The natural transmission cycle of Yellow Fever (YF) involves tree hole breeding mosquitoes and a wide array of nonhuman primates (NHP), including monkeys and apes. Some Neotropical monkeys (howler monkeys, genus Alouatta) develop fatal YF virus (YFV) infections similar to those reported in humans, even with minimum exposure to the infection. Epizootics in wild primates may be indicating YFV circulation, and the surveillance of such outbreaks in wildlife is an important tool to help prevent human infection. In 2001, surveillance activities successfully identified YF-related death in a black-and-gold howler monkey (Alouatta caraya), Rio Grande do Sul State (RGS) in southern Brazil, and the YFV was isolated from a species of forest-dwelling mosquito (Haemagogus leucocelaenus). These findings led the State Secretariat of Health to initiate a monitoring program for YF and other 18 arboviral infections in Alouatta monkeys. The monitoring program included monkey captures, reporting of monkey casualties by municipalities, and subsequent investigations. If monkey carcasses were found in forests, samples were collected in a standardized manner and this practice resulted in increased reporting of outbreaks. In October 2008, a single howler monkey in a northwestern RGS municipality was confirmed to have died from YF. From October 2008 to June 2009, 2,013 monkey deaths were reported (830 A. caraya and 1,183 A. guariba clamitans). Viruses isolation in blood, viscera, and/or immunohistochemistry led to the detection of YF in 204 of 297 (69%) (154 A. g. clamitans and 50 A. caraya) dead Alouatta monkeys tested. The number of municipalities with confirmed YFV circulation in howlers increased from 2 to 67 and 21 confirmed human cases occurred. This surveillance system was successful in identifying the largest YF outbreak affecting wild NHP ever recorded.

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.

RESUMO.-[Infecção fatal por Herpesvirus simplex Tipo 1 (HHV-1) em saguis de cativeiro (Callithrix jacchus and Callithrix penicillata) no Brasil: caracterização clínica e patológica.] Infecção fatal por Herpesvirus simplex Tipo 1 (HHV-1) foi diagnosticada em 12 saguis de cativeiro (Callithrix jacchus e Callithrix penicillata) provenientes da região metropolitana de São Paulo, Estado de São Paulo. Os sinais clínicos foram variáveis entres os casos, no entanto, a maioria dos saguis afetados apresentavam sinais associados à replicação viral em epitélios: úlceras na cavidade oral, lín-gua e pele da face e hipersalivação; e no sistema nervoso central: prostração, convulsão e comportamento agressivo. Histologicamente, o principal achado foi meningoencefalite necrosante não supurativa difusa, leve a acentuada com gliose, vasculite e necrose neuronal. Inclusões intranucleares também foram observadas em encéfalo, cavidade oral, pele, glândula adrenal e plexo mioentérico. A imuno-histoquímica anti-HHV-1 confirmou a presença do antígeno viral em associação às lesões em encéfalo, mucosa oral e lingual, pele da face, glândula adrenal e plexo mioentéri-co. Em 7/8 saguis infectados foi detectada a presença de HHV-1 por reação em cadeia da polimerase (PCR) a partir de amostras de encéfalo. Conclui-se que HHV-1 causa uma infecção disseminada e fatal em saguis. Clinical signs were variable among the cases, but most affected marmosets presented signs associated with viral epithelial replication: oral, lingual and facial skin ulcers and hypersalivation, and viral replication in the central nervous system: prostration, seizure and aggressive behavior. Consistent microscopic findings were diffuse mild to severe nonsuppurative necrotizing meningoencephalitis with gliosis, vasculitis and neuronal necrosis. Additionally, in the brain, oral cavity, skin, adrenal gland and myoenteric plexus intranuclear inclusion bodies were present. Immunohistochemistry confirmed the presence of the HHV-1 antigen in association with lesions in the brain, oral and lingual mucosa, facial skin, adrenal gland and myoenteric plexus. HHV-1-specific polymerase chain reaction (PCR) analysis of the brain was carried out and the virus was detected in 7/8 infected marmosets. It is concluded that HHV-1 causes widespread fatal infection in marmosets.

A morphological evaluation of histopathological liver samples from 42 fulminant hepatic failure cases from the Amazon Basin was undertaken in order to differentiate yellow fever (YF) from Lábrea hepatitis (LH) and other entities. The pattern and distribution of liver cell death as well as ballooning degeneration and midzonal apoptotic bodies were the most distinctive features of YF, whereas morula cells were the major finding for LH. Nineteen well characterised cases were further submitted to immunohistochemical studies for expression of YF antigen, hepatitis B surface antigen (HBsAg) and delta virus antigen. In both diseases, but particularly in LH, portal vein branch phlebitis was evident and might have played a role in the pathogenesis of hepatic injury, leading to hepatic extinction and portal tract approximation. The regeneration pattern was remarkable: a high proliferative index was detected in YF, whereas in LH multinucleation and pseudoacinar transformation, associated with portal type I collagen deposition and portal elastic fibre proliferation, was seen. In conclusion, midzonal apoptosis, portal phlebitis and a high proliferative index in patients without evidence of previous liver injury was the dominant picture in YF. On the other hand, LH cases showed extensive, predominantly lytic hepatocytic necrosis, portal and hepatic vein phlebitis and morula cells in patients with a morphological background of chronic liver disease.

No abstract