Weather, host and vector--their interplay in the spread of insect-borne animal virus diseases

[Serological studies for research on arbovirus antibodies in a human population of the Vale do Ribeira region. III. Survey in inhabitants with cases of Flavivirus Rocio encephalitis]

Foi realizado inquérito sorológico para pesquisa de anticorpos de 17 arbovírus existentes no país, em coabitantes com doentes de encefalite por Rocio, residentes em zona urbana da região do Vale do Ribeira, São Paulo (Brasil), onde ocorreu recentemente uma extensa epidemia dessa moléstia. Não se verificou maior prevalência de anticorpos IH para vírus Rocio nessas pessoas quando comparadas com indivíduos que não coabitavam com doentes de encefalite. Foram observados e discutidos alguns aspectos já verificados em outros grupos populacionais estudados anteriormente: maior prevalência de anticorpos IH de arbovírus em homens, particularmente pescadores; aumento dessa prevalência com a idade e presença de pessoa com antecedente de encefalite que apresentou, exclusivamente anticorpos neutralizantes para o Alphavirus EEL, o qual até agora não tem sido responsabilizado por moléstia na região. Encontrou-se baixa proporção de indivíduos com anticorpos para Rocio e Flavivirus em geral, fato este estranhável considerando a recente epidemia.

The spread of Rift Valley fever and approaches to its control

Rift Valley fever (RVF) is primarily a disease of sheep, cattle, other domestic animals, and man; it was believed to be relatively benign for man until 1977 when it spread to Egypt. There it caused enormous losses of sheep and cattle, and thousands of human cases occurred, with nearly 600 reported deaths. Although mosquitos are known to transmit RVF virus in epizootics and epidemics, the reservoir and means of inter-epizootic maintenance are not known. RVF epizootics can be recognized by a combination of observations: abortions and neonatal death in sheep and cattle at times when mosquitos are abundant, accompanied by cases of fever in man, which are complicated in a minority of patients by haemorrhagic fever, encephalitis, and retinitis with blindness. Vaccination of livestock with available killed or live attenuated vaccines should prevent transmission to both human subjects and animals. Although routine quarantine of animals is not deemed a practical measure, movement of animals should be restricted when an epizootic is in progress. Since it is possible that RVF may spread from Africa in the future, serological surveillance in man and animals is recommended in potentially receptive countries of the Mediterranean Basin and South-West Asia to establish baseline data and to familiarize staff with the methods of RVF diagnosis.