Serological and Virological Studies of Newcastle Disease and Avian Influenza in Slaughter-Age Ostriches (Struthio camelus) in Japan

Abstract

ABSTRACT. Serum samples from 191 ostriches (Struthio camelus) in Japan were tested for antibodies to Newcastle disease virus (NDV) and avian influenza virus (AIV). Twenty-two (12%) contained NDV-specific neutralizing antibodies by a virus-neutralization (VN) test without vaccination. Antibodies to AIV were not detected in the any sera by an agar gel precipitation test. Seven serum samples that had vaccinated with live NDV by eye drop were all positive by the VN test at 1 month post vaccination. A haemagglutination inhibition (HI) test for NDV seemed not to be suitable for ostriches because of non-specific agglutination of chicken red blood cells. No haemagglutinating viruses were isolated. This is the first report on detection of antibodies against NDV in ostriches in Japan. KEY WORDS: Newcastle disease, ostrich, serological survey.

Situation of Serum Antibodies against Newcastle Disease Virus in Slaughter-Age Ostriches after Vaccination Campaign in Japan

“…In the countries that are leading producers and major exporters of ostrich products such as South Africa, it is important to reduce the risk of NDV transmission by effective vaccination. In Japan, commercial ostriches were introduced in 1988 and the number was increased to around 10,000 ostriches by 2002 [21,22]. Because of their size and natural environment, ostriches are inevitably reared outdoors, and this means they are likely to come into contact with viruses and other organisms infecting wild birds and other animals.…”

“…There is increasing impetus by ostrich producers in Japan to establish preventive medicine practices such as ND vaccination, disease monitoring and surveillance. Previously we demonstrated antibodies to NDV in ostriches in Japan [22] and Japan Ostrich Council (JOC) started ND vaccine campaign for commercial ostrich farms since 2004. The objectives of this study are therefore to provide serological surveillance information, determine the prevalence of antibodies to NDV in commercially raised slaughter-age ostriches and deduce about vaccination situation on ostrich farms after the campaign.…”

“…The neutralizing antibody titer was calculated at 50% plaque reduction point by Behrens-Kaerber's method [17]. The titers equal to or greater than log 2 2 were considered positive result [22].…”

“…In case these ostriches were infected with virulent NDV, we should expect high level (more than 100) of VN titer or observe some clinical sign of disease. Alongside, Sakai et al [22] reported there were three of 10 ostrich serum samples collected from livestock hygiene service centers that showed high level of VN titer (171, 250, and 1990), and they assumed that these ostriches might have been infected with virulent NDV. According to information from these centers, ND outbreaks had occurred in chicken farms near the farms that these ostriches were kept.…”

“…Although ND vaccination schedule of JOC was set up for 6 times at the first year old and booster every 6 months for attenuated vaccine by eye drop or combination with inactivated vaccine, most farmers still do not follow that schedule. Before JOC introduced the ND vaccination programs to commercial ostrich, Sakai et al [22] found 22 (12.15%) of 181 slaughter age ostriches had VN titer even without vaccination during 2002-2004. Six (3.3%) samples showed VN titer as middle and 5 (2.8%) as high.…”