The host-parasite relationships in pyridoxine (vitamin B6) deficient cotton rats infected with <i>Litomosoides carinii</i> (Nematoda: Filaroidea)

Beg, M. A.; Fistein, Jon; Storey, D. M.

doi:10.1017/s0031182000064660

Cited by 18 publications

(20 citation statements)

References 22 publications

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“…Further, was not sensitive to the mean viral count or sample size. This lack of sensitivity to the mean is in contrast to previous descriptions of macroparasite load heterogeneity across wild organisms in which it was found that the negative binomial parameter ( k ) was sensitive to mean parasite burden [33]. However, given that parameter estimation is an imprecise exercise requiring very large sample sizes, significant problems have been identified with this way of measuring aggregation across study populations [27].…”

Section: Discussionmentioning

confidence: 57%

Birds Shed RNA-Viruses According to the Pareto Principle

et al. 2013

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A major challenge in disease ecology is to understand the role of individual variation of infection load on disease transmission dynamics and how this influences the evolution of resistance or tolerance mechanisms. Such information will improve our capacity to understand, predict, and mitigate pathogen-associated disease in all organisms. In many host-pathogen systems, particularly macroparasites and sexually transmitted diseases, it has been found that approximately 20% of the population is responsible for approximately 80% of the transmission events. Although host contact rates can account for some of this pattern, pathogen transmission dynamics also depend upon host infectiousness, an area that has received relatively little attention. Therefore, we conducted a meta-analysis of pathogen shedding rates of 24 host (avian) – pathogen (RNA-virus) studies, including 17 bird species and five important zoonotic viruses. We determined that viral count data followed the Weibull distribution, the mean Gini coefficient (an index of inequality) was 0.687 (0.036 SEM), and that 22.0% (0.90 SEM) of the birds shed 80% of the virus across all studies, suggesting an adherence of viral shedding counts to the Pareto Principle. The relative position of a bird in a distribution of viral counts was affected by factors extrinsic to the host, such as exposure to corticosterone and to a lesser extent reduced food availability, but not to intrinsic host factors including age, sex, and migratory status. These data provide a quantitative view of heterogeneous virus shedding in birds that may be used to better parameterize epidemiological models and understand transmission dynamics.

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Section: Discussionmentioning

confidence: 57%

Birds Shed RNA-Viruses According to the Pareto Principle

et al. 2013

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“…Parasite abundance data are often overdispersed relative to what is expected from a Poisson distribution, therefore a negative binomial distribution is often used [33], [34]. In addition, it is fairly frequent with a higher proportion of zeros than expected even from a negative binomial distribution [34], warranting the use of zero-inflated models [35].…”

Section: Methodsmentioning

confidence: 99%

Landscape Level Variation in Tick Abundance Relative to Seasonal Migration in Red Deer

et al. 2013

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Partial migration is common among northern ungulates, typically involving an altitudinal movement for seasonally migratory individuals. The main driving force behind migration is the benefit of an extended period of access to newly emerged, high quality forage along the green up gradient with increasing altitude; termed the forage maturation hypothesis. Any other limiting factor spatially correlated with this gradient may provide extra benefits or costs to migration, without necessarily being the cause of it. A common ectoparasite on cervids in Europe is the sheep tick (Ixodes ricinus), but it has not been tested whether migration may lead to the spatial separation from these parasites and thus potentially provide an additional benefit to migration. Further, if there is questing of ticks in winter ranges in May before spring migration, deer migration may also play a role for the distribution of ticks. We quantified the abundance of questing sheep tick within winter and summer home ranges of migratory (n = 42) and resident red deer (Cervus elaphus) individuals (n = 32) in two populations in May and August 2009–2012. Consistent with predictions, there was markedly lower abundance of questing ticks in the summer areas of migrating red deer (0.6/20 m2), both when compared to the annual home range of resident deer (4.9/20 m2) and the winter home ranges of migrants (5.8/20 m2). The reduced abundances within summer home ranges of migrants were explained by lower abundance of ticks with increasing altitude and distance from the coast. The lower abundance of ticks in summer home ranges of migratory deer does not imply that ticks are the main driver of migration (being most likely the benefits expected from forage maturation), but it suggests that ticks may add to the value of migration in some ecosystems and that it may act to spread ticks long distances in the landscape.

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“…Many studies have been carried out in this area in order to develop our understanding of what causes heterogeneity in the distribution of macroparasites within a host population [68]. Parasite aggregation in the wild is often complex, in macro-parasitic infections the majority of hosts are observed harbouring a low number of parasites with a minority of hosts harbouring a large number [69]. Such skewed aggregations have been shown to follow a negative binomial distribution [66,67,69].…”

Section: Discussionmentioning

confidence: 99%

“…Parasite aggregation in the wild is often complex, in macro-parasitic infections the majority of hosts are observed harbouring a low number of parasites with a minority of hosts harbouring a large number [69]. Such skewed aggregations have been shown to follow a negative binomial distribution [66,67,69]. The negative binomial distribution, (defined as s 2 = m + m 2 /k , where s 2 and m are the variance and mean respectively) quantifies the (inverse) degree of aggregation via the parameter k [70] such that for small k parasite aggregation is increased, whereas for large k aggregation decreases.…”

Section: Discussionmentioning

confidence: 99%

Predicting the Potential for Natural Recovery of Atlantic Salmon (Salmo salar L.) Populations following the Introduction of Gyrodactylus salaris Malmberg, 1957 (Monogenea)

et al. 2016

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Gyrodactylus salaris (Monogenea, Platyhelminthes) is a notifiable freshwater pathogen responsible for causing catastrophic damage to wild Atlantic salmon stocks, most notably in Norway. In some strains of Baltic salmon (e.g., from the river Neva) however, the impact is greatly reduced due to some form of innate resistance that regulates parasite numbers, resulting in fewer host mortalities. Gyrodactylus salaris is known from 17 European states; its status in a further 35 states remains unknown; the UK, the Republic of Ireland and certain watersheds in Finland are free of the parasite. Thus, the parasite poses a serious threat if it emerges in Atlantic salmon rearing regions throughout Europe. At present, infections are generally controlled via extreme measures such as the treatment of entire river catchments with the biocide rotenone, in order to remove all hosts, before restocking with the original genetic stock. The use of rotenone in this way in EU countries is unlikely as it would be in contravention of the Water Framework Directive. Not only are such treatments economically and environmentally costly, they also eradicate the potential for any host/parasite evolutionary process to occur. Based on previous studies, UK salmon stocks have been shown to be highly susceptible to infection, analogous to Norwegian stocks. The present study investigates the impact of a G. salaris outbreak within a naïve salmon population in order to determine long-term consequences of infection and the likelihood of coexistence. Simulation of the salmon/ G. salaris system was carried out via a deterministic mathematical modelling approach to examine the dynamics of host-pathogen interactions. Results indicated that in order for highly susceptible Atlantic strains to evolve a resistance, both a moderate-strong deceleratingly costly trade-off on birth rate and a lower overall cost of the immune response are required. The present study provides insights into the potential long term impact of G. salaris if introduced into G. salaris-free territories and suggests that in the absence of external controls salmon populations are likely to recover to high densities nearing 90% of that observed pre-infection.

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The host-parasite relationships in pyridoxine (vitamin B6) deficient cotton rats infected with Litomosoides carinii (Nematoda: Filaroidea)

Cited by 18 publications

References 22 publications

Birds Shed RNA-Viruses According to the Pareto Principle

Birds Shed RNA-Viruses According to the Pareto Principle

Landscape Level Variation in Tick Abundance Relative to Seasonal Migration in Red Deer

Predicting the Potential for Natural Recovery of Atlantic Salmon (Salmo salar L.) Populations following the Introduction of Gyrodactylus salaris Malmberg, 1957 (Monogenea)

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