Section for Parasitology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. 7028, Uppsala SE-750 07, Sweden.
Parasit Vectors. 2012 May 20;5:97. doi: 10.1186/1756-3305-5-97.
The poultry roundworm Ascaridia galli has reappeared in hens kept for egg production in Sweden after having been almost absent a decade ago. Today this is a frequent intestinal nematode parasite in non-caged laying hens. The aim of this study was to investigate the genetic diversity (Fst) in A. galli collected from different poultry production sites in southern Sweden, to identify possible common routes of colonization.
Adult parasites (n = 153) from 10 farms, including both broiler breeder parents and laying hens, were investigated by amplified restriction fragment length polymorphism analysis (AFLP). Worms from a Danish laying hen farm were also included for comparison. Most of the farms were represented by worms from a single host, but on two farms multiple samples from different hosts were assessed in order to study flock variation.
A total of 97 fragments (loci) were amplified among which 81% were variable alleles. The average genetic diversity was 0.13 (range = 0.09-0.38), which is comparable to other AFLP studies on nematodes of human and veterinary importance. Within-farm variation showed that worms harboured by a single hen in a flock covered most of the A. galli genetic variation within the same flock (Fst = 0.01 and 0.03 for two farms). Between-farm analysis showed a moderate population genetic structure (Fst = 0.13), along with a low mutational rate but high gene flow between different farms, and absence of strong genetic selection. Network analysis showed repeated genetic patterns among the farms, with most worms on each farm clustering together as supported by high re-allocation rates.
The investigated A. galli populations were not strongly differentiated, indicating that they have undergone a genetic bottlenecking and subsequent drift. This supports the view that the investigated farms have been recently colonized, and that new flocks are reinfected upon arrival with a stationary infection.
在几乎绝迹十年后，家禽蛔虫鸡蛔虫又重新出现在瑞典产蛋鸡中。如今，这种寄生虫在非笼养产蛋母鸡中很常见。本研究旨在调查瑞典南部不同家禽养殖场采集的鸡蛔虫的遗传多样性（Fst），以确定可能的定植途径。
采用扩增限制性片段长度多态性分析（AFLP）对来自 10 个农场的 153 只成年寄生虫（包括肉鸡种鸡父母代和产蛋母鸡）进行了研究。丹麦一个产蛋鸡场的蠕虫也被包括在内进行比较。大多数农场都有单一宿主的蠕虫代表，但在两个农场中，对不同宿主的多个样本进行了评估，以研究群体变化。
共扩增出 97 个片段（基因座），其中 81%为可变等位基因。平均遗传多样性为 0.13（范围为 0.09-0.38），与其他有关人类和兽医重要性的线虫的 AFLP 研究相当。农场内的变异表明，在一个群体中，一只母鸡身上的蠕虫涵盖了同一群体内的大部分鸡蛔虫遗传变异（两个农场的 Fst 值分别为 0.01 和 0.03）。农场间分析显示，种群遗传结构中等（Fst 值为 0.13），突变率低，但不同农场间基因流高，不存在强烈的遗传选择。网络分析显示，农场间存在重复的遗传模式，每个农场的大多数蠕虫都聚集在一起，重新分配率很高。
研究的鸡蛔虫种群没有明显分化，表明它们经历了遗传瓶颈和随后的漂变。这支持了这样一种观点，即研究农场最近才被定植，新的群体在到达时会重新感染，导致感染固定。
