Tissue-specific transcriptomic adaptation in three strains of chickens during coinfections with parasites

The widespread adoption of non-caged production systems contributes to the pathogenesis of coinfections with gastrointestinal nematodes and Histomonas meleagridis, triggering local and systemic immune and metabolic responses in chickens. This study investigated transcriptomic adaptation of tissues two weeks after experimental coinfections with Ascaridia galli, Heterakis gallinarum, and H. meleagridis in Lohmann Brown (LB), Lohmann Dual (LD), and Ross-308 (R) male chickens, which differ in growth rates (R > LD > LB).

RNA sequencing of the jejunum, caecum, and liver tissues revealed tissue-specific, strain-dependent transcriptional responses. Coinfection was confirmed during necropsy, and Ascaris-specific antibodies as well as alpha-1-acid glycoprotein were significantly higher in infected birds (p < 0.01). The caecum exhibited the highest unique differentially expressed genes, DEGs (n = 4,094), corresponding to significant activation of complex immune pathways and inhibition of metabolic pathways (p < 0.01). Jejunum DEGs (n = 760) primarily related to muscle contraction, collagen metabolism notably in LB and LD strains. The liver displayed fewer unique DEGs (n = 266) but prominently activated immune responses, especially in R chickens.

In general, slower-performing strains effectively initiated responses favouring worm expulsion and tissue repair in the jejunum, whereas high-performing strains predominantly showed inflammatory responses in the caecum and liver. These findings highlight tissue-specific adaptations underlying strain-dependent tolerance to coinfections with mixed parasites.