Susceptibility and pathology in juvenile atlantic cod gadus morhua to a marine viral haemorrhagic septicaemia virus isolated from diseased rainbow trout oncorhynchus mykiss

The first known outbreak caused by a viral haemorrhagic septicaemia virus (VHSV) strain of genotype III in rainbow trout occurred in 2007 at a marine farm in Storfjorden, Norway. The source of the virus is unknown, and cod and other marine fish around the farms are suspected as a possible reservoir. The main objective of this study was to test the susceptibility of juvenile Atlantic cod to the VHSV isolate from Storfjorden. As the pathology of VHS in cod is sparsely described, an additional aim of the study was to give a histopathological description of the disease. Two separate challenge experiments were carried out, using both intra peritoneal (ip) injection and cohabitation as challenge methods. Mortality in the ip injection experiment leveled at approximately 50% three weeks post challenge. Both immunohistochemical and rRT-PCR analysis of organs sampled from diseased and surviving fish confirmed VHSV infection. No VHSV was detected in the cohabitants. The results indicate that Atlantic cod has a low natural susceptibility to this VHSV genotype III strain. One of the most extensive pathological changes was degeneration of cardiac myocytes. Immunohistochemistry confirmed that the lesions were related to VHSV. In some fish, the hematopoietic tissue of spleen and kidney showed degeneration and immunostaining, classical signs of VHS, as described in rainbow trout. Positive immunostaining of the capillaries of the gills, suggests this organ as a useful alternative when screening for VHSV.publishedVersio

Bovine respiratory syncytial virus in experimentally exposed and rechallenged calves; viral shedding related to clinical signs and the potential for transmission

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Barrier treatment with fipronil to control desert locust Schistocerca gregaria (Forskäl, 1775) hopper bands infesting a large area in Mauritania

Fipronil, a compound belonging to a new chemical family, the phenylpyrazols, was tested as a barrier treatment in Mauritania against bands of hoppers of the desert locust (#Schistocerca gregaria#, Forskal1775). An ultra-low volume formulation (ADONIS 12.5UL) was applied at 15.7 and 16.6/km. The doses were 1.96 and 1.04 g ai/ protected ha. Two sites of approximately 2800 and 7200 ha were sprayed from a helicopter flying at 20m. There were 12 track spacings, ranging from 330m to 2600m. The effects of fipronil on hopper bands were determined by comparison with the initial locust populations at the two sites. Several hopper bands were monitored in two untreated areas. The hopper bands were controlled within two days in the area up to 500m from the flight path, within 7 days in the area between 1000 and 2000m, and within 12 days in the area between 2000 and 2600m. The speed of mortality was related to the upwind distance from the flight path. When ADONIS 12.5UL (12.5g ai/l of fipronil) is applied at 16 l/km, at 20m height, with track spacings up to 1000m, the efficacy was similar to that obtained with a blanket treatment (11 g ai/ha) performed the previous year in Mauritania (Author's abstract

Bovine respiratory syncytial virus in experimentally exposed and rechallenged calves; viral shedding related to clinical signs and the potential for transmission

publishedVersio

High prevalence of viral haemorrhagic septicaemia virus (VHSV) in Norwegian spring‑spawning herring

Viral haemorrhagic septicaemia (VHS) is a viral disease known to cause high mortality in many teleost species, both in wild and farmed populations. The effects of this virus infection on the population dynamics of Atlantic herring Clupea harengus are still unknown; however, high mortalities have been reported in infected Pacific herring C. pallasii. We investigated Atlantic herring from the Norwegian spring-spawning (NSS) stock during the spawning season and found a much higher prevalence of VHS virus (VHSV) than had been identified in previous surveillance studies. Positive results were found in 19% of the samples analysed using viral cell culture on pooled brain, spleen and kidney tissue samples from 5 fish. Real-time RT-PCR performed on the same pooled samples revealed 33% positive samples, while analysis of individual organs resulted in a prevalence of 12-13%. Gills, which were analysed only by real-time RT-PCR, displayed a prevalence of 69%. It is not clear whether the virus detected in the gills reflects an infection or a passive carrier status. Sequencing of positive samples from gills and internal organs revealed high identity levels with VHSV of genotype Ib detected previously in Norwegian herring. The high prevalence identified in our study indicates a need for further research into the significance of VHSV infection on the herring population.2018-03-2