Intertwined arbovirus transmission activity: reassessing the transmission cycle paradigm

Abstract

Arboviruses are emerging/reemerging infectious agents worldwide. The factors within this scenario include vector and host population fluctuations, climatic changes, anthropogenic activities that disturb ecosystems, an increase in international flights, human mobility, and genetic mutations that allow spill-over phenomenon. Arboviruses are maintained by biologic transmission among vectors and hosts. Sometimes this biological transmission is specific and includes one vector and host species such as Chikungunya (CHIKV), Dengue (DENV), and urban Yellow Fever (YFV). However, most of the arboviruses are generalist and they use many vectors and hosts species. From this perspective, arboviruses are maintained through a transmission network rather than a transmission cycle. This allows us to understand the complexity and dynamics of the transmission and maintenance of arboviruses in the ecosystems. The old perspective that arboviruses are maintained in close and stable transmission cycles should be modified by a new more integrative and dynamic idea, representing the real scenario where biological interactions have a much broader representation, indicating the constant adaptability of the biological entities.

Seroprevalence of Flavivirus in horses in Chaco, Argentina. Circulation during 2013-2014

“…These results suggest the need for additional studies on viral circulation in mosquitoes and hosts. Although equines are important WNV vertebrate hosts, only a limited number of dead or diseased horses have been diagnosed in America (Díaz et al, 2013). These authors suggest that prior exposure to others Flavivirus could modulate the disease in subsequent exposures to WNV, which could be a possible explanation that none of the horses infected with this virus in the present study have developed a clinical response.…”

“…SLEV is known to cause subclinical infections in horses nevertheless; the first isolation of SLEV from a horse that died due to a neurological disease in Brazil is a significant event. This is the first observation that SLEV can cause disease in horses, which indicates that some aspects of its viral cycle and its ability to cause disease need further studies (Díaz et al, 2013).…”

Culex saltanensis and Culex interfor (Diptera: Culicidae) are susceptible and competent to transmit St. Louis encephalitis virus (Flavivirus: Flaviviridae) in central Argentina.

“…increase in abundance with peaks in summer, with are temporal distribution of Culex spp. coinciding with the activity peaks of SLEV in human infection [3,39]. Adult mosquitoes belonging to the species Cx.…”

Molecular and cellular evidence of natural Venezuelan equine encephalitis virus infection in frugivorous bats in Colombia

“…The analysis of the dynamic maintenance of these viruses appears to link to a transmission network instead of a transmission cycle [11]. The mechanisms for the maintenance of arboviruses are intrinsically complicated and must be taken into account and incorporated when designing and constructing mathematical models that allow predicting their enzootic/ epidemic activity in a given ecosystem (wild, urban, and agricultural, as well).…”

“…These animals become infected and develop viremia that is sufficient to infect the vectors [9,10]. Different studies have reported evidence of VEEV infection, suggesting that bats (frugivorous, sanguinivorous, and insectivorous) could be host to arboviruses of public health impact in America [11][12][13][14][15]. Clinically, VEEV is indistinguishable from dengue and other arboviral diseases, often humans infected with VEEV symptoms appear within 2-5 days, and range from febrile, or flu-like symptoms, such as malaise, fever, chills, and myalgia, to coma and death are registered in ~1% of cases [3].…”