RESUMEN
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.
Asunto(s)
Brotes de Enfermedades , Virus Visna-Maedi , Animales , Noruega/epidemiología , Ovinos , Brotes de Enfermedades/veterinaria , Virus Visna-Maedi/aislamiento & purificación , Neumonía Intersticial Progresiva de los Ovinos/epidemiología , Neumonía Intersticial Progresiva de los Ovinos/virología , Enfermedades de las Ovejas/epidemiología , Enfermedades de las Ovejas/virologíaRESUMEN
Early and accurate diagnosis is fundamental for successful surveillance and control of maedi-visna virus (MVV). MVV was detected in Norway in 2019, almost 14 years after the previous outbreak. Genetic analysis indicates persistence of the virus in the sheep population since 2005. The virus was not detected despite continuous serological surveillance. This emphasises the need for improved surveillance, which relies on an understanding of both diagnostic test performance, sampling strategy and the prevalence of the disease. This study therefore aims to evaluate three commercial ELISA tests for MVV antibodies. We conducted a retrospective study using 615 samples from six flocks diagnosed with MVV in 2019. We ran all samples with the following three tests: ID Screen® MVV/CAEV Indirect (IDvet, Grabels, France), IDEXX MVV/CAEV p28 Ab Verification Test (IDEXX Laboratories, Maine, USA) and Elitest MVV/CAEV (Hyphen Biomed, Neuville-sur-Oise, France), hereinafter referred to as ID Screen, IDEXXp28 and Elitest respectively. Without a perfect reference test, we used Bayesian latent class analysis, including conditional dependence between tests, to estimate diagnostic accuracy and true prevalence in the flocks. Using recommended cut-off values, we found that ID Screen and Elitest had significantly higher sensitivity (Se) estimates (99.3 % [97.4-100.0, 95 % Posterior Credible Interval] and 97.4 % [94.1-99.7 %], respectively) than IDEXXp28 (79.5 % [72.3-86.0 %]), while IDEXXp28 and ID Screen had significantly higher specificity (Sp) estimates than Elitest (99.7 % [99.1-100.0], 99.1 % [98.0-99.8 %] and 93.7 % [91.4-95.7 %], respectively). The estimated true prevalence in the six flocks ranged from a median of 0.8-93.5 %. Combining ID Screen and Elitest in serial interpretation showed the highest median Se and Sp (96.7 % [92.0-99.1] and 100.0 % [99.9-100.0], respectively), as well as the highest median positive predictive value (PPV) for the population with the lowest prevalence. Our study supports the use of ID Screen for screening. Further verification with Elitest in serial interpretation will enhance the PPV.
Asunto(s)
Neumonía Intersticial Progresiva de los Ovinos , Enfermedades de las Ovejas , Virus Visna-Maedi , Ovinos , Animales , Análisis de Clases Latentes , Teorema de Bayes , Estudios Retrospectivos , Neumonía Intersticial Progresiva de los Ovinos/diagnóstico , Neumonía Intersticial Progresiva de los Ovinos/epidemiología , Ensayo de Inmunoadsorción Enzimática/veterinaria , Enfermedades de las Ovejas/diagnóstico , Enfermedades de las Ovejas/epidemiologíaRESUMEN
BACKGROUND: Escherichia coli infections known as colibacillosis constitute a considerable challenge to poultry farmers worldwide, in terms of decreased animal welfare and production economy. Colibacillosis is caused by avian pathogenic E. coli (APEC). APEC strains are extraintestinal pathogenic E. coli and have in general been characterized as being a genetically diverse population. In the Nordic countries, poultry farmers depend on import of Swedish broiler breeders which are part of a breeding pyramid. During 2014 to 2016, an increased occurrence of colibacillosis on Nordic broiler chicken farms was reported. The aim of this study was to investigate the genetic diversity among E. coli isolates collected on poultry farms with colibacillosis issues, using whole genome sequencing. METHODS: Hundred and fourteen bacterial isolates from both broilers and broiler breeders were whole genome sequenced. The majority of isolates were collected from poultry with colibacillosis on Nordic farms. Subsequently, comparative genomic analyses were carried out. This included in silico typing (sero- and multi-locus sequence typing), identification of virulence and resistance genes and phylogenetic analyses based on single nucleotide polymorphisms. RESULTS: In general, the characterized poultry isolates constituted a genetically diverse population. However, the phylogenetic analyses revealed a major clade of 47 closely related ST117 O78:H4 isolates. The isolates in this clade were collected from broiler chickens and breeders with colibacillosis in multiple Nordic countries. They clustered together with a human ST117 isolate and all carried virulence genes that previously have been associated with human uropathogenic E. coli. CONCLUSIONS: The investigation revealed a lineage of ST117 O78:H4 isolates collected in different Nordic countries from diseased broilers and breeders. The data indicate that the closely related ST117 O78:H4 strains have been transferred vertically through the broiler breeding pyramid into distantly located farms across the Nordic countries.