Chikungunya Virus–Vector Interactions

Emerging and re-emerging arthropod-borne viruses (arboviruses) represent a significant threat to human and veterinary health worldwide. A mosquito-borne alphavirus that causes chikungunya fever (CHIK) is a severe, debilitating and often chronic arthralgia, from its first isolation in 1952, and detected as the etiologic agent of sporadic epidemics in Africa and Asia and, since 2004. Its geographic range expanded to circulate on Indian Ocean islands, and in Italy, France, and the Americas. CHIKV has also re-emerged in Southeast Asia since 2006, causing an estimated 1.3 million human cases. CHIKV cycles in urban settings between humans and two mosquito species found in the U.S., suggest a potential for endemic establishment in USA. Since 2004, CHIKV has emerged in Africa, Indian Ocean islands, Asia, Europe, and the Americas, causing millions of human infections. Understanding the natural ecology of transmission and vector infection dynamics are central to CHIKV emergence and management. In this process, Lark L. Coffey from Center for Vector borne Diseases, School of Veterinary Medicine, University of California, Davis, California and his associates reviewed CHIKV infection and vector life history traits including transmission cycles, genetic origins, distribution, emergence and spread, dispersal, vector competence, vector immunity and microbial interactions, and co-infection by CHIKV and other arboviruses. They studied genetics of vector susceptibility and host range changes, population heterogeneity and selection for the fittest viral genomes, dual host cycling and its impact on CHIKV adaptation, viral bottlenecks and intra host diversity. The potential for CHIKV re-emergence and expansion into new areas and prospects for prevention via vector control were also briefly identified.?

Aedes aegypti, ?which largely replaced A. albopictus in Southeast Asian cities, and A. albopictus have both spread beyond their native ranges via commercial trade. Vector competence, the ability of an arbovirus vector to acquire a pathogen and successfully transmit it to another susceptible host, is a complex process influenced by external factors including temperature, the availability of vertebrate hosts, vector population density and predation, as well as internal factors including mosquito survival and virus replication.?Both horizontal and vertical transmissions can occur. Vector mosquitoes ingest CHIKV from viremic vertebrate hosts during blood feeding. During the extrinsic incubation period that occurs in the vector, CHIKV infects the midgut and disseminates through the body cavity to infect salivary glands for secretion into saliva, which transmits the viral load to vertebrate vectors. The ability to circumvent bottlenecks within and between dynamic environments including switching between vector and vertebrate hosts plays role in expansion of the virus. ?Although novel strategies to control vector populations and reduce transmission are in early stages of field testing, the deployment of one of several highly promising human vaccines probably offers the best hope for making a major impact in restricting CHIKV circulation and preventing human disease.

Source: In: Viruses 2014, 6, 4628-4663.