Epidemiology of pseudorabies in intensive pig farms in Shanghai, China: Herd-level prevalence and risk factors

Abstract

Pseudorabies (PR), also known as Aujeszky's disease, is a highly contagious disease affecting pigs and a wide range of animals. Pseudorabies is enzootic in many countries. In China, it is a priority animal disease for control and eradication, however the data on disease frequency in intensive pig farms and the information on associated risk factors is inadequate. A cross-sectional study of intensive pig farms (≥350 sows) in Shanghai was conducted to determine herd-level prevalence of PRV and associated risk factors. Following a two-stage random sampling design, a total of 1,349 sow serum samples were tested by gpI-ELISA from a total of 91 intensive pig farms in Shanghai. A herd was classified as positive if at least one PRV test-positive sow was present. Information on putative risk/protective factors was collected using questionnaires to pig farm owners or veterinarians. A logistic regression model was built to identify risk/protective factors for herd positivity. The results indicated that the herd-level true prevalence was 67.6% (95% CI：57.0 -77.0). In the multivariable logistic regression model using backward stepwise procedure, two risk factors were found to be significantly associated with herd positivity: 'Breeding with introduced sows in the last 12 months' (OR=3.5, 95%CI:1.2, 10.3) and 'Presence of stray dogs or cats' (OR=4.0, 95%CI: 1.2, 12.6). The multivariable logistic model fitted the data well. Hosmer-Lemeshow goodness of fit test showed  2 = 10.86 (df = 8, p = 0.21 > 0.05) and the predictability (area under the ROC curve) was 0.86. This study suggested that PR was highly endemic in intensive pig farms in Shanghai. The risk and protective factors identified in this study could be useful to improve the prevention policy of PR in Shanghai and other areas of China.

Prevalence of Porcine Pseudorabies Virus and Its Coinfection Rate in Heilongjiang Province in China from 2013 to 2018

“…In this study, 18,815 serum samples of pigs in different production phases were collected from pig farms in eight investigated cities in Heilongjiang province, and were subsequently examined by ELISA on an annual basis to investigate gB-and gE-specific antibody level and SPR. Consistent with results of previous publications (7,14,19,21), >80% of pigs were vaccinated in the investigated farms in Heilongjiang province, according to the higher level of PRV gB SPR rates described in Table 1 from 2013 to 2018. Moreover, S/N ratio of different investigated herds showed lower than 0.6, ranging from 0.17 to 0.54.…”

Epidemiological Investigation and Genetic Analysis of Pseudorabies Virus in Yunnan Province of China from 2017 to 2021

“…An investigation of the prevalence of PRV is required to build up strategies to control and even eradicate PR and minimize the risk of humans contacting this infectious pathogen. Though the prevalence and genetic characteristics of PRV have been documented in several regions or provinces of China [ 2 , 3 , 10 , 11 ], the relevant information in Yunnan Province in recent years is still not available. To fill in this gap, 20,158 pig serum samples were collected from 2017 to 2021 to investigate the epidemiology of PRV in Yunnan Province.…”

Prevalence of Porcine Pseudorabies Virus and Its Coinfection Rate in Heilongjiang Province in China from 2013 to 2018

“…In this study, 18,815 serum samples of pigs in different production phases were collected from pig farms in eight investigated cities in Heilongjiang province, and were subsequently examined by ELISA on an annual basis to investigate gB-and gE-specific antibody level and sero-prevalence rate (SPR).Consistent with results of previous publications [10,[13][14][15], more than80% of pigs were vaccinated in the investigated farms in Heilongjiang province, according to the higher level of PRV-gB SPR rates described in Table 1 (Table 4). Previous studies conducted in Shandong province in China have shown that a high proportion of pigs were latently infected by PRV in the investigated region [16,17], which was recognized to be the most critical source of infection when the latent viral genome is reactivated [5].…”