Vol. 18 No. 7 (2020)

Since the first detection in 2009, PEDV has been circulating in the North, Centre and the South of Vietnam. The disease has caused significant damages to the pig production sector. In order to mitigate the economic damage caused by diseases, the manufacture and use of field- matching vaccines are necessary. Aimed at providing more information on the biology of pathogenic PEDV strains in Vietnam, this study analyzed the molecular biology of the gene encoding S1 domain of one PEDV isolate detected in Hung Yen in 2017. The results showed that the field isolate, PEDV_HY2017, is genogroup G2 PEDV. The virus shared nucleotide similarity with PEDV strains of Vietnam in the ranges of 90-91% and 95.7-98.2% in compared to genogroup G1 and genogroup G2, respectively. The PEDV_HY2017 strain carries two regions of insertion-deletion mutations in the gene segment encoding the S1 domain of the Spike protein. This characteristic was similar to the other Vietnamese PEDV genogroup G2 viruses.

The study aimed to establish a virus neutralization test for field isolated virus, create a tool for assessing the protection of vaccines against pathogenic porcine epidemic diarrhea virus (PEDV) strains in Vietnam. By using DMEM medium free calf fetal serum (FBS) and without trypsin for dilution sample preparation/viral suspensions, and the maintenance medium containing 8 µg of trypsin/ml, the virus neutralization test and evaluation of neutralizing antibodies by immunochemical staining on monolayer cells were optimized. The results showed that the virus neutralization test for field isolated virus with the sensitivity of 87.46% and specificity 98.18% with compared to ELISA kit. It also pointed out that the virus neutralization test could be applicated to detect fluctuation of PEDV neutralization antibody in colostrum and serum of mother and piglets.

This study was conducted on African Swine Fever (ASF) infected pigs from outbreaks in Hung Yen and Thai Binh provinces in February 2019. All pigs were tested positive for ASF virus by PCR method. The methods of investigation, autopsy and microscopic specimens were used to identify the clinical symptoms, gross and microscopic lesions of infected pigs. The results showed clinical symptoms of ASF pigs included high fever, loss of appetite, vomiting, skin hemorrhage, blood clotting abnormality, epistaxis and diarrhea. Severe hemorrhage was a gross lesion observed in different organs (lymph nodes, heart, kidney, stomach, intestines, gallbladder, bladder...). Hypertrophic spleen, black and purple hemorrhagic gastrointestinal lymph nodes and kidney lymph nodbaes were found in most cases. Microscopic lesions were marked lymphoid depletion in the spleen, lympho nodes and tosil, multi organic severe congestion and haemorrhages. It can be said that the first outbreaks of ASF in the North of Vietnam were produced by highly virulent strain and induced disease onset with peracute to acute disease course.

Porcine Parvovirus (PPV1) is one of the main pathogens inducing reproductive failure in sows. PPV1 is also known as a triggering factor of porcine circovirus type 2. In Vietnam, the presence of PPV1 and its association with reproductive disorders of sows had been confirmed. However, few publications are available on this topic. This study investigated the occurrence of PPV1 in growing pigs risen in Hanoi and neighboring provinces by serology test, PCR and genetic analysis. It was revealed that 88.2% (60/68) sera contained detectable antibodies against PPV1. Of these, 18/60 sera had high antibody titres (HI >1/512). The viremia was detected at a high frequency (10 out of 18 tested sera) and was uncorrelated with the level of antibody titers against PPV1. The genetic analysis based on the partial NS1- protein-coding gene showed that 10 PPV1 field strains were within genogroup 1. In combination with the other studies, the current result supported that PPV1 is circulating in pigs in Vietnam.

The present study was conducted to evaluate the maturation rate of porcine oocytes matured in POM or TCM199 medium; in maturation, medium made from Sigma pure water or MQW and effects of hormone supplementation in the first 22 hours or during IVM. Maturation rate of porcine oocyte matured in POM (73.45 ± 2.61%) medium was significantly higher than that of TCM199 medium (58.84 ± 2.49). There was no significant difference in the maturation rate of porcin oocyte matured in POM medium made from Sigma pure water (87.16 ± 4.74%) or MQW (83.20 ± 6.93%). The supplementation of hormone in 22 hours could help to improve the maturation rate (90.88 ± 2.33%) compared to that of 46 hours (84.93 ± 2.78%). MQW can be used to prepared porcine oocyte matured medium. Supplementation of hormones during IVM1 has potential to improve the maturation rate of porcine oocytes.

This study aimedto assess the virulence in experimental pigs of field African swine fever virus strain (VNUA - ASFV -L01) belonged to genotype 2 which isolated from the infected pig duringan outbreakoccurredin Ha Nam province of Vietnam, 2019. The experimental pigs were intramuscularly inoculated with the virus at a dose of 104 HAD50. All inoculated pigs showed acute disease manifestations and died between 7and 9 days post-infection (dpi) with clinical features of ASF including high fever (41-42°C), diarrhea, vomiting, loss of appetite and reflexes, depression, respiratory distress, haemorrhages in the skin, neurological signs, coma and death. Haemorrhagic lesions were typically observed in multiple tissue organ in ASFV infected pigs with remarkable signs of diffuse hemorrhages in lymph nodes, renal cortex, haemorrhagic spleen, swollen liver, edema of the gallbladder, and hemorrhagic meninges... Analysis of viremia inthe blood of pigs by real-time PCR showedthat ASFV viremia was detected in the blood of pigs at 2 days post-inoculation, thereafter rapidly replication of field virus strain was observed in the blood of infected pigs at a later time point post-infection (days 3 to 6). These initial results indicate that VNUA - ASFV -L01 strain is highly virulent in pigs.

Avian metapneumovirus (aMPV) is one of the etiological agents of the swollen head syndrome (SHS) in chickens. The aim of this study was to confirm the presence of aMPV in some northern provinces of Vietnam.By using ELISA and RT-PCR techniques, the study detected molecular and serology of aMPV in chickens. A result of testing 85 chickens aged from 5 to 12 weeks without aMPV vaccination showed that 22 chickens (25.88%) had aMPV antibody. In contrast, out of 85 swab samples tested only 3 (3.53%) were positive to aMPV by RT-PCR. Clinical signs and gross pathology indicate that chickens suspected to be infected with aMPV are concentrated in the upper respiratory tract. Swelling of the periorbital and infraorbital is the most common. The research result is providinga scientific basis for diagnosing and recommending to use proper vaccines to reduce the economic losses due to aMPV.

This study was conducted in order to providefurtherinformation on clinical signs as well as macroscopic and microscopic lesions in the uterus of the 6 rabbits in Hanoi. In the present study, pet rabbits were determined the clinical symptoms, gross features, and microscopic lesions using through clinical observation and histopathological methods. Clinical symptoms were often non-specific, mainly in the genital-urinary tract, such as vaginal discharge/bleeding, abnormal swelling. The condition was discovered as an incidental finding during neutering (in 4 rabbits) and abdominal palpation (in 2 rabbits). The histopathological examination revealed that uterine adenocarcinoma in 3 rabbits, endometrial hyperplasia in 2 rabbits, and uterine leiomyoma with endometrial hyperplasia in a rabbit. Therefore, female rabbits as pets should be routine check-ups. Additionally, ovariohysterectomy should be performed early if the rabbit is not intended to be bred for reducing the risk of uterine problems.

The study was designed to determine the effects of estrus induction method combined fixed-time artificial insemination (FTAI) in dairy cows. This study was conducted on 17 sixteen-month-old prepubertal heifers and 34 repeat breeder cows in Vinh Phuc province between July and November 2019. Hormones therapy and progesterone device were used to induce estrus and performed artificial insemination during 14-18 hours after finish the treatment. Pregnancy diagnosis was performed from 60 days after FTAI date. The results have indicated that the insemination rate and the conception rate were 100% (51/51 cows) and 37.25% (19/51 cows), respectively. Regarding the non-pregnant group, the estrus resumption proportion was 96.87% (31/32 cows). In conclusion, the significant effects of estrus synchronization and fixed-time artificial insemination (FTAI) were proved to increase the insemination rate and to promote cow to return to the normal physiological estrus cycle, although the first service conception rate was not high after treatment.