The ecology of California group viruses.
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Animals↗
Biomedical subjects
J W LeDuc
Publications and source records attributed to J W LeDuc.
Natural transmission of Keystone virus to sentinel rabbits on the Delmarva Peninsula.
Domestic rabbits were exposed in the Pocomoke Cypress Swamp from early May through October 1973, to act as sentinel indicators of Keystone (KEY) virus transmission on the Delaware-Maryland-Virginia (DelMarVa) Peninsula. Rabbits were bled weekly and their sera were tested for the presence of neutralizing antibody to both KEY and James-town Canyon (JC) viruses. Adult mosquito activity was monitored concurrently by CDC miniature light traps with Dry Ice. Of 100 rabbits exposed, 20 rabbits acquired neutralizing antibody to KEY virus as a result of their exposure; none acquired antibody to JC virus. Eighty-three percent of susceptible rabbits exposed converted immediately after the emergence of Aedes atlanticus adult mosquitoes in early September. Rabbit seroconversions were not limited to any particular habitat within the swamp. The conversion of a large proportion of sentinel rabbits immediately following emergence of A. atlanticus, and the previous demonstration of transovarial transmission of KEY virus by A. atlanticus, suggest that vertically infected individuals are capable of viral transmission at their initial engorgement. Such transmission provides the initial step in a vertebrate amplification cycle.
Aedes↗
Towards a quantitative understanding of the epidemiology of Keystone virus in the eastern United States.
The implications of the Keystone virus--Aedes atlanticus transmission cycle are explored in the context of a quantitative model. Among the variables considered are the vertical transmission rate, the effect of the virus upon vector fertility and survival, vector densities and distributions, the proportion susceptible in the vertebrate population, the attractiveness of different vertebrates to the vector and vector survival rates. The logical relationships between these several variables are explored. It is concluded that the current view of Keystone virus maintenance is quantitatively feasible, and that certain predictions may be made as to the magnitude of several parameters which have not yet been measured. Such predictions allow direct testing of the model. The general structure of the model is such that it may prove useful in describing the epidemiology of other vector-borne infections in which vertical transmission is essential for infection maintenance at certain periods of the year.
Aedes↗
Ecology of Keystone virus, a transovarially maintained arbovirus.
Our studies in the Pocomoke Cypress Swamp of Maryland have shown that KEY strain of CE is endemic and is carried by the floodwater mosquito A. atlanticus. The virus is transmitted transstadially in nature, as evidenced by our recovery of virus from larvae and males of this species. Serologic evidence, both here and elsewhere, indicates that vertebrates are infected with KEY, but their role in the transmission cycle remains unknown. We have found several animals, for example, the gray squirrel, that are potential vertebrate reservoirs for the virus. Gray squirrels possess antibodies to KEY in nature, are known to be fed upon by A. atlanticus females, and have been shown to circulate a high-titered viremia after experimental inoculation. Evidence from 1974 collections, however, indicates that A. atlanticus females ingested only a single blood meal during the period when adults were active. We will not be able to assess the relative importance of the vertebrate and mosquito cycles until much more work has been performed on vector-reservoir-virus dynamics.
Aedes↗