Chronic wasting disease: Possible transmission mechanisms in deer

Potapov, Alexey; Merrill, Evelyn H.; Pybus, M. J.; Coltman, David W.; Lewis, Mark A.

doi:10.1016/j.ecolmodel.2012.11.012

Cited by 38 publications

(77 citation statements)

References 52 publications

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“…Female white-tailed and mule deer form matrilineal groups with stable home ranges, with minimum overlap with other matrilineal groups. Direct contact in the form required for pathogen transfer is most likely during male-male combat and female-male courtship (Potapov et al 2013). The higher prevalence in adult males could be explained by males visiting many groups of females, increasing the overall likelihood of visiting an infected group (Grear et al 2010).…”

Section: Infection Pattern and Mode Of Transmissionmentioning

confidence: 99%

“…Chronic wasting disease was first observed in captive mule deer (Odocoileus hemionus) in the late 1960s in Colorado, USA. Further, the demographic pattern of infection can shed light on the mode of transmission (Potapov et al 2013) and hence provide keys to mitigation. All individuals infected with CWD eventually die from the disease if they live long enough.…”

Section: Introductionmentioning

confidence: 99%

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The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

et al. 2019

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and J. V age. 2019. The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage.Abstract. Infection patterns linked to age and sex are crucial to predict the population dynamic effects of diseases in long-lived species. How such demographic patterns of infection arise is often multifactorial, although the cause is commonly seen as a combination of immune status as well as variation in pathogen exposure. Prion diseases are particularly interesting, as they do not trigger an adaptive immune response; hence, differences in pathogen exposure linked to behavior could be the prime determinant of the pattern of infection. In cervids, the fatal prion disease, chronic wasting disease (CWD), is spreading geographically, with economic and cultural consequences in affected areas in North America, and all infected individuals eventually die from disease-associated sequelae if they live long enough. Understanding the causes of the demographic pattern of infection with CWD is therefore urgent but is limited by the fact that reported data primarily come from related deer species in North America. The recent (detected 2016) emergence of CWD among wild alpine reindeer (Rangifer tarandus) in Norway with a different social organization, that is, no home range behavior and no matrilineal female groups, offers an opportunity to advance our understanding of how behavior influences the infection patterns. Testing of 1081 males and 1278 females detected 19 animals positive for abnormal prion protein in brain and/or lymphatic tissues. No calves and only one male yearling were infected, with the remaining positives being adults (representing 1.5% of adult males and 0.5% of adult females). We found a strong sex-biased infection pattern in reindeer (with infection 2.7 times more likely in adult males), which is similar to the results reported in mule deer and white-tailed deer. The hazard of being detected as positive increased with age in males. There was no close genetic relatedness among positive animals. The results were consistent with the within-group contact of males being a possible major route of transmission. We discuss the demographic pattern of infection with CWD in view of the lack of stable home range behavior and other key behavioral traits of reindeer relevant to understanding pathogen exposure in general.

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Section: Infection Pattern and Mode Of Transmissionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

et al. 2019

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“…As well as influencing the transfer of information throughout a population, the properties of such associations can also affect the rate of spread of infectious diseases [3]. For social species, epidemiological models that assume all hosts have equal probability of association and disease transmission, and that ignore seasonal variation, are no longer considered suitable for the study of complex diseases [4, 5]. To enhance models to guide disease control, studies are needed to quantify the extent to which individuals choose whom to associate with and factors relating to these choices.…”

Section: Introductionmentioning

confidence: 99%

“…The complexity of this disease is due to its transmission through both animal-to-animal contact and through the environment, its lengthy infectious period (>1.5 years), and the persistence of prions in the environment for at least 2.5 years [9, 10]. These factors highlight the need for detailed information on mule deer social behaviour and the dynamics of prions in the environment [5, 11] to parameterise dynamic disease models and inform cervid population management programs. The validity of CWD transmission model outcomes is reliant on accurate parameter estimates that describe deer sociality.…”

Section: Introductionmentioning

confidence: 99%

Mule deer spatial association patterns and potential implications for transmission of an epizootic disease

et al. 2017

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Animal social behaviour can have important effects on the long-term dynamics of diseases. In particular, preferential spatial relationships between individuals can lead to differences in the rates of disease spread within a population. We examined the concurrent influence of genetic relatedness, sex, age, home range overlap, time of year, and prion disease status on proximal associations of adult Rocky Mountain mule deer (Odocoileus hemionus hemionus) in a chronic wasting disease endemic area. We also quantified the temporal stability of these associations across different sex, age, and disease status classes. We used three years of high frequency telemetry data from 74 individuals to record encounters within 25 m of each other, and to calculate seasonal home range overlap measured by volume of intersection (VI). The strength of pairwise spatial association between adult mule deer was independent of genetic relatedness, age and disease status. Seasonal variation in association strength was not consistent across years, perhaps due to annual changes in weather conditions. The influence of home range overlap on association strength varied seasonally, whereby associations were stronger in pre-rut and fawning than in the rest of the seasons. The sexes of individuals also interacted with both VI and season. At increasing levels of VI, associations were stronger between females than between males and between females and males. The strongest associations in pre-rut were between males, while the strongest in rut were between females and males. The temporal stability of associations was markedly dependant on the sex and the diagnosis of the associating pair. Our findings highlight the importance of considering concurrent effects of biological and environmental factors when seeking to understand the role of social preference in behavioural ecology and disease spread. Applying this knowledge in epidemiological modelling will shed light on the dynamics of disease transmission among mule deer.

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“…CWD is a prion disease, and, to date, it is not known how to control the disease. Our previous modelling work [11] showed evidence that CWD transmission may result primarily from FD mechanisms related to deer social organization for both direct and environmental transmission [12]. In the case when the disease prevalence grows significantly slower than the rate at which prions decay or become inaccessible to deer [13], both mechanisms can be described within the framework of SI-type model without explicit environmental compartment.…”

Section: Introductionmentioning

confidence: 99%

Wildlife disease elimination and density dependence

2012

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Disease control by managers is a crucial response to emerging wildlife epidemics, yet the means of control may be limited by the method of disease transmission. In particular, it is widely held that population reduction, while effective for controlling diseases that are subject to density-dependent (DD) transmission, is ineffective for controlling diseases that are subject to frequency-dependent (FD) transmission. We investigate control for horizontally transmitted diseases with FD transmission where the control is via culling or harvest that is non-selective with respect to infection and the population can compensate through DD recruitment or survival. Using a mathematical model, we show that culling or harvesting can eradicate the disease, even when transmission dynamics are FD. Eradication can be achieved under FD transmission when DD birth or recruitment induces compensatory growth of new, healthy individuals, which has the net effect of reducing disease prevalence by dilution. We also show that if harvest is used simultaneously with vaccination, and there is high enough transmission coefficient, application of both controls may be less efficient than vaccination alone. We illustrate the effects of these control approaches on disease prevalence for chronic wasting disease in deer where the disease is transmitted directly among deer and through the environment.

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Chronic wasting disease: Possible transmission mechanisms in deer

Cited by 38 publications

References 52 publications

The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

Mule deer spatial association patterns and potential implications for transmission of an epizootic disease

Wildlife disease elimination and density dependence

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