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African Journal of Pig Farming ISSN: 2375-0731 Vol. 10 (1), pp. 001-005, January, 2022. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 
 
 
Full Length Research Paper 

  

 

Antiviral activities of ellagitannins against bovine 
herpesvirus-1, suid alphaherpesvirus-1 and caprine 

herpesvirus-1 

 
Neli Vilhelmova-Ilieva1, Ivo Sirakov2, Remi Jacquet3, Stephane Quideau3 and Angel S. 

Galabov1*
 

 
1
Department of Virology, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, 

26 G. Bonchev Str., BG-1113 Sofia, Bulgaria. 
2
Department of Medical Microbiology, Medical Faculty, Medical University of Sofia, 2 Zdrave Street, BG-1431 Sofia, 

Bulgaria. 
3
Universitéde Bordeaux, Institut des Sciences Moléculaires (CNRS-UMR 5255), Institut Européen de Chimie et Biologie, 

2 rue Robert Escarpit, 33607 Pessac Cedex, France. *Corresponding author. E-mail: galabov@microbio.bas.bg. Tel: 
+359 888 287 103. Fax: +359 2 870 0109. 

 
Accepted 23 July, 2021  

 
In vitro antiviral activity of three ellagitannins - castalagin, vescalagin and grandinin was investigated 
against replication of three of the most common herpes viruses infecting animals, namely bovine 
herpesvirus-1 (BoHV-1), suid alphaherpesvirus-1 (SuHV-1), and caprine herpesvirus-1 (CapHV-1). The 
cytopathic effect inhibition test via the neutral red uptake assay in Madin-Darby bovine kidney (MDBK) 
cell culture was applied. The highest activity was demonstrated by castalagin followed by vescalagin 
against replication of SuHV-1, strain A2, with selectivity index values of 336.8 and 309, respectively, 
which are close to that of acyclovir (SI = 540). The activity of grandinin against the replication of SuHV-1 
A2 strain (SI = 40.8) as well as the activity of all three substances against the replication of BoHV-1 
strain K22 was lower but still significant (castalagin SI = 45; vescalagin SI = 42.5; grandinin SI = 32.3). 
Against the E/CH strain of CapHV-1, the three ellagitannins showed a moderate to weak activity: 
Castalagin SI = 19.3, vescalagin SI = 18.8, grandinin SI = 11.8. The results obtained characterize 
compounds tested as perspective antivirals. 

 
Key words: bovine herpesvirus-1, suid alphaherpesvirus-1, caprine herpesvirus-1, ellagitannins, alpha 
acyclovir, antiviral activity.  

 
 
INTRODUCTION 

 
Among the viruses of the Herpesviridae family, some are 
common pathogens for humans and animals. They are 
easily transmitted from an infectious to a healthy 
individual and also they have the ability to form a life-long  

 
 
latent infection. In the herpesvirus species that attack 
animals, it is important that the animals are not only a 
reservoir for viruses, but also that the quality of the meat 
from the infected animals of the point of view of food  
   

  



2 

 

 
 
 

 

production is deteriorated and this leads to great 
economic losses.  

Among the most important herpesviruses infecting 
animals are the members of the subfamily suid 
Alphaherpesvirinae bovine herpesvirus-1 (BoHV-1), 
alphaherpesvirus-1 (SuHV-1), and caprine herpesvirus-1 
(CapHV-1). The economic importance of these viruses 
lies in the high economic losses incurred due to infections 
and the clinical symptoms caused by them. BoHV-1 
infections lead to repeat breeding, rhinotracheitis in 
calves, vulvovaginitis-balanoposthitis in adult animals 
(Haralambiev, 2002), infertility, abortions (Yilmaz et al., 
2016) and neonatal mortality (Wyler et al.,1989). CapHV-
1 causes a similar clinical picture, with neonatal losses of 
up to 80%, repeat breeding 15%, reproductive disorders 
in adult animals - abortions 5% in affected flocks (Sirakov 
2012), and death in kids (Saito et al., 1974).  

Whereas BoHV-1 and CapHV-1 affect cattle and goats, 
SuHV-1 causes infections in a range of various domestic 
and wild animals. In swine, it is associated with abortions 
(~35%) and mortality (3–5%) (Yu et al., 2017), stillbirths 
and decrease in weight gain (Gerdts et al., 1997). It 
affects ruminants, horses, dogs (Quiroga et al., 1998), 
cats and panthers (Glass et al., 1994). Although some 
cases have been reported in humans (Mravak et al., 
1987; Skinner et al., 2001) and that this virus has limited 
zoonotic potential (Khan et al., 2013), SuHV-1 to some 
extent has social importance, as well.  

To date, there is no in general effective therapy of 
herpesvirus infections, nor vaccines created to avoid the 
formation of latent infection. Administration of anomalous 
nucleoside analogues is considered as the most potential 
by its efficacy chemotherapeutic agents used in the 
clinical practice, acyclovir been with largest application. A 
disadvantage of nucleoside analogues is the relatively 
faster development of drug-resistant mutants.  

Limited scope of investigations was carried out on 
chemotherapeutic agents proved in humans against 
herpesvirus infections in domestic animals. Treatment 
with cidofovir has been shown to give good relief of 
clinical symptoms and a decrease in the viral shedding 
titers in CapHV-1 infection in goats (Tempesta et al., 
2008). Chervenkov et al. (2014) demonstrated that 
aqueous extracts of Melissa officinalis L. (Lamiaceae) 
have a marked antiviral effect against SuHV-1. Antiviral 
activity against this virus, as well as against BoHV-1, has 
also been shown by lambda-carrageenan prepared from 
red seaweed (Diogo et al., 2015). Moreover, Lisov et al. 
(2015) demonstrated that 2,5-dihydrobenzoic acid– 
gelatin conjugate has an anti-BoHV-1 effect and 
suggested that this agent would also be effective against 
other alphaherpesvirus subfamily members due to the 
similar mode of entry into the host cells. Some studies on 
the spread and replication of herpesviruses have been 
conducted using natural substances found in many foods 
that a person consumes daily. 

 
 
 
 

 

Recently a special interest as anti-herpetic agents are 
the tannins which are a group of polyphenols, divided into 
two groups of condensed and hydrolysable compounds. 
Of the group of hydrolizable tannins are the ellagitannins. 
There is a lot of evidence in the literature that different 
types of ellagitannins show anti-herpesvirus activity 
(Kurokawa et al., 2001; Chattopadhyay et al., 2010; Lin et 
al., 2011).  

In previous investigations we have also shown that 
three ellagitannins - castalagin, vescalagin and grandinin, 
possess remarkable activity against human herpes 
simplex virus (HSV)-1 and HSV-2, sensitive and resistant 
to acyclovir strains (Vilhelmova et al., 2011; Vilhelmova– 
Ilieva et al., 2014). In the present work we pay attention 
to the activity of these three substances on the replication 
of herpesvirus strains that are animal pathogens. 
 

 
MATERIALS AND METHODS 
 
Cells and viruses 
 
Monolayer cultures of Madin-Darbey bovine kidney (MDBK) cells 
(CCLV 1992, RIE 261/ National Bank for Industrial Microorganisms 
and Cell Cultures, Sofia) were grown in Dulbeco minimal essential 
medium (DMEM) containing 10% bovine fetal serum (Gibco BRL, 
USA), supplemented with 10 mM HEPES buffer (Merck, Germany) 
and antibiotics (penicillin 100 IU/ml, streptomycin 100 μg/ml), in 

CO2 incubator (HERA cell 150, Heraeus, Germany) at 37°C/5% 
CO2. 

Suid alphaherpesvirus 1 (SuHV-1) strain A2, bovine herpesvirus-  
1 (BoHV-1), strain K 22, and caprine herpesvirus-1 (CapHV-1), 
strain E/CH (National Diagnostic and Research Veterinary Institute 
collection strains) were included in the study. The viruses were 
grown in MDBK cell cultivated in MEM-Eagle (Sigma–Aldrich, St. 
Louis, MO, USA) and MEM-Hanks (Sigma–Aldrich, St. Louis, MO, 
USA) supplemented with antibiotics (penicillin 100 IU/ml, 
streptomycin 100 IU/ml), essential amino acids and 2% fetal bovine 
serum (Sigma–Aldrich, St. Louis, MO, USA).  
The virus titers were evaluated by the end-point dilution method, 
based on the cytopathic effect (CPE) inhibition and expressed as 

50% cell culture infectious dose per ml (CCID50/ml). 

 

Compounds tested 
 
Nonahydroxyterphenoyl-containing C-glucosidic ellagitannins: 
castalagin, vescalagin and grandinin, extracted from powdered 
pedunculate oak (that is, Quercus robur) heartwood and purified as 
previously described (Quideau and Feldman, 1996) were tested. 
The substances were dissolved in distilled water to a concentration 
of 0.01 M and then diluted in DMEM to the required concentrations. 
Acyclovir [9-(2-hydroxyethoxymethyl)-guanine] (ACV) was also 
dissolved in DMEM to the required concentration. 

 

Antiviral activity assay 
 
CPE inhibition test was employed on confluent cell monolayer in 96-

well micro plates infected with 100 CCID50 in 0.1 ml (MOI = 
0.0025). After 1 h of virus adsorption, compounds were added in 
various concentrations and cells were incubated for 48 h at 37 °C. 
Inhibition of cytopathic effect was determined using a neutral red 



3 

 

  
 
 

 
Table 1. Antiviral activity of ellagitannins castalagin, vescalagin and grandinin against replication of bovine herpesvirus-1 strain K 22, 
suid alphaherpesvirus 1 strain A2 and caprine herpesvirus-1 strain E/CH.  

 

Compound 
SuHV-1 A2  BoHV-1 K 22 CapHV-1 E/CH 

 

IC50 µM/ml SI IC50 µM/ml SI IC50 µM/ml SI 
 

 
 

Castalagin 0.16 ± 0.073
***,^^^

 336.8 1.2 ± 0.12
***,<<<

 45.0 2.8 ± 1.61
***,>>>

 19.3 
 

Vescalagin 0.22 ± 0.068
***,^^^

 309.0 1.6 ± 0.62
***,<<<

 42.5 3.6 ± 2.11
***,>>>

 18.8 
 

Grandinin 0.87 ± 0.24
***,#

 40.8 1.1 ± 1.07
***,<<<

 32.3 3.0 ± 3.2
***,>>>

 11.8 
 

ACV 2.4 ± 0.55
^^^

 540.0 3.8  ± 0.84
<<<

 341.0 18.4,
>>>

 70.4 
  

***
 p<0.0001, when comparing the values of each ellagitannin with that of ACV for the same strain. 

^^^
 p<0.0001, when comparing the values 

against SuHV-1 (A2) and BoHV-1 (K22) strains of each substance. 
<<<

 p<0.0001, when comparing the values against BoHV-1 (K22) and 

CapHV-1 (E/CH) strains of each substance. 
>>>

 p<0.0001, when comparing the values against SuHV-1 (A2) and CapHV-1 (E/CH) strains of 

each substance.
#
p>0.05, when comparing the values against SuHV-1 (A2) and BoHV-1 (K22) strains of each substance.

 

 

 

uptake assay (Borenfreund and Puerner, 1984). The IC50 values of 
ellagitannins were evaluated, that is, the concentrations that 
inhibited CPE development by 50%. The compounds cytotoxicity 

CC50 (50% cytotoxicity) values were used to determine the 
selective index (SI) values of the compounds tested. Cytotoxicity of 
ellagitannins and ACV was determined on MDBK cells in our 

previous study (Vilhelmova et al., 2011).The values of CC50 of the 
substances were as follows: castalagin - 53.9 µM/ml, vescalagin - 
68.0 µM/ml, grandinin - 35.5 µM/ml and ACV - 1296.0 µM/ml. 

 
Statistical analysis 
 
Data on compounds antiviral effects were analyzed statistically. The 

values of IC50 are presented as means ± SD. The significant 
differences between the effects of each ellagitannin on each virus 
strain are compared with the corresponding acyclovir value; also 
those between the effects of each compound on the different strains 
were done through the One-Way ANOVA where p-values of <0.05 
were considered as significant. 

 

RESULTS 
 

The IC50 values of ellagitannins tested against the three 

herpesviruses (SuHV-1, BoHV-1 and CapHV-1) are 
presented in Table 1. All three ellagitannins show the 
highest activity against SuHV, strain A2. Among them the 
antiviral effect of castalagin attained a pronounced value, 
SI = 336.8, followed by magnitude by the vescalagin’s 
effect, SI = 309. The activity of both substances was 
close to that of ACV SI = 540. Grandinin manifested a 
marked activity but was substantially weaker.  

The three ellagitannins demonstrasted a marked 
activity against BoHV-1, strain K22, with close SI values.  

The most active was castalagin with SI = 45, followed 
by vescalagin with SI = 42.5, and weakest activity was 
shown by grandinin - SI = 32.3. Here, it should be noted 
that, unlike the results obtained against SuHV-1, 
catalagin and vescalagin manifested significantly lower 
activity, while grandinin retained almost the same activity 
as that of ACV against SuHV-1. The weakest activity of 
the three ellagitannins was demonstrated against the 
replication of CapHV-1, E/CH strain. The values of the 
selective indices of castalagin, vescalagin and grandinin 

 
 

 

were SI = 19.3, SI = 18.8, and SI = 11.8, respectively. It 
could mark that the activity of acyclovir against this virus 
was lower than that established vs BoHV-1 and SuHV-1, 
although it was significantly superior (SI = 70.4) 
compared to the effect of ellagitannins. 
 

 

DISCUSSION 

 

Having in mind that the ellagitannins castalagin, 
vescalagin and grandinin, studied in the present work, 
were tested against viruses belonging to the subfamily 
Alphaherpesvirinae of the Herpesviridae family, it is not 
surprising that they manifested activities similar to that 
found against the subfamily members attacking humans 
(HSV-1 and HSV- 2) (Vilhelmova et al., 2011). When 
comparing the activity of ellagitannins on the replication 
of the SuHV-1 strain and their activity against human 
herpesvirus strains, it is noted that their activity is close to 
that observed with HSV-1 (Victoria strain) (Vilhelmova et 
al., 2011).  

On the other hand, the activity of the tested 
ellagitannins on replication of BoHV-1 resembles their 
activity against HSV-2 (strain Bja) (Vilhelmova et al., 
2011), although with lower values and that of castalagin 
and vescalagin was close to that of grandinin. Evidently, 
anti-BoHV-1 activity was considerably inferior when 
compared with the activity against SuHV-1. Similar 
dependence was observed in the ellagitannins activity 
against replication of CapHV-1 strain, where the activity 
was significantly lower and the activity of grandinin can 
be said to be insignificant.  

Different authors have conducted various experiments 
to determine the viral replication stage inhibited by 
ellagitannins. Some ellagitannins have been shown to 
attack the extracellular virions (virucidal effect); others 
have an effect on the adsorption and entry of the virus 
into the host cell. There are ellagitannins that specifically 
inactivate viral DNA polymerase and inhibit replication of 
viral DNA or influence specific viral proteins necessary for 
viral replication (Tan et al., 2013). The results of our 



4 

 

 
 
 

 

study on the mode of anti-herpesvirus action of castalagin 
on the model of HSV-1 (Victoria strain) are in line with 
these data. The compound has been previously shown to 
have (i) a marked direct inactivating effect on extracellular 
virus; (ii) an inhibitory effect on virus adsorption; (iii) 
suppression of early steps in the viral replication cycle 
(Vilhelmova-Ilieva et al., 2013). There are conflicting 
reports about the effect of acyclovir as the sole antiviral 
therapy against CapHV-1. Elia et al. (2015) observed no 
antiviral effect, whereas Camero et al. (2017) report good 
inhibitory activity. Camero et al.  
(2017) explained these contradictory results to the 
different time of acyclovir application in the experimental 
setup. Both studies, however, show good antivirus activity 
of acyclovir in combination with mizoribine. It was 
established that there is a synergistic combined effect of 
acyclovir and mizoribine on the replication of strain 
CapHV-1 (Elia et al., 2015, Camero et al., 2017) and on 
the human HSV-1 (Pancheva et al., 2002). In these 
previous experiments, acyclovir was used in sub-inactive 
concentrations, and with the addition of mizoribine a 
strong synergistic effect was obtained. This effect was 
mizoribine dose dependent.  

Developing effective therapies to suppress herpes viral 
replication is important because the herpes infection of 
animals has not only economic significance for human 
infections but also for food production. In recent years, 
more and more attention has been paid to the ability of 
some herpes viruses to pass between species’ barrier. In 
these cases, a virus that specifically infects a particular 
animal can also infect other species, and in some cases it 
can also be transmitted to humans (Reperant et al., 
2016). Data presented in this study enlarge the scope of 
ellagitannins’ effects on replication of herpesviruses of 
Alphaherpesvirinae subfamily. It would be of interest to 
see the activity of these compounds against 
herpesviruses not belonging to this subfamily. Among the 
pathogens with economic importance are gallid 
herpesvirus 1 (laryngotracheitis virus), ovine herpesvirus 
2 (malignant catarrhal fever virus), equine herpesviruses 
1, 4 and 9 and cyprinid herpesvirus 3. So, experimental 
chemotherapeutic investigations including these viruses 
could be considered as a target of primary importance. 
 

 

CONFLICT OF INTERESTS 

 

The authors have not declared any conflict of interests. 
 

 
REFERENCES 
 
Borenfreund E, Puerner JA (1984). Toxicity determination in vitro by 

morphological alterations and neutral red adsorption. Toxicology 
Letters 24:119-124.  

Camero M, Crescenzo G, Marinaro M, Tarsitano E, Bellacicco AL, 
Armenise C., Buonavoglia C, Tempesta M (2010). Cidofovir does not 

 
 
 
 

 
prevent caprine herpesvirus type-1 neural latency in goats.  
Antiviral Therapy 15:785-788. 

Chattopadhyay  D,  Das  S,  Chakraborty  S,  Bhattacharya  SK  (2010). 
Ethnomedicines for the development of anti-herpesvirus agents. 
Ethnomedicine: Source of complementary therapy pp. 117-147. 
ISBN: 978-81-308-0390-6.  

Chervenkov M, Ivanova T, Kacheva D, Stoeva T (2014}. Antiviral 
activity of Melissa officinalis aqueous extract against pseudorabies 
virus. Comptes rendus de l'Academie bulgare des Sciences 67:879-
888. 

 
Diogo JV, Novo SG, González MJ, Ciancia M, Bratanich AC (2015). 

Antiviral activity of lambda-carrageenan prepared from red seaweed 
(Gigartina skottsbergii) against BoHV-1 and SuHV-1. Research in 
Veterinary Science 98:142-144.  

Elia G, Camero M, Decaro N, Lovero A, Martella V, Tempesta M, 
Buonavoglia C, Crescenzo G (2015). In vitro inhibition of caprine 
herpesvirus 1 by acyclovir and mizoribine. Research in Veterinary 
Science 99:208-211.  

Gerdts V, Makoschey B, Visser N, Mettenleiter TC (1997). Protection of 
pigs against Aujeszky's disease by DNA vaccination. Journal of 
General Virology 78:2139-2146.  

Glass CM, McLean RG, Katz JB, Maehr DS, Cropp CB, Kirk LJ, 
McKeiman AJ, Evermann JF (1994). Isolation of pseudorabies 
(Aujeszky's disease) virus from a Florida panther. Journal of Wildlife 
Diseases 30:180-184.  

Haralambiev H (2002). Animal Viruses. Short guide of Virology (in 
Bulgarian). Pandora Press, Sofia, pp.129-130.  

Khan SU, Atanasova KR, Krueger WS, Ramirez A, Gray GC (2013). 
Epidemiology, geographical distribution, and economic 
consequences of swine zoonoses: a narrative review. Emerging 
Microbes and Infections 2(1):1-11.  

Kurokawa M, Hozumi T, Tsurita M, Kadota S, Namba T, Shiraki K 
(2001). Biological characterization of eugeniin as an anti-herpes 
simplex virus type 1 compound in vitro and in vivo. Journal of 
Pharmacology and Experimental Therapeutics 297:372-379.  

Lin LT, Chen TY, Chung CY, Noyce RS, Grindley TB, McCormick C, Lin 
T-C, Wang GH, Lin CC, Richardson CD (2011). Hydrolyzable tannins 
(chebulagic acid and punicalagin) target viral glycoprotein-
glycosaminoglycan interactions to inhibit herpes simplex virus 1 entry 
and cell-to-cell spread. Journal of Virology 85:4386-4398.  

Lisov A, Vrublevskaya V, Lisova Z, Leontievsky A, Morenkov O (2015).  
A 2, 5-dihydroxybenzoic acid–gelatin conjugate: the synthesis, 
antiviral activity and mechanism of antiviral action against two 
alphaherpesviruses. Viruses 7:5343-5360.  

Mravak A, Bienzle U, Feldmeier H, Hample H, Habermehl KO (1987). 
Pseudorabies in man. Lancet 1:501-502  

Pancheva S, Dundarova D, Remichkova M (2002). Potentiating effect of 
mizoribine on the anti-herpes virus activity of acyclovir. Zeitschrift für 
Naturforschung C 57(9-10):902-904.  

Quideau S, Feldman KS (1996). Ellagitannin chemistry. Chemical 
Reviews 96: 475-503.  

Quiroga MI, Nieto JM, Sur J, Osorio F (1998). Diagnosis of Aujeszky's 
disease virus infection in dogs by use of immunohistochemistry and 

in‐situ hybridization. Transboundary and Emerging Diseases 45:75-
81.  

Reperant LA, Brown IH, Haenen OL, de Jong MD, Osterhaus ADME, 
Papa A, Rimstad E, Valarcher J.-F, Kuiken T (2016). Companion 
animals as a source of viruses for human beings and food production 
animals. Journal of Comparative Pathology 155:S41-S53.  

Saito JK, Gribble DH, Berrios PE, Knight HD, McKercher DG (1974). A 
new herpes virus isolate from goats: preliminary report. American 
Journal of Veterinary Research 35:847-848.  

Sirakov I (2012). Investigation of herpesvirus infection in goats (PhD 
thesis) (in Bulgaian), Bulgarian Food Safety Agency, Nat. Diagn.  
National Veterinary Research Institute, Sofia. DOI:  
10.13140/RG.2.2.21740.39046.  

Skinner GRB., Ahmad A, Davies JA (2001). The infrequency of 
transmission of herpesviruses between humans and animals; 
postulation of an unrecognized protective host mechanism. 



5 

 

 
 
 

 
Comparative Immunology, Microbiology and Infectious 
Diseases24:255-269.  

Tan WC, Jaganath IB, Minikam R, Sekaran SD (2013). Evaluation of 
antiviral activities of four local Malaysian Phyllanthus species against 
herpes simplex viruses and possible antiviral target. International 
Journal of Medical Sciences 10:1817-1829.  

Tempesta M, Crescenzo G, Camero M, Bellacicco AL, Tarsitano E, 
Decaro N, Neyts J, Martella V, Buonavoglia C (2008). Assessing the 
efficacy of cidofovir against herpesvirus-induced genital lesions in 
goats using different therapeutic regimens. Antimicrobial Agents and 
Chemotherapy 52(11):4064-4068.  

Vilhelmova N, Jacquet R, Quideau S, Stoyanova A, Galabov AS (2011). 
Three-dimensional analysis of combination effect of ellagitannins and 
acyclovir on herpes simplex virus types 1 and 2. Antiviral Research 
89:174-181.  

Vilhelmova-Ilieva N, Jacquet R, Quideau S, Galabov AS (2013). Initial 
study on the mode of action of castalagin against herpes simplex 

virus. Journal of Virology (Abstracts 5
th

 European Congress of 
Virology, Lyon, 11-14.09.2013) 17.  

Vilhelmova-Ilieva N, Jacquet R, Quideau S, Galabov AS (2014). 
Ellagitannins as synergists of ACV on the replication of ACV-resistant 
strains of HSV 1 and 2. Antiviral Research 110:104-114. 

  
  

 
 

 
Wyler R, Engels M, Schwyzer M (1989). Infectious bovine 

rhinotracheitis/vulvovaginitis. In: Wittmann, G. (Ed.), Herpesvirus 
Diseases of Cattle, Horses and Pigs. Kluwer Academic Publishers, 
Boston, Dordrecht, London pp. 1-72.  

Yilmaz V, Coskun N, Sahin M (2016). Molecular detection of bovine 
herpes virus-1 (BoHV-1), bovine herpes virus-4 (BoHV-4) and bovine 
viral diarrhoea virus (BVDV) in aborted ruminant fetuses from Kars 
province in Northeast Turkey. Indian Journal of Animal Research 
50:551-556.  

Yu X, Zhou Z, Hu D, Zhang Q, Han T, Li X,Tian K (2014). Pathogenic 
pseudorabies virus, China, 2012. Emerging Infectious Diseases 
20:102-104. 


