The field effectiveness of routine and emergency vaccination with an inactivated vaccine against foot and mouth disease

Foot and mouth disease viruses are recurrently introduced to Israel and spread by extensively reared sheep and cattle: Insights from a whole-genome sequence analysis

Despite routine vaccination, Israel experiences recurrent outbreaks of foot and mouth disease (FMD). We analyzed VP1 coding sequences of viruses isolated during FMD outbreaks from 2001 to 2011 in Israel and neighboring nations. The Israeli strains were aligned with strains from neighboring countries in corresponding years, implying repeated FMD virus incursions. In 2007 a large FMD epidemic, caused by a serotype O virus, occurred in Israel. Bayesian analysis of whole-genome sequences of viruses isolated during this epidemic revealed predominant transmission among extensively farmed beef-cattle and small ruminants. Small ruminants were key in spreading to beef-cattle, which then transmitted the virus to feedlot-cattle. Wild gazelles had a minor role in transmission. The results may suggest probable transmission of FMD virus from the Palestinian Authority to Israel. Targeting extensive farms via enhanced surveillance and vaccination could improve FMDV control. Given cross-border transmission, a collaborative FMD mitigation strategy across the Middle-East is crucial.

Emergency vaccine immunization protects hamsters against acute leptospirosis

Leptospirosis, caused by pathogenic Leptospira, is a global critical zoonotic disease in terms of mortality and morbidity. Vaccines are often used to prevent leptospirosis. However, few studies have reported the therapeutic effect of a vaccine against Leptospira infection. This study demonstrates the efficacy of the emergency vaccine immunization against acute leptospirosis in hamsters. Treatment with a whole-cell vaccine (Leptospira interrogans serovar Lai) at 24 h post-infection improved the survival rate of hamsters with lower leptospiral burden and minor pathological damage to organs. The vaccine also protected against multiple Leptospira serotypes acute infection. However, the protective effect of the vaccines was lost when beginning treatment at 36 h or 48 h post-infection. These results indicated that vaccines could treat acute leptospirosis in hamsters, but only if immunization is within 24 h after infection.

Challenges to the Application of Spatially Explicit Stochastic Simulation Models for Foot-and-Mouth Disease Control in Endemic Settings: A Systematic Review

Simulation modeling has become common for estimating the spread of highly contagious animal diseases. Several models have been developed to mimic the spread of foot-and-mouth disease (FMD) in specific regions or countries, conduct risk assessment, analyze outbreaks using historical data or hypothetical scenarios, assist in policy decisions during epidemics, formulate preparedness plans, and evaluate economic impacts. Majority of the available FMD simulation models were designed for and applied in disease-free countries, while there has been limited use of such models in FMD endemic countries. This paper's objective was to report the findings from a study conducted to review the existing published original research literature on spatially explicit stochastic simulation (SESS) models of FMD spread, focusing on assessing these models for their potential use in endemic settings. The goal was to identify the specific components of endemic FMD needed to adapt these SESS models for their potential application in FMD endemic settings. This systematic review followed the PRISMA guidelines, and three databases were searched, which resulted in 1176 citations. Eighty citations finally met the inclusion criteria and were included in the qualitative synthesis, identifying nine unique SESS models. These SESS models were assessed for their potential application in endemic settings. The assessed SESS models can be adapted for use in FMD endemic countries by modifying the underlying code to include multiple cocirculating serotypes, routine prophylactic vaccination (RPV), and livestock population dynamics to more realistically mimic the endemic characteristics of FMD. The application of SESS models in endemic settings will help evaluate strategies for FMD control, which will improve livestock health, provide economic gains for producers, help alleviate poverty and hunger, and will complement efforts to achieve the Sustainable Development Goals.

Influenza A virus vaccine research conducted in swine from 1990 to May 2018: A scoping review

BACKGROUND

Influenza A viruses of swine (IAV-S) are a global zoonotic and economic concern. Primary control is through vaccination yet a formal evidence map summarizing vaccine research conducted in pigs is not available.

OBJECTIVE

Ten characteristics of English language primary IAV-S vaccine research, conducted at the level of the pig or higher, were charted to identify research gaps, topics for systematic review, and coverage across different publication types.

DESIGN

Six online databases and grey literature were searched, without geographic, population, or study type restrictions, and abstracts screened independently and in duplicate for relevant research published between 1990 and May 2018. Full text data was charted by a single reviewer.

RESULTS

Over 11,000 unique citations were screened, identifying 376 for charting, including 175 proceedings from 60 conferences, and 170 journal articles from 51 journals. Reported outcomes were heterogeneous with measures of immunity (86%, n = 323) and virus detection (65%, n = 246) reported far more than production metrics (9%, n = 32). Study of transmissibility under conditions of natural exposure (n = 7), use of mathematical modelling (n = 11), and autogenous vaccine research reported in journals (n = 7), was limited.

CONCLUSIONS

Most research used challenge trials (n = 219) and may have poor field relevance or suitability for systematic review if the purpose is to inform clinical decisions. Literature on vaccinated breeding herds (n = 89) and weaned pigs (n = 136) is potentially sufficient for systematic review. Research under field conditions is limited, disproportionately reported in conference proceedings versus journal articles, and may be insufficient to support systematic review.

Risk factors of foot and mouth disease in an endemic area on low vaccination rate in Xayaboury province of Lao People's Democratic Republic (Lao PDR)

In Xayaboury province, located in the northern region of Lao PDR, the foot and mouth disease (FMD) vaccination campaign just began in 2009. Up until now, a small number of farms have been vaccinated. When FMD outbreaks occur, it is interesting to determine the risk factors of FMD, especially in the area where vaccination rates are low. The questionnaire survey, using a case-control design at the household level, was carried out. From 59 villages with a total number of 434 households, 181 households who experienced FMD were assigned as case households, 146 households without FMD occurrence inside the outbreak villages as inside control households, and 107 households without FMD occurrence outside the outbreak villages as outside control households. Household owners were interviewed. The logistic regression model was used to identify the relationship between FMD occurrence (dependent variable) and the collected data (independent variables), including the social status of livestock owners, FMD prevention strategies, and farm locations. A non-parametric test was performed to determine the association of FMD and network parameters of animal movements among villages. In general, results show that a limited number of holders did vaccinate animals before the outbreaks (13.8-17.8%). The results indicated that livestock owners who had known information about FMD before the outbreaks had been less severely affected by the FMD outbreak than the owners who had not known information about FMD (P < 0.01, OR 0.16, 95% CI 0.09-0.29). Before the outbreaks, higher FMD risk was observed in owners who sold the livestock through animal traders (P < 0.01, OR 4.76, 95% CI 1.68-13.50). Spatial data show that households in the community closer to the main roads had higher FMD risk (P < 0.01, OR 4.76, 95% CI 1.68-13.50). In addition, the network parameters including in-degree, out-degree, and betweenness indicated that the villages with high movements of livestock were at high risk of FMD (P < 0.05). The present study emphasized the importance of the government units to distribute the information about FMD to all livestock farmers in Xayaboury. Disease awareness and prevention strategy should be prioritized in areas close to high density communities and in the trading of livestock.

The epidemiology of foot-and-mouth disease outbreaks and its history in Iraq

Background and Aims:

Foot-and-mouth disease (FMD) is reported in Iraq since 1937 and occurs as a devastating seasonal epidemic. This study intended to explore the epidemiology of FMD in Iraq during 2011-2016, through assessment of outbreak reports among cow, buffalo, and small ruminants (sheep and goat) in 15 Iraqi governorates except for Kurdistan region.

Materials and Methods:

The reported data regarding FMD cases were collected from veterinary hospitals in 15 Iraqi governorates and were analyzed.

Results:

The results revealed annual FMD outbreaks in cow, buffalo, and small ruminants in Iraqi governorates with variability in the numbers of the infected and dead animals. The total number of infected animals increased in 2016 compared to 2015 due to the illegal importation of FMD-infected cows at the end of 2015. The prevalence rates of FMD were 68.7%, 46.6%, and 30.3% in cattle, buffalo, and small ruminants, respectively, in 2016, while this was 18.4%, 19.9%, and 17.3%, respectively, in 2015.

Conclusion:

This study approved the reemergence and endemic nature of FMD in Iraqi livestock. Prompt procedures and a new future strategy need to be implemented to control the increasing incidences of FMD in Iraq.

Risk factors for recurrence of FMD outbreaks in Iran: a case-control study in a highly endemic area

BACKGROUND

Foot-and-mouth disease (FMD) is an acute viral disease of cloven-hoofed animals with high economic impact. FMD remains endemic in Iran particularly in the livestock-dense province of Khorasan Razavi in northeastern Iran where FMD outbreaks continuously occur. In this study, we aimed to quantify risk factors for the recurrence of FMD outbreaks in Iran by analyzing a time-series of FMD outbreak data from the province of Khorasan Razavi.

RESULTS

This study used FMD outbreak data collected from 2012 to 2014. Data were collected by local offices of the Iranian Animal Disease Department and the veterinarian of the veterinary council of the Khorasan Razavi province. An outbreak investigation questionnaire was delivered to 127 farms, including 46 case farms (FMD-infected) and 81 control farms (FMD-free). To quantify and compare the odds of exposure to a risk factor in FMD-infected farms versus FMD-free farms, logistic regression models were built using SPSS software version 16. Our results of multivariable logistic regression indicate that hygienic status of the farm (OR = 11.83; CI = 3.38-41.43), FMD vaccination status (OR = 0.06; CI = 0.01-0.68), transportation of livestock (OR = 0.40; CI = 0.163-0.981) and inhibition of livestock dealers' entry into the farm (OR = 0.36; CI = 0.12-1.09) were identified as important risk factors for farm-level FMD infection.

CONCLUSION

This study generated much needed evidence on a set of modifiable risk factors for the recurrence of FMD outbreaks in the high risk province of Khorasan Razavi. This information can be used to improve existing national FMD control program and suggest new guidelines to prevent FMD outbreaks in the country.

Spatial and temporal risk as drivers for adoption of foot and mouth disease vaccination

Identifying the drivers of vaccine adoption decisions under varying levels of perceived disease risk and benefit provides insight into what can limit or enhance vaccination uptake. To address the relationship of perceived benefit relative to temporal and spatial risk, we surveyed 432 pastoralist households in northern Tanzania on vaccination for foot-and-mouth disease (FMD). Unlike human health vaccination decisions where beliefs regarding adverse, personal health effects factor heavily into perceived risk, decisions for animal vaccination focus disproportionately on dynamic risks to animal productivity. We extended a commonly used stated preference survey methodology, willingness to pay, to elicit responses for a routine vaccination strategy applied biannually and an emergency strategy applied in reaction to spatially variable, hypothetical outbreaks. Our results show that households place a higher value on vaccination as perceived risk and household capacity to cope with resource constraints increase, but that the episodic and unpredictable spatial and temporal spread of FMD contributes to increased levels of uncertainty regarding the benefit of vaccination. In addition, concerns regarding the performance of the vaccine underlie decisions for both routine and emergency vaccination, indicating a need for within community messaging and documentation of the household and population level benefits of FMD vaccination.

Systemic antibodies administered by passive immunization prevent generalization of the infection by foot-and-mouth disease virus in cattle after oronasal challenge

The role of passively transferred sera in the protection against aerogenous foot-and-mouth disease (FMD) virus infection in cattle was evaluated using vaccine-induced immune serum preparations obtained at 7 and 26 days post-vaccination (dpv). We showed that circulating antibodies were sufficient to prevent disease generalization after oronasal infection in animals passively transferred with 26-dpv serum but not with the 7-dpv serum. Conversely, conventional FMD vaccination provided clinical protection at 7 dpv, promoting fast and robust antibody responses upon challenge and even though antibody titers were similar to those found in animals passively immunized with 7-dpv serum. These results demonstrate that presence of antigen-specific antibodies is critical to prevent the dissemination of the virus within the animal. Conventional FMD vaccination additionally promoted the deployment of rapid, high titer and isotype-switched antibody responses at systemic and mucosal levels after infection, thus conferring protection even in the presence of low pre-challenge antibody titers.

Evaluation of a polyvalent foot-and-mouth disease virus vaccine containing A Saudi-95 against field challenge on large-scale dairy farms in Saudi Arabia with the emerging A/ASIA/G-VII viral lineage

In 2015, foot-and-mouth disease (FMD) viruses of the A/ASIA/G-VII lineage emerged from the Indian sub-continent to cause outbreaks in the Middle and Near East. A factor which has been proposed to have contributed to the rapid spread of this lineage is the poor in vitro vaccine-match of field isolates to vaccine strains that are commonly used in the region. This study used data from outbreaks on four large-scale dairy farms using routine vaccination in Saudi Arabia, to evaluate the impact of vaccination and learn how to manage outbreaks more effectively in this setting. This evaluation also included an assessment of vaccine-induced neutralisation titres to the vaccine and field strains on a related farm with no history of FMD that employed an identical vaccination schedule. The incidence risk among exposed groups ranged from 2.6 to 20.1% and was significantly higher among youngstock (18.7%) compared to adults (7.4%). Evidence was found that local isolation of individual sick animals was more effective than whole group isolation and that subclinical infection and undetected circulation may occur on large-scale farms in Saudi Arabia, although both of these points require further evaluation. On the unaffected farm, the mean reciprocal titres for the vaccine and field strains were all above the cut-off supposed to correlate with clinical protection based on evidence from challenge studies. An estimate of vaccination effectiveness was not possible on the affected farms, but the incidence of FMD provides a more realistic estimation of the expected vaccine performance than in vivo studies or r1 value as it is based on field conditions and natural exposure. This study shows that analysis of field data from FMD outbreaks are a useful addition to more conventional challenge and in vitro based evaluations of vaccines and suggests further work is necessary to validate correlates of protection in field conditions.

Global Foot-and-Mouth Disease Research Update and Gap Analysis: 3 - Vaccines

This study assessed research knowledge gaps in the field of FMDV (foot-and-mouth disease virus) vaccines. The study took the form of a literature review (2011-15) combined with research updates collected in 2014 from 33 institutes from across the world. Findings were used to identify priority areas for future FMD vaccine research. Vaccines play a vital role in FMD control, used both to limit the spread of the virus during epidemics in FMD-free countries and as the mainstay of disease management in endemic regions, particularly where sanitary controls are difficult to apply. Improvements in the performance or cost-effectiveness of FMD vaccines will allow more widespread and efficient disease control. FMD vaccines have changed little in recent decades, typically produced by inactivation of whole virus, the quantity and stability of the intact viral capsids in the final preparation being key for immunogenicity. However, these are exciting times and several promising novel FMD vaccine candidates have recently been developed. This includes the first FMD vaccine licensed for manufacture and use in the USA; this adenovirus-vectored FMD vaccine causes in vivo expression of viral capsids in vaccinated animals. Another promising vaccine candidate comprises stabilized empty FMDV capsids produced in vitro in a baculovirus expression system. Recombinant technologies are also being developed to improve otherwise conventionally produced inactivated vaccines, for example, by creating a chimeric vaccine virus to increase capsid stability and by inserting sequences into the vaccine virus for desired antigen expression. Other important areas of ongoing research include enhanced adjuvants, vaccine quality control procedures and predicting vaccine protection from immune correlates, thus reducing dependency on animal challenge studies. Globally, the degree of independent vaccine evaluation is highly variable, and this is essential for vaccine quality. Previously neglected, the importance of evaluating vaccination programme effectiveness and impact is increasingly being recognized.

The serological response against foot and mouth disease virus elicited by repeated vaccination of dairy cattle

In Israel, cattle are annually vaccinated against foot and mouth disease (FMD). If infections with FMD virus occur in dairy farms it mainly involves heifers and calves, while older dairy cows seldom become infected. We hypothesized that this difference in susceptibility between adult cows and the young heifers and calves is due to stronger and more stable immune response elicited by multiple vaccinations. In order to test this hypothesis, 99 dairy cattle, divided into six groups according to number of prior vaccinations, were annually vaccinated with a trivalent vaccine (A, O and Asia-1) and followed during two consecutive years. In total 988 sera were sampled at 11 time points. Virus neutralization tests (VNT) were performed in order to determine the neutralizing antibody titers (NAT) against the vaccine homologous serotypes: O-4625, O-Manisa, Asia-1-Shamir and the heterologous serotype A-Turkey-20/2006. A similar NAT pattern was observed to all serotypes and therefore statistical analysis was restricted to O-4625 serotype. In the 'high vaccination' groups (cows that were vaccinated at least four times before the study), high NAT were found on the beginning of the trial and no or only a mild increase of NAT was observed following further vaccinations. Additionally, in the 'high vaccination' groups, the percentage of cows that had a NAT higher than 2.0 (log10) by the end of the 1st year was significantly higher than in the 'low vaccination' groups (cows vaccinated only three times or less before the study). We conclude that starting from the 5th vaccination, the NAT increase following vaccination is mild and NAT are persistent, suggesting reduction of the frequency of routine vaccination after multiple vaccinations is possible.

Prevalence and risk factors for foot and mouth disease infection in cattle in Israel

Foot and mouth disease (FMD) is a highly contagious viral disease with major economic consequences. In Israel, FMD epidemics recur almost every year and mostly affect cattle. The highest number of outbreaks occurs among beef cattle farms, followed by feedlot farms and dairy farms. We performed several cross-sectional serological studies in Israel during 2006-2014, aimed to reveal if the virus is endemic among cattle and to determine the sero-prevalence of antibodies directed against non-structural proteins (NSP) of FMD virus. Additionally we aimed to determine the risk factors for such sero-positivity. A risk based sampling was performed and the presence of anti-NSP antibodies was estimated using the PrioCHECK(®) ELISA kit. Beef cattle showed the highest sero-prevalence (13.2%, CI95%=10.8-15.8%). Higher FMD sero-prevalence in beef cattle sampled in 2014 was associated with previous FMD outbreaks in the farm and with age (adult cows versus calves (p<0.05)). Sero-prevalence in feedlot calves was significantly lower with only one sero-positive calf out of 256 (0.4%, CI95%=0-2.2%). Sero-prevalence among dairy cattle was 2.7% (CI95%=2-3.6%) with location of up to 3km from FMD outbreaks in multiple farms and location of up to 5km from the nearest border standing out as significant (p<0.05) risk factors for sero-positivity. The extremely low sero-prevalence of FMD in feedlot cattle and the significant association of infection in beef cattle with previous outbreaks suggest absence of virus circulation between these two populations during the study period, although previous data show that during outbreaks such transmission can occur. Low sero-prevalence in dairy cattle located in areas adjacent to previous FMD outbreaks may be attributed to intense routine vaccination and stringent control measures that were applied during outbreaks such as emergency vaccination and strict quarantine. Early detection of FMD outbreaks among grazing beef herds as well as the implementation of control measures among these farms are therefore the methods of choice to prevent future outbreaks in Israel.

Foot-and-Mouth Disease Impact on Smallholders - What Do We Know, What Don't We Know and How Can We Find Out More?

Foot‐and‐mouth disease (FMD) endemic regions contain three‐quarters of the world's FMD susceptible livestock and most of the world's poor livestock keepers. Yet FMD impact on smallholders in these regions is poorly understood. Diseases of low mortality can exert a large impact if incidence is high. Modelling and field studies commonly find high FMD incidence in endemic countries. Sero‐surveys typically find a third of young cattle are sero‐positive, however, the proportion of sero‐positive animals that developed disease, and resulting impact, are unknown. The few smallholder FMD impact studies that have been performed assessed different aspects of impact, using different approaches. They find that FMD impact can be high (>10% of annual household income). However, impact is highly variable, being a function of FMD incidence and dependency on activities affected by FMD. FMD restricts investment in productive but less FMD‐resilient farming methods, however, other barriers to efficient production may exist, reducing the benefits of FMD control. Applying control measures is costly and can have wide‐reaching negative impacts; veterinary‐cordon‐fences may damage wildlife populations, and livestock movement restrictions and trade bans damage farmer profits and the wider economy. When control measures are ineffective, farmers, society and wildlife may experience the burden of control without reducing disease burden. Foot‐and‐mouth disease control has benefitted smallholders in South America and elsewhere. Success takes decades of regional cooperation with effective veterinary services and widespread farmer participation. However, both the likelihood of success and the full cost of control measures must be considered. Controlling FMD in smallholder systems is challenging, particularly when movement restrictions are hard to enforce. In parts of Africa this is compounded by endemically infected wildlife and limited vaccine performance. This paper reviews FMD impact on smallholders in endemic countries. Significant evidence gaps exist and guidance on the design of FMD impact studies is provided.

Epidemiological analysis of an outbreak of foot-and-mouth disease (serotype SAT2) on a large dairy farm in Kenya using regular vaccination

During August-September 2012, an outbreak of Foot-and-mouth Disease (FMD) due to serotype Southern African Territories-2 (SAT2) occurred on a large, extensively grazed dairy farm in Nakuru County, Kenya. Over 29 days, 400/644 (62.1%) cattle were recorded as displaying clinical signs consistent with FMD. Out of the 18 management groups present, 17 had clinical cases (weighted mean incidence rate 3.5 per 100 cattle-days, 95% CI 2.4, 5.1; range 0.064-10.9). Transmission may have been encouraged when an infected group was moved to a designated isolation paddock. A four to five day minimum incubation period was apparent in five groups for which a point source exposure was evident. Further transmission was associated with the movement of individual animals incubating infection, use of a common dip and milking parlour, and grazing of susceptible groups in paddocks neighbouring to infectious cases. Animals over 18 months old appeared to be at highest risk of disease possibly due to milder clinical signs seen among younger animals resulting in reduced transmission or cases not being recorded. Cows with a breeding pedigree containing a greater proportion of zebu appeared to be at lower risk of disease. The outbreak occurred despite regular vaccination (three times per year) last performed approximately three months before the index case. Incidence risk by the lifetime number of doses received indicated limited or no vaccine effectiveness against clinical disease. Reasons for poor vaccine effectiveness are discussed with antigenic diversity of the SAT2 serotype and poor match between the field and vaccine strain as a likely explanation. Detailed field-derived epidemiological data based on individual animals are rarely presented in the literature for FMD, particularly in East-Africa and with the SAT2 serotype. This study provides a detailed account and therefore provides a greater understanding of FMD outbreaks in this setting. Additionally, this is the first study to provide field-derived evidence of poor vaccine effectiveness using a SAT2 vaccine. Further field-based measures of vaccine effectiveness in line with evaluation of human vaccines are needed to inform FMD control policy which has previously relied heavily upon experimental data and anecdotal experience.

Antigenic properties and virulence of foot-and-mouth disease virus rescued from full-length cDNA clone of serotype O, typical vaccine strain

We cloned the full-length cDNA of O Manisa, the virus for vaccinating against foot-and-mouth disease. The antigenic properties of the virus recovered from the cDNA were similar to those of the parental virus. Pathogenesis did not appear in the pigs, dairy goats or suckling mice, but neutralizing antibodies were raised 5-6 days after the virus challenge. The utilization of O Manisa as a safe vaccine strain will increase if recombinant viruses can be manipulated by inserting or removing a marker gene for differential serology or replacing the protective gene from another serotype.

Association of the time that elapsed from last vaccination with protective effectiveness against foot-and-mouth disease in small ruminants

Routine and emergency vaccination of small ruminants against foot-and-mouth disease (FMD) is mandatory in many endemic countries, yet data on the field effectiveness of the vaccines used is scarce. We conducted an investigation of a serotype O FMD outbreak that took place in a sheep and goat pen, and estimated the effectiveness of various routine vaccination statuses. We also evaluated the protection provided by colostrum administration and emergency vaccination. Animals which were routinely vaccinated twice were not clinically affected while disease incidence was observed among animals routinely vaccinated only once (p = 0.004 according to a two-sided Fisher's exact test). In groups vaccinated only once, there was a significant association between the average time that elapsed since last vaccination and the disease incidence (n = 5; Spearman correlation coefficient: r_s = 1.0, p < 0.01). In addition, non-vaccinated lambs fed colostrum from dams vaccinated more than 2 months before parturition had a mortality rate of 33%. Administration of emergency vaccination 2 days after the occurrence of the index case was the probable reason for the rapid blocking of the FMD spread within 6 days from its onset in the pen.

Supplementation of dietary germanium biotite enhances induction of the immune responses by foot-and-mouth disease vaccine in cattle

Background

After the recent outbreak of foot-and-mouth disease (FMD) in Korea, a vaccination policy has been applied to control the disease. In addition, several non-specific immune stimulators have been used without any scientific evidence that they would enhance the immune response after FMD vaccination and/or protect against FMD. Based on the current situation, the aim of this study was to evaluate the effect of the non-specific immune stimulator germanium biotite on FMD vaccination and immune responses in cattle. To achieve our goal, immune responses to FMD vaccination, such as levels of IgG and IgA, antibody duration, and virus-neutralizing titers were investigated after germanium biotite feeding. The PBMC typing and proliferative response after stimulation with mitogens, the cytokines expression level of PBMC, and the lysozyme activity in the serum were measured to evaluate the immune enhancing effects of germanium biotite following its administration.

Results

Following the first vaccination, high level of IgG (at 4 weeks) and IgA (at 2 and 31 weeks) titers in serum and saliva were observed in the germanium biotite-feeding group (p < 0.05). The germanium biotite group also showed high and longstanding inhibition percentage value in ELISA assay at 31 weeks (p < 0.05). Generally, higher virus-neutralizing antibody titers were observed in the feeding group at 20 and 31 weeks after vaccination. Following the feeding germanium biotite, the germanium biotite group showed increased subpopulation of CD4⁺ lymphocytes and MHC I⁺II⁺ cells in PBMCs at 23 week, responding to stimulation of ConA. The levels of IFN-γ (at 3 and 8 weeks), IL-1α (at 3, 11, and 23 weeks), IL-1β (at 3, 8, and 11 weeks), and IL-4 (at 8 and 11 weeks) gene expression were also significantly increased in the feeding group (p < 0.01 and p < 0.05). Feeding with germanium biotite increased the lymphocytes’ proliferative response to the stimulation of ConA and LPS at 23 weeks and lysozyme activity at 9 weeks after feeding.

Conclusions

These results suggest that germanium biotite feeding could increase the protection against FMD virus infection via the induction of higher humoral and cellular immune responses in cattle.

Effects of germanium biotite supplement on immune responses of vaccinated mini-pigs to foot-and-mouth disease virus challenge

Since the outbreaks of foot-and-mouth disease (FMD) in South Korea in 2010-2011, a trivalent vaccine has been used as a routine vaccination. Despite the high efficacy of the trivalent vaccine, low antibody formation was reported in the pig industry and there is considerable concern about the ability of the vaccine to protect against the Andong strain responsible for recent outbreaks in South Korea. To overcome these problems, immunostimulators have been widely used to improve vaccine efficacy in South Korea, although without any scientific evidence. Based on the current situation, the aim of this study was to investigate the effects of germanium biotite, a feed supplement used to enhance the immune system, on the immune responses to FMD vaccination through the Andong strain challenge experiment in trivalent vaccinated pigs. Following the challenge, the germanium biotite-fed pigs showed high levels of IL-8 in serum, and increased cellular immune responses to stimulation with the Andong strain antigen compared to nonsupplemented pigs. In addition, higher FMD virus (FMDV) neutralizing antibody titers were detected in the germanium biotite-fed group than in the nonsupplemented group before the challenge. The findings of this study indicate that germanium biotite supplement might enhance immune responses to the FMD vaccine in pigs.