Search Results (68)

Maedi-visna virus (MVV), a small ruminant lentivirus causing chronic multisystemic disease in sheep, poses significant economic burdens due to reduced productivity and a lack of effective treatments. Despite its worldwide prevalence, epidemiological data from Algeria remain absent. This first national seroprevalence study aimed to elucidate MVV distribution, risk factors, and transmission dynamics in Algerian sheep herds. A cross-sectional survey of 1400 sheep across four regions (East, Center, West, South) was conducted, with sera analyzed via indirect ELISA (IDvet). Risk factors (geography, age, sex, breed, farming system) were evaluated using chi-square tests and Cramer’s V. Overall seroprevalence was 9.07% (95% CI: 7.57–10.57), with significant variation by sex (females: 20.44% vs. males: 3.68%; p < 0.05), age (1–5 years: 6.86% vs. <1 year: 0.29%; p = 0.01), and region (Central: 3.36% vs. Eastern: 0.86%; p < 0.05). Notably, no association was found with breed or farming system (p ≥ 0.08), contrasting prior studies and suggesting region-specific transmission dynamics. Females exhibited heightened seropositivity, implicating prolonged herd retention and vertical transmission risks. Geographic disparities highlighted industrialized farming in central Algeria as a potential transmission amplifier. Strikingly, seronegative animals in high-prevalence herds hinted at genetic resistance, warranting further investigation. This study provides foundational insights into MVV epidemiology in North Africa, underscoring the need for targeted surveillance, ewe-focused control measures, and genetic research to mitigate transmission. The absence of prior national data elevates its significance, offering actionable frameworks for resource-limited settings and enriching the global understanding of SRLV heterogeneity. Full article

Small ruminant lentiviruses (SRLVs) are widespread and have a long co-evolutionary history with their hosts, namely sheep and goats. These viruses induce insidious pathologies, causing significant financial losses and animal welfare issues for the affected flocks. In Switzerland, in the 1980s, an eradication campaign was launched targeting these viruses, exclusively in goats, eliminating the virulent SRLV-B strains from the goat population, in which SRLV-B-induced arthritis was prevalent. Nevertheless, although they do not seem to induce clinical diseases, SRLV-A strains continue to circulate in Swiss goats. For this study, we contacted farmers who had animals testing positive for these strains during the census from 2011 to 2012 and visited six of these flocks, conducting serological, virological, and clinical analyses of the animals. We confirmed the absence of SRLV-B; however, we have detected SRLV-A in these flocks. Positive and negative animals lived in close contact for ten years and, except for a small flock of 13 animals, 7 of which tested positive, the transmission of these viruses proved inefficient. None of the positive animals showed any pathology attributable to SRLV infection. These encouraging results allowed us to formulate recommendations for the continued surveillance of these viruses in the Swiss goat population. Full article

Caprine arthritis and encephalitis (CAE), caused by small ruminant lentivirus (SRLV), is a key disease of goats, with chronic inflammation of joints and brain symptoms leading to losses in milk production and animal trade. In this study, we analyzed gene expressions in the milk somatic cells (MSCs) of seropositive (SRLV-SP) and seronegative (SRLV-SN) goats to identify transcriptomic changes using a non-invasive sampling method. Materials and Methods: This study was conducted on goats of two Polish breeds (Polish Improved White and Polish Improved Fawn), which were kept at the Institute of Genetics and Animal Biotechnology, Polish Academy of Sciences, during their first lactation. MSCs were isolated from milk, and gene expression was analyzed using the Goat Gene Expression Microarray. The results were verified by RT-qPCR for five genes (DUSP26, PRLR, SCARA3, APBB2, OR4F4). Statistical analysis was performed in GeneSpring 12 software. Results: Microarrays showed reduced expression of DUSP26, PRLR, SCARA3, APBB2, and OR4F4 genes in SRLV-SP goats. RT-qPCR confirmed changes for DUSP26, SCARA3, and APBB2. Functional analysis indicated associations with immune processes and HIV-like pathways. Discussion: The results suggest that SRLV induces transcriptomic perturbations, especially in immunity-related genes. MSCs are an effective model for non-invasive studies, and further studies may support strategies for combating CAE. Full article

Vaccination plays a pivotal role in the control and prevention of animal infectious diseases. However, no efficient and safe universal vaccines are currently registered for major pathogens such as influenza A virus, foot-and-mouth disease virus (FMDV), simian immunodeficiency virus (SIV), and small ruminant lentiviruses (SRLV). Here, we review the development of Sendai virus (SeV) vectors as a promising vaccine platform for animal diseases. Recombinant SeV vectors (rSeVv) possess several key features that make them highly suitable for developing vaccination strategies: (1) SeV has exclusively cytoplasmic replication cycle, therefore incapable of transforming host cells by integrating into the cellular genome, (2) rSeVv can accommodate large foreign gene/s inserts (~5 kb) with strong but adjustable transgene expression, (3) can be propagated to high titers in both embryonated chicken eggs and mammalian cell lines, (4) exhibits potent infectivity across a broad range of mammalian cells from different animals species, (5) undergo transient replication in the upper and lower respiratory tracts of non-natural hosts, (6) has not been associated with disease in pigs, non-humans primates, and small ruminants, ensuring a favorable safety profile, and (7) induce a robust innate and cellular immune responses. Preclinical and clinical studies using rSeVv-based vaccines against influenza A virus, FMDV, SIV, and SRLV have yielded promising results. Therefore, this review highlights the potential of rSeVv-based vaccine platforms as a valuable strategy for combating animal viruses. Full article

In 2011–2013, we isolated and characterized small ruminant lentiviruses (SRLVs) from two flocks, one of goats and the other of sheep, that had never been in direct contact. Phylogenetic analysis of these viruses indicated a common origin, which led us to hypothesize indirect transmission of these viruses between the two flocks. Since, to our knowledge, there are no published data on the tenacity of these viruses, we started this work. In the first part, we monitored the loss of infectivity of two prototypic SRLV strains, MVV 1514 and CAEV-CO, over time, in liquid suspension. As expected, the suspensions stored at 4 °C better preserved the infectivity of the viruses. Additionally, viruses resuspended in milk, the medium mirroring the in vivo situation, proved more tenacious than those maintained in a cell culture medium. These viruses, subjected to harsh treatments such as drying and resuspending, partially maintained their replication capacity. After an immediate loss of nearly 1 log₁₀ TCID₅₀ immediately after desiccation, the viruses maintained their replication capacity for at least three weeks when desiccated in milk. These results suggest that fomites, clothing, or pastures contaminated with secretions or milk from infected animals might mediate the infection of animals independently of direct contact. Full article

Small ruminant lentiviruses (SRLVs) cause a persistent, chronic degenerative, multisystem disease in goats and sheep. This study was performed to assess the genetic distribution of SRLV in Mexico and the risk factors that favor its presence in sheep and goats across different production units. In total, 890 goats and sheep (383 and 507, respectively) from 52 mixed-species and single-species flocks in the northern, central, and southern regions of Mexico were analyzed. Serological and molecular diagnoses were conducted. PCR-positive samples were further analyzed via real-time PCR to identify genotypes A and B. The survey data were evaluated to determine the relationship between virus presence, seropositivity, and associated factors in the flocks. Of the 890 animals sampled (507 sheep and 383 goats), 40% (354/890) tested positive for antibodies specific for SRLV (229 goats and 125 sheep), while 78% (697/890) were positive for the viral genome (340 goats and 357 sheep). The results confirmed that genotype A circulated in 15% of infected animals, genotype B circulated in 66%, and 19% were co-infected with both genotypes. This study highlights the circulation and spread of SRLV genotypes A and B in goat and sheep flocks in Mexico. The risk factors that showed a significant association with seropositivity were age, flock size, and veterinary assistance. For molecular positivity detection, production with mixed flocks was added as a variable in the central region cluster, in addition to the variable knowledge of SRLV diseases and contact with other flocks in the sheep cluster. Other factors such as species cohabitation, cleanliness, and preventive measures were associated with the presence of clinical signs. Full article

Small ruminant lentiviruses (SRLVs) infect sheep, causing a multiorganic disease called maedi-visna or ovine progressive pneumonia, which significantly affects the production and welfare of sheep, generating serious economic losses. Although not all infected animals develop fully symptomatic disease, they constantly spread the virus in the flock. Since the infection is incurable and no vaccine is available, another approach is necessary to control SRLV infections. In recent years, an alternative for culling infected animals has become the approach based on identifying genetic markers for selecting SRLV-resistant individuals. Recent reports revealed several candidates, including gene encoding transmembrane protein 154 (TMEM154). Several single nucleotide polymorphisms (SNPs) are found within this gene in sheep of different breeds, but only some can be considered as resistant markers. This study aimed to investigate the presence of single polymorphic sites in TMEM154 gene in sheep of selected Polish flocks and assess their association with the infection and proviral load in the context of susceptibility to SRLV infection. In total 107 sheep, representing three breeds, were screened for their SRLV infection status by serological and PCR testing. All these animals were also genotyped to characterize the presence of SNPs in TMEM154 gene and estimate their potential of being the SRLV-resistance marker. The frequency of identified alleles differed among breeds. Moreover, the positive association between TMEM154 genotype and SRLV status was found for E35K polymorphism and two polymorphic sites in 5′UTR in one of analyzed breed. However, when the relationship between SNPs and SRLV proviral load was analyzed, five had a strong association, considering the whole population of tested sheep. Presented data, for the first time, identified the presence of SNPs in TMEM154 gene in sheep housed in Polish flocks and suggested that selecting SRLV-resistant animals based on this analysis might be possible, but further validation in a larger group of sheep is required. Full article

Small ruminant lentiviruses (SRLVs) are responsible for chronic and progressive multisystemic clinical forms, which significantly reduce flocks’ productivity and have a considerable economic impact on the small ruminant industry. Due to the increase in genetic analysis studies and the potential for misclassification of certain strains, owing to the high genetic variability of these viruses, a systematic review was deemed necessary. This review explores the types of matrices used for molecular detection and phylogenetic studies, the genomic regions selected as targets, and the software utilized for phylogenetic analysis, assessing the geographical distribution of identified genotypes and subgenotypes over time. A thorough comparison of the diagnostic approaches highlights the strengths and limitations of each method, identifying gaps that need to be addressed. Additionally, recombination events and compartmentalization are examined to provide an updated, detailed, and comprehensive overview of SRLV phylogenesis. Full article

In 2023, a molecular study was conducted on the Hungarian goat population to determine genotypes and subtypes of small ruminant lentiviruses (SRLV) infecting these herds. Ten goat herds seropositive for SRLV infection according to a serosurvey conducted earlier in Hungary were selected, and 135 adult goats (>1 year old) were blood sampled. The two-stage nested real-time PCR (nRT-PCR) was used to detect proviral DNA of SRLV and distinguish between two main viral genotypes (A and B). PCR products were submitted for Sanger dideoxy sequencing, and phylogenetic and molecular evolutionary analyses were conducted on the 200–250 bp-long proviral DNA sequences from the end of long terminal repeat (LTR) region and beginning of gag gene using the MEGA11 software. Reference strains included strains most identical to Hungarian sequences according to the Standard Nucleotide BLAST and prototypic strains for the relevant genotypes and subtypes. Proviral DNA of SRLV was detected in goats from all ten tested herds. A single SRLV genotype was detected in 6 herds—genotype A in three herds and B also in three herds. In four herds, mixed infection with genotypes A and B was confirmed. In total, 110/135 seropositive goats tested positive in the nRT-PCR (81.5%): 49/110 goats (44.5%) for genotype A, 54/110 goats (49.1%) for genotype B, and 7/110 goats (6.4%) for both genotypes. Hungarian sequences belonged to subtypes A1/A18, A2, and subtype B1. This is the first study which shows that Hungarian goats are infected by SRLV belonging to both genotypes A and B. Full article

Small ruminant lentivirus (SRLV) infections are spread in the flocks of sheep and goats all over the world, causing economic loss. Although only a fraction of infected animals develop disease symptoms, all of them may shed the virus, causing uncontrolled spread of the infection. Antibodies against the virus can be detected in the blood of infected animals and are the main marker of infection. Additionally, in most infected animals, proviral DNA can also be detected, but at different levels. Due to the lack of treatment or vaccines, the most effective strategy to prevent SRLV infections are control programmes introduced by several countries based on the elimination of seropositive individuals from the flock. An alternative approach, which has currently become the rationale, is an identification of host factors which may predispose certain individuals or breeds to resistance or susceptibility to small ruminant lentivirus infection. In our work, attention was paid to goats of the Carpathian breed infected with SRLV. Available RNA-seq results from the blood of 12 goats with a determined level of SRLV proviral load were used to analyse single nucleotide polymorphisms (SNPs) by the variant calling method. Six SNPs within five genes (POU2AF1, BCAT2, TMEM154, PARP14, UBASH3A) were selected for genotyping to determine their association with the level of small ruminant lentivirus proviral DNA in a group of 60 goats. Interestingly, in seronegative individuals, only the TT genotype of the PARP14 gene was observed, while the TMEM154 CC genotype was found only in seropositive goats. Both genes may be considered potential markers for resistance/susceptibility to SRLV infection. In contrast, polymorphisms identified in POU2AF1 and UBASH3A genes seemed to be deleterious for respective protein functions; therefore, these genes are less likely to be recognised as resistance/susceptibility markers of SRLV infection. Full article

(1) Background: Information is lacking on small ruminant lentivirus (SRLV) status, prevalence, risk factors, and control measures for mastitis in California ewes. The goal of this survey was to outline characteristics of the sheep industry in California related to udder health and mastitis management. (2) Methods: An online survey consisting of 48 questions was completed by respondents between April 2022 and February 2023. Descriptive analysis and chi-squared tests were conducted to evaluate associations between variables. A multiple correspondence analysis (MCA) of general management practices, udder health management, and flock demographics was performed to assess clustering. A subset of respondents (20) participated in SRLV serology testing. (3) Results: Seventy-one completed surveys were submitted. The MCA showed two clusters. Larger flock sizes, the use of breeding ewes for meat or wool production or contract grazing, and extensive management practices were more closely related to >5% udder abnormalities per lactation and ≥5% orphan lambs. The flock-level seroprevalence of SRLV was 75% (15/20), and ewe-level seroprevalence was 14.1% (183/1106). (4) Conclusions: The results of this study highlight areas that need further research, such as exploring differences in mastitis and SRLV incidences among management systems, the efficacy of mastitis treatments, and education on critical timepoints for mastitis diagnosis and control. Full article

The Maedi-visna virus (MVV) causes a persistent infection in small ruminants, and its high genetic heterogeneity affects the performance of diagnostic tests when used in different populations. Therefore, the aim of this study was to develop a bead-based multiplex immunoassay tailored to detect antibodies against a Norwegian MVV strain. We used tissue samples from 14 PCR-positive sheep from a recent MVV outbreak in Norway to sequence the viral strain and produced recombinant antigens based on sequences from one animal. The assay included commercial TM-A and recombinant Norwegian p25, p16–25 and SU5 antigens. Cut-off values for each antigen were determined using receiver operating characteristic curves on 40 ELISA-negative and 67 ELISA-positive samples from the outbreak. The intraplate and interplate repeatability were investigated by testing a quadruplicate of five samples over three days, while the analytical sensitivity (aSe) and specificity (aSp) were measured in comparison to a commercial ELISA. The repeatability showed a coefficient of variation below 15% for most positive samples. The aSe was equal or higher for the multiplex assay than the ELISA, and the aSp of each antigen was 91.7, 93.3, 95.0 and 93.3% for p25, p16–25, SU5 and TM-A, respectively. The assay shows promising results; however, further evaluations of diagnostic characteristics are necessary before implementation in the Norwegian surveillance programme. Full article

Small ruminant lentiviruses are a group of viruses infecting goat and sheep worldwide. These viruses exhibit an extraordinary degree of genetic and antigenic variability that severely influence in vivo and in vitro features, as well as diagnostic test results. Small ruminant farming is the most important animal farming business in Greece, with a high impact on the Greek primary economy. Although SRLV infection and its impact on animal production are well established in the country, little is known about the circulating SRLV strains and their prevalence. The aim of this study was to characterize SRLVs circulating in Greece with a combined serological and molecular approach, using the bulk milk matrix collected from 60 farms in different municipalities. This study allowed us to estimate a seroprevalence of around 52% at the herd level. The B1, B2 and A3 subtypes and a novel A viral cluster were identified. Moreover, the amplicon sequencing method allowed us to identify more than one viral subtype in a sample. These results again confirm the high variability of these viruses and highlight the importance of the constant monitoring of viral evolution, in particular in antigens of diagnostic interest. Full article

The high genetic heterogeneity of small ruminant lentiviruses (SRLV) renders the genetic characterization of the circulating strains crucial for the epidemiological investigation and the designation of effective diagnostic tools. In Greece, research data regarding the genetic diversity of the circulating SRLV strains is scarce, hindering the implementation of efficient surveillance and control programs. The objective of the study was to genetically characterize SRLV strains isolated from intensive dairy sheep farms in Greece and evaluate the variability of the immunodominant regions of the capsid protein. For this reason, a total of 12 SRLV-infected animals from four intensive dairy sheep farms with purebred Chios and Lacaune ewes were used for the amplification and sequencing of an 800 bp gag-pol fragment. The phylogenetic analyses revealed a breed-related circulation of strains; Chios ewes were infected with strains belonging exclusively to a separate group of genotype A, whereas strains belonging to subtype B2 were isolated from Lacaune ewes. Immunodominant epitopes of capsid protein were quite conserved among the strains of the same genotype, except for the Major Homology Region which showed some unique mutations with potential effects on viral evolution. The present study contributes to the extension of the current knowledge regarding the genetic diversity of SRLV strains circulating in sheep in Greece. However, broader genetic characterization studies are warranted for the exploration of possible recombinant events and the more comprehensive classification of the circulating strains. Full article

Recent studies that investigated the origins of SRLV strains offered new insights into their distribution among domestic ruminants. The aim of the study was to investigate SRLV circulation in Morocco. A total of 51 farms were selected in different geographical locations and tested by screening and genotyping ELISA. Whole blood was used for DNA extraction and nested gag PCR. The sample size allowed for an estimation of prevalence lower than 20% (CI 95%). Surprisingly, a large proportion of screening-positive samples were not correctly serotyped. Sanger and NGS amplicon sequencing approaches allowed us to obtain new sequences even from difficult-to-amplify samples. The serological data support the evidence of an intrinsic difficulty of SRLV to spread, likely due to management practices. The low rate of success by genotyping ELISA led us to suppose that divergent strains might have escaped from diagnostic tools, as partially confirmed by the evidence of an A subtype carrying a mismatch in serotyping epitope. The sequence analysis revealed the circulation of novel B and recombinant A/B subtypes. This study highlights the importance of monitoring viral sequences and their evolution to develop specific diagnostic tests, particularly in countries where control measures are in place. Full article