Sawang Kesdangsakonwut

Probable tiger-to-tiger transmission of avian influenza H5N1.

During the second outbreak of avian influenza H5N1 in Thailand, probable horizontal transmission among tigers was demonstrated in the tiger zoo. Sequencing and phylogenetic analysis of those viruses showed no differences from the first isolate obtained in January 2004. This finding has implications for influenza virus epidemiology and pathogenicity in mammals.

Relationships among specific reasons for culling, reproductive data, and gross morphology of the genital tracts in gilts culled due to reproductive failure in Thailand

The present study aims to investigate genital organs of replacement gilts culled due to reproductive failure, and the relationship between gross morphological findings and historical reproductive data. The study was conducted from July 2005 to September 2006 and included a random sample of 200 genital organs from six swine herds in Thailand. Historical data and the reasons for culling were analyzed. Gross morphological examinations focused on the normality and abnormalities of the ovaries, as well as the remainder of the reproductive tract. Descriptive statistics and frequency analysis were conducted for all reproductive parameters. On average, the gilts were culled at 321.2+/-51.1d of age, at a body weight of 145.3+/-24.2kg. Gilts expressed first estrus at 253.2+/-32.7d and were artificially inseminated for the first time at 268.2+/-30.8d of age. The interval from entry to culling averaged 96.9+/-53.7d. Reasons for culling included anestrus (44.0%), vaginal discharge (20.5%), repeat breeding (15.5%), not being pregnant (10.0%), and miscellaneous causes (10.0%). Overall, 50.5% of gilts had normal genital organs, whereas 49.5% had at least one abnormality. Abnormalities of the ovary, oviduct, uterus, cervix and vagina-vestibule were found in 15.5%, 14.0%, 22.0%, 16.2%, and 17.6% of the gilts, respectively. The most common post-mortem abnormalities included endometritis (14.0%), cystic ovaries (10.5%) and congenital abnormalities of the reproductive tract (8.0%). Of the gilts culled due to anestrus, 52.2% were pre-pubertal. Most of the gilts culled due to vaginal discharge or repeat breeding had been cycling (90.2% and 96.8%, respectively).

A novel DNA vaccine for reduction of PRRSV-induced negative immunomodulatory effects: A proof of concept.

BACKGROUND Viral-induced interleukin (IL)-10 and regulatory T lymphocytes (Tregs) are believed to play a major role in shaping the immunological and clinical outcomes following Porcine Reproductive and Respiratory Syndrome virus (PRRSV) infection. Recently, it has been shown that PRRSV nucleocapsid (N) protein can induce IL-10 production which is essential for induction of PRRSV-specific Tregs. We hypothesized that immunity to N protein should reduce PRRSV-induced negative immunomodulatory effects which will be essential for establishing proper anti-PRRSV immunity in infected pigs. OBJECTIVES To investigate the immunomodulatory effects of DNA vaccine encoding a linearized, truncated form of PRRSV-N protein (pORF7t) which was designed to preferentially induce cell-mediated immunity against PRRSV N protein. METHOD Immunomodulatory effects of the novel DNA vaccine were investigated in an experimental vaccinated-challenged model. In addition, long-term immunomodulatory effects of the DNA vaccine were investigated in vaccinated pigs kept at the PRRSV-positive environment until the end of the fattening period. Pigs were vaccinated either prior to or following natural PRRSV infection. RESULT The results indicated that pORF7t could modulate the anti-PRRSV immune responses and promote the control of viral replication in the vaccinated-challenged pigs. Immunized pigs exhibited increased numbers of PRRSV-specific activated CD4(+)CD25(+) lymphocytes, reduced numbers of PRRSV-specific Tregs, and rapid viral clearance following infection. In a long-term study, regardless of the time of vaccination, DNA vaccine could modulate the host immune responses, resulted in enhanced PRRSV-specific IFN-γ producing cells, and reduced numbers of PRRSV-specific Tregs, without evidence of enhanced antibody responses. No vaccine adverse reaction was observed throughout the study. CONCLUSION This study revealed the novel concept that PRRSV-specific immunity can be modulated by induction of cell-mediated immunity against the nucleocapsid protein. This concept could potentially benefit the development of PRRSV management and control strategies.

Porcine circovirus type 3 (PCV3) infection in grower pigs from a Thai farm suffering from porcine respiratory disease complex (PRDC)

Porcine circovirus type 3 (PCV3) is a newly emerging virus with unknown pathogenesis. The major objective of this study was to investigate the presence of PCV3 in pigs from a farm in Thailand suffering from porcine respiratory disease complex (PRDC). Initially, a Thai PCV3 strain (PCV3/Thailand/PB01/17) was identified from a pig originated from a farm with PRDC problem during grower period and whole genome analysis showed that the Thai PCV3 shared highest nucleotide identity of 99.60% with the South Korean strain PCV3/KU-1602. The presence of PCV3 infection in PRDC-affected pigs was then investigated in this farm. Serum samples from clinically healthy pigs and pigs showing PRDC-related clinical signs during 5-18 weeks were used in PCV3 detection by PCR. The results showed that the PRDC-affected pigs exhibited higher prevalence of PCV3 infection and higher PCV3 titers comparing with the clinically healthy pigs. These results confirmed the presence of PCV3 in a Thai farm with PRDC problem. The pathogenesis of PCV3 on PRDC should be clarified in further studies.

Positive immunomodulatory effects of heterologous DNA vaccine- modified live vaccine, prime-boost immunization, against the highly-pathogenic PRRSV infection

Porcine reproductive and respiratory syndrome virus (PRRSV) infection is one of the most important swine pathogens, and causes a major economic impact worldwide. Recently, a new variant type 2 PRRSV, highly pathogenic PRRSV (HP-PRRSV) has emerged and continued to circulate in Southeast Asia region. Currently, commercially available PRRSV vaccines, modified live PRRS vaccines (MLV) are not able to provide complete protection against HP-PRRSV and been reported to induce negative immunomodulatory effects. Interestingly, a novel DNA vaccine was developed and successfully used to improve PRRSV-specific immune responses following MLV vaccination. To investigate the efficacy of a heterologous DNA-MLV prime-boost immunization against the HP-PRRSV infection, an experimental vaccinated-challenged study was conducted. Two-week-old, PRRSV-seronegative, crossbred pigs (5-8 pigs/group) were allocated into 5 groups. At day -14 (D-14), the treatment group (DNA-MLV) was immunized with a DNA vaccine encoding PRRSV-truncated nucleocapsid protein (pORF7t), followed by a commercial modified live type 2 PRRS vaccine (MLV) at D0. The other groups included the group that received PBS at D-14 followed by MLV at D0 (MLV), pORF7t at D-14 (DNA), PBS at D0 (PBS) and the negative control group. At D42, all groups, except the negative control group, were challenged with HP-PRRSV (strain 10PL1). The results demonstrated that pigs that received MLV, regardless of the DNA priming, exhibited less clinical signs and faster viral clearance. Following HP-PRRSV challenge, the DNA-MLV group exhibited improved PRRSV-specific immunity, as observed by increased neutralizing antibody titers and PRRSV-specific IFN-γ production, and reduced IL-10 and PRRSV-specific Treg productions. However, neither the prime-boost immunization nor the MLV was able to induce complete clinical protection against HP-PRRSV infection. In conclusion, improved immunological responses, but not clinical protection, were achieved by DNA-MLV prime-boost immunization. This study highlights the potential use of heterologous prime-boost vaccination regimen, where DNA can be incorporated with other vaccine candidates, for improving anti-PRRSV immunity that may eventually lead induction of complete PRRSV protection.

Protection of human influenza vaccines against a reassortant swine influenza virus of pandemic H1N1 origin using a pig model

Since the pandemic H1N1 emergence in 2009 (pdmH1N1), many reassortant pdmH1N1 viruses emerged and found circulating in the pig population worldwide. Currently, commercial human subunit vaccines are used commonly to prevent the influenza symptom based on the WHO recommendation. In case of current reassortant swine influenza viruses transmitting from pigs to humans, the efficacy of current human influenza vaccines is of interest. In this study, influenza A negative pigs were vaccinated with selected commercial human subunit vaccines and challenged with rH3N2. All sera were tested with both HI and SN assays using four representative viruses from the surveillance data in 2012 (enH1N1, pdmH1N1, rH1N2 and rH3N2). The results showed no significant differences in clinical signs and macroscopic and microscopic findings among groups. However, all pig sera from vaccinated groups had protective HI titers to the enH1N1, pdmH1N1 and rH1N2 at 21DPV onward and had protective SN titers only to pdmH1N1and rH1N2 at 21DPV onward. SN test results appeared more specific than those of HI tests. All tested sera had no cross-reactivity against the rH3N2. Both studied human subunit vaccines failed to protect and to stop viral shedding with no evidence of serological reaction against rH3N2. SIV surveillance is essential for monitoring a novel SIV emergence potentially for zoonosis.

Number of ovulations in culled Landrace × Yorkshire gilts in the tropics associated with age, body weight and growth rate

The objective of the present study was to determine the number of ovulations in culled Landrace × Yorkshire (LY) crossbred gilts in the tropics associated with age, body weight and growth rate. The genital organs from 316 gilts were examined for gross abnormalities, and those with normal cyclic ovaries (n=155, 307 ± 4.1 days of age, 148 ± 1.6 kg body weight) were included in the analyses. Number of ovulations was defined by a count of the corpora lutea (CL) from both ovaries. On average, the number of ovulations in LY gilts was 15.9 ± 0.3 (range 4 to 27). The number of ovulations correlated with the body weight (r=0.31, P<0.001) and growth rate (r=0.20, P=0.015) of the gilts, but not with their age (P>0.05). Gilts with a body weight of 141 to 150 kg (17.0 CL, n=31) ovulated more than those with a body weight ≤130 kg (14.1 CL, P=0.014, n=23). In conclusion, both the body weight and growth rate of the gilts were significantly correlated with the number of ovulations. The maximum number of ovulations was found in gilts at a body weight of above 141 kg.

Novel canine circovirus strains from Thailand: Evidence for genetic recombination

Canine circoviruses (CanineCV’s), belonging to the genus Circovirus of the Circoviridae family, were detected by next generation sequencing in samples from Thai dogs with respiratory symptoms. Genetic characterization and phylogenetic analysis of nearly complete CanineCV genomes suggested that natural recombination had occurred among different lineages of CanineCV’s. Similarity plot and bootscaning analyses indicated that American and Chinese viruses had served as major and minor parental viruses, respectively. Positions of recombination breakpoints were estimated using maximum-likelihood frameworks with statistical significant testing. The putative recombination event was located in the Replicase gene, intersecting with open reading frame-3. Analysis of nucleotide changes confirmed the origin of the recombination event. This is the first description of naturally occurring recombinant CanineCV’s that have resulted in the circulation of newly emerging CanineCV lineages.