Dosage comparison of Congo Basin and West African strains of monkeypox virus using a prairie dog animal model of systemic orthopoxvirus disease

The prairie dog is valuable for the study of monkeypox virus (MPXV) virulence and closely resembles human systemic orthopoxvirus disease. Herein, we utilize a variable dose intranasal challenge with approximately 103, 104, 105, and 106PFU for each clade to further characterize virulence differences between the two MPXV clades. A trend of increased morbidity and mortality as well as greater viral shedding was observed with increasing viral challenge dose. Additionally, there appeared to be a delay in onset of disease for animals challenged with lower dosages of virus. Mathematical calculations were used to determine LD50 values and based on these calculations, Congo Basin MPXV had approximately a hundred times lower LD50 value than the West African clade (5.9×103 and 1.29×105 respectively); reinforcing previous findings that Congo Basin MPXV is more virulent.