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Exploring Prevalenceof Mycoplasma hyorhinisInfection by PCR Method in Pigs Raised in Hung Yen Province

Truong Quang Lam, Nguyen Thi Thu Huong, Nguyen Thi Lan, Dao Le Anh, Le Thi Trang, Vu Thi Anh

Received: 12-10-2021 / Accepted: 05-07-2022
The aim of this study was to determine the infection rate of Mycoplasma hyorhinisfrom suspected pigs in Khoai Chau, Van Giang, and Yen My districts of Hung Yen province.A total of 52 clinical samples of suspected pigs were used to determine the infection rate of M. hyorhinisby using the PCR method. The results showed that the infection rate of M. hyorhinisin 3 districts in Hung Yen province was relatively high at 26.92%, in which infection rate was recorded in Khoai Chau with 31.82%, Van Giang 25.00% and Yen My 21.43%. The rate of infection with M. hyorhinisin pigs at 5-10 weeks of age was the highest at 29.41% and was similar to pigs >10 weeks old 28.57%,while pigs <5 weeks oldshowed lowest infection rate 21.43%. Research also determined that the rate of co-infection of M. hyorhiniswith M. hyopneumoniaeaccounted for 28.57%, H. parasuis35.71% and S. suis21.43%. Comparison of macroscopic findings and PCR results showed that pigs infected with M. hyorhinisexhibited the main pathological feature with a severe fibrinous pericarditis.
Several Epidemiological and Clinical Characteristics of Strongyloidosisin Dairy Cowsat theFarmof Mocchau Dairy Cow Breeding Joint Stock Company

Tran Duc Hoan, Nguyen Thi Huong Giang

Received: 10-02-2020 / Accepted: 24-02-2020
The study aimed to identify some epidemiological and clinical characteristics of Strongyloidosison dairy cow. By using theepidemiological methods, 809 fecal samples were collected for examinationby floatation method. The results indicated that the infection rate of Strongyloidesspp. at 5 farms in Mocchau dairy cow breeding joint stock company was 26.58%. Dairy cow infected Strongyloidesspp. with all ages, the infection rate of Strongyloidesspp. reduced according to the age (60.48% in dairy cow under 6 months old and decreased by 7.78% in dairy cow over 2 years old. Strongyloidosiscould occur in all year round, although the infection rate of Strongyloidesspp. in February and March were higher than December and January, respectively. The infection rate of Strongyloidesspp. at households (35.48%) were higher as compared with industrial farms (23.56%). The infection rate of Strongyloidesspp. in dairy cows with diarhhea (58.29%) was higher than dairy cow with normal feces (17.04%). The infection rate of Strongyloidesspp. showed clinical sign 17.67% with the main symptoms as scraggy, ruffled, sticky feces in the anus, loss of appetite, non-appetite, loose stools.
Comparison and Evaluation of Cross-infection Possibility of Edwardsiella ictaluri Isolatedfrom Tilapia and Channel Catfish under the Experimental Conditions

Doan Thi Nhinh, Dang Thi Hoa, Tran Thi Trinh, Le Viet Dung, Nguyen Thi Huong Giang, Kim Van Van, Dang Thi Lua, Truong Dinh Hoai

Received: 05-01-2021 / Accepted: 23-04-2021
The study was conducted to compare and evaluate the cross-infection possibility of Edwardsiella ictaluricausing diseases in tilapia and Channel catfish. The strains ofE. ictaluriisolated from tilapia and Channel catfish were compared based on the biochemical characteristics, PCR confirmation, lethal doses and the possibility of cross-infection among other fish species. The results revealed that E. ictaluriisolated from tilapia and Channel catfish differed in 2/22 biochemical reactions (citrate utilization, Voges-proskauer) but they were identical in PCR assay. The virulence of E. ictaluristrains from tilapia was high when they were challenged to tilapia (LD50= 2.5 101CFU/fish) but remarkably decreased to Channel catfish (LD50= 2.0 106CFU/fish). Similarly, the isolates from Channel catfish exhibited a high virulence in this fish (LD50= 4.7 103CFU/fish) but reduced their pathogenicity to tilapia (LD50= 2.5 106CFU/fish). The primary result demonstrates that E. ictaluricausing diseases in Channel catfish and tilapia differed in several characteristics. However, they cause relatively high mortality of fish when cross-infection among fish species at high bacterial densities. Thus, biosafety is required to avoid the spreading of pathogens in the culture systems.
Pathogenesis of Hp-Prrsv in Crossbred Wild Pigs through Experimental Innoculation

Do Tien Duy, Nguyen Pham Huynh

Received: 23-11-2018 / Accepted: 05-03-2019
The objective of this study was to examine the pathogenesis of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) in crossbred-wild pigs through experimentally infected model. Twenty eight healthy crossbred-wild pigs, 42-49 day-old, originated from CSFV-PRRSV-negative farms were allocated in two experimental groups.The findings in clinical signs and pathology showed that the acute phase of infection took place from 5 to 14 days post infection. The major manifestations were fever, anorexia, respiratory failure, eye discharge and swelling, shivering and death. Severe interstitial pneumonia happened in all infected animals and interstitial pneumonia accompanied with hemorrhage recorded in died pigs. The laboratory indicators (viremia in the blood/tissues, IHC score, IgG antibodies, IL-1) were in homology with clinical pathology in acute phase of the disease. There were variations ofthe antigen distribution in various tissues over time-points post infection. This virus was first detected intheepithelial cells of bronchioles, stomach, kidney, bile duct and hepatic cells. The study results demonstrated that HP-PRRSV might cause severe pathology, wide antigenic distribution in visceral organs and could be fatal in crossbred-wild pigs through experimental infection.
The Effects of a Protein Rích Diet on Pathogenicity of Three Weak β-haemolyticBrachyspira Species in Fattening Pigs

Nguyen Thi Tuyet Le, Anja Rothkamp, Frank Seeliger, Michael Wendt

Received: 18-08-2020 / Accepted: 14-09-2020
This study was performed to evaluate the influence of a protein rich diet as a provocative factor on producing the clinical disease after infection with three weak β-haemolytic Brachyspira species (B. innocens, B. murdochii and B. intermedia) in fattening pigs.A total of 67 pigs with an average body weight of 15.6 ± 3.1kg were fed a diet containing 50% extracted soybean meal for seven days. The results of the experimental groups (infection with weakly haemolytic Brachyspira species B. innocens, n = 15, B. murdochii, n = 24 and B. intermedia, n = 10) were compared with those of the positive control group (infection with B. hyodysenteriae, n = 15) and the negative control group (n = 3; no inoculation). The results showed that all 15 pigs inoculated with B. hyodysenteriae developed mucohaemorrhagic diarrhea after an incubation period of one to 13 days. In contrast, diarrhea could not be detected in the three groups inoculated with weakly haemolytic Brachyspira species. These groups also showed no significant difference in the average weight gain and feed conversion ratio with no pathological findings typical for dysentery among themselves. It can be therefore concluded that the examined strains of weakly haemolytic Brachyspira species could colonize and proliferate in the mucosa of the large intestine after the experimental infection. Faecal shedding occurred regularly, but no clinical symptoms of swine dysentery could be produced in the experimental pigs.
Evaluation of Agro-Biological Characteristics of some Cassava (Manihot EsculentaCrantz) Materials in Field Conditions and Screening of the Resistance to CMV in Artificial Infection

Hoang Thi Thuy, Tran Thi Thanh Ha, Vu Thi Bich Hanh, Nguyen Van Ha, Duong Thi Loan, Vu Van Liet

Received: 11-02-2020 / Accepted: 11-08-2020
This study was conducted to evaluate some agro-biological characteristics of 14 domestic and exotic cassava materials in Gia Lam, Hanoi condition, and to evaluate the resistance of the materials through artificial infection experiments by the transplanting method. The material was grown in the field in a sequential experiment without repeating, tracking some agro-biological characteristics. The materials were havested after 8-11 months. The plant height of the materials ranged from 165.2-183.2cm, there are 8 materials with branching height. Most materials have only 1 stem/cluster, CM15, CM21 had 2 stems/cluster and CM60 had 3 stems/cluster. The number of tubers/tree varies from 4.3-15.8 tubers/tree. The highest weight of fresh tubers was obtained CM15 (5.0 kg/tree) and 2 control varieties (5.26-5.82 kg/tree). Using the tranplanting method, evaluated after 2 weeks, 40 successful transplanted trees of 13 materials were evaluated. Genotyping of these transplanted trees was checked by JSP1/JSP2 and JSP1/JSP3 primers detected the presence of ACMV in plants of 8 materials (CM2, CM3, CM8, CM15, CM20, CM60, KM140 and KM94). Assessing the level of infection after 3 months of transplantation, the group of resistant and highly resistant varieties were identified including CM15, CM16, CM21, CM60, CM88, CM50, CM61 and KM94.
Gene Expresssion of Cytokine and Toll-like Receptor Signaling molecule mRNA in Peripheral Blood Mononuclear Cells (PBMCs) from Pigs Co-infected with Porcine Reproductive and Respiratory Syndrome Virus and Porcine Circovirus

Dong Van Hieu, Phan Hong Dien, Tran Thi Huong Giang, Wen Bin Chung

Received: 18-03-2015 / Accepted: 18-05-2015
Field and experimental studies have shown that co-infection of PRRSV and PCV2 in pigs were quite common and thus the interactions between both viruses in the host might be critical to the pathogenesis of the disease. The exact interaction mechanisms are unknown and remained to be elucidated. In this study, the expression of cytokine mRNA as well as Toll like receptor signaling molecules associated with innate immunity in peripheral blood mononuclear cells (PBMCs) from pigs infected with PRRSV and/or PCV2 were investigated. Cytokine mRNA and TLR signaling molecule expression were determined by quantitative real-time polymerase chain reaction. Co-infection of pigs with PRRSV and PCV2 led to up-regulated expression of IL-1β and IL-10 mRNA and down-regulated expression of TNF-α and IL-6, IFN-α and IFN-β in PBMCs of pigs co-infected with PRRSV and PCV2. An increased expression of CD14 mRNA was noticed in pigs co-infected with PRRSV and PCV2. A down-regulated expression of IRF-1 and IRF-3 mRNA might also suppress the expression of IFNs that leads to the enhanced replication of PCV2 in pigs co-infected with PRRSV and PCV2.
ẢnhhưởngcủatếbàohìnhchéntrongviệcthảitrừgiunNippostrongylusbrasiliensisở vậtchủđồngnhiễmvớiEimeriavermiformis

Bui Khanh Linh, Hayashi T

Received: 20-06-2014 / Accepted: 02-03-2015
Tế bào hình chén đóng vai trò quan trọng trong việc thải trừ giun Nippostrongylus brasiliensis (N. brasiliensis) thông qua việc tăng số lượng tế bào và tăng tiết chất nhầy ở ruột. Trong khi đó, cầu trùng Eimeria vermiformis lại làm giảm số lượng tế bào hình chén ở ruột và hình thành miễn dịch tế bào Th1 ở ruột thì N. brasiliensis lại sản sinh đáp ứng miễn dịch Th2. Bài báo này sẽ thảo luận những ảnh hưởng gây ra do tế bào hình chén ở chuột đồng nhiễm trong việc thải trừ N. brasiliensis. Nippostrongylus brasiliensis và Eimeria vermiformis được gây nhiễm cho chuột ICR. Kết quả cho thấy, việc thải trừ giun bị giảm ở chuột đồng nhiễm so với chuột đơn nhiễm và có liên quan đến số lượng của tế bào hình chén. Kết quả này cho thấy, Eimeria vermiformis có ảnh hưởng đến việc thải trừ Nippostrongylus brasiliensis và có thể thông qua hệ đáp ứng miễn dịch ở chuột đồng nhiễm.
Study on Some Biological and Molecular Biological Characteristicsof the KTY-PRRS-01 Virus Strain Isolated in Vietnam

Pham Van Son, Nguyen Thi Lan, Nguyen Van Cam, Nguyen Ba Hien

Received: 27-02-2017 / Accepted: 25-04-2017
The study was carried out on the KTY-PRRS-01 virus strain isolated in Vietnam. The PRRSV strains were cultured for 5thconsecutive generations on the Marc145 cell and in each passage the virus was tested for biology and molecular biology characteristics. The results of the study showed that through 5th passages, the ability to multiply and destroy the cells of the original virus over time had no significant difference in the generations. The virus began to multiply and had cytopathogenic effect after 48 hours post - infection, cytopathogenic effect reached 80% at 72 hours post - infection, and the cells were completely destroyed after 84 hours post - infection. TCID50 of virus was stable through 5th passages with a titre from 3,03x106/ml to 7,12x106/ml. The ORF5 and ORF7 gene sequences of the virus strain through 5th passages were sequenced. Sequences of these genes showed no difference in nucleotide sequences as well as amino acids through 5th passages. Thus the KTY-PRRS-01 virus strain is stable in biological and molecular biology characteristics over 5th passages.
Detection of anti-Toxocara spp. and Ascaris suum Antibodies in Naturally Infected Free-range Chickens

Nguyen Thi Hoang Yen, Nguyen Thi Hop, Do Trung Dung, Pham Thi Toi, Dong The Anh, Nguyen Van Phuong, Nguyen Thi Hong Chien

Received: 26-08-2020 / Accepted: 18-01-2020
The purpose of this study was to detect anti-Toxocara spp. and Ascaris suum antibodies in freely raised chickens. Two hundred and fifty-one serum samples were collected at the fresh market (Trau Quy, Gia Lam, Ha Noi) and some small-scale free-range chicken farms (Bac Giang Province). Indirect ELISA was applied using As-SWAP crude antigen to screen and choose serum samples which showed positive reactions with anti-ascarid antibodies and using Tci-ES and Asm-ES antigens to discriminate infecting species. Next, Toxocara Western Blotting Kit was applied to confirm Toxocara infection, and pre-adsorbed ELISA was conducted to confirm A. suum infection. The results showed that: 38.65% of serum samples contained anti-ascarid antibodies. Additionally, the result of discrimination of infecting species assumed that 11.55% and 2.79% samples containing anti-Toxcocara spp. and anti-A. suum antibodies, respectively. This is the first study to detect Toxocara spp. and A. suum in naturally infected free-range chickens. The attained results of this study provides important information for chicken farmers in protecting themselves in order to avoid exposure to ascarid egg-contaminated soil. Besides, it gives evidence of the risk of getting A. suum infection in humans in Vietnam.
Alternaria Leaf Spot Diseaseon Cabbage (Brassica oleraceaL. var. capitata) in Nghe An Province

Nguyen Xuan Canh, Nguyen Xuan Truong, Nguyen Thi Thu, Vo Thi Bich Thuy, Dang Thi Thanh Tam, Nong Thi Hue, Pham Hong Hien

Received: 30-08-2023 / Accepted: 05-01-2024
The study was conducted to isolate and identify the causal agent of leaf spot disease on cabbage (Brassica oleracea L. var. capitata) in Hung Tien, Nam Dan, Nghe An province. Ten symptomatic cabbage leaves were collected from three diseased fields. Morphological examination revealed that only one type of fungus (designated as BC01) was isolated from the cut surface of the diseased leaf pieces. The isolate BC01 had dark olive colonies, white margin, cottony mycelium, branched conidial chains, brown oval or ellipse conidia shape with a short cone-shaped beak at the head, 0-3 longitudinal septa and 1-5 transverse septa. The conidial size ranged from 10.17 to 40.06 × 4.16 to 13.09µm. Based on the ITS gene sequence analysis and morphological characteristics, the isolate BC01 was identified as Alternaria alternata. After 7 days of re-infection, the symptoms on the re-infection leaves were similar to those on the isolated leaves. At the site of infection, the fungal mycelium grew densely and invaded deep into the leaf tissue, while the control leaves showed no symptoms.
Biological Characterization of Canine Parvovirus Type 2 IsolatesCausing Canine Parvovirus Enteritis in North Viet Nam

Truong Quang Lam, Nguyen Thi Lan, Nguyen Anh Tuan, Nguyen Thi Yen, Nguyen Thi Hoa, Le Thi Luyen

Received: 10-03-2021 / Accepted: 21-01-2022
Canine parvovirus (CPV) is a highly contagious viral disease that commonly causes acute gastrointestinal illness in dog breeds in Vietnam. We isolated and determined genotype and biological characteristics of CPV in the CRFK cell line. Three strains of CPV, VNUA.CPV.HN01, VNUA.CPV.HN04 and VNUA.CPV.HY05 in the CRFK cell line were isolated from 30 clinicalsamples. The phylogenetic analysis revealed that all CPVisolates belonged to the genotype CPV2c. CPV did not cause disease in the first passage but caused cytopathogenic effect in the CRFK cells after 2 to 4 blind passages. Cytopathic effect (CPE) occurred within 24 hours post-infection and the cells were completely destroyed after 60 to 72 hours of infection. CPE viral titer was high, at 107,47TCID50/ml. The growth curve reached the peak at 60 to 72 hours after infection and then decreased gradually.
Biological Characterization of Canine Parvovirus Type 2 IsolatesCausing Canine Parvovirus Enteritis in North Viet Nam

Truong Quang Lam, Nguyen Thi Lan, Nguyen Anh Tuan, Nguyen Thi Yen, Nguyen Thi Hoa, Le Thi Luyen

Received: 10-03-2021 / Accepted: 21-01-2022
Canine parvovirus (CPV) is a highly contagious viral disease that commonly causes acute gastrointestinal illness in dog breeds in Vietnam. We isolated and determined genotype and biological characteristics of CPV in the CRFK cell line. Three strains of CPV, VNUA.CPV.HN01, VNUA.CPV.HN04 and VNUA.CPV.HY05 in the CRFK cell line were isolated from 30 clinicalsamples. The phylogenetic analysis revealed that all CPVisolates belonged to the genotype CPV2c. CPV did not cause disease in the first passage but caused cytopathogenic effect in the CRFK cells after 2 to 4 blind passages. Cytopathic effect (CPE) occurred within 24 hours post-infection and the cells were completely destroyed after 60 to 72 hours of infection. CPE viral titer was high, at 107,47TCID50/ml. The growth curve reached the peak at 60 to 72 hours after infection and then decreased gradually.
The Prevalence of Porcine Epidemic Diarrhea (PED) and Detection of Antibody against PED Virus in Pigs Infected by “Gut Feedback” Method in Thanh Hoa Province

Hoang Van Son, Pham Ngoc Thach, Nguyen Thi Lan

Received: 10-01-2020 / Accepted: 10-07-2020
A survey on the prevalence of PED and detection of antibody against PED virus in pigs infected by “gut feedback” method was conducted in Thanh Hoa province. A total of16.443 pigs raised in six districts of Thanh Hoa province was daily observed, the pigs with symptoms of PED were confirmed by PED Ag Test kits and RT-PCR technique.A total of sixty gestation sows (at 13th weeks of pregnancy) was used in an experiment to detect antibodies against PED virus by protein-based enzyme-linked immunosorbent assay (ELISA) testing method. The results showed that the prevalence of PED in pigs in Thanh Hoa province was 14.56% with the case fatality rate (CFR)was 53.38%. Of all districts, the prevalence was the highest in Tinh Gia district (16.12%), while it was the lowest in Yen Dinh district (12.08%). The prevalence and CFR of PED were the highest in suckling pigs (22.01% and 72.63%, respectively) but they were lowest in boars (5.81% and 0%, respectively). In this study, the prevalence of PED was higher in the winter than in the summer (33% and 18%, respectively). The size of farms has also affected the results, in which the large farm showed the highest prevalence (15.79%) but the lowest CFR (50.75%). The results indicated that after infected with PED by “gut feedback” method, all of the serum samples from experimental pigs presented antibodies against PED virus. At 14 days and 21 days after infection, the percentages of pigs showed positive results to antibodies against PED virus were 78.33% and80.00%, respectively.
The Reproductive Biology ofDactylogyrus sp. (Monogenea: Dactylogyridae) Infecting Grasscarp

Truong Dinh Hoai, Nguyen Thi Hau, Kim Van Van

Received: 24-09-2013 / Accepted: 12-11-2013
Dactylogyrus sp., a common external parasite frequently occurs with high percentage and intensity of infection in fresh water fish. The infection of this prasite causes great influence on the growth and production of many freshwater fish, especially grasscarp (Ctenopharyngodon idella) at fry and fingerling stage. The study was carried out on 180 fry grasscarp, 363 mature Dactylogyrus sp. and 1813 eggs of Monogenea to investigate major features of the reproductive biology of this parasite. The results showed that the maturation time of the eggs from being laid to hatching to oncommiracidia was 4.65 ±0.27days. This parasite reaches sexual maturity and completes their life cycle in 11.4 ± 0.24 days. Egg production increased gradually over time, rising from 2.75 ± 0.17 to 8.08± 0.53 eggs/h from day 1 to day 5.. At night time, the rate of laying and egg production was 1.7 to 2 and 1.6 to 2.1 times, respectively, higher than those at day time. This study is the first instance that the reproductive biology of Dactylogyrus sp. infecting grasscarp was examined in Vietnam.
ClinicalandNon-Clinical Characteristics and Gross Lesions of Chickens Infectedby Chicken Infectious Anemia Virus (CIAV) under ExperimentalCondition

Dao Doan Trang, Nguyen Van Giap, Le Thi Trinh, Truong Ha Thai, Lai Thi Lan Huong, Cao Thi Bich Phuong, Huynh Thi My Le

Received: 31-07-2019 / Accepted: 20-09-2019
This study was conducted to reveal the clinical and non-clinical characteristics as well as gross lesions of chickens infected by chicken infectiousaAnemia virus (CIAV) under an experimental condition. Via intra-abdominal inoculation of the virus at a dose of 104TCID50/mL, one-week oldchickens were sucessfully infected by the field strain of CIAV with the viremia appeared at 3 weeks postinfection (20.0%) and reached 100% at the sixth week postinfection. Under the current condition, viremic CIAV chickens exhibited minimum clinical signs. From the fifth week after infection, CIAV infected group exhibited a reduction inthe growth rate and had significantly lower body weight than that of the control group. Additionally, at eighth week postinfection, the packed cell volume of CIAV positive group was less than 27% and was significantly lower than the control group. The chickens of the experimental group had compatible gross lesions of anemia, such as pale of bone marrow (77.8%) and atrophy of primary lymphoid organs (bursa of Fabricius and thymus, 33.3% and 55.6%, respectively). The results of this study appeared helpful for differential diagnosis of chicken infectious anemia in the field.
Study on Alternative Methods to Green Malachite in Treatment of Ichthyophthirius multifiliis

Truong Dinh Hoai, Nguyen Van Tuyen, Nguyen Thi Huong Giang, Pham Thi Lam Hong

Received: 19-12-2015 / Accepted: 20-09-2016
The mixture of Green Malachite (MG) and formalin is the most effective chemical used to treat Ichthyophthirius multifiliis and other prasites infecting fish.However, MG was prohibited to usein aquaculture due to its potential risks to the environment, animal and human health. The prohibited use of MG has caused many difficulties to treat this parasite and other aquatic diseases. This study was conducted to examine a new, environmental friendly, safe and effectively method alternative to MG. Formalin 25 ppm (F25) was combined with a high oxidizing PHA (15% peracetic acid, 25% hydrogen peroxideand 25% acetic acid) at different concentrations of 1, 3, 5, 7, 10 ppm (PHA1, PHA3, PHA5, PHA7, PHA10) and the mixture was used to experimentally treat theronts (in vitro), and mature Ichthyophthirius multifiliis (trophonts) parasitized on Grass carp (in vivo), following with comparison to mixture of Green malachite and formalin (F25 + G0.25). The in vitrotest results show that the mixtureof F25 + PHA10 could kill 96.5% theronts within 48h. For in vivotest, treatments were conducted 72h post infection. After 10 days of experimental treatment, the control group (infected without treatment) had a high mortality rate (85.56%).In contrast, the F25 + G0.25 showed high efficiency in controlling this parasite with 94.43% fish survival. The mixtures F + PHA were effective to mitigate mortality rate compared to the control group, in which the mixture of F25 + PHA10 resulted in highest survival rate (92.23%), following with low prevalence and infection intensity, 5.13 and 1.81 parasites/sample at 40 x magnification, respectively. In addition, Ichthyophthirius multifiliis exhibited changes in morphology and moving behaviour. Results of following 10 days post treatment showed that fish treated with F25 + PHA10 recoveredeffectively, stopped mortality and probably created immunity against this parasite.
Isolation and Identification of Biological Characteristicsof Porcine Epidemic Diarrhea Virus

Nguyen Thi Hoa, Nguyen Thi Lan, Truong Quang Lam, Trinh Dinh Thau, Ngo Thi Hanh

Received: 08-12-2017 / Accepted: 21-05-2018
Porcine Epidemic Diarrhea Virus(PEDV) causesacute diarrhea in pigs and this is especially dangerous for piglets. Isolation of PEDV is a pre-requisite for research on production of vaccinesor bioformulationsin the prevention and treatment of the disease.Small intestinesof pigs diagnosed positively with PEDV based on RT-PCR method and vero cell lines were used for this study. PEDV isolationswere determined for the viral titre and the growth curve. A total of 13 PEDV strains were successfully isolated from83diseasesamples. The medium containing 10µg/ml trypsinwas suitable for viral isolation. PEDV was permissive for replication and caused disease at the beginning ofthe second culture passage. Infected vero cell cultures exhibited characteristics CPE by cell-fusion and syncytial formation. CPE occured at 12 hours post infection and the cellswerecompletely destroyed after 36 to 48 hours of infection. In thefirst passage,CPE viral titre ranged from 103,4to 105,7TCID50/mlbut after4 culture passages,theviral titre increasedfrom 105,3 to 107,3TCID50/ml.
Isolation of Bacteria Caused Hemorrhagic Disease for Catfish (Ictalurus punctatus) in The Northern Parts of Vietnam

Trinh Thi Trang, Nguyen Thi Dung, Truong Dinh Hoai

Received: 28-02-2017 / Accepted: 24-04-2017
Cat fish, Ictalurus punctatusis increasingly cultured in the Northern part of Vietnam.However, the diseaseson the fish have not yet studied extensively with limited literature. The study was implemented to isolate pathogenic bacteria causing hemorrhagic disease in catfish and to find out highly effective antibiotics for disease treatment. The result showed that the external signs of the diseases are black skin with lossing mucus and haemorrhagic spots in the head part, fins, and abdomen. The internal signs showed damaged kidney and liquid accumulated abdomen. Thirteen rod shape, gram negative bacterial strains that grew in selected R-S medium were isolated from diseased fish. These strains were identified as Aeromonas hydrophila. Histopathological analysis of hemorrhagic diseased catfish revealed structural changes with slight necroses in muscle and gill filaments. There were many necrotic areas and granulomatous lesions on the liver, kidney and spleen, hydrophytic kidney and spleen tissues. After 2 day period of infection,bacterial strainsCL18, CL20, CL24 and CL26 at 108CFU/fish caused hemorrhagic septicemia in healthy catfish similarly to those in natural infection. Among 7 types of antibiotics, Doxycylin most sensitive with 13 tested isolates. Therefore, the use of Doxycylin on catfish haemorrhagic disease treatment is highly effective.
Assessment of the Possibility White Spot Virus Infectionfrom Red Fiddler (Ucasp.) to White Shrimp (Litopenaeus vannamei)

Truong Thi My Hanh, Huynh Thi My Le, Pham The Viet, Phan Thi Van

Received: 28-02-2017 / Accepted: 10-04-2017
White spot syndrome virus (WSSV), the causative agent of white spot syndrome in shrimp, has a wide host range includingcrabs, zooplankton (Copepods), molluscs, poultry and polychaete.Ucasp.isa common fiddler living in intertidal land, estuary and sourcewaterused for settling pond of shrimp farmsin Nam Đinh, Nghe An and Quang Ninh. WSSV, an important viral pathogen of the shrimp, can replicate in crustacean species,therefore, it is a potential vector for virus transmission. The major aim of this study was to determine whether WSSV can be replicate on Ucasp and transmitted from Ucasp. to shrimp (Litopenaeus vannamei) through water environment. Uca sp. wasinfected withWSSV by injecting suspension containing WSSV in dilution 10-2on the second leg. Results showed that, WSSV was detected in infected fiddler in experimentby PCR method after 107 hours of infection. WSSV was transmitted from Ucasp. to shrimp through water environment horizontally after 83 hours of exposure to Ucasp. carrying WSSV. Our findings support the contention that Ucasp. was a potential vector for virus transmissionandcan be a source of WSSV infection of culture shrimp.
Study on Virulence of PRRS Virus Strain Hua 02 Isolatedin North Vietnamin Piglets

Le Thi Toan, Nguyen Thi Lan, Pham Cong Hoat, Nguyen Thi Ngoc, Nguyen Thi Hoa

Received: 15-12-2016 / Accepted: 24-01-2017
In this study, we investigated the virulence and pathogenicity of porcine reproductive and respiratory syndrome virus (PRRSV) strain HUA 02 in 8-weeks old PRRSV antibody-negative pigs. Experimental pigs were intranasally inoculated with a dose of TCID50 1,74x106/25 µl (2 ml/pig). After inoculation, the pigs were recorded for clinical signs, virus replication in the blood, and macroscopic and microscopic lesions of some tissues for 21 days post inoculation. The results demonstrated that pigs infected with PRRS HUA 02 virus strain had clinical signs and symptoms of moodiness, fatigue, anorexia, high fever, rapid breathing, dyspnea, skin rash and constipation. Reverse transcription PCR (RT-PCR) results revealed the presence of PRRS HUA 02 virus strain in the blood and nasal swabs of infected pigs at 3 and 5 days post inoculation, respectively. Similarly, the viral load in serum quantified by Realtime PCR showed that the PRRSV loads were recorded in the serum at 3 days post infection, and reached highest level in all infected pigs at 9 days post infection. Macroscopic lesions consistently observed included lung inflammation, congestion, hemorrhage and interstitial pneumonia and kidneys with spotting hemorrhage. In lung the lymph nodes were characterized by swelling and hematoma, and in pericardium with hydropericarditisof pigs infected with PRRS HUA 02 virus strain. The microscopic lesions were observed mainly in lungs with bronchoalveolar inflammation, haemorrhagic lymph nodes, and hemorrhagic glomeruli. The results of our study showed that the PRRSV HUA 02 is capable of causing severe disease in pigs with clinical signs, symptoms, macroscopicand microscopic lesions similar to those of highly-pathogenic PRRS virus strain observed previously in North Vietnam.
Virulence in Experimental Pigs of Field African Swine Fever Virus Strain(VNUA - ASFV - L01)Isolated from Infected Pig in Ha Nam Province of Vietnam

Truong Quang Lam, Nguyen Thi Lan, Dao Le Anh, Nguyen Thi Hoa, Nguyen Thi Thu Huong

Received: 18-05-2020 / Accepted: 23-06-2020
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.
Molecular and Biological Characteristics of African Swine Fever Virus Isolated in Some Northern Provinces of Vietnam

Trinh Thi Bich Ngoc, Nguyen Van Tam, Nguyen Thi Thu Huyen, Vu Xuan Dang, Le Van Phan

Received: 25-06-2020 / Accepted: 03-09-2020
African swine fever (ASF) is a highly infectious disease in the domestic and wild pig populations causing tremendous damage to the global swine industry. ASF was first reported in Vietnam on February 1st, 2019 and the disease has spread to 63 provinces in just 7 months. This study aims to investigate the molecular and biological characteristics of ASF viruses isolated from tissue samples of ASF-infected pigs collecting from the northern provinces of Vietnam. The results of virus isolation showed that five ASFV strains had been successfully isolated on PAM (Porcine Alveolar Macrophage) cells, virus titer ranging from 106-107,5 HAD50/ml. The results of the growth curve of the virus on PAM cells disclosed that, with the multiplicity of infection (MOI) = 1, the highest achieved virus titer was 108.160.21HAD50/ml after 96 hours post-infection. The sequencing results of the B646L (p72) gene showed that all present ASFV strains shared 100% nucleotide and amino acid sequence identity with each other. Phylogenetic analysis revealed that all isolated strains belonged to genotype II.
Nghiêncứuảnhhưởngcủanhiệtđộnướcthấpđếnsựgâybệnhcủavirútđốmtrắng(WSSV) trêntômhe NhậtBản(Marsupenaeusjaponicus)

Dang Thi Lua, Ikuo Hirono

Received: 08-07-2015 / Accepted: 09-12-2015
Vi rút đốm trắng (WSSV) là vi rút gây bệnh có độc lực mạnh trên tôm nhưng dễ bị ảnh hưởng bởi các yếu tố gây sốc. Các biện pháp khống chế WSSV đã và đang được nghiên cứu nhưng vẫn chưa được áp dụng vào thực tiễn, do vậy việc quản lý môi trường nhằm hạn chế các yếu tố gây sốc đóng vai trò quan trọng trong việc ngăn ngừa bệnh WSSV. Nghiên cứu này đánh giá ảnh hưởng của nhiệt độ nước, đặc biệt là nhiệt độ nước thấp, đến khả năng gây bệnh của WSSV trên tôm he Nhật Bản. Kết quả nghiên cứu cho thấy tỷ lệ tôm chết sớm và cao nhất, lên tới 100% sau 7 ngày gây nhiễm WSSV, đã quan sát thấy ở nghiệm thức tôm nuôi ở 25oC, tiếp đến là ở nghiệm thức tôm nuôi ở 20oC và tỷ lệ chết thấp nhất ở nghiệm thức tôm được giữ ở 15oC. Nghiên cứu cũng cho thấy, tỷ lệ tôm chết xuất hiện muộn và thấp hơn ở tôm thí nghiệm nuôi ở 25oC nhưng được hạ nhiệt độ xuống 15oC sau khi gây nhiễm khi so với tôm trước và sau khi gây nhiễm đều giữ ở 25oC. Ngược lại, tỷ lệ tôm chết tăng lên ở nghiệm thức tôm giữ ở 15oC sau đó được nâng lên 25oC sau khi gây nhiễm khi so với nghiệm thức tôm giữ ở 15oC trước và sau khi gây nhiễm. Kết quả này được kiểm chứng bằng kỹ thuật PCR và RT-PCR. Kết quả nghiên cứu cho thấy sự gây bệnh của WSSV trên tôm he Nhật Bản phụ thuộc vào nhiệt độ và tôm mẫn cảm nhất với WSSV ở nhiệt độ khoảng 25oC. Nhiệt độ thấp (khoảng 15oC) đã làm chậm sự nhân lên của WSSV trên tôm nhiễm bệnh và ở nhiệt độ này tôm được xem như là nguồn mang mầm bệnh WSSV tiềm ẩn, khi nhiệt độ nước tăng lên bệnh sẽ bùng phát.
Prevalence of Bovine Mastits, Affecting Factors andExperimental Treatment in Phu Dong Dairy Farm

Lai Thi LanHuong, Pham Hong Trang

Received: 11-09-2017 / Accepted: 02-10-2017
The aims of present study were to evaluate the prevalence of mastitis, identify factors influencing disease incidence and test treatment methods in Phu Dong dairy farm in Gia Lam-Ha Noi. The results by California Mastitis Test showed that the prevalence of clinical mastitis was lower than that of sub-clinical cases (10.43% and 25.36%). Based on methylene blue decolorization test, 90% of testing milk samples could be used within 24 -48 hours. The percentage of milk samples discolorized by the dye within 30 minutes was 3.33%. The risk of infection was influenced by the stage of milking. The highest incidence was found in the first month of lactation then reached lowest point at fourth month. The infection rate continued to increase from sixth month toward the end of the lactation period. Age was positively correlated the disease incidence. Cows with higher levels of cross-bred rate had higher rates of mastitis. Treatment with neomycin/amoxicillin combined with pumping inside the infected udders and proper care was effective.

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