Situation of and phenotypic markers of susceptibility to helminth infection among sheep on farms in the Brazilian cerrado biome

Abstract This study aimed to determine the intensity, seasonality, and distribution by genera of, as well as to identify phenotypic markers of susceptibility to, gastrointestinal parasites among sheep on farms within the Brazilian savanna (cerrado) biome. We evaluated 1271 sheep, on seven farms, during the rainy season (in December 2017 and December 2018) and dry season (in July 2018 and July 2019). Parasitological evaluation was based on culture and EPG. We calculated hematocrit, as well as the body condition score and feces score. Of the sheep evaluated, 34.15% had moderate-to-severe parasitic infection. The factors of herds’ phenotypic characterization about helminth infections were (p ≤ 0.05 for all): anemia (OR = 5.72); leanness (OR = 1.80); loose stools or diarrhea (OR = 1.54); breed other than Santa Inês (OR = 2.31); “weaned lamb” category (OR = 4.76); “lambing ewe” category (OR = 4.66); and dry season (OR = 2.37). Haemonchus, Trichostrongylus, Oesophagostomum, and Cooperia accounted for 76.40%, 20.23%, 2.89%, and 0.47%, respectively, of the helminth genera identified, with their proportional distributions being comparable between the rainy and dry seasons. Changes in health management, with regard to helminth infection control, are urgently needed in order to combat the disease more effectively and sustainably.

摘要 本研究旨在明确巴西塞拉多（Cerrado）热带草原生物群区内农场养殖绵羊的胃肠道寄生虫感染强度、季节动态及属水平分布特征，并鉴定其易感表型标记物。本研究于2017年12月、2018年12月（雨季）以及2018年7月、2019年7月（旱季）对7个农场的1271只绵羊开展调查评估。寄生虫学检测采用培养法与每克粪便虫卵数（Eggs Per Gram，EPG）计数法；同时检测了红细胞比容、体况评分与粪便评分。在所评估的绵羊中，34.15%存在中重度寄生虫感染。与绵羊蠕虫感染相关的表型危险因素（所有因素P值均≤0.05）包括：贫血（比值比（Odds Ratio，OR）=5.72）、体况偏瘦（OR=1.80）、粪便松散或腹泻（OR=1.54）、非圣塔伊内斯（Santa Inês）品种（OR=2.31）、断奶羔羊群体（OR=4.76）、待产母羊群体（OR=4.66）以及旱季（OR=2.37）。在所鉴定出的蠕虫属中，血矛线虫属（Haemonchus）、毛圆线虫属（Trichostrongylus）、食道口线虫属（Oesophagostomum）与古柏线虫属（Cooperia）占比分别为76.40%、20.23%、2.89%与0.47%，且雨季与旱季的属分布比例无显著差异。当前亟需优化蠕虫感染防控相关的健康管理策略，以更高效且可持续地应对该寄生虫病。