Table 1.

Comparison of the ferret and Golden Syrian hamster models.

	Ferret (Mustela putorius furo)	Golden Syrian hamster (Mesocricetus auratus)
Age	15–19 weeks	5 weeks (‘young’)	>20 weeks (‘older’)
Infection Dose	1 × 106 PFU in 200 μL (‘high’) and 1 × 102 PFU in 200 μL (‘low’)	1 × 106 PFU in 200 μL
Weight loss	Yes, average peak – 6 dpi	Yes, average peak – 5 dpi (young) or 7 dpi (older)
Clinical signs	Nasal rattles/sneezing, nasal discharge, laboured breathing, diarrhoea, reduced activity. No differences observed between doses.	None
Temperature	Fever peak at ~35–45 hpi, depending on dose.	Temperature drop observed following infection as well as disruption to diurnal rhythm. Differences observed between male and female hamsters—male hamster temperatures fell significantly following infection.
Shedding of live virus from the URT	Yes, peak observed at 1–2 dpi depending on dose, shedding was detectable until 8 dpi.	Yes, peak observed mainly at 1 dpi; shedding detected until 5 dpi. Differences observed between male and female hamsters at 1 dpi—male hamsters shedding significantly more live virus.
Viral load in LRT	Live virus detected in lung at 4 dpi. Virus only detected in one (high dose) animal at 14 dpi.	Live virus detected in lung of 2/12 (male) at 4 dpi. Assay failure suspected. Method requires further optimisation.
Pathology	No differences observed in % lesions in the lung. No significant differences observed in assigned ‘Morgan score’ [9] at 4 or 14 dpi. Viral NP staining was detectable at 4 dpi in the NT and lung.	No differences observed in % lesions in the lung. ‘Young’ hamsters were assigned a significantly higher ‘Morgan score’ [9] at 4 dpi. Viral NP staining was detectable at 4 dpi in the NT and lung.
Humoral Response	Seroconversion detected by HAI and NAI at 7 dpi. No difference between dose observed in HAI and NAI titres.	Seroconversion detected by HAI and NAI at 14 dpi. No differences between ages observed in HAI titres. Young hamsters had significantly higher NAI titres at 14 dpi.
Cellular Response	Peak of response in PBMCs observed at 7 dpi (high dose) or 11 dpi (low dose). Higher influenza-specific IFNγ responses observed in the lung of high-dose ferrets when compared to low-dose ferrets. NP-specific IFNγ responses were highest in both compartments measured.	No differences observed between ‘young’ and ‘older’ hamsters in amount of CD4+ cells in peripheral blood following infection. No differences in influenza-specific IFNγ responses observed between ‘young’ or ‘older’ hamsters. In general, higher responses were observed at 14 dpi when compared to 4 dpi. NP-specific IFNγ responses were highest in all compartments measured.