SEROLOGIC SURVEY OF VIRAL AND RICKETTSIAL DISEASES AMONG JUNGLE INHABITANTS OF THE UPPER AMAZON BASIN
Authors: Gajdusek D. Carleton , Rogers Nancy G. , Bankhead Annie S. 
Published: December 2021

In order to extend our knowledge of the prevalence of viral and rickettsial infections among people living in remote areas of the Western Hemisphere, sera have been examined from children and adults dwelling under primitive conditions in jungle communities of the upper Amazon Drainage area of Peru and Bolivia for neutralizing antibodies to the three types of poliomyelitis, to viruses of yellow fever and encephalomyocarditis; for complementfixing antibodies to mumps, herpes simplex, and the PLV group of viruses, Q fever, and epidemic and murine typhus; and for hemagglutination-inhibiting antibodies to arthropod-borne viruses of Casals' Group B.

By 4 years of age all but a very few children in both countries have had contact with all three types of poliomyelitis virus and are presumably immune to subsequent infection, as evidenced by the presence of significant amounts of neutralizing antibodies to all three types of virus. Similar findings from equivalent socio-economic groups have been reported from many parts of the globe. The data suggest that in recent years Type 1 virus has been more extensively disseminated in the Bolivian than in the Peruvian community while the reverse is true of Type 3 virus.

No antibody-neutralizing yellow fever virus was found in sera from 87 children and adolescents of Peru and Bolivia. Yellow fever has occurred infrequently in Peru in the last decade. However, during this same period, a few cases have been recorded in the neighborhood of Santa Cruz, Bolivia, and in 1950 a severe outbreak occurred in southern Bolivia in an area where no yellow fever had been recorded during an observation period of 18 years. Thus, the negative findings on this small sampling of Bolivian sera may not be representative of the region as a whole.

Six individuals possessed serum which inhibited agglutination with a representative of Casals' Group B to titer of 1:20 or greater. These were equally distributed between Peru and Bolivia. These data indicate that an agent related to Group B may be present in these areas but contact does not seem to be extensive. The tests do not permit identification of this agent.

No antibody-neutralizing virus of encephalomyocarditis was found in any of 25 sera of adults.

Complement-fixing antibodies against both mumps and herpes simplex were already present in sera of some children less than 5 years of age and by puberty over half of the children had such antibodies, while about 90% of adults had antibodies to these viruses. These findings are comparable to those reported in a survey of indigenous inhabitants of northwestern Mexico and undoubtedly reflect a similarity of these groups in terms of personal hygiene and sanitation. In Peruvian communities complement-fixing antibodies to the PLV group were found only in subjects more than 15 years of age, a finding which suggests the possibility that lymphogranuloma venereum virus is responsible for these immune substances, rather than the members of the psittacosis group causing enzootic disease of birds and mammals.

Q fever antibody in low titer was found in 10 children and 6 adults from these two tropical jungle communities, and its presence is evidence for the occurrence of infection with rickettsiae causing Q fever, or an unknown agent sharing its complementfixing antigen, in these regions. Q fever in infancy and childhood is common in many primitive communities.

The presence of low titer of antibodies to epidemic or murine typhus in only two sera suggests that, although louse-borne typhus often occurs in outbreaks in the Andean Highlands, epidemic and murine typhus have been rare or absent in the tropical lowlands of the Amazon Basin.

The significance of these findings and their relation to the cultural pattern found in the communities of the Upper Amazon Basin can only be surmised on the basis of the data presented. Additional serologic investigations are needed in order to gain more definitive information about the presence, prevalence and age incidence of human infections with specific viral and rickettsial agents in the areas in question.