Azmi Al-Jubury

Effects of adjuvant Montanide™ ISA 763 A VG in rainbow trout injection vaccinated against Yersinia ruckeri

Enteric redmouth disease (ERM) caused by the fish pathogen Yersinia ruckeri is a major threat to freshwater production of rainbow trout (Oncorhynchus mykiss) throughout all life stages. Injection vaccination of rainbow trout against Y. ruckeri infection has been shown to confer better protection compared to the traditionally applied immersion vaccination. It may be hypothesized, based on experience from other vaccines, that adjuvants may increase the protective level of ERM injection vaccines even more. Controlled comparative vaccination studies have been performed to investigate effects of the oil adjuvant Montanide™ ISA 763 A VG (Seppic) when added to an experimental Y. ruckeri bacterin (containing both biotype 1 and 2 of serotype O1). A total of 1000 fish with mean weight 19 g was divided into five different groups (in duplicated tanks 2 × 100 fish per group) 1) non-vaccinated control fish (NonVac), 2) fish injected with a commercial vaccine (AquaVac(®) Relera™) (ComVac), 3) fish injected with an experimental vaccine (ExpVac), 4) fish injected with an experimental vaccine + adjuvant (ExpVacAdj) and 5) fish injected with adjuvant alone (Adj). Injection of the experimental vaccine (both adjuvanted and non-adjuvanted) induced a significantly higher antibody (IgM) level, increased occurrence of IgM(+) cells in spleen tissue and significant up-regulation of several immune genes. Additional experiments using a higher challenge dosage suggested an immune enhancing effect of the adjuvant as the challenge produced 100% mortality in the NonVac group, 60% mortality in both of ComVac and Adj groups and only 13 and 2.5% mortalities in the ExpVac and the ExpVacAdj groups, respectively.

Host size-dependent anisakid infection in Baltic cod Gadus morhua associated with differential food preferences.

A significant increase in the infection level of Baltic cod Gadus morhua with the anisakid nematode larvae Contracaecum osculatum and Pseudoterranova decipiens has been recorded during recent years due to the expanding local population of grey seals Halichoerus grypus, which act as final hosts for these parasites. Here, we report from an investigation of 368 cod (total length [TL] 6-49 cm; caught in ICES Subdivision 25) that the infection level of juvenile cod (TL 6-30 cm) with larvae of C. osculatum and P. decipiens is absent or very low, whereas it increases drastically in larger cod (TL 31-48 cm). A third nematode Hysterothylacium aduncum was rarely found. The study indicates that the prey animals for large cod act as transport hosts for the parasite larvae. Analyses of stomach contents of cod caught in the same area (2007-2014) showed that small benthic organisms (including polychaetes Harmothoë sarsi) are preferred food items by small cod, the isopod Saduria entomon is taken by all size classes, and sprat Sprattus sprattus are common prey items for cod larger than 30 cm. Parasitological investigations (microscopic and molecular analyses) of H. sarsi (100 specimens) and S. entomon (40 specimens) did not reveal infection in these invertebrates, but 11.6% of sprat (265 specimens examined) was shown to be infected with 1-8 C. osculatum third stage larvae per fish. Analyses of sprat stomach contents confirmed that copepods and cladocerans are the main food items of sprat. These observations suggest that the C. osculatum life cycle in the Baltic Sea includes grey seals as final hosts, sprat as the first transport host and cod as second transport host. It may be speculated that sprat obtain infection by feeding on copepods and/or cladocerans, which could serve as the first intermediate hosts. One cannot exclude the possibility that the size-dependent C. osculatum infection of cod may contribute (indirectly or directly) to the differential mortality of larger cod (>38 cm) compared to smaller cod (<30 cm) recently recorded in the Baltic cod population.

Whipworms in humans and pigs: origins and demography.

BackgroundTrichuris suis and T. trichiura are two different whipworm species that infect pigs and humans, respectively. T. suis is found in pigs worldwide while T. trichiura is responsible for nearly 460 million infections in people, mainly in areas of poor sanitation in tropical and subtropical areas. The evolutionary relationship and the historical factors responsible for this worldwide distribution are poorly understood. In this study, we aimed to reconstruct the demographic history of Trichuris in humans and pigs, the evolutionary origin of Trichuris in these hosts and factors responsible for parasite dispersal globally.MethodsParts of the mitochondrial nad1 and rrnL genes were sequenced followed by population genetic and phylogenetic analyses. Populations of Trichuris examined were recovered from humans (n = 31), pigs (n = 58) and non-human primates (n = 49) in different countries on different continents, namely Denmark, USA, Uganda, Ecuador, China and St. Kitts (Caribbean). Additional sequences available from GenBank were incorporated into the analyses.ResultsWe found no differentiation between human-derived Trichuris in Uganda and the majority of the Trichuris samples from non-human primates suggesting a common African origin of the parasite, which then was transmitted to Asia and further to South America. On the other hand, there was no differentiation between pig-derived Trichuris from Europe and the New World suggesting dispersal relates to human activities by transporting pigs and their parasites through colonisation and trade. Evidence for recent pig transport from China to Ecuador and from Europe to Uganda was also observed from their parasites. In contrast, there was high genetic differentiation between the pig Trichuris in Denmark and China in concordance with the host genetics.ConclusionsWe found evidence for an African origin of T. trichiura which were then transmitted with human ancestors to Asia and further to South America. A host shift to pigs may have occurred in Asia from where T. suis seems to have been transmitted globally by a combination of natural host dispersal and anthropogenic factors.

Exclusion of IgD‐, IgT‐ and IgM‐positive immune cells in Ichthyophonus‐induced granulomas in rainbow trout Oncorhynchus mykiss (Walbaum)

Ichthyophonus (Plehn & Mulsow) is a protistan fish parasite with a broad host range (Ragan et al. 1996). It infects marine and freshwater fish species worldwide and produces a granulomatous systemic disease in vascularized organs such as heart, liver and kidney (Spanggaard et al. 1994; McVicar 1999). The susceptibility of various fish species is considerably variable. Atlantic herring (Clupea harengus L.) are highly susceptible (Rahimian & Thulin 1996), while rainbow trout Oncorhynchus mykiss (Walbaum) show a medium level of susceptibility and catfish (Ameiurus nebulosus Lesueur) are relatively resistant to this parasite (McVicar 1982, 1999). The main characteristics of the infection are multinucleated spherical parasite cells with a double wall and the tissue around the parasite contains inflammatory cells early in the infection, whereas fibrous tissue dominates late in the infection (McVicar & Maclay 1985; Franco-Sierra & Alvarez-Pellitero 1999; McVicar 1999). Despite the numerous histopathological studies conducted, we have no information about specific lymphocytes involved with Ichthyophonus in rainbow trout. In teleost fish, different B lymphocyte subsets can be found defined by their expression of immunoglobulin types (Igs) present in fish. IgDIgM B cells are present in all teleost species analysed thus far and represent the majority of B lymphocytes in fish. In addition, IgDIgM B cells have been reported in channel catfish Ictalurus punctatus Rafinesque) (Edholm et al. 2010) and in rainbow trout gills (Castro et al. 2014), but their role in immunity has not been yet clarified. Finally, a lineage of B cells uniquely expressing IgT has been reported in some species (Schorpp et al. 2006; Zhang et al. 2010), where they seem particularly important for mucosal responses. In this study, immunohistochemical techniques were applied in order to characterize to what extent B lymphocytes take part in the immune response against Ichthyophonus in naturally infected rainbow trout. For this, cells bearing the different immunoglobulin (Ig) types present in rainbow trout (IgM, IgT and IgD) were recorded in infected fish. Fish and sampling: Samples were collected at a commercial freshwater trout farm located in Idaho, USA, during the monthly health routine monitoring. It was known that the pathogen could occur in the farm but there were no external signs or mortality recorded. From experience, it was known that older fish had a higher probability of infection and three infected rainbow trout (age 500 days old, 7250 degree days, body weight Correspondence K Buchmann, Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 7, DK-1870 Frederiksberg C, Denmark (e-mail: kub@sund.ku.dk)

Experimental anal infection of rainbow trout with Flavobacterium psychrophilum: A novel challenge model

challenge model DTU Orbit (21/09/2018) Experimental anal infection of rainbow trout with Flavobacterium psychrophilum : A novel challenge model Flavobacterium psychrophilum is a Gram‐negative psychrophilic bacterium causing rainbow trout fry syndrome (RTFS) in fry and bacterial coldwater disease (BCWD) in older fish. Both diseases challenge fish welfare and economy in hatcheries and in on‐growing facilities. The bacteria enter hosts through gills, skin, and the gastrointestinal tract, and transfer horizontally in contaminated water and vertically with sexual products of both male and female fish (Madetoja, Dalsgaard, & Wiklund, 2002; Madsen & Dalsgaard, 1999; Nematollahi, Decostere, Pasmans, & Haesebrouck, 2003). Protection afforded by experimental vaccination (injection or immersion) using bacterins (formalin‐killed whole cell) has been described (Hoare, Ngo, Bartie, & Adams, 2017; Madetoja et al., 2006), although no commercial vaccine is presently available for control of RTFS and BCWD. Further research on RTFS/BCWD vaccinology will benefit from an improved challenge method as current methods comprising intraperitoneal (i.p.) injection, bath, and bath exposure after treatment with stressors such as hydrogen peroxide (Henriksen, Kania, Buchmann, & Dalsgaard, 2015; Madsen & Dalsgaard, 1999) remain difficult to reproduce and rely on wounding the structural integrity of mucosal surfaces. The present study compares different infection methods and evaluates systems where the rainbow trout surface (skin, gills, and gut) is kept intact or injured. We compared six different challenge methods comprising anal intubation, i.p. injection, co‐habitation, and bath challenge exposing either nontreated intact fish, fish chemically damaged by exposure to hydrogen peroxide or fish mechanically damaged by needle insertion in the tail‐fin. Disease development was subsequently recorded for 4 weeks.