Standardized white spot syndrome virus (WSSV) inoculation procedures for intramuscular or oral routes

In the past, strategies to control white spot syndrome virus (WSSV) were mostly tested by infectivity trials in vivo using immersion or per os inoculation of undefined WSSV infectious doses, which complicated comparisons between experiments. In this study, the reproducibility of 3 defined doses (10, 30 and 90 shrimp infectious doses 50% endpoint [SID50] of WSSV was determined in 3 experiments using intramuscular (i.m.) or oral inoculation in specific pathogen-free (SPF) Litopenaeus vannamei. Reproducibility was determined by the time of onset of disease, cumulative mortality, and median lethal time (LT50). By i.m. route, the 3 doses induced disease between 24 and 36 h post inoculation (hpi). Cumulative mortality was 100% at 84 hpi with doses of 30 and 90 SID50 and 108 hpi with a dose of 10 SID50. The LT50 of the doses 10, 30 and 90 SID50 were 52, 51 and 49 hpi and were not significantly different (p > 0.05). Shrimp orally inoculated with 10, 30 or 90 SID50 developed disease between 24 and 36 hpi. Cumulative mortality was 100% at 108 hpi with doses of 30 and 90 SID50 and 120 hpi with a dose of 10 SID50. The LT50 of 10, 30 and 90 SID50 were 65, 57 and 50 hpi; these were significantly different from each other (p 50 was selected as the standard for further WSSV challenges by i.m. or oral routes. These standardized inoculation procedures may be applied to other crustacea and WSSV strains in order to achieve comparable results among experiment

The effect of raising water temperature to 33°C in <i>Penaeus vannamei</i> juveniles at different stages of infection with white spot syndrome virus (WSSV)

This study investigated the effect of high water temperature (33°C) at different stages of infection with a highly virulent and low virulent white spot syndrome virus strain (WSSV Thai-1 and WSSV Viet) in Penaeus vannamei juveniles. Shrimp were inoculated intramuscularly with either a high dose (HD) or low dose (LD). Water temperature was kept either at continuously 27°C or switched from 27°C to 33°C at 0, 12 or 24 h post inoculation (hpi) for both strains and in addition at 48 or 96 hpi for WSSV Viet. The increased temperature 33°C was maintained till the end of the experiments (120–144 hpi with WSSV Thai-1 and 240 hpi with WSSV Viet). To determine the infection status at the moment of temperature increase, five shrimp that were kept continuously at 27 °C were euthanized at 0, 12, 24, 48 and 96 hpi with each dose of two strains. WSSV infections (viral antigen VP28) in dead and euthanized shrimp were demonstrated by indirect immunofluorescence.Shrimp inoculated with HD or LD of WSSV Thai-1 and kept continuously at 27°C till euthanasia were 100% viral antigen positive from 12 (HD) or 24 hpi (LD). Shrimp inoculated with WSSV Viet were 100% positive from 24 (HD) and 48 hpi (LD). Shrimp kept at 27°C, showed clinical signs from 24 (HD) or 24–36 hpi (LD) with both strains. Cumulative mortalities reached 100% with WSSV Thai-1 at 60 (HD) or 84–144 hpi (LD) and with WSSV Viet 100% at 216 hpi (HD) or 90% at 240 hpi (LD). Switch of temperature to 33°C from 0, 12 or 24 hpi was effective in reducing mortality of shrimp inoculated with the LD of both strains and with the HD of WSSV Viet. The switch to 33°C from 24 hpi with the Thai strain (HD) and from 48 and 96 hpi with the Viet strain (LD or HD) had no effect or even accelerated the mortality rate (80–100%). All shrimp were viral antigen positive at death and euthanasia (one shrimp LD WSSV Viet) when kept continuously at 27°C. All dead and euthanized shrimp kept at 33°C from 0 or 12 hpi were viral antigen negative. With 33°C from 24, 48 or 96 hpi, all dead shrimp were viral antigen positive and euthanized shrimp were negative.This study showed that 33°C is effective to prevent disease, reduce mortality and block WSSV replication, but only in the early stages of infection

Charting the Host Adaptation of Influenza Viruses

Four influenza pandemics have struck the human population during the last 100 years causing substantial morbidity and mortality. The pandemics were caused by the introduction of a new virus into the human population from an avian or swine host or through the mixing of virus segments from an animal host with a human virus to create a new reassortant subtype virus. Understanding which changes have contributed to the adaptation of the virus to the human host is essential in assessing the pandemic potential of current and future animal viruses. Here, we develop a measure of the level of adaptation of a given virus strain to a particular host. We show that adaptation to the human host has been gradual with a timescale of decades and that none of the virus proteins have yet achieved full adaptation to the selective constraints. When the measure is applied to historical data, our results indicate that the 1918 influenza virus had undergone a period of preadaptation prior to the 1918 pandemic. Yet, ancestral reconstruction of the avian virus that founded the classical swine and 1918 human influenza lineages shows no evidence that this virus was exceptionally preadapted to humans. These results indicate that adaptation to humans occurred following the initial host shift from birds to mammals, including a significant amount prior to 1918. The 2009 pandemic virus seems to have undergone preadaptation to human-like selective constraints during its period of circulation in swine. Ancestral reconstruction along the human virus tree indicates that mutations that have increased the adaptation of the virus have occurred preferentially along the trunk of the tree. The method should be helpful in assessing the potential of current viruses to found future epidemics or pandemics

Vomiting and wasting disease associated with hemagglutinating encephalomyelitis viruses infection in piglets in jilin, china

One coronavirus strain was isolated from brain tissues of ten piglets with evident clinical manifestations of vomiting, diarrhea and dyskinesia in Jilin province in China. Antigenic and genomic characterizations of the virus (isolate PHEV-JLsp09) were based on multiplex PCR and negative staining electron microscopy and sequence analysis of the Hemagglutinin-esterase (HE) gene. These piglets were diagnosed with Porcine hemagglutinating encephalomyelitis virus (PHEV)

Detection of Group 1 Coronaviruses in Bats in North America

Bats of 2 species harbor group 1 coronaviruses

From where did the 2009 'swine-origin' influenza A virus (H1N1) emerge?

The swine-origin influenza A (H1N1) virus that appeared in 2009 and was first found in human beings in Mexico, is a reassortant with at least three parents. Six of the genes are closest in sequence to those of H1N2 'triple-reassortant' influenza viruses isolated from pigs in North America around 1999-2000. Its other two genes are from different Eurasian 'avian-like' viruses of pigs; the NA gene is closest to H1N1 viruses isolated in Europe in 1991-1993, and the MP gene is closest to H3N2 viruses isolated in Asia in 1999-2000. The sequences of these genes do not directly reveal the immediate source of the virus as the closest were from isolates collected more than a decade before the human pandemic started. The three parents of the virus may have been assembled in one place by natural means, such as by migrating birds, however the consistent link with pig viruses suggests that human activity was involved. We discuss a published suggestion that unsampled pig herds, the intercontinental live pig trade, together with porous quarantine barriers, generated the reassortant. We contrast that suggestion with the possibility that laboratory errors involving the sharing of virus isolates and cultured cells, or perhaps vaccine production, may have been involved. Gene sequences from isolates that bridge the time and phylogenetic gap between the new virus and its parents will distinguish between these possibilities, and we suggest where they should be sought. It is important that the source of the new virus be found if we wish to avoid future pandemics rather than just trying to minimize the consequences after they have emerged. Influenza virus is a very significant zoonotic pathogen. Public confidence in influenza research, and the agribusinesses that are based on influenza's many hosts, has been eroded by several recent events involving the virus. Measures that might restore confidence include establishing a unified international administrative framework coordinating surveillance, research and commercial work with this virus, and maintaining a registry of all influenza isolates

Transmission and pathogenicity of novel reassortants derived from Eurasian avian-like and 2009 pandemic H1N1 influenza viruses in mice and guinea pigs

Given the present extensive co-circulation in pigs of Eurasian avian-like (EA) swine H1N1 and 2009 pandemic (pdm/09) H1N1 viruses, reassortment between them is highly plausible but largely uncharacterized. Here, experimentally co-infected pigs with a representative EA virus and a pdm/09 virus yielded 55 novel reassortant viruses that could be categorized into 17 genotypes from Gt1 to Gt17 based on segment segregation. Majority of novel reassortants were isolated from the lower respiratory tract. Most of reassortant viruses were more pathogenic and contagious than the parental EA viruses in mice and guinea pigs. The most transmissible reassortant genotypes demonstrated in guinea pigs (Gt2, Gt3, Gt7, Gt10 and Gt13) were also the most lethal in mice. Notably, nearly all these highly virulent reassortants (all except Gt13) were characterized with possession of EA H1 and full complement of pdm/09 ribonucleoprotein genes. Compositionally, we demonstrated that EA H1-222G contributed to virulence by its ability to bind avian-type sialic acid receptors, and that pdm/09 RNP conferred the most robust polymerase activity to reassortants. The present study revealed high reassortment compatibility between EA and pdm/09 viruses in pigs, which could give rise to progeny reassortant viruses with enhanced virulence and transmissibility in mice and guinea pig models