Bovine herpesvirus-1 in three major milk sheds of Ethiopia: Serostatus and association with reproductive disorders in dairy cattle

Seroprevalence of and Associated Risk Factors for Bovine Viral Diarrhea in Dairy Cattle in and Around Nekemte Town, East Wallaga, Oromiya Regional State, Ethiopia

Bovine viral diarrhea virus (BVDV) is an important pathogen affecting dairy cattle all over the world by causing significant economic losses due to reproductive and respiratory problems, immunosuppressive effects, increased risk of morbidity, and calf mortality. A cross-sectional study was conducted from February 2021 to August 2021 to determine the seroprevalence of bovine viral diarrhea (BVD) and identify risk factors associated with its occurrence in and around Nekemte Town of Ethiopia. Blood samples were collected from 305 dairy cattle of 41 herds by using cluster-sampling method. All sampled animals were identified by their age, breeds, origin, parity, pregnancy status, and history of reproductive and respiratory problems. Competitive ELISA was used in the laboratory to detect the presence of antibodies in the serum. At the animal and herd level, descriptive statistics were utilized to assess the amount of BVDV viral antibody circulation, and multivariable logistic regression analysis was employed to detect potential risk variables. The result demonstrates 9.84% (95% confidence interval (CI): 6.49-13.18) and 28.52% (95% CI: 23.46-33.59) seroprevalence of BVDV antibody at individual and herd level, respectively. Abortion (odds ratio (OR) = 2.75; p = 0.019), retention of fetal membrane (OR = 3.33; p = 0.011), purchasing of animals (OR = 2.98; p = 0.017), and pregnancy (OR = 3.16; p = 0.019) were variables significantly associated with the seropositivity of BVDV. Herd size was found to be substantially linked with BVDV infection at the herd level (p = 0.009). These moderate seroprevalence of BVDV results indicate that the virus is widely spread among dairy cattle at various farms in and around Nekemte Town, hurting dairy farm production and productivity. To reduce the seroprevalence of this infectious agent, cows with a history of reproductive disorders should be tested, and new animals should be quarantined before being introduced into herds, and more research should be done to assess the impact of reproductive failure and other effects associated with this virus.

Seroprevalence and associated risk factors of bovine herpesvirus 1 in smallholder dairy farms in two districts of Gondar zones, North-West Ethiopia

Bovine herpesvirus 1 (BoHV-1) is the infectious agent that causes infectious bovine rhinotracheitis (IBR), a disease affecting the reproductive and respiratory systems of cattle. Significant economic losses result from infectious bovine rhinotracheitis because of metritis, abortions, placenta retention, recurrent breeding, animal deaths, and losses from trade restrictions. Reports of the diseases have been made in southern, southwestern and in major cities that kept improved breed of dairy cows in Ethiopia with prevalence ranging from 28.5-67 %. However, there is insufficient information available regarding the frequency and spread of IBR in the northwest part of the nation. In northwest Ethiopia, a cross-sectional study was carried out to estimate seroprevalence of BoHV-1 and identify associated risk factors. Dairy farms and farm owners were chosen using a multistage cluster sampling technique, while dairy cattle were chosen using a simple random sample technique. Four hundred and thirty-one dairy cattle from 177 herds in the Debark and Lay-Armachiho districts in the North and Central Gondar zones, respectively, both in Northwestern Ethiopia, were selected to provide serum samples. Owners of dairy animals provided information via questionnaires. Using a competitive enzyme-linked immunosorbent assay (c-ELISA), anti-BoHV-1 antibodies were detected in serum samples. To identify risk factors, univariable and multivariable mixed effect logistic regression models were used. We calculated animal level and herd level seroprevalence of 72 % (95 % CI: 64.9-78.4 %) and 85.7 % (95 % CI: 79.8-90 %), respectively. Parity was associated with seroprevalence of BoHV-1; cows with higher parity had increased seroprevalence of BoHV-1. Bull mating [OR=3.13, (95 % CI: 1.74-5.64)] compared to AI and Debark district [OR=2.73 (95 % CI: 1.63-4.57)] compared to Lay-Armachiho district, were associated with seroprevalence of BoHV-1. The study had shown that BoHV-1 is circulating out of the major cities and also on dairy farms keeping local breeds of dairy cows in Gondar zones, North-West Ethiopia. This suggests need of attention in prevention and control of BoHV-1.

Seroprevalence of bovine Herpesvirus-1, bovine viral diarrhoea virus, Neospora caninum and Coxiella burnetii in dairy cows in Ethiopia

BACKGROUND

The reproductive problem is an animal health-related bottleneck that constrains livestock genetic improvement efforts in tropical countries such as Ethiopia. The infectious causes of reproductive disorders are one cause of decreased reproductive efficiency. This study aimed to determine the seroprevalence to Bovine Herpesvirus-1 (BHV1), Bovine Viral Diarrhea Virus (BVDV), Neospora caninum (N. caninum) and C. burnetii (C. burnetii) exposures in dairy cows with reproductive disorders in selected areas of Ethiopia. Overall, 164 serum samples were collected from October 2018 to May 2019 from animals with a history of reproductive disorders. The collected sera were tested for antibody titers to Brucella species, N. caninum, BVDV, BHV1, C. burnetii and Chlamydophila abortus (C. abortus) using Rose Bengal and ELISA.

RESULTS

The apparent seroprevalence of BHV1, BVDV, N. caninum and C. burnetii were 61%, 33.5%, 4.9% and 0.6%, respectively. Among the selected study areas, the mean apparent seroprevalence was significantly greater in Bishoftu (35.9%), Holeta (34.2%) and Adaberga (28.6%) than in Mekelle (9.9%) and Ambo (16.2%). Among the specific seroprevalence in specific areas, BHV1 was the most common in Adaberga, with an apparent seroprevalence of 92.9%. Similarly, the seroprevalence of BVDV was the highest in Holeta, with an apparent seroprevalence of 73.3%. On the other hand, no seropositive animal to Brucella spp. or C. abortus was found in these study areas.

CONCLUSION

BVDV and BHV1 seroprevalence was higher in dairy cattle with a history of reproductive disorder in Ethiopia as compared to the seroprevalence of N. caninum and C. burnetii.

Seroprevalence and Associated Risk Factors of Infectious Bovine Rhinotracheitis (IBR) and Animal Owners' Knowledge, Attitude and Practice (KAP) Towards the Disease in Selected Districts of East Wollega Zone, Oromia Regional State, Ethiopia

PURPOSE

Infectious bovine rhinotracheitis (IBR) is one of the most important diseases affecting production and productivity.

METHODOLOGY

Cross-sectional study was aimed at to determine the seroprevalence of IBR and associated risk factors, and animal owners' knowledge, attitude and practice towards the disease from April 2021 to June 2022. Accordingly, a total of 384 serum samples were collected from both crossbreed (70) and local breed (314) cattle from purposively selected districts of East Wollega zone of Western Ethiopia. Competitive enzyme-linked immunosorbent assay (ELISA) was used for testing glycoprotein antibodies (anti-gB) for bovine herpes virus-1 (BoHV-1) virus in collected serum, and the obtained data were analysed by multiple logistic regressions by using R software 3.62 version. However, questionnaire data were analysed for descriptive statistics by SPSS version 20.0 (IBM. Corp, 2011).

RESULT

The total prevalence of IBR in the study area was found to be 70.54% at herd and 80.47% at individual cattle level. The significant association (p < 0.05 $ < \ 0.05$ ) was found for breed, age, body condition and herd size but not for district and sex as risk factors. The BoHV-1 virus seropositivity in adult animals increased significantly, with an odds ratio of 1.65 (95% CI 0.705-3.85) compared to young. Local breed cattle were 2.055 times more likely to test positive for IBR with an odds ratio of 0.77 (95% CI 0.23-2.22) compared to crossbreed cattle. The chances of cattle in medium herds testing positive for the BoHV-1 virus with an odds ratio of (1.78 95% CI 1.303-7.50) are greater than the chances of cattle in smaller herds testing positive. The survey results showed that 70% of animal owners identified IBR as a major challenge in animal production, whereas 35% mentioned long calving intervals. However, 92% of the participants were not informed about the level of knowledge and attitude regarding particular diseases such as IBR.

CONCLUSION

This study showed that there is a high prevalence of IBR in cattle in the study area, and that owners have low awareness of the disease. Therefore, it is necessary to develop an immediate control system and conduct additional research on molecular detection to evaluate its effects on reproductive performance.

Seroepidemiology of bovine alphaherpesvirus 1 (BoAHV-1) in commercial and smallholder dairy herds in north Shewa, central highlands of Ethiopia

Bovine alphaherpesvirus 1 (BoAHV-1) is the most important respiratory and reproductive disease-causing pathogen in dairy cattle. Despite BoAHV-1 has become widespread and a major challenge to the dairy industry, little is known about its epidemiology in dairy herds in Ethiopia. A cross-sectional study was conducted from November 2022 to May 2023 to determine the seroprevalence and potential risk factors associated with BoAHV-1 seropositivity in dairy herds in North Shewa, the central highlands of Ethiopia. A total of 511 blood samples were collected from randomly selected cattle herds (n = 142) and examined antibodies against BoAHV-1 using ELISA test. A retrospective survey was also done to gather information related to reproductive disorders. The overall seroprevalence of BoAHV-1 was 61.84% (95% CI: 57.53-65.97) at the animal level and 85.21% (95% CI: 78.28-90.21) at the herd level. Multivariable logistic analysis revealed that the risk of being BoAHV-1 seropositive was nine times higher in cows older than six years (OR = 9.16; 95% CI: 3.09-27.16; P = 0.000), five times higher (OR = 4.51; 95% CI: 1.23-16.53; P = 0.019) in cows with a history of abortion, three times higher (OR = 2.75; 95% CI: 1.72-4.22; P = 0.029) in cows with a history of retained fetal membrane, and three times higher (OR = 2.83; 1.86-9.31; P = 0.03) in animals with clinical signs of ocular and/or nasal discharge. This study demonstrates a significant circulating of BoAHV-1 in the dairy cattle population in study districts. Thus, a comprehensive approach that includes strict farm biosecurity and vaccination should be practiced for effective BoAHV-1 control and prevention and to promote the growing dairy industry in the central highlands of Ethiopia.

Seroprevalence and associated risk factors of equine herpesvirus type-1/-4 in selected districts of Northwest Amhara, Ethiopia

This study aimed to estimate the prevalence, determine the distribution, and identify the epidemiological risk factors of EHV-1/-4 infections in selected districts of Northwest Amhara Region. 460 serum samples were collected from equines using multistage cluster sampling technique, and a competitive Enzyme-linked immunosorbent assay (cELISA) was performed. Various risk factors for the occurrence of EHV-1/-4 were considered. Statistical analysis was performed using R version 4.3.1. 65.9% (303) equids were tested positive for antibodies against EHV-1/-4. Based on district, the highest prevalence was recorded in Wogera (86.1%), while the lowest was in Debark (47.4%). There was a significant difference (p <0.05; 95% CI: 1.1067993-3.682843) in the prevalence of EHV-1/-4 among species and donkeys are 2.019 times more likely to get an EHV infection than horses. The prevalence of EHV-1/-4 was highest in equids with the age of 3-8 years and lowest in < 3 years, and the difference was statistically significant (p <0.05; 95% CI: 1.9812042-6.771820). Statistically significant variation (p <0.05; 95% CI: 1.1173822-2.684013) was also observed between sex of equids in which females had 1.73 times higher chance to get EHV infection than males. Higher prevalence was found in lactating equids (81.6%), followed by pregnant equids (74.6%), and dry equids (66.4%). Generally, this study indicated a high and wide distribution of EHV-1/-4 infection in the study area, which needs due attention. Devising strategies to prevent and minimize the spread and occurrence of the infection is crucial.

Molecular detection of bovine alphaherpesvirus-1 in cases of reproductive disorders among cattle and buffaloes in Gujarat

Bovine alphaherpesvirus-1 (BoAHV-1) is an important viral pathogen that causes significant economic losses to the dairy industry. The present study aimed to determine the prevalence of BoAHV-1 in cases of bovine reproductive disorder. Clinical samples were collected from various villages in Gujarat using specialized FTA® cards and were tested using real-time PCR assay targeting the gB gene of BoAHV-1. Out of 401 animals, 18.20% (95% CI: 14.74-22.28%) tested positive for BoAHV-1 DNA. The percentage positivity of BoAHV-1 was 20.37% in abortion cases and 19.55% in retention of fetal membrane cases, while only one out of nine metritis cases screened in the study was positive for BoAHV-1 DNA. A higher percentage positivity in buffaloes (22.14%) compared to cattle (16.30%) was recorded, but this difference was not statistically significant (p = 0.169). The frequency of BoAHV-1 detection was higher among crossbreeds (16.76%) and exotics (19.61%) than among indigenous cattle (8.82%), although this difference was not statistically significant (p = 0.400). There was also no significant difference in frequency distribution among animals of varying parity, ranging from 15.20 to 33.33% (p = 0.540). This study confirms the widespread circulation of BoAHV-1 and highlights the need for its control and prevention.

Seroprevalence and risk factors associated with bovine herpesvirus 1 (BHV-1) infection in dairy cattle in southern and central Ethiopia

Bovine herpesvirus 1 (BHV-1) is an important pathogen of cattle with a worldwide distribution. It occurs as a subclinical, mild or severe disease. The clinical signs may vary widely with respiratory, genital, ocular and encephalomyelitis form. This cross-sectional study was carried out between May 2019 and March 2020 with the aim to estimate the seroprevalence of bovine herpesvirus 1 (BHV-1) and to identify related potential risk factors in dairy cattle in central and southern Ethiopia. A total of 954 serum samples were obtained from randomly selected dairy cattle in 98 herds. The samples were collected from animals over 6 months old and tested using a BHV-1 antibody blocking enzyme linked immunosorbent assay (b-ELISA). The study showed that the animal- and herd-level seroprevalence of BHV-1 was 30.0 % (95 % CI: 21.7, 39.9) and 75.5 % (95 % CI: 65.9, 83.1), respectively. Multiple logistic regression model demonstrated that adult animals (> 2.5 years) (OR = 2.4, 95 % CI: 1.1, 5.5) had higher seroprevalence of BHV-1 compared to their counterparts (p < 0.05). Cattle in farms using artificial insemination (AI), and both AI and bulls had a 3.9 (95 % CI: 1.2, 13.3) and 5.1 (95 % CI: 1.8, 14.8) odds of being seropositive, respectively, compared to farms using bulls only. Arrangement of animals in a tail-to-tail fashion appeared to be protective against BHV-1 infection (p < 0.05). However, source of the animal was not associated with BHV-1 serostatus (p > 0.05). The animal- and herd-level prevalence recorded in our study confirms that BHV-1 infection is widespread and remains endemic in dairy cattle of central and southern Ethiopia.

Seroepidemiological study of bovine alphaherpesvirus 1 in the dairy cattle herds of Addis Ababa, Ethiopia

Bovine alphaherpesvirus 1(BoHV-1) causes respiratory disease, abortions, and genital disorders in cattle. Although BoHV-1 has been known to cause severe economic damage to the dairy industries, little is known about its epidemiology in dairy cattle of Addis Ababa, Ethiopia. The present study aimed to determine the seroprevalence and the risk factors associated with the occurrence of BoHV-1. A total of 369 blood samples from 115 dairy herds were collected using a proportional stratified random sampling method and examined antibodies against BoHV-1 using ELISA test. A questionnaire survey was done to gather information related to farm demographics and reproductive disorders. Univariate and multivariate mixed-effect logistic regression analyses were used. The overall seroprevalence of BoHV-1 was detected in 21 % (95%CI: 17-25%) and 32 % (95%CI: 24-42 %) at animal and herd levels, respectively. A multivariable mixed effect logistic regression model revealed that adult cattle had 14 times (OR = 14.32; 95 % CI: 2.53-81.5; P = 0.003) more likely to increase the risk of being BoHV-1 seropositive than young cattle. Purchased cattle had 4 times (OR = 4.15; 95 % CI: 1.36-12.66, P = 0.012) more likely to increase the risk of being BoHV-1 seropositive than homebred cattle. The risk of being BoHV-1 seropositive was 195 times higher in herds using bulls (OR = 195.51; 95 % CI: 3.62-1056.51; P = 0.010) than in herds using artificial insemination only for breeding. BoHV-1 seropositivity was significantly associated with cows that had a history of abortion (OR = 6.89; 95 % CI: 1.97-22.76; P = 0.002), retained placenta (OR = 3.26; 95 % CI: 1.32-8.07; P = 0.010), and repeat breeding (OR = 3.64; 95 % CI: 1.08-12.18; P = 0.036). This study demonstrated the gaps in the selection of BoHV-1 free bulls for breeding as well as limited farm biosecurity practices. Thus, awareness creation for dairy farmers on good farm biosecurity practices including vaccination should be initiated.

Prevalence of bovine herpesvirus 1 antibodies and risk factors in dairy cattle of Iran's central desert

Bovine herpesvirus type 1 (BoHV 1) is a major bovine pathogen spreading worldwide and causing extensive damage to the livestock industry. BoHV causes respiratory, genital, and neurological disorders. A cross-sectional study was performed for the first time to estimate the seroreactivity to BoHV 1 and related risk factors among Iran's central desert dairy cattle. A total of 800 blood samples was randomly collected from 76 unvaccinated herds. Samples were tested with an indirect enzyme-linked immunosorbent assay (ELISA) commercial kit to detect BoHV 1 antibodies. The logistic regression model was used to analyze the data. BoHV 1 seroreactivity at animal and herd levels was 50% and 65%, respectively. Herd size was recognized as a risk factor (OR = 2.65, CI = 1.61-4.37) for seroreactivity to BoHV using GLM (p < 0.05). The high prevalence of BoHV 1 antibodies in the study area indicates the need to implement educational programs on the importance of the disease and design methods to control and prevent virus distribution.

Serodiagnosis and Risk Factors Associated with Infectious Agents of Reproductive Diseases in Bovines of Chiquinquirá, District of Boyacá (Colombia)

The productivity of cattle farms is affected by infectious and noninfectious factors that generate economic losses and cause reproductive failure represented by low conception rates, embryonic mortality, abortions, and fetal mummification. The infectious agents that most impact the reproductive health of the bovine species from conception to birth are bovine herpesvirus type 1 (BoHV-1) causing infectious bovine rhinotracheitis (IBR), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus type 3 (PI3), Neospora caninum and Leptospira spp. The objective of this study was to diagnose the presence of BoHV-1, bovine viral diarrhea (BVD), PI3, Neospora caninum, and Leptospira spp. by serology and identify the risk factors associated with infectious agents of reproductive interest in bovines of Boyacá (Colombia). A descriptive cross-sectional study was developed, with simple random sampling, where a sample size of 601 female cattle of Holstein, Jersey, and Normande breeds of different age groups was determined. Blood samples were taken and processed using the indirect ELISA technique (SYNBIOTICS®, SERELISA® BVD p80 Ab Mono Blocking, Ingezim R.12.NC.K, PRIMACHECK VPI-3®) and the MAT test for the diagnosis of bovine leptospirosis. The data were processed with the statistical program Epi Info™. The highest apparent seroprevalence was established for infectious bovine rhinotracheitis (61.1%), followed by BVD (37.6%), PI3 (40.9%), neosporosis (51.1%), and leptospirosis (14.8%). Variables such as age >4 years and Holstein breed for IBR and >4 years for BVD were established risk factors. Considering our results, we suggest implementing prevention and control plans that include vaccination as a prophylactic measure and biosecurity tools that reduce the probability of contagion and transmission of pathogens.

Seroprevalence and risk factors associated with bovine herpesvirus 1 in dairy herds of Colombia

Background and Aim: Infectious bovine rhinotracheitis (IBR) is an infectious disease widely distributed globally and is considered the main cause of various reproductive and respiratory tract diseases in cattle and buffaloes. This study aimed to estimate seroprevalence and determine risk factors associated with the presentation of IBR in the municipality of Sotaquirá, Boyacá (Colombia). Materials and Methods: A descriptive cross-sectional study with simple random sampling was performed, and the sample size was 1,000 cattle. Blood samples were obtained by coccygeal venipuncture and processed through indirect enzyme-linked immunosorbent assay using the Synbiotics® kit (Zoetis, New Jersey, USA) with a sensitivity and specificity of 96% and 98%, respectively. Data were processed using the statistical program EpiInfo® (Centers for Disease Control and Prevention; Atlanta, Georgia). Results: A high seroprevalence of 57.5% was established. Seroprevalence was the highest in cattle >4 years of age (65.0% apparent seroprevalence [AS]; 67% true seroprevalence [TS]) and in the Holstein breed (65.5% AS; 67.8% TS). The breed and age of the animals were significantly associated with each other. The Holstein breed, age group >4 years, uncertified semen, and fetal death were established as risk factors for IBR. In comparison, the age groups of <1 and 1–2 years and the Normande breed were established as protective factors against the bovine herpesvirus-1 virus. Conclusion: Management factors, such as livestock from other owners and animal purchases, which affect disease presentation, are evident. The implementation and development of novel prevention and control measures for IBR at the national level are necessary.

Risk assessment and seroprevalence of bovine herpesvirus type 1 infection in dairy herds in the inner Aegean Region of Turkey

This cross-sectional study was performed to investigate the seroprevalence and associated risk factors of bovine herpesvirus type 1 (BoHV-1) infection in dairy cattle herds in Afyonkarahisar province in the Aegean Region of Turkey. Blood samples were collected from 602 cattle from 56 unvaccinated dairy herds between May 2018 and June 2019. Animal and herd-level epidemiological information was collected with a questionnaire during blood collection. Specific antibodies against BoHV-1 and bovine viral diarrhea virus (BVDV) were detected by using a virus neutralization test and a commercial indirect ELISA kit, respectively. Univariable and multivariable logistic regression analyses were used to determine any association between categorical variables and BoHV-1 seropositivity. The animal-level and herd-level seroprevalences of BoHV-1 infection were determined to be 39.53% (95% confidence interval, CI: 35.71-43.50) and 73.21% (95% CI: 60.41-83.04), respectively. Within-herd prevalence was more than 50% in 34.14% of infected herds. Cattle age (odds ratio, OR= 2.34, 95% CI: 1.58-3.44), BVDV infection (OR= 7.74, 95% CI: 5.08-11.76), and the presence of goats in the herd (OR= 2.84, 95% CI: 1.91-4.19) were identified as risk factors for BoHV-1 seropositivity by the multivariable logistic regression model. This is the first study conducted in Turkey using two-layer sampling and logistic regression analyses to determine the herd-level and animal-level seroprevalence and associated risk factors of BoHV-1 infection.

Infectious bovine abortions: observations from an organized dairy herd

Abortions in dairy animals can be caused by several infectious agents. Identification of the actual causal agent(s) is important for formulating suitable control strategies. A 3-year (2016-2018) longitudinal study was conducted in a dairy farm following an abortion storm in the mid- to late gestations. The investigation focused on the seven major infectious abortifacient in cattle, viz. bovine alphaherpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV), Neospora caninum, Brucella abortus, Coxiella burnetii, Leptospira Hardjo, and Listeria monocytogenes. High seroprevalence was observed for BVDV (79.4%), Leptospira (70.5%), BoHV-1 (53.5%), and Brucella (45.0%) at the beginning of the investigation (August 2016). The incidence proportion increased for BVDV, Leptospira, and Brucella in the following years of the investigation. A strong association of Brucella seropositivity with history of abortion (OR = 3.27) was recorded. Incidence of BoHV-1 reduced during the period of study coincident with systematic IBR inactivated marker vaccination of the herd. Sixty-four abortion cases were investigated for the identification of causative agent(s) by microbial culture, serological (ELISA), and molecular detection (PCR/ real-time PCR). Antibodies to BVDV, Brucella, BoHV-1, Leptospira, Neospora, and Coxiella were detected in 63, 61, 56, 35, 5, and 6 aborting cattle, respectively. Real-time PCR/PCR of clinical specimens detected DNA of Brucella, BoHV-1, Coxiella, Leptospira, and Listeria in 34, 13, 12, 9, and 4 abortion cases, respectively. BVDV and Neospora were not detected in any specimen samples. Brucella abortus isolated from the farm was determined as ST1 by multi-locus sequence typing (MLST). DNA of multiple agents were detected in 21 of the 64 cases (43.75%). Overall, the data suggests, Brucella was the major causative agent, although multiple causative agents circulated in the farm.

Importance of Viral Disease in Dairy Cow Fertility

Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations. BTV-8 also impairs the development of hatched blastocysts; furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes.

Protective immunity following vaccination with a recombinant multiple-epitope protein of bovine herpesvirus type I in a rabbit model

Bovine herpesvirus type 1 (BoHV-1) causes considerable economic losses to the cow industry. Vaccination remains an effective strategy to control the diseases associated with BoHV-1. However, live vaccines present safety concerns, especially in pregnant cows; thus, nonreplicating vaccines have been developed to control the disease. The envelope glycoproteins of BoHV-1 induce a protective immune response. In this work, selected epitopes on glycoproteins gD, gC, and gB were constructed in triplicate with linker peptides. Vaccination of rabbits demonstrated that P2-gD/gC/gB with AAYAAY induced higher specific antibodies than that with GGGGS linker. P2-gD/gC/gB with AAYAAY linker was fused with bovine interleukin-6 (BoIL-6) or rabbit IL-6 (RaIL-6) and bacterially expressed. Rabbits were intramuscularly immunized with 100 μg of P2-gD/gC/gB-BoIL-6, P2-gD/gC/gB-RaIL-6, P2-gD/gC/gB, P2-gD/gC/gB plus BoIL-6, P2-(gD-a)3-BoIL-6, or P2-(gD-a)3 emulsified with ISA 206 adjuvant thrice at 3-week intervals. P2-gD/gC/gB-BoIL-6 generated a higher titer of BoHV-1-specific antibodies, neutralizing antibodies, interferon (IFN)-γ, and IL-4 compared with P2-gD/gC/gB plus BoIL-6, P2-gD/gC/gB-RaIL-6, or other formulation. P2-gD/gC/gB-BoIL-6 triggered similar levels of antibodies and significantly higher titer of IFN-γ and IL-4 compared with inactivated bovine viral diarrhea (BVD)-infectious bovine rhinotracheitis (IBR) vaccine. Rabbits vaccinated with P2-gD/gC/gB-BoIL-6 dramatically reduced viral shedding and tissue lesions in lungs and trachea after viral challenge and reactivation compared with those with P2-gD/gC/gB plus BoIL-6 or P2-gD/gC/gB-RaIL-6. P2-gD/gC/gB-BoIL-6 provided protective effects against viral shedding and tissue pathogenesis similar to those of the inactivated vaccine. The data confirmed the safety and immunogenicity of multiple-epitope recombinant protein and a potential vaccine candidate to control the disease, especially for pregnant cattle.

Mapping a highly conserved linear neutralizing epitope at the N-terminus of the gD glycoprotein of bovine herpesvirus type I using a monoclonal antibody

Bovine herpesvirus type 1 (BoHV-1), a member of the Alphaherpesvirinae subfamily, causes significant economic losses to the cattle industry worldwide. Envelope glycoprotein D (gD) of BoHV-1 plays an essential role in the viral entry into permissive cells and possibly cooperates with other envelope glycoproteins. The herpesvirus gD induces a protective immune response against diseases in cattle or animal models. Mapping epitopes on gD will facilitate the understanding of the BoHV-1 pathogenesis and development of alternative vaccines against various diseases associated with the virus. In this study, a monoclonal antibody (MAb), designated as 3C1, was generated using naive BoHV-1 in vaccination of mice, demonstrating that 3C1 was specific to gD and represents a neutralizing activity against BoHV-1 infection in Madin-Darby bovine kidney cells. Panels of overlapping gD recombinant proteins with glutathione S-transferase tag were prepared to define the epitope recognized by 3C1. The data demonstrated that the N-terminus of gD ²³APRVTVYVD³¹ was recognized by 3C1. Furthermore, the ²⁶VTVYVD³¹ motif was the minimal amino acid sequence for the recognition. The epitope identified in this study is highly conserved among the typical strains of BoHV-1 and BoHV-5, suggesting that this epitope may be useful in the diagnosis of diseases. In addition, the defined region on gD of BoHV-1 might be essential in viral entry upon comparison with the prototype virus in herpes simplex virus (Alphaherpesvirinae). The data will elucidate the roles of gD of BoHV-1 in viral entry and pathogenesis and its potential application for the development of vaccine candidates and diagnostic techniques based on the conserved epitopes on gD or in combination with those of other herpesvirus glycoproteins.

Mapping a highly conserved linear neutralizing epitope on gD glycoprotein of bovine herpesvirus type I using a monoclonal antibody

Bovine herpesvirus type 1 (BoHV-1), a member of the Alphaherpesvirinae, causes a variety of diseases, which result in significant economic losses worldwide. Envelope glycoprotein D (gD) of BoHV-1 plays an important role in viral entry into the permissive cells, and protective immune response. The fine mapping epitope on the gD will contribute to the understanding of viral pathogenesis and development of alternative vaccines against various diseases associated with BoHV-1. We previously reported the preparation of a monoclonal antibody (MAb) 2B6, which was raised by a truncated recombinant gD protein, demonstrating a neutralizing activity against BoHV-1 infection in Madin–Darby bovine kidney cells. This study described the identification of a linear B-cell epitope on gD using MAb 2B6. A series of partially overlapping gD proteins with glutathione S-transferase tag were generated to define the epitope recognized by MAb 2B6. The amino acid (aa) sequence ³²³GEPKPGPSPDADRPE³³⁷ was recognized by MAb 2B6 using Western blot with the variedly truncated recombinant proteins. Importantly, this epitope was highly conserved among the typical members of BoHV-1, indicating that the epitope may be utilized in diagnosis of diseases due to BoHV-1 infection. Furthermore, the minimal linear epitope sequence ³²³GEPKPGP³²⁹ on gD recognized by MAb 2B6 was confirmed using single-aa residue deletion mutation in carboxyl terminal. This finding not only contributes to our understanding of gD of BoHV-1 virion but also shows a potential for the development of vaccine candidates and diagnostic techniques.