Genetics of nematode resistance in pasture-raised Central Anatolian Merino lambs

Abstract

Gastrointestinal nematode infections are among the most economically significant health challenges in small ruminant production, particularly under extensive management systems. The genetic basis of host resistance offers a sustainable alternative to chemical control, which is increasingly limited due to rising anthelmintic resistance. In this study, we conducted a genome-wide association analysis (GWAS) to identify genomic regions associated with faecal egg count (FEC) as a proxy for nematode burden in 226 Central Anatolian Merino lambs raised on pasture. FEC exhibited moderate genomic heritability (h² = 0.22 ± 0.04), supporting the potential for genetic improvement. GWAS identified two SNPs that exceeded the genome-wide significance threshold and five additional loci at the chromosome-wide level. Notably, candidate genes including PLCL1, TCF7L2, ADRB1, GRIP1, VAC14, and TXNDC16 were located near significant SNPs. These genes are involved in immune signalling, epithelial barrier function, and redox regulation—mechanisms essential for helminth defence. Several regions overlapped with those previously reported for resistance to Eimeria and Moniezia spp., suggesting shared genetic pathways for gastrointestinal parasite resistance. These findings contribute to the understanding of the genetic architecture of nematode resistance and provide a foundation for the development of genomic selection strategies in native sheep breeds.

Keywords

• Gastrointestinal nematodes
• Fecal egg count
• Genetic resistance
• Central Anatolian Merino sheep

Merada yetiştirilen Orta Anadolu Merinosu kuzularında nematod direncinin genetiği

Öz

Gastrointestinal nematod enfeksiyonları, özellikle ekstansif yetiştiricilik sistemlerinde küçükbaş hayvancılığın karşılaştığı en önemli ekonomik sağlık sorunlarından biridir. Konak hayvanın direnç mekanizmasının genetik temeli, artan antihelmintik direnci nedeniyle giderek sınırlanan kimyasal kontrol yöntemlerine karşı sürdürülebilir bir alternatif sunmaktadır. Bu çalışmada, merada yetiştirilen 226 Orta Anadolu Merinosu kuzusunda nematod yükünün göstergesi olarak kullanılan dışkı yumurta sayısı (FEC) ile ilişkili genomik bölgeleri belirlemek amacıyla bir genom çapında ilişkilendirme analizi (GWAS) gerçekleştirilmiştir. FEC için hesaplanan genomik kalıtım derecesi orta düzeyde bulunmuştur (h² = 0.22 ± 0.04) ve bu durum, genetik iyileştirme potansiyelini desteklemektedir. GWAS sonucunda, iki SNP genom çapında anlamlılık eşiğini aşarken, beş ek bölge kromozom çapında anlamlı bulunmuştur. Anlamlı SNP'lerin yakınında bulunan aday genler arasında PLCL1, TCF7L2, ADRB1, GRIP1, VAC14 ve TXNDC16 yer almakta olup, bu genler bağışıklık sinyal iletimi, epitel bariyer fonksiyonu ve redoks düzenlemesi gibi helmint savunmasında temel rol oynayan mekanizmalarla ilişkilidir. Ayrıca, bazı genomik bölgeler daha önce Eimeria ve Moniezia spp. direnç çalışmalarıyla da örtüşmektedir; bu durum, gastrointestinal parazit direnci için ortak genetik yolların varlığını düşündürmektedir. Elde edilen bulgular, nematod direncinin genetik yapısını daha iyi anlamamıza katkı sağlamakta ve yerli koyun ırklarında genomik seleksiyon stratejilerinin geliştirilmesi için sağlam bir temel oluşturmaktadır.

Anahtar Kelimeler

• Gastrointestinal nematodes
• Fecal egg count
• Genetic resistance
• Central Anatolian Merino sheep

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