Detection of squirrel poxvirus by nested and real-time PCR from red (Sciurus vulgaris) and grey (Sciurus carolinensis) squirrels

This project describes the design and optimization of a real-time PCR for SQPV. Comparison with the nested PCR showed the real-time assay to be more sensitive by one log and able to detect approximately 144 genome copies per mg of tissue.The real-time PCR has been used to quantify viral genome load in tissues from diseased and apparently healthy red and grey squirrels, and suggests that the titre of virus in tissues from diseased red squirrels is considerably higher than that found even in a grey squirrel with cutaneous lesions.Squirrelpox is a disease caused by a virus of the family Poxviridae. Although originally described as a parapoxvirus, it is now considered to belong to a previously undescribed genus of the Chordopoxvirinae subfamily [1,2]. In the UK, squirrelpox virus (SQPV) is known to infect two species of squirrel: the native red squirrel (Sciurus vulgaris) and the introduced Eastern grey squirrel (Sciurus carolinensis) [3]. In red squirrels, the disease is characterized by a severe multifocal ulcerative and exudative dermatitis with hemorrhagic scabs which is predominantly fatal if untreated. Such lesions appear primarily on the eyelids, nose and lips, with later spread to the digits, inguinal area and ventral skin of the body [4-7]. Affected animals develop widespread epidermal necrosis, resulting in dehydration, a loss of body condition and ultimately death, although in experimental controlled conditions, one of four red squirrels were able to recover [8]. In contrast to red squirrels, grey squirrels generally do not show any clinical signs of infection [8]. Only one exceptional case of disease has been described in a grey squirrel with proliferative oral lesions from which poxviruses were demonstrated by electron microscopy [9].The first recorded epidemics of pox-like disease in red squirrels occurred in the 1900 s [10] and continue to the present day [4,7,11]. The origins of SQPV are poorly understood, but it is suggested that the virus was introduce