Seroprevalence of Bluetongue Virus in small ruminants in Balochistan province, Pakistan

Prevalence and risk factors of bluetongue in small and large ruminants maintained on Government farms in North-western Pakistan

This study reports prevalence of antibodies against bluetongue virus (BTV) in animals kept on Government farms/research stations in North-western Pakistan and its association with different risk factors. In total, 1257 blood samples were collected, at random, from animals on 12 separate Government farms/research stations. The prevalence of antibodies against BTV was evaluated using a competitive ELISA. Mixed effects univariate and multivariate logistic regressions were applied to ascertain different risk factors associated with the prevalence of the infection using farm as random effect variable. The overall weighted seroprevalence was recorded as 52%. In univariate analysis, a significant association between sero-conversion to BTV infection and species (P < 0.0001), sex (P < 0.0001), herd size (P = 0.0295) and age of animal (P < 0.0001) was recorded. In multivariate mixed effects logistic regression analysis, prevalence of the infection was found to be 7 (95% CI =2-28) times higher in goats and buffalo than in sheep. Prevalence of the infection was found to be 2.5 (95% CI =1.7-3.3) times higher in female than male animals. However, no significant association was found between sero-conversion of BTV and herd size in multivariate mixed effects logistic regression. Age was found to be a risk factor for the sero-conversion; odds of sero-conversion to BTV increased by 1.29, 1.4, 1.32 and 1.6 times per year increase in age of sheep, goats, buffalo and cattle, respectively. Prevalence of bluetongue was found higher in animals maintained on Government owned farms than that in individual holdings, as previously reported in Pakistan.

Epidemiology of bluetongue virus infection among small ruminants in Turkey: Seroprevalence and associated risk factors

Bluetongue (BT) is an endemic disease of small ruminants in Turkey, and it has substantial socio-economic impact at national level. To reduce this impact, vaccination has been used for the control of BT but sporadic outbreaks have been reported. Although sheep and goat farming plays an important role in rural communities, little is known about the BT epidemiological situation in small ruminants in Turkey. Therefore, this study aimed to estimate the seroprevalence of the bluetongue virus (BTV) and to identify the potential risk factors associated with BTV seropositivity in small ruminants. This study was conducted in the Antalya Province in the Mediterranean region of Turkey, from June 2018 to June 2019. A total of 1026 blood samples, from clinically healthy goats (n = 517) and sheep (n = 509), obtained from randomly selected unvaccinated flocks (n = 100) were tested for BTV anti-VP7 antibodies by using a competitive enzyme linked immunosorbent assay test. A questionnaire was administered to the flock owners to obtain data related to sampled flocks and animals. At the animal level, the true prevalence of BTV antibodies was 74.2% (n = 651/1026, 95% CI = 70.7-77.7) with 85.3% (n = 370/509, 95% CI = 80.6-89.9) seropositive sheep and 63.3% (n = 281/517, 95% CI = 58.2-68.4) seropositive goats. The true flock-level seroprevalence of BTV was higher in goats (100.0%, 95% CI = 92.8-100.0) than in sheep (98.8%, 95% CI = 86.6-100.0). The intra-flock seroprevalence within seropositive flocks varied between 36.4% and 100%, with a mean value of 85.5% and 61.9% in sheep and goat flocks, respectively. The logistic regression model revealed that odds of seropositivity for sheep were significantly higher in female animals (OR: 1.8, 95% CI = 1.1-2.9), animals older than 24 months old (OR: 5.8, 95% CI = 3.1-10.8), Pirlak breed (OR: 3.3, 95% CI = 1.1-10.0) and Merino breed (OR: 4.9, 95% CI = 1.6-14.9), whereas for goats, it was higher in female animals (OR: 1.7, 95% CI = 1.0-2.6), animals older than 24 months old (OR: 4.2, 95% CI = 2.7-6.6) and Hair breed (OR: 5.6, 95% CI = 2.8-10.9). The use of insecticides was identified as a protective factor. The present study revealed that BTV infection is widespread in sheep and goats in the Antalya Province. It is recommended to implement biosecurity measures in flocks and use insecticides to mitigate the spread of infection and contact between hosts and vectors.

Serological evidence of bluetongue virus and associated factors in small ruminants of Bangladesh

Bluetongue (BT) is an infectious, vector-borne viral disease of animals having a substantial economic impact and it is endemic in the bordering states of the Indian subcontinent. Livestock enters frequently from India into Bangladesh without any screening. Hence, this study aimed to estimate the seroprevalence of Bluetongue virus (BTV) and associated risk factors in small ruminants of Bangladesh. We conducted a cross-sectional study in the Dhaka, Chattogram, and Faridpur districts of Bangladesh between 2017 and 2018. The team collected 333 serum samples from 123 goats and 210 sheep and tested them for the presence of antibodies against BTV using a competitive enzyme linked immunosorbent assay (c-ELISA). A mixed multivariable logistic regression model was built to identify risk factors. Sample collection location was included as a random effect and husbandry and demographic variables as fixed effects to identify the potential risk factors. The BTV seroprevalence was found to be 55.3% (n = 184; 95% CI: 49.74-60.68). In the mixed-effect logistic regression analysis, animal species (AOR: 4.69; 95% CI: 2.49-8.82; p = 0.001) and vector control measurement (AOR: 9.01; 95% CI: 4.01-20.00; p = 0.0001) were significantly associated with BTV seropositivity. However, no significant association was found in multivariable mixed-effect logistic regression for the variables age, body condition score (BCS), vaccination against PPR (p > 0.05). The study found evidence of high seroprevalence of BTV in both sheep and goats in different districts of Bangladesh, indicating natural exposure of the virus and the animals can serve as a potential threat for other animals. Further research is needed to isolate and identify the circulating virus serotype(s) of BTV in Bangladesh as well as longitudinal studies for epidemiological investigations to formulate sound control programs and to enhance the awareness about the possible impacts of this disease on the livelihood of the people.

Risk-based serological survey of bluetongue and the first evidence of bluetongue virus serotype 26 circulation in Tunisia

BACKGROUND

Bluetongue (BT), a vector-borne disease of wild and domestic ruminants, is responsible for severe economic losses in flocks. To reduce this impact, a surveillance and control plan was implemented in Tunisia. However, the epidemiological situation of BT remains incompletely understood, especially for the circulating serotypes.

OBJECTIVE

The aim of this survey was to determine the seroprevalence, to identify the circulating serotypes and to identify the associated risk factors for bluetongue virus (BTV) circulation in Tunisia using risk-based sampling (RBS).

METHODS

A total of 3314 blood samples were randomly collected from 67 sectors using risk-based sampling and screened by competitive enzyme-linked immunosorbent assays (c-ELISAs). Out of the 1330 positive samples, 200 samples were analysed by serum neutralization test (SNT) to identify circulating BTV serotypes.

RESULTS

Of 3314 sera, 1330 were c-ELISA-positive (40.1%) for antibodies against the BTV structural protein VP7. The result of SNT showed the presence of BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. The logistic regression model revealed that older animals had nearly two times the odds of being infected with BTV compared to younger animals. Flocks with a history of BT were almost 1.5 times more likely to be at risk for contracting BTV infection. The flock size, housing indoors and intensive production system were significant protective factors.

CONCLUSIONS

High seroprevalence of BTV among sheep was highlighted in Tunisia. The neutralization test showed the presence of the following BTV serotypes: BTV-1, BTV-2, BTV-3, BTV-4 and, for the first time in Tunisia, BTV-26. Age, production system and flock size were important variables associated with BTV infection in sheep. This finding is crucial, as it will allow the adjustment of the BT control programme in Tunisia.

Prevalence and risk factors of bluetongue virus infection in sheep and goats in China: A systematic review and meta-analysis

Bluetongue is a viral disease transmitted by the bite of bloodsucking insects, which mainly occurs in sheep, goats, and cattle. Bluetongue is characterized by fever, leukopenia, and severe catarrhal inflammation of the oral and gastrointestinal mucosa. The present study aimed to evaluate and analyze the prevalence of bluetongue and its associated risk factors in sheep and goats in China. We collected 59 publications from 1988 to 2019 through searches at ScienceDirect, PubMed, the Chongqing VIP Chinese journal database, Wanfang database, and Chinese Web of knowledge. In these studies, a total of 123,982 sheep and goats across 7 regions of China were investigated, and the pooled prevalence of bluetongue in sheep and goats was 18.6%, as assessed using serological methods. The prevalence of bluetongue in Southern China was 30.3%, which was significantly higher than that in Northeastern China (4.7%). The prevalence of bluetongue between sheep (12.9%) and goats (28.1%) was significantly different (P < 0.05). Detection methods subgroup analysis showed that the prevalence of bluetongue was significantly higher (P < 0.05) in the others group (43.8%) than in the agar immunodiffusion (15.9%) and enzyme-linked immunosorbent assay groups (20.5%). In addition, different geographical factors (latitude range, longitude range, altitude range, average precipitation, and average temperature) could affect the prevalence. Our results suggested that bluetongue is widespread in sheep and goats, and sheep and goats in contact with insect media, such as Culicoides, or in a warm and humid environment, could have an increased prevalence of bluetongue disease. Animal disease prevention and control departments should focus on continuous monitoring of the bluetongue epidemic in sheep and goats to prevent and control outbreaks.

An updated review on bluetongue virus: epidemiology, pathobiology, and advances in diagnosis and control with special reference to India

Bluetongue (BT) is an economically important, non-contagious viral disease of domestic and wild ruminants. BT is caused by BT virus (BTV) and it belongs to the genus Orbivirus and family Reoviridae. BTV is transmitted by Culicoides midges and causes clinical disease in sheep, white-tailed deer, pronghorn antelope, bighorn sheep, and subclinical manifestation in cattle, goats and camelids. BT is a World Organization for Animal Health (OIE) listed multispecies disease and causes great socio-economic losses. To date, 28 serotypes of BTV have been reported worldwide and 23 serotypes have been reported from India. Transplacental transmission (TPT) and fetal abnormalities in ruminants had been reported with cell culture adopted live-attenuated vaccine strains of BTV. However, emergence of BTV-8 in Europe during 2006, confirmed TPT of wild-type/field strains of BTV. Diagnosis of BT is more important for control of disease and to ensure BTV-free trade of animals and their products. Reverse transcription polymerase chain reaction, agar gel immunodiffusion assay and competitive enzyme-linked immunosorbent assay are found to be sensitive and OIE recommended tests for diagnosis of BTV for international trade. Control measures include mass vaccination (most effective method), serological and entomological surveillance, forming restriction zones and sentinel programs. Major hindrances with control of BT in India are the presence of multiple BTV serotypes, high density of ruminant and vector populations. A pentavalent inactivated, adjuvanted vaccine is administered currently in India to control BT. Recombinant vaccines with DIVA strategies are urgently needed to combat this disease. This review is the first to summarise the seroprevalence of BTV in India for 40 years, economic impact and pathobiology.

Soluble expression and purification of Bluetongue Virus Type 1 (BTV1) structure protein VP2 in Escherichia coli and its immunogenicity in mice

Background

The VP2 on the surface of the virus particle is the main structural protein of BTV, which can induce the host to produce neutralizing antibodies and play an important role in the antiviral immunity process. This study aimed to obtain the soluble VP2 and analyze its immunogenicity.

Methods

The gene encoding the full-length VP2 of BTV1 was amplified by PCR. The products from restriction enzyme digestion and ligase reaction between VP2 and vector pET-28a were transformed into E.coli DH5α. After PCR and sequencing detection, the positive plasmid PET28a-VP2 was transformed into E.coli BL21(DE3) and Rosetta(DE3) competent cells, expression induced by IPTG. The fusion protein was expressed in the optimized conditions with the induction of IPTG, purified by affinity chromatography and identified by SDS-PAGE and Western blotting. A total of 5 Balb/c mice aged 6–8 weeks were immunized with the fusion protein at a dose of 30 µg per mouse. Each mouse was immunized three times at an interval of 3 weeks.

Results

The recombinant plasmid PET28a-VP2 was successfully constructed. The expression strains were induced by 0.4 mmol/L IPTG at 16 °C for 10 h, and BTV1 VP2 was expressed in a soluble form. The purity of the recombinant VP2 protein (∼109 kDa) was about 90% in the concentration at 0.2 mg/ml afterpurification. The purified VP2 had good immunoreactivity with BTV1 positive serum. Taken together, thisstudy offered a route for producing soluble BTV VP2, which retains activity and immunogenicity, to bebeneficial to the research on developing BTV vaccine, and lay the foundation for further research on BTV.

Seroprevalence and Risk Factors of the Bluetongue Virus in Cattle in China From 1988 to 2019: A Comprehensive Literature Review and Meta-Analysis

Background: Bluetongue caused by the bluetongue virus (BTV) is a non-contagious and an insect-borne disease mainly affecting domestic and wild ruminants. Bluetongue in cattle is associated with vesicular lesions, weight loss, low milk production, and low reproductive capacity. It should not be ignored as it is associated with large economic losses to the livestock breeding industry in China. Although many studies have investigated bluetongue virus infection in cattle, no nationwide study on the prevalence of bluetongue virus infection in cattle from China has yet been conducted. This meta-analysis aimed to evaluate the seroprevalence and risk factors for bluetongue in cattle. Results: We collected 50 publications from 1988 to 2019 through PubMed, ScienceDirect, Chinese Web of Knowledge (CNKI), VIP Chinese journal database, and Wanfang database. A total of the pooled bluetongue seroprevalence of 12.2% (5,332/87,472) in cattle was tested. The point estimate of bluetongue collected from 2001 to 2011 was 22.5% (95% CI: 1.2-58.9), which was higher than after 2012 (9.9%, 95% CI: 3.3-19.4). The analysis of the feeding model subgroup revealed that the seroprevalence of bluetongue was significantly higher (P < 0.05) among free-range cattle (22.5%; 95% CI: 7.7-42.3) than among cattle from intensive farming systems (1.8%; 95% CI: 0.0-6.7). The seroprevalence of bluetongue in different species showed significant variation (P < 0.05), with the highest seroprevalence of 39.8% (95% CI: 18.7-63.0) in buffalo and the lowest seroprevalence of 4.3% (95% CI: 1.2-9.0) in yak. In the zoogeographical division subgroup, the seroprevalence of bluetongue correlated positively within a certain range with the species distribution of Culicoides. Conclusion: Our findings suggested that bluetongue was prevalent in cattle in China. In addition, the contact with sheep, other ruminants, or transmission media such as Culicoides may increase the seroprevalence of bluetongue disease in cattle. It is necessary to carry out continuous monitoring of the bluetongue seroprevalence. Moreover, comprehensive and improved strategies and measures should be implemented to prevent and control the spread of bluetongue.

Sentinel surveillance of selected veterinary and public health pathogens in camel population originating from Southern Punjab province, Pakistan

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Camels are susceptible to a wide range of infectious diseases with varying rate of morbidity and mortality.

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Blutongue, peste des petits ruminants and brucellosis are prevalent among camels in southern part of the Punjab provinvce, Pakistan.

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Genome corresponding to Brucella abortus and multiple serotypes of bluetongue were detected among camels.

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Camels should be included for disease control interventions reltaed to brucellosis, blutongue and PPR from their endemic setting worldwide.

An extended range of host susceptibility including camel has been evidenced for some of the important veterinary and public health pathogens, such as brucellosis, peste des petits ruminants (PPR) and bluetongue (BT). However, in disease endemic settings across many parts of the globe, most of the disease control interventions accounts for small and large ruminants, whereas unusual hosts and/or natural reservoirs, such as camels, remain neglected for disease control measures including routine vaccination. Such a policy drawback not only plays an important role in disease epizootiology particularly in settings where disease is endemic, but also serves an obstacle in disease control and subsequent eradication in future. With this background, using pre-validated ELISA and molecular assays [multiplex PCR, reverse transcriptase (RT)-PCR and real-time (rt)-PCR], we conducted a large-scale pathogen- and antibody-based surveillance for brucellosis, peste des petits ruminants and bluetongue in camel population (n = 992) originating from a wide geographical region in southern part of the Punjab province, Pakistan. Varying in each of the selected districts, the seroprevalence was found to be maximum for bluetongue [n = 697 (70.26%, 95% CI: 67.29–73.07)], followed by PPR [n = 193 (19.46%, 95% CI: 17.07–22.09)] and brucellosis [n = 66 (6.65%, 95% CI: 5.22–8.43)]. Odds of seroprevalence were more significantly associated with pregnancy status (non-pregnant, OR = 2.23, 95% CI: 1.86–5.63, p<0.01), farming system (mixed-animal, OR = 2.59, 95% CI: 1.56–4.29, p<0.01), breed (Desi, OR = 1.97, 95% CI: 1.28–4.03, p<0.01) and farmer education (illiterate, OR = 3.17, 95% CI: 1.45–6.93, p<0.01) for BTV, body condition (normal, OR = 3.54, 95% CI: 1.92–6.54, p<0.01) and breed (Desi, OR = 2.19, 95% CI: 1.09–4.40, p<0.01) for brucellosis, and feeding system for PPR (grazing, OR = 2.75, 95% CI: 1.79–4.22, p<0.01). Among the total herds included (n = 74), genome corresponding to BT virus (BTV) and brucellosis was detected in 14 (18.92%, 95 CI: 11.09–30.04) and 19 herds (25.68%, 95% CI: 16.54–37.38), respectively. None of the herds was detected with genome of PPR virus (PPRV). Among the positive herds, serotype 1, 8 and 11 were detected for BTV while all the herds were exclusively positive to B. abortus. Taken together, the study highlights the role of potential disease reservoirs in the persistence and transmission of selected diseases in their susceptible hosts and, therefore, urges necessary interventions (e.g., inclusion of camels for vaccine etc.) for the control of diseases from their endemic setting worldwide.

Large-scale seroprevalence and risk factors associated with Bluetongue virus in Iran

Bluetongue virus (BTV) remains as an economically major concern in the world. Seroprevalence and potential risk factors of BTV were assessed in a cross-sectional study at both the herd and animal levels in Iran. A total of 73 Epidemiologic Units (E.Unit), defined as a herd, flock or village including animals with equal chance of exposure to infectious agents, were randomly selected. Serum samples from all animals (n = 34,575) within the E.Units were collected and tested for BTV sero-group antibodies by using commercially competitive ELISA test. Using cluster analysis, 90.41 % (95 %, CI: 80.85 %-95.47 %) of the E.Units and 56.13 % (95 % CI: 55.61 %-56.66 %) of the tested animals were detected seropositive against BTV. A seroprevalence rate of 57.59 % (95 % CI: 48.01 %-66.63 %), 65.65 % (95 % CI: 59.10 %-73.74 %) and 27.63 % (95 % CI: 14.40 %-46.43 %) was estimated for sheep, goats and cattle, respectively. At E.Unit (herd) level, density was identified as a great risk factor for the infection (r² = 0.891; P = 0.000), and particularly density of cattle significantly correlated with BTV infection within the E.Units (r² = 0.247; P = 0.019). Using multilevel logistic regression, adjusted odds ratios (ORs) were estimated at individual level. A significantly less risk of BTV infection was evaluated for cattle than for sheep (OR = 0.42, 95 % CI: 0.38-0.47, P < 0.001), while no significant difference was observed between sheep and goat (OR = 1.03, 95 % CI: 0.97-1.10, P = 0.345). Animals over 2 years and between 6 months and 2 years expressed 2.22 (OR = 2.22, 95 % CI: 1.96-2.52, P < 0.001) and 2.18 (OR = 2.18, 95 % CI: 1.92-2.49, P < 0.001) times higher chance for the infection than animals under 6 months. Males were at significantly less risk of the infection than females (OR=0.68, 95 % CI: 0.63-0.74, P < 0.001). Animals kept in industrial farming systems displayed 0.46 (OR=0.46, 95 % CI: 032-0.66, P < 0.001) times less chance than animals kept in traditional farming system for BTV, while animals lived in semi-industrial farming system were found to be at 2.97 (OR=2.97, 95 % CI: 2.41-3.66, P < 0.001) times higher chance for BTV than animals lived in traditional farming system. Furthermore, seropositive animals exhibited a high amount of antibodies against BTV (s) suggesting that viral exposure may have frequently occurred during their lifetimes. This large - scale study yielded information on epidemiology of BTV in Iran that is prerequisite for further research, and also for evaluation of any cost-benefit control measure to be established in an enzootic zone of the virus.

Seroprevalence of Bluetongue virus in small and large ruminants in Punjab province, Pakistan

Bluetongue (BT) is a vector-borne disease of immense economic importance for small and large ruminants. Despite frequent disease reports from neighboring countries, a little is known about current disease status and prevalent serotypes in Pakistan. We screened a total of 1312 healthy animals for group-specific antibodies and serotype-specific genome for BT virus through competitive ELISA and real-time PCR, respectively. An overall prevalence of group-specific VP7 antibodies [28.81% (n = 378/1312, 95% CI = 26.4-31.4)] was observed. The prevalence was higher in goats [40.75% (n = 194/476, 95% CI = 36.4-45.3)] followed by buffalo [29.34% (n = 81/276, 95% CI = 24.3-34.9)], sheep [18.40% (n = 60/326, 95% CI = 14.5-22.9)] and cattle [17.94% (n = 42/234, 95% CI = 13.56-23.4)]. The odds of seropositivity were more in buffalo of Nili breed (OR = 2.06, 95% CI = 1.19-3.58) as well as those found with a presence of vector (OR = 2.04, 95% CI = 1.16-3.59). Buffalo and cattle with history of abortion [(OR = 3.95, 95% CI = 1.33-11.69) and (OR = 5.89, 95% CI = 1.80-19.27) respectively] were much likely to be infected with the disease. Serotype 8 was detected in all animal species while, serotypes 4 and 6 were detected in sheep, 2, 6 and 11 in goat, and 2 and 16 in buffalo. The study concludes a much frequent exposure of different serotypes of Bluetongue virus (BTV) in small and large ruminants and indicates its expansion to enzootic range worldwide.