Sero-epidemiology of bluetongue virus (BTV) infection in sheep and goats of Khyber Pakhtunkhwa province of 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.

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.

Seroprevalence and risk factors of bluetongue virus in sheep of Chattogram, Bangladesh

Background and Aim:

Bluetongue (BT) is a non-contagious, infectious disease of wild and domestic ruminant animals caused by the BT virus (BTV). Bangladesh having a border with a BTV-endemic country, India and a substantial number of susceptible animals. Therefore, this study aimed to estimate BTV seroprevalence and potential risk factors.

Materials and Methods:

We collected 150 serum samples from indigenous sheep from Chattogram, Bangladesh. We screened the serum samples using a competitive enzyme-linked immunosorbent assay for detecting BTV-specific immunoglobulin.

Results:

We detected antibodies against BTV in 39.3% (59/150; 95% confidence interval: 31.5–47.6) of all sampled sheep. Factors like sampling site, sheep rearing location, rearing sheep with other farm species, and body condition score had a significant (p < 0.05) influence on the seroprevalence of BTV.

Conclusion:

The findings show that indigenous sheep have a higher BTV seroprevalence, necessitating sustained surveillance for early diagnosis and a better understanding of virus epidemiology in Bangladesh.

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.

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.