Key result
H7N1 HPAIV drives ~49% higher mortality than H5N8 in chickens with shorter mean death times.
Why the study?
Chickens are highly susceptible to highly pathogenic avian influenza viruses, but the severity of infection varies depending on the viral strain and the host genetic background.
Absolute Event Rate: 70% vs 47%
The severity of highly pathogenic avian influenza infection in chickens depends on both the viral isolate and host genetic factors like the Mx 2032 polymorphism.
Breed variation modulates HPAIV mortality in Spanish chickens; leaves open selective breeding approaches pending prospective validation.
Chickens are highly susceptible to highly pathogenic avian influenza viruses (HPAIVs). However, the severity of infection varies depending of the viral strain and the genetic background of the host. In this study, we evaluated the pathogenesis of two HPAIVs (H7N1 and H5N8) and assessed the susceptibility to the infection of local and commercial chicken breeds from Spain. Eight chicken breeds were intranasally inoculated with 105 ELD50 of A/Chicken/Italy/5093/1999 (H7N1) or A/Goose/Spain/IA17CR02699/2017 (H5N8 clade 2.3.4.4. B) and monitored during 10 days. Chickens were highly susceptible to both HPAIVs, but H7N1 was considerably more virulent than H5N8 as demonstrated by the highest mortality rates and shortest mean death times (MDT). Both HPAIVs produced severe necrosis and intense viral replication in the central nervous system, heart and pancreas; however, the lesions and replication in other tissues were virus-dependent. High levels of viral RNA were detected by the oral route with both viruses. In contrast, a low number of H5N8-inoculated chickens shed by the cloacal route, demonstrating a different pattern of viral shedding dependent of the HPAIV. We found a high variation in the susceptibility to HPAIVs between the different chicken breeds. The birds carrying the genotype AA and AG at position 2032 in chicken Mx gene presented a slightly higher, but not significant, percentage of survival and a statistically significant longer MDT than GG individuals. Our study demonstrated that the severity of HPAI infection is largely dependent of the viral isolate and host factors, underlining the complexity of HPAI infections.
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Sánchez-González et al. (2020) studied Highly pathogenic avian influenza (HPAI). H7N1 HPAIV vs. H5N8 HPAIV was evaluated on Mortality rate. H7N1 HPAIV was considerably more virulent to chickens than H5N8 HPAIV, resulting in higher mortality rates (70% vs 47%) and shorter mean death times (3.3 vs 4.9 days).
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