A cross-sectional study of swine influenza in intensive and extensive farms in the northeastern region of the state of São Paulo, Brazil

Farm management practices, biosecurity and influenza a virus detection in swine farms: a comprehensive study in colombia

Biosecurity protocols (BP) and good management practices are key to reduce the risk of introduction and transmission of infectious diseases into the pig farms. In this observational cross-sectional study, survey data were collected from 176 pig farms with inventories over 100 sows in Colombia. We analyzed a complex survey dataset to explore the structure and identify clustering patterns using Multiple Correspondence Analysis (MCA) of swine farms in Colombia, and estimated its association with Influenza A virus detection. Two principal dimensions contributed to 27.6% of the dataset variation. Farms with highest contribution to dimension 1 were larger farrow-to-finish farms, using self-replacement of gilts and implementing most of the measures evaluated. In contrast, farms with highest contribution to dimension 2 were medium to large farrow-to-finish farms, but implemented biosecurity in a lower degree. Additionally, two farm clusters were identified by Hierarchical Cluster Analysis (HCA), and the odds of influenza A virus detection was statistically different between clusters (OR 7.29, CI: 1.7,66, p = < 0.01). Moreover, after logistic regression analysis, three important variables were associated with higher odds of influenza detection: (1) “location in an area with a high density of pigs”, (2) “farm size”, and (3) “after cleaning and disinfecting, the facilities are allowed to dry before use”. Our results revealed two clustering patterns of swine farms. This systematic analysis of complex survey data identified relationships between biosecurity, husbandry practices and influenza status. This approach helped to identify gaps on biosecurity and key elements for designing successful strategies to prevent and control swine respiratory diseases in the swine industry.

The epidemiology of swine influenza

Globally swine influenza is one of the most important diseases of the pig industry, with various subtypes of swine influenza virus co-circulating in the field. Swine influenza can not only cause large economic losses for the pig industry but can also lead to epidemics or pandemics in the human population. We provide an overview of the pathogenic characteristics of the disease, diagnosis, risk factors for the occurrence on pig farms, impact on pigs and humans and methods to control it. This review is designed to promote understanding of the epidemiology of swine influenza which will benefit the control of the disease in both pigs and humans.

Health profile of free-range wild boar (Sus scrofa) subpopulations hunted in Santa Catarina State, Brazil

Wild boars represent a potential dissemination source of important pathogens to public and animal health, since they can host several pathogens. This study aimed to evaluate the health profile of wild boars hunted for population control in the state of Santa Catarina (SC), south of Brazil. For this study, tissue and blood samples were collected from 61 wild boars hunted from October 2017 to November 2018. All 61 serum samples were screened for antibodies by different assays, presenting the following seroprevalence: 52.4% for porcine circovirus type 2 (PCV2); 21.3% for Leptospira spp.; 19.7% for Mycoplasma hyopneumoniae; 13.1% for hepatitis E virus (HEV); and 9.8% for influenza A virus (IAV). No seroreaction was observed for Brucella spp. and classical swine fever virus (CSFV). At necropsy, the main lesions observed were evidence of pulmonary metastrongylid parasites, haemorrhagic lymph nodes and white-spotted liver. Histopathological analyses mainly showed interstitial pneumonia, bronchopneumonia and bronchi-associated lymphoid tissue (BALT) hyperplasia. There was a significant association between metastrongylid parasitism and BALT hyperplasia in lungs. Pathological findings of wild boars indicate that the assessed individuals were not exposed to notifiable diseases, such as CSFV, African swine fever virus and foot-and-mouth disease, which cause economic damage by non-tariff trade barriers. However, the detection of antibodies against PCV2 and M. hyopneumoniae, pathogens that impact commercial production, indicates the circulation of these agents, with frequency variation in wild populations. This shows the potential risk of pathogen transmission among domestic swine populations and free-living ones. The detection of antibodies against zoonotic agents such as HEV, IAV and Leptospira spp., other than characterizing the pathogens' circulation in these populations, suggests a potential risk to public health and pig farming, depending on the interactions established with the environment, humans and domestic swine.

No effects of noncytopathic bovine viral diarrhea virus type 2 on the reproductive tract of experimentally inoculated boars

Bovine viral diarrhea virus (BVDV) infections in pigs may result in transient leukopenia, chronic gastroenteritis, septicemia, and hemorrhagic lesions. Both classical swine fever virus (CSF) and the atypical porcine pestivirus (APPV) are shed in the semen of infected boars. Because these viruses share conserved regions and present antigenic similarity, they may not be the only species belonging to the genus Pestivirus that can be shed in the semen of infected pigs. The objective of this study was to evaluate the testicular and epididymal changes, seminal parameters, and viral shedding in the reproductive tract of boars experimentally inoculated with noncytopathic BVDV-2. Six males were selected, and samples of blood, semen, and preputial swabs were collected every four days until the 52nd day after inoculation. The samples were tested for the presence of viral RNA by RT-PCR. An aliquot of whole blood was used to perform hematological analyses, which showed a significant reduction in monocyte counts and a significant increase in lymphocyte counts when comparing the pre- and postinoculation periods. The neutralizing antibody titers were determined by the virus neutralization test. None of the animals presented clinical signs or worsening of the seminal parameters that were evaluated. Moreover, BVDV-2 shedding by the reproductive route was not observed.

Prevalence, distribution and risk factors of farmer reported swine influenza infection in Guangdong Province, China

A cross-sectional study was undertaken to better understand the husbandry, management and biosecurity practices of pig farms in Guangdong Province (GD), China to identify risk factors for farmer reported swine influenza (SI) on their farms. Questionnaires were administered to 153 owners/managers of piggeries (average of 7 from each of the 21 prefectures in GD). Univariable and multivariable logistic regression analyses were used to identify risk factors for farmer reported SI in piggeries during the six months preceding the questionnaire administration. The ability of wild birds to enter piggeries (OR 2.50, 95% CI: 1.01-6.16), the presence of poultry on a pig-farm (OR 3.24, 95% CI: 1.52-6.94) and no biosecurity measures applied to workers before entry to the piggery (OR 2.65, 95% CI: 1.04-6.78) were found to increase the likelihood of SI being reported by farmers in a multivariable logistic regression model. The findings of this study highlight the importance of understanding the local pig industry and the practices adopted when developing control measures to reduce the risk of SI to pig farms.

Biosecurity practices associated with influenza A virus seroprevalence in sows from southern Brazilian breeding herds

Influenza A virus (IAV) infection is a recognized cause of acute respiratory disease in pigs that can culminate in the decline of performance due to increasing feed conversion and costs of antimicrobial drugs to control secondary infections. Biosecurity practices are the key to prevent transmission of highly contagious agents. The aim of this study was to assess the effect of biosecurity practices on IAV seroprevalence through a cross-sectional study carried out in 404 sows from 21 herds. An indirect ELISA was used to detect antibodies against a nucleoprotein of IAV. To evaluate IAV subtypes (H1N1pdm09, H1N2 and H3N2), all samples positive by ELISA were tested using the hemagglutination inhibition assay (HI). Prevalence ratios (PR) estimates were calculated using multivariate Poisson regression accounted with survey weights. Sixty-four percent (261/404) of sows were positive in the rNP-ELISA and the estimated prevalence was 63.9% (95% CI 55%-73%). All farms had at least one seropositive sow; the frequency of IAV subtypes found in seropositive sows was 51.9% for H1N1pdm09, 38.1% for codetection H1N1pdm09 and H1N2, 8.6% for H1N2, and 0.6% for codetection H1N1pdm09 and H3N2, and 19 herds presented coinfection of H1N1 pdm09 and H1N2. Variables significantly associated with IAV seroprevalence found in the final model were 'bird-proof net' (PR = 0.75; 95% CI: 0.65-0.86) and 'gilt acclimatization unit' (PR = 0.57, 95% CI: 0.50-0.66), showing a protective effect against IAV seroprevalence, and 'external replacement', which had a positive effect on IAV seroprevalence (PR = 1.38, 95% CI: 1.17-1.64). This study suggests that preventing contact among wild species and swine and using an adaptation area for animals before entry into the herd can be strategies to control the influenza virus in breeding herds.

Serological surveillance and factors associated with influenza A virus in backyard pigs in Southern Brazil

Backyard pig populations are not monitored for influenza A virus (IAV) in Brazil and there are limited data about seroprevalence and risk factors in these populations. Our goal was to assess possible factors associated with IAV seroprevalence in backyard pig populations using an indirect ELISA protocol based on a recombinant nucleoprotein. Following the IAV screening using NP-ELISA, subtype-specific serology based on hemagglutination inhibition (HI) assay of the ELISA-positive pigs was conducted. The survey comprised a total of 1,667 sera samples collected in 2012 and 2014 in 479 holdings and the estimated seroprevalence was 5.3% (3.84%-7.33%) and 2.3% (1.34%-3.71%) in the respective years. In both years, H1N1pdm09 was the most prevalent subtype. The multivariable analysis showed main factors such as "age," "sex," "number of suckling pigs" and "neighbours raising pigs" that presented the greatest effect on IAV seroprevalence in these pig populations. These factors may be associated with the low biosecurity measures and management of backyard holdings. In addition, the low IAV seroprevalences found in these backyard pig populations could be related to a low number of animals in each pig holding and low animal movement/replacement that do not favour IAV transmission dynamics. This low frequency of H1N1pdm09 seropositive pigs could also be due to sporadic human-to-pig transmission of what is now a human seasonal influenza A virus; however, these factors should be explored in future studies. Herein, these results highlight the importance of IAV continued surveillance in backyard pig holdings, since it is poorly known which IAVs are circulating in these populations and the risk they could pose to public health and virus transmission to commercial farms.

Limited awareness of animal influenza prevention and control among Dai Lue smallholder farmers in Southwest China

Awareness of animal influenza and its prevention and control is important for ensuring livestock health, production and welfare. In China, a country stereotyped as a major source of emerging zoonotic infectious diseases, research on the public understanding of animal influenza is limited to the Han, the main ethnic group. The present qualitative study in Southwest China investigated awareness of animal influenza among the Dai, an ethnic minority. The participants (15 men and 10 women, ages 18–83) were smallholder farmers of pigs and poultry in rural areas of Jinghong, Xishuangbanna, Yunnan Province. A mixture of interviews and group discussions took place in homes and villages. The participants were asked about their knowledge of avian influenza (H7N9), swine influenza (H1N1), precautions taken to protect against influenza, procedures when animals were sick and perceived risk of animal influenza. The data were analysed following coding and thematic analysis. The findings demonstrated a limited understanding of animal health and welfare among participants. Specifically, they were largely unaware of animal influenza (H7N9, H1N1) including its causes, symptoms, prevention and treatment. The farmers were also uninformed of the risks they faced and unknowingly engaged in behaviours which increased direct or indirect exposure to infected animals, a risk factor for human infection. They also reported poor usage of veterinary services. In order to guarantee the health, welfare and production of their livestock, immediate action is needed to enable Dai smallholder farmers to prevent and respond to animal influenza effectively and timely.