The Habitat, Ecology and Epidemiology of Eastern Equine Encephalomyelitis in Southeast Louisiana.

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

Evidence of Yersinia pestis DNA from fleas in an endemic plague area of Zambia

BACKGROUND: Yersinia pestis is a bacterium that causes plague which infects a variety of mammals throughout the world. The disease is usually transmitted among wild rodents through a flea vector. The sources and routes of transmission of plague are poorly researched in Africa, yet remains a concern in several sub-Saharan countries. In Zambia, the disease has been reported on annual basis with up to 20 cases per year, without investigating animal reservoirs or vectors that may be responsible in the maintenance and propagation of the bacterium. In this study, we undertook plague surveillance by using PCR amplification of the plasminogen activator gene in fleas. FINDINGS: Xenopsylla species of fleas were collected from 83 rodents trapped in a plague endemic area of Zambia. Of these rodents 5 had fleas positive (6.02%) for Y. pestis plasminogen activator gene. All the Y. pestis positive rodents were gerbils. CONCLUSIONS: We conclude that fleas may be responsible in the transmission of Y. pestis and that PCR may provide means of plague surveillance in the endemic areas of Zambia

Co-Circulation of Multiple Serotypes of Bluetongue Virus in Zambia

Bluetongue (BT) is an arthropod-borne viral disease of ruminants with serious trade and socio-economic implications. Although the disease has been reported in a number of countries in sub-Saharan Africa, there is currently no information on circulating serotypes and disease distribution in Zambia. Following surveillance for BT in domestic and wild ruminants in Zambia, BT virus (BTV) nucleic acid and antibodies were detected in eight of the 10 provinces of the country. About 40% (87/215) of pooled blood samples from cattle and goats were positive for BTV nucleic acid, while one hartebeest pool (1/43) was positive among wildlife samples. Sequence analysis of segment 2 revealed presence of serotypes 3, 5, 7, 12 and 15, with five nucleotypes (B, E, F, G and J) being identified. Segment 10 phylogeny showed Zambian BTV sequences clustering with Western topotype strains from South Africa, intimating likely transboundary spread of BTV in Southern Africa. Interestingly, two Zambian viruses and one isolate from Israel formed a novel clade, which we designated as Western topotype 4. The high seroprevalence (96.2%) in cattle from Lusaka and Central provinces and co-circulation of multiple serotypes showed that BT is widespread, underscoring the need for prevention and control strategies