The importance of the domestic pig reservoir for Hepatitis E virus (HEV) was assessed by estimating the seroprevalence and prevalence of HEV contaminated livers in French slaughter-aged pigs. 6565 sera and 3715 livers were randomly sampled from 186 pig farms throughout the country. Taking the sampling design into account, the farm-level seroprevalence was 65% (95% CI 57-74) and 31% (95% CI 24-38) of the slaughter-aged pigs had antibodies against HEV. The individual prevalence of HEV RNA positive livers was 4% (95% CI 2-6) and 24% (95% CI 17-31) of the farms had at least 1 positive liver. Most isolates were of genotype 3f (76.7%) with smaller amounts of 3c (18.6%) and 3e (4.6%). The high prevalence of HEV in pigs and the similarities between HEV subtypes from pigs and humans corroborates the possible zoonotic origin of some HEV autochthonous infections.

Concomitant infections by different influenza A virus subtypes within pig farms increase the risk of new reassortant virus emergence. The aims of this study were to characterize the epidemiology of recurrent swine influenza virus infections and identify their main determinants. A follow-up study was carried out in 3 selected farms known to be affected by repeated influenza infections. Three batches of pigs were followed within each farm from birth to slaughter through a representative sample of 40 piglets per batch. Piglets were monitored individually on a monthly basis for serology and clinical parameters. When a flu outbreak occurred, daily virological and clinical investigations were carried out for two weeks. Influenza outbreaks, confirmed by influenza A virus detection, were reported at least once in each batch. These outbreaks occurred at a constant age within farms and were correlated with an increased frequency of sneezing and coughing fits. H1N1 and H1N2 viruses from European enzootic subtypes and reassortants between viruses from these lineages were consecutively and sometimes simultaneously identified depending on the batch, suggesting virus co-circulations at the farm, batch and sometimes individual levels. The estimated reproduction ratio R of influenza outbreaks ranged between 2.5 [1.9-2.9] and 6.9 [4.1-10.5] according to the age at infection-time and serological status of infected piglets. Duration of shedding was influenced by the age at infection time, the serological status of the dam and mingling practices. An impaired humoral response was identified in piglets infected at a time when they still presented maternally-derived antibodies.

Hepatitis E virus (HEV) can cause enterically-transmitted hepatitis in humans. The zoonotic nature of Hepatitis E infections has been established in industrialized areas and domestic pigs are considered as the main reservoir. The dynamics of transmission in pig herds therefore needs to be understood to reduce the prevalence of viremic pigs at slaughter and prevent contaminated pig products from entering the food chain. An experimental trial was carried out to study the main characteristics of HEV transmission between orally inoculated pigs and naïve animals. A mathematical model was used to investigate three transmission routes, namely direct contact between pigs and two environmental components to represent within-and between-group oro-fecal transmission. A large inter-individual variability was observed in response to infection with an average latent period lasting 6.9 days (5.8; 7.9) in inoculated animals and an average infectious period of 9.7 days (8.2; 11.2). Our results show that direct transmission alone, with a partial reproduction number of 1.41 (0.21; 3.02), can be considered as a factor of persistence of infection within a population. However, the quantity of virus present in the environment was found to play an essential role in the transmission process strongly influencing the probability of infection with a within pen transmission rate estimated to 2 ⋅ 10− 6g ge− 1d− 1(1 ⋅ 10− 7; 7 ⋅ 10− 6). Between-pen environmental transmission occurred to a lesser extent (transmission rate: 7 ⋅ 10− 8g ge− 1d− 1(5 ⋅ 10− 9; 3 ⋅ 10− 7) but could further generate a within-group process. The combination of these transmission routes could explain the persistence and high prevalence of HEV in pig populations.

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The frequency of sporadic cases of hepatitis E in humans in developed countries has increased in recent years. The consumption of raw or undercooked pig liver-based products has been identified as an important source of human infection. The question of possible massive human exposure to this zoonotic agent has been raised by the high prevalence of hepatitis E virus (HEV) in swine herds. However, little is known about the epidemiology of HEV on pig farms. A retrospective study, based on a previous prevalence study of 185 farms, was conducted on 90 farms located in Western France, randomly selected from this database, to identify factors associated with the presence of HEV in pig livers and HEV seroprevalence in slaughter-age pigs. At least one HEV RNA-positive liver was found in 30% of the sampled farms while seroprevalence in slaughter-age pigs at the farm level reached almost 75%. Different factors were associated with the two conditions. The risk of having HEV-positive livers was increased by early slaughter, genetic background, lack of hygiene measures and surface origin of drinking water. High HEV seroprevalence was associated with mingling practices at the nursery stage and hygiene conditions. These results can be used to determine on-farm measures to reduce within-farm HEV spread and infection of slaughter-age pigs.

We investigated the impact of the hatchery practice of administering third-generation cephalosporin (3GC) on the selection and persistence of 3GC-resistant Escherichia coli in poultry. We studied 15 3GC-treated (TB) and 15 non-3GC-treated (NTB) broiler flocks and 12 3GC-treated (TL) and 10 non-3GC-treated (NTL) future layer flocks. Fecal samples from each flock were sampled before arrival on the farm (day 0), on day 2, on day 7, and then twice more. E. coli isolates were isolated on MacConkey agar without antibiotics and screened for 3GC resistance, and any 3GC-resistant E. coli isolates were further analyzed. 3GC-resistant E. coli isolates were found in all 3GC-treated flocks on at least one sampling date. The percentages of 3GC-resistant E. coli isolates were significantly higher in TB (41.5%) than in NTB (19.5%) flocks and in TL (49.5%) than in NTL (24.5%) flocks. In the day 2 samples, more than 80% of the E. coli strains isolated were 3GC resistant. 3GC-resistant E. coli strains were still detected at the end of the follow-up period in 6 out of 27 3GC-treated and 5 out of 25 non-3GC-treated flocks. Many 3GC-resistant E. coli strains were resistant to tetracycline, and there were significant differences in the percentages of resistance to sulfamethoxazoletrimethoprim, streptomycin, or gentamicin between treated and nontreated flocks. bla CTX-M and bla CMY-2 were the most frequently detected genes. These results clearly demonstrated that 3GC-resistant strains are introduced early in flocks and that the use of 3GC in hatcheries promotes the selection of 3GC-resistant E. coli. Measures must be implemented to avoid the spread and selection of 3GC-resistant strains.T hird-generation cephalosporins (3GC) have been classified as "critically important antimicrobials" in human medicine by the World Health Organization. In many European countries, there has been a dramatic increase in the prevalence of 3GC-resistant Escherichia coli in broilers and broiler meat (1-3), and these isolates are considered of public health concern.Several studies have suggested a possible link between use of 3GC in hatcheries and the increase in 3GC resistance in E. coli. The presence of these resistant isolates in the broiler production pyramid has been recently demonstrated (2, 4). 3GC antimicrobials are sometimes used to control the early mortality rate associated with E. coli. It is automatically administered in ovo to broilers (5) or by subcutaneous injection to 1-day-old future layers (6), together with Marek's disease vaccination. It is strongly suspected that use at hatcheries is responsible for the increase in 3GC resistance in poultry production (3,7,8). However, to our knowledge, no direct evidence of this potential cause-effect relationship has been published.The purpose of this study was to investigate the impact of hatchery use of 3GC on the selection and persistence of 3GC-resistant E. coli in poultry intestinal flora throughout the lifetime of the birds, by comparing flocks of broilers and future laying hens (layers) that ha...

In developed countries, most of hepatitis E human cases are of zoonotic origin. Swine is a major hepatitis E virus (HEV) reservoir and foodborne transmissions after pork product consumption have been described. The risk for HEV-containing pig livers at slaughter time is related to the age at infection and to the virus shedding duration. Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a virus that impairs the immune response; it is highly prevalent in pig production areas and suspected to influence HEV infection dynamics. The impact of PRRSV on the features of HEV infections was studied through an experimental HEV/PRRSV co-infection of specific-pathogen-free (SPF) pigs. The follow-up of the co-infected animals showed that HEV shedding was delayed by a factor of 1.9 in co-infected pigs compared to HEV-only infected pigs and specific immune response was delayed by a factor of 1.6. HEV shedding was significantly increased with co-infection and dramatically extended (48.6 versus 9.7 days for HEV only). The long-term HEV shedding was significantly correlated with the delayed humoral response in co-infected pigs. Direct transmission rate was estimated to be 4.7 times higher in case of co-infection than in HEV only infected pigs (0.70 and 0.15 per day respectively). HEV infection susceptibility was increased by a factor of 3.3, showing the major impact of PRRSV infection on HEV dynamics. Finally, HEV/PRRSV co-infection – frequently observed in pig herds – may lead to chronic HEV infection which may dramatically increase the risk of pig livers containing HEV at slaughter time.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0207-y) contains supplementary material, which is available to authorized users.

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