Small Ruminant Lentivirus Infection Research Articles

Investigation, management and control of a maedi outbreak in Norway in 2019-2020

BackgroundVisna-maedi is a notifiable disease in Norway, and eliminating the disease is a national goal. The import of sheep into Norway is very limited, and strict regulations apply to the movement of small ruminants between flocks and within defined geographical regions. Several outbreaks have occurred in the last 50 years, and the most recent before 2019 occurred in Trøndelag county in Central Norway in 2002. A national surveillance programme for small ruminant lentivirus infection exists since 2003.ResultsIn 2019, the national surveillance programme detected seropositive animals for small ruminant lentivirus in a sheep flock in Trøndelag. Based on the result of polymerase chain reaction analysis and histopathological findings, the Norwegian Food Safety Authority concluded the diagnosis of maedi. Further investigations detected maedi in eight additional sheep flocks in the same county. The flocks were placed under restrictions, and the authorities also imposed restrictions on 82 contact flocks. Sequencing of partial gag genes indicated that the virus in the current outbreak was related to the small ruminant lentivirus detected in the same area between 2002 and 2005.ConclusionsThe outbreak investigation shows the need for sensitive and specific diagnostic methods, and an improved and more targeted surveillance strategy. It also demonstrates the risk of disease spreading between flocks through animal movements, and highlights the importance of biosecurity and structured livestock trade. In addition to allowing livestock trade only from flocks documented free from maedi, it may be necessary to monitor sheep flocks over many years, when aiming to eliminate maedi from the Norwegian sheep population.

Circulation of small ruminant lentivirus in endangered goat and sheep breeds of Southern Italy

According to the Domestic Animal Diversity Information System (DAD-IS) of the FAO, Italy has one of the largest numbers of local small ruminant breeds among European countries. In Southern Italy, namely the Campania Region, Bagnolese and Laticauda sheep breeds and Cilentana goat breeds are considered endangered according to the DAD-IS. Conservation of endangered animal breeds is a goal of the European Union (EU). However, the role of infectious diseases as risk factors for endangered breeds has rarely been considered. Small ruminant lentiviruses (SRLV) infect sheep and goats, causing slow-progressive, persistent, and debilitating diseases that can lead to animal death and productivity loss. In this study, we investigated the presence of SRLV in Bagnolese, Laticauda, and Cilentana breeds using a commercial ELISA in parallel with an in-house ELISA. The results of the two tests were in good agreement (Cohen Kappa 0.84, 95 % CI = 0.76–0.93). Discrepancies between the two tests were resolved using western blotting. In total, 430 samples were tested (248 Bagnolese, 125 Laticauda, and 57 Cilentana). The apparent prevalence rates were 12.5 %, 6.4 %, and 1.7 % in Bagnolese, Laticauda, and Cilentana, respectively. In the molecular analysis of 11 proviral partial sequences, subtypes B2 and A24 were identified in two Bagnolese herds. Owing to the beneficial role of sheep and goat breeding in marginal areas, it is important to screen the entire population and implement control/eradication of SRLV infections in conjunction with each conservation program.

Development of in-house ELISA based on recombinant gag proteins of small ruminant lentiviruses isolated from goats in Thailand

Small ruminant lentiviruses (SRLVs), are grouped in Retroviridae family, remain a significant loss in the small ruminant husbandry. As a result of unavailability of vaccine and effective treatment, the diagnosis plays a crucial role for the control of SRLV infection. However, the major challenge of diagnosis of SRLV infection is the genetic and antigenic variability of the viruses that can lead to a failure in serological detection. This study investigated the circulating strains of the viruses in goats in Thailand and an in-house ELISA was developed. The coding sequences for gag protein were optimized, synthesized, and expressed in Escherichia coli for increasing the sensitivity of ELISA test. A total of 365 serum samples were examined against the recombinant protein in an in-house ELISA. The results showed that the recombinant gag achieves 96.67% sensitivity and 93.18% specificity as compared with the commercially available ELISA test kit.

SEROPREVALENCE OF SMALL RUMINANT LENTIVIRUS INFECTION IN A GOAT FLOCK IN EASTERN ROMANIA

Small ruminant lentiviruses (SRLVs) pose significant economic challenges to goat farming and have a detrimental impact on animal welfare. The objectives of this study were to deepen our comprehension of SRLV infections and their implications for small ruminant farming. Within the studied herd, the detected seroprevalence of SRLV was notably high at 91.92% (95.0% CI: 86.5%–97.3%). This finding strongly suggests the enduring presence of SRLV infection within the goat farm, spanning multiple years. Antibodies against SRLVs were detected across all selected age categories and breeds, irrespective of the presence or absence of clinical signs. The data gleaned from this study allow significant implications, raising concerns about the potential for future clinical outbreaks resulting from SRLV infections in eastern Romanian goat herds. Given these findings, the imperative for the continuous surveillance of SRLV infections becomes evident. Ongoing vigilance and monitoring are essential to mitigate the risk of disease transmission, minimise economic losses and safeguard the welfare of goats within the region.

Serological evidence of Maedi-Visna and Caprine Arthritis Encephalitis in sheep and goats in the Korça region in Albania

Lentiviruses infect small ruminants and cause similar but different two significant diseases: Maedi-Visna in sheep and Caprine Arthritis Encephalitis in goats. In the current study, 91 of 413 adult sheep and goats from the Korça region tested positive for small ruminant lentiviruses. Furthermore, 11 of the 25 small ruminant herds have at least one positive animal for small ruminant lentiviruses. The overall observed herd prevalence was 44.0% (95% CI: 29–59) for both diseases, 38.6% (95% CI: 18.6-55.1) for Maedi-Visna in sheep, and 66.7% (95% CI: 43.1-90.2) for Caprine Arthritis Encephalitis in goats. The average observed prevalence rate ranges from 20% to 82.9% (95% CI: 12–89.2) within positive goat’s herds, while within sheep-positive herds, it varies from 23.1% to 57.1% (95% CI: 11.7–70.4). There was a positive correlation between seroprevalence rate and animal species; goats seem to have an odd 2.36 (OR 95% CI: 1.48-3.76) higher than sheep to test positive in ELISA. Other risk factors, such as farm size, indoor versus outdoor rearing, and close farm biosecurity, may play a role in disease transmission between and within small ruminant animals’ herds. This is the first study on the prevalence of Maedi-Visna infection in sheep and one of the few published Caprine Arthritis Encephalitis studies in Albania. These findings support the presence of Small Ruminant Lentiviruses (SRLV) in the Korça district emphasize the need for monitoring and controlling SRLV infection in sheep and goats. According to the study’s conclusions, a yearly monitoring program is essential and must be developed in the future to keep the disease under control. This initiative aims to help owners understand SRLV and the need to raise seronegative animals

The genetic variability of small-ruminant lentiviruses and its impact on tropism, the development of diagnostic tests and vaccines and the effectiveness of control programmes.

Maedi-visna virus and caprine arthritis encephalitis virus are two closely related lentiviruses which cause multisystemic, progressive and persistent infection in goats and sheep. Because these viruses frequently cross the species barrier, they are considered to be one genetic group called small-ruminant lentiviruses (SRLV). They have in vivo tropism mainly for monocytes and macrophages and organ tropism with unknown mechanisms. Typical clinical signs are pneumonia in sheep, arthritis in goats, and mastitis in both species. Infection with SRLV cannot currently be treated or prevented, and control programmes are the only approaches to avoiding its spread. These programmes rely mainly on annual serological testing and elimination of positive animals. However, the high genetic and antigenic variability of SRLV complicate their early and definitive diagnosis. The objective of this review is to summarise the current knowledge of SRLV genetic variation and its implications for tropism, the development of diagnostic tests and vaccines and the effectiveness of control and eradication programmes. Subject literature was selected from the PubMed and the Google Scholar databases. The high genetic diversity of SRLV affects the performance of diagnostic tools and therefore control programmes. For the early and definitive diagnosis of SRLV infection, a combination of serological and molecular tests is suggested. Testing by PCR can also be considered for sub-yearling animals. There are still significant gaps in our knowledge of the epidemiology, immunology and biology of SRLV and their impact on animal production and welfare. This information may aid selection of the most effective SRLV spread reduction measures.

Epizootiological serosurvey on small ruminant lentiviruses: Prevalence, age and breed effects

AbstractIn this study, the prevalence of small ruminant lentivirus, i.e. Maedi-Visna and caprine arthritis encephalitis virus infections in sheep and goat populations were investigated through epizootiological serosurveillance in the Aegean region located in western Türkiye in 2018. A total of 1,840 serum samples (595 goats, 1,245 sheep) were collected from 92 villages in the region and examined by indirect ELISA. Thirty-nine goat and 304 sheep sera were found positive for small ruminant lentivirus antibodies. The prevalence was 24.42% in sheep and 6.55% in goats. An average of 18.64% was found in small ruminants in the Aegean region. The prevalence of small ruminant lentiviruses was found to be higher in Pirlak and Pirlak hybrid sheep and in Saanen and Saanen hybrid goats (P < 0.05). The prevalence was found to increase with age, as it was higher in animals older than 48 months than in the age groups of 0–24 or 25–48 months (P < 0.05). Moreover, the small ruminant lentivirus prevalence was higher in sheep than in goats (P < 0.0001). With the epizootiological approach, this study is expected to contribute to the control and prevention of small ruminant lentivirus infections.

Perfil das metaloproteínas de matriz extracelular em cabras Toggenburg sadias e infectadas por lentivírus de pequenos ruminantes no Sudeste brasileiro

Small ruminant lentiviruses (SRLV) are difficult to diagnose due to their escape mechanisms. Therefore, proteomics is an alternative in the search for biomarkers through extracellular matrix metalloproteinases (MMPs), enzymes related to the immune response. In this sense, this study aimed to analyze the profile of MMPs in healthy and infected Toggenburg goats with chronic SRLV infection in Southeast Brazil. Five positive and five negative goats for SRLV were selected using the agar gel immunodiffusion (AGID) microtechnique, western blot (WB), and nested polymerase chain reaction (nPCR). All animals were submitted to blood collection by puncture of the jugular vein, followed by centrifugation to obtain blood plasma, protein quantification by the Bradford method, one-dimensional electrophoretic separation (1D), and identification of protease activity by zymography and confirmation via reverse zymography in the presence of MMP-2 through the action of tissue inhibitors (TIMP-2). The analysis of protein bands was performed using descriptive statistics and densitometry values for zymography were subjected to the Shapiro-Wilk test to determine normality. Little difference was observed in the occurrence of protein bands between groups. Regarding MMPs, no differences were observed in the expression of proMMP-9, MMP-9, and MMP-2 in animals affected by SRLV. TIMP-2 inhibited proMMP-2 and MMP-2 in all animals. Thus, the profile of protein bands does not change in healthy goats with chronic SRLV infection. The TIMP-2 expression allowed proving the existence of MMP-2 in animals chronically infected by SRLV via reverse zymography.

Small Ruminant Lentivirus Infection in Sheep and Goats in North Portugal: Seroprevalence and Risk Factors.

Small ruminant lentiviruses (SRLVs) are transmitted among ovine and caprine species. This disease is a severe problem for small ruminant production, not only for animals' well-being but also for flocks' efficiency. The main aim of this research was to quantify the seroprevalence and associated risk factors for SRLV infection in the northern region of Portugal. Samples were collected from a total of 150 flocks, of which 129 (86.0%; 95% CI: 80.67%-91.33%) had at least one seropositive animal. Out of 2607 individual blood samples, 1074 (41.2%) were positive for SRLVs. Risk factors associated with SRLV infection were species (caprine), age (>2 years old), flock size (>100 animals), production system (intensive), food production system (milk), type of activity (professional), participation in livestock competitions (yes), replacement young ewe bought (yes), and natural feeding management (yes). This knowledge empowers the implementation of effective preventive measures. Overall, biosecurity measures should be promoted and implemented with the main aim of reducing viral transmission and reducing the prevalence of this disease. We recognise that government authorities should promote and audit voluntary control and eradication programs in small ruminant flocks in the region studied.

Outbreak of Acute Clinical Mastitis in Primigravidae Ewes in the Immediately Pre-Partum Period

An outbreak of acute mastitis was investigated in a dairy sheep farm in Central Greece with a prevalence of 8.2%. Two animals were examined with symptoms of hyperacute inflammation in one of the two mammary glands. Affected glands presented swollen to grossly enlarged, warm and painful. In both animals, haematological examination revealed mild anaemia, increased leucocyte counts with mature neutropaenia and left shift, and marked thrombocytosis. Bacteriological examinations of mammary gland secretion yielded heavy growth of Streptococcus dysgalactiae and Escherichia coli from each of the two animals, respectively. Serological examination revealed a high percentage of positive samples for small ruminant lentivirus infection in both animals. The somatic cell count in the bulk-tank milk was 0.65 × 106 cells/mL. The housing conditions were inadequate with high levels of ammonia, intense stocking and muddy bedding. This pathological condition in nulliparous ewes was attributed to the extensive oedema of mammary gland and teat, the relaxation of immunity during the peri-parturient period and the heavily contaminated environment. These findings are in general agreement with corresponding incidents in heifers. Following our instructions for improving housing conditions, no other similar incidents were recorded.

A large-scale study on the seroprevalence of small ruminant lentiviral infection in the Polish goat population

A large-scale study was carried out in a Polish goat population in 2014-2022 to determine the herd-level (between-herd) and within-herd seroprevalence of small ruminant lentivirus (SRLV) infection. A total of 8354 adult goats (aged >1 year) from 165 herds located in various regions of Poland were serologically tested using a commercial ELISA. One hundred twenty eight herds were randomly selected while 37 were enrolled based on convenience non-random sampling. At least 1 seropositive result was obtained in 103 / 165 herds. For all these herds the probability that they were truly positive (herd-level positive predictive value) was calculated. It was ≥90% in 91 seropositive herds and 73% to <90% in 12 herds in which only 1-4 goats were seropositive (22 goats in total). The seropositive goats in the latter herds were retested using a different commercial ELISA and 14 goats (9 males and 5 females) from 9 herds were confirmed to be seropositive (serial testing). The true herd-level seroprevalence was estimated at 61% (95% confidence interval [CI 95%]: 53%-68%). It differed significantly between herd size classes (p=0.003): the highest prevalences were found in the medium (51 - 100 adult goats) and large herds (>100 adult goats) - 72% (CI 95%: 56-84%) and 86% (CI 95%: 67%-95%), respectively, while prevalences in very small (≤20 adult goats) and small herds (21 - 50 adult goats) were 46% (CI 95%: 34%-59%) and 57% (CI 95%: 43%-70%), respectively. The true herd-level seroprevalence differed significantly also between geographical regions of Poland (p=0.003), with the highest values in the north-western and the lowest in the southern region of the country. The true within-herd seroprevalence estimated using a Bayesian approach ranged from 0.7% to 100% with the median (IQR) of 42% (17%-84%), and did not vary significantly between herd size classes (p=0.393) or geographical regions of Poland (p=0.570). Concluding, SRLV infection is widespread in the Polish goat population, the north-western region of Poland is most extensively infected, and herds counting >50 adult goats are more often infected.

Immune response dynamics of recent and chronic small ruminant lentivirus infection in the male reproductive system

The objective of this study was to analyze the immune responses of bucks to small ruminant lentivirus (SRLV) with a focus on the reproductive system of males with recent and chronic infection. A total of 12 bucks were selected, six seronegative and six seropositive with chronic natural infection for more than 18 months (chronic infection group). After selecting the animals, the six seronegative males were intravenously inoculated with caprine arthritis-encephalitis virus (CAEV)-Co viral strain at a titer of 10-5,6 TCID50/mL. After viral inoculation, this group was called the recent infection group and was monitored weekly with the chronically infected group for 180 days with blood serum and seminal plasma Western Blot (WB) analysis. Of the animals with chronic SRLV infection, 18.94% (50/264) showed anti-SRLV antibodies in at least one of the samples, and 81.06% (214/264) were negative. Anti-SRLV antibodies were detected in 27.27% (36/132) of the blood serum samples from this group, while 10.60% (14/132) were reactive in the seminal plasma WB test. The animals inoculated with CAEV-Co became seropositive after the third week of viral inoculation. In this group, 31.06% (41/132) of seminal plasma samples had anti-SRLV antibodies, and of these, 70.73% (29/41) coincided with blood serum results. Of the remaining 29.27% (12/41), the seminal plasma sample of only three animals (RIA2, RIA3, and RIA5) had anti-SRLV antibodies. One of the animals with a recent infection presented anti-SRLV antibodies only in seminal plasma samples, possibly due to virus compartmentalization. Intermittent viral shedding was observed in both biological samples, regardless of the infection stage. The immune response in bucks with recent SRLV infection is more significant than in chronically infected animals. Regardless of the stage of infection, there is a fluctuation in antibody levels, therefore, this creates a risk of false-negative samples when performing the diagnosis.

P-060 Imaging examination in Small Ruminant Lentivirus Infection

P-060 Imaging examination in Small Ruminant Lentivirus Infection

O-129 Occurrence and risk factors associated with small ruminant lentivirus infection in goat and sheep herds

O-129 Occurrence and risk factors associated with small ruminant lentivirus infection in goat and sheep herds

O-115 A new approach to the diagnostics of small ruminant lentivirus infection?

O-115 A new approach to the diagnostics of small ruminant lentivirus infection?

Associations between small ruminant lentivirus infection and total milk yield and somatic cell count in a dairy sheep flock.

Small ruminant lentiviruses (SRLVs) are lentiviruses of sheep and goats, formerly known as maedi-visna (MV) in sheep and caprine encephalitis and arthritis in goats. In sheep, SRLVs commonly cause progressive pneumonia, wasting and indurative mastitis. SRLVs have a long latent period, and chronic production losses are often not recognised until very late. Few studies quantifying the production losses in ewes have been published, and none have been published under UK flock husbandry conditions. Production records of milk yield and somatic cell count (SCC) from a dairy flock of 319 milking East Friesian × Lacaune ewes identified as MV infected via routine serological screening for SRLV antibodies were used in multivariable linear regression modelling to estimate the impact of SRLV status on total milk yield and SCC. Milk yield was reduced in seropositive ewes by 8.1%-9.2%over an entire lactation. SCC counts were not significantly different in SRLV-infected andunifectedanimals. Further parameters, such as body condition score or clinical mastitis, that were not available may have clarified the underlying cause of milk yield drop. The study demonstrates substantial production losses in anSRLV-affected flock and highlightsthe impact of the virus on afarm'seconomic viability.

Serological testing of an equal-volume milk sample – a new method to estimate the seroprevalence of small ruminant lentivirus infection?

BackgroundIn cattle attempts to evaluate within-herd prevalence of various infectious and parasitic diseases by bulk-tank milk (BTM) testing with ELISA have been made with moderate success. The fact that BTM is composed of variable and unknown volumes of milk from individual lactating animals weakens the relationship between numerical result of the ELISA and the within-herd prevalence. We carried out a laboratory experimental study to evaluate if a pooled milk sample created by mixing an equal volume of individual milk samples from seropositive and seronegative goats, henceforth referred to as an equal-volume milk sample (EVMS), would allow for accurate estimation of within-herd seroprevalence of caprine arthritis-encephalitis (CAE) using 3 different commercial ELISAs. By mixing randomly selected milk samples from seronegative and seropositive goats, 193 EVMS were created – 93 made of seronegative samples and 100 with the proportion of seropositive individual milk samples (EVMS%POS) ranging from 1 to 100%. EVMS%POS could be considered as a proxy for the within-herd seroprevalence. Then, OD of EVMS (ODEVMS) of the 193 EVMS was measured using 3 commercial ELISAs for CAE – 2 indirect and 1 competitive.ResultsThe cut-off values of ODEVMS indicating SRLV infection were determined. The regression functions were developed to link ODEVMS with EVMS%POS. A significant monotonic relationship between ODEVMS measured with 2 commercial indirect ELISAs and EVMS%POS was identified. Two regression models developed on this basis described approximately 90% of variability and allowed to estimate EVMS%POS, when it was below 50%. High ODEVMS indicated EVMS%POS of > 50%.ConclusionOur study introduces the concept of serological testing of EVMS as a method of detecting SRLV-infected herds and estimating the proportion of strongly seropositive goats. Further field studies are warranted to assess practical benefits of EVMS serological testing.

Investigation of the Epidemiology of Small Ruminant Lentivirus Infections southeast part of the Marmara region of Turkey

Small ruminant lentiviruses (SRLVs) are viral pathogens that are common in goats and sheep, affect production, and cause significant economic losses in small ruminant breeding. Caprine arthritis encephalitis virus (CAEV) and Maedi-Visna virus (MVV) are prototypes of SRLVs. Both of them affect animal health and welfare in sheep and goats and cause progressive and persistent infections in the small ruminant industry. The present study aimed to reveal the epidemiological status of lentivirus infection in the sheep region in Yalova province located in the southeast part of the Marmara region and determine the circulating genotypes by conducting the sequence analysis of the samples detected positive by a molecular method and molecular characterization of the detected field strains. To that end, 231 sheep blood samples were used between May 2016 and April 2018. Based on sampling results of the PCR test and ELISA tests, 5.62% (13/231) and 5.19% (12/231) positivity rates were found in sheep, respectively. According to the ELISA test results, a significant difference was found in terms of age groups (6 months -1 age, 1-3 age, &gt;3 age) (χ2: 6.01; p=0.04). Furthermore, the sequence analysis of the gag gene region detected the existence of the A genotype of small ruminant lentiviruses in sheep. The data obtained from the study revealed a low seroprevalence course of SRLV infection in the study area in the absence of a systematic disease control program.

Lentivirus Susceptibility in Brazilian and US Sheep with TMEM154 Mutations.

Small ruminant lentiviruses (SRLVs) affect sheep and goats worldwide. The major gene related to SRLV infections is the Transmembrane Protein Gene 154 (TMEM154). We estimated the haplotype frequencies of TMEM154 in the USA (USDA-ARS) and Brazil (Embrapa) Gene Banks by using two different SNP genotyping methodologies, FluidigmTM and KASPTM. We also genotyped the ZNF389_ss748775100 deletion variant in Brazilian flocks. A total of 1040 blood samples and 112 semen samples from 15 Brazilian breeds were genotyped with Fluidigm for the SNP ZNF389_ss748775100 and 12 TMEM154 SNPs. A total of 484 blood samples from the Santa Inês breed and 188 semen samples from 14 North American sheep breeds were genotyped with KASP for 6 TMEM154 SNPs. All the Brazilian samples had the "I/I" genotype for the ZNF389_ss748775100 mutation. There were 25 TMEM154 haplotypes distributed across the Brazilian breeds, and 4 haplotypes in the US breeds. Haplotypes associated with susceptibility were present in almost all breeds, which suggests that genetic testing can help to improve herd health and productivity by selecting non-susceptible animals as founders of the next generations. Fluidigm and KASP are reliable assays when compared with Beadchip arrays. Further studies are necessary to understand the unknown role of TMEM154 mutations, host-pathogen interaction and new genes associated with the clinical condition.

Factors associated with small ruminant lentivirus infection in goat herds from Pernambuco state, Northeast region of Brazil

Serum samples (n = 1532) were collected between May 2011 to April 2012 from goats from 76 herds (49 from dairy farms and 27 herds for genetic improvement) from three geographical regions from the state of Pernambuco, Brazil: Zona da Mata, Agreste, and Sertão. Samples were processed using agar gel immunodiffusion test, with p28 CAEV antigen. The objective was to determine the risk factors for small ruminant lentivirus (SRLV) in dairy goats and goats with high genetic value. Overall, seroprevalence was 13.7% (210/1532) [95% CI: 12–15.4%] in animals and 67.1% (51/76) [95% CI: 56.5%− 77.7%] in herds. In dairy farms the seroprevalence was 73.5% (36/49) [95% CI: 61.1%− 85.8%], and in properties with animals of high genetic value it was 55.6% (15/27) [95% CI: 36.8%− 74.3%]. Robust Poisson regression analysis adjusted by the random effect of the herd showed that risk factors were: importing bucks from another Brazilian state (prevalence ratio [PR] = 4.73 [95% CI: 2.05; 10.88]), not isolating sick animals (PR = 3.27 [95% CI: 2.24; 4.76]), and participating in fairs/animal crowding (PR = 1.52 [95% CI: 1.09; 2.11]). Prevalence results show that SRLV is present in caprine herds in the state of Pernambuco and identified risk factors are strongly related to animal transit. Considering the epidemiological situation, the first step for mitigating the consequences of this disease would be controlling animal transit.