sarcoid

Background 

This is the first report of Besnoitia bennetti in donkeys in Ireland. B. bennetti, an apicomplexan protozoan parasite specifc to equids, is an emerging pathogen in Europe. This parasite forms chronic intracytoplasmic cysts in cells of the mesenchymal lineage, mainly fbroblasts, in the skin, sclera and mucosa. Clinical signs in afected equine hosts vary from mild to severe debilitating disease. Little is known of the phylogeny, epidemiology or transmission of B. bennetti infection in donkeys, mules or horses. 

Case presentation 

Two cases of besnoitiosis in donkeys are presented. Both donkeys were born and raised in the south west of Ireland. The first case was a 2.5-year-old donkey that had a suspect sarcoid removed, while the second case, a 2-year-old donkey, had a biopsy of nodular dermatitis of the muzzle. Diagnosis was made by histopathology and the parasite species, B. bennetti, was confirmed by PCR followed by sequencing and microsatellite analysis. Both donkeys had high antibody titres against Besnoitia spp. Small (0.5 mm) scleral, conjunctival and dermal cysts over the muzzle were subsequently observed in both animals. Treatment with trimethoprim sulfadiazine for 30 days did not lead to clinical resolution. The fndings are compared to the cases of besnoitiosis in donkeys reported in the past 10 years throughout Europe. 

Conclusions 

Besnoitiosis should be considered as a differential diagnosis for chronic skin disease particularly in cases of cutaneous masses, non-pruritic dermatitis, and dermatitis that is not responsive to treatment in donkeys and other equids. Future studies are needed to investigate the prevalence of the disease in Irish donkeys, the spread of the disease and the potential impact on the health and welfare of the donkeys.

Equine sarcoids develop upon bovine papillomavirus type 1 or 2 (BPV1, BPV2) infection in conjunction with trauma and represent the most common tumour disease in horses and other equids, including donkeys. In face of a sarcoid outbreak involving 12 of 111 donkeys and mules at the ‘Rifugio degli Asinelli’, a subsidiary charity organization of The Donkey Sanctuary, non-invasively collected sample material including crusts, dandruff, swabs and hair roots was collected from sarcoid-affected and 26 healthy donkeys, as well as dandruff from a grooming kit and tabanids caught from or in the vicinity of sarcoid patients. In addition five previously collected sarcoids stored in formalin were provided.

DNA isolated from collected material was tested for the presence of the BPV1/2 E5 oncogene using PCR. Positive samples were further analysed by E2/E4 and LCR PCR and amplicon sequencing to determine a possible common source of infection via comparative alignment of intralesional BPV1/2 gene variants. IC/PCR was used to assess sample aliquots for the presence of BPV1/2 virions, and IHC to analyse five tumours for BPV1 E5 and L1 protein expression.

All sarcoid-affected donkeys, two of 55 tabanids and dandruff from a curry comb tested positive for BPV1/2 E5, yet negative by IC/PCR. Healthy animals were BPV1/2-free. IHC revealed different levels of intralesional E5 and L1 expression. A series of BPV1 E5, E2, and LCR variants and BPV2 E5 were detected from donkeys, indicating that they had accidently developed sarcoids at about the same time rather than having acquired disease from each other.