Medical importance of Culex tritaeniorhynchus

Cx. tritaeniorhynchus is a potential vector of pathogens that cause human diseases. It is the primary vector of Japanese encephalitis (JE) in southern Asia. It has also been found infected with Dengue, Rift Valley fever, Sindbis, Getah and Tembusu viruses, and microfilariae of both Brugia malayi and Wuchereria bancrofti, in many areas of eastern and southeastern Asia. Laboratory experiments have confirmed the vector capability of Cx. tritaeniorhynchus for West Nile Virus.

JE is the leading cause of viral encephalitis in South East Asia and is endemic in India, China, Japan, South East Russia, all of South East Asia and West Pacific.

Less than 1% of human Japanese Encephalitis Virus (JEV) infections result in JE. 60-70,000 new JE cases occurs globally each year. Approximately 20–30% of JE cases are fatal and 30–50% of survivors have significant neurologic sequelae. JE is primarily a disease of children and most adults in endemic countries have natural immunity after childhood infection, but all age groups are affected. The presence of pigs and marsh birds is crucial in the etiology of JE, as the virus is carried by birds and amplified by pigs.

The occurrence of JE is largely restricted to rural settings. The cultivation of rice and the management of paddy water strongly influence the transmission of JE. The rice cultivation practices, the domicilliary surroundings with adjacent water bodies, and the high temperature and humidity were found to be the main environmental factors influencing the abundance of the potential mosquito vectors responsible for the transmission of the virus.The presence of pigs and marsh birds is also crucial in the epidemiology of JE, as the virus is carried by birds and amplified by pigs. Human is dead-end host.

Autochthonous cases of (JE) have never been reported in Europe. However, a fragment of JEV RNA has been detected in Culex pipiens mosquitoes and birds in Italy. The establishment of JEV in new ecosystems outside of its current range is difficult. With the spread of JEV into much of the Indian subcontinent, however, other destinations served by frequent routes of commerce or passenger air travel, such as Africa and Europe, could also be at risk. Whether JEV represents a human health threat in Europe merits further investigation.

Editing: Ioanna Lytra
Agronomist, MScD Student
Agricultural University of Athens

The literature review and the studies conducted from the Agricultural University of Athens are derived from a research that has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) – Research Funding Program: Heracleitus II. Investing in knowledge society through the European Social Fund.