Dermatopathology of Orf Virus (Malaysian Isolates) in Mice Experimentally Inoculated at Different Sites with and without Dexamethasone Administration.

Jamilu Abubakar Bala,Krishnan Nair Balakrishnan,Tay Kimmy,Mohd Azmi Mohd Lila,Abd Wahid Haron,Mustapha Mohamed Noordin,Idris Umar Hambali,Yusuf Abba,Ramlan Bin Mohamed,Ashwaq Ahmed Abdullah,Faez Firdaus Abdullah Jesse,Asinamai Athliamai Bitrus

doi:10.1155/2018/9207576

Abstract

Orf is a clinical manifestation of parapoxvirus infection often fatal in goats and sheep especially when they are under stress or influenced by unfavorable environment. This study investigated the pathogenicity of two Orf virus isolates (ORFV UPM1/14 and UPM2/14) and host response in mouse model by using different inoculation sites with/without prior exposure to dexamethasone. Treatments with dexamethasone served as an immunosuppressant that may mimic stress situation in affected animals. Groups of five mice were given intradermal injection of 0.2 mL of tissue culture infective dose 50 (TCID50) of UPM1/14 (Group 1) and UPM2/14 (Group 2) at the dorsum (Group 1A; Group 2A), ear pinna (Group 1B; Group 2B), and labial commissure (Group 1C; Group 2C). An inoculum 0.2 mL of UPM1/14 was administered to animals treated with dexamethasone (n=5; 5 mg/kg/day intraperitoneally) and nondexamethasone (n=5) groups at the dorsum, ear pinna, and labial commissure. No significant difference (p>0.05) was observed in the mean lesion scores among the groups of different inoculation sites or between dexamethasone-treated and nontreated groups. However, there was a significant difference (p<0.05) in the mean stratum thickness of affected skin following inoculation with UPM2/14 isolate at the ear pinna and labial commissure. Histopathology examination revealed keratosis, acanthosis, and ballooning degeneration in the skin of affected mice. Orf virus DNA was detected in the skin samples by targeting F1L and B2L virus-specific genes in polymerase chain reaction (PCR) assay. Intradermal inoculation with UPM1/14 or UPM2/14 isolate produced a mild skin lesion in mice, and there was no significant difference in orf disease manifestation despite variation of inoculation sites. Similarly, short-term dexamethasone administration gave no adverse effects on pathogenicity of orf virus isolates.

Highlights

Orf virus (ORFV) belongs to the genus Parapoxvirus (PPV) of the family Poxviridae [1]
ORFV was grown in LT cells and it was monitored daily for development of cytopathic effects
Scabs formation was observed at the inoculation sites of mice inoculated at the dorsum and labial commissure after 5 days of inoculation

Summary

Introduction

Orf virus (ORFV) belongs to the genus Parapoxvirus (PPV) of the family Poxviridae [1]. It is the etiological agent of contagious ecthyma (CE), a severe exanthematic dermatitis that affects domestic and wild small ruminants [2]. Orf has been reported in camels and camelids, members of the Cervidae family, and various other ruminants. Cats, and squirrels can become infected with the orf virus [3, 4]. Based on a recent seroprevalence study, evaluation of IgM antibodies in small ruminant populations showed higher incidence in goats than sheep [5]. The disease has a zoonotic potential for those who are in close contact with animals such as veterinarians, farmers, animal attendants, and visitors [6,7,8]

Methods

Results

Conclusion