Non-vaccinated Sheep Research Articles

Seroprevalence and Identification of Brucella melitensis Based on a Glycosyltransferase Gene among Ruminants in Rafha, Saudi Arabia

Brucellosis is a zoonotic disease with veterinary, public health, and economic implications. The study aimed to estimate the seroprevalence of Brucella spp. among ruminants in Rafha, Saudi Arabia during January to October 2022 and to identify camel strains based on a glycosyltransferase gene sequence. Sera (n=1012) were collected from non-vaccinated sheep, goats, camels and cattle of different sex, age and breed randomly from the abattoirs to investigate the circulating brucella antibodies using RBPT. One hundred and eighteen sera (9.7%) were reactive for Brucella spp. IgG immunoglobulins, with higher percentages detected in sheep (11.4%), females (13.3%), adults (10.7%), and naieme breed (13.9%). Significant correlation between Brucella spp. antibodies and animal species (0.095), age (0.077) was found, while strong correlation between antibodies and sex was observed. Glycosyltransferase gene was amplified and sequenced from camel reactive sera (n=6). Camel strains displayed multiple nucleotide substitutions and deletions, nucleotide identity among local strains is 96.2-100%. Phylogenetic analysis showed that Brucella spp. strains clustered in two groups, Rafha strains clustered in one group together with other strains. Further investigation is needed to determine the prevalence of the bacteria among farm animals and to identify the strains involved to improve the preventive measures and strategies adopted for control.

Detection of immune effects of the Mannheimia haemolytica gamma irradiated vaccine in sheep.

Exposure to gamma rays from cobalt 60 (Co60) can induce a complete inactivation of Mannheimia haemolytica. The inactivated bacterial pathogen is a potential vaccine candidate for immunization of ruminants such as sheep. The subcutaneous administration of irradiated vaccine in a two-dose regimen (4.0 × 109 colony forming unit (CFU) per dose) results in no mortality in any of the vaccinated sheep during immunization and after subsequent challenge of the live bacteria of the same strain of M. haemolytica. A significant rise in serum IgG titer, detected through ELISA, is observed after the passage of two weeks from the inoculation of the first dose whereas, the peak of the mean serum antibody titer occurred after two weeks of booster dose. The vaccination does not bring significant change to the IFN-γ levels in serum. The bacterial challenge of the vaccinated sheep does not induce a further seroconversion relative to serum antibody titer. In conclusion, the vaccinated sheep are protected by the elevated IgG titer and increased levels of IL-4 (Th-2 response) compared to the non-vaccinated sheep. Radiation technology can provide the opportunity for mass production of immunologically safe vaccines against animal and zoonotic diseases. Ethics Approval by the National Research Center Ethics Committee (Trial Registration Number (TRN) no 13,602,023, 13/5/2023) was obtained.

IP10 is a predictor of successful vaccine protection against paratuberculosis infection in sheep.

The cell mediated immune response and ability of immune cells to migrate to the site of infection are both key aspects of protection against many pathogens. Mycobacterium avium subsp. paratuberculosis (MAP) is an intracellular pathogen and the causative agent of paratuberculosis, a chronic wasting disease of ruminants. Current commercial vaccines for paratuberculosis reduce the occurrence of clinical disease but not all animals are protected from infection. Therefore, there is a need to understand the immune responses triggered by these vaccines at the site of infection, in circulating immune cells and their relationships to vaccine-mediated protection. The magnitude and location of gene expression related to the cell mediated immune response and cellular migration were studied in the ileum of sheep. In addition, longitudinal IP10 (also known as IP10) secretion by circulating immune cells was examined in the same sheep. Animals were grouped based on vaccination status (vaccinated vs non-vaccinated) and MAP exposure (experimentally exposed vs unexposed). Vaccination of unexposed sheep increased the expression of IP10, CCL5 and COR1c. Sheep that were successfully protected by vaccination (uninfected following experimental exposure) had significantly reduced expression of IP10 in the ileum at 12months post exposure compared to vaccine non-responders (those that became infected) and non-vaccinated infected sheep. Successfully protected sheep also had significantly increased secretion of IP10 in in vitro stimulated immune cells from whole blood compared to vaccine non responders at 4months post exposure. Therefore, the IP10 recall response has the potential to be used as marker for infection status in vaccinated sheep and could be a biomarker for a DIVA test in sheep.

Multivariable binary logistic regression model to predict risk factors of peste des petits ruminants in goat and sheep

Peste des petits ruminants (PPR) highly contagious illness that affects domestic and wild small ruminants, causing significant economic losses. The goal of this study was to use a multivariable logistic regression model to determine risk factors for PPR. A total of 113 healthy non-vaccinated goats and sheep (63 goats and 50 sheep) more than five months (1st group from 5-12 months,2nd group above 12 months), subject to a seroprevalence study by competitive ELISA which was used to detect antibodies against PPRV antibodies in serum sample during the period between April 2018 and March 2019. The incidence of PPR in autumn was significantly increased compared with the spring. Additionally, animals had a 4.08 more likelihood of being infected with PPR in the autumn compared with the spring season. There was a significant difference between male and female groups; The female group had 5.236 times increased odds of being infected with PPR than the male group. Moreover, the old age group had 2.771 times higher odds of being infected with PPR than the young age group. On the other hand, the test model found no evidence to support any significant differences between sheep and goat species. According to finding, PPR is common in females and mature small ruminants. Furthermore, throughout the spring season, the incidence of PPR was significantly reduced. Indeed, the current study may help plan an effective vaccination program against the PRP disease in Egypt.

Analysis of vaccination strategy against cystic echinococcosis developed in the Province of Río Negro, Argentina: 12 years of work

SummaryCystic echinococcosis (CE) is a zoonosis caused by species of the complex Echinococcus granulosus, sensu lato in their larval stage. It is an endemic disease in the province of Río Negro, where small farmers generally have both sheep and goats. Lamb vaccination with EG95 was incorporated in 2009 with very good results: in fact, it contributed to a significant drop in prevalence of infection in both sheep and goats, when determined by necropsy and serology in 2018. In the design of the activity, it was decided not to vaccinate goats in order to minimize the operational requirements of vaccination and comments from producers about the rarity of observing hydatid cysts in goat viscera were considered. ObjectiveTo identify causes which can still generate infection in dogs, and to detect species/genotypes in circulation in the province of Río Negro. Materials and methodsIn indigenous reserves comprised within the area of lamb vaccination with 3 doses of EG95, (dose 1 in December, dose 2 in January and dose 3 in December of the year following, at the time of application of dose 1 to the new lambs). Prevalence in adult goats and sheep was determined by necropsy and serology (ELISA). Infective species/genotypes present in the work area and in the rest of the province of Río Negro were identified by Cox1 mitochondrial gene sequencing. Epidemiological analysis was completed with surveys among farmers about slaughter habits for human consumption. ResultsThrough serology and necropsy, infection rates in vaccinated and nonvaccinated sheep were significantly different (21% versus 66%). Non-vaccinated sheep and non-vaccinated goats were also significantly different in that there was less infection in goats compared to sheep (7% versus 66% for necropsy, 30% versus 61% for serology); After many years of sheep vaccination the infection positives were low, and differences between vaccinated sheep and non-vaccinated goats turned out non-significant (21% versus 7%). With reference to epidemiology and control along the period 2018–2022, PZQ dosing of dogs 4 times a year was maintained, and 2 extra deworming tasks were introduced together with dose 1 and 2 of EG95, performed by the veterinary vaccination team, ensuring the ingestion of PZQ by dogs. Assessment of animal slaughter for consumption in 41 producers showed that 21 of them slaughter a monthly average of 18 goats (an average of 0.43 goat per month per farm) and 36 in all slaughter 35 old sheep in a year (average of 0.85 sheep per month per farm). With respect to identification of species/genotypes as from 2010, genotypes G1 have been found in 11 sheep (out of which 6 belong to vaccination zone) and genotypes G7, in one pig. A goat cyst within vaccination zone turned out unfertile and it was not possible to sequence it. ConclusionDesign and implementation of a vaccine programme combined with the use of PZQ resulted as cost-effective, since it was possible to maintain the vaccine over time, with clear impact on prevalence decrease in sheep and goats.

Sheep Brucellosis in Kuwait: A Large-Scale Serosurvey, Identification of Brucella Species and Zoonotic Significance.

Brucellosis is a common zoonotic disease of major concern in humans of Kuwait, and B. melitensis causes most human cases. The disease is endemic in small ruminants, cattle, and camels for decades, causing substantial economic losses in livestock production. However, a nationwide large-scale investigation of brucellosis in the small ruminant population has not been done in the past two decades. A serosurvey of sheep brucellosis in the five districts of Kuwait with most animal production farms was done between 2016 and 2019. In total, 67,054 serum samples from 233 sheep herds were collected and tested. Additionally, milk and tissue samples were collected from 46 seropositive cases for bacteriology. Thirty persons from seven seropositive farms were tested by serology. The incidence of seropositive cases was 7% in districts devoid of vaccination, while it was 4.7% in farms with history of vaccination. The serosurvey revealed that 89% of non-vaccinated herds (n = 181) were seropositive by Rose Bengal test (RBT), buffered acidified plate antigen test (BAPAT), and complement fixation test (CFT). Prevalence of 100% was reported for non-vaccinated sheep herds from Al-Wafrah and Al-Jahra districts, followed by those from Al-Salmi (88.24%), Al-Abdali (86.7%) and Kabd (75.6%). Implementation of vaccination with B. melitensis Rev.1 vaccine and test-and-slaughters in 20 herds reduced the seroprevalence to 33.3% and 25% in herds from Al-Jahra and AL-Wafrah, respectively. B. melitensis was isolated from 20 samples (43.5%). More than half of the examined animal owners (56.6%) tested positive for Brucella using RBT, BAPAT and CFT. The high numbers of infected herds and high prevalence in herdsmen are alarming. Thus, control measures have to be ensured immediately. The epidemiological situation in Kuwait is similar to those of the neighboring countries and the combined action of these states is needed. The understanding of the economic and public health impact of brucellosis in Kuwait needs to grow.

Seroprevalence of brucellosis in sheep and goats in the Arabian Gulf region.

Background and Aim:Brucellosis is a zoonosis that occurs worldwide. There were more efforts to control brucellosis in all countries. This study was performed to determine the seroprevalence of brucellosis in sheep and goats in some areas in the Arabian Gulf.Materials and Methods:The study analyzed 8500 sera from non-vaccinated sheep and goats. Animals included 6441 sheep (3420 from farms and 3021 from quarantine) and 2059 goats (1580 from farms and 479 from quarantine). Sera were tested using the Rose Bengal Plate Test (RBPT) and confirmed with an indirect enzyme-linked immunosorbent assay (i-ELISA) test. Final confirmation analyzed blood samples from confirmed infected animals (n=30, 23 sheep and seven goats) using polymerase chain reaction (PCR) and culture.Results:The serological examination showed that 62/8500 of animals (0.729%, confidence interval [CI] 95% 0.57-0.94) were seropositive for brucellosis. Thirteen of 5000 (0.26%, CI 95% 0.15-0.45) and 49/3500 (1.4%, CI 95% 1.1-1.8) of animals from farms and quarantine were seropositive, respectively. Out of the 6441, 46 (0.71%) sheep and 16/2059 (0.78%) goats were seropositive. i-ELISA confirmed 41/62 RBPT-positive animals – 41/8500 (0.482%, CI 95% 0.36-0.65). Eight of 5000 of these animals (0.16%, CI 95% 0.08-0.32) and 33/3500 (0.94%, CI 95% 0.67-1.3) were confirmed positive in farms and quarantine, respectively. Thirty of 6441 (0.466%) and 11/2059 (0.534%) cases were positive in sheep and goats, respectively. PCR confirmed 18 of 41 positive animals (0.212% of all sera, CI 95% 0.13-0.34) identified by both RBPT and i-ELISA. Three of 5000 (0.06%, CI 95% 0.019-0.19) and 15/3500 (0.429%, CI 95% 0.26-0.71) from farms and quarantine were confirmed positive. Tissue samples (uterine, supra-mammary, testicular, and accessory glands lymph node) were collected from positive animals, as detected by RBPT and i-ELISA, at culling or slaughtering. Using in vitro culture, 14/30 were confirmed positive – 3/7 from farms (two sheep and one goat) and 11/23 from quarantine (nine sheep and two goats). Biovar 1 was dominant. PCR confirmed 23/30 tissue samples, 4/7 from farms (three sheep and one goat), and 19/23 from quarantine (15 sheep and four goats).Conclusion:The overall brucellosis rate in sheep and goats is 0.48%, with fewer animals from farms testing positive (0.16%) in this area of the Arabian Gulf. The infection appears to be well controlled, and continuous effort is still needed to maintain control and completely eradicate brucellosis. Additional support is needed for testing and slaughterhouse monitoring. In quarantine (imported animals), brucellosis infection in the slaughterhouse (0.94%) could pose a risk for transmission and spread of infection. The effort is needed to monitor this threat, and PCR is a sensitive and time-saving test for brucellosis diagnosis. All 14 confirmed positive samples were Biovar 1 dominant.

Effect of progesterone on the vaccination and immune response against Chlamydia abortus in sheep

Chlamydia abortus produces ovine enzootic abortion (OEA). Symptoms are not observed until the organism colonises the placenta, eventually causing abortion. Infected animals become carriers and will shed the organism in the following oestruses. This process suggests that sex hormones might play an important role in the physiopathology of OEA, affecting the success of chlamydial clearance and also jeopardising the effectiveness of vaccination. However, the mechanisms through which sex hormones are involved in chlamydial pathogenicity remain unclear. The aim of this study, therefore, was to determine the effect of progesterone on the immune response against C. abortus and on the protection conferred by an experimental inactivated vaccine in sheep.Eighteen sheep were ovariectomised and divided into four groups: vaccinated and progesterone-treated (V-PG), vaccinated and non-treated (V-NT), non-vaccinated and non-treated (NV-NT) and non-vaccinated and progesterone-treated sheep (NV-PG). Animals from both PG groups were treated with commercial medroxyprogesterone acetate impregnated intravaginal sponges before and during the vaccination (V-PG) or just before challenge (NV-PG). The animals from both V groups were subcutaneously immunised with an experimental inactivated vaccine, which was seen to confer high protection in previous studies. All sheep were challenged intratracheally with C. abortus strain AB7 and were sacrificed on day 8 post-infection. Morbidity was measured as the variation in rectal temperature and samples of sera were collected for antibody and cytokine (IFN-γ and IL-10) analysis by commercial ELISA. In addition, lung and lymph node samples were collected for chlamydial detection by qPCR and for histopathological and immunohistochemical analyses.Sheep from the V-PG group showed less severe or no lesions and lower morbidity than the other groups. They also had the highest abundance of regulatory T-cells. The sheep from V-NT also manifested high antibody levels against C. abortus and less severe lesions than those observed in non-vaccinated sheep, which showed high morbidity, low antibody levels and severe lesions, especially in NV-NT. These results confirm the effectiveness of the experimental vaccine employed and suggest that progesterone could enhance the effect.

Assessment of the efficacy of an autogenous vaccine against Yersinia pseudotuberculosis in young Merino sheep

AIMSTo assess the efficacy of an autogenous vaccine against Yersinia pseudotuberculosis III in preventing clinical disease and deaths due to yersiniosis in young Merino sheep, and to determine the effect of vaccination on the prevalence of faecal shedding of pathogenic Yersinia spp., daily liveweight gain, and development of antibodies to Yersinia spp. following vaccination and natural exposure.METHODSIn six groups (three groups each from two farms) of young Merino sheep, 148–150 animals were systematically allocated to be vaccinated twice with an autogenous, formalin- killed bacterin vaccine containing Y. pseudotuberculosis serotype III or to remain non-vaccinated. All vaccinated and non-vaccinated sheep were run together in their original groups throughout the trial. Faecal and blood samples were collected, and liveweight measured, at the time of vaccination and subsequently over a 6-month period to determine faecal shedding of Y. enterocolitica and Y. pseudotuberculosis, seroprevalence of antibodies to Yersinia outer membrane proteins (YOP) and changes in liveweight.RESULTSNone of the six trial groups experienced an outbreak of clinical yersiniosis during the study period. On Farm A, the prevalence of shedding of either or both Yersinia spp. was <40% on all but one sampling occasions. On Farm B the prevalence of shedding of both Yersinia spp. peaked at 98%, 96 days after vaccination. Mean liveweight and daily liveweight gain at the end of the study were similar in vaccinated and non-vaccinated groups on both farms (p>0.1), as was the prevalence of faecal shedding of Yersinia spp. (p>0.2), and the proportion of animals that became seropositive for antibodies to YOP following vaccination (p>0.1).CONCLUSIONS AND CLINICAL RELEVANCEThis vaccine had, at most, limited effects on seroconversion and, under the conditions of this study, had no demonstrable impact on liveweight, mean daily liveweight gain or faecal shedding of Yersinia spp. Further studies are needed to determine the efficacy of this vaccine during outbreaks of yersiniosis or following experimental challenge with pathogenic Yersinia spp..

Investigating peste des petits ruminants (PPR) in naturally infected goats and sheep in Anseba Region, Eritrea, by reverse transcription polymerase chain reaction (RT-PCR).

The impact of peste des petits ruminants (PPR) virus was investigated by reverse transcription polymerase chain reaction (RT-PCR) on different samples obtained from non-vaccinated diseased and necropsied sheep and goats showing PPR-like symptoms. The disease picture was typical and sheep were observed to be less susceptible. Nasal and rectal swabs, whole blood and pathological tissue samples from the lungs, intestine, and mesenteric lymph nodes were used for this study. The results of RT-PCR indicated that from a total of 32 samples collected, 12 (41%) were positive by this method. Out of those collected samples, 29 were from goats and 3 were from sheep. Nasal and rectal swabs and blood samples were superior in detection of the PPR virus compared to other tissue samples.

Intratracheal infection as an efficient route for testing vaccines against Chlamydia abortus in sheep

Pregnant ewes have been widely used to test vaccines against Chlamydia abortus. However, this model entails many disadvantages such as high economic costs and long periods of pregnancy. The murine model is very useful for specific studies but cannot replace the natural host for the later stages of vaccine evaluation. Therefore, a non-pregnant model of the natural host might be useful for a vaccine trial to select the best vaccine candidates prior to use of the pregnant model. With this aim, two routes of infection were assessed in young non-pregnant sheep, namely, intranasal (IN) and intratracheal (IT). In addition, groups of non-vaccinated sheep and sheep immunised with an inactivated vaccine were established to investigate the suitability of the model for testing vaccines.After the experimental infection, isolation of the microorganism in several organs, with pathological and immunohistochemical analyses, antibody production assessment and investigation by PCR of the presence of chlamydia in the vagina or rectum were carried out. Experimental IT inoculation of C. abortus induced pneumonia in sheep during the first few days post-infection, confirming the suitability of the IT route for testing vaccines in the natural host. The course of infection and the resulting pathological signs were less severe in vaccinated sheep compared with non-vaccinated animals, demonstrating the success of vaccination. IN infection did not produce evident lesions or demonstrate the presence of chlamydial antigen in the lungs and cannot be considered an appropriate model for testing vaccines.

Transmission characteristics and optimal diagnostic samples to detect an FMDV infection in vaccinated and non-vaccinated sheep

We wanted to quantify transmission of FMDV Asia-1 in sheep and to evaluate which samples would be optimal for detection of an FMDV infection in sheep.For this, we used 6 groups of 4 non-vaccinated and 6 groups of 4 vaccinated sheep. In each group 2 sheep were inoculated and contact exposed to 2 pen-mates. Viral excretion was detected for a long period (>21 days post-inoculation, dpi). Transmission of FMDV occurred in the non-vaccinated groups (R0=1.14) but only in the first week after infection, when virus shedding was highest. In the vaccinated groups no transmission occurred (Rv<1, p=0.013). The viral excretion of the vaccinated sheep and the viral load in their pens was significantly lower than that of the non-vaccinated sheep.FMDV could be detected in plasma samples from 12 of 17 infected non-vaccinated sheep, for an average of 2.1 days, but in none of the 10 infected vaccinated sheep. In contrast, FMDV could readily be isolated from mouth swab samples from both non-vaccinated and vaccinated infected sheep starting at 1–3dpi and in 16 of 27 infected sheep up till 21dpi. Serologically, after 3–4 weeks, all but one of the infected sheep were detected using the NS-ELISA. We conclude that vaccination of a sheep population would likely stop an epidemic of FMDV and that the use of mouth swab samples would be a good alternative (instead of using vesicular lesions or blood samples) to detect an FMD infection in a sheep population both early and prolonged after infection.

CD4+ T-cells, γδ T-cells and B-cells are associated with lack of vaccine protection in Mycobacterium avium subspecies paratuberculosis infection

Vaccination is one of the strategies used to control the spread of Mycobacterium avium subspecies paratuberculosis (MAP) infection in livestock. Gudair® is a widely-used vaccine in sheep and goats and is the only vaccine approved for use in sheep in Australia and New Zealand. This vaccine reduces mortality due to MAP-infection by up to 90% but some sheep remain infectious by shedding MAP in faeces, despite vaccination. In this study, using an experimental infection model in sheep, our aim was to assess differences in immune parameters between vaccinated MAP-exposed sheep in which the vaccine was effective compared to those in which it failed to protect against infection. We assessed immune parameters such as MAP-specific IFNγ, IL-10 and lymphocyte proliferative responses and serum antibody levels. At the end of the trial, 72% of non-vaccinated sheep and 24% of vaccinated sheep were infected, as defined by the detection of viable MAP in intestinal tissues when the trial was terminated at 49 weeks post exposure. There were significant differences in the proliferation of CD4+, B and γδ T-cells over time in vaccinated sheep in which the vaccine failed to protect against infection compared to the non-infected vaccinated sheep. There were no significant differences in the IFNγ response or serum antibody levels between the vaccinated infected and vaccinated non-infected sheep. These results emphasise the importance of specific lymphocyte subsets in protecting against MAP-infection, especially in vaccinated sheep, and that immune parameters other than the commonly used IFNγ and antibody tests are required when assessing vaccine efficacy.

Evaluation of the immunogenicity and safety of Brucella melitensis B115 vaccination in pregnant sheep

In spite of its limitations, Rev.1 is currently recognized as the most suitable vaccine against Brucella melitensis (the causative agent of ovine and caprine brucellosis). However, its use is limited to young animals when test-and-slaughter programs are in place because of the occurrence of false positive-reactions due to Rev.1 vaccination. The B. melitensis B115 rough strain has demonstrated its efficacy against B. melitensis virulent strains in the mouse model, but there is a lack of information regarding its potential use in small ruminants for brucellosis control. Here, the safety and immune response elicited by B115 strain inoculation were evaluated in pregnant ewes vaccinated at their midpregnancy. Vaccinated (n=8) and non-vaccinated (n=3) sheep were periodically sampled and analyzed for the 108 days following inoculations using tests designed for the detection of the response elicited by the B115 strain and routine serological tests for brucellosis [Rose Bengal Test (RBT), Complement Fixation Test (CFT) and blocking ELISA (ELISAb)]. Five out of the 8 vaccinated animals aborted, indicating a significant abortifacient effect of B115 inoculation at midpregnancy. In addition, a smooth strain was recovered from one vaccinated animal, suggesting the occurrence of an in vivo reversion phenomenon. Only one animal was positive in both RBT and CFT simultaneously (91 days after vaccination) confirming the lack of induction of cross-reacting antibody responses interfering with routine brucellosis diagnostic tests in most B115-vaccinated animals.

Caseous lymphadenitis in small ruminants in Egypt

The aim of this study was to investigate the distribution of caseous lymphadenitis (CLA) among small ruminants in Egypt, identify risk factors associated with its occurrence and to analyze the efficacy of the vaccine for control of CLA. A total of 1206 sheep and 351 goats were examined clinically for CLA. The prevalence and the risk factors of CLA in small ruminant flocks were estimated and identified. Efficacy of the commercial vaccine Case-Bac (Colorado Serum Company, USA) was determined in a field study trial conducted on 15 CLA-free lambs. Follow-up of vaccination immune response was carried out using indirect ELISA. Prevalence of superficial CLA was 6.7%. Clinically, CLA appeared as abscesses in superficial lymph nodes mostly of the head and neck. On the basis of a multivariate analysis which accounted for clustering at herd level, sheep were at risk of getting superficial CLA 3.5 times more than goats (p < 0.0001). Animals of fixed flocks were at risk of getting the superficial CLA 2 times more than animals in fixed-mobile flocks (p < 0.038). Serological follow-up indicated protective antibody titers for 6 months. In vaccinated animals clinical cases were not observed while they occurred among non-vaccinated sheep. Prevalence of CLA varied among studied flocks even between those of the same breeding system due to complex and overlapping factors associated with each flock like introduction or culling rate of animals, care of shepherds or owners to deal with opened abscesses in addition to the average age of the animals within each flock. Breeding systems have observable effects on occurrence of CLA: infected sheep can transmit the infection to a large number of animals in a short period under the conditions of close contact and reduced air flow in covered sheds. Infected small ruminants in fixed flocks represent a risk factor for CLA for healthy ones. The vaccine used in the study provides an effective protection against new infections. So mass vaccination of small ruminants against CLA in Egypt has to be considered to minimize the disease prevalence.

Kinetics of epsilon antitoxin antibodies in different strategies for active immunization of lambs against enterotoxaemia

Enterotoxaemia, a common disease that affects domestic small ruminants, is mainly caused by the epsilon toxin of Clostridium perfringens type D. The present study tested four distinct immunization protocols to evaluate humoral response in lambs, a progeny of non-vaccinated sheep during gestation. Twenty-four lambs were randomly allocated into four groups according to age (7, 15, 30 and 45 days), receiving the first dose of epsilon toxoid commercial vaccine against clostridiosis with booster after 30 days post vaccination. Indirect ELISA was performed after the first vaccine dose and booster to evaluate the immune response of the lambs. Results showed that for the four protocols tested all lambs presented serum title considered protective (≥0.2UI/ml epsilon antitoxin antibodies) and also showed that the anticipation of primovaccination of lambs against enterotoxaemia conferred serum title considered protective allowing the optimization of mass vaccination of lambs.

Timing of activation of CD4+ memory cells as a possible marker to establish the efficacy of vaccines against contagious agalactia in sheep

Mycoplasma agalactiae is a major pathogen of sheep and goats in many areas of the world and particularly in Mediterranean countries. It causes contagious agalactia, an infectious disease primarily affecting mammary glands. Many vaccines against the pathogen are currently under development. The aim of the study was to investigate the involvement of T cell-mediated immunity during vaccination and challenge experiments against Mycoplasma agalactiae. A comparison of the antigen-specific expansion of interferon gamma positive T cell memory and naïve subsets was performed between vaccinated and non-vaccinated sheep to identify cellular subsets whose activation was different between protected and non-protected sheep. Data reported in this manuscript demonstrated that two out of the three vaccines used in this study protected sheep from the disease. In the protected groups CD4+ memory interferon-γ+ T cells underwent an early expansion (p<0.05 when compared to unprotected groups), whilst memory CD8+ Interferon-γ+ T cells increased in non-protected animals 7 days after infection (p<0.05). γδ+ Interferon-γ+ T cells reached peaks of expansion in infected and in two vaccinated groups thus indicating that these cells are not preferentially involved in protection or pathogenesis (p<0.05).Hereby we propose that the early activation of CD4+ memory Interferon-γ+ T cells could be considered as a marker of protection from the disease as well as a tool to establish vaccine efficacy.

Vaccination against foot-and-mouth disease II: Regaining FMD-free status

An epidemic of foot-and-mouth disease (FMD) can have devastating effects on animal welfare, economic revenues, the export position and society as a whole. The preferred control strategy in the Netherlands has recently changed to vaccination-to-live, but – not have been applied before – this poses unprecedented challenges for effectively controlling an epidemic, regaining FMD-free status and minimizing economic losses. These three topics are addressed in an interdisciplinary model analysis. In this second part we evaluate whether vaccination-to-live poses a higher risk for regaining FMD-free status than non-vaccination strategies and whether the final screening can be improved to reduce this risk. The FMD transmission model that was developed in the first part, predicted the prevalence of infected animals in undetected herds for 1000 hypothetical epidemics per control strategy. These results serve as input for the final screening model that was developed in this part. It calculates the expected number of undetected infected herds and animals per epidemic after final screening, as well as the number of herds and animals to be tested. Our results show that vaccination strategies yield a larger number of undetected infected animals in the whole country per epidemic before final screening than preemptive culling (median values and 5–95% interval): 8 (0–42) animals for 1km preemptive culling, 50 (7–148) for 2km vaccination and 35 (6–99) for 5km vaccination. But the final screening reduced these to comparably low numbers: 1.0 (0–9.1) for 1km preemptive culling, 3.5 (0.3–15) for 2km vaccination and 2.1 (0.3–9.4) for 5km vaccination. Undetected infected animals were mainly found in non-vaccinated sheep herds and vaccinated cattle and sheep herds. As a consequence, testing more non-vaccinated cattle and pig herds will not reduce the expected number of undetected infected animals after the final screening by much, while the required testing resources drastically increase. However, testing only a sample instead of all animals in vaccinated pig herds will not increase the expected number of undetected infected animals by much, while the required testing resources reduce by half. In conclusion, vaccination and preemptive culling strategies yield comparable numbers of undetected infected animals after final screening and the final screening costs can be reduced by testing a sample instead of all vaccinated pigs.

Brucellosis control in Tajikistan using Rev 1 vaccine: change in seroprevalence in small ruminants from 2004 to 2009

Cross-sectional serological surveys of 13,006 small ruminants were conducted in 2003 to establish baseline levels of seropositivity to brucellosis and of 12,102 again in 2009 to evaluate the efficacy of...

Quantifying foot-and-mouth disease virus transmission rates using published data

Foot-and-mouth disease is an extremely infectious and devastating disease affecting all species of cloven-hoofed animals. To understand the epidemiology of the causative virus and predict viral transmission dynamics, quantified transmission parameters are essential to decision makers and modellers alike. However, such quantified parameters are scarcely available, and recently a series of animal experiments was set up to obtain such data experimentally. In this communication, however, we report on the use of data from an animal experiment conducted 10 years ago to quantify transmission of foot-and-mouth disease virus between non-vaccinated sheep and from sub-clinically infected sheep to in-contact pigs. This new analysis utilises a state-of-the-art Generalised Linear Model to estimate the transmission rate. From the obtained results it is concluded that meta-analysis of "old" experiments using newly developed techniques can provide useful data to replace, reduce and refine future foot-and-mouth disease transmission experiments, thereby minimising animal suffering for research purposes.