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

THEILERIOSIS IN ZAMBIA : ETIOLOGY, EPIDEMIOLOGY AND CONTROL MEASURES

In Zambia, theileriosis manifests itself in the form of Corridor disease (CD), caused by Theileria parva lawrencei, and East Coast fever (ECF), caused by T. parva parva. Of the approximately 3 million cattle in Zambia, 1.4 million are at risk to theileriosis. ECF is found in the Northern and Eastern provinces of the country, while CD appears in Southern, Central, Lusaka and Copperbelt provinces. Theileriosis is a major constraint to the development of the livestock industry in Zambia, with losses of about 10,000 cattle per annum. The disease is spreading at a very fast rate, over-flowing its original borders. The epidemiology is complicated by, among other factors, the wide distribution of the tick vector, Rhipicephalus appendiculatus, which is found all over the country. The current strategy of relying on tick control and therapeutic drugs as a way of controlling the disease is becoming increasingly difficult for Zambia. This is because both curative drugs and acaricides are very costly. Immunization against theileriosis using the infection and treatment method as a way of controlling the disease is becoming increasingly accepted, provided local Theileria stocks are used. This paper reviews the incidence of theileriosis in the last 2 years, 1991 and 1992. It also gives a historical perspective of the disease, epidemiology and control measures presently in use

VIRAL DISEASES OF LIVESTOCK IN ZAMBIA

This review is to provide information on viral diseases of livestock in Zambia. The distribution of the diseases as well as the control measures and limited research that has been done, are described. Foot and mouth disease (FMD) causes serious economic losses in the cattle industry. So far five serotypes (SAT1, SAT2, SAT3, O and A) of FMD virus have been isolated in Zambia. Other notifiable viral diseases are rabies, Rift Valley fever, lumpy skin disease, African horse sickness, bluetongue, African swine fever, Newcastle disease, Marek's disease, fowlpox and infectious bursal disease. Based on the reports of clinical and/or serological diagnoses, these are widespread in the country, although their precise incidence rates are not known. With the establishment of a veterinary school equipped with modern diagnostic facilities and the increasing number of qualified veterinary personnel, this review would stimulate surveillance study on the viral diseases for the ultimate goal of achieving effective disease control measures

The Epidemiology of African Swine Fever in "Nonendemic" Regions of Zambia (1989-2015) : Implications for Disease Prevention and Control.

African swine fever (ASF) is a highly contagious and deadly viral hemorrhagic disease of swine. In Zambia, ASF was first reported in 1912 in Eastern Province and is currently believed to be endemic in that province only. Strict quarantine measures implemented at the Luangwa River Bridge, the only surface outlet from Eastern Province, appeared to be successful in restricting the disease. However, in 1989, an outbreak occurred for the first time outside the endemic province. Sporadic outbreaks have since occurred almost throughout the country. These events have brought into acute focus our limited understanding of the epidemiology of ASF in Zambia. Here, we review the epidemiology of the disease in areas considered nonendemic from 1989 to 2015. Comprehensive sequence analysis conducted on genetic data of ASF viruses (ASFVs) detected in domestic pigs revealed that p72 genotypes I, II, VIII and XIV have been involved in causing ASF outbreaks in swine during the study period. With the exception of the 1989 outbreak, we found no concrete evidence of dissemination of ASFVs from Eastern Province to other parts of the country. Our analyses revealed a complex epidemiology of the disease with a possibility of sylvatic cycle involvement. Trade and/or movement of pigs and their products, both within and across international borders, appear to have been the major factor in ASFV dissemination. Since ASFVs with the potential to cause countrywide and possibly regional outbreaks, could emerge from "nonendemic regions", the current ASF control policy in Zambia requires a dramatic shift to ensure a more sustainable pig industry

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