Vertebrate Reservoirs of Arboviruses : Myth, Synonym of Amplifier, or Reality?

The rapid succession of the pandemic of arbovirus diseases, such as dengue, West Nile fever, chikungunya, and Zika fever, has intensified research on these and other arbovirus diseases worldwide. Investigating the unique mode of vector-borne transmission requires a clear understanding of the roles of vertebrates. One major obstacle to this understanding is the ambiguity of the arbovirus definition originally established by the World Health Organization. The paucity of pertinent information on arbovirus transmission at the time contributed to the notion that vertebrates played the role of reservoir in the arbovirus transmission cycle. Because this notion is a salient feature of the arbovirus definition, it is important to reexamine its validity. This review addresses controversial issues concerning vertebrate reservoirs and their role in arbovirus persistence in nature, examines the genesis of the problem from a historical perspective, discusses various unresolved issues from multiple points of view, assesses the present status of the notion in light of current knowledge, and provides options for a solution to resolve the issue.Peer reviewe

Contrasting the Practices of Virus Isolation and Characterization between the Early Period in History and Modern Times: The Case of Japanese Encephalitis Virus

Japanese encephalitis is a serious disease transmitted by mosquitoes. With its recent spread beyond the traditional territory of endemicity in Asia, the magnitude of global threat has increased sharply. While much of the current research are largely focused on changing epidemiology, molecular genetics of virus, and vaccination, little attention has been paid to the early history of virus isolation and phenotypic characterization of this virus. In this review, using this piece of history as an example, I review the transition of the concept and practice of virus isolation and characterization from the early period of history to modern times. The spectacular development of molecular techniques in modern times has brought many changes in practices as well as enormous amount of new knowledge. However, many aspects of virus characterization, in particular, transmission mechanism and host relationship, remain unsolved. As molecular techniques are not perfect in all respects, beneficial accommodation of molecular and biologic data is critically important in many branches of research. Accordingly, I emphasize exercising caution in applying only these modern techniques, point out unrecognized communication problems, and stress that JE research history is a rich source of interesting works still valuable even today and waiting to be discovered

A Re-Examination of the History of Etiologic Confusion between Dengue and Chikungunya.

Contrary to the perception of many researchers that the recent invasion of chikungunya (CHIK) in the Western Hemisphere marked the first episode in history, a recent publication reminded them that CHIK had prevailed in the West Indies and southern regions of the United States from 1827-1828 under the guise of "dengue" (DEN), and that many old outbreaks of so-called "dengue" actually represented the CHIK cases erroneously identified as "dengue." In hindsight, this confusion was unavoidable, given that the syndromes of the two diseases-transmitted by the same mosquito vector in urban areas-are very similar, and that specific laboratory-based diagnostic techniques for these diseases did not exist prior to 1940. While past reviewers reclassified problematic "dengue" outbreaks as CHIK, primarily based on manifestation of arthralgia as a marker of CHIK, they neither identified the root cause of the alleged misdiagnosis nor did they elaborate on the negative consequences derived from it. This article presents a reconstructed history of the genesis of the clinical definition of dengue by emphasizing problems with the definition, subsequent confusion with CHIK, and the ways in which physicians dealt with the variation in dengue-like ("dengue") syndromes. Then, the article identifies in those records several factors complicating reclassification, based on current practice and standards. These factors include terms used for characterizing joint problems, style of documenting outbreak data, frequency of manifestation of arthralgia, possible involvement of more than one agent, and occurrence of the principal vector. The analysis of those factors reveals that while some of the old "dengue" outbreaks, including the 1827-1828 outbreaks in the Americas, are compatible with CHIK, similar reclassification of other "dengue" outbreaks to CHIK is difficult because of a combination of the absence of pathognomonic syndrome in these diseases and conflicting background information

Revisiting Houston and Memphis: The Background Histories Behind the Discovery of the Infestation by Aedes albopictus (Diptera: Culicidae) in the United States and Their Significance in the Contemporary Research

ABSTRACT The discovery of Aedes albopictus Skuse infestation in Texas in 1985 and subsequent global spread of this mosquito have spawned a large number of publications worldwide. The unique discovery in this episode was used tire trade as mechanism by which this exotic mosquito was introduced to the United States. While most researchers have focused their attention primarily on recent events and scientiÞc progress, far fewer examined in depth early contributions made in the United States still very much relevant for contemporary discussion and other important subjects associated with its infestation. The Þrst part of this review covers early background histories of research on Ae. albopictus in the institutions in the United States and of introduction of Ae. albopictus and Ae. aegypti to the U.S. territories in the eastern PaciÞc as well as dengue outbreaks therein. The second part covers evolution of recognition of the importance of tire as breeding site of domesticated or peridomestic dengue vectors and of its transport in the dispersal of these mosquitoes. In the third part, the signiÞcance of vector-borne viral disease outbreak potential of Ae. albopictus and Ae. aegypti in temperate regions and a variety of problems concerning vector spread and commercial practices learned in the past are reassessed in the context of contemporary research. I further identiÞed as byproducts of this review two potentially important epidemiological mechanisms in the transmission of dengue in temperate regions, increasing tendency of indoor activity of Ae. albopictus and massive human movement associated with unpredictable political development

The Absence of Yellow Fever in Asia: History, Hypotheses, Vector Dispersal, Possibility of YF in Asia, and Other Enigmas

Since the recent epidemics of yellow fever in Angola and Brazil as well as the importation of cases to China in 2016, there has been an increased interest in the century-old enigma, absence of yellow fever in Asia. Although this topic has been repeatedly reviewed before, the history of human intervention has never been considered a critical factor. A two-stage literature search online for this review, however, yielded a rich history indispensable for the debate over this medical enigma. As we combat the pandemic of COVID-19 coronavirus worldwide today, we can learn invaluable lessons from the historical events in Asia. In this review, I explore the history first and then critically examine in depth major hypotheses proposed in light of accumulated data, global dispersal of the principal vector, patterns of YF transmission, persistence of urban transmission, and the possibility of YF in Asia. Through this process of re-examination of the current knowledge, the subjects for research that should be conducted are identified. This review also reveals the importance of holistic approach incorporating ecological and human factors for many unresolved subjects, such as the enigma of YF absence in Asia, vector competence, vector dispersal, spillback, viral persistence and transmission mechanisms

Título en español.

Many bacteria, fungi and several species of nematodes were isolated during a preliminary investigation of microorganisms associated with some insects of Puerto Rico. Although most of the organisms did not prove to be parasitic, a few fungi, notably Metarrhizium anisopliae and Entomophthora virulenta, were found highly pathogenic under laboratory conditions. Several protozoa belonging to Microsporida were found in Aedes mediovittatus, Anopheles grabhamii, Culex secutar, and Diatraea saccharalis for the first time.Durante la primera fase de la investigación sobre los microorganismos asociados con varios insectos de Puerto Rico, se aislaron muchas bacterias y hongos, así como varias especies de nematodos. Aunque la mayoría de dichos microorganismos probaron no ser parasíticos, se encontró que algunos hongos, particularmente Metarrhizium anisopliae y Entomophthora virulenta, eran muy patogénicos bajo las condiciones prevalecientes en el laboratorio. Además, varios parásitos protozoarios pertenecientes a los microspóridos, fueron descubiertos por primera vez en Aedes mediovittatus, Anopheles grabhamii, Culex secutor, y Diatraea saccharalis