Virological and Histopathological Findings in Boars Naturally Infected With Porcine Reproductive and Respiratory Syndrome Virus Type 1.

Major geographical transmission of porcine reproductive and respiratory syndrome virus (PRRSV) occurs via semen when a boar stud is infected. This happened in Denmark in 2019, providing an opportunity to compare previous experimental PRRSV boar studies with natural PRRSV-1 infection in boars. The aim of this study was to investigate the association between the presence of PRRSV RNA in serum, semen, testicles, and epididymis of boars naturally infected with PRRSV and to describe the histological lesions in the testes and epididymis combined with direct visualisation of PRRSV-infected cells by immunohistochemical staining (IHC). The exact timing of infection of each boar was not determined, but based on serology the boars were divided into two groups: acute and late infections. All boars included were sampled the same day. In this study, 35 boars and 10 healthy boars from another PRRSV-negative boar stud were included as histological controls. PRRSV RNA was found most often in serum (51%) and least frequently in semen (22%) and was more often detected in the reproductive tract in the acute phase of infection (p < 0.0001; RR: 2.58). Mononuclear cells and multinuclear giant cells were present in the adluminal compartment of the testis and epididymis in PRRSV-infected boars, but not in control boars (p < 0.05), which supports the hypothesis that macrophages are involved in the venereal spread of the virus.

Post-weaning diarrhea in pigs weaned without medicinal zinc: risk factors, pathogen dynamics, and association to growth rate.

BACKGROUND: Porcine post-weaning diarrhea (PWD) has reemerged as an important topic in pig production, as common control strategies based on prophylactic use of antimicrobials and zinc oxide have been deemed unsustainable. The objectives of this study were to estimate the cumulative incidence of porcine post-weaning diarrhea with different etiologies in production systems weaning without zinc oxide and prophylactic antimicrobials, to assess risk factors for post-weaning diarrhea, and to estimate the impact of post-weaning diarrhea on growth rate. A cohort study was conducted at two commercial indoor producers weaning without medicinal zinc oxide and prophylactic antimicrobials. RESULTS: Piglets were included at birth (n = 300) and 272 survived until weaning. After insertion to the nursery units, the piglets were clinically examined every day for 14 days, and rectal swabs were collected and analyzed for enterotoxigenic Escherichia coli (ETEC) and rotavirus A. The cumulative incidences of PWD the first 14 days after insertion to the nursery units were 41.8% (CI 33.6, 50.4) and 51.1% (CI 42.3, 60.0) at the two producers, respectively. We found a low incidence of cases associated to ETEC, and detected a substantial proportion of cases associated to rotavirus. We observed a biphasic pattern in the assumed etiology with rotavirus occurring first, and then a shift towards cases associated to ETEC/non-ETEC hemolytic E. coli. Being offspring of older sows was a protective factor for the development of PWD (Hazard ratio = 0.88 [CI 0.78, 0.99] per unit increase in parity of the dam). Low birth weight reduced the post-weaning growth rate (- 5.2 g/day [CI - 7.5, - 2.9] per 100 g decrease in birthweight) and increased the hazard of developing PWD (Hazard ratio for birthweight below 1100 g: 2.30 [CI 1.41-3.74]). The combined effect of having diarrhea for 2 days or more and receiving antimicrobial treatment was associated with an increased average daily weight gain. CONCLUSIONS: This study suggests novel insights regarding pathogen dynamics and risk factors for PWD in productions not using prophylactic antimicrobials and medicinal zinc. The findings may have important implications for both antimicrobial usage and prevention strategies.

Effect of two methods and two anaesthetics for local anaesthesia of piglets during castration.

BACKGROUND: Since January 2019, surgical castration of male piglets must be performed using local anaesthesia, if farmers deliver pigs to the primary exporting slaughterhouses according to the "Danish quality scheme"; a voluntary initiative taken by the Danish pig industry. The approved procedure for local anaesthesia in Denmark is a three-step injection method with procaine. A comparison of lidocaine and procaine with the same concentration and injection methods of local anaesthetics has not previously been studied. The purpose of this study was to investigate the effect of two injection methods and two local anaesthetics on piglets' avoidance behaviour (vocalisation and resistance movements) as well as the time spent on the procedures. The study included 203 male piglets that were randomly assigned to one of five treatments: 1. CONTROL: Sham-handling without injection of local anaesthesia, 2. Pro3: Procaine injection using a three-step method, 3. Pro2: Procaine injection using a two-step method, 4. Lid3: Lidocaine injection using a three-step method, 5. Lid2: Lidocaine injection using a two-step method. During injection of local anaesthesia and castration, vocalisation was measured using a decibel meter and resistance movements were registrated by video recordings. RESULTS: During castration, piglets treated with local anaesthesia showed significantly reduced vocalisation and resistance movements and time spent on castration was also significantly reduced compared to the control group. During injection of the local anaesthesia, the piglets had significantly increased vocalisation and resistance movements compared to the control group. Piglets injected with lidocaine had a significantly reduced resistance movement score and a tendency to reduced vocalisation compared to piglets injected with procaine. No differences in avoidance behaviour were found between the injection methods. CONCLUSIONS: The use of local anaesthesia, irrespective of the method and local anaesthetic, was effective in reducing vocalisation and resistance movements during surgery as well as the time spent on castration.

Controlling Transmission of MRSA to Humans During Short-Term Visits to Swine Farms Using Dust Masks.

The aim of the investigation was to determine the protective effect of wearing dust masks to prevent Methicillin-resistant Staphylococcus aureus (MRSA) contamination during a short-term visit in a MRSA-positive swine farm. A total of 118 human volunteers were randomly allocated to a group wearing masks and to the control group. On average, 9% of the participants wearing masks were MRSA-positive when leaving the farm compared to 62% of the participants not wearing masks. At day 1, 2, and 7 after the farm visit, none of those wearing masks were MRSA-positive. An odds ratio of 18.9 (CI: 6.4-56.2) for being MRSA-positive was found for those not wearing masks compared to those wearing masks when including the farm as random effect. None of the covariates (gender, age, and smoking) influenced the OR for being MRSA-positive when leaving the farm. This study shows that the use of dust masks gives a significant protection against nasal MRSA contamination after a short-term visit to a swine farm. In addition, 106 volunteers not wearing masks were investigated in order to provide an estimate of a contamination dose of airborne MRSA. Due to the high variation in the MRSA measurements, it was not possible to establish a stable estimate for this. Out of the 106 volunteers not wearing masks, 6, 7, and 3% tested MRSA-positive 1, 2, and 7 days after the farm visit, respectively.