Dataset Information

Epidemiology and control of bovine ephemeral fever.

ABSTRACT: Bovine ephemeral fever (or 3-day sickness) is an acute febrile illness of cattle and water buffaloes. Caused by an arthropod-borne rhabdovirus, bovine ephemeral fever virus (BEFV), the disease occurs seasonally over a vast expanse of the globe encompassing much of Africa, the Middle East, Asia and Australia. Although mortality rates are typically low, infection prevalence and morbidity rates during outbreaks are often very high, causing serious economic impacts through loss of milk production, poor cattle condition at sale and loss of traction power at harvest. There are also significant impacts on trade to regions in which the disease does not occur, including the Americas and most of Europe. In recent years, unusually severe outbreaks of bovine ephemeral fever have been reported from several regions in Asia and the Middle East, with mortality rates through disease or culling in excess of 10-20%. There are also concerns that, like other vector-borne diseases of livestock, the geographic distribution of bovine ephemeral fever could expand into regions that have historically been free of the disease. Here, we review current knowledge of the virus, including its molecular and antigenic structure, and the epidemiology of the disease across its entire geographic range. We also discuss the effectiveness of vaccination and other strategies to prevent or control infection.

SUBMITTER: Walker PJ

PROVIDER: S-EPMC4624662 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Epidemiology and control of bovine ephemeral fever.

Walker Peter J PJ Klement Eyal E

Veterinary research 20151028

Bovine ephemeral fever (or 3-day sickness) is an acute febrile illness of cattle and water buffaloes. Caused by an arthropod-borne rhabdovirus, bovine ephemeral fever virus (BEFV), the disease occurs seasonally over a vast expanse of the globe encompassing much of Africa, the Middle East, Asia and Australia. Although mortality rates are typically low, infection prevalence and morbidity rates during outbreaks are often very high, causing serious economic impacts through loss of milk production, p ...[more]

PMID: 26511615

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Project description:Bovine ephemeral fever virus (BEFV) is an arthropod-borne rhabdovirus that causes a debilitating disease of cattle in Africa, Asia, and Australia; however, its global geodynamics are poorly understood. An evolutionary analysis of G gene (envelope glycoprotein) ectodomain sequences of 97 BEFV isolates collected from Australia during 1956 to 2012 revealed that all have a single common ancestor and are phylogenetically distinct from BEFV sampled in other geographical regions. The age of the Australian clade is estimated to be between 56 and 65 years, suggesting that BEFV has entered the continent on few occasions since it was first reported in 1936 and that the 1955-1956 epizootic was the source of all currently circulating viruses. Notably, the Australian clade has evolved as a single genetic lineage across the continent and at a high evolutionary rate of ∼10(-3) nucleotide substitutions/site/year. Screening of 66 isolates using monoclonal antibodies indicated that neutralizing antigenic sites G1, G2, and G4 have been relatively stable, although variations in site G3a/b defined four antigenic subtypes. A shift in an epitope at site G3a, which occurred in the mid-1970s, was strongly associated with a K218R substitution. Similarly, a shift at site G3b was associated primarily with substitutions at residues 215, 220, and 223, which map to the tip of the spike on the prefusion form of the G protein. Finally, we propose that positive selection on residue 215 was due to cross-reacting neutralizing antibody to Kimberley virus (KIMV). This is the first study of the evolution of BEFV in Australia, showing that the virus has entered the continent only once during the past 50 to 60 years, it is evolving at a relatively constant rate as a single genetic lineage, and although the virus is relatively stable antigenically, mutations have resulted in four antigenic subtypes. Furthermore, the study shows that the evolution of BEFV in Australia appears to be driven, at least in part, by cross-reactive antibodies to KIMV which has a similar distribution and ecology but has not been associated with disease. As BEFV and KIMV are each known to be present in Africa and Asia, this interaction may occur on a broader geographic scale.

Project description:BackgroundBovine ephemeral fever virus (Rhabdoviridae: Ephemerovirus) (BEFV) causes bovine ephemeral fever (BEF), an economically important disease of cattle and water buffalo. Outbreaks of BEF in Africa, Australia, Asia and the Middle East are characterized by high rates of morbidity and highly efficient transmission between cattle hosts. Despite this, the vectors of BEFV remain poorly defined.MethodsColony lines of biting midges (Culicoides sonorensis) and mosquitoes (Aedes aegypti, Culex pipiens and Culex quinquefasciatus) were infected with a strain of BEFV originating from Israel by feeding on blood-virus suspensions and by intrathoracic inoculation. In addition, in vivo transmission of BEFV was also assessed by allowing C. sonorensis inoculated by the intrathoracic route to feed on male 6 month-old Holstein-Friesian calves.ResultsThere was no evidence of BEFV replication within mosquitoes fed on blood/virus suspensions for mosquitoes of any species tested for each of the three colony lines. In 170 C. sonorensis fed on the blood/virus suspension, BEFV RNA was detected in the bodies of 13 individuals and in the heads of two individuals, indicative of fully disseminated infections and an oral susceptibility rate of 1.2%. BEFV RNA replication was further demonstrated in all C. sonorensis that were inoculated by the intrathoracic route with virus after 5, 6 or 7 days post-infection. Despite this, transmission of BEFV could not be demonstrated when infected C. sonorensis were allowed to feed on calves.ConclusionsNo evidence for infection or dissemination of BEFV (bovine/Israel/2005-6) in mosquitoes of three different species was found. Evidence was found for infection of C. sonorensis by the oral route. However, attempts to transmit BEFV to calves from infected C. sonorensis failed. These results highlight the challenge of defining the natural vector of BEFV and of establishing an in vivo transmission model. The results are discussed with reference to the translation of laboratory-based studies to inference of vector competence in the field.

Dataset Information

Epidemiology and control of bovine ephemeral fever.

Publications

Epidemiology and control of bovine ephemeral fever.

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