Investigation, management and control of a maedi outbreak in Norway in 2019-2020.

BACKGROUND: Visna-maedi is a notifiable disease in Norway, and eliminating the disease is a national goal. The import of sheep into Norway is very limited, and strict regulations apply to the movement of small ruminants between flocks and within defined geographical regions. Several outbreaks have occurred in the last 50 years, and the most recent before 2019 occurred in Trøndelag county in Central Norway in 2002. A national surveillance programme for small ruminant lentivirus infection exists since 2003. RESULTS: In 2019, the national surveillance programme detected seropositive animals for small ruminant lentivirus in a sheep flock in Trøndelag. Based on the result of polymerase chain reaction analysis and histopathological findings, the Norwegian Food Safety Authority concluded the diagnosis of maedi. Further investigations detected maedi in eight additional sheep flocks in the same county. The flocks were placed under restrictions, and the authorities also imposed restrictions on 82 contact flocks. Sequencing of partial gag genes indicated that the virus in the current outbreak was related to the small ruminant lentivirus detected in the same area between 2002 and 2005. CONCLUSIONS: The outbreak investigation shows the need for sensitive and specific diagnostic methods, and an improved and more targeted surveillance strategy. It also demonstrates the risk of disease spreading between flocks through animal movements, and highlights the importance of biosecurity and structured livestock trade. In addition to allowing livestock trade only from flocks documented free from maedi, it may be necessary to monitor sheep flocks over many years, when aiming to eliminate maedi from the Norwegian sheep population.

Racing-associated fatalities in Norwegian and Swedish harness racehorses: Incidence rates, risk factors, and principal postmortem findings.

BACKGROUND: There are no reports on the number of fatalities or causes of death in the Norwegian and Swedish harness racehorses. OBJECTIVES: The incidence rates (IRs), risk factors, and postmortem findings in horses that died or were euthanized associated with racing between 2014 and 2019 were investigated. ANIMALS: Thirty-eight Standardbreds and 10 Norwegian-Swedish Coldblooded Trotters died or were euthanized associated with racing. A total of 816 085 race-starts were recorded. METHODS: Incidence rates were calculated for both countries and horse breeds. Risk factors for sudden death were identified using a case-control logistic model. Postmortem examinations were performed in 43 horses. RESULTS: The overall fatality IR was 0.059/1000 race-starts. Traumatic injuries accounted for 14.5%, while sudden death for 85.5% of fatalities. Only minor differences between countries and breeds were recorded. The number of starts within the last 30 days increased the risk of sudden death (5 starts odds ratio (OR) 228.80, confidence interval (CI) 10.9-4793). An opposite non-linear effect was observed in number of starts the last 180 days (>10 starts OR 0.12, CI 0.02-0.68). Seven horses were euthanized because of catastrophic injury. Acute circulatory collapse because of suspected cardiac or pulmonary failure or both was recorded in 30 horses, while major hemorrhage after vessel rupture was the primary cause of death in 10 cases. One horse collapsed and died but was not submitted for autopsy. CONCLUSIONS AND CLINICAL IMPORTANCE: Comparatively low rates of catastrophic orthopedic fatalities were reported, while causes and IR of sudden death were similar to previous studies.

Experimental inoculation of chickens with gull-derived low pathogenic avian influenza virus subtype H16N3 causes limited infection.

The infectivity, transmission, and pathogenicity potential of avian influenza virus (AIV) subtype H16N3, isolated from the European herring gull (Larus argentatus), was examined in chickens. Nineteen 6-wk-old commercial Lohmann white chickens were inoculated intranasally with 1 x 10(6) 50% egg infectious dose and clinical signs, humoral immune response, virus shedding, virus transmission, and pathologic changes in the respiratory tract were studied. Oropharyngeal and cloacal swabs were collected for viral RNA detection by real-time reverse transcriptase-PCR (rRT-PCR). Sera were collected and examined for H16-specific antibodies using a hemagglutination inhibition test. Tissue samples from the nasal cavity, trachea, and lung were collected at postmortem examination for histopathology and viral RNA detection by rRT-PCR. In one bird, bilateral serous nasal discharge was observed at 2 days postinoculation (DPI) and viral RNA was detected in oropharyngeal swabs at 2 and 4 DPI. Viral RNA was also detected from the oropharynx of an additional bird at 5 DPI. Moreover, H16-specific antibodies were detected in sera from these two birds at 14 and 21 DPI. No viral RNA was detected from cloacal swabs, and no virus transmission between virus-inoculated chickens and noninoculated contact chickens was observed. Tissue samples from the nasal cavity, trachea and lung were negative for viral RNA and no gross or histopathologic lesions were observed in the virus-inoculated birds. These results indicate that gull-derived AIV subtype H16N3 causes only limited infection in chickens under experimental conditions.

An Official Outbreak Investigation of Acute Haemorrhagic Diarrhoea in Dogs in Norway Points to Providencia alcalifaciens as a Likely Cause.

An outbreak investigation was initiated in September 2019, following a notification to the Norwegian Food Safety Authority (NFSA) of an unusually high number of dogs with acute haemorrhagic diarrhoea (AHD) in Oslo. Diagnostic testing by reporting veterinarians had not detected a cause. The official investigation sought to identify a possible common cause, the extent of the outbreak and prevent spread. Epidemiological data were collected through a survey to veterinarians and interviews with dog owners. Diagnostic investigations included necropsies and microbiological, parasitological and toxicological analysis of faecal samples and food. In total, 511 dogs with acute haemorrhagic diarrhoea were registered between 1 August and 1 October. Results indicated a common point source for affected dogs, but were inconclusive with regard to common exposures. A notable finding was that 134 of 325 faecal samples (41%) cultured positive for Providencia alcalifaciens. Whole genome sequencing (WGS) of 75 P. alcalifaciens isolates from 73 dogs revealed that strains from 51 dogs belonged to the same WGS clone. Findings point to P. alcalifaciens as implicated in the outbreak, but investigations are needed to reveal the pathogenic potential of P. alcalifaciens in dogs and its epidemiology.

A descriptive study of acute outbreaks of respiratory disease in Norwegian fattening pig herds.

BACKGROUND: Respiratory diseases are major health concerns in the pig production sector worldwide, contributing adversely to morbidity and mortality. Over the past years there was a rise in reported incidents of respiratory disease in pigs in Norway, despite population wide freedom from Aujeszky´s disease, porcine reproductive and respiratory syndrome, porcine respiratory corona virus and enzootic pneumonia. The main objective of this study was to investigate acute outbreaks of respiratory disease in conventional Norwegian fattening pig herds. The study included 14 herds. In seven herds with reported outbreaks of acute respiratory disease, data on clinical signs was recorded and samples for laboratory examination were collected. Diagnostic protocols were compared by parallel analysis of clinically healthy pigs from seven non-outbreak herds. RESULTS: The most commonly reported clinical signs were sudden deaths and dyspnea. An average compartment morbidity of 60%, mortality of 4% and case fatality of 9% was recorded in the outbreak herds. Post-mortem examinations revealed acute lesions resembling porcine pleuropneumonia in all 28 pigs investigated from the outbreak herds and in 2 of the 24 (8%) pigs from the non-outbreak herds. Chronic lesions were recorded in another 2 pigs (8%) from the non-outbreak herds. Actinobacillus pleuropneumoniae serovar 8 was isolated from lungs and/or pleura from all tested pigs (n = 28) in the outbreak herds, and from 2 out of 24 pigs (8%) in the non-outbreak herds, one pig with an acute and another pig with a chronic infection. No other significant bacterial findings were made. Seroconversion to A. pleuropneumoniae antibodies was detectable in all outbreak herds analyzed and in six out of seven non-outbreak herds, but the risk ratio for seroconversion of individual pigs was higher (risk ratio 2.3 [1.50- 3.43 95% CI; P < 0.001]) in the outbreak herds. All herds tested positive for porcine circovirus type 2 and negative for influenza A viruses on oral fluid RT-qPCR. CONCLUSION: The main etiological pathogen found during acute outbreaks of respiratory disease was A. pleuropneumoniae serovar 8. All pigs from outbreak herds had typical lesions of acute porcine pleuropneumonia, and only A. pleuropneumoniae serovar 8 was identified. Co-infections were not found to impact disease development.

Natural killer cells in lymph nodes of healthy calves express CD16 and show both cytotoxic and cytokine-producing properties.

Natural killer (NK) cells were recently shown to play an important immunomodulatory role in lymph nodes. We here report the presence, phenotype and function of NK cells resident in lymph nodes of several anatomical sites of healthy calves. NKp46+/CD3-lymphocytes, recently demonstrated to precisely identify NK cells in all tested species, were present in the paracortex and the medulla of bovine lymph nodes. Most lymph node-derived NK cells expressed CD16 and perforin, and a lytic capacity was demonstrated, while a well-developed interferon-gamma response to interleukin-2 and interleukin-12 stimulation was also seen. Lymph node-derived NK cells differed from those in blood by a higher expression of the activation markers CD44 and CD25, as well as CD8. L-selectin (CD62L) was expressed by the majority of lymph node-derived NK cells, consistent with a dependency of this molecule for migration to lymph nodes. Unlike in blood, the majority of lymph node NK cells had little or no CD2 expression. Compared to available literature, calf lymph nodes contained NK cells in numbers equal to or higher than reported in humans, and clearly higher than in mice. These findings suggest a cytotoxic role of lymph node residing NK cells, beyond the predominantly cytokine-producing role previously inferred from studies on human NK cells.

Bilateral tympanokeratomas (cholesteatomas) with bilateral otitis media, unilateral otitis interna and acoustic neuritis in a dog.

BACKGROUND: An aural cholesteatoma, more appropriately named tympanokeratoma, is an epidermoid cyst of the middle ear described in several species, including dogs, humans and Mongolian gerbils. The cyst lining consists of stratified, keratinizing squamous epithelium with central accumulation of a keratin debris. This case report describes vestibular ganglioneuritis and perineuritis in a dog with chronic otitis, bilateral tympanokeratomas and presumed extension of otic infection to the central nervous system. CASE PRESENTATION: An 11-year-old intact male Dalmatian dog with chronic bilateral otitis externa and sudden development of symptoms of vestibular disease was examined. Due to the dog's old age the owner opted for euthanasia without any further examination or treatment and the dog was submitted for necropsy. Transection of the ears revealed grey soft material in the external ear canals and pearly white, dry material consistent with keratin in the tympanic bullae bilaterally. The brain and meninges were grossly unremarkable. Microscopical findings included bilateral otitis externa and media, unilateral otitis interna, ganglioneuritis and perineuritis of the spiral ganglion of the vestibulocochlear nerve and multifocal to coalescing, purulent meningitis. A keratinizing squamous epithelial layer continuous with the external acoustic meatus lined the middle ear compartments, consistent with bilateral tympanokeratomas. Focal bony erosion of the petrous portion of the temporal bone and squamous epithelium and Gram-positive bacterial cocci were evident in the left cochlea. The findings suggest that meningitis developed secondary to erosion of the temporal bone and ganglioneuritis and/or perineuritis of the vestibulocochlear nerve. CONCLUSIONS: Middle ear tympanokeratoma is an important and potentially life-threatening otic condition in the dog. Once a tympanokeratoma has developed expansion of the cyst can lead to erosion of bone and extension of otic infection to the inner ear, vestibulocochlear ganglion and nerve potentially leading to bacterial infection of the central nervous system.

Human to animal transmission of influenza A(H1N1)pdm09 in a turkey breeder flock in Norway.

Introduction: Routine surveillance samples disclosed seropositivity to influenza A virus (IAV) in a Norwegian turkey breeder flock. Simultaneous reports of influenza-like symptoms in farm workers and a laboratory confirmed influenza A(H1N1)pdm09 (H1N1pdm09) infection in one person led to the suspicion of a H1N1pdm09 infection in the turkeys. Animals and methods: H1N1pdm09 infection was confirmed by a positive haemaggutinin inhibition test using H1N1pdm09 antigens, and detection of H1N1pdm09 nucleic acid in reproductive organs of turkey hens. The flock showed no clinical signs except for a temporary drop in egg production. Previous reports of H1N1pdm09 infection in turkeys suggested human-to-turkey transmission (anthroponosis) during artificial insemination. Results and discussion: The flock remained seropositive to IAV and the homologous H1N1pdm09 antigen throughout the following 106 days, with decreasing seroprevalence over time. IAV was not detected in fertilised eggs or in turkey poults from the farm, however, maternally derived antibodies against H1N1pdm09 were found in egg yolks and in day-old poults. Genetic analyses of haemagglutinin gene sequences from one of the infected farm workers and turkeys revealed a close phylogenetic relationship, and confirmed human-to-turkey virus transmission.

Establishment of Mycobacterium avium subsp. paratuberculosis infection in the intestine of ruminants.

Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) is the cause of paratuberculosis, which is a chronic enteritis of ruminants characterized by granulomatous inflammation. The transmission of the infection is mainly by faecal contaminated feed. The bacteria are transported from the intestinal lumen into the intestinal wall via M cells, which overlie the domes of Peyer's patches. It is proposed that integrin receptors on the apical surface of M cells bind fibronectin-opsonized bacteria, facilitating phagocytosis by these cells. After crossing the epithelial barrier of the intestine, the bacteria are phagocytosed by macrophages, which are the target cell for this microorganism. Macrophages internalize the bacteria by binding to different receptors, including the complement receptor 3, and phagosomes containing the organisms are formed. Macrophages can destroy M. a. paratuberculosis, but not by way of oxidative compounds. The bacteria manipulate macrophages in order to survive, inhibiting the maturation and acidification of the phagosomes, and modulating macrophage cytokine production and antigen-presentation.

Comparison of flow cytometry and image morphometry in the quantitative analysis of cell population markers in the lymph node of sheep.

Two approaches to the quantitative analysis of cell population markers in tissues are flow cytometry and image morphometry. To compare these methods, sheep lymph nodes were collected and analysed for CD8+ and CD21+ cell populations, which were selected to represent dispersed and concentrated cell populations, respectively. These two populations were measured as a percentage of total cell count (flow) or total tissue area (morphometry). The two populations were also measured as a percentage of respective base populations (CD2+ cells for CD8 and MHC II+ cells for CD21). A simple linear regression analysis showed that when the cell populations were assessed as a percentage of total cell count or total area, measurements obtained with flow and morphometry only correlated significantly with the dispersed CD8+ population and not with the highly concentrated CD21+ population. However, when the cell populations were assessed as a percentage of their base population, measurements obtained with flow and morphometry showed a significant correlation for both the dispersed and concentrated cell populations. This study demonstrates that measurements of lymph node cell populations obtained with the two methods are comparable, but that tissue distribution of cell populations should be considered, when the unit of measurement is chosen.

Early responses of natural killer cells in pigs experimentally infected with 2009 pandemic H1N1 influenza A virus.

Natural killer (NK) cells are important players in the innate immune response against influenza A virus and the activating receptor NKp46, which binds hemagglutinin on the surface of infected cells, has been assigned a role in this context. As pigs are natural hosts for influenza A viruses and pigs possess both NKp46- and NKp46+ NK cells, they represent a good animal model for studying the role of the NKp46 receptor during influenza. We explored the role of NK cells in piglets experimentally infected with 2009 pandemic H1N1 influenza virus by flow cytometric analyses of cells isolated from blood and lung tissue and by immunostaining of lung tissue sections. The number of NKp46+ NK cells was reduced while NKp46- NK cells remained unaltered in the blood 1-3 days after infection. In the lungs, the intensity of NKp46 expression on NK cells was increased during the first 3 days, and areas where influenza virus nucleoprotein was detected were associated with increased numbers of NKp46+ NK cells when compared to uninfected areas. NKp46+ NK cells in the lung were neither found to be infected with influenza virus nor to be undergoing apoptosis. The binding of porcine NKp46 to influenza virus infected cells was verified in an in vitro assay. These data support the involvement of porcine NKp46+ NK cells in the local immune response against influenza virus.

Faecal shedding detected earlier than immune responses in goats naturally infected with Mycobacterium avium subsp. paratuberculosis.

Paratuberculosis was diagnosed in a goat herd that participated in a sanitation program against Mycobacterium avium subsp. paratuberculosis. The aim of this study was to characterise the development of gamma interferon (IFN-γ) and antibody responses as well as the occurrence of faecal shedding. Faecal culture appeared surprisingly sensitive as about 18% and 40% of the goats were positive at 9 and 15-17 months of age, respectively, and shedding was often seen prior to peripheral immune responses. Peripheral IFN-γ responses were not related to protection as clinical and high shedding goats often had high responses. An IFN-γ response usually preceded a humoral response. However, positive antibody titers could sometimes be seen simultaneously with, and even prior to, IFN-γ responses. In conclusion, faecal culture appeared as sensitive as IFN-γ testing. Furthermore, the antibody ELISA and the IFN-γ assay may perform equally well in an infected herd if surveillance is conducted annually.

Pathological Findings and Distribution of Pandemic Influenza A (H1N1) 2009 Virus in Lungs from Naturally Infected Fattening Pigs in Norway.

The Norwegian pig population was considered free from influenza A virus infections until the first case of porcine pandemic influenza A (H1N1) 2009 virus infection in October 2009. Human to pig transmission of virus was suspected. Unusual lung lesions were observed in fattening pigs, with red, lobular, multifocal to coalescing consolidation, most frequently in the cranial, middle, and accessory lobes. The main histopathological findings were epithelial degeneration and necrosis, lymphocyte infiltration in the epithelial lining and lamina propria of small bronchi and bronchioles, and peribronchial and peribronchiolar lymphocyte infiltrations. Infection with pandemic influenza A (H1N1) 2009 virus was confirmed by real-time RT-PCR and immunohistochemical detection of influenza A virus nucleoprotein in the lesions. This investigation shows that natural infection with the pandemic influenza A (H1N1) 2009 virus induces lung lesions similar to lesions described in experimental studies and natural infections with other swine-adapted subtypes of influenza A viruses.

Polymorphisms at codons 141 and 154 in the ovine prion protein gene are associated with scrapie Nor98 cases.

Until June 2004, thirty-eight scrapie cases with unusual features, designated Nor98, have been diagnosed in Norway. This study investigated the distribution of PrP genotypes among Nor98 cases, their flock-mates and a random sample of Norwegian slaughtered sheep. The PrP genotype distribution of Nor98 cases differed markedly from that of previous cases of classical scrapie. A leucine/phenylalanine polymorphism at codon 141 with hitherto unknown significance to scrapie was strongly associated with Nor98 cases. Twenty of 38 (52.6 %) cases were either homozygous or heterozygous for phenylalanine at codon 141. In contrast, this allele was present in only 10.5 % of the flock-mates and 4.5 % of the random sample of slaughtered sheep. Moreover, the H(154) allele was represented in 24 of 38 (63.2 %) of Nor98 cases, as opposed to 27.0 % of Nor98 flock-mates and 17.0 % of the slaughtered sheep.