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PubMed2005

Bovine ephemeral fever in Australia and the world.

Bovine ephemeral fever (BEF) is a disabling viral disease of cattle and water buffaloes. It can cause significant economic impact through reduced milk production in dairy herds, loss of condition in beef cattle and loss of draught animals at the time of harvest. Available evidence indicates clinical signs of BEF, which include bi-phasic fever, anorexia, muscle stiffness, ocular and nasal discharge, ruminal stasis and recumbency, are due primarily to a vascular inflammatory response. In Australia, between 1936 and 1976, BEF occurred in sweeping epizootics that commenced in the tropical far north and spread over vast cattle grazing areas of the continent. In the late 1970s, following several epizootics in rapid succession, the disease became enzootic in most of northern and eastern Australia. In Africa, the Middle East and Asia, BEF occurs as also epizootics which originate in enzootic tropical areas and sweep north or south to sub-tropical and temperate zones. The causative virus is transmitted by haematophagous insects that appear to be borne on the wind, allowing rapid spread of the disease. Bovine ephemeral fever virus (BEFV) has been classified as the type species of the genus Ephemerovirus in the Rhabdoviridae. It has a complex genome organization which includes two glycoprotein genes that appear to have arisen by gene duplication. The virion surface glycoprotein (G protein) contains four major antigenic sites that are targets for neutralizing antibody. An analysis of a large number of BEFV isolates collected in Australia between 1956 and 1992 has indicated remarkable stability in most neutralization sites. However, epitope shifts have occurred in the major conformational site G3 and these have been traced to specific mutations in the amino acid sequence. BEFV isolates from mainland China and Taiwan are closely related to Australian isolates, but some variations have been detected. Natural BEFV infection induces a strong neutralizing antibody response and infection usually induces durable immunity. Several forms of live-attenuated, inactivated and recombinant vaccines have been reported but with variable efficacy and durability of protection. The BEFV G protein is a highly effective vaccine antigen, either as a purified subunit or expressed from recombinant viral vectors.

Africa↗
PubMed1987

Epidemiology of bovine ephemeral fever in Australia 1981-1985.

Bovine ephemeral fever is an important viral disease of cattle in Australia. The disease occurred each year, principally in summer and autumn, between 1981 and 1985. Queensland and the northern half of New South Wales were areas of greatest activity with only sporadic cases being reported from the Northern Territory and the northern third of Western Australia. Since 1981, the disease has been endemic in an extensive area of eastern Australia and has tended to occur in widely scattered outbreaks rather than the north-south advancing wave form of the epidemics of 1936-37, 1967-68, 1970-71 and 1972-74. The southernmost outbreaks between 1981 and 1985 were well within the limits of these earlier epidemics. The pattern of disease appears to have become seasonally endemic rather than periodically endemic in the northern two-thirds of eastern Australia. Ephemeral fever was not recorded in Victoria, Tasmania, South Australia or the southern part of Western Australia between 1981 and 1985. The disease was most frequently reported in cattle under 3 years of age, but also occurred in older cattle.

Animals↗
PubMed2005

Bovine ephemeral fever in Taiwan (2001-2002).

Bovine ephemeral fever (BEF), a vector-borne disease of cattle, is caused by the Ephemerovirus of the family Rhabdoviridae. In the past 40 years, Taiwan has had seven BEF epizootics, and we have previously reported the first five. This study summarizes the 2001 and 2002 epizootics; conducted case-control serologic studies on 10 herds involved in the 2001 epizootic; determined whether the recent BEF viruses have varied significantly; and discusses the relationship between epizootic patterns and possible variant BEF viruses. For mature cows that had received at least 2 doses of vaccine before the study, a negative correlation between the prevaccinated (the 3rd dose and after) serum neutralization antibody (SNA) titers and their postvaccinated peak rates was found. When prevaccinated SNA levels were at < or = 32, their postvaccinated SNA levels increased significantly faster (P<0.01) than for those at > or = 32. The glycoprotein gene of isolates from 1999, 2001, and 2002 had a 99.2-99.9% homology, without consistent amino acid variations in the neutralization sites. Phylogenetic analysis of Taiwanese isolates revealed 2 distinct clusters, the 1983-1989 and 1996-2002 isolates. Cross-neutralization tests confirmed the glycoprotein gene sequence analysis results. In conclusion, annual boosters at SNA levels > 32, at more than 2 doses, or at intervals shorter than 6 months are not advisable. The occurrence of frequent small epizootics implies the dominance of BEF virus over host immunity, but not a variant virus.

Animals↗
PubMed1998

Epizootics of bovine ephemeral fever on dairy farms in Saudi Arabia.

In 1990 and 1996, field veterinarians suspected the clinical occurrence of bovine ephemeral fever among dairy and conventional cattle in different regions of Saudi Arabia. The disease has a seasonal occurrence; it begins in early summer (May) and ends in late autumn (November). The mortality rate is low: 0.3% to 0.6%. The morbidity rate ranged from 5% to 61% within the different age groups of one affected herd in the 1996 outbreaks and from 3.4% to 19% among four affected herds in the 1990 outbreaks. A sudden sharp drop in milk production occurred in lactating animals, some of which had become dry by the end of the outbreaks. Trials to isolate the causative virus in cell culture and in baby mice were unsuccessful. Serum neutralisation tests, which used a cell culture-adapted vaccine strain of bovine ephemeral fever virus as an antigen, revealed the presence of specific antibodies with significantly increased titres in the convalescent sera of affected animals. In addition, the testing of paired sera from non-affected heifers and from both dry and milking cows, performed twice, with an interval of 21 days, revealed the presence of neutralising antibodies. In the 1990 outbreaks, comparative serological studies indicated a high percentage (67.5%; 27/40) of seropositive animals in herds in which bovine ephemeral fever had been previously suspected. No antibodies were detected in animals of herds which had no recorded clinical history of bovine ephemeral fever. Following serological confirmation of the prevalence of bovine ephemeral fever in Saudi Arabia, some dairy farms started using a live imported vaccine to control the disease. This study discusses the epizootiological findings in regard to bovine ephemeral fever, as well as its economic impact on four affected dairy farms in 1990. In addition, the authors evaluate the efficacy of immunoprophylaxis in another dairy herd during the same outbreaks.

Acute Disease↗
PubMed1975

The infection of merino sheep with bovine ephemeral fever virus.

Four Merino sheep inoculated intravenously with bovine blood containing ephemeral fever virus showed no clinical signs of ephemeral fever. Two sheep showed a mild haematological response and developed a neutralising antibody which closely paralled that of a steer inoculated at the same time. Leucocytes harvested from these 2 sheep on days 3 and 4 after inoculation with virus reproduced ephemeral fever when inoculated into susceptible steers whilst those harvested on days 1, 2 and 5 did not. Even though this indicates that EFV can multiply in some sheep when they are inoculated intravenously, it cannot be inferred that natural infection occurs.

Animals↗
PubMed1985

Studies on the pathogenesis of bovine ephemeral fever in sentinel cattle. I. Virology and serology.

Twenty-two sentinel cattle were observed daily during an outbreak of ephemeral fever on a dairy farm in eastern Australia in the summer of 1981-82. Of the 22 cattle, 9 developed clinical ephemeral fever. None developed sub-clinical infection. The pattern of the epidemic was a single index case followed 10 days later by the main epidemic wave which lasted for 7 days. This wave stopped when there were still 14 uninfected susceptible animals remaining in the sentinel group, and when biting flies were very active. Ten isolations of bovine ephemeral fever virus were made in Aedes albopictus tissue cultures from the blood of 5 clinical cases. One hundred and twelve isolations of CSIRO Village virus and one each of Kimberley and Akabane viruses were also made from various members of the sentinel group. There was serological evidence that infections with Tibrogargan, Tinaroo and Aino viruses also occurred in 6 cattle in the observation period. The 13 cattle undergoing a sub-clinical viraemia with CSIRO Village virus, Tibrogargan, Kimberley, Akabane or Aino viruses at the time of the main outbreak, appeared to be temporarily protected against ephemeral fever. However, 9 of the 11 still remaining in the herd were susceptible in a subsequent outbreak of ephemeral fever 2 years later. Evidence is presented that subclinical infections with other arboviruses may limit an ephemeral fever epidemic by providing temporary protection by interference.

Aedes↗
PubMed2004

Apoptosis induced by bovine ephemeral fever virus.

The potential significance of bovine ephemeral fever virus (BEFV)-induced apoptosis and involved viral molecules was fully unknown. In the present study, evidence is provided demonstrating that bovine ephemeral fever virus induces apoptosis in several cell lines. Five types of assays for apoptosis were used in examining BEFV-infected cells. (1) Assay for DNA fragmentation, (2) nuclear staining with acridine orange, (3) ELISA detection of cytoplasmic histone-associated DNA fragment, (4) terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick-end labelling (TUNEL) assay of BEFV-infected cells, (5) observation of blebbing of the plasma membrane and the formation of apoptotic bodies of apoptic cells by scanning electron microscope. The level of lactate dehydrogenase (LDH) in BEFV-infected cells was increased significantly after 20-25 h post-infection. Caspases-2, -3, -4, -6, -8, -9, and -10 were activated in BEFV-infected BHK-21 cells. To determine further whether BEFV-induced apoptosis was caspase-dependent, the effect of the tripeptide pan-ICE (caspase) inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyketone on the inhibition of apoptosis in BEFV-infected BHK-21 cells, was investigated. Apoptosis could be blocked by the caspase inhibitor (Z-VAD-fmk), indicating that BEFV induces caspase-dependent apoptosis in cultured cells.

Animals↗
PubMed1977

The epizootiology of bovine ephemeral fever in Australia and Papua-New Guinea.

The epizootiology of ephemeral fever in Australia from its first recognition until 1968 was reviewed. Since 1968, ephemeral fever often in a silent form has been shown to be enzootic in northern Australia, by the use of sentinel cattle. The major epizootics which occured in 1970-1971, 1972-1974 and 1974-1975 are described. These epizootics were characterised by an apparently rapid movement of disease in a general north-south direction in summer months. Ephemeral fever antibody was detected in 11% of 1009 domesticated and feral water buffaloes.

Animals↗
PubMed1990

The occurrence of ephemeral fever in Kenya, 1968-1988.

Ephemeral fever occurs in Kenya in epidemics which have been associated with periods of unusually heavy and prolonged rainfall. The epidemics persist for 2-3 years and involve most of the country. They occur in the same years as epizootics of Rift Valley fever, which is a mosquito-borne Phlebovirus infection. Sporadic outbreaks of the disease have been associated with local heavy rains; though one outbreak occurred during a dry period. Culicoides spp. were generally present in large numbers at the site of the outbreaks. Seroconversions were detected in sentinel cattle, when there had been no apparent clinical disease.

Animals↗
PubMed1985

Studies on the pathogenesis of bovine ephemeral fever in sentinel cattle. II. Haematological and biochemical data.

Twenty-two non-lactating dairy cattle from a sentinel herd previously described (St. George, 1985) were monitored daily during an outbreak of ephemeral fever. Nine developed clinical ephemeral fever between 25 December 1981 and 30 January 1982. There were no subclinical infections with bovine ephemeral fever virus in the group. There were, however, subclinical infections with CSIRO Village, Akabane, Aino, Tinaroo and Kimberley viruses as described by St. George et al. (1984). Six of the nine affected cattle showed a neutrophilia with a concurrent lymphopaenia on the day of pyrexia; however, the differential white cell profile had begun to change up to 24 h prior to leucocytosis. Serum carboxypeptidase values fell by 24 h following the febrile response. Plasma fibrinogen rose rapidly in all six cows. The peak concentration (15.6 +/- 2.70 g l-1) occurred 3 days after pyrexia with the highest individual increase being from 6.05 to 19.6 g l-1. Plasma fibrinogen levels remained elevated for at least 7 days. Serum calcium fell significantly during Day 1 of the disease, the mean decline being 0.22 +/- 0.08 mmol l-1. The greatest individual fall was from 2.33 to 1.92 mmol l-1. None of the affected cattle showed any compensatory change in serum magnesium. There was no change in the normal values of creatinine, urea, gamma-GT, AST and alkaline phosphatase. Bovine ephemeral fever virus was isolated from only four of the six cases, whereas specific antibody was detected in all cattle 3-4 days after recovery.

Animals↗
PubMed1999

Observations on the recent epizootic of bovine ephemeral fever in Saudi Arabia.

Observations of the epizootic of bovine ephemeral fever which occurred in Saudi Arabia during 1996 are presented. The investigations included the collection of epidemiological data from affected farms and the testing of sera for antibodies to the virus. The authors report a mean morbidity rate of 50% and a mean case fatality rate of 0.3%. Of the infected cattle, 4% were affected by recumbency, the majority of these recovered (89%). The clinical signs observed in affected cattle were uniform throughout the region concerned. The features of the outbreak, obtained through field investigations, were considered in relation to the ecological and meteorological conditions which were prevalent at the time. The outbreak occurred during the summer months (May to October) in the central and eastern regions of Saudi Arabia, with the initial infection reported at the Al-Ahsa oasis. Farms which were subsequently affected were all reported to possess areas of stagnant water suitable for the reproduction of the vectors of the disease (Culicoides spp. and mosquitoes). To conclude, the authors discuss precautions to prevent future outbreaks of bovine ephemeral fever in Saudi Arabia.

Animals↗
PubMed1975

The susceptibility of calves to infection with a strain of bovine ephemeral fever virus inoculated intracerebrally.

Three newborn calves were inoculated intracerebrally with bovine ephemeral fever virus strain 525. The 2 that lacked detectable neutralising antibody to bovine ephemeral fever vaccine developed fatal encephalitis after 4 and 7 days respectively. The third calf which had a low level of maternal antibody remained healthy and developed antibody that became undetectable after 6 months. Bovine ephemeral fever virus strain 525 was reisolated from the brains of both dead calves by intracerebral inoculation of suckling mice. Homogenates that were prepared from the brains of the calves failed to produce disease or to induce antibody formation in susceptible calves when inoculated intravenously. Strain 525 of BEF virus has been shown to possess a degree of neurovirulence for laboratory animals that has not been reported for other strains (Tzipori and Spradbrow 1974). Although this strain is unable to produce viraemia in calves after I/V inoculation, the present study shows that strain 525 can multiply in the brain tissues of calves and cause death after I/C inoculation.

Animals↗
PubMed1992

A blocking ELISA for the detection of specific antibodies to bovine ephemeral fever virus.

A blocking ELISA (B/ELISA) for detecting antibodies to bovine ephemeral fever virus (BEFV) in cattle is described. In this test, the binding capacity of a monoclonal antibody specific for an epitope on antigenic site G1 of the BEF virus glycoprotein is blocked in the presence of positive serum. The sensitivity of the B/ELISA was compared with the virus neutralisation (VN) test using a total of 380 sera from cattle. Of these, 118 were from an area known to be free of bovine ephemeral fever, 181 from naturally and experimentally BEFV-infected cattle, 33 sequential serum samples from a sentinel steer from which Berrimah virus (BERV) had been isolated, 9 from a sentinel cow from which Kimberley virus (KIMV) was isolated and a panel of 39 sera supplied as a blind trial. The B/ELISA results overall compared favourably with those of the VN tests. The monospecificity of the test was demonstrated using hyperimmune mouse ascitic fluid to other BEF serogroup viruses, namely KIM and BER viruses and the results showed no significant cross-reaction. The greater simplicity and sensitivity of the test when compared with the VN test makes it the preferred test for the diagnosis and monitoring of clinical bovine ephemeral fever.

Animals↗
PubMed1975

The effect of bovine ephemeral fever virus on the bovine foetus.

Six pregnant heifers that were experimentally infected with bovine ephemeral fever virus produced normal calves. Foetuses of 8 heifers that were immune to bovine ephemeral fever were inoculated with bovine ephemeral fever virus. One was aborted after 36 days, but the cause of abortion could not be determined. One was sacrificed after 28 days. The foetus and its membranes were normal and neither virus nor antibody was demonstrated. The other 6 heifers produced normal calves. One calf, 501, inoculated after 160 days gestation, contained high levels of neutralising antibody in serum before ingestion of colostrum. The others, inoculated at gestational ages of 52 days to 157 days showed no evidence of neutralising antibody in blood samples collected at birth.

Abortion, Veterinary↗
PubMed2002

Epidemiological investigations of outbreaks of bovine ephemeral fever in Israel.

In two epidemics of bovine ephemeral fever (BEF) in Israel, one in 1990 and one in 1999, the virus was probably carried by vectors transported by air currents across the Rift Valley and through the Red Sea trough. The disease broke out under optimal ecological conditions among vulnerable cattle populations and spread rapidly; it developed in the spring and summer and ended soon after the daily average ambient temperature fell below 16 degrees C in late autumn. The proportion of herds affected reached 78.4 and 97.7 per cent in 1990 and 1999, respectively. The highest rates of incidence, morbidity and mortality were recorded in dairy cattle herds in the Jordan Valley, the initial focus of the outbreaks, with a morbidity of 20 and 38.6 per cent in 1990 and 1999, respectively, and mortality among the affected animals of 2 and 8.6 per cent in 1990 and 1999, respectively. In 1991, the disease recurred sporadically in the central and southern regions of Israel in only three herds, but in 2000 the disease returned on an epidemic scale, and 85 per cent of herds were affected, with morbidity and mortality rates of 4-3 and 0-3 per cent, respectively. In the 1999 epidemic, the morbidity rate decreased from 38-6 per cent on average in the Jordan Valley to 12.8 per cent in the inner valleys and 5.3 per cent on the Mediterranean coastal plain, but the mortality rate increased from 8-6 per cent in the Jordan Valley to 14-3 per cent in the inner valleys, and to 28 per cent on the Mediterranean coastal plain, where the outbreak declined. An average of 2-7 per cent of the animals experienced a second attack of the disease two to six weeks later. The epidemic in 2000 was milder and shorter than that in 1999. All the cattle affected in both outbreaks were more than three months old. The vector(s) is not known for certain but the available evidence indicates that mosquitoes, and not Culicoides species, are the natural vectors of BEF virus in Israel.

Age Factors↗
PubMed1970

Morphology and development of bovine ephemeral fever virus.

The development of the virus of bovine ephemeral fever in mouse brain has been studied by electron microscopy. The virus particles are bullet-shaped, 70 by 145 nm, and slightly tapered toward the rounded end. The outer envelope is closely apposed to an electron-dense shell, about 12 nm thick, but no other internal structure is visible. The virus strains studied bud from the marginal membranes of neurones, but intracytoplasmic development, possibly aberrant, was also observed with one strain. Ephemeral fever virus is thus obviously a rhabdovirus, with points of resemblance to vesicular stomatitis, Flanders-Hart Park, and Kern Canyon viruses on the one hand, and to rabies virus on the other, but is structurally distinct from any of these.

Animals↗
PubMed1989

The relationship between selenium deficiency and the development of pulmonary and subcutaneous emphysema in bovine ephemeral fever virus-infected cattle.

Bovine ephemeral fever (BEF) was diagnosed on several commercial farms around Harare, Zimbabwe. The affected animals showed signs of fever (40-41.5 degrees C), depression, ruminal stasis, lameness and recumbency. Eight of those attended had severe respiratory distress and subcutaneous emphysema. Haematological and biochemical results indicated leukocytosis with an attending lymphopaenia. Selenium deficiency was detected only in those animals which showed respiratory embarrassment and subcutaneous emphysema.

Animals↗
PubMed1991

Proteins of bovine ephemeral fever virus.

The proteins of bovine ephemeral fever virus (BEFV) were examined in purified virions and in infected BHK-21 cells. Five structural proteins were named L (180K), G (81K), N (52K), M1 (43K) and M2 (29K). The 81K G protein incorporated [3H]glucosamine, was removed from virions by treatment with Triton X-100 and bound monoclonal antibodies which were both neutralizing and protective. Treatment of virions with Triton X-100 and 0.2 to 1.0 M-NaCl progressively released L, M1 and M2. The N protein remained associated with nucleocapsids in up to 2.5 M-NaCl. The glycoprotein (G), nucleoprotein (N) and matrix protein (M2) were phosphorylated. In BEFV-infected BHK-21 cells, five virus-induced proteins were detected from 12 h post-infection. The L, N, M1 and M2 proteins corresponded to those detected in virions whereas the G protein existed in two forms. In tunicamycin-treated cells these occurred as 67K and 71K non-glycosylated precursors. In the absence of tunicamycin, 77K and 79K glycosylated forms were further modified to produce the 81K virion G protein and a 90K cell-associated form. Five viral proteins were also detected in cells infected with the closely related Berrimah virus; the Berrimah virus G protein was also present in two forms.

Animals↗