by 8 d after intake, urine retention was evident; therefore, a urinary catheter was placed. Supportive care and therapeutics were continued, and euthanasia was considered because of lack of response to treatment, but 10 d after intake, before the necessary permissions were obtained, the pangolin died. Necropsy was conducted immediately. Severe pulmonary edema, frothy serosanguinous nasal discharge, and gastric ulceration at the peptic gland were found. Aerobic cultures from the deeper wound, stomach, and lung samples produced no bacterial growth.

Presumed or confirmed C. tetani infection has not previously been reported in any animal of the order Pholidota. Tetanus diagnosis is often made clinically (Stalder 2019). Although laboratory testing may support a clinical diagnosis, serum toxin, serum tetanus toxin antibody, and C. tetani PCR or aerobic cultures may not be easily accessible in resource-poor countries, as in this instance. Furthermore, C. tetani is rarely detected through culture, PCR, or tetanus toxin antibody testing (Afshar et al. 2011).

The efficacy of tetanus antitoxin in many species is disputed, and due to the unknown risk of hypersensitivity reactions, it was not administered in this case (Armentano and Schaer 2014). However, because the prognosis is grave regardless, administration may be warranted in future pangolin tetanus cases. Although nonsteroidal anti-inflammatory drugs have been used as analgesia for tetanus in other veterinary species, they were withheld due to the high risk of gastric ulceration in pangolins (Ives 2014; Bentley et al. 2021). There are no pharmacodynamic studies assessing analgesics in pangolins; full opioid agonists were unavailable; therefore, butorphanol was used for its partial opiate analgesia and mild sedative effects (Ives 2014; Wicker et al. 2019). Pain from muscle spasms and rigidity was further minimized through benzodiazepine administration.

Tetanus is preventable; therefore, immunization is recommended for susceptible species (Stalder 2019). Since this case, vaccination with a single dose of 0.5 mL of tetanus toxoid (Tetanus Toxoid Vaccine Absorbed, Serum Institute of India, Pune, India) has been administered to eight pangolins presenting with deep tissue wounds, with no noted adverse reactions. Additional studies are required to assess whether this tetanus vaccination protocol in Temminck's pangolin produces a sufficient antibody response and to evaluate the duration of protection. It is probable that other pangolin species are also susceptible; therefore, vaccination may be indicated in individuals with tetanus-prone wounds on presentation.