Table 5.
Squirrels used in the study of MPXV
| Animal specie | Age | Viral strain | Route of infection/dose | Major findings | Reference |
|---|---|---|---|---|---|
| Squirrel (S. tridecemlineatus) | Adults | MPXV-USA-2003-044 | Intraperitoneal/105,1 and intranasal/106,1 p.f.u/mL | The infection caused severe and fatal disease in all animals in both inoculation routes. High rate of viral load and wide distribution of the virus through the organs. The squirrels were lethargic and anorexic within 4 or 5 days, with death within 9 days. No apparent skin lesions were observed; however, severe liver and spleen lesions were seen in both groups; in addition, necrosis of peribronchial lymphoid tissue and lymph nodes from other sites was also observed in the group challenged by the intranasal route | (Tesh et al.91) |
| a | MPXV-ZAI-1979-005 and MPXV-USA-2003-044 | Subcutaneous/3,7x104 and 1,8x104 p.f.u/mL | Clinical symptoms were earlier and more severe in animals that received strain Z79 and mortality in these animals occurred between days 6 and 11; on the other hand, despite presenting a milder symptomatology, death in animals that received strain US03 occurred in a very similar period. Animals infected with the Z79 virus strain showed consistently higher viral titer in blood and lung tissue compared with those infected with US03 virus alone, but it was also possible to identify virus titers in the spleen and liver of these animals | (Sbrana et al.92) | |
| a | MPXV-ZAI-1979-005 | Subcutaneous/106,3 p.f.u/mL | Infected and untreated animals show signs of disease on day 4 post-infection, and all died between 6 and 9 days post-infection. The animals had a high viral load; however, none of the challenged and treated squirrels developed detectable viremia | (Sbrana et al.93) | |
| Squirrel (Marmota bobak) | 1–2-year-old | MPXV-ZAI-1979-005 | Subcutaneous/2.6, 4.1, 5.6, 7.1 log10 p.f.u/mL and intranasal/1.8, 0.2, 2.2, 3.7, 4.2, 5.0, 6.6 and 7.8 log10 p.f.u/mL | Virus was recovered from nasal mucosa, oropharyngeal lymph nodes, and spleen in animals challenged by MPXV Congo Basin (CB) on day 4 and in animals challenged with the West African (WA) strain on day 6. For both groups, viremia primary was seen from days 6–9 through day 17. Although the histopathology and immunohistochemistry findings were similar, CB MPXV spread faster and accumulated to higher levels, causing greater morbidity in animals when compared to WA MPXV. Two animals that succumbed to the disease showed abundant viral antigen in all organs tested, except the brain. Interestingly, splenocytes were labeled positive for apoptosis more often than hepatocytes in both MPXV groups | (Sergeev et al.94) |
| Squirrel (Funisciurus anerythrus) | a | Congo Basin MPXV/Luc+ | Intranasal and intradermal/106 p.f.u/mL | MPXV infection in these animals caused moderate to severe morbidity and mortality, with clinical signs including smallpox lesions on the skin, eyes, mouth, and nose, dyspnea, and profuse nasal discharge. Both intranasal and intradermal exposures induced high levels of viremia, rapid systemic spread, and long periods of viral shedding. The sentinel animal showed clinical signs of infection including increased respiratory rate, nasal discharge and mouth lesions, respiratory problems, weight loss, and severe lethargy | (Falendysz et al.95) |
a
Not reported; p.f.u: plaque formation unit; mL: milliliter; MPXV: Monkeypox virus.