Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Veterinary Medical Sciences - Pathobiological Sciences

First Advisor

Martin E. Hugh-Jones

Abstract

Many unanswered questions on the epidemiology and ecology of eastern equine encephalomyelitis (EEE) still preclude a complete understanding of its natural history. Among these are the distribution and epidemic vectors of EEE virus (EEEV) in different regions, habitats, and foci; its inter-epidemic maintenance, and overwintering mechanisms. Phase 1 of a research project designed to find answers to the above questions with regard to southeast Louisiana was conducted over 1992 and 1993, and consisted of several individual studies. These included 3 mosquito studies to determine major horse- and bird-feeding mosquito species that could be the EEEV epidemic vectors in southeast Louisiana; a chicken serological study to establish and monitor EEEV activity in the study areas so that the epidemic vector potential of the identified major species could be verified and a transfer interval between birds and horses or humans could be determined; and a horse serological study to deal with the distribution, inter-epidemic, and overwintering mechanism questions. An attempt was also made to assess the influence of environmental factors on the population dynamics and feeding patterns of the identified major species. The results of these studies are summarized as follows: (1) Many major horse- and bird-feeding species were identified. However, only Culex (Melanoconion) spp. was strongly suggested as a potential epidemic vector of EEEV. The species avidly fed on both horses and birds, its population increased simultaneously with increasing EEEV activity, it shares breeding habitats with the endemic vector, Culiseta melanura, and it is ubiquitous; (2) an even distribution of EEEV in St. Tammany Parish was established, thus providing a basis for future similar studies; (3) continued EEEV activity and transmission during 1993 was indicated even though the year was non-epidemic; (4) continued EEEV activity during the 1992/93 winter months was also suggested, thus casting doubt on the necessity of an overwintering mechanism; (5) the results demonstrated that appropriately located private chicken yards could be an inexpensive and effective EEEV monitoring tool and that vaccinated horses might be a valuable tool for detecting and, perhaps, monitoring EEEV inter-epidemic activity; (6) the environmental factor assessment had little success and the transfer interval could not be determined.

Pages

118

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