Respiratory disease and increased mortality occurred in minks on two farms in the Netherlands, with interstitial pneumonia and SARS-CoV-2 RNA in organ and swab samples. On both farms, at least one ...worker had coronavirus disease-associated symptoms before the outbreak. Variations in mink-derived viral genomes showed between-mink transmission and no infection link between the farms. Inhalable dust contained viral RNA, indicating possible exposure of workers. One worker is assumed to have attracted the virus from mink.
Brucella canis had not been isolated in the Netherlands until November 2016, when it was isolated from a dog imported from Romania. Including this case, 16 suspected cases were notified to the ...authorities during the following 25 months. Of these 16 dogs, 10 were seropositive; tracking investigations found another 8 seropositive littermates. All seropositive animals were rescue dogs imported from Eastern Europe. B. canis was cultured from urine, blood, and other specimens collected from the dogs. Genotyping of isolates revealed clustering by litter and country. Isolating B. canis in urine indicates that shedding should be considered when assessing the risk for zoonotic transmission. This case series proves introduction of B. canis into a country to which it is not endemic through import of infected dogs from B. canis–endemic areas, posing a threat to the naive autochthonous dog population and humans.
Organisms of the genus Bonamia are intracellular protistan parasites of oysters. To date, 4 species have been described (B. ostreae, B. exitiosa, B. perspora and B. roughleyi), although the status of ...B. roughleyi is controversial. Introduction especially of B. ostreae and B. exitiosa to naïve host populations has been shown to cause mass mortalities in the past and has had a dramatic impact on oyster production. Both B. ostreae and B. exitiosa are pathogens notifiable to the World Organisation for Animal Health (OIE) and the European Union. Effective management of the disease caused by these pathogens is complicated by the extensive nature of the oyster production process and limited options for disease control of the cultured stocks in open water. This review focuses on the recent advances in research on genetic relationships between Bonamia isolates, geographical distribution, susceptible host species, diagnostics, epizootiology, host-parasite interactions, and disease resistance and control of this globally important genus of oyster pathogens.
One of the most valuable aquaculture fish in Europe is the rainbow trout, Oncorhynchus mykiss, but the profitability of trout production is threatened by a highly lethal infectious disease, viral ...hemorrhagic septicemia (VHS), caused by the VHS virus (VHSV). For the past few decades, the subgenogroup Ia of VHSV has been the main cause of VHS outbreaks in European freshwater-farmed rainbow trout. Little is currently known, however, about the phylogenetic radiation of this Ia lineage into subordinate Ia clades and their subsequent geographical spread routes. We investigated this topic using the largest Ia-isolate dataset ever compiled, comprising 651 complete G gene sequences: 209 GenBank Ia isolates and 442 Ia isolates from this study. The sequences come from 11 European countries and cover the period 1971-2015. Based on this dataset, we documented the extensive spread of the Ia population and the strong mixing of Ia isolates, assumed to be the result of the Europe-wide trout trade. For example, the Ia lineage underwent a radiation into nine Ia clades, most of which are difficult to allocate to a specific geographic distribution. Furthermore, we found indications for two rapid, large-scale population growth events, and identified three polytomies among the Ia clades, both of which possibly indicate a rapid radiation. However, only about 4% of Ia haplotypes (out of 398) occur in more than one European country. This apparently conflicting finding regarding the Europe-wide spread and mixing of Ia isolates can be explained by the high mutation rate of VHSV. Accordingly, the mean period of occurrence of a single Ia haplotype was less than a full year, and we found a substitution rate of up to 7.813 × 10-4 nucleotides per site per year. Finally, we documented significant differences between Germany and Denmark regarding their VHS epidemiology, apparently due to those countries' individual handling of VHS.
Two mass mortality events (MMEs) of marine mussels that took place in the Oosterschelde, the Netherlands—the first in 2015/2016 and the second in 2019—both severely affected mussel production. The ...current study presents our observations on the onset and course of both MMEs and discusses probable putative causes. The two MMEs displayed a distinct course of events. The first event started in November 2015 with high mortality rates on culture plots, which remained elevated until the autumn of 2016. Approximately 40–50% of mussels from all age classes were lost on culture plots and 100% were lost from wild seed beds. The second event started in April–May 2019 and continued until the end of July, with mortality ranging from 20 to 100%, again from all age classes. Culture areas other than the Oosterschelde and other shellfish species were not affected. Histological and bacteriological screening produced no evidence for common pathogens or pollution as a primary mortality factor and there is no indication of abnormal environmental conditions preceding or during the events. We hypothesize that a cumulation of stressors results in weakening of the mussels and in elevated mortality rates. In 2019, this cumulation of stressors could be high spawning activities (an unusual high concentration of mussel larvae was found in April) that resulted in very low condition from April to June, a
Phaeocystis
bloom in April to May that prevented a quick recovery, and the development of granulocytomas that were found in up to 60 to 70% of live mussels as a consequence of cumulative stress. Although no (single) putative causes could be identified, this study contributes to the knowledge on MMEs in mussels and fits in a wider and disturbing trend on mortality events in shellfish.
The Baltic tellin Limecola balthica is one of the most common bivalves in intertidal areas in the Northern Hemisphere. Over the last 2 decades, the species has been suffering from a decrease in adult ...survival in the European Wadden Sea. While several factors such as global warming and fisheries have been suggested to influence the population dynamics of this bivalve mollusc, the potential role of diseases has never been investigated. In this study, we investigated whether disseminated neoplasia, a common proliferative disorder in bivalve molluscs, could play a potential role in the recent population decline of Baltic tellins in the Wadden Sea. We conducted a field survey in the Dutch Wadden Sea to (1) determine whether the disease occurs in Baltic tellins in the Wadden Sea and (2) quantify the occurrence and severity of the disease via histology. Disseminated neoplasia occurred in L. balthica at each of the 10 sampled locations with very high prevalences (21-89%) compared to those reported elsewhere for this species. The highest severity category was found in 8 to 87% of affected individuals, with severity generally increasing with prevalence. Disseminated neoplasia usually increases mortality among affected individuals and may also be associated with important sub-lethal effects, especially regarding gametogenesis. Thus, we suggest that disseminated neoplasia may play a key role in the population dynamics of the Baltic tellin, the extent of which remains to be investigated in future studies.
A Brucella suis biovar 1 infection was diagnosed in a dog without typical exposure risks, but the dog had been fed a raw meat-based diet (hare carcasses imported from Argentina). Track and trace ...investigations revealed that the most likely source of infection was the dog's raw meat diet.
Analysis of low pathogenic avian influenza (LPAI) viruses circulating in the Netherlands in a previous study revealed associations of specific hemagglutinin (HA) and neuraminidase (NA) subtypes with ...wild bird or poultry hosts. In this study, we identified putative host associations in LPAI virus internal proteins. We show that LPAI viruses isolated from poultry more frequently carried the allele A variant of the nonstructural protein (NS) gene, compared to wild bird viruses. We determined the susceptibility of chickens to wild bird-associated subtypes H3N8 and H4N6 and poultry-associated subtypes H8N4 and H9N2, carrying either NS allele A or B, in an infection experiment. We observed variations in virus shedding and replication patterns, however, these did not correlate with the predicted wild bird- or poultry-associations of the viruses. The experiment demonstrated that LPAI viruses of wild bird-associated subtypes can replicate in chickens after experimental infection, despite their infrequent detection in poultry. Although the NS1 protein is known to play a role in immune modulation, no differences were detected in the limited innate immune response to LPAI virus infection. This study contributes to a better understanding of the infection dynamics of LPAI viruses in chickens.
Cyprinid herpesvirus 3 (CyHV-3) or koi herpesvirus (KHV) is a devastating virus of carp. Using generic primers for the DNA polymerase and the major capsid protein genes of cyprinid herpesviruses, ...nucleotide sequences divergent from previously described CyHV-3 were obtained. At least 3 novel groups of putative CyHV-3-like viruses were identified, sharing 95 to 98% nucleotide identity with CyHV-3 strains. Carp carrying the CyHV-3 variants did not show clinical signs consistent with CyHV-3 infection and originated from locations with no actual CyHV-3 outbreaks. These strains might represent low- or non-pathogenic variants of CyHV-3.
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•A competitive real-time PCR assay has been developed for Marteilia refringens detection.•Such assay allow discrimination between “M” and “O” genotypes of M. refringens.•The method is ...rapid, sensitive and specific with high repeatability and efficiency.•It will facilitate studies on epidemiology of the parasite, geographical distribution and host specificity.
Species belonging to the genus Marteilia are protozoan parasites of bivalves. The species Marteilia refringens, jeopardizing the health of European bivalves, is included on the list of OIE notifiable pathogens. Two genotypes of Marteilia refringens are distinguished: type “O” affecting mainly oysters, and type “M” affecting mainly mussels. Historically, detection of Marteilia species is primarily carried out by histology. In recent years molecular assays are more frequently used for the detection of mollusc pathogens, also in routine monitoring. In the present work, a competitive real-time PCR assay was developed for rapid and sensitive detection of M. refringens and discrimination between “M” and “O” genotypes of M. refringens. The real-time PCR assay was shown to be analytically sensitive and specific and has a high repeatability and efficiency. Subsequent application of the assay on collected bivalves from two geographical locations, the Ebro Delta in Mediterranean Spain and the Rhine-Meuse Delta in the Netherlands resulted in detection of M. refringens type M in Mytilus galloprovincialis and M. refringens type O in Ostrea edulis from Spain. In two O. edulis specimen both M. refringens type O and type M were detected. In the Netherlands M. refringens was not observed in any of the tested Mytilus edulis and O. edulis. The results obtained by real time PCR were in correspondence with the results obtained by histopathology and a substantial agreement with the results obtained by conventional PCR.
In conclusion, the developed real time PCR assay facilitates rapid detection and subtyping of M. refringens and could be applied for further studies on epidemiology of the parasite, geographical distribution and host specificity.
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