Interspecific transmission of small ruminant lentiviruses from goats to sheep

In vivo evaluation of the antiretroviral activity of Melia azedarach against small ruminant lentiviruses in goat colostrum and milk

This study aimed to evaluate in vivo the use of the extract from the leaves of Melia azedarach in the ethyl acetate fraction at a concentration of 150 µg/mL as an antiretroviral treatment against small ruminant lentiviruses (SRLV) in goat colostrum, and milk with a 90-min action. Two groups of six kids were treated with the extract. One group received three supplies of colostrum from does naturally positive for SRLV, treated with the ethyl acetate fraction of M. azedarach (EAF-MA) for three days, while the other group consumed milk from does also carrying the virus with the respective extract twice a day for five days. After undergoing treatment, all animals began to receive thermized milk until weaning (60 days) and were monitored for six months using nested polymerase chain reaction (nPCR) and western blot (WB) tests. The study revealed cumulative percentages of positive animals in WB or nPCR in the milk group of 66.66% on the seventh day, 83.33% in the following week, and 100% at 120 days, while the colostrum group showed values of 66.66% at 14 days, 83.33% at 90 days, and 100% at 120 days. Variation and intermittency were observed in viral detection, but all animals tested positive in WB or nPCR at some point. A potential delay in infection was observed, which was more significant in the colostrum group. The need for the combination of serological and molecular tests for a more efficient detection of the disease is also emphasized.

Caprine arthritis and encephalitis virus infection in goats of Bangladesh: Serological detection and its associated risk factors

Background and Aim

Caprine arthritis and encephalitis (CAE) is a multisystemic persistent viral disease of goat that causes significant economic losses to the farmers and livestock sector. However, no information in this country is available regarding CAE virus (CAEV) infection. Therefore, this study aimed to estimate the seroprevalence of CAEV infection among the goat population in the selected goat-prone districts in Bangladesh and to identify the associated risk factors of the disease.

Materials and Methods

From July 2021 to June 2022, 446 goat serum samples were randomly collected from the study area. Goat owners were interviewed using a pretested questionnaire to determine the risk factors. A commercial indirect enzyme-linked immunosorbent assay kit was used to screen blood serum for CAEV antibodies. Logistic regression models were used to analyze risk factors and serological data to identify the potential risk factors.

Results

Out of 446 serum samples, 19 samples were seropositive against CAEV. The overall seroprevalence was 4.26% (95% confidence interval [CI]: 2.58-6.57). The multivariable logistic regression model identified sex (Female; odds ratio [OR]: 3.98; 95% CI: 1.13-13.95), animal age (12-48 months; OR: 4.93, 95% CI: 0.63-38.13), and biosecurity status (Poor biosecurity; OR: 1.66, 95% CI: 0.46-5.92) as potential risk factors for CAEV seropositivity.

Conclusion

This study revealed the serological detection of CAEV in Bangladeshi goats where seroprevalence is found to be relatively low. To eradicate the disease, screening and culling of infected goats from the herd might be implemented.

Longitudinal Study on Seroreactivity of Goats Exposed to Colostrum and Milk of Small Ruminant Lentivirus-infected Dams

Introduction

Small ruminant lentivirus (SRLV) causes caprine arthritis-encephalitis in goats and maedi-visna disease in sheep. Transmission is via ingestion of colostrum and milk from infected dams or long-term direct contact between animals. Lifelong seroconversion can occur several weeks after infection via ingestion. However, sub-yearling lambs that ingest contaminated colostrum may be able to clear the infection and become seronegative. Whether a similar phenomenon occurs in goats remains unknown. Therefore, the serological status of goats was studied longitudinally from the moment of natural exposure to colostrum and milk of SRLV-positive dams through the age of 24 months.

Material and Methods

Between February 2014 and March 2017 a dairy goat herd was studied which had been infected with SRLV for more than 20 years and carried maedi-visna virus-like genotype A subtype A17. Thirty-one kids born to dams seropositive for SRLV for at least a year beforehand were followed. They ingested colostrum immediately after birth and then remained with their dams for three weeks. The goats were tested serologically every month using two commercial ELISAs. The clinical condition of the goats was also regularly assessed.

Results

Out of 31 goats, 13 (42%) seroconverted at the age ranging from 3 to 22 months with a median of 5 months. Two goats seroconverted in the second year of life. The other eleven did so before the age of one year; two of these reverted to seronegative status. Only 9 out of 31 goats (29%) seroconverted in the first year of life and remained seropositive. They were early and stable seroreactors to which SRLV was transmitted lactogenically. The age at which they seroconverted ranged from 3 to 10 months with a median of 5 months. In 8 of the 18 persistently seronegative goats, a single isolated positive result occurred. No goats showed any clinical signs of arthritis. The level of maternal antibodies at the age of one week did not differ significantly between the stable seroreactors and the remainder.

Conclusion

Seroconversion appears to occur in less than 50% of goats exposed to heterologous SRLV genotype A via ingestion of colostrum and milk from infected dams and is delayed by 3-10 months. The natural lactogenic route of transmission of SRLV genotype A in goats appears to be less effective than this route of genotype B transmission reported in earlier studies.

Alternative Molecular Tools for the Fight against Infectious Diseases of Small Ruminants: Native Sicilian Sheep Breeds and Maedi-Visna Genetic Susceptibility

Simple Summary

Local breeds represent a precious reservoir of genetic diversity, crucial to adapting to environmental and climate changes and reacting to evolving diseases. In Sicily, four native dairy breeds, namely Valle del Belìce, Comisana, Barbaresca, and Pinzirita, have adapted to low-input farming systems and semiarid environments, having an essential role in producing high-quality milk and typical dairy products. Maedi-visna (MV) is one of the most important chronic diseases affecting the sheep sector worldwide, causing production losses. Different target genes play an important role in immunity and in genetic resilience to MV, such as TMEM154, TLR9, MYD88, and CCR5. A major host genetic component to sheep MV susceptibility was identified in the ovine TMEM154 gene. Animals with either of TMEM154 haplotypes that encode glutamate at position 35 (E35) of the protein are at higher risk of MV infection than those homozygous with lysine at position 35 (K35). In the tested Sicilian breeds, animals carrying the allele E35 showed a greater risk of being serologically positive. Comisana, Barbaresca, and Pinzirita breeds showed a good frequency of the protective allele K35, whilst a high frequency of risk allele was found in the Valle del Belìce breed, related to the selection strategies addressed to obtain a productive dairy sheep. Our results highlight the importance of the preservation of autochthonous breeds as a reservoir of natural resistance against infectious disease.

Abstract

Maedi-visna (MV) is a disease caused by small ruminant lentiviruses. It is included in the list of notifiable terrestrial animal diseases due to economic losses and animal welfare harm in the sheep sector. To date, control programs remain the onliest approach to avoiding infection. The allelic variant p.Glu35Lys (E35K) of the TMEM154 gene has been strongly associated with host vulnerability to MV illness. The present study aimed to investigate the association of TMEM154 E35K allele frequencies with MV susceptibility in native Sicilian sheep breeds. More than 400 animals from 14 local sheep were serologically tested and genotyped for the TMEM154 E35K polymorphism. The local breeds displayed different values of MV seroprevalence, with the lowest antibody prevalence in Barbaresca and Pinzirita breeds. TMEM154 protective allele (K35) was less frequent than the risk allele (E35) in Valle del Belìce breed, whereas the other three breeds showed a more balanced alleles distribution. A positive association between seroprevalence and genotype was found in the entire sample set. The risk of infection resulted in more than 3-fold times as high in sheep with EK and EE genotype compared to the KK genotype. Our data could be helpful in establishing selection breeding programs aimed at reducing MV infection in Sicilian sheep farming and encouraging the breeding of native breeds.

A Comparison of Oxidative Stress Biomarkers in the Serum of Healthy Polish Dairy Goats with Those Naturally Infected with Small Ruminant Lentivirus in the Course of Lactation

The present study examines the effects of natural infection by small ruminant lentivirus (SRLV) in the two most common goat breeds in Poland, i.e., Polish white improved and polish fawn improved. It focuses on biomarkers of oxidative stress, oxidatively modified proteins and antioxidant defenses, ceruloplasmin level as an acute phase protein, and the activities of antioxidant enzymes in the goat serum. It was conducted on 24 goats divided into two equal groups: one SRLV-seropositive (SRLV-SP) and another SRLV-seronegative (SRLV-SN). Both groups were identical in terms of breed and parity. Despite infection, the SRLV-SP goats demonstrated no symptoms of caprine arthritis-encephalitis. In addition, the SRLV-SP goats did not reveal pronounced dysfunctions in oxidative stress biomarkers in the serum compared to the SRLV-SN animals. However, both groups demonstrated elevated levels of the aldehydic and ketonic derivatives of oxidatively modified proteins during the lactation period. In addition, both groups retained a high total antioxidant capacity in serum despite the decrease of enzyme antioxidant defenses throughout the 200-day lactation period.

Diagnostic accuracy of three commercial immunoenzymatic assays for small ruminant lentivirus infection in goats performed on individual milk samples

Caprine arthritis-encephalitis (CAE) caused by small ruminant lentivirus (SRLV) infection is one of the most widespread and devastating diseases of goats. Serological methods, mainly immunoenzymatic assays (ELISA), are the mainstay of CAE diagnostics. Even though blood is still the most commonly tested material, animal welfare issues and increasing costs of veterinary service prompt the development of serological methods based on milk testing. Several different types of ELISAs for CAE are available on the market. All of them perform well on serum, however their diagnostic accuracy for testing milk has not been so far compared. Therefore, we carried out the study in 5 dairy goat herds in Poland whose previous epidemiological situation regarding CAE was known. Paired serum and milk samples were collected from all adult females (n = 420) and tested with 3 commercial ELISAs - indirect ELISA based on the whole-virus antigen (wELISA), indirect ELISA based on the recombined transmembrane and capsid protein (TM/CA-ELISA), and competitive ELISA based on the surface glycoprotein (SU-ELISA). Milk was tested as lactoserum at dilution of 1/2 in wELISA and TM/CA-ELISA, and undiluted in SU-ELISA. The true status of goats was based on the composite reference standard comprising the results of all three ELISAs done on serum and the true prevalence of SRLV infection in the herd of origin. 243 (57.9 %) goats were classified as truly positive and 177 (42.1 %) goats as truly negative. Diagnostic accuracy was evaluated using the area under the ROC curve (AUROC) as well as sensitivity (Se) and specificity (Sp) for a range of cut-off values. AUROC was 98.8 % (CI 95 %: 97.5 %, 100 %) for wELISA, 97.9 % (CI 95 %: 96.5 %, 99.2 %) for TM/CA-ELISA, and 91.7 % (CI 95 %: 88.9 %, 94.5 %) for SU-ELISA. At the cut-off values recommended by the manufacturers both indirect ELISAs were highly sensitive (89.3 % and 91.4 %, respectively) and highly specific (98.3 % and 95.5 %, respectively), whereas SU-ELISA had only moderate Se (71.2 %) at comparably high Sp (96.6 %). Nevertheless, the optimal cut-off values were lower than those recommended by manufacturers for serum - sample-to-positive control serum ratio (S/P%) of 10 % for wELISA, S/P% of 80 % for TM/CA-ELISA, and percentage inhibition of 23 % for SU-ELISA. Concluding, the study shows that wELISA and TM/CA-ELISA may be interchangeably used for testing individual goat milk samples for SRLV infection. Diagnostic sensitivity and specificity of these ELISAs appear not to be lower on milk than on serum. SU-ELISA is considerably less sensitive on milk samples than indirect ELISAs.

Vertical transmissibility of small ruminant lentivirus

This study aimed to evaluate by means of Nested Polymerase Chain Reaction (nPCR), co-cultivation and sequencing, with genetic comparison between strains (mother/newborn), the occurrence of vertical transmission of Small Ruminant Lentiviruses (SRLV) from naturally occurring nannies infected for their offspring. For the detection of SRLV seropositive progenitors, blood was collected from 42 nannies in the final third of gestation in tubes with and without anticoagulant. The diagnostic tests used were Western Blot (WB) and nPCR. During the period of birth, the same blood collection procedure was performed on 73 newborns at zero hours of birth, with the same diagnostic tests. Seventeen blood samples from seven-day-old kids, proven positive for SRLV by nPCR, chosen at random, were subjected to coculture in goat synovial membrane (GSM) cells for 105 days. The pro-viral DNA extracted from the cell supernatant from the coculture was subjected to nPCR. For DNA sequencing from the nPCR products, nine positive samples were chosen at random, four nannies with their respective offspring, also positive. Each sample was performed in triplicate, thus generating 27 nPCR products of which only 19 were suitable for analysis. Among the 42 pregnant goats, in 50% (21/42) pro-viral DNA was detected by nPCR, while in the WB, only 7.14% (3/42) presented antibodies against SRLV. Regarding neonates, of the 73 kids, 34 (46.57%) were positive for the virus, using the nPCR technique, while in the serological test (WB), three positive animals (4.10%) were observed. The coculture of the 17 samples with a positive result in the nPCR was confirmed in viral isolation by amplification of the SRLV pro-viral DNA. When aligned, the pro-viral DNA sequences (nannies and their respective offspring) presented homology in relation to the standard strain CAEV Co. It was concluded that the transmission of SRLV through intrauterine route was potentially the source of infection in the newborn goats.

Eradication of caprine arthritis encephalitis virus in the goat population of South Tyrol, Italy: analysis of the tailing phenomenon during the 2016-2017 campaign

Since 2007, the Autonomous Province of Bolzano-South Tyrol (Italy) has carried out a compulsory eradication program against caprine arthritis encephalitis virus (CAEV) in goats. A drastic seroprevalence reduction was achieved during the initial phase (2007-2011); however, a tailing phenomenon has been observed during the latest years, hampering the achievement of the final goal. CAEV belongs to a group of lentiviruses, called small ruminant lentiviruses (SRLVs), which are antigenically related and can infect both goats and sheep. We investigated the possible link between the tailing phenomenon in goats and the role of sheep as a virus reservoir by comparing serologic results between multispecies farms (where goats and sheep coexist) and monospecies farms (goats only). Goats on multispecies farms had a higher prevalence and seroconversion rate (even if to a rather moderate extent), higher antibody titers, and a higher probability of conclusive results in the genotyping analysis, with more frequent identification of SRLV genotype A (sheep-related) infections. Sheep can serve as a SRLV reservoir, thus contributing to scattered positive tests in goats, causing the tailing phenomenon.

Phylogenetic Analysis of Belgian Small Ruminant Lentiviruses Supports Cross Species Virus Transmission and Identifies New Subtype B5 Strains

Small ruminant lentiviruses (SRLV) are a group of highly divergent viruses responsible for global and fatal infections in sheep and goats. Since the current phylogenetic classification of these viruses was proposed in 2004, it nowadays consists out of 5 genotypes and 28 subtypes. In support of our national SRLV control program, we performed the genetic characterization of SRLV strains circulating in the Belgian sheep and goat population. Fourteen sheep and 9 goat strains were sequenced in the gag-pol and pol regions using the method described by Shah. Most SRLV strains from sheep and goats belonged to prototype A1 and B1 subtypes, respectively. We, however, also found indications for cross-species transmission of SRLV strains between sheep and goats and vice versa, and identified a new subtype designated as B5. An in-depth analysis of the current SRLV phylogeny revealed that many subtypes have been defined over the years based on limited sequence information. To keep phylogeny as a useful tool, we advocate to apply more rigorous sequencing standards to ensure the correct classification of current and new emerging strains. The genetic characterization of Belgian SRLV strains will help in the development of appropriate diagnostic tools to assist the national control program.

Histopathological, serological, molecular and electron microscopy detection of Maedi-Visna infection in sheep population in the West of Iran

BACKGROUND

Maedi-Visna (MV) is a progressive lymphoproliferative viral disease that affects multiple organs of small ruminants, including sheep and goats. The disease occurs primarily in the lung tissue and causes interstitial pneumonia.

AIMS

The aim of present study was to investigate the prevalence of ovine MV infection in Iranian sheep population through macroscopic, histopathological, serological, and molecular assays, as well as transmission electron microscopy (TEM).

METHODS

Lung and blood samples of one-hundred female sheep (≤ 2 years old) referred to the Kermanshah slaughterhouse with respiratory symptoms were collected for histopathological and molecular evaluations. Corresponding serum samples were also collected for serological examination.

RESULTS

Histopathological study showed the Maedi-like pulmonary lesions in 85% of the affected lungs, which included the interstitial pneumonia, smooth muscle hypertrophy of alveolar septa and around the blood vessels, interstitial lymphoplasmacytic infiltration and lymphofollicular hyperplasia. Specific antibodies against MV virus were detected in 7% of serum samples. Long terminal repeat (LTR) region of MV provirus was amplified in three (3%) DNA samples, extracted from the suspected lungs. Sequencing analysis of polymerase chain reaction (PCR)-positive samples confirmed the presence of MV provirus in the genome. No amplification was observed, neither in the DNA samples extracted from the blood samples of suspected sheep nor the control group. Transmission electron microscopy also confirmed the presence of MV virions inside the cytoplasmic membrane of MV-infected macrophages.

CONCLUSION

Although histopathology can provide a preliminary estimation of Maedi in populations, definitive diagnosis of the disease needs to be approved by more sensitive techniques such as serological examinations and molecular analysis.

Genotyping Based on the LTR Region of Small Ruminant Lentiviruses from Naturally Infected Sheep and Goats from Mexico

Small ruminant lentiviruses (SRLVs) belong to the genus Lentivirus in the Retroviridae family. There are five genotypes (A, B, C, D, and E), where genotypes A and B have a global distribution and genotypes C, D, and E are limited to Europe. The presence of SRLV has been confirmed in Mexico, with genotype B detected in the central region of the country. We examined the presence of SRLVs and genotype prevalence in 1014 sheep and 1383 goats from 12 Mexican states. Using a commercial competitive ELISA (cELISA) test, we detected SRLV antibodies in 107 sheep (10.55%) and 466 goats (33.69%). We used an endpoint PCR to amplify the LTR region on seropositive animals. A total of 50 sheep and 75 goats tested positive via PCR. Positive amplicons from 11 sheep and 17 goats from ten Mexican States were cloned and sequenced. With the LTR sequence data obtained in this study, a phylogenetic analysis was performed; we also constructed a phylogenetic tree using the obtained sequences and GenBank's available sequences. All studied sequences were associated with genotype B, specifically with the FESC-752 isolate previously identified in Mexico. Highly conserved transcription factor binding sites were observed in analyzed alignments, such as AML (vis), AP-4, and TATA box. However, we identified nucleotide differences at site AP-1 that suggest function loss. Our study found that ovine and caprine genotype B SRLVs are widely distributed in Mexico; a highly conserved LTR region among the sequences evaluated in this study was also found.

Genotyping Based on the LTR Region of Small Ruminant Lentiviruses from Naturally Infected Sheep and Goats from Mexico

Small ruminant lentiviruses (SRLVs) belong to the genusLentivirusin the Retroviridae family. There are five genotypes (A, B, C, D, and E), where genotypes A and B have a global distribution and genotypes C, D, and E are limited to Europe. The presence of SRLV has been confirmed in Mexico, with genotype B detected in the central region of the country. We examined the presence of SRLVs and genotype prevalence in 1014 sheep and 1383 goats from 12 Mexican states. Using a commercial competitive ELISA (cELISA) test, we detected SRLV antibodies in 107 sheep (10.55%) and 466 goats (33.69%). We used an endpoint PCR to amplify the LTR region on seropositive animals. A total of 50 sheep and 75 goats tested positive via PCR. Positive amplicons from 11 sheep and 17 goats from ten Mexican States were cloned and sequenced. With the LTR sequence data obtained in this study, a phylogenetic analysis was performed; we also constructed a phylogenetic tree using the obtained sequences and GenBank’s available sequences. All studied sequences were associated with genotype B, specifically with the FESC-752 isolate previously identified in Mexico. Highly conserved transcription factor binding sites were observed in analyzed alignments, such as AML (vis), AP-4, and TATA box. However, we identified nucleotide differences at site AP-1 that suggest function loss. Our study found that ovine and caprine genotype B SRLVs are widely distributed in Mexico; a highly conserved LTR region among the sequences evaluated in this study was also found.

Sodium dodecyl sulfate as a viral inactivator and future perspectives in the control of small ruminant lentiviruses

ABSTRACT Infections by small ruminant lentiviruses (SRLVs) affect goats and sheep causing chronic multisystemic diseases that generate great economic losses. The caprine lentivirus (CLV) and the ovine lentivirus (OLV) present tropism for cells of the monocyte/macrophage lineage, which are directly associated with the main route of transmission through the ingestion of milk and colostrum from infected animals. In this manner, controlling this route is of paramount importance. Currently, researches have investigated the use of chemical additives in milk that can preserve colostrum or milk and inactivate microbiological agents. Among the compounds, sodium dodecyl sulfate (SDS) has been shown to be satisfactory in the chemical inactivation of HIV and CLV in milk, and also as a biocide in goat colostrum.

Comparative Analysis of Different Serological and Molecular Tests for the Detection of Small Ruminant Lentiviruses (SRLVs) in Belgian Sheep and Goats

Countries rely on good diagnostic tests and appropriate testing schemes to fight against economically important small ruminant lentivirus (SRLV) infections. We undertook an extensive comparative analysis of seven commercially available serological tests and one in-house real-time PCR (qPCR) detecting genotype A and B strains using a large panel of representative Belgian field samples and samples from experimentally infected sheep and goats. ELISAs generally performed well and detected seroconversion within three weeks post experimental infection. Two enzyme-linked immunosorbent assays (ELISAs) (Elitest and IDscreen^® kits) showed the highest sensitivities (>96%) and specificities (>95%) in both species, and their combined use allowed to correctly identify the infection status of all animals. Individual agar gel immunodiffusion (AGIDs) kits lacked sensitivity, but interestingly, the combined use of both kits had a sensitivity and specificity of 100%. qPCRs detected SRLV infection before seroconversion at two weeks post infection and showed a specificity of 100%. Sensitivity however remained suboptimal at 85%. These results allow to propose a faster and cheaper diagnostic testing strategy for Belgium by combining a first ELISA screening, followed by confirmation of positive samples in AGID and/or a second ELISA. Since genotypes A and B strains are predominant in many countries, these results are interesting for other countries implementing SRLV control programs.

In vitro and in vivo evaluation of sodium dodecyl sulfate (SDS) as an inactivator of caprine lentivirus (CLV) in colostrum and milk

ABSTRACT The aim of this study was to evaluate in vitro and in vivo the effect of sodium dodecyl sulfate (SDS) on the caprine lentivirus (CLV) in colostrum and milk. This was performed to develop a practical and efficient method of blocking the lactogenic transmission of the virus. In the in vitro experiment, colostrum and milk were treated with 0.25%; 0.50% and 1% SDS. Then, somatic cells of colostrum and milk were submitted to co-culture with caprine synovial membrane cells (CSM). In the in vivo test, goats were fed with colostrum and milk provided from CLV-positive goats treated with SDS in the same concentrations used in the in vitro experiment. Animals were tested by nested polymerase chain reaction (nPCR) and Western blot (WB) assays. In the in vitro experiment, inhibitory activity against CLV without inactivation occurred in colostrum with all SDS concentrations. However, concentrations of 0.25 and 0.5% SDS presented only inhibitory activity against CLV in milk cells, and 1% concentration provided inactivation of the virus. In the in vivo tests, none of the three concentrations of SDS was effective in inactivating LVC in colostrum or goat milk, which was confirmed by seroconversion and presence of proviral DNA in animals afterwards.

Sheep infection by caprine lentivirus

SUMMARY The objective of this study was to demonstrate iatrogenic transmission of small ruminant lentivirus (SRLV) from goats to sheep and horizontal transmission between sheep. The study was conducted on a farm with separate goat and sheep rearing, and animals were monitored for lentivirus occurrence by clinical examination and testing by immunoblotting (IB), agar gel immunodiffusion (AGID), and nested polymerase chain reaction (nPCR). Positive results had not been observed in the sheep flock until this study. Conversely, virus positive dairy goats were known. For this reason, the farm performed the caprine arthritis-encephalitis (CAE) control program. The study was designed with a sheep group that presented positive animals for SRLV by nPCR. It was verified that three newborn animals in this group were rejected by their mothers and consequently received milk from the goat herd. These three animals remained with another 20 sheep of the same age, totaling 23 animals. After one year, during monitoring, 11 of the 23 animals in the group presented positive results in the nPCR and three demonstrated seroconversion by IB. Of the animals that had received goat milk, two had positive results in the nPCR and IB. The 11 animals positive in the nPCR were followed and it was verified that five animals did not present further positive results in the nPCR, nor seroconversion; two continued presenting positive results in the nPCR but were negative in the IB and AGID and four were positive in the nPCR, IB, and AGID. Thus, it was possible to demonstrate iatrogenic interspecific infection and the occurrence of horizontal caprine lentivirus transmission among sheep.

Serum epidemiological survey and risk factors investigation for lentivirus in goats from Sisal Region, Bahia, Brazil

ABSTRACT: This study aimed to carry out a serum epidemiological survey of goat arthritis encephalitis in the sisal region of Bahia, Brazil, and to evaluate risk factors. We evaluated 831 samples of goat blood serum among males and females older than six months, from 49 farms distributed among the municipalities of Araci, Cansanção, Conceição do Coité, Itiúba, Monte Santo, Nordestina, Queimadas, Santa Luz, São Domingos and Valente. An epidemiological questionnaire for the analysis of possible risk factors was applied. All sera were tested for immune-agar gel. The seroprevalence obtained in surveyed herds was 1.56% (13/831). There was significant difference (p<0.05) for animal racial pattern, type of farming and breeding systems. However, when considering herds with predominantly dairy breeds (Saanen and Alpine Pardo), the seropositivity in animals from Valente, Conceição do Coité and São Domingos amounted to 5.06% (12/237). In these municipalities, from 14 properties analyzed, five (38.5%) had at least one positive-testing animal. This result is extremely worrying when one considers that few control measures are adopted by farmers to prevent the goat arthritis encephalitis in the most important dairy region of Bahia state.

Maedi-Visna virus: current perspectives

Maedi-Visna virus (MVV) and caprine arthritis-encephalitis virus are commonly known as small ruminant lentiviruses (SRLVs) due to their genetic, structural, and pathogenic similarities. They produce lifelong lasting infections in their hosts, which are characterized by slow progression till overt disease happens. There are four major clinical forms derived from a chronic inflammatory response due to the constant low grade production of viruses from monocyte-derived macrophages: respiratory (caused by interstitial pneumonia), mammary (which may produce a decrease in milk production due to subclinical mastitis), joint (characterized by lameness), and neurological (characterized by chronic nonpurulent meningoencephalomyelitis). There are three levels which try to eliminate the virus: cellular, body, and the flock level. However, SRLVs have ways to counteract these defenses. This review examines some of them.

Seroprevalence of small ruminant caprine arthritis encephalitis lentivirus among goats from selected small ruminant farms in Selangor, Malaysia

Background and Aim:

Caprine arthritis encephalitis (CAE) is an important viral disease of small ruminants particularly in dairy goats with severe social and economic implication. Hence, this study was designed to determine the seroprevalence of CAE virus (CAEV) among goat population in selected small ruminant farms in Selangor and the risk factors associated with the occurrence of the disease.

Materials and Methods:

Blood samples were collected from a total of 91 goats selected at random. Blood serum was harvested and used for competitive enzyme-linked immunosorbent assay test to detect antibodies against CAE virus.

Results:

The result obtained showed that 8/91 (8.8%) of the goats were seropositive for CAEV. In addition, biosecurity management, source of origin and sex of the animal were observed to be important risk factors associated with the occurrence of CAE in goats.

Conclusion:

The findings of this study affirmed that the seroprevalence of CAEV infection among goat population in small ruminant farms in Selangor, Malaysia, is low. However, there is need to institute strict control measures such as testing and culling positive animals or separation of infected animals from those that tested negative to the disease for effective eradication of the disease.

Achievements of an eradication programme against caprine arthritis encephalitis virus in South Tyrol, Italy

Small ruminant lentivirus infections in goats affect both production and animal welfare. This represents a threat to the qualitative and quantitative growth of goat farming, recently observed in mountainous regions such as the Autonomous Province of Bolzano – South Tyrol (Italy). To monitor and eradicate the caprine arthritis encephalitis virus in this goat population, a compulsory eradication campaign was launched, based on a strict census of small ruminants and yearly serological testing of all animals, followed by the consequent culling of seropositive individuals. The campaign succeeded in completely eliminating cases of clinical disease in goats, while drastically reducing the seroprevalence at the herd as well as individual animal level. The serological outcome of the introduced control measures was determined using commercially available ELISA kits, demonstrating their suitability for use in this type of campaign, aimed at reducing seroprevalence as well as clinical manifestations of these infections. However, this clear success is diminished by the failure to achieve a complete eradication of these viruses. The reasons leading to the observed tailing phenomenon and the occurrence of new infections in already sanitised flocks are discussed and implementation of further measures are proposed.

Caprine lentivirus in sheep milk and semen

ABSTRACT With the objective of detecting the presence of caprine lentivirus (CLV) in ewe milk and in ram semen, ten matrixes and four reproducers experimentally infected with CLV were used. Samples of ewe milk were collected during the four months of lactation, five collections per animal, totaling 50 samples. Regarding the rams, eight semen collections were made per animal, during one year of experimentation, totaling 32 samples. The milk and semen samples were submitted to DNA extraction and the nested polymerase chain reaction test (nPCR) to detect CLV proviral DNA. Eight (16%) of the milk samples were positive in nPCR originating from two ewes. Only one (3.12%) semen sample was positive. The amplification products were sequenced, and were confirmed to be a CLV genomic sequence. Thus, the presence of CLV proviral DNA in sheep milk and semen was demonstrated, confirming the feasibility of infection between species, and alerting to the risk of spreading infections.