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From 2016 to 2018, an epidemic wave of yellow fever (YF) occurred in Brazil, affecting a large number of Platyrrhini monkeys. Titi monkeys (Callicebus spp.) were severely affected yet pathological characterizations are lacking. This study characterized epizootic YF in 43 titi monkeys (Callicebus spp.) with respect to the microscopic lesions in liver, kidney, spleen, heart, brain, and lung, as well as the distribution of immunolabeling for YF virus antigen, and the flaviviral load in the liver. Of 43 titi monkeys examined, 18 (42%) were positive for yellow fever virus (YFV) by immunohistochemistry or reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). Affected livers had consistent marked panlobular necrotizing hepatitis, lipidosis, and mild inflammation, with intense immunolabeling for YFV mainly in centrilobular hepatocytes (zone 1; P =.05). In the spleen, consistent findings were variable lymphoid depletion (10/11), lymphoid necrosis (lymphocytolysis; 4/11), and immunolabeling for YFV in histiocytic cells (3/16). The main finding in the kidney was multifocal acute necrosis of tubular epithelium (5/7) that was occasionally associated with intracytoplasmic immunolabeling for YFV (6/15). These data indicate that titi monkeys are susceptible to YFV infection, developing severe hepatic lesions and high viral loads, comparable to humans and Alouatta spp. Thus, Callicebus spp. may be reliable sentinels for YF surveillance. [ABSTRACT FROM AUTHOR]

A major outbreak of yellow fever (YF) occurred in Brazil during 2016-2018. Epizootics in New World nonhuman primates are sentinel events for YF virus circulation. However, genus-specific susceptibilities and suitability for YF surveillance remain poorly understood. We obtained and compared epidemiologic, histopathologic, immunohistochemical, and molecular results from 93 human and 1,752 primate cases submitted during the recent YF outbreak in Brazil (2017), with the support of the Brazilian National YF Surveillance Program. We detected heterogeneous YF-associated profiles among the various genera of primates we analyzed. Alouatta primates were the most reliable sentinel; Sapajus and Callicebus primates had higher viral loads but lower proportional mortality rates. Callithrix primates were the least sensitive, showing lower viral loads, lower proportional mortality rates, and no demonstrable YF virus antigen or extensive lesions in liver, despite detectable viral RNA. These differences in susceptibility, viral load, and mortality rates should be considered in strategic surveillance of epizootics and control measures for YF. [ABSTRACT FROM AUTHOR]

Aims: The clinical spectrum of yellow fever (YF) ranges from asymptomatic to fulminant hepatitis. During the sylvatic YF epidemic in the metropolitan area of São Paulo, Brazil in 2018, seven orthotopic liver transplantations (OLTs) were performed in our institution to treat fulminant YF hepatitis. Three patients recovered, while four patients died following OLT. The autopsy findings of all these cases are presented herein as the first description of YF in transplanted patients. Methods and results: All patients were men, aged 16–40 years, without vaccination to YF virus (YFV). All organs were examined, with tissue sampling for histopathological analysis. Detection of YF virus antigens (YFV Ag) was performed with two primary antibodies (mouse polyclonal anti‐YFV antibody directed to wild strain and a goat anti‐YF virus antibody), and RT–PCR assays were utilised to detect YFV‐RNA. All the cases depicted typical findings of YF hepatitis in the engrafted liver. The main extrahepatic findings were cerebral oedema, pulmonary haemorrhage, pneumonia, acute tubular necrosis and ischaemic/reperfusion pancreatitis. Of the four cases, the YVF Ag was detected in the heart in one case, liver and testis in three cases, and the kidney and spleen in all four cases. All four cases had YF virus RNA detected by RT–PCR in the liver and in other organs. Conclusions: Infection of the engrafted liver and other organs by YFV, possibly combined with major ischaemic systemic lesions, may have led to the death of four of the seven patients undergoing OLT. [ABSTRACT FROM AUTHOR]