Animal Health and Biotechnology Group (SaBio), Spanish National Wildlife Research Institute (IREC CSIC-UCLM-JCCM) Ciudad Real, Spain.
Front Cell Infect Microbiol. 2013 Jun 27;3:23. doi: 10.3389/fcimb.2013.00023. Print 2013.
The interactions between host individual, host population, and environmental factors modulate parasite abundance in a given host population. Since adult exophilic ticks are highly aggregated in red deer (Cervus elaphus) and this ungulate exhibits significant sexual size dimorphism, life history traits and segregation, we hypothesized that tick parasitism on males and hinds would be differentially influenced by each of these factors. To test the hypothesis, ticks from 306 red deer-182 males and 124 females-were collected during 7 years in a red deer population in south-central Spain. By using generalized linear models, with a negative binomial error distribution and a logarithmic link function, we modeled tick abundance on deer with 20 potential predictors. Three models were developed: one for red deer males, another for hinds, and one combining data for males and females and including "sex" as factor. Our rationale was that if tick burdens on males and hinds relate to the explanatory factors in a differential way, it is not possible to precisely and accurately predict the tick burden on one sex using the model fitted on the other sex, or with the model that combines data from both sexes. Our results showed that deer males were the primary target for ticks, the weight of each factor differed between sexes, and each sex specific model was not able to accurately predict burdens on the animals of the other sex. That is, results support for sex-biased differences. The higher weight of host individual and population factors in the model for males show that intrinsic deer factors more strongly explain tick burden than environmental host-seeking tick abundance. In contrast, environmental variables predominated in the models explaining tick burdens in hinds.
宿主个体、宿主种群和环境因素之间的相互作用调节了特定宿主种群中寄生虫的丰度。由于成年嗜血性蜱在马鹿（ Cervus elaphus ）中高度聚集，并且这种有蹄类动物表现出显著的性二型性、生活史特征和分离，我们假设蜱寄生在雄性和雌性马鹿身上会受到这些因素的不同影响。为了验证这一假设，我们在西班牙中南部的一个马鹿种群中，在 7 年内从 306 只马鹿身上采集了 182 只雄性和 124 只雌性的蜱。通过使用广义线性模型，采用负二项式误差分布和对数链接函数，我们用 20 个潜在预测因子来对鹿身上的蜱数量进行建模。我们开发了三个模型：一个用于马鹿雄性，另一个用于雌性，还有一个用于合并雄性和雌性的数据，并包含“性别”作为因子。我们的理由是，如果雄性和雌性身上的蜱虫负担与解释因素以不同的方式相关，那么使用拟合于另一性别的模型或合并两性数据的模型来准确地预测一性别的蜱虫负担是不可能的。我们的结果表明，马鹿雄性是蜱虫的主要目标，每个因素的体重在性别之间有所不同，并且每个特定性别的模型都无法准确预测另一性别的动物的负担。也就是说，结果支持性别偏向差异。雄性模型中宿主个体和种群因素的权重较高，表明内在的鹿因素比环境中宿主寻找的蜱虫丰度更能解释蜱虫负担。相比之下，环境变量在解释雌性蜱虫负担的模型中占主导地位。
