Large-scale Serological Survey Research Articles

A Large-Scale Serological Survey in Pets From October 2020 Through June 2021 in France Shows Significantly Higher Exposure to SARS-CoV-2 in Cats Compared to Dogs.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to infect various animals, including domestic pets like dogs and cats. Many studies have documented infection in companion animals by molecular and serological methods. However, only a few have compared seroprevalence in cats and dogs from the general population, and these studies were limited by small sample sizes and collections over short periods. Our aim was to obtain a more accurate evaluation of seroprevalence in companion animals in France and to determine whether cats and dogs differ in their exposure to SARS-CoV-2. We conducted an extensive serological survey of SARS-CoV-2, collecting blood samples from 2036 cats and 3577 dogs during routine veterinary medical examinations across different regions of metropolitan France from October 2020 to June 2021. This period encompassed the peaks and onset of two waves, as well as the emergence of the first variants. A microsphere immunoassay targeting the receptor-binding domain and trimeric spike protein was used to detect anti-SARS-CoV-2 antibodies. A subset of 308 seropositive samples was tested for the presence of neutralising antibodies. We determined an overall seroprevalence of anti-SARS-CoV-2 antibodies of 7.1% (95% confidence interval [CI]: 6.4%-7.8%) among the sampled pets. Cats exhibited a significantly higher seroprevalence (9.3%; 95% CI: 8.1%-10.1%) compared to dogs (5.9%; 95% CI: 5.2%-6.8%). Among the subset of seropositive samples, 81 (26.3%; 95% CI: 21.5%-31.6%) displayed neutralizing antibodies. Furthermore, seroprevalence in both species was lower in older animals and was not associated with sex. Finally, unlike cats, seroprevalence in dogs was found to be correlated with the date of sampling. The large sample size enhances the reliability and statistical robustness of our estimates regarding pet exposure to SARS-CoV-2. This study on SARS-CoV-2 reaffirms the crucial importance of adopting a One Health approach incorporating domestic animals when managing an epidemic caused by a zoonotic virus.

Evaluation of dried blood spots for serological surveys of myxoma and rabbit hemorrhagic disease viruses in their wild reservoir

Myxoma (MYXV) and rabbit hemorrhagic disease (RHDV) viruses are pathogens of economic relevance for cuniculture and conservation concern for wild European rabbits (Oryctolagus cuniculus), recently classified as ‘Endangered’ in its native range. Large-scale serological surveys, facilitated by sample collection using dried blood spots (DBS), allow monitoring seroprevalence in the wild reservoir but require evaluating the technique for the host and pathogen of interest. This study aimed to evaluate Protein Saver 903 DBS for MYXV and RHDV (genotype GI.2) serological surveys in European rabbits. Paired serum and DBS collected from 172 rabbits harvested or found dead in the Iberian Peninsula were tested for IgG antibodies specific against MYXV and RHDV GI.2 using indirect ELISA. We found an almost perfect agreement between serum and DBS for MYXV (Cohen's κ=0.914, CI95 0.847 – 0.981) and a strong agreement for RHDV GI.2 (Cohen's κ=0.808, CI95=0.722 – 0.893). The diagnostic sensitivity of DBS was 95.4 % (CI95 90.3 – 97.9 %) for MYXV and 82.1 % (CI95 73.2 – 88.5 %) for RHDV GI.2. The diagnostic specificity and positive predictive value were 100 % for both pathogens. This study supports DBS as a suitable sampling strategy for serological surveys of antibodies specific to MYXV and RHDV GI.2 in European rabbits, which generally agrees with results from other hosts and pathogens where this technique was evaluated.

Molecular epidemiology and population immunity of SARS-CoV-2 in Guangdong (2022–2023) following a pivotal shift in the pandemic

The SARS-CoV-2 Omicron variant sparked the largest wave of infections worldwide. Mainland China eased its strict COVID-19 measures in late 2022 and experienced two nationwide Omicron waves in 2023. Here, we investigated lineage distribution and virus evolution in Guangdong, China, 2022-2023 by comparing 5813 local viral genomes with the datasets from other regions of China and worldwide. Additionally, we conducted three large-scale serological surveys involving 1696 participants to measure their immune response to the BA.5 and XBB.1.9 before and after the corresponding waves. Our findings revealed the Omicron variants, mainly the BA.5.2.48 lineage, causing infections in over 90% of individuals across different age groups within a month. This rapid spread led to the establishment of widespread immunity, limiting the virus’s ability to further adaptive mutation and dissemination. While similar immune responses to BA.5 were observed across all age groups after the initial wave, children aged 3 to 11 developed a stronger cross immune response to the XBB.1.9 strain, possibly explaining their lower infection rates in the following XBB.1 wave. Reinfection with Omicron XBB.1 variant triggered a more potent neutralizing immune response among older adults. These findings highlight the impact of age-specific immune responses on viral spread in potential future waves.

Large-Scale Serological Survey of Crimean-Congo Hemorrhagic Fever Virus and Rift Valley Fever Virus in Small Ruminants in Senegal.

Crimean-Congo hemorrhagic fever (CCHF) and Rift Valley fever (RVF) are among the list of emerging zoonotic diseases that require special attention and priority. RVF is one of the six priority diseases selected by the Senegalese government. Repeated epidemic episodes and sporadic cases of CCHF and RVF in Senegal motivated this study, involving a national cross-sectional serological survey to assess the distribution of the two diseases in this country throughout the small ruminant population. A total of 2127 sera from small ruminants (goat and sheep) were collected in all regions of Senegal. The overall seroprevalence of CCHF and RVF was 14.1% (IC 95%: 12.5-15.5) and 4.4% (95% CI: 3.5-5.3), respectively. The regions of Saint-Louis (38.4%; 95% CI: 30.4-46.2), Kolda (28.3%; 95% CI: 20.9-35.7), Tambacounda (22.2%; 95% CI: 15.8-28.6) and Kédougou (20.9%; 95% CI: 14.4-27.4) were the most affected areas. The risk factors identified during this study show that the age, species and sex of the animals are key factors in determining exposure to these two viruses. This study confirms the active circulation of CCHF in Senegal and provides important and consistent data that can be used to improve the surveillance strategy of a two-in-one health approach to zoonoses.

Large-scale serological survey on Mycobacterium avium subsp. paratuberculosis infection in sheep and goat herds in Sicily, Southern Italy.

Paratuberculosis (PTB) is a worldwide chronic, contagious enteric disease caused by Mycobacterium avium subsp. paratuberculosis (MAP) mainly affecting ruminant species. PTB is a WOAH-listed disease with direct and indirect economic losses in the livestock sector, negative impact on animal welfare and significant public health concerns. In spite of this, MAP prevalence in small ruminants is still unknown and the prevalence appears to be underestimated in many countries. The aim of this study is providing a first large-scale serological survey on MAP infection in small ruminants in Sicily, a region of Southern Italy with the 11.3 and 8.9% Italian national heritage of sheep and goats, respectively. For this purpose, we analyzed a total of 48,643 animals reared in 439 flocks throughout Sicily. MAP seroprevalence was estimated both at herd-level and animal-level within breeds reared in all the nine sampled provinces. Our results revealed a high overall apparent prevalence at herd-level of 71.8% in sheep and 60.8% in goat farms with an animal-level prevalence of 4.5 and 5.1% in sheep and goats, respectively. Significant statistical differences were found between the provinces and within the breeds both in sheep and goats. Our study provides the first large-scale serological survey on PTB infection in small ruminants in Sicily and showed a high prevalence of disease depending to the species, breed and province. This study represents the first step to better understand the MAP epidemiology in a typical Mediterranean breeding context, suggesting the need of in-depth study on the herds risk factors, including the eventual presence of candidate genes for resistance/susceptibility to PTB in native breeds.

Development and Application of an iELISA for the Detection of Antibody against Salmonella Abortusequi

Equine abortus salmonellosis is a bacterial disease that causes high abortion rates in susceptible equids and therefore significant economic losses. Although the tube agglutination test (TAT) is a commonly used serological test for S. Abortusequi, it is not highly specific or sensitive, and the development of more sensitive, specific and rapid assays is therefore urgently required. In this study, an indirect enzyme-linked immunosorbent assay (iELISA) was developed for the specific detection of flagellum protein (FljB) antibodies against S. Abortusequi. Negative sera from horses in China (n = 1030) were used to establish the baseline for a negative population, and reference antisera positive against other viruses or bacteria were used to test the cross reactivity of the technique. The performance of the FljB iELISA was evaluated against that of the standard TAT, and was tested using field serum samples. The FljB iELISA assay was 8–16 times more sensitive than TAT. ROC analysis showed that the FljB iELISA was accurate, with an area under the curve (AUC) = 0.9943 (95% CI, 0.9815–1.000). The diagnostic sensitivity (DSe) of the FljB iELISA was 98.9% (95% Cl, 93.84%–100.00%), which was higher than that of TAT (DSe 38.6; 95% CI, 29.14%–49.08%). The diagnostic specificity (DSp) of the iELISA was 100.0% (95% CI, 95.82%–100.0%). When the 508 clinical samples were tested, the FljB iELISA had a positive detection rate of 51.38% (261/508, 95% CI, 51.24%–51.51%), which was higher than that of TAT (44/508). We also performed a serological survey for S. Abortusequi infection, using a series of samples collected from across eighteen provinces of China in 2021. The results showed that all provinces except Jiangsu had a certain number of cases, and the positive rates ranged from 0% to 96.9%, indicating the wide spread of S. Abortusequi in China. The abovementioned results suggest that the FljB iELISA developed in this study is rapid, sensitive, specific, and repeatable and is likely to be a suitable test for large-scale serological surveys for the detection and control of S. Abortusequi infection.

Relative role of border restrictions, case finding and contact tracing in controlling SARS-CoV-2 in the presence of undetected transmission: a mathematical modelling study

BackgroundUnderstanding the overall effectiveness of non-pharmaceutical interventions to control the COVID-19 pandemic and reduce the burden of disease is crucial for future pandemic planning. However, quantifying the effectiveness of specific control measures and the extent of missed infections, in the absence of early large-scale serological surveys or random community testing, has remained challenging.MethodsCombining data on notified local COVID-19 cases with known and unknown sources of infections in Singapore with a branching process model, we reconstructed the incidence of missed infections during the early phase of the wild-type SARS-CoV-2 and Delta variant transmission. We then estimated the relative effectiveness of border control measures, case finding and contact tracing when there was no or low vaccine coverage in the population. We compared the risk of ICU admission and death between the wild-type SARS-CoV-2 and the Delta variant in notified cases and all infections.ResultsWe estimated strict border control measures were associated with 0.2 (95% credible intervals, CrI 0.04–0.8) missed imported infections per notified case between July and December 2020, a decline from around 1 missed imported infection per notified case in the early phases of the pandemic. Contact tracing was estimated to identify 78% (95% CrI 62–93%) of the secondary infections generated by notified cases before the partial lockdown in Apr 2020, but this declined to 63% (95% CrI 56–71%) during the lockdown and rebounded to 78% (95% CrI 58–94%) during reopening in Jul 2020. The contribution of contact tracing towards overall outbreak control also hinges on ability to find cases with unknown sources of infection: 42% (95% CrI 12–84%) of such cases were found prior to the lockdown; 10% (95% CrI 7–15%) during the lockdown; 47% (95% CrI 17–85%) during reopening, due to increased testing capacity and health-seeking behaviour. We estimated around 63% (95% CrI 49–78%) of the wild-type SARS-CoV-2 infections were undetected during 2020 and around 70% (95% CrI 49–91%) for the Delta variant in 2021.ConclusionsCombining models with case linkage data enables evaluation of the effectiveness of different components of outbreak control measures, and provides more reliable situational awareness when some cases are missed. Using such approaches for early identification of the weakest link in containment efforts could help policy makers to better redirect limited resources to strengthen outbreak control.

A Randomized Large-Scale Cross-Sectional Serological Survey of Hepatitis E Virus Infection in Belgian Pig Farms.

Hepatitis E virus (HEV) is the causative agent of hepatitis E disease in humans. While sporadic HEV infections, which occur in industrialised countries and are typically due to HEV genotypes 3 or 4, are asymptomatic and self-limiting, a chronic form of the disease can lead to liver cirrhosis in immunocompromised individuals. Pigs share HEV 3 and 4 genotypes and are thus considered a major animal reservoir for human infection. A subset of animals has been shown to carry HEV particles at the age of slaughter, rendering raw or undercooked pig products potential vectors for human infection. To provide an overview of the current dissemination of HEV in Belgian pig herds, this study was designed as a randomized, robust, large-scale, cross-sectional, serological survey. HEV genotypes and subtypes recently circulating in Belgium (2020-2021) were investigated. Sample stratification as well as epidemiological investigation through the available demographic data of the sampled herds showed that HEV widely circulated in the Belgian pig population during this time and that a change in the circulating HEV strains may have occurred in the last decade. Herd size and type were identified as risk factors for HEV herd-seropositivity. Identifying farms at risk of being HEV-positive is an important step in controlling HEV spread and human infection.

Measuring Resilience and Fatality Rate During the First Wave of COVID-19 Pandemic in Northern Italy: A Note.

Background: This Policy Brief aims to contribute to the debate on the resilience of the healthcare systems during the pandemic by discussing whether mortality indicators are appropriate for assessing resilience or whether other statistics should be employed. Evidence: During the first wave of the COVID-19, much emphasis was placed on case-fatality rates to offer a preliminary assessment of the resilience of healthcare systems. However, these statistics are often biased and do not consider the real figure of the population that has been infected. Policy Options and Recommendations: Comparing data obtained with different approaches based on statistical inference and large-scale serological survey, the brief highlights, that great care must be taken when using case-fatality data, which in the absence of careful analysis, can lead to erroneous conclusions. Conclusion: Using case-fatality rate gives us no sounding information about the real capability of healthcare systems to save lives during the pandemic. However, even in the absence of detailed epidemiological data new advancements in statistical methods can be useful to provide a more sounding evaluation of the resilience of the healthcare systems.

Development of an indirect enzyme-linked immunosorbent assay for the detection of novel chicken orthoreovirus.

A novel avian orthoreovirus (N-ARV) variant characterized with obvious arthritis and synovial inflammation, was isolated from Shandong, China in May 2016. It caused chicken poor growth and enormous economic losses to the poultry industry of China. However, there are few effective methods for detecting the antibody levels of N-ARV. In this study, a viral structural protein σC was expressed using the prokaryotic expression vector pET32a (+). The target protein was obtained by inducing for 6 hours at an IPTG concentration of 0.6mM. The optimal dilution of the coating antigen and serum antibody were determined to be 1000 fold and 10 fold respectively. A specificity test showed that there was no positive reactivity between N-ARV and other pathogens, and when the positive serum was diluted 100 times detection results were still checkable. The repeatability of this method was determined by the inter assay and intra assay tests with variability ranging from 4.85% to 7.93%. In conclusion, this indirect enzyme linked immunosorbent assay (ELISA) will be useful for large-scale serological surveys and monitoring antibody levels in N-ARV infection.

Serological survey of antibodies against SARS-CoV-2 in dogs and cats, Thailand.

Coronavirus disease of 2019 (COVID‐19) caused by severe acute respiratory syndrome virus type 2 (SARS‐CoV‐2) is an emerging severe acute respiratory disease affecting global human health. In this study, a large‐scale serological survey of antibodies against SARS‐CoV‐2 in dogs and cats was conducted during the first and second waves of COVID‐19 outbreaks in Thailand, from April to December 2020. A total of 3215 serum samples were collected from dogs (n = 2102) and cats (n = 1113) living in Bangkok and in the vicinities. Serum samples were tested for SARS‐CoV‐2 antibodies by using an indirect multispecies enzyme‐linked immunosorbent assay (ELISA). Positive and suspected samples were additionally tested for neutralizing antibodies by the surrogate virus neutralization test (sVNT). The indirect ELISA results showed that 1.66% (35 out of 2103) of dogs and 0.36% (four out of 1112) of cats were positive for SARS‐CoV‐2 antibodies. The sVNT results showed that all ELISA‐positive and suspected samples were negative for neutralizing antibodies. Positive serum samples (35 dogs and four cats) were obtained from clinically healthy animals and animals with mild respiratory signs aged <1–13 years living in Bangkok and Samutprakarn Provinces. In summary, a serological survey revealed evidence of anti‐N‐IgG antibodies suggesting SARS‐CoV‐2 exposure in both dogs and cats during the first and second COVID‐19 outbreaks in Thailand.

Measuring Resilience and Fatality Rate During the First Wave of COVID-19 Pandemic in Northern Italy: A Note for Robust Health Policy Assessment

Background: During the first wave of the COVID-19 pandemic, much emphasis was placed on mortality indicators such as case-fatality rate and crude mortality rates to offer a preliminary assessment of the resilience between healthcare systems. The paper aims to contribute to the debate on the resilience of the healthcare systems during the pandemic by discussing whether the case-fatality rate and crude mortality indicators are appropriate for assessing resilience or whether other indicators should be employed.Method and Results: Comparing data obtained with different approaches based on statistical inference and large-scale serological survey, the article highlight, that great care must be taken when using case-fatality and crude mortality data, which in the absence of careful analysis, can lead to erroneous conclusions on the assessment of the resilience between healthcare systems. Furthermore, it shows that even in the absence of detailed epidemiological data new advancement in statistical methods can be useful to provide a more sounding evaluation of resilience.Funding Statement: None to declare. Declaration of Interests: The author declares no competing interests.

SARS-CoV-2 neutralising antibodies in dogs and cats in the United Kingdom

Companion animals are susceptible to SARS-CoV-2 infection and sporadic cases of pet infections have occurred in the United Kingdom. Here we present the first large-scale serological survey of SARS-CoV-2 neutralising antibodies in dogs and cats in the UK. Results are reported for 688 sera (454 canine, 234 feline) collected by a large veterinary diagnostic laboratory for routine haematology during three time periods; pre-COVID-19 (January 2020), during the first wave of UK human infections (April–May 2020) and during the second wave of UK human infections (September 2020–February 2021). Both pre-COVID-19 sera and those from the first wave tested negative. However, in sera collected during the second wave, 1.4% (n ​= ​4) of dogs and 2.2% (n ​= ​2) of cats tested positive for neutralising antibodies. The low numbers of animals testing positive suggests pet animals are unlikely to be a major reservoir for human infection in the UK. However, continued surveillance of in-contact susceptible animals should be performed as part of ongoing population health surveillance initiatives.

On the importance of population-based serological surveys of SARS-CoV-2 without overlooking their inherent uncertainties

The SARS-CoV-2 epidemic has caused an unprecedented public health situation and more than ever it is important to be well informed on methods to monitor and analyse the progression of the epidemic. This brief note aims to explain the scope in conducting large-scale serological surveys of SARS-CoV-2 to define the landscape of population immunity, without overlooking the inherent uncertainty steaming from sampling design and diagnostic validity. The note completes with a succinct appendix of simple statistical methods for estimating prevalence from random population samples using imperfect diagnostic tests.

Seroprevalence and Potential Risk Factors of Bluetongue Virus Infection in Domestic Cattle and Goats in Guangxi Province, Southern China.

Bluetongue is one of the most important vector-borne viral diseases that can lead to significant economic losses as a result of reduction of productivity and even death in some susceptible ruminants. However, epidemiological information on bluetongue virus (BTV) infection in cattle and goats is scarce in China. To determine the seropositive rate and risk factors of BTV infection in cattle and goats in Guangxi province, a subtropical region in Southern China, a total of 548 cattle serum samples and 6567 goat serum samples collected from 13 cities across Guangxi province during 2003-2015 were analyzed and found that the seroprevalence is 44.5% (244/548) in cattle and 28.0% (1837/6567) in goats and the main BTV serotypes are BTV-1, -2, -4, and -8. Climatic zone, age, and species are found to be the likely risk factors for BTV infection. To our knowledge, this is the first large-scale serological survey for BTV infection in domestic cattle and goats in Guangxi province, Southern China.

Characterization of the self-assembly of New Jersey polyomavirus VP1 into virus-like particles and the virus seroprevalence in Japan

New Jersey polyomavirus (NJPyV) was discovered in 2014 in a pancreatic transplant recipient’s vascular endothelial cells. Here, in the recombinant baculovirus system, VP1 protein of NJPyV expressed in insect cells was processed. The protein self-assembled into virus-like particles (NJPyV-LPs) in a cell-type-dependent manner, and the particles were then released into the culture media. Spherical ~50-nm-dia. NJPyV-LPs of uniform size with morphology resembling that of the native particles of polyomaviruses were purified from the fraction at 1.33 g/cm3 in supernatants of VP1-expressing Sf9 cells. We investigated the antigenic properties of purified NJPyV-LPs and performed a VLP-based enzyme immunoassay to determine the age-specific prevalence of NJPyV infection in a general Japanese population aged 1–70 years. The overall seropositivity rate of anti-NJPyV antibodies was only 1.8%. This might be explained by the low circulation of NJPyV in Japan. This is the first report of a large-scale serological survey of NJPyV in Asia (n = 1,050).

Serological survey and risk factors of Aelurostrongylus abstrusus infection among owned cats in Italy.

Feline lungworms affect the respiratory tract of domestic cats causing respiratory conditions of various degrees. In this study, we investigated the exposure of cats to feline lungworm infections by detecting antibodies in a large population of animals from several regions of Italy. Sera of 1087 domestic cats living in regions of the north (n = 700), the centre (n = 227) and the south (n = 160) of Italy were examined by a newly developed indirect ELISA conceived for detection of antibodies against the most frequently occurring feline lungworm Aelurostrongylus abstrusus. Individual cat data (i.e., age, sex, neutering status and provenience) were analysed as potential risk factors for exposure to lungworm infections. Samples were additionally screened for feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) proviral DNAs. Overall, 9% (98/1087; 95% confidence interval (CI) 7.4-10.9%) of the animals tested seropositive to lungworm antibodies. Positive cats were identified in the north (7.1%; CI 5.5-9.3%), in the centre (5.3%; CI 3.0-9.0%) and in the South (22.5%; CI 16.7-29.6%), with more seropositive animals in the latter area (p < 0.05). The risk of lungworm infection in cats was significantly associated with age less than 6months (i.e. 24.4%, p < 0.05) and FIV infection (p < 0.05). This large-scale serological survey confirms the exposure of cats to lungworm infections in Italy and that serological tests can be used to assess the distribution of lungworm infections in large populations of animals.

A Large-Scale Serological Survey of Toxoplasma gondii Infection Among Persons Participated in Health Screening in Yunnan Province, Southwestern China.

Surveys of Toxoplasma gondii infection in animals have been reported in Yunnan province, southwestern China. However, limited information is available regarding the epidemiology of T. gondii infection among persons participated in health screening in Yunnan. From January 2014 to December 2016, a large-scale and cross-sectional serological survey was conducted to reveal the seroprevalence of T. gondii infection in persons participated in health screening in three major hospitals. A total of 64,533 serum samples were collected and anti-T. gondii antibodies were examined by commercially available enzyme-linked immunosorbent assay kits. The total seroprevalence of T. gondii infection was 6.67% (4306/64,533). Of these, 3721 persons (5.77%, 3721/64,533) were positive for Immunoglobulin G (IgG) only, 473 persons (0.73%, 473/64,533) were positive for Immunoglobulin M (IgM) only, and 112 persons (0.17%, 112/64,533) were positive for both IgG and IgM. Female seroprevalence (6.83%, 3167/46,389) was higher than male (6.28%, 1139/18,144). The highest seroprevalence of T. gondii infection was found in the age range of 41-50 years (10.60%, 228/2150) (p < 0.001). The seroprevalence in 2014, 2015, and 2016 were 6.39% (1083/16,946), 6.24% (1261/20,201), and 7.16% (1962/27,386), respectively. The results showed that T. gondii infection is common in persons participated in health screening in Yunnan province, which has significant public health concern. Thus, improved integrated measures should be executed to prevent and control T. gondii infection humans and animals in Yunnan province.

Development and application of an indirect ELISA for the detection of antibodies against encephalomyocarditis virus.

Encephalomyocarditis virus (EMCV) can cause acute myocarditis in young pigs or reproductive failure in sows. It has been recognized worldwide as a pathogen infecting many species and causes substantial economic losses. In the present study, an indirect ELISA was developed for the detection of antibodies to EMCV. The VP1 gene of EMCV was amplified by reverse transcription-quantitative polymerase chain reaction and expressed in Escherichia coli with 49.3 kDa under the condition of isopropyl-β-d-thiogalactoside. Following this, the authors obtained the recombinant protein VP1 as a coating antigen. The antigen concentration and serum dilution were optimized using a checkerboard titration. Compared with viral neutralization tests, the sensitivity and specificity of the indirect ELISA was 95.7% and 92.9%, respectively. A total of 265 clinical swine serum samples from different pig farms in China were used to a serological survey. The seropositive rate of the serum samples was 81.9%. In conclusion, the developed indirect ELISA assay is sensitive and specific, which will be useful for large-scale serological survey in EMCV infection and monitoring antibodies titers against EMCV.

A large-scale serological survey of Akabane virus infection in cattle, yak, sheep and goats in China

Akabane virus (AKAV) is a member of the Simbu serogroup, classified in the genus Orthobunyavirus, family Bunyaviridae. AKAV infection can cause abortion, stillbirth, and congenital arthrogryposis and hydranencephaly in cattle and sheep. The distribution and prevalence of AKAV infection in China is still unknown. A total of 2731 sera collected from 2006 to 2015 in 24 provinces of China from cattle, sheep, goats and yak were examined by serum neutralisation test. The overall seroprevalence rates for AKAV antibodies were 21.3% in cattle (471/2215) and 12.0% (17/142) in sheep or goats, and 0% in yak (0/374). The results indicated widespread AKAV infection in China among cattle and sheep but yak appear to have a low risk of infection. Using a selection of 50 AKAV-positive and 25 AKAV-negative cattle sera, neutralisation tests were also conducted to detect antibodies to several other Simbu serogroup bunyaviruses and closely related Leanyer virus. Although inconclusive, the data suggest that both Aino virus and Peaton virus, which have been reported previously in Japan and Korea, may also be present in cattle in China.