Marks Fernanda S, Rodenbusch Carla R, Okino Cíntia H, Hein Héber E, Costa Eduardo F, Machado Gustavo, Canal Cláudio W, Brentano Liana, Corbellini Luís G
Laboratório de Epidemiologia Veterinária, EPILAB, Universidade Federal do Rio Grande do Sul, UFRGS, Brazil.
Laboratório de Virologia, Universidade Federal do Rio Grande do Sul, UFRGS, Brazil.
Prev Vet Med. 2014 Sep 1;116(1-2):197-202. doi: 10.1016/j.prevetmed.2014.06.001. Epub 2014 Jun 10.
Newcastle disease virus (NDV) causes a fast-spreading, highly contagious infectious disease in several bird species. Commercial poultry farms in Brazil were considered free of virulent NDV. Data on NDV infection levels in backyard poultry flocks and the epidemiology of the disease are limited. The aim of this study was to perform a NDV survey in backyard poultry from households flocks located around one of the main wintering sites for migratory wild birds in Brazil, and to identify potential risk factors associated with NDV. Backyard poultry may be sentinels and a source of infection for commercial poultry, since they may have as much contact with these birds as with migratory wild birds. Data were collected from 48 randomly selected households using an epidemiological questionnaire. Serum samples from poultry were tested for NDV antibodies using an ELISA, and tracheal and cloacal swabs were collected for NDV molecular detection. The risk factors were assessed using a multivariate Poisson regression with robust variance. The ELISA showed that 33.8% of the serum samples were positive for anti-NDV antibodies and in 42 households (87.5%) at least one NDV-positive bird was found. Tracheal and cloacal swabs were negative for NDV by real time RT-PCR, possible because within this region there might flow a low pathogenicity NDV strain, which can induce seroconversion with innaparent clinical findings. The prevalence ratio (PR) increased when farmers used their own replacement poultry to restock their flock (PR=1.64; 95% CI: 1.11-2.42). Furthermore, the increasing distance of the household flock from the "Laguna do Peixe" estuary was associated with decreasing NDV seropositivity (PR=0.94; 95% CI: 0.90-0.99). This is the first study in Brazil evaluating the presence of NDV and the associated risk factors in households with backyard poultry flocks. The great number of farms with seropositive birds indicates that the virus circulates in backyard flocks, and this breeding system may be a source of NDV. These data can be used to establish appropriate biosecurity and husbandry measures for this type of breeding system to prevent NDV spread in Brazil.
新城疫病毒（NDV）在多种鸟类中引发一种传播迅速、高度传染性的疾病。巴西的商业家禽养殖场曾被认为没有强毒力新城疫病毒。关于后院家禽群中新城疫病毒感染水平及该疾病流行病学的数据有限。本研究的目的是对位于巴西主要候鸟越冬地之一周边家庭饲养的后院家禽进行新城疫病毒调查，并确定与新城疫病毒相关的潜在风险因素。后院家禽可能是商业家禽的哨兵和感染源，因为它们与这些家禽以及候鸟接触的机会一样多。使用流行病学调查问卷从48个随机选择的家庭收集数据。采用酶联免疫吸附测定法（ELISA）检测家禽血清样本中的新城疫病毒抗体，并采集气管和泄殖腔拭子用于新城疫病毒的分子检测。使用具有稳健方差的多元泊松回归评估风险因素。酶联免疫吸附测定法显示33.8%的血清样本抗新城疫病毒抗体呈阳性，在42户家庭（87.5%）中发现至少一只新城疫病毒阳性家禽。气管和泄殖腔拭子经实时逆转录聚合酶链反应（RT-PCR）检测新城疫病毒呈阴性，可能是因为该地区可能传播低致病性新城疫病毒株，其可在无明显临床症状的情况下诱导血清转化。当农户使用自家留种家禽补充鸡群时，患病率比（PR）升高（PR =
1.64；95%置信区间：1.11 - 2.42）。此外，家庭鸡群距离“佩克西泻湖”河口的距离增加与新城疫病毒血清阳性率降低相关（PR = 0.94；95%置信区间：0.90 - 0.99）。这是巴西首次评估后院家禽群中新城疫病毒的存在情况及相关风险因素的研究。大量血清阳性家禽的养殖场表明该病毒在后院鸡群中传播，并且这种养殖系统可能是新城疫病毒的一个来源。这些数据可用于为这类养殖系统制定适当的生物安全和饲养措施，以防止新城疫病毒在巴西传播。
