Duration of Immunity in Cattle to Lumpy Skin Disease Utilizing a Sheep Pox Vaccine.

The transmission of lumpy skin disease (LSD) occurs through ticks, mosquitoes, and flies. The most effective way to combat LSD is to conduct large-scale vaccination, covering the entire cattle population with safe and effective vaccines, while introducing restrictions on the movement of livestock. The first and only LSD cases that occurred in Armenia happened in 2015,and they were controlled with the use of a once yearly heterologous sheep pox vaccine for cattle in high-risk areas. We have previously reported on the safety and immunogenicity of this vaccine in cattle, but information on the duration of immunity is lacking. Our aim was to determine the duration of immunity to the LSD virus (LSDV) in cattle when utilizing a heterologous sheep pox vaccine. We have evaluated antibodies in cattle blood prior to and post-vaccination (1, 6, and 11 months). We have utilized an enzyme-linked immunosorbent assay to follow the development and waning of LSDV antibodies in vaccinated cattle in two age groups: 1) young unvaccinated cattle ≤12 months of age and 2) adult cattle that had previously been vaccinated. Our results were consistent with our previous study in Armenia, showing a high level of population immunity, 80.0-83.3%, in both age groups at 1 month, with a significant (p = 0.001) drop for young cattle at 6 months. Previously vaccinated adult cattle showed a longer duration of immunity at 11 months for this heterologous sheep pox vaccine. Based on these data, we advise that young cattle receive an additional booster vaccination 4-6 months after their first vaccination, and then yearly vaccinations in high-risk areas.

Evaluation of the effectiveness of foot-and-mouth disease vaccination of animals in the buffer zone of the Republic of Armenia in 2016-2020.

BACKGROUND: Foot-and-mouth disease (FMD) is a high impact viral disease of livestock for which vaccines are extensively used for limiting the spread of infection. Armenia shares a border with both Turkey and Iran where FMD is endemic, making vaccination an important component of Armenia's control strategy. Additionally, Armenian veterinary services utilize both passive and active monitoring for prevention control. METHODS: We sought to determine the immune status of animals vaccinated against FMD and to evaluate the effectiveness of our vaccination policy in Armenia. This was conducted in three regions including Shirak, Armavir, and Ararat Region which are located in the buffer zones that border Turkey and Iran. Through active monitoring in 2020, we studied blood serum samples from cattle and sheep using an enzyme immunoassay to determine the level of immune animals in these regions following the use of a polyvalent inactivated vaccine containing FMDV serotypes A, O, and Asia-1 that are relevant for this region. ELISA titers were assessed at 28, 90, and 180 days after vaccination in cattle of three age groups at the time of initial vaccination: 4-6 months, 6-18 months and ≥ 24 months of age with sheep of all ages. RESULTS: The 3 age groups of cattle had similarly high levels of immunity with over 90% of the cattle showing a ≥ 50% protective titer 28 days after the first vaccination. By day 90, titers in cattle from the initial 4-18-month age groups dropped below 58% across the 3 serotypes and at or below 80% for the oldest cattle ≥ 24 months. Re-vaccination of cattle at 120 days did improve protective titers but never reached the level of immunity of the first vaccination. Sheep showed a similar rapid drop to less than 50% having a ≥ 50% protective titer at 90 days emphasizing the need for continual revaccination. CONCLUSIONS: The results of this study have important implications for the current FMD vaccine policy in Armenia and improves our understanding of the rapid loss of protective titers over short periods. Since small ruminants are only vaccinated once per year and vaccination titers drop rapidly by 90 days suggests that they are vulnerable to FMD and that vaccination protocols need to be updated. Cattle should continue to be vaccinated every 3-6 months depending on their age to maintain a protective level of antibodies to protect them from FMD. More studies are needed to understand the possible role of small ruminants in the epidemiology of FMD and to evaluate revaccination at shorter intervals. These results show the concerns of rapid loss of protection to both cattle and small ruminants following 1 or more doses of commercial vaccines and that additional vaccines need to be evaluated in both groups to know how often they must be vaccinated to provide full protection. The addition of challenge studies should also be considered to better understand the level of protection as measured by serology and how it relates to protection from challenge. These results should be considered by anyone using these vaccines in cattle and sheep at longer than 3 month intervals.

The Serological Response in Cattle following Administration of a Heterologous Sheep Pox Virus Strain Vaccine for Protection from Lumpy Skin Disease; Current Situation in Armenia.

Lumpy skin disease (LSD) is a highly infectious viral disease of cattle caused by LSD virus (LSDV), which was first reported in Armenia in late 2015. It was identified in pasture-raised cattle near the border with Iran. Currently, vaccination plays a key role in preventing further incursion of disease in high-risk areas. The purpose of this work was to assess the quality of vaccination currently used in Armenia by determining the immune response of the heterologous dry culture sheep pox virus-based vaccine against LSD in cattle. Seroprevalence and seroconversion testing was carried out using an ELISA to detect specific antibodies against LSD before and 30 days after vaccination in three adjacent regions of Armenia (Ararat, Armavir, Gegharkunik). Ixodes ticks were also examined for the presence of LSDV via real-time PCR. We found that the heterologous vaccine used in Armenia creates a high level of population immunity of 86.09% (83.83-87.97%) and no adverse side effects were observed in cattle. Of the 6 types of Ixodes ticks identified and tested, we found no evidence of LSDV circulating in these vectors. These results suggest that regular serological monitoring via ELISA and heterologous vaccination should continue in areas of Armenia at high risk for incursion of LSD to reduce the spread of this highly infectious transboundary disease.