Visna Research Articles

Scrapie at Abattoir: Monitoring, Control, and Differential Diagnosis of Wasting Conditions during Meat Inspection.

Simple SummaryObservation of small ruminants showing differing degrees of leanness or emaciation is a common occurrence at slaughterhouses. Although either condition may result from similar causes, emaciation and cachexia are usually pathological conditions, warranting total condemnation of the carcass during post-mortem inspection. This is done in order to prevent unfit meat from entering the human food chain. Scrapie, a naturally occurring transmissible spongiform encephalopathy in small ruminants, is characterized by loss of body conditioning and a wasting appearance. Since atypical scrapie has been identified as occurring at a low, but very consistent, the prevalence in small ruminant populations, it is advisable to include this disease as a differential diagnosis of wasting conditions detected during meat inspection at the abattoir. Vigilance for detection of putative scrapie in slaughterhouses, and its differential diagnosis from other conditions associated with wasting carcasses, are of paramount importance for post-mortem decisions on the fate of carcasses, offal, as well as animal by-products.Wasting disease in small ruminants is frequently detected at slaughterhouses. The wasting disorder is manifested by the deterioration of the nutritional and physiological state of the animal indicated by thinness, emaciation, and cachexia. Evidence of emaciation and cachexia, alone, are pathological conditions leading to carcass condemnation during an inspection. Several diseases are associated with a wasting condition, including scrapie, pseudotuberculosis, tuberculosis, paratuberculosis, Maedi Visna, and tumor diseases. On the other hand, parasitic diseases, nutrition disorders, exposure or ingestion of toxins, metabolic conditions, inadequate nutrition due to poor teeth, or poor alimentary diet are conditions contributing to poor body condition. Classical and atypical scrapie is naturally occurring transmissible spongiform encephalopathies in small ruminants. The etiological agent for each one is prions. However, each of these scrapie types is epidemiologically, pathologically, and biochemically different. Though atypical scrapie occurs at low incidence, it is consistently prevalent in the small ruminant population. Hence, it is advisable to include differential diagnosis of this disease, from other possibilities, as a cause of wasting conditions detected during meat inspection at the abattoir. This manuscript is a review of the measures in force at the abattoir for scrapie control, focusing on the differential diagnosis of gross lesions related to wasting conditions detected in small ruminants during meat inspection.

Effect of TMEM154 E35K variant (haplotypes 1 and 3) on the incidence of ovine lentivirus infection and ewe productivity during lifetime exposure.

Ovine progressive pneumonia virus (OPPV) is a small ruminant lentivirus that is widespread throughout U.S. sheep flocks. Infections with OPPV are lifelong and effects are multi-systemic with significant implications for animal well-being and productivity. A protein isoform with lysine at position 35 (K35, haplotype "1") encoded by the ovine transmembrane protein 154 (TMEM154) gene has been associated with reduced susceptibility to infection when two copies are present (i.e., diplotype "1,1"). Conversely, the ancestral protein isoform with glutamate at position 35 (E35, haplotype "3") is associated with high susceptibility to infection when at least one copy is present. The beneficial effect of TMEM154 K35 alleles on ewe productivity has not been previously measured in controlled challenge experiments and was a major objective of this study. Ewes with TMEM154 diplotypes "1,1"; "1,3"; and "3,3" (n = 31, 47, and 30, respectively) were born and reared by OPPV-infected dams and managed under continual natural exposure to OPPV. Ewes were tested for serological status at 4-mo intervals for up to 5.5 yr. The incidence of infection in ewes with diplotype "1,1" was 6.5% to 9.7% and significantly lower (P < 0.001) than ewes with diplotype "1,3" (60.5 to 97.3%) or "3,3" (64.0 to 91.4%). Furthermore, the incidence among ewes with diplotype "1,1" did not increase from 10 to 67 mo of age (P > 0.99), whereas the incidence among diplotype "1,3" and "3,3" ewes increased steadily until reaching an asymptote at approximately 52 mo of age. Total number and weight of lamb weaned per ewe exposed through 5.5 yr from ewes with diplotype "1,1" far exceeded (P ≤ 0.05) those with diplotypes "1,3" and "3,3" by, on average, 2.1 lambs and 40 kg, respectively. The present study confirmed that TMEM154 diplotype "1,1" animals have reduced incidence of OPPV infection and, correspondingly, improved productivity. In flocks with a high frequency of TMEM154 haplotype "3," selection for haplotype "1" appears to be a cost-effective approach to mitigate the impact of this economically important disease.

A novel 2\xa0bp deletion variant in Ovine-DRB1 gene is associated with increased Visna/maedi susceptibility in Turkish sheep

Visna/maedi (VM) is a multisystemic lentivirus infection of sheep that affecting sheep industry across the globe. TMEM154 gene has been identified to be a major VM-associated host gene, nevertheless, a recent study showed that the frequency of the VM-resistant TMEM154 haplotypes was very low or absent in indigenous sheep. Thus, the present study was designed to determine other possible co-receptors associated with VM. For this purpose, DRB1 gene, which is renowned for its role in host immune response against various diseases was targeted. A total number of 151 case–control matched pairs were constructed from 2266 serologically tested sheep. A broad range of DRB1 haplotype diversity was detected by sequence-based genotyping. Moreover, a novel 2 bp deletion (del) in the DRB1 intron 1 was identified. For the final statistic, the sheep carrying VM-resistant TMEM154 diplotypes were removed and a McNemar’s test with a matched pairs experimental design was conducted. Consequently, it was identified for the first time that the 2 bp del variant is a genetic risk factor for VM (p value 0.002; chi-square 8.31; odds ratio 2.9; statistical power 0.90) in the dominant model. Thus, negative selection for 2 bp del variant could decrease VM infection risk in Turkish sheep.

First Survey of SNPs in TMEM154, TLR9, MYD88 and CCR5 Genes in Sheep Reared in Italy and Their Association with Resistance to SRLVs Infection.

Maedi-visna virus (MVV) and caprine arthritis encephalitis virus (CAEV), referred to as small ruminant lentiviruses (SRLVs), belong to the genus Lentivirus of the Retroviridae family. SRLVs infect both sheep and goats, causing significant economic losses and animal welfare damage. Recent findings suggest an association between serological status and allelic variants of different genes such as TMEM154, TLR9, MYD88 and CCR5. The aim of this work was to investigate the role of specific polymorphisms of these genes in SRLVs infection in some sheep flocks in Italy. In addition to those already known, novel variants in the TMEM154 (P7H, I74V, I105V) gene were detected in this study. The risk of infection was determined finding an association between the serological status and polymorphisms P7H, E35K, N70I, I74V, I105V of TMEM154, R447Q, A462S and G520R in TLR9 gene, H176H* and K190K* in MYD88 genes, while no statistical association was observed for the 4-bp deletion of the CCR5 gene. Since no vaccines or treatments have been developed, a genetically based approach could be an innovative strategy to prevent and to control SRLVs infection. Our findings are an important starting point in order to define the genetic resistance profile towards SRLVs infection.

Kars İlindeki Bazı Koyun Sürülerinde Maedi-Visna Enfeksiyonunun Seroprevalansının Araştırılması

Maedi-Visna (MV) is a viral disease that has no treatment and vaccination in sheep which causes chronic respiratory problems, nervous disorders, and yield losses. The aim of this study was to investigate the seroprevalence of MV infection in sheep in Kars province. A total of 200 sheep blood sera taken from 4 local areas (Ortaköy, Boğatepe, Halefoğlu, Borluk) in Kars center were the material of the study. A Commercial ELISA antibody test was used to investigate MV antibodies. At the end of the analysis, 32 of 200 (16%) animals were positive against Maedi-Visna spesific antibodies. At the end of this study, no statistically significant difference was found between the groups in terms of breed, location and gender. Only the difference between ages was determined. In conclusion, this study shows that MV disease occurs in sheep in Kars province.

A DNA Regulatory Element Haplotype at Zinc Finger Genes Is Associated with Host Resilience to Small Ruminant Lentivirus in Two Sheep Populations.

Simple SummarySheep are affected by a viral infection that causes an incurable and difficult to treat lung, joint and brain disease that decreases production efficiency. This small ruminant lentivirus is closely related to human immunodeficiency virus (HIV) that causes AIDS in humans. Differences in breed susceptibility to disease are known in sheep that indicate genetic, or hereditary, resilience factors exist. Our objective was to study the source of this hereditary advantage so that it can eventually be translated into a tool for sheep breeders to improve herd health. Previously, one such hereditary region was detected, but little was known about possible mechanisms or nearby mutations. Here, we report several mutations that may underlie this hereditary mechanism and are in regions of DNA that are known to affect genes by increasing or decreasing gene expression, akin to gene “on/off switches.” These mutations were strongly associated with a predictor of disease severity in live animals and had a greater predicted effect on the degree of disease than previously studied mutations. Statistical association (p < 0.05) of disease was demonstrated in two different groups of sheep that were reared in different environments, which indicates increased likelihood that a genetic factor is producing this effect.Small ruminant lentivirus (SRLV) causes Maedi-Visna or Ovine Progressive Pneumonia in sheep and creates insidious livestock production losses. This retrovirus is closely related to human immunodeficiency virus and currently has no vaccines or cure. Genetic marker assisted selection for sheep disease resiliency presents an attractive management solution. Previously, we identified a region containing a cluster of zinc finger genes that had association with ovine SRLV proviral concentration. Trait-association analysis validated a small insertion/deletion variant near ZNF389 (rs397514112) in multiple sheep breeds. In the current study, 543 sheep from two distinct populations were genotyped at 34 additional variants for fine mapping of the regulatory elements within this locus. Variants were selected based on ChIP-seq annotation data from sheep alveolar macrophages that defined active cis-regulatory elements predicted to influence zinc finger gene expression. We present a haplotype block of variants within regulatory elements that have improved associations and larger effect sizes (up to 4.7-fold genotypic difference in proviral concentration) than the previously validated ZNF389 deletion marker. Hypotheses for the underlying causal mutation or mutations are presented based on changes to in silico transcription factor binding sites. These variants offer alternative markers for selective breeding and are targets for future functional mutation assays.

Gene Expression Profiling Reveals New Pathways and Genes Associated with Visna/Maedi Viral Disease.

Simple SummaryVisna/Maedi is a disease caused by a small ruminant lentivirus (SRLV), with different symptoms in adult sheep such as pneumonia, arthritis, encephalitis and mastitis. SRLV infection in sheep is widespread across the world, with Europe showing the highest individual prevalence. There is currently no effective treatment for SRLV infections and, due to their constant changes, effective vaccine development has been and is still challenging. The dynamics of the sheep immune response to these virus infections is unclear, and changes in gene expression can help to explain the processes occurring in infected sheep. In this study, a gene expression microarray was used to identify the differentially expressed genes in infected and diseased sheep by comparing animals with different serologic statuses and with the presence of VM-characteristic clinical lesions in the lungs. The expression profile analysis revealed many interesting genes that may be associated with the viral infection process (such as OXT and a number of genes implicated in the Toll Like Receptors signaling network and complement pathway). This work improves our understanding of the sheep immune response against SRLVs.Visna/Maedi virus (VMV) is a lentivirus that infects the cells of the monocyte/macrophage lineage in sheep, goats and wild ruminants. Infection with VMV causes a multisystemic inflammatory disorder, which includes pneumonia, encephalitis, mastitis or arthritis. The immune response to VMV infection is complex, and the infection and pathogenesis of this virus are not totally characterized yet. In this work, a gene expression microarray was used to identify the differentially expressed genes in VMV infection and disease development by comparing sheep with different serologic status and with presence of VM-characteristic clinical lesions. The expression profile analysis has revealed many interesting genes that may be associated with the viral infection process. Among them, the OXT gene appeared significantly up-regulated, so the oxytocin-secreting system could play an essential role in VM disease. Moreover, some of the most significantly enriched functions in up-regulated genes appeared the complement pathway, which (in combination with the Toll-like receptor signaling network) could compose a mechanism in the VMV pathogenesis. Identifying the host genetic factors associated with VMV infection can be applied to develop strategies for preventing infection and develop effective vaccines that lead to therapeutic treatments.

Seroprevalence of small ruminant lentivirus infection in goats in Thailand.

Small ruminant lentivirus (SRLV), which causes caprine arthritis encephalitis in goats and ovine progressive pneumonia (maedi-visna disease) in sheep, is classified in genus Lentiviruses belonging to Retroviridae family. It persists in infected goats and sheep, which mostly are sub- clinical. A serological survey was conducted to determine the prevalence of small ruminant lentivirus infection in Thai goat population. Serum samples were taken from 1,925 goats distributed throughout the country, then they were tested for the presence of SRLV antibodies using commercial indirect enzyme-linked immunosorbent assay (ELISA) test kits. Results revealed that a total of 68 goats were found seropositive, representing the apparent prevalence and true prevalence of 3.57% and 2.60%, respectively. The seroprevalence, revealed in this study, was lower than in the previous reports. The decreasing of seroprevalence might be caused by successful control strategies from Department of Livestock Development (DLD).

Prevalence and risk factors associated with Maedi-Visna infection in sheep in the State of Maranhão, Brazil

In order to determine Maedi-Visna virus (MVV) seroprevalence and risk factors associated with infection in sheep, 445 animals of both sexes and different ages were tested using the Agarose Gel Immunodiffusion technique (IDGA). The animals were divided into two groups: group 1 composed of exhibition animals (n=70) and group 2 composed of animals from properties from the north, east and central mesoregions of the state of Maranhão (n=375). The general prevalence of MVV infection was 2.02%; 1.42% in group 1 and 2.13% in group 2. In the north mesoregion the prevalence was 2.20%, while a total of 40% of the animals living in municipalities for MVV. It was observed that 1.15% of males and 2.23% of females were seropositive (p&gt; 0.20). Regarding breeds, the Dorper (1.66%); Santa Inês (1.67%); White Dorper (33.33%) and Texel (4.34%) were the most affected. This was the only variable among all the risk factors studied that had a significant association in multivariate analysis (p &lt;0.05). MVV infection is present regardless of the purpose of breeding, and the animals are exposed to the same risk of infection. This demonstrates the need to implement public policies for the prevention, control, and eradication of this disease.

EVALUATION OF THE RELATIONSHIP BETWEEN MAEDI-VISNA INFECTION AND SERUM APELIN LEVELS IN TERMS OF BREED, GENDER, BODY CONDITION SCORE, LACTATION AND PREGNANCY PERIODS IN EWE USING SEROLOGICAL AND MOLECULAR TECHNIQUES

In this study, the objective was to assess the serological and molecular characteristics of the maedi-visna infection during lactation and pregnancy periods of fat-tailed sheep belonging to the Red Karaman and White Karaman–Kangal race with maedi-visna infection and body condition score (BCS) of ≤2, 3– 3.5 and ≥4 (high) and to analyse the relationship between the level of apelin and its secretion. Apelin level in the blood serum samples obtained from the jugular vein of the sheeps was determined using ELISA method. As a result of the analyses, it was determined that the level of apelin was statistically different between the races; between lactating sheep and pregnant sheep; and sheep and rams. There was no difference between the BCS groups (p > 0.05). Race and sex interaction as well as race, sex and BCS triple interaction effects were found significant (p < 0.05). It was observed that the sheep belonging to the White Karaman–Kangal race were 18 times more likely to be infected with the virus. A decrease in apelin level was observed in the sheep with infection, and it was found that the risk of infection was 0.37 times higher in rams than in lactating sheep (p < 0.05).

Next-generation sequencing for the genetic characterization of Maedi/Visna virus isolated from the northwest of China.

BackgroundMaedi/Visna virus (MVV) is a contagious viral pathogen that causes considerable economic losses to the sheep industry worldwide.ObjectivesIn China, MVV has been detected in several regions, but its molecular characteristics and genetic variations were not thoroughly investigated.MethodsTherefore, in this study, we conducted next-generation sequencing on an MVV strain obtained from northwest China to reveal its genetic evolution via phylogenetic analysis.ResultsA MVV strain obtained from Inner Mongolia (NM) of China was identified. Sequence analysis indicated that its whole-genome length is 9193 bp. Homology comparison of nucleotides between the NM strain and reference strains showed that the sequence homology of gag and env were 77.1%–86.8% and 67.7%–75.5%, respectively. Phylogenetic analysis revealed that the NM strain was closely related to the reference strains isolated from America, which belong to the A2 type. Notably, there were 5 amino acid insertions in variable region 4 and a highly variable motif at the C-terminal of the surface glycoprotein (SU5).ConclusionsThe present study is the first to show the whole-genome sequence of an MVV obtained from China. The detailed analyses provide essential information for understanding the genetic characteristics of MVV, and the results enrich the MVV library.

Maedi–visna virus Vif protein uses motifs distinct from HIV-1 Vif to bind zinc and the cofactor required for A3 degradation

The mammalian apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3 or A3) family of cytidine deaminases restrict viral infections by mutating viral DNA and impeding reverse transcription. To overcome this antiviral activity, most lentiviruses express a viral accessory protein called the virion infectivity factor (Vif), which recruits A3 proteins to cullin–RING E3 ubiquitin ligases such as cullin-5 (Cul5) for ubiquitylation and subsequent proteasomal degradation. Although Vif proteins from primate lentiviruses such as HIV-1 utilize the transcription factor core-binding factor subunit beta as a noncanonical cofactor to stabilize the complex, the maedi–visna virus (MVV) Vif hijacks cyclophilin A (CypA) instead. Because core-binding factor subunit beta and CypA are both highly conserved among mammals, the requirement for two different cellular cofactors suggests that these two A3-targeting Vif proteins have different biochemical and structural properties. To investigate this topic, we used a combination of in vitro biochemical assays and in vivo A3 degradation assays to study motifs required for the MVV Vif to bind zinc ion, Cul5, and the cofactor CypA. Our results demonstrate that although some common motifs between the HIV-1 Vif and MVV Vif are involved in recruiting Cul5, different determinants in the MVV Vif are required for cofactor binding and stabilization of the E3 ligase complex, such as the zinc-binding motif and N- and C-terminal regions of the protein. Results from this study advance our understanding of the mechanism of MVV Vif recruitment of cellular factors and the evolution of lentiviral Vif proteins.

Western Blot in Immunodiagnosis of Small Ruminant Lentivirus

Background: Small ruminant lentiviruses (SRLV) belong to genus Lentivirus, family Retroviridae. These viruses cause caprine arthritis encephalitis (CAE) and maedi visna (MV), infectious diseases that cause economic, production, and reproductive losses. There are no effective treatments or vaccines for these diseases. Thus, early detection via serology has great importance for control of SRLV. Therefore, the objective of this review is to demonstrate the potential of the western blot (WB) test as an immunodiagnostic test for SRLV. Review: In general, immunodiagnosis of SRLV is performed via agar gel immunodiffusion (AGID) and indirect enzyme-linked immunosorbent assay (ELISA), which can detect antibodies in several different biological samples but is used preferably with serum and blood plasma. However, WB has demonstrated efficacy in the early diagnosis of immunoglobulins against SRLV, presenting higher sensitivity and specificity than the serological tests usually used, because this technique can detect antibodies at a dilution as much as 256 times greater than that of AGID and 32 times greater than that of ELISA. SRLV infection and consequent immunological activation result in the induction of cellular and humoral responses. Additionally, around the third week, production of antibodies directed mainly toward viral capsid proteins (p25 and p28) occurs. After the fifth week, production of immunoglobulins directed toward other viral proteins occurs. Because of the persistence of SRLV infection, serology is considered to be the most practical means to diagnosis. Each serological test has a percentage specificity and distinct sensitivity, as well as advantages and disadvantages in its applicability. It should be noted that there is no gold standard test for diagnosis of SRLV infection. Moreover, SRLV are characterized by escape mechanisms such as genetic diversity, mutagenic potential, viral intermittence, and the process of compartmentalization, which make immunodiagnosis more difficult. In addition, positive animals tend to present unstable levels of antibodies over weeks, months, and even years. In this context, WB, with early antibody detection, has been proven to be a refined and more accurate technique than other immunodiagnostic tests for SRLV. WB allows the simultaneous resolution of several immunogenic antigens present in a sample, and this feature provides it with greater reliability, differentiates it from other immunological methods, and accredits it as a test of wide applicability. Epidemiological and immunological dynamics studies often use WB in the immunodynamic diagnosis of SRLV. Serum, blood plasma, and seminal plasma are typical biological materials used in the serological diagnosis of SRLV with WB, expanding its potential as an immunodiagnosis method.Conclusion: WB is the most accurate serological technique for SRLV. It is more capable of accurate diagnosis because the genetic diversity that characterizes such lentiviruses and their various immune system escape mechanisms routinely hinder traditional diagnosis. Additionally, this test has been used widely in studies of SRLV for various purposes, but mainly in studies of epidemiological and immunological dynamics, using serum, blood plasma, or seminal plasma. However, independently of the biological sample tested, WB maintains high sensitivity and precision in immunodiagnosis, making it a refined and valid technique for SRLV control programs.

Infectious diseases surveillance of the Iberian ibex (Capra pyrenaica victoriae) in Western Spain: health and conservation implications

A survey was conducted between 2004 and 2011 to identify potential pathogens present in the main subpopulation of Iberian ibex subspecies Capra pyrenaica victoriae, located in Gredos Mountain range in Western Spain. Samples were collected from 144 animals and subjected to specific procedures to detect the presence of, or evidence of exposure to, viral, bacterial and parasitic agents. A wide diversity of parasites was found, including 17 species of gastrointestinal nematodes and lungworms, nine species of Coccidia and three of Cestoda. Overall, 54% (75/138) of animals were parasitized by ticks (Rhipicephalus bursa, Ixodes ricinus, Haemaphysalis sulcata, and Hyalomma marginatum marginatum). Null detection of Sarcoptes scabiei mites, causal agent of sarcoptic mange, must be highlighted. Serological assays revealed exposure to Babesia ovis (43%, 56/129), Neospora caninum (13%, 14/108), Oestrus spp. (10%, 4/42), Coxiella burnetii (10%, 5/50), Mycobacterium bovis (6%, 3/50), and Toxoplasma gondii (3%, 4/137). We did not detect the presence of antibodies against Chlamydia psittaci, Brucella spp., Mycobacterium avium subspecies paratuberculosis, Visna-Maedi virus and Bluetongue virus. Despite the fact that major pathogens for animal health were not evidenced, the implementation of periodic passive surveillance programs directed to both wildlife and livestock is highly desirable to predict outbreaks that may compromise survival of such wild goat subspecies.

Evaluation of Two SNP Markers in DPPA2 and SYTL3 Genes for Association with Host Response against Visna/Maedi Infection in Turkish Sheep

Visna/maedi (VM) is an incurable viral disease of sheep causing serious production losses across the globe. Classical control measures against VM such as screening and culling are costly and time-consuming. Breeding VM resistant sheep could provide an opportunity for struggling with the VM and decreasing the economic loss. In this study, we aimed to investigate possible associations between two previously reported single nucleotide polymorphisms (SNPs) in the ovine DPPA2 and SYTL3 genes and VM serostatus, and evaluate implementation of selective breeding strategies against VM in Karacabey merino, Kivircik, Imroz, and composite breeds; Bandirma, Hampshire crosses (HAMP), Ramlic and Black-headed German mutton crosses (SBA) which are reared in Marmara region of Turkey. For this purpose, we genotyped the sheep which VM serostatus were determined previously. The genotyping results showed that these SNPs in the DPPA2 and SYTL3 genes are polymorphic. We have conducted an association analysis with an experimental design using case-control matched pairs. Finally, a power analysis was performed to determine the power of the statistical analysis. According to our findings, within our detection limits (the minimum odds ratio 2.5 to 2.8; CI 95; statistical power 0.96; p-value < 0.05), there was no significant association between the SNPs in the DPPA2 and SYTL3 genes and VM serostatus. Therefore, these SNP markers are not useful to selective breeding against VM in Turkish sheep.

Sero-prevalence and associated risk factors of Maedi-visna virus in sheep population of selected area of eastern Amhara, Ethiopia

Sero-prevalence and associated risk factors of Maedi-visna virus in sheep population of selected area of eastern Amhara, Ethiopia

Bioactive monolaurin as an antimicrobial and its potential to improve the immune system and against COVID-19: a review

Monolaurin is monoacylglycerol which is a bioactive lipid since it can affect the human biological systems. This review discusses the bioactive properties of monolaurin, especially its role as an antibacterial, immune system enhancement, and its ability as an antiviral so that it has the potential to fight against various viral attacks. Monolaurin can act as an antibacterial in inhibiting the growth of several pathogenic bacteria, especially gram-positive bacteria. Monolaurin is known to be able to enhance the immune system through modulation of various immune systems, controlling pro-inflammatory cytokines, activating and attracting leukocytes to the site of infection. Monolaurin can also act as an antiviral, especially against enveloped viruses, such as Maedi-visna virus, vesicular stomatitis, herpes simplex-1, measles, HIV, cytomegalovirus, influenza, and corona. Monolaurin inhibits the virus through the mechanism of the disintegration of the viral membrane, prevents binding of the viral protein to the host-cell membrane, inhibits the process of assembling the viral RNA, and the process of virus maturation in the replication cycle. Therefore monolaurin has the potential for human consumption to boost the immune system and ward off various virus attacks, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the cause of COVID-19 which became a pandemic in the world.

Epidemiology and control of maedi-visna virus: Curing the flock.

Maedi-visna (MV) is a complex lentiviral disease syndrome characterised by long immunological and clinical latencies and chronic progressive inflammatory pathology. Incurable at the individual level, it is widespread in most sheep-keeping countries, and is a cause of lost production and poor animal welfare. Culling seropositive animals is the main means of control, but it might be possible to manage virus transmission effectively if its epidemiology was better quantified. We derive a mathematical epidemiological model of the temporal distributions of seroconversion probabilities and estimate susceptibility, transmission rate and latencies in three serological datasets. We demonstrate the existence of epidemiological latency, which has not explicitly been recognised in the SRLV literaure. This time delay between infection and infectiousness apparently exceeds the delay between infection and seroconversion. Poor body condition was associated with more rapid seroconversion, but not with a higher probability of infection. We estimate transmission rates amongst housed sheep to be at about 1,000 times faster than when sheep were at grass, when transmission was negligible. Maternal transmission has only a small role in transmission, because lambs from infected ewes have a low probability of being infected directly by them, and only a small proportion of lambs need be retained to maintain flock size. Our results show that MV is overwhelmingly a disease of housing, where sheep are kept in close proximity. Prevalence of MV is likely to double each year from an initial low incidence in housed flocks penned in typically-sized groups of sheep (c. 50) for even a few days per year. Ewes kept entirely at grass are unlikely to experience transmission frequently enough for MV to persist, and pre-existing infection should die out as older ewes are replaced, thereby essentially curing the flock.

Test positivity for Maedi–Visna virus and Mycobacterium avium ssp. paratuberculosis in Sarda ewes: Effects on milk composition and coagulation traits and heritability estimates for susceptibility

Maedi-Visna virus (MVV) and Mycobacterium avium ssp. paratuberculosis (MAP) are two pathogens that cause chronic, production-limiting diseases in dairy sheep. Although they are present worldwide, there are no detailed reports on their actual effects on milk traits in the literature. This study was designed to investigate the effects of test positivity to MVV and MAP on ovine milk yield, composition and coagulation properties, and curd-firming over time (CFt) variables in clinically healthy animals at the field level. The additive genetic variation and heritabilities of MVV and MAP positivity were also estimated. Milk samples were collected from 1,079 Sarda sheep kept on 23 farms, and pedigree information was obtained from the flock book. Milk yield was also recorded on the sampling date. Positivity for MVV and MAP was determined from milk samples using indirect ELISA test kits. Milk composition traits were measured by spectroscopy, milk coagulation properties were measured with a Formagraph (Foss Italia, Padua, Italy), and CFt traits were calculated using the data from the Formagraph diagram. The effects of MVV and MAP positivity on milk traits were determined through a set of mixed linear models, which took into account various sources of variation, such as days in milk, parity, and flock effects, and included the effects (positive or negative) of the 2 pathogens. A Bayesian threshold sire model with sire relationship was used to estimate genetic variation and heritability. The overall animal prevalence of MVV-positive ewes was 43.6%; on only 1 farm of the 23 tested were all sampled ewes negative. An overall animal prevalence of 10.6% was recorded for MAP, with 4 farms at 0%. Positivity for MVV significantly affected the logarithmic score of the bacterial count, curd firmness after 30 min and 45 min, and the curd-firming instant rate constant. We found significant effects of MAP infection on milk composition, pH, and rennet coagulation time. The mean of the posterior distributions of heritability estimates on the liability scale was 0.15 for MAP and 0.07 for MVV. Our results demonstrate that only a few traits are negatively affected by MVV and MAP positivity, and that there is exploitable genetic variation in MVV and MAP susceptibility in dairy sheep.

PREVALENCE OF SMALL RUMINANT LENTIVIRUS INFECTIONS IN SHEEP AND GOATS IN SOME REGIONS OF VOJVODINA PROVINCE

Small Ruminant Lentivirus causes a chronic lifelong, multisystemic diseases in sheep and goats with or without clinical manifestation. Maedi-visna virus (MVV) and Caprine arthritis encephalitis virus (CAEV) are often considered together as small ruminants lentivirus (SRLV) due to their phylogenetic correlation and the interspecies transmission between sheep and goats.&#x0D; During the period of four years, from 2015-2018, an annual monitoring was done on male animals (rams and bucks) used for breeding, for determination of antibodies against SRLV with ELISA serological method. In total, serum samples from 6732 animals were analyzed.&#x0D; During the study period, seroprevalence for small ruminant lentivirus has rised from 4,17% to 16,21%, with an overall value of 12% for the whole period. Over the years seroprevalence has been changing with increasing tendency. The highest seroprevalence in rams was in 2018, when the largest number of samples was examined. In bucks, the highest number of positive samples was found in 2015. From 2014 until 2018, the overall seroprevalence in rams and bucks has increased significantly. From the study results it can be seen that annual monitoring program is very important and has to be held in the future in order to have the disease under control. The program helps in rising the awareness and knowledge of the owners about SRLV and the importance of breeding seronegative animals.