Grey squirrels have high seroprevalence to a parapoxvirus associated with deaths in red squirrels

Sainsbury, Anthony W.; Nettleton, P. F.; Gilray, Janice; Gurnell, John

doi:10.1111/j.1469-1795.2000.tb00107.x

Cited by 93 publications

(67 citation statements)

References 19 publications

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“…Although Sainsbury et al (2000) detected a high seroprevalence to SQPV in English and Welsh gray squirrels, no antibodies to SQPV were detected in the geographically isolated population in Scotland, and it is believed that, until recently, Scottish gray squirrels were not reservoirs of the virus. Where mixed populations of red squirrels and gray squirrels existed in the absence of SQPV, such as in Scotland (until recently) and in Italy, the red squirrel has been shown to decline but the rate of decline of red squirrels in the presence of both SQPV and gray squirrels (in Cumbria) is 17-25 times faster (Rushton et al, 2006).…”

Section: Introductionmentioning

confidence: 73%

“…Figure 2 shows the temporal and spatial distribution of cases of SQPV-TEM-positive and suspected red squirrels in northern England and southern Scotland for each year between 1993 and 2005, the geographical location of red squirrels with skin lesions that were TEM-negative, the geographical location of all other red squirrels examined postmortem, and the changing and cumulative pattern of gray squirrel distribution in England only, south of a line between the Solway Firth and Holy Island. Up until 2005, only English and Welsh populations of gray squirrels had been found to be seropositive to SQPV (Sainsbury et al, 2000), therefore, the gray squirrel distribution depicted in Figure 2 also represents the distribution of seropositive gray squirrels in northern England and southern Scotland. The majority of cases of SQPV disease confirmed by TEM occurred in areas also inhabited by seropositive gray squirrels.…”

Section: Resultsmentioning

confidence: 97%

“…Incisions were made in order that all organ systems could be examined in situ and ex situ after removal, and abnormalities of color, consistency, shape, or appearance were noted. A sample of fluid from the thorax was collected, whenever possible, and analyzed for antibodies to SQPV by ELISA (Sainsbury et al, 2000).…”

Section: Methodsmentioning

confidence: 99%

“…On the assumption that the virus is spread to red squirrels by direct contact with gray squirrels, it would be expected that epidemics of disease would be more likely to occur during periods of gray squirrel dispersal and/or breeding because increased movement of gray squirrels would lead to more encounters between gray squirrels and red squirrels. We also predicted that, given the apparent high mortality rate of red squirrels in outbreaks of SQPV disease and the very low seroprevalence to SQPV in red squirrels (Sainsbury et al, 2000), red squirrels in contact with the virus would die and there would be no signs of recovery following exposure. In order to test these hypotheses, we carried out examinations on red squirrels found dead in England, Wales, and Scotland between 1993 and 2005, diagnosed cases of poxvirus disease from pathological signs and examination by transmission electron microscopy (TEM), tested the same squirrels for SQPV antibody by enzyme-linked immunosorbent assay (ELISA), mapped the cases of SQPV disease using a geographical information system (GIS) and analyzed the temporal and spatial patterns in disease distribution, with respect to the distribution of gray squirrels and the density of red squirrels and gray squirrels, using woodland type as a measure of squirrel density.…”

Section: Introductionmentioning

confidence: 99%

“…The gray squirrel, Sciurus carolinensis, an invasive introduced species, has high seroprevalence to SQPV in England and Wales and is likely to be a reservoir host and to transmit infection to the red squirrel (Sainsbury et al, 2000). As gray squirrels, introduced into central and southern England from 1876, have encroached on red squirrel populations, the transmission of SQPV and the ensuing disease in red squirrels, has given the gray squirrel a competitive advantage over the red squirrel allowing the former to increase its geographic range rapidly through England and Wales over the last 100 years (Rushton et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Poxviral Disease in Red Squirrels Sciurus vulgaris in the UK: Spatial and Temporal Trends of an Emerging Threat

et al. 2008

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The squirrel poxvirus (SQPV) is the probable mediator of apparent competition between the introduced invading gray squirrel (Sciurus carolinensis) and the red squirrel (Sciurus vulgaris) in the UK, and modeling studies have shown that this viral disease has had a significant impact on the decline of the red squirrel in the UK. However, given our limited understanding of the epidemiology of the disease, and more generally the effects of invasive species on parasite ecology, there is a need to investigate the transmission dynamics and the relative pathogenicity of the virus between species. We aimed to increase our knowledge of these processes through an empirical study in which we: (i) used pathological signs and transmission electron microscopy (TEM) to diagnose SQPV disease in red squirrels found dead during scanning surveillance between 1993 and 2005; (ii) detected antibody to SQPV using an enzyme-linked immunosorbent assay (ELISA) in the same animals; and (iii) mapped cases of the disease, and the gray squirrel distribution, using a geographical information system. We analyzed the distribution of cases of SQPV disease according to woodland type, a measure of squirrel density. SQPV disease occurred only in areas of England also inhabited by seropositive gray squirrels, and as the geographical range of gray squirrels expanded, SQPV disease occurred in these new gray squirrel habitats, supporting a role for the gray squirrel as a reservoir host of the virus. There was a delay between the establishment of invading gray squirrels and cases of the disease in red squirrels which implies gray squirrels must reach a threshold number or density before the virus is transmitted to red squirrels. The spatial and temporal trend in SQPV disease outbreaks suggested that SQPV disease will have a significant effect on Scottish populations of red squirrels within 25 years. The even spread of cases of disease across months suggested a direct rather than vector-borne transmission route is more likely. Eight juvenile and sub-adult free-living red squirrels apparently survived exposure to SQPV by mounting an immune response, the first evidence of immunity to SQPV in free-living red squirrels, which possibly suggests a changing host-parasite relationship and that the use of a vaccine may be an effective management tool to protect remnant red squirrel populations.

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Section: Introductionmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Poxviral Disease in Red Squirrels Sciurus vulgaris in the UK: Spatial and Temporal Trends of an Emerging Threat

et al. 2008

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Poxvirus Infections

Bourne¹,

Duff²,

Vikøren³

2012

Infectious Diseases of Wild Mammals and Birds in Europe

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European red squirrel population dynamics driven by squirrelpox at a gray squirrel invasion interface

Chantrey

Dale

Read

et al. 2014

Ecology and Evolution

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Infectious disease introduced by non-native species is increasingly cited as a facilitator of native population declines, but direct evidence may be lacking due to inadequate population and disease prevalence data surrounding an outbreak. Previous indirect evidence and theoretical models support squirrelpox virus (SQPV) as being potentially involved in the decline of red squirrels (Sciurus vulgaris) following the introduction of the non-native gray squirrel (Sciurus carolinensis) to the United Kingdom. The red squirrel is a major UK conservation concern and understanding its continuing decline is important for any attempt to mitigate the decline. The red squirrel–gray squirrel system is also exemplary of the interplay between infectious disease (apparent competition) and direct competition in driving the replacement of a native by an invasive species. Time series data from Merseyside are presented on squirrel abundance and squirrelpox disease (SQPx) incidence, to determine the effect of the pathogen and the non-native species on the native red squirrel populations. Analysis indicates that SQPx in red squirrels has a significant negative impact on squirrel densities and their population growth rate (PGR). There is little evidence for a direct gray squirrel impact; only gray squirrel presence (but not density) proved to influence red squirrel density, but not red squirrel PGR. The dynamics of red SQPx cases are largely determined by previous red SQPx cases, although previous infection of local gray squirrels also feature, and thus, SQPV-infected gray squirrels are identified as potentially initiating outbreaks of SQPx in red squirrels. Retrospective serology indicates that approximately 8% of red squirrels exposed to SQPV may survive infection during an epidemic. This study further highlights the UK red squirrel – gray squirrel system as a classic example of a native species population decline strongly facilitated by infectious disease introduced by a non-native species. It is therefore paramount that disease prevention and control measures are integral in attempts to conserve red squirrels in the United Kingdom.

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Grey squirrels have high seroprevalence to a parapoxvirus associated with deaths in red squirrels

Cited by 93 publications

References 19 publications

Poxviral Disease in Red Squirrels Sciurus vulgaris in the UK: Spatial and Temporal Trends of an Emerging Threat

Poxviral Disease in Red Squirrels Sciurus vulgaris in the UK: Spatial and Temporal Trends of an Emerging Threat

Poxvirus Infections

European red squirrel population dynamics driven by squirrelpox at a gray squirrel invasion interface

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