A 26-year-old male trumpeter hornbill (Bycanistes buccinator) presented with acute onset ataxia and incoordination. The animal had undergone a sinusotomy for excisional biopsy of a casque mass two months prior to presentation, which was determined to be non-neoplastic in origin. An abbreviated initial physical examination under manual restraint with supplemental oxygen therapy was performed. The animal was alert, responsive, and had adequate body condition. A rectangular patch approximately 1 cm by 2 cm composed of casque tissue, composite, and moldable epoxy was covering the prior sinusotomy site at the right dorsolateral casque. A composite cap was present over the rostral casque where a defect and deteriorating keratin had been identified and treated previously (Figure 1(a) and 1(b)). Large amounts of putrid dietary material, comprised mostly of fruit, were caked on the bill, casque, and packed along the rostral gnathotheca. Accumulation of dietary material at the oral cavity and casque had been noted at several previous examinations and this material was partially removed during the evaluation. Complete blood count and plasma biochemistry panels were performed. All results were within the International Species Information System reference values for trumpeter hornbills and were considered unremarkable (Teare 2013), although all heterophils exhibited cytologic toxic characteristics. Direct and sodium nitrate fecal floatation analyses performed two weeks prior to presentation revealed no evidence of parasites. A West Nile virus serum neutralization titer assessed two months prior to presentation was 1:40, consistent with the bird's history of previous vaccination. The animal was treated with crystalline fluids (25 mL/kg BW), enrofloxacin (12.5 mg/kg BW), and meloxicam (0.6 mg/kg BW) subcutaneously. Enrofloxacin was continued orally at the same dose for 10 days.

Casque infection, resolution, and subsequent repneumatization in a trumpeter hornbill (Bycanistes buccinator)

All authors

Jenessa L. Gjeltema, Ryan S. De Voe, Brianne E. Phillips & Michael K. Stoskopf

https://doi.org/10.1080/01652176.2015.1035462

Published online:

24 April 2015

Figure 1. Sequential radiographs of the head and casque of a trumpeter hornbill (Bycanistes buccinator) demonstrating a casque mass, casque infection, granulation of the casque space, and repneumatization of the casque space. (a and b) Two months prior to presentation; irregularly shaped mass visible within the casque space. (c and d) Day 3; diffuse increased soft tissue radiopacity of the casque space representing a severe casque infection with complete filling of the casque space by purulent material. (e and f) Day 32; increased soft tissue radiopacity of the rostral two thirds of the casque corresponding to filling of the casque space with granulation tissue. (g and h) Day 64; increased regional radiolucency within the casque space representing progressive repneumatization of the casque space.

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The animal was re-evaluated three days after initial presentation for a neurologic examination and under general anesthesia for a thorough physical examination and further diagnostics. Menace response, pupillary light reflexes, palpebral reflexes, eye position and movement, tongue position, beak tone, withdrawal reflexes, and postural reactions were assessed in the awake animal as was safe and feasible using techniques described for avian species (Clippinger et al. 2007). These were considered normal. The bird was anesthetized, inducing with isoflurane gas and oxygen via facemask followed by intubation and routine maintenance. Orthogonal view radiographs of the head and casque were performed (lateral view 44 kV and 1.6 mAs; dorsoventral view 50 kV and 1.6 mAs), which revealed diffuse increased soft tissue opacity throughout the rostral two-thirds of the casque space (Figure 1(c) and 1(d)). No important radiographic abnormalities were seen in orthogonal views of the whole body. In addition to orthogonal view radiographs, oblique and rostrocaudal views may also be of particular value for diagnosis, monitoring, planning of a specific treatment approach, and in assessing response to treatment of casque disease. Advanced imaging for this case was not pursued due to limitations of cost and availability, although computed tomography and magnetic resonance imaging would likely have provided additional helpful information about the internal casque structure and composition. Removal of the composite patch at the sinusotomy site located at the right dorsolateral casque and the rostral cap revealed a casque space completely filled with purulent material (Figure 2(a)). Samples were collected for cytology and submitted for bacterial cultures. The casque space was lavaged extensively with sterile saline solution through the sinusotomy window and then packed with sterile umbilical tape soaked in sterile saline and silver sulfadiazine cream. The sinusotomy window was then covered by an adhesive elastic bandage. The cytology revealed suppurative inflammation with intracellular bacteria. Bacterial culture produced heavy growth of Enterobacter aerogenes, which was intermediately resistant to enrofloxacin and sensitive to ciprofloxacin, a common metabolite of enrofloxacin reported in pharmacokinetic studies of some avian species (Flammer et al. 1991). There was also light growth of Citrobacter freundii, which sensitivity testing indicated was susceptible to both enrofloxacin and ciprofloxacin. These results were considered biased due to the previously initiated empirical treatment with enrofloxacin. Complete blood counts performed on days 10 and 14 following the presentation revealed marked heteropenia (0.54 and 0.17 × 10⁹ cells/L, respectively; reference values 0.00–7.55) with characteristic toxicity indicative of a marked inflammatory response.

Casque infection, resolution, and subsequent repneumatization in a trumpeter hornbill (Bycanistes buccinator)

All authors

Jenessa L. Gjeltema, Ryan S. De Voe, Brianne E. Phillips & Michael K. Stoskopf

https://doi.org/10.1080/01652176.2015.1035462

Published online:

24 April 2015

Figure 2. Sinusotomy site at the right dorsolateral aspect of the casque. (a) Day 3; sinusotomy site at diagnosis of severe casque infection. (b) Day 88; showing remaining shallow defect at sinusotomy site.

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The casque was managed as an open wound, and standard wound care was initiated including extensive lavage with sterile saline solution, debridement, and packing with sterile gauze or umbilical tape into the open casque space cavity under general anesthesia. A lavage port was created by inserting a syringe tip through deteriorating keratin tissue at the rostral casque. This allowed retrograde lavage and complete draining of the casque space. Rigid laparoscopy allowed monitoring of the rostral and caudal poles of the casque space that were not easily visible through the sinusotomy window. Wound care was initially performed every three days for a total of five treatments until a thick layer of healthy granulation tissue had formed over the entire mucosal surface within the casque space. Packing of the casque space was then discontinued to allow the cavity to fill entirely with granulation tissue. In conjunction with wound care, the animal was continued on enrofloxacin and meloxicam orally or subcutaneously once daily as previously prescribed. In addition to these medications, clindamycin (25 mg/kg BW) was also administered orally or subcutaneously twice daily for 14 days, and tramadol (2 mg/kg BW) was given orally twice daily as needed based on behavioral signs of discomfort. Crystalline fluid (10–20 mL/kg BW) was also administered subcutaneously as needed to maintain hydration during the course of treatment. Hydration status was subjectively determined by eyelid skin turgor, mucous membrane moisture, and urine production.

Weekly evaluations and light debridement were performed under general anesthesia for three additional weeks after the first five treatments. Orthogonal view radiographs of the casque were performed at 32, 45, and 63 days post presentation. These radiographs initially showed increased soft tissue radiopacity throughout the majority of the casque space presumed to be due to filling of the space with granulation tissue (Figure 1(e) and 1(f)). Progressive remodeling of the internal structure and repneumatization of the casque space was evident when comparing sequential radiographs (Figure 1(g) and 1(h)). At 400 days after presentation, the animal has exhibited no further clinical signs. The sinusotomy window and rostral lavaging port are visible as shallow defects at the right dorsolateral and rostral casque (Figure 2(b)).

The casque is a unique anatomical feature of the ramphotheca for hornbills in the avian family Bucerotidae. The exact function of the casque remains unclear and likely varies by species, but may provide structural support, be primarily ornamental in nature, or serve an acoustic purpose (Alexander et al. 1994). The anatomical and mechanical properties of casques for several hornbill species have been studied and described in detail. For most species, the casque is a pneumatized structure lined by cancellous bone with an overlying keratinous external surface (Gamble 2007; Seki et al. 2010). The casque space may be continuous with other sinuses associated with the ramphotheca and head, and the connectivity of these sinuses may vary by species. Casque-related diseases such as traumatic injury (Wright 1992) and squamous cell carcinoma in great hornbills (Buceros bicornis) (Miller et al. 1985; Gamble, 2012) have been reported in the literature, but less information is available on the management of casque infections in any hornbill species.

The initial clinical signs observed in this case were ataxia and incoordination, non-specific signs that can be associated with a number of diseases. Hepatic encephalopathy related to iron storage disease (Gamble 2015), atherosclerosis (Miller et al. 1985; Gamble 2015), and West Nile virus (Komar 2003) may cause neurologic signs, and have been reported in hornbills. Additionally, heavy metal toxicity, metabolic disease such as hypoglycemia, verminous or protozoal encephalitis, aspergillosis, and intracranial neoplasia were included in the differential diagnoses for this case and were ruled out or considered unlikely based on history and the diagnostics performed. Due to the rapid resolution of these clinical signs following treatment, the ataxia and incoordination were attributed to the casque infection. The exact pathogenesis is unclear, but the apparent neurologic signs could have been caused by generalized weakness related to a debilitated state, bacterial toxemia related to the infection, or imbalance from altered weight distribution within the casque. Secondary bacterial encephalitis due to hematogenous or direct spread through connected sinuses and the nasal conchae or hypoglycemia from sepsis related to the infection are also possibilities.

A variety of factors may have contributed to the development of the casque infection in this case. The infection may have developed as a sequela to the sinusotomy for excisional biopsy of a casque mass performed two months earlier. Although aseptic technique, lavage of the casque space following the procedure, and perioperative antibiotic therapy were used, bacterial contamination of the casque space may still have occurred during the surgery. This may have led to infection, which then worsened over the course of two months.

Attempting to fully close a casque lesion or surgical window may also lead to complications. An incomplete or ineffective patch over the sinusotomy site can allow bacterial contamination and subsequent infection of the casque space. Epoxy and dental mold material have been used in some cases to create patches or to cover casque defects (Miller et al. 1985; Wright 1992), but such rigid closures can inhibit timely and effective assessment of the healing wound. In this case, the original patch was created using dental composite and the removed section of casque. It is possible that the autogenous casque tissue used in this patch did not have an adequate vascular supply to prevent necrosis following replacement after the sinusotomy procedure. Use of potentially devitalized autogenous tissue is not recommended to avoid some of the complications encountered in this case. This animal also had a prominent indentation at the rostral casque separate from the casqueotomy site, composed of deteriorating keratin, and packed with putrid food. This indention had also been treated previously with cleaning, trimming, and epoxy capping. It is unclear whether this defect or its treatment may have contributed to the development of infection but it is a possibility, particularly if accumulated decaying food exacerbated deterioration of the external casque keratin.

Although caking of food material within or around the oral cavity of a bird may occur as a result of debilitation or beak deformities, recurrent accumulation of food material on the bill, casque, or within the oral cavity of an otherwise healthy bird may indicate inappropriate dietary management or husbandry. The buildup of dietary material on the bill or casque as was noted during the physical examination in this case could contribute to potential deleterious health effects for the animal. Prolonged contact with decaying food material may lead to a loss of integrity to normal keratin layers or facilitate establishment of infection. Some hornbill species utilize ballistic transport of food with a cranio-inertial mechanism rather than lingual manipulation to guide dietary items into the esophagus (Baussart & Bels 2010). Many hornbill species are predominantly frugivorous in the wild and may ingest small whole fruit items such as figs, berries, and drupes (Kemp 1995). Peeled, soft, juicy, or finely chopped fruits may be more prone to adhering to the bill. Alteration of the diet to include items of appropriate size, shape, and consistency for ballistic feeding in animals with recurrent potentially hazardous accumulation of dietary material at the casque or bill is recommended to prevent some of the complications that occurred in this case. These birds may also utilize small twigs or other enrichment items to remove undesirable debris, and providing convenient tools that may be used for self-grooming behavior is appropriate (Galama et al. 2002). Regular inspection and hygiene measures by husbandry staff are also recommended to prevent potentially harmful accumulation of dietary material.

One striking feature of this case is the apparent complete filling of casque space by granulation tissue followed by repneumatization as healing progressed. Casque regeneration has been previously described (Wright 1992), but the obliteration of the casque space by granulation tissue was unexpected and it is unknown if it was an over exuberant healing reaction or if this is common for this type of wound. The healing was also characterized by repneumatization. It is unclear whether all hornbills are capable of repneumatization of the casque, and generalizations about this capability in other hornbill species should be made with caution.

This case report describes the diagnosis, clinical management, and resolution of a severe casque infection in a trumpeter hornbill. Resolution of the infection was achieved by treating the casque with techniques similar to those used for open wounds in other tissues. These included frequent evaluation with rigid laparoscopy of the sinus and the creation of an opening in the rostral casque to facilitate flushing and draining the wound. Management of casque defects using modified open-wound techniques can be an effective treatment option for some cases of casque disease.