Very virulent infectious bursal disease virus infection caused changes in cloacal temperature and clinical manifestations in pigeons (Columba livia domestica) and is transmitted to sentinel chickens.

In this study, changes in cloacal temperature and clinical manifestations due to very virulent infectious bursal disease virus (vvIBDV) infection in pigeons (Columba livia domestica) and transmission to chickens were demonstrated. Thirty pigeons (3-6 weeks old) and thirty chickens (3 weeks old) divided into 4 groups (I-IV) were used for this study. Group I comprised of 10 uninoculated pigeons only; II comprised of 10 inoculated pigeons and 10 sentinel chickens; III comprised of 10 sentinel pigeons and 10 inoculated chickens, while IV comprised of 10 uninoculated chickens only. Pigeons in group II and chickens in group III were each inoculated with 0.20 mL (titre of 109.76CID50/mL) of vvIBDV (Nigerian strain). Cloacal temperature was monitored and clinical manifestations scored post-inoculation (pi). Results indicated significant (P < 0.05) pyrexia at 2 days pi (dpi), mild clinical signs and no mortality in inoculated pigeons. Significant (P < 0.05) pyrexia at 2-4 dpi, severe clinical signs and mortality (50%; 60%) were observed in inoculated and sentinel chickens. IBDV antigen and antibody were detected in pigeons and chickens. Pigeons showed response to vvIBDV infection thus suggesting susceptibility of pigeons to IBD. Sentinel chickens presented clinical manifestations of IBD and this suggests transmission from pigeons to chickens. This study therefore documents pyrexia and clinical manifestations due to vvIBDV infection in pigeons and successful transmission of the virus between pigeons and chickens.

Retrospective and prospective studies of transmissible viral proventriculitis in broiler chickens in Brazil.

We investigated the occurrence and pathologic findings of transmissible viral proventriculitis (TVP) associated with the chicken proventricular necrosis virus (CPNV) in commercial broiler chickens in southeastern Brazil. Seventy-three broilers, 25-36 d old, with a history of reduced growth, were referred to our veterinary pathology services from 2013 to 2017. Broilers were clinically examined, weighed, and euthanized for postmortem examination. Broilers of different ages with proventricular histologic lesions were positive for CPNV by RT-PCR; however, the intensity of histologic lesions was higher among 33-d-old animals, and viral RNA detection was more frequent among those that were 28 d old. In the proventriculi of 35 of 73 (48%) broilers, lesions were characterized by glandular epithelial necrosis, lymphoplasmacytic and histiocytic infiltrates, and metaplasia of glandular epithelium to ductal epithelium. In 24 of 73 (36%) broilers with histologic TVP-compatible lesions, CPNV was detected by RT-PCR for the viral protein 1 (VP1) gene. Broilers with histologic lesions were lighter than expected compared to the Cobb 500 standard weight. TVP has not been reported previously in broiler chickens in Brazil, to our knowledge.

Molecular tracing confirms that infection with infectious pancreatic necrosis virus follows the smolt from hatchery to grow-out farm.

Infectious pancreatic necrosis (IPN) is an important restraint to production of salmonids in aquaculture globally. In order to implement efficacious mitigation strategies for control of this disease, it is important to understand infection routes under current production systems. IPN virus has been shown to be transmitted vertically in Rainbow trout, from broodstock to fingerlings in hatcheries, and there is circumstantial evidence suggesting that vertical transmission can also occur in Atlantic salmon, in addition to horizontal transmission between grow-out fish in farms. In this study, we show that the smolt carries infection with IPN from hatchery to the marine farm. We do this by comparing sequences from fish groups taken both in hatcheries and on corresponding marine grow-out farms. We use statistical analysis to prove that sequences obtained from the same fish group in both hatchery and marine farm are more similar than sequences obtained from random fish groups on hatcheries and marine farms.

Inhibition of infectious bursal disease virus transmission using bioceramic derived from chicken feces.

Bioceramic powder (BCX), at pH 13.0, derived from chicken feces, was evaluated for its efficacy to inactivate virus and inhibit virus horizontal transmission by fecal-oral route, using infectious bursal disease virus (IBDV) vaccine strain D78 as a challenge virus. Three 1-week-old SPF chicks were vaccinated per os and used as seeder birds. Six hours later, 3 sentinel 1-week-old SPF chicks were introduced into the same cage. Results revealed that BCX had excellent efficacy to inactivate IBDV within 3 min. Treating IBDV contaminated litter in the cage with BCX could prevent transmission of IBDV to new sensitive chicks completely. Further, transmission of IBDV to the sentinel chicks was significantly inhibited by adding BCX to litter and chicken feed. These data suggest that BCX at pH 13, derived from chicken feces, has excellent efficacy to inactivate IBDV, which can be applied in bedding materials for preventing viral transmission during production round. It is a good material that can effectively be used for enhancing biosecurity system in poultry farms.

Experimental transmission of infectious pancreatic necrosis virus from the blue mussel, Mytilus edulis, to cohabitating Atlantic Salmon (Salmo salar) smolts.

Integrated multitrophic aquaculture (IMTA) reduces the environmental impacts of commercial aquaculture systems by combining the cultivation of fed species with extractive species. Shellfish play a critical role in IMTA systems by filter-feeding particulate-bound organic nutrients. As bioaccumulating organisms, shellfish may also increase disease risk on farms by serving as reservoirs for important finfish pathogens such as infectious pancreatic necrosis virus (IPNV). The ability of the blue mussel (Mytilus edulis) to bioaccumulate and transmit IPNV to naive Atlantic salmon (Salmo salar) smolts was investigated. To determine the ability of mussels to filter and accumulate viable IPNV, mussels were held in water containing log 4.6 50% tissue culture infective dose(s) (TCID50) of the West Buxton strain of IPNV ml(-1). Viable IPNV was detected in the digestive glands (DGs) of IPNV-exposed mussels as early as 2 h postexposure. The viral load in mussel DG tissue significantly increased with time and reached log 5.35 ± 0.25 TCID50 g of DG tissue(-1) after 120 h of exposure. IPNV titers never reached levels that were significantly greater than that in the water. Viable IPNV was detected in mussel feces out to 7 days postdepuration, and the virus persisted in DG tissues for at least 18 days of depuration. To determine whether IPNV can be transmitted from mussels to Atlantic salmon, IPNV-exposed mussels were cohabitated with naive Atlantic salmon smolts. Transmission of IPNV did occur from mussels to smolts at a low frequency. The results demonstrate that a nonenveloped virus, such as IPNV, can accumulate in mussels and be transferred to naive fish.

Viral shedding and emission of airborne infectious bursal disease virus from a broiler room.

1. The significance of airborne transmission in epidemics of infectious diseases in the livestock production industry remains unclear. The study therefore investigated the shedding route (faeces vs. exhaled air) of a vaccine strain of infectious bursal disease virus (IBDV) by broilers and the emission of airborne virus. 2. The experimental room contained 526 broilers which were orally inoculated at the age of 20 d. The airborne virus was sampled by three different bioaerosol samplers: Andersen six-stage impactor, all-glass impinger (AGI-30) and OMNI-3000. 3. Infected broilers started to shed virus in faeces on d 5 post inoculation (PI), and stopped shedding on d 12 PI. The faecal virus remained detectable for at least two d after drying under broiler room conditions. No virus was detected in the air exhaled by broilers. 4. Airborne virus was collected on d 5, 8 and 12 PI at 20 cm above the floor, and on d 8 and 12 PI in exhausted air. The emission rates of IBDV were 4·0 log10 50% tissue culture infectious dose (TCID50)/bird/d on d 8 PI, and 4·5 log10 TCID50/bird/d on d 12 PI. 5. We concluded that broilers shed IBDV mainly through their faeces. The presence of indoor airborne virus is associated with the viral presence in faeces. The successful recovery of airborne virus in exhausted air indicates there is a potential risk of virus spreading to the ambient environment via air.

A comparison of modelling approaches to assess the transmission of pathogens between Scottish fish farms: the role of hydrodynamics and site biomass.

Scotland is the largest Atlantic salmon (Salmo salar) producer in the EU with an output of over 150,000 t, contributing over £500 million annually towards the economy. Production continues to increase, predominantly due to the increase in output per farm and reduction in losses due to infectious diseases. Farms are grouped within disease management areas whose boundaries are defined by where the closest pair of farms is separated by more than twice the tidal excursion distance (TE) Tidal excursion is defined as 7.2 km in mainland Scotland, or 3.6 km in the Shetland Islands). The majority of salmon farms are located within relatively sheltered inshore areas where non-tidal advective current speed is minimal. However there is an aspiration for offshore production where it might be possible to increase stocking levels and where current speeds will be greater so TE models could break down. Separation distances whereby farms would avoid infection risk were obtained using an analytical, discrete-time Susceptible-Exposed-Infectious-Recovered (SEIR) model coupled with a hydrodynamic transport expression representing transmission of pathogenic agents between fish farms. The model incorporated transmission, expression and recovery parameters as well as pathogen shedding and decay. The simplified hydrodynamic model incorporated residual advection, tidal advection and turbulent diffusion elements. The obtained separation distances were compared to a computationally intensive, numerical model and were demonstrated to be comparable, although the analytical model underestimated the variation within the transmission distances. Applying characteristics for a robust pathogen, infectious pancreatic necrosis virus type (IPNV-type), and less robust pathogens such as infectious salmon anaemia virus type (ISAV-type) and Aeromonas salmonicida type (AS-type) pathogens, it was possible to obtain separation distances whereby farms avoided infection. Simulation outputs indicated that separation distances should increase to avoid disease as farm size and current speed increase. The more conserved IPNV-type pathogen required separation distances of hundreds of kilometres, AS-type required tens of kilometres, whilst the distances for ISAV-type were within the scale of the current DMAs, that were developed for ISAV control. However, should production be moved to areas of faster moving currents and increased farm production the current disease management area principles might need readdressing.

The spread of pathogens through trade in poultry meat: overview and recent developments.

Increasing international trade in poultry meat presents an opportunity for the global dissemination of poultry disease. However, it would be very unfortunate if expanding world trade resulted in animal diseases being used as unjustified non-tariff trade barriers. For those avian diseases currently listed by the World Organisation for Animal Health, the current evidence suggests that only highly pathogenic avian influenza, Newcastle disease, and (for chicken meat) infectious bursal disease should be considered likely to be spread though trade in this commodity.

Survey for antibodies to infectious bursal disease virus serotype 2 in wild turkeys and Sandhill Cranes of Florida, USA.

Captive-reared Whooping Cranes (Grus americana) released into Florida for the resident reintroduction project experienced unusually high mortality and morbidity during the 1997-98 and 2001-02 release seasons. Exposure to infectious bursal disease virus (IBDV) serotype 2 as evidenced by seroconversion was suspected to be the factor that precipitated these mortality events. Very little is known about the incidence of IBD in wild bird populations. Before this study, natural exposure had not been documented in wild birds of North America having no contact with captive-reared cranes, and the prevalence and transmission mechanisms of the virus in wild birds were unknown. Sentinel chickens (Gallus gallus) monitored on two Whooping Crane release sites in central Florida, USA, during the 2003-04 and 2004-05 release seasons seroconverted, demonstrating natural exposure to IBDV serotype 2. Blood samples collected from Wild Turkeys (Meleagris gallopavo) and Sandhill Cranes (Grus canadensis) in eight of 21 counties in Florida, USA, and one of two counties in southern Georgia, USA, were antibody-positive for IBDV serotype 2, indicating that exposure from wild birds sharing habitat with Whooping Cranes is possible. The presence of this virus in wild birds in these areas is a concern for the resident flock of Whooping Cranes because they nest and raise their chicks in Florida, USA. However, passively transferred antibodies may protect them at this otherwise vulnerable period in their lives.

Detection and characterization of infectious bursal disease viruses in broilers at processing.

The presence of infectious bursal disease virus (IBDV) in broilers entering processing plants was examined. The dissemination of IBDV and the introduction of non-native strains for example very virulent (vv) IBDV have had a negative economic impact on poultry production in many countries. Restrictions have been placed on the import and export of poultry products by some countries. There is a perceived risk that IBDV can be spread through transportation and contamination of processing equipment, poultry protein products and processing plant personnel. This risk, however, is fundamentally unknown because scientific studies have not been conducted on the presence of IBDV in birds entering processing plants or the variables that may affect this risk during and post-harvest. The goal of this study was to determine if infectious IBDV was present in broilers entering processing plants. A total of 47 pooled bursa samples from 26 processing plants in the Eastern U.S. were examined. Molecular testing indicated that an IBDV specific RT-PCR was positive in 12 (25.5%) of the samples from 11 different processing plants. Nucleotide sequence analysis was conducted on the 12 RT-PCR positive samples and indicated the IBDV was not commercially available attenuated vaccine strains. Most of the sequences were unique and a phylogenic analysis indicated they were most closely related to variant strains of IBDV. Five RT-PCR positive samples were selected at random for testing in specific-pathogen-free chickens. All five samples contained infectious IBDV as evidenced by macroscopic lesions and bursa/body weight ratios that were significantly lower in infected birds than in the non-inoculated controls. The five viruses were re-identified in bursa tissue from chickens in their respective groups at necropsy using RT-PCR and nucleotide sequencing. The results indicate that infectious and pathogenic IBDV are entering processing plants in this geographic region of the U.S. Additional studies are needed on post-harvest variables that could increase or decrease the risk that these viruses are being disseminated during this process.

Viral hemorrhagic septicemia and infectious pancreatic necrosis viruses replicate differently in rainbow trout gonad and induce different chemokine transcription profiles.

Viral hemorrhagic septicemia virus (VHSV) and infectious pancreatic necrosis virus (IPNV) are two rainbow trout (Oncorhynchus mykiss) pathogens. While IPNV is known to be vertically transmitted to the next generation through the oocyte, VHSV is known to replicate in the ovary and be transmitted horizontally through the ovarian fluid. In this work, we wanted to study whether these differences had an effect on the immune response triggered in the ovary, with a focus on the chemokine response. We have studied the kinetics of viral gene expression and the sites of replication, confirming that great differences exist between the replication of the two viruses in the gonad. Next, we studied the levels of expression of several CXC and CC chemokines in the ovary and found that while VHSV strongly triggered chemokine transcription, IPNV had almost no effect. This lack of immune response might be an advantage that permits its vertical transmission.

Mice as potential carriers of infectious bursal disease virus in chickens.

To investigate the role of mice as potential carriers of infectious bursal disease virus (IBDV), three mice were inoculated with a very virulent strain of IBDV and allowed to have contact with three uninoculated mice. Faeces, intestine and pooled liver and spleen collected from inoculated mice 12 and 24 h post-inoculation were positive for IBDV by reverse transcriptase-polymerase chain reaction (PCR)-nested PCR (RT-PCR-nPCR). IBDV was detected by RT-PCR-nPCR in 3/3 samples of intestine and 2/3 samples of pooled liver and spleen from uninoculated in-contact mice at 24 h after exposure. Chickens developed clinical signs of IBD and died when inoculated with faecal extracts prepared from mice 24 h after inoculation with IBDV. Bursae were atrophied and positive for IBDV by RT-PCR-nPCR.

Susceptibility of Atlantic cod Gadus morhua juveniles to different routes of experimental challenge with infectious pancreatic necrosis virus (IPNV).

Atlantic cod Gadus morhua L. juveniles weighing 40 g were challenged with infectious pancreatic necrosis virus (IPNV) by intraperitoneal (i.p.) or intramuscular (i.m.) injection or by bath. The amount of infectious virus was determined over 6 wk in head kidney, heart and pylorus tissues. No mortality or clinical signs were observed in either of the challenged groups. However, 6 wk after challenge virus was still present in the fish, which shows that IPNV can persist asymptomatically in cod. I.p. and i.m. injections were the most efficient routes of challenge giving the highest virus recovery. The prevalence of individuals with a viral titre > or = 500 infectious units g(-1) tissue was lower in the group of fish challenged by bath; thus bath was a less efficient route of challenge than injection. Our data also show that pylorus and head kidney are target organs for IPNV in cod, and levels of virus recovery were not considerably different between these 2 organs. Challenged by injection, the cod heart is also a target organ for IPNV. Compared to head kidney and pylorus, the heart seems to have a minor role in virus multiplication. Virus was also recovered from cohabiting fish, demonstrating that covertly infected cod may represent a reservoir of infectious IPNV for surrounding fish populations. Expression analysis of selected cod immune genes showed that i.p. injection of IPNV induced gene expression of ISG15 and LGP2, markers for the innate antiviral defence, while expression of markers for the inflammatory response (interleukins IL-1 beta, IL-8, IL-10) was not significantly increased.

Experimental study of the susceptibility of Atlantic cod, Gadus morhua (L.), to infection with an IPNV strain pathogenic for Atlantic salmon, Salmo salar L.

Intraperitoneal (IP) injection, cohabitation and immersion routes of infection were used to determine if Atlantic cod, Gadus morhua (L.), of 1 and 3 g are susceptible to infectious pancreatic necrosis (IPN). Mortalities of cod injected IP were significantly higher when challenged with infectious pancreatic necrosis virus (IPNV) than with phosphate buffered saline. This is the first report of Atlantic cod mortalities caused by IPNV. Fish challenged by cohabitation had significantly higher mortalities than the controls, but mortalities of Atlantic cod challenged with IPNV by immersion were not significantly different from controls. Titres of IPNV in the tissues of infected fish were sometimes very high (range 10(2)-10(10) infectious units per gram of tissue) suggesting virus replication and titres of fish that died were generally higher than those of fish which survived. However, the relatively low mortality rates when challenged by cohabitation and immersion (20% and 17%, respectively), compared to the IP injection challenge (100%) suggest that 1 and 3 g cod have low susceptibility to IPN when challenged by more natural routes. These data strongly suggest that the cause of death of experimentally challenged cod was IPNV and further histological evidence for this came from 1 g cod challenged IP with IPNV in which the pancreas showed severe necrosis and heavy immunostaining for IPNV coincidentally with the peak of mortalities.

Estimation of infectious dose and viral shedding rates for infectious pancreatic necrosis virus in Atlantic salmon, Salmo salar L., post-smolts.

Infectious dose and shedding rates are important parameters to estimate in order to understand the transmission of infectious pancreatic necrosis virus (IPNV). Bath challenge of Atlantic salmon post-smolts was selected as the route of experimental infection as this mimics a major natural route of exposure to IPNV infection. Doses ranging from 10(2) to 10(-4) 50% end-point tissue culture infectious dose (TCID(50)) mL(-1) sea water were used to estimate the minimum infectious dose for a Scottish isolate of IPNV. The minimum dose required to induce infection in Atlantic salmon post-smolts was <10(-1) TCID(50) mL(-1) by bath immersion (4 h at 10 degrees C). The peak shedding rate for IPNV following intraperitoneal challenge using post-smolts was estimated to be 6.8 x 10(3) TCID(50) h(-1) kg(-1) and occurred 11 days post-challenge. This information may be incorporated into mathematical models to increase the understanding of the dispersal of IPNV from marine salmon sites.

Distribution of infectious pancreatic necrosis virus (IPNV) in wild marine fish from Scottish waters with respect to clinically infected aquaculture sites producing Atlantic salmon, Salmo salar L.

This study represents the first large-scale investigation of IPNV in Scottish wild marine fish. Kidney samples were taken from 30 627 fish comprising 37 species and 45 isolations were made from nine different species, illustrating these as reservoirs of IPNV in Scottish waters. The estimated prevalence of IPNV in the Scottish marine environment was low at 0.15% (90% confidence intervals, (CI) of 0.11-0.19%). This was significantly greater in fish caught less than 5.0 km from IPN-positive fish farms in Shetland, at 0.58% (90% CI of 0.45-0.77%). This prevalence persisted and did not significantly decrease over the 16-month period of study. The estimated prevalence of IPNV for each positive species was less than 1% with the statistically non-significant exceptions of flounder, Platichthys flesus (L.), at 12.5% (90% CI of 0.64-47.06%) and saithe, Pollachius virens (L.), at 1.11% (90% CI of 0.49-2.19%). The 45 isolates were titrated and all but two were below the detection limit of the test (<55 PFU g(-1)). Titres of 3.8 x 10(2) PFU g(-1) and 2.8 x 10(1) PFU g(-1) were calculated from common dab, Limanda limanda (L.), and saithe, respectively. This study provides evidence that clinical outbreaks of IPN in farmed Atlantic salmon may cause a localized small increase in the prevalence of IPNV in wild marine fish.

Infectious bronchitis virus in the chicken Harderian gland and lachrymal fluid: viral load, infectivity, immune cell responses, and effects of viral immunodeficiency.

We compared detection of infectious bronchitis virus (IBV) by quantitative RT-PCR (qRT-PCR) in tears and trachea of IBV-infected chickens and found that quantitative detection of IBV RNA in tears is more sensitive than in tracheal homogenates. Furthermore, we demonstrated that IBV contained in chicken lachrymal fluid is infectious and that tears of IBV-infected chickens can be used to infect naive chickens. We compared the immune responses to IBV in the Harderian gland and cecal tonsils of immunocompetent chickens and chickens infected with chicken anemia virus (CAV) and/or infectious bursal disease virus (IBDV). Flow cytometry analyses of lymphocytes in Harderian glands and cecal tonsils indicated that the relative abundance of IgM+ B cells in the Harderian glands and cecal tonsils following exposure to IBV in combination with immunosuppressive viruses was reduced compared to chickens infected with IBV alone. CAV, but not IBDV, reduced the CD4+/CD8+ T cell ratios compared to chickens infected with IBV alone. Enzyme-linked immuno-spot forming assays on cells in the Harderian glands and cecal tonsils of IBV-infected chickens indicated that maximum IBV-specific IgA-secreting cell responses were reduced in chickens infected with CAV. IBDV co-infected chickens displayed a delayed IgA response to IBV. Thus immunosuppressive viruses reduced B cells and T helper cells in the Harderian glands and cecal tonsils in response to IBV, and slowed the kinetics and/or reduced the magnitude of the mucosal immune response against IBV. We have shown for the first time that CAV affects pathogen-specific B cell responses in a mucosal effector site.

Modulation of macrophages by infectious bursal disease virus.

Infectious bursal disease is one of the most important naturally occurring viral diseases of chickens worldwide. The causative agent, infectious bursal disease virus (IBDV), belongs to the family Birnaviridae. This virus causes an acute, highly contagious and immunosuppressive disease in chickens. The virus infects and destroys actively dividing IgM-bearing B cells. Although B cells are the principal targets for IBDV, recent data show that the virus also infects macrophages. IBDV-infected macrophages produce various cytokines and chemokines which may play an important role in the protection and/or pathogenesis of IBDV. In this review, the modulatory effects of IBDV on macrophages will be discussed.

Infectious pancreatic necrosis virus establishes an asymptomatic carrier state in kidney leucocytes of juvenile Atlantic cod, Gadus morhua L.

Juvenile Atlantic cod (10 g) were infected with infectious pancreatic necrosis virus (IPNV) by intraperitoneal injection and cohabitation. Fish showed no signs of disease but IPNV could be re-isolated from kidney tissue for up to 12 weeks. On weeks 2, 5, 8, 10, 11 and 12 following infection, kidney leucocytes were fractionated on Percoll gradients, and cells separated into plastic adherent and non-adherent cell populations after overnight incubation. IPNV was detectable in lysates of both cell populations and in supernatants by culture in CHSE-214 cells. Wells containing 10(5)-10(6) macrophages had an IPNV TCID(50) of about 10(3)/well and in serially diluted macrophages the minimum number of cells required to detect virus ranged from 10(1) to 10(4). These data indicate that about one in 10(4) macrophages were infected and the mean number of virus/infected cell was about 10. Replication of IPNV in the macrophages was low as the titre of the virus in macrophage lysates did not increase between days 1 and 3 of culturing the macrophages, but virus was released into the supernatant over this time.