Dermatophilus congolensis associated bronchopneumonia in an alpaca

Abstract A severe, chronic, locally extensive granulomatous bronchopneumonia was diagnosed on post‐mortem and histopathological examination of an adult alpaca. Dermatophilus congolensis organisms were isolated from the lungs and genotypic identification of aerobic culture was confirmed by sequence analysis of the entire 16S rDNA gene. This is the first report of D. congolensis‐associated bronchopneumonia in any species.


| INTRODUC TI ON
Dermatophilus congolensis is a Gram-positive filamentous bacterium which is usually known to cause skin disease in a wide range of domestic and wild animals throughout the world, especially in the humid tropics and subtropics. The dermal lesions are characterised by raised, crusty, alopecic and sometimes papillomatous lesions covered by thick keratinaceous incrustations (Hargis & Myers, 2017;Mauldin & Peters-Kennedy, 2015). In temperate countries, sheep and goats are commonly affected and a sporadic proliferative pyogranulomatous pododermatitis has been seen in alpacas in Australia (Horadagoda unpublished data). Apart from skin infections, in rare instances, the organism can cause pyogranulomatous infections in the lymph nodes (Byrne, Rand, McElliott, Samitz, & Brault, 2010).
To the author's knowledge, this is the first report of D. congolensis associated with a case of bronchopneumonia in an animal.

| C A S E HIS TORY
A 12-month-old male alpaca was presented to the University of Sydney Veterinary Teaching Hospital, Camden for evaluation of weight loss and cough of 2 weeks duration. The alpaca had been treated 6 months previously for draining of abscesses under the jaw and in the groin, thought to be caseous lymphadenitis (CLA). These abscesses had resolved, and the alpaca had been otherwise clinically normal and had a good appetite until 2 weeks prior to presentation.

S H O R T C O M M U N I C A T I O N
ventral thorax with marked soft tissue opacity effacing the margins of the cardiac silhouette/ventral diaphragm and multiple air bronchograms. Severe bronchopneumonia with or without pleural effusion was considered likely. Given the clinical signs, blood sample and radiographic findings, the owners were offered a very guarded prognosis for survival so elected to euthanise the alpaca.
Post-mortem examination revealed marked, locally extensive, cranioventral consolidation involving 60%-70% of the lungs with the pleural surfaces containing multifocal to coalescing, firm creamy white nodules (Figure 1). On the cut surface, the nodules extended into the lung parenchyma and there were multiple fibrous adhesions between pleural surfaces. The tracheobronchial lymph nodes were enlarged. The left inguinal lymph node was firm and enlarged. All other body systems were grossly normal.  Splendore-Hoeppli material. This material is thought to be antigenantibody complexes together with tissue debris and fibrin (Hargis & Myers, 2017). Splendore-Hoeppli material is seen with certain persistent, poorly degradable, foreign body antigens and with fungal infections such as coccidioidomycosis, sporotrichosis as well bacterial diseases caused by Actinomyces bovis, Actinobacillus lignieresii and Staphylococcus aureus (Hargis & Myers, 2017;Jones, Hunt, & King, 1997). To the author's knowledge, the Splendore-Hoeppli phenomenon is not reported as a histomorphological feature in infections caused by D. congolensis.

| D ISCUSS I ON
The histology of the inguinal lymph node showed a concurrent infection with granulomatous inflammation characteristic of D. congolensis abutting large areas of necrosis with mineralisation, consistent with CLA caused by Corynebacterium pseudotuberculosis. Concurrent infections of dermatophilosis and CLA has been reported in outbreak forms in camels (Tarazi & Al-Ani, 2016). In the present case, this lesion may reflect residual infection from the previously, suspected episode of CLA, 6 months prior to this presentation. According to Valli, Kiupel, Bienzle, and Wood (2015) as a general rule, once the infection is established in a node it is persistent although in some instances it may be cleared when the node ruptures. The treatment records of the earlier presentation at this Hospital reported that the lesion content was shelled out from the submandibular and superficial inguinal lymph nodes at surgery and the wounds left to heal without sutures at the site of incision. This procedure is likely to have some residual organisms which are responsible for the histological changes in the inguinal lymph node.
In the blood work, the marked eosinophilia is a significant finding, and this is reflected by the mobilisation of circulatory eosinophils by pulmonary granulomatous inflammatory foci containing Splendore-Hoeppli material and the surrounding pneumonic lung tissue. Although the functions of eosinophils are not fully understood they are known to be involved in the modulation of allergic inflammation and immune-complex reactions (Weiser, 2012).
Given that Splendore-Hoeppli material originates from antigenantibody complexes, it is likely that eosinophils are attracted to this material resulting in an increased demand in circulation and activation of the haemopoietic system. The association between Splendore-Hoeppli material and eosinophils is supported by another report which describes multiple eosinophilic granuloma in a nasal lesion caused by toxigenic Corynebacterium ulcerans although the occurrence of a concurrent eosinophilia is not mentioned (Murakami et al., 2014).
Dermatophilus congolensis is generally considered a dermal pathogen affecting a wide range of animals with rare occurrence of lesions in other tissues. The clinical findings reported in this paper have for the first time shown that D. congolensis can be associated with bronchopneumonia and that the organism should be considered as a pathogen in investigations relating to chronic pulmonary infections characterised by granulomatous inflammation. The presence of the organism in carrier animals and within dust particles for long periods in the environment could potentially allow dissemination of the pulmonary disease or the establishment of new infections across different species.

ACK N OWLED G EM ENT
The authors would like to thank Dr Alex Young for her assistance with the radiographic interpretation.

CO N FLI C T O F I NTE R E S T
The authors have no conflict of interest.

E TH I C A L S TATEM ENT
The authors confirm that the ethical policies of the journal, as noted on the journal's author guidelines page, have been adhered to. No ethical approval was required as this is an investigation of an animal at post-mortem examination.