The protective effectiveness of an inactivated bovine ephemeral fever virus vaccine.

Bovine ephemeral fever (BEF) is an important viral disease of cattle. Despite the extensive use of inactivated vaccines for the prevention of BEF, a controlled study of their field effectiveness has never been performed. We conducted a large field effectiveness study of a BEF inactivated vaccine, during a large BEF outbreak. Neutralizing antibody titers measured in 385 heifers and calves 1 month after 2(nd) vaccination averaged 1:91.8 (CI95%=76.6-110). The effectiveness study enrolled 2780 cows in nine herds. In two herds cows vaccinated twice, 1 year before the outbreak and once 2-3 months before outbreak onset were compared with non-vaccinated cows. Average vaccine effectiveness of three vaccine doses compared to no vaccination was 47% (CI95%=34-57) in these herds. In two other herds cows vaccinated twice 1 year before the outbreak and twice again 2-3 months before outbreak were compared with cows vaccinated only twice 2-3 months prior to the outbreak. Average vaccine effectiveness of four doses compared to two doses was 49% (CI95%=25-65) in these herds. In five herds cows vaccinated twice 2-3 months before outbreak onset were compared with non-vaccinated cows. This vaccination schedule was shown to be non-effective (average effectiveness=2%, CI95%=-14-17). Milk production analysis on one of the effected herds, in which 56% vaccine effectiveness and an absolute reduction of 27% in morbidity were documented, revealed a net milk production loss of 175.9kg/sick cow (CI95%=127.9-223.9) and an average gain of 37kg for each vaccinated cow (CI95%=-3.6-77.7). This study indicates that despite the fact that two vaccine doses of the tested inactivated vaccine elicited high titers of neutralizing antibodies, partial protection was induced only when at least 3 doses were administrated before natural challenge.

Safety, immunogenicity and duration of immunity elicited by an inactivated bovine ephemeral fever vaccine.

Bovine ephemeral fever (BEF) is an economically important viral vector-borne cattle disease. Several live-attenuated, inactivated and recombinant vaccines have been tested, demonstrating varying efficacy. However, to the best of our knowledge, duration of immunity conferred by an inactivated vaccine has never been reported. In the last decade, Israel has faced an increasing number of BEF outbreaks. The need for an effective vaccine compatible with strains circulating in the Middle East region led to the development of a MONTANIDE™ ISA 206 VG (water-in-oil-in-water), inactivated vaccine based on a local strain. We tested the safety, immunogenicity and duration of immunity conferred by this vaccine. The induced neutralizing antibody (NA) response was followed for 493 days in 40 cows vaccinated by different protocols. The vaccine did not cause adverse reactions or a decrease in milk production. All cows [except 2 (6.7%) which did not respond to vaccination] showed a significant rise in NA titer of up to 1:256 following the second, third or fourth booster vaccination. Neutralizing antibody levels declined gradually to 1:16 up to 120 days post vaccination. This decline continued in cows vaccinated only twice, whereas cows vaccinated 3 or 4 times showed stable titers of approximately 1:16 for up to 267 days post vaccination. At least three vaccinations with the inactivated BEF vaccine were needed to confer long-lasting immunity. These results may have significant implications for the choice of vaccination protocol with inactivated BEF vaccines. Complementary challenge data should however be added to the above results in order to determine what is the minimal NA response conferring protection from clinical disease.

A reverse-transcription PCR method for detecting all known ephemeroviruses in clinical samples.

Bovine ephemeral fever virus (BEFV) is an economically important vector-borne pathogen of cattle in tropical and sub-tropical regions of Australia, Asia, Africa and the Middle East. Although clinical cases of bovine ephemeral fever are usually attributed to BEFV, definitive diagnosis is rarely performed and at least two other related viruses, kotonkon virus (KOTV; an ephemerovirus) and Fukuoka virus (FUKAV; an unassigned rhabdovirus), can cause similar clinical signs. As vaccines have been developed against BEFV but not against KOTV or FUKAV, a test capable of detecting and differentiating these pathogens would be useful. In the present study, an RT-PCR method using degenerate primers designed to a region of block III of the polymerase (L) gene was developed and optimised for primer annealing temperature and MgCl2 concentration. The RT-PCR detected all known ephemeroviruses and several other closely related insect-transmitted rhabdoviruses, including FUKAV. Viruses could be identified by subsequent sequencing and phylogenetic analysis of the amplicons. BEFV could be detected using tissue culture isolates or cattle blood to a sensitivity of 500 RNA copies per reaction. This test will be useful for establishing the identity of the causative agent of bovine ephemeral fever from field samples and cultured isolates.

Circulation of bovine ephemeral fever in the Middle East--strong evidence for transmission by winds and animal transport.

Bovine ephemeral fever virus (BEFV) is an economically important arbovirus of cattle. The main routes of its transmission between countries and continents are not completely elucidated. This study aimed to explore BEFV transmission in the Middle-East. A phylogenetic analysis was performed on the gene encoding the G protein of BEFV isolates from Israel from 2000 and 2008 with isolates from Turkey (2008), Egypt (2005), Australia (1968-1998) and East Asia (1966-2004). Calf sera collected during the years 2006-2007 were tested by serum neutralization in order to explore for recent exposure to BEFV before 2008. These were followed by a meteorological analysis, aimed to reveal movement of air parcels into Israel in the two weeks preceding the first case of BEF in Israel in 2008. The 2008 Israeli and Turkish isolates showed 99% identity and formed a new cluster with the 2000 Israeli isolate. The serological survey showed no new exposure to BEFV during 2006 and 2007. These results coincided with the meteorological analysis, which revealed that air parcels originating in Southern Turkey had reached the location of outbreak onset in Israel nine days before the discovery of the index case. The Egyptian isolate clustered phylogenetically with the Taiwanese isolates, coinciding with data on importation of cattle from China to the Middle East in the year preceding the isolation of the Egyptian isolates. These results suggest that both winds and animal transport may have an important role in trans-boundary transmission of BEFV.