Variation in the prevalence and abundance of acanthocephalans in brown-nosed coatis Nasua nasua and crab-eating foxes Cerdocyon thous in the Brazilian Pantanal

Abstract Host infection by parasites is influenced by an array of factors, including host and environmental features. We investigated the relationship between host sex, body size and age, as well as seasonality on infection patterns by acanthocephalan in coatis (Procyonidae: Nasua nasua) and in crab-eating foxes (Canidae: Cerdocyon thous ) from the Brazilian Pantanal wetlands. Between 2006 and 2009, we collected faecal samples from these hosts and analyzed for the presence of acanthocephalan eggs. Prevalence, abundance and intensity of eggs of acanthocephalans were calculated. Egg abundance was analyzed using generalized linear models (GLM) with a negative binomial distribution and models were compared by Akaike criteria to verify the effect of biotic and abiotic factors. Prevalence of acanthocephalans was higher in the wet season in both host species but did not differ between host sexes; however, adult crab-eating foxes showed higher prevalence of acanthocephalan eggs than juveniles. In contrast, prevalence of acanthocephalan eggs found in coatis was higher in coati juveniles than in adults. Host age, season and maximum temperature were the top predictors of abundance of acanthocephalan eggs in crab-eating foxes whereas season and host sex were predictors of egg abundance in coatis. The importance of seasonality for abundance of acanthocephalan was clear for both host species. The influence of host-related attributes, however, varied by host species, with host gender and host age being important factors associated with prevalence and parasite loads.

摘要 寄生虫对宿主的感染受多种因素调控，涵盖宿主自身特征与环境因子。本研究以巴西潘塔纳尔湿地的南美浣熊（浣熊科：Nasua nasua）与食蟹狐（犬科：Cerdocyon thous）为研究对象，探究宿主性别、体型、年龄以及季节性对棘头虫（acanthocephalan）感染模式的影响。2006年至2009年间，本研究采集了上述宿主的粪便样本，用于检测棘头虫卵的存在。研究人员计算了棘头虫卵的感染率、感染丰度与感染强度。采用负二项分布的广义线性模型（generalized linear models, GLM）对虫卵丰度开展分析，并通过赤池信息准则比较不同模型的拟合效果，以明确生物与非生物因子的影响效应。两种宿主的棘头虫感染率均在湿季更高，但不同性别宿主的感染率并无显著差异；不过成年食蟹狐的棘头虫卵感染率显著高于幼崽。与之相反，南美浣熊幼崽的棘头虫卵感染率显著高于成年个体。对于食蟹狐而言，宿主年龄、季节与最高气温是影响棘头虫卵丰度的最优预测因子；而对于南美浣熊来说，季节与宿主性别则是虫卵丰度的重要预测因子。两种宿主的棘头虫丰度均明显受季节性调控。不过宿主相关特征的影响效应因宿主物种而异，宿主性别与年龄是与感染率及寄生虫负荷密切相关的重要因素。