Transmission dynamics and pathogenesis of squirrelpox in UK red (Sciurus vulgaris) and grey squirrels (Sciurus carolinensis)

Dale, Timothy
Transmission dynamics and pathogenesis of squirrelpox in UK red (Sciurus vulgaris) and grey squirrels (Sciurus carolinensis). PhD thesis, University of Liverpool.

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Since the introduction of the non-native grey squirrel (Sciurus carolinensis) into the UK the native red squirrel has seen a dramatic decline in both abundance and distribution. There is an increasing body of evidence suggesting that rather than competition, a disease is in fact driving the demise of the red squirrel. Using survey and mortality data collected from one of the England’s last remaining red squirrel strongholds located in Merseyside, risk factors were identified that posed a threat to the remaining red squirrels. Squirrelpox virus (SQPV) known to be carried by grey squirrels but causes a severe skin disease in reds was identified as a significant risk factor and the cause of a 85% decline in red squirrels in the area in 2008. Mixed model regression links SQPV infection in grey squirrels with disease in reds squirrels. A post-epidemic survey reveals the presence of SQPV antibodies in some of the remaining red squirrels, indicating an estimated survival rate of 8%. In order to gain more information about the virus, two longitudinal mark-recapture studies were set up in Formby, Merseyside and Ness Gardens, Cheshire, to study red and grey squirrels respectively. A multiplex PCR was developed to monitor the infection status of squirrels in respect to SQPV and adenovirus (ADV). Grey squirrels showed high infection rates of both viruses, with little sign of any detrimental effect of infection. Red squirrels showed comparable levels of infection with ADV but SQPV remained very low. This suggested ADV to be endemic in both squirrels. While SQPV was endemic in grey squirrels and posed to be an epidemic threat to red squirrels. Although no significant association between SQPV and fleas was reported, fleas as potential vectors of SQPV could not be discounted. Of further interest was a possible interaction between the two viruses, where co-infection led to significantly higher levels of SQPV in the blood of grey squirrels. This may have implications for how infectious grey squirrels are and thus impacts on the risk of transfer to red squirrels. Although ADV may not be an immediate threat to red squirrels, the influence it may have on SQPV increases its relevance and warrants further investigation.

Item Type: Thesis (PhD)
Additional Information: Date: 2013-09 (completed)
Uncontrolled Keywords: squirrelpox, SQPV, squirrel, red, grey, invasive, species, wildlife, disease, adenovirus, ecology, virus, microparasite
Depositing User: Symplectic Admin
Date Deposited: 06 Aug 2014 10:58
Last Modified: 16 Dec 2022 04:41
DOI: 10.17638/00016253