Laboratory animals are essential mainly for experiments aiming to study pathogenesis and evaluate antivirals and vaccines against emerging human infectious diseases. Preclinical studies of coronavirus disease 19 (COVID-19) pathogenesis have used several animal species as models: transgenic human ACE2 mice (K18 mice), inbred BALB/c or C57BL/6N mice, ferrets, minks, domestic cats and dogs, hamsters, and macaques. However, the choice of an animal model relies on several limitations. Besides the host susceptibility, the researcher’s experience with animal model management and the correct interpretation of clinical and laboratory records are crucial to succeed in preclinical translational research. Here, we summarise pathological and clinical findings correlated with virological data and immunological changes observed from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) experimental infections using different well-established SARS-CoV-2 animal model species. This essay aims to critically evaluate the current state of animal model translation to clinical data, as described in the human SARS-CoV-2 infection.

This study was conducted to analyse the course and the outcome of the liver disease in the co-infected animals in order to evaluate a possible synergic effect of human parvovirus B19 (B19V) and hepatitis A virus (HAV) co-infection. Nine adult cynomolgus monkeys were inoculated with serum obtained from a fatal case of B19V infection and/or a faecal suspension of acute HAV. The presence of specific antibodies to HAV and B19V, liver enzyme levels, viraemia, haematological changes, and necroinflammatory liver lesions were used for monitoring the infections. Seroconversion was confirmed in all infected groups. A similar pattern of B19V infection to human disease was observed, which was characterised by high and persistent viraemia in association with reticulocytopenia and mild to moderate anaemia during the period of investigation (59 days). Additionally, the intranuclear inclusion bodies were observed in pro-erythroblast cell from an infected cynomolgus and B19V Ag in hepatocytes. The erythroid hypoplasia and decrease in lymphocyte counts were more evident in the co-infected group. The present results demonstrated, for the first time, the susceptibility of cynomolgus to B19V infection, but it did not show a worsening of liver histopathology in the co-infected group.

Achados de necropsia em três casos de toxoplasmose ocorridos naturalmente em macacos-de-cheiro (Saimiri sciureus) obtidos de capturas na região Amazônica foram descritos. A avaliação histopatológica do fígado, baço, rins e linfonodos mesentéricos mostrou múltiplos focos de inflamação e necrose. Cistos morfológicos típicos e bem definidos de Toxoplasma gondii e formas livres foram detectados pelo método da imunoperoxidase com infiltrados inflamatórios. A presença de T. gondii na colônia de primatas estudada pode influenciar severamente os resultados de experimentos realizados nos animais.

Necropsy findings in three cases of naturally occurring toxoplasmosis in squirrel monkeys (Saimiri sciureus) obtained as wild catches from the Amazon region were described. Histopathological evaluation of the liver, spleen, kidneys and mesenteric lymph nodes showed multiple foci of inflammation and necrosis. Typical, well-defined morphologic Toxoplasma gondii cysts and free forms of the parasite were found by immunoperoxidase staining within inflammatory infiltrates. The presence of T. gondii in the studied colony could severely influence the results of experiments performed in the animals.