HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Barnett, H. C. Search for Related Content PubMed PubMed Citation Articles by Barnett, H. C.

The Transmission of Western Equine Encephalitis Virus by the Mosquito Culex Tarsalis Coq^1,2,

This investigation confirmed and extended the work of Hammon and Reeves (1943) which demonstrated that the mosquito Culex tarsalis is capable of transmitting Western equine encephalitis virus from bird to bird. Virus was transmitted from chicken to chicken, from canary to canary, and from canary to chicken; 131 transmissions of virus were obtained in the study, and 29 (22 per cent) of the agents transmitted were re-identified by neutralization test.

Infectivity was acquired by these mosquitoes only when they fed on a bird with a threshold, or greater, level of viremia. This threshold level, of viremia was shown to be not more than an LD₅₀ titer of 3.2. The minimal extrinsic incubation period was found to be four days, and it was further demonstrated that the rate of transmission steadily increased from 10 per cent on the fourth day to 84 per cent after the thirteenth day following the infective blood-meal. Transmission was readily accomplished by the bite of a single infective mosquito, and virus was transmitted by such a mosquito as often as four times in eleven days. Virus transmission was obtained from mosquitoes as late as sixty days after they had had an infective blood-meal, and from these results it is presumed that mosquitoes can remain infective for life.

Negative results were obtained in all attempts to demonstrate transovarian passage of western equine encephalitis virus in C. tarsalis. One mechanical transmission of virus by C. tarsalis was obtained in 24 attempts, suggesting that this phenomenon may also occur in nature, but the epidemiologic significance is not known.

¹ Part of a thesis submitted to the Graduate School of the University of Pittsburgh in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

² This work was carried out under sponsorship of the Commission on Virus and Rickettsial Diseases of the Armed Forces Epidemiological Board, and was supported in part by a contract with the Office of the Surgeon General, Department of the Army.

³ Address: Walter Reed Army Institute of Research, Washington, D. C.

⁴ This work was carried out at the Rocky Mountain Laboratory, National Microbiological Institute, U. S. Public Health Service, Hamilton, Montana.