Diagnosis and outcome of odontogenic abscesses in client-owned rabbits (Oryctolagus cuniculus): 72 cases (2011–2022)

Ivana Levy Department of Surgical Science, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI

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Christoph Mans Department of Surgical Science, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI

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Abstract

OBJECTIVE

To characterize the epidemiologic features of rabbits with odontogenic abscesses.

ANIMALS

72 client-owned rabbits.

METHODS

The medical record database of a veterinary teaching hospital was searched to identify rabbits with odontogenic abscesses characterized by a palpable facial mass and confirmed via CT scan. Data reviewed included age, breed, presenting complaint, abscess location, bacterial culture results, treatment, and outcome.

RESULTS

Lop-eared rabbits were the most common breeds affected (20/72 [28%]), and mini lop rabbits were significantly overrepresented. The mandibular quadrants were more frequently affected (65/92 [71%]), and osteomyelitis was a common comorbidity on CT (53/72 [74%]). The most common aerobic and anaerobic isolates were Streptococcus spp (17/40 [43%]) and Fusobacterium spp (10/22 [45%]), respectively. Systemic antibiotic therapy alone was performed in 35 of 62 (56%) treated cases, with documented resolution in 25%. Abscess packing with antibiotic-soaked gauze in conjunction with systemic antibiotic therapy was performed in 20 of 62 (32%) treated cases. Resolution of the odontogenic abscesses with this treatment protocol was documented in 17 of 20 (85%) cases. The number of packing procedures used to obtain resolution of infection was 4 (IQR, 3 to 5).

CLINICAL RELEVANCE

A combination of the abscess-packing technique, which avoids extensive surgery and extraction of the involved elodont teeth, with systemic antibiotic therapy can be an effective treatment option for rabbits with palpable odontogenic abscesses and can result in a high cure rate comparable to more invasive surgical treatments. Antibiotic treatment alone is not recommended, as it has a low chance of abscess resolution.

Abstract

OBJECTIVE

To characterize the epidemiologic features of rabbits with odontogenic abscesses.

ANIMALS

72 client-owned rabbits.

METHODS

The medical record database of a veterinary teaching hospital was searched to identify rabbits with odontogenic abscesses characterized by a palpable facial mass and confirmed via CT scan. Data reviewed included age, breed, presenting complaint, abscess location, bacterial culture results, treatment, and outcome.

RESULTS

Lop-eared rabbits were the most common breeds affected (20/72 [28%]), and mini lop rabbits were significantly overrepresented. The mandibular quadrants were more frequently affected (65/92 [71%]), and osteomyelitis was a common comorbidity on CT (53/72 [74%]). The most common aerobic and anaerobic isolates were Streptococcus spp (17/40 [43%]) and Fusobacterium spp (10/22 [45%]), respectively. Systemic antibiotic therapy alone was performed in 35 of 62 (56%) treated cases, with documented resolution in 25%. Abscess packing with antibiotic-soaked gauze in conjunction with systemic antibiotic therapy was performed in 20 of 62 (32%) treated cases. Resolution of the odontogenic abscesses with this treatment protocol was documented in 17 of 20 (85%) cases. The number of packing procedures used to obtain resolution of infection was 4 (IQR, 3 to 5).

CLINICAL RELEVANCE

A combination of the abscess-packing technique, which avoids extensive surgery and extraction of the involved elodont teeth, with systemic antibiotic therapy can be an effective treatment option for rabbits with palpable odontogenic abscesses and can result in a high cure rate comparable to more invasive surgical treatments. Antibiotic treatment alone is not recommended, as it has a low chance of abscess resolution.

Introduction

Rabbits are common companion mammals that present to veterinary clinics with acquired or, less frequently, congenital dental disease.14 Acquired dental disease is often caused by a combination of factors including inappropriate diet, trauma, metabolic bone disease, infection, or, less likely, neoplasia.2,5,6 These abnormalities can lead to physical changes including elongated teeth, malocclusion, and the progressive development of dental spurs.2,7 A known complication of dental disease is the formation of odontogenic abscesses and secondary osteomyelitis.8,9 While odontogenic abscesses are common in rabbits, the pathophysiology is not currently well understood.1012

Although dental disease and odontogenic abscesses are commonly diagnosed in companion rabbits, there is currently limited evidence-based information on the manifestation, diagnosis, treatment, and outcome of this condition in rabbits. Documented clinical signs of odontogenic abscess formation include hyporexia to anorexia, palpable facial swellings, epiphora, ptyalism, and weight loss.1,3,10,11 Intraoral exam findings may include clinical crown abnormalities such as abnormal occlusal surfaces, clinical crown elongation leading to secondary soft tissue trauma, mobile or fractured teeth, widened interproximal space, or purulent material in the oral cavity.1,3,10,11 Generally, it is recommended to perform advanced diagnostic imaging, including a CT scan and oral endoscopy under anesthesia, to comprehensively evaluate the dentition and odontogenic infection.11,13

There is no current consensus on the most appropriate treatment protocol for odontogenic abscesses in rabbits.3,6,8 Most authors agree that treatment decisions are dependent on the severity of the disease, and the current recommendation for treating odontogenic abscesses is a combination of surgical and medical management.3,10 Surgical techniques described include intraoral or extraoral tooth extraction, abscess excision with or without marsupialization, an abscess-packing technique using antibiotic-soaked gauze, or the use of various topical treatments.3,4,6,8,10,14,15 Currently, reports on the effectiveness of treatment protocols for odontogenic abscesses in rabbits are limited to 3 retrospective studies that involve abscess packing, aggressive surgical debridement, and tooth extraction.6,8,14 In cases treated with the abscess-packing technique using antibiotic-soaked gauze combined with systemic antibiotics and avoiding extraction of involved teeth, the reported resolution rate was 93% (13/14; disease-free time, 32.6 ± 24.3 months).8 Another study6 that investigated aggressive surgical treatment including tooth extraction and marsupialization demonstrated resolution in 90% (182/203) of cases (disease-free time, 29 months; range, 4 to 60 months). Another study14 assessed tooth extraction alone, and 90% (18/20; disease-free time not provided) of cases were resolved. For other treatment options, the information published is anecdotal and included in textbooks and review articles.24,10

The purpose of this retrospective study was to describe the clinical signs, diagnosis, treatment, and outcome of rabbits diagnosed with odontogenic abscesses at a single veterinary teaching hospital over an 11-year period.

Methods

Medical records of patients seen at the University of Wisconsin-Madison School of Veterinary Medicine (UW-SVM) were reviewed by a single author (IL) using an electronic medical record system (VetStar; Advanced Technology Corp). All rabbits that presented to the veterinary hospital between January 1, 2011, and July 31, 2022, and that had the term “abscess” in their medical record were reviewed. Cases were eligible for inclusion only if the patient had a palpable facial mass and the CT scan was reviewed by a board-certified radiologist whose findings and interpretation were consistent with an odontogenic abscess. Cases were excluded if they were consistent with a retrobulbar abscess due to different treatment recommendations and outcomes for this condition at this institution.16

Data extracted from the medical record included age at diagnosis, sex, presenting complaint and physical exam findings, abscess location (oral quadrant affected), presence of concurrent dental disease, relevant CT findings, aerobic and/or anaerobic culture results, prior antibiotic treatments, treatments performed, and outcome. Disease resolution was defined as the clinical resolution of the odontogenic abscess. Disease-free time was defined as the available follow-up time postresolution of an odontogenic abscess with no known recurrence. Efforts were made to obtain follow-up information from the client and referring veterinarian through email and phone.

Data were evaluated using Excel (Microsoft Corp). Descriptive statistics are reported as median and range unless otherwise indicated. χ2 tests or Fisher exact tests were used to evaluate for differences in disease prevalence and outcomes among breeds, sex, and different diagnostic and treatment factors. Differences were considered statistically significant if P < .05.

Results

Signalment

A total of 1,886 rabbits were presented to the teaching hospital between the period of January 1, 2011, and July 31, 2022. Of those rabbits, 72 (3.8%) had a palpable facial mass and were diagnosed with 1 or multiple odontogenic abscesses via CT. Age ranged from 6 to 134 months (median, 54 months), and body weight ranged from 0.8 to 4.6 kg (median, 1.9 kg). Male rabbits accounted for 62% (45/72) of cases (56% of the total rabbit population were male), and 38% (27/72) were female (43% of all evaluated rabbits were female; Supplementary Table S1). Male rabbits were not significantly more likely to be diagnosed with odontogenic abscesses (P = .29). Lop-eared rabbit breeds were the most prevalent group of breeds diagnosed with odontogenic abscesses (20/72 [28%]) and significantly more likely to be diagnosed with odontogenic abscesses (P = .035; 18% of all evaluated rabbits were lop-eared breeds). The mini lop breed was most prevalent (13/72 [18%]; 8% of all evaluated rabbits were mini lops) and significantly more likely to be diagnosed with odontogenic abscesses than other breeds (P = .0025). Other rabbit breeds commonly diagnosed with odontogenic abscesses included rex or mini rex (11/72 [15%]; 11% of all evaluated rabbits belonged to these breeds; P = .26) and Dutch (8/72 [11%]; 11% of all evaluated rabbits belonged to this breed). Breed prevalence is summarized in Supplementary Table S2.

Presenting complaints and clinical signs associated with palpable odontogenic abscesses included hyporexia/anorexia (26/72 [36%]), ocular discharge (13/72 [18%]), lethargy (8/72 [11%]), upper respiratory signs (6/72 [8%]), or ptyalism (4/72 [6%]; Supplementary Table S1).

Diagnosis

On the basis of a palpable facial mass and confirmed via CT, 72 cases were diagnosed with at least 1 odontogenic abscess. A single rabbit had 2 unrelated odontogenic abscesses at different time points and was therefore included as 2 separate cases. Of these cases, 58 of 73 (79%) had a single oral quadrant affected, 13 of 73 (18%) had 2 quadrants affected, and 2 of 73 (3%) had all 4 quadrants affected (Table 1; Supplementary Tables S3 and S4). Based on the involvement of > 1 quadrant at the time of diagnosis, there was a total of 92 odontogenic abscesses, with 65 of 92 (71%) affecting the mandibular quadrants and 27 of 92 (29%) affecting the maxillary quadrants.

Table 1

Abscess location, culture results, treatment, and outcome for 19 rabbits receiving abscess packings for 20 odontogenic abscesses at a veterinary teaching hospital from 2011 to 2022.

Case affected Quadrant Aerobic culture Anaerobic culture Packing material: No. of packings Systemic antibiotics (d) Resolved? Y/N DFT (d)
16 Mand NG Fusobacterium nucleatum Ampicillin: 4 ENO: 56

MTR: 56
Y 55
32 Mand Streptococcus milleri NS Ampicillin: 3 SXT: 44

MTR: 44
Y 180
18* Max Pseudomonas aeruginosa Fusobacterium spp Bacteroides pyogenes Ampicillin: 6 AZM: 56 Y 210
50** Max Staphylococcus pseudintermedius

Mannheimia granulomatis Streptococcus suis
NG Ampicillin: 2 AZM: 28

ENO: 28
Y 240
45 Mand NG B pyogenes Ampicillin: 3 AZM: 14

CCFA: 36
Y 251
47 Mand Proteus mirabilis Enterobacter cloacae

Streptococcus spp
NG Ampicillin: 1

Ceftazidime: 3
AZM1: 36

ENO1: 36
Y 335
66 Mand NG NS Pen-G: 6 ENO: 51

MTR: 51
Y 354
38 Mand Streptococcus intermedius NG Ceftazidime: 5 AZM: 64 Y 375
2 Mand NG Fusobacterium canifelinum Ampicillin: 2 CCFA: 56

AZM: 30
Y 390
10 Mand S intermedius NG Ampicillin: 2 AZM: 30

SXT: 30
Y 399
35* Mand NG NG Pen-G: 7 SXT: 56

AZM: 20
Y 675
7* Max S intermedius NS Cefazolin: 4 AZM: 42 Y 713
3 Mand NG F nucleatum Ampicillin: 2

Ceftazidime: 3
PPG: 30

MTR: 51
Y 730
27* Mand NG NG Ampicillin: 4 AZM: 42 Y 861
12 Max NG NS Ceftazidime: 3 AZM: 30 Y 1,096
71 Mand S intermedius NG Ampicillin: 3 CCFA1: 51

MTR: 51
Y NFU
33 Mand S intermedius NG Ampicillin: 5 ENO: 42

AZM: 42
Y NFU
13 Mand NG NS Ceftazidime: 1 AZM: 30 N2 N/A
42 Max Escherichia coli Pasteurella multocida

Enterococcus gallinarum
B pyogenes Ampicillin: 5 CHL: 19

MTR: 38

ENO: 57

CCFA: 16
N3 N/A
50** Mand NG B pyogenes

Fusobacterium spp
Ampicillin: 2 AZM: 14 N4 N/A

Abscesses were packed in a median of 7-day intervals with a range of 6 to 8 days. Patients received a range of 2 to 7 packings, with a median of 4 packings.

AZM = Azithromycin. CCFA = Ceftiofur crystalline-free acid. CHL = Chloramphenicol. DFT = Disease-free time (defined as available follow-up time after resolution of facial mass with no known recurrence). ENO = Enrofloxacin. Mand = Mandibular. Max = Maxillary. Med = Median. Min = Minimum. MTR = Metronidazole. NFU = No follow-up. NG = No growth. NS = Not submitted. Pen-G = Penicillin G. SXT = Trimethoprim/sulfamethoxazole.

Some or all abscess packings performed at referring veterinarian.

Patient received 2 separate abscess packings for unrelated odontogenic abscesses.

Changed to this antibiotic on the basis of initial culture results.

Patient died under anesthesia 7 days post–initial abscess packing.

Patient euthanized 57 days post–initial abscess packing due to progressive disease.

Patient had abscess packing discontinued after 14 days due to cardiac arrest during anesthesia and elected for palliative care.

Computed tomography demonstrated that most rabbits (62/73 [85%]) had concurrent dental disease in either the same or a different oral quadrant consisting of malocclusion, crown elongation, dental spurs, periodontal disease, and/or tooth displacement/rotation. Other CT findings included osteomyelitis (53/73 [73%]) associated with the odontogenic abscess, otitis externa (20/73 [27%]), head and/or cervical lymphadenopathy (19/73 [26%]), rhinitis or sinusitis (15/73 [21%]), otitis media (12/73 [16%]), and/or mandibular fracture (4/73 [5%]). Of the rabbits with a known breed with otitis media, 6 of 10 (60%) were lop-eared rabbits.

Bacterial cultures

Bacterial cultures (aerobic, anaerobic, or both) were performed in 44 of 73 (60%) cases (Tables 13; Supplementary Tables S3–S5). Samples were collected by extraoral fine-needle aspiration of the abscesses or intraorally through the sampling of the purulent discharge during endoscopy-guided intraoral examination under general anesthesia. Of the 44 cases that had bacterial cultures performed, 24 of 44 (55%) were receiving antibiotics at the time of the sample collection. Aerobic and anaerobic cultures were performed in 29 of 44 (66%) cases and solely aerobic cultures in 15 of 44 (34%) cases. No growth on aerobic culture was reported in 17 of 44 (39%) cases, with 11 of 17 (65%) cases receiving systemic antibiotics at the time of sampling. No growth on anaerobic culture was reported in 13 of 29 (45%) cases, with 3 of 13 (23%) having received antibiotics effective against anaerobes before sample collection.

Table 2

Aerobic bacterial isolates (n = 40) from 43 rabbits with 44 odontogenic abscesses. Twenty-six of 40 (65%) isolates were gram-positive and 14 of 40 (35%) were gram-negative.

Isolate name No. (%) of isolates
Streptococcus spp 17/40 (43%)
 Streptococcus intermedius (9)
Pasteurella spp 6/40 (15%)
 Pasteurella multocida (5)
Staphylococcus spp 5/40 (13%)
Escherichia coli 2/40 (5%)
Gemella morbillorum 2/40 (5%)
Pseudomonas aeruginosa 2/40 (5%)
Actinobacillus capsulatus 1/40 (2%)
Nonhemolytic Corynebacterium 1/40 (2%)
Enterobacter cloacae 1/40 (2%)
Enterococcus gallinarum 1/40 (2%)
Neisseria spp 1/40 (2%)
Proteus mirabilis 1/40 (2%)
Table 3

Anaerobic isolates (n = 22) from 16 rabbits with odontogenic abscesses.

Isolate name No. (%) of isolates
Fusobacterium spp 10/22 (45%)
 Fusobacterium nucleatum (5)
Bacteroides spp 7/22 (32%)
 Bacteroides pyogenes (4)
 Bacteroides fragilis (3)
Parvimonas micra 3/22 (14%)
Rodentibacter pneumotropicus 1/22 (4%)
Veillonela parvula 1/22 (4%)

A total of 62 isolates (40 aerobic, 22 anaerobic) were isolated from 44 positive cultures (Tables 13; Supplementary Tables S3 and S4). Of the aerobic bacteria, 26 of 40 (65%) isolates were gram-positive while 14 of 40 (35%) isolates were gram-negative. Eleven of 27 (41%) aerobic cultures grew gram-negative isolates either alone or in conjunction with other isolates. The most frequently isolated aerobic bacteria were Streptococcus intermedius (9/40 [23%]), α-hemolytic Streptococcus spp (4/40 [10%]), and Pasteurella multocida (5/40 [13%]). The most common anaerobic isolates were Fusobacterium nucleatum (5/22 [23%]), Bacteroides pyogenes (4/22 [18%]), Bacteroides fragilis (3/22 [14%]), and Parvimonas micra (3/22 [14%]). Susceptibility against commonly used antimicrobials was available for 22 of 40 (55%) of the aerobic isolates. Not all antibiotics were tested for susceptibility at this institution due to known resistance. Of the number of susceptible organisms tested, 20 of 22 (91%) were susceptible to enrofloxacin, 14 of 22 (64%) were susceptible to trimethoprim/sulfamethoxazole, and 7 of 22 (32%) were susceptible to azithromycin (Supplementary Table S5). Data were only collected for the first culture in each case.

Treatment

Humane euthanasia was performed in 11 of 73 (15%) cases within 48 hours of presentation due to owner preference, considering disease severity, disease progression, or comorbidities.

Systemic antibiotic treatment only

Long-term antibiotic therapy as the sole treatment was initiated in 35 of 73 (48%) cases (Supplementary Table S3). Of those cases, 23 of 35 (66%) had more aggressive interventions recommended including abscess packing (17/22 [77%]) or extractions (6/22 [27%]), while euthanasia was recommended as a primary treatment in 3 of 35 (9%) cases secondary to disease severity. Six of 35 (17%) cases were ultimately euthanized due to disease progression within 2 months of initial diagnosis. The most frequently prescribed antibiotics in cases that received antibiotic therapy alone included azithromycin, enrofloxacin, penicillin G procaine, ceftiofur crystalline-free acid, trimethoprim/sulfamethoxazole, metronidazole, or a combination (min, 14 days; max, 180 days; median, 30 days). Azithromycin was prescribed alone or in combination in 18 of 35 (51%) cases and combinations with metronidazole were prescribed in 8 of 35 (23%) cases (combined with enrofloxacin, penicillin G procaine, trimethoprim/sulfamethoxazole). Bacterial culture (aerobic, anaerobic, or both) was performed in 19 of 35 (54%) cases. Cases that had bacterial cultures performed resolved the abscess in 31% (6/19) cases, compared to cases without cultures (6%, 1/16; P .1). Follow-up information was available for 28 of 35 (80%) cases, and 21 of 28 (75%) did not resolve (median follow-up time, 365 days; min, 60 days; max, 1,367 days [3.7 years]). Of the 7 of 28 (25%) cases treated solely with antibiotics that did resolve, there was a median disease-free time of 507 days (min, 166 days; max, 1,812 days [5 years]).

Surgical treatment

Abscess packing with antibiotic-soaked gauze using a previously described surgical protocol8 was performed in 20 of 73 (27%) cases (Table 3). Of these cases, 16 of 20 (80%) occurred solely at the UW-SVM, 2 of 20 (10%) were initiated at the UW-SVM and continued by a referring veterinarian, and 2 of 20 (10%) were performed solely by a referring veterinarian with guidance from a veterinarian at the UW-SVM following diagnosis of the odontogenic abscess at the UW-SVM. The treated odontogenic abscess was associated with the mandibular quadrant in 15 of 20 (75%) cases and the maxillary quadrant in 5 of 20 (25%) cases.

Antibiotics used to soak the sterile gauze strips for the abscess packing included ampicillin (30 mg/kg; 12/20 [60%]), ceftazidime (3/20 [15%]; dose not available), a combination of ampicillin and ceftazidime (2/20 [10%]), procaine G penicillin (60 to 70,000 IU/kg; 2/20 [10%]), or cefazolin (20 mg/kg; 1/20 [5%]). The gauze was replaced every 7 days (range, 6 to 8 days), and a median of 4 packings were performed (range, 2 to 7; IQR, 3 to 5). All packing cases had an additional anesthetic event to remove the gauze and close the surgical site. In all cases, the abscess packing protocol was combined with systemic antibiotic therapy including azithromycin, enrofloxacin, metronidazole, ceftiofur crystalline-free acid, trimethoprim/sulfamethoxazole, or a combination. Azithromycin was prescribed alone or in combination in 14 of 20 (70%) cases, and metronidazole combinations were prescribed in 6 of 20 (30%) cases.

Abscess resolution was achieved in 17 of 20 (85%) cases following treatment with the abscess-packing technique. The median disease-free time of rabbits treated with the abscess-packing technique was 375 days (55 to 1,096 days). Rabbits treated with the abscess-packing technique were significantly more likely to be cured of the disease than rabbits that received systemic antibiotics alone (P < .001).

Of the rabbits treated with the abscess-packing technique, 1 (1/20 [5%]) patient died under anesthesia during the second surgical packing. Another 2 (2/20 [10%]) cases elected to discontinue packings due to either asystole under general anesthesia or disease progression. The patient that underwent asystole had already successfully undergone abscess packings 8 months prior and was being treated for a novel, unrelated odontogenic abscess. The patient with disease progression was consistently pyrexic on presentation, had heavy Escherichia coli growth on bacterial culture, and developed a new, unrelated odontogenic abscess while undergoing abscess packings.

In 7 of 62 (11%) treated cases, a surgical technique other than abscess packing was elected including surgical extraction, marsupialization, or lancing. Information about abscess location, culture results, treatment, and outcome is available in Supplementary Table S4.

Discussion

This study assessed data from 72 rabbits diagnosed with 92 odontogenic abscesses and found that a combination of an abscess-packing protocol and long-term systemic antibiotics can be an effective treatment option with an 85% success rate. This is consistent with a prior retrospective study8 evaluating an abscess-packing protocol in 13 rabbits (93% success rate). Other surgical techniques to treat odontogenic abscesses in rabbits have been described, including extraoral tooth extraction and long-term systemic antibiotic therapy in 20 rabbits (90% success rate)14 and extraoral tooth extraction with marsupialization and long-term system antibiotic therapy in 200 rabbits (90% success rate).6 The previously described techniques have a success rate comparable to the abscess-packing approach and eliminate the need for repeated anesthetic events, which was associated with major complications in this study (2 [10%] cases underwent asystole associated with anesthesia).6,14 However, the extraction and marsupialization technique requires more advanced surgical skills, intensive postoperative care, and is associated with significantly higher risks of complications. Minor complications occurred in at least 40% of cases, and major complications including the formation of a bone sequestrum, repeated gingival failure, and mandibular fracture that necessitated further surgical intervention occurred in 16% of cases. There was also persistent or recurrent infection in 18% of cases that required repeat surgical treatment.6 In contrast, this study had minimal postoperative complications (none reported post–abscess packing) and only a single case (5%) had progressive disease while receiving the abscess-packing treatment. This study demonstrated that abscess packing as a treatment for odontogenic abscesses is an easily implementable procedure that can be taught across varying skill levels with minimal complications.

Another key difference between the previously described techniques and the abscess-packing technique is tooth extraction. It has previously been suggested that extracting cheek teeth associated with the odontogenic abscess is necessary to achieve abscess resolution.4,6 However, there were documented complications associated with tooth extraction in the 2 retrospective studies, including tooth elongation from the opposite side, alterations in the location of other teeth in the affected jaw, and subsequent development of periodontal disease.6,14 In both the current study and a previous study8 evaluating the less invasive abscess-packing technique, all successfully treated odontogenic abscesses resolved without the need for cheek tooth extraction. Consequently, this study demonstrated that successful outcomes for odontogenic abscesses do not necessarily require tooth extraction and thereby avoid complications with this technique, including those listed above as well as possible future anesthetic events associated with occlusal adjustments.

Rabbits treated solely with antibiotic therapy had a low abscess resolution rate (25%) compared to animals treated with the abscess-packing technique and systemic antibiotic therapy (85%). While other studies have not explicitly studied antibiotic treatment as the sole intervention, the findings from this study suggest antibiotics alone may be an inappropriate treatment choice in most cases but may be considered as a palliative option. Various factors, including the specific bacterial isolates and thick caseous abscess material, could contribute to the multifactorial challenges associated with antibiotic treatment alone. A greater percentage of cases in this study that had a bacterial culture performed resolved compared to cases that did not have a culture performed. Although the resolution rate was still low (31%), it may indicate that these cases received more targeted antibiotic therapy, and culture and sensitivity is recommended to provide appropriate antimicrobial treatment.

Bacterial culture results included a high prevalence of gram-negative aerobic bacterial isolates (35%). Previous studies have reported variable gram-negative aerobic bacterial isolate populations ranging from 2 of 12 (17%)17 to 30 of 52 (58%).12 The most common aerobic and anaerobic bacterial isolates in this study were Streptococcus and Pasteurella species and Fusobacterium and Bacteroides, respectively. Previous studies investigating bacterial isolates in rabbits with odontogenic abscesses had predominant isolate populations of Pseudomonas,12 Pasteurella,12 Streptococcus,6,14,17 Fusobacterium,6,12,14 Peptostreptococcus,12,17 Prevotella,6,17 Actinomyces,6,17 and Bacteroides species.12 While this study demonstrated some variability in isolates compared to previous studies, a consistent finding is that bacterial isolates from rabbit odontogenic abscesses are a combination of aerobic and anaerobic gram-positive and gram-negative organisms. Subsequently, it is recommended to perform aerobic and anaerobic culture and sensitivity to provide appropriate antimicrobial treatment. If culture and sensitivity cannot be performed due to abscess location or client constraints, it is recommended to prescribe an antimicrobial with a broad spectrum of activity to cover gram-negative and anaerobic bacteria. Based on the results from this study, an appropriate aerobic antibiotic choice may be trimethoprim/sulfamethoxazole or enrofloxacin. In this study population, a large proportion was treated empirically with azithromycin, which may not be an appropriate first-line treatment choice, given its limitations against anaerobes and gram-negative bacteria. Specifically, azithromycin is not an appropriate choice of treatment for B fragilis and Fusobacterium species.18 Therefore, it is recommended to provide anaerobic antibacterial coverage with a more broad-spectrum choice like metronidazole.

Two rabbits had odontogenic abscesses with E coli isolates, and both cases had a poor outcome. One case was euthanized due to severe comorbidities and multifocal odontogenic abscessation, and the other had progressive disease while undergoing abscess packings. In the previous study8 evaluating the abscess-packing technique, the only case that did not resolve was also associated with E coli. On the basis of available evidence, odontogenic abscesses associated with E coli carry a poor prognosis and therefore bacterial cultures in rabbits with odontogenic abscesses are recommended to provide clients with more prognostic information.

This study found that mini lop rabbits were more likely to be diagnosed with odontogenic abscesses. This is consistent with previous reports that demonstrated that lop-eared rabbits may exhibit a genetic predisposition to dental disease, warranting further investigation.19,20 In contrast, the male predisposition reported in other studies was not apparent in this dataset, highlighting the need for additional research to investigate associations between sex and dental disease in rabbits.1,6,21,22 Since previous studies did not consider the sex ratio in the overall rabbit population, assumptions based on the number of males in a subpopulation diagnosed with dental disease are not an accurate method to determine whether sex is a risk factor.

The mandibular quadrant was more commonly associated with odontogenic abscesses in this study. This is consistent with previous studies6,14,15 and hypothesized to be secondary to anatomical factors including a narrower mandibular arcade, increased attrition forces, or a closer proximity to the lymphatic system.10

This retrospective study had inherent limitations, including lack of follow-up and potential inaccuracies in record information. Future studies are recommended to determine a grading system for odontogenic abscesses, assess the relationship between breed and dental disease, and investigate prognostic indicators for this disease, including bacterial isolates or comorbidities.

In conclusion, this study determined that abscess packing in conjunction with systemic antibiotics is an effective treatment option for rabbits with odontogenic abscesses. Mini lop and rex rabbits were more likely to suffer from odontogenic abscesses, which may support a genetic predisposition toward dental disease. Bacterial culture demonstrated a mixture of aerobic and anaerobic bacteria with a high prevalence of gram-negative bacteria, and culture and susceptibility are recommended to provide appropriate antimicrobial coverage.

Supplementary Materials

Supplementary materials are posted online at the journal website: avmajournals.avma.org.

Acknowledgments

The authors thank Ms. Gabi Conidi for her assistance in obtaining follow-up information from pet owners and referring veterinary clinics.

Disclosures

Dr. Mans is a member of the JAVMA Scientific Review Board, but was not involved in the editorial evaluation of or decision to accept this article for publication.

No AI-assisted technologies were used in the generation of this manuscript.

Funding

The authors have nothing to disclose.

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