Cross-sectional study on risk factors associated with porcine epidemic diarrhea virus infection in pig farms in Junan county, China

Porcine epidemic diarrhea (PED) is a highly contagious, intestinal infectious disease in pigs, characterized by severe diarrhea, vomiting and dehydration. PED is widely epidemic in China as well as in many eastern Asian and America countries, causing tremendous losses in pig industry. However, little was known about the disease frequency and the associated risk factors of PED in pig farms. A cross-sectional study was conducted to estimate the herd prevalence and to identify the potential risk factors of porcine epidemic diarrhea virus (PEDV) infection of pig farms (≥100 pigs) in Junan county, China. A two-stage random sampling strategy was adopted, and a total of 751 fecal samples from suckling piglets of 82 farms were collected and tested by RT-PCR and sequencing for PEDV. Meanwhile, information on the putative risk factors of PEDV infection of those farms were collected in forms of questionnaires, followed by a descriptive analysis, univariable and multivariable logistic regression analysis. The results showed that the herd-level true prevalence of PEDV infection of pig farms in Junan was 35.16 % (95 %CI: 22.91-53.89); there were two variables significantly associated with PEDV infection, which were 'having more than 1000 slaughter pigs per annum' (OR = 5.42, 95 %CI: 1.19-24.72), and 'Weaning at 21-25 days' old' (OR = 4.50, 95 %CI:1.25-16.20). The research suggested that PED was highly endemic in pig farms in Junan county; larger herd size and weaning at an earlier age were potential risk factors associated with PEDV infection in pig farms in Junan. This study set an example in the research on herd-level prevalence of PEDV infection and risk factors associated with PEDV infection, and the results were of practical significance for the future planning of prevention and control of PED in Junan or other areas of China.

High herd-level seroprevalence and associated factors for bovine leukemia virus in the semi-arid Paraíba state, Northeast Region of Brazil

Epidemiological surveys that investigate infectious diseases such as enzootic bovine leukosis (EBL) are important. Furthermore, estimating the prevalence of such infectious diseases and associated factors is key to assess the disease impact and design control programs. In this study, we identified a high herd-level seroprevalence of EBL in cattle from the semi-arid Paraíba state, Northeast Region of Brazil, using a planned cross-sectional survey. Herd-level and animal-level prevalence were estimated using a two-stage random sampling survey. In total, 2067 cows aged ≥24 months from 400 herds were sampled. An enzyme-linked immunosorbent assay was used to detect specific antibodies directed to the bovine leukosis virus gp51 antigen in both individual and pooled sera. The herd-level and animal-level prevalence was 23.4 % (95 % CI = 19.2-28.1 %) and 10.8 % (95 % CI = 7.5 %-15.3 %), respectively. There were no significant clusters of positive herds (within a radius of 2 km). The factors associated with herd-level prevalence were the exclusive use of hand milking (prevalence ratio [PR] = 1.88), herd size (PR = 1.005), artificial insemination (PR = 2.03), purchase of animals in the previous year (PR = 1.87), and peri-urban farms (PR = 2.09). Prevention measures should be applied at the herd-level, particularly for farms located in peri-urban areas, focusing on good hygiene in hand milking, robust practices and standards for artificial insemination, and serological testing of animals prior to purchase.

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

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 1349 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 χ² = 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.