Immune Response in Goats to Two Commercial Foot-and-Mouth Disease Vaccines and the Assessment of Maternal Immunity in Their Kids

Serological Evidence of Foot-and-Mouth Disease Infection in Goats in Lao PDR

Foot and Mouth Disease (FMD) causes significant economic loss in Lao PDR (Laos) and perpetuates the cycle of smallholder poverty mainly through large ruminant productivity losses, increased costs of production and potential limitations to market access for trade in livestock and their products. Goats are emerging as an important livestock species in Laos, and there is an increasing trend in the number of households with goats, often farmed alongside cattle and buffalo. Although an FMD susceptible species, very little is known about the role of goats in the epidemiology of the disease in Laos. A cross-sectional seroprevalence study was conducted by detecting antibodies to the non-structural proteins (NSP), an indication of a previous infection, and serotype-specific structural proteins (SP) that could be due to vaccination or infection. The study commenced in late 2017 and sera were collected from 591 goats in 26 villages of northern, central and southern Laos. For a subset of sera samples, paired oral swab samples were also collected by a simple random sampling method to detect the prevalence of FMD virus infection at the time of collection. The NSP seroprevalence in the provinces of Borkeo and Xayabouli in the north was 42 and 8%, respectively and in Khammoune in the center, it was 20%. In the other five provinces, Luang Namtha and Luang Prabang (northern Laos), Xieng Khouang and Savannaket (central Laos), and Champasak (southern Laos), the seroprevalence was close to zero. The multivariable analysis indicated that age (p < 0.001) was positively associated with animal-level seropositivity and males were less likely to be seropositive than females (OR: 0.29; 95%CI: 0.10–0.83; p = 0.017). Continued sero-surveillance for FMD in goats is recommended to improve our understanding of their role in the epidemiology of FMD in the region and to extend support to FMD control decisions, particularly regarding vaccination.

Experimental Infection of Foot and Mouth Disease in Indian Sheep and Goats

Foot-and-mouth disease (FMD) is an economically important contagious disease of livestock mainly cattle, buffalo, sheep, goats, and pig. There is limited data available on pathogenesis of foot and mouth disease in goats. In the study, the sheep and goats were infected experimentally with a serotype O foot-and-mouth disease virus by different challenge routes. The sheep and goats challenged by coronary band route and coronary band and intra-dermo-lingual route exhibited FMD clinical signs at 2-5 days post challenge. Whereas intra-dermo-lingual challenged sheep and goats did not exhibit FMD clinical signs. Live virus could be isolated from blood of infected sheep and goats at 2-5 days post challenge. Viral RNA could be detected from blood of infected sheep and goats at 1-10 days post challenge. The neutralizing antibody titre was detected at 10 days post challenge and maintained up to 35 days post challenge in all infected sheep and goats. Non structural protein (NSP) antibodies were detected as early as 5-10 days post challenge and remain positive up to 35 days post challenge in the infected sheep and goats. In conclusion, the pathogenesis of sheep and goats with serotype O foot and mouth disease virus by different challenge routes could be demonstrated.

Efficacy of a foot-and-mouth disease vaccine against a heterologous SAT1 virus challenge in goats

Goats are susceptible to infection with foot-and-mouth disease virus (FMDV), but their role in the epidemiology of the disease and response to vaccination is poorly understood. In southern Africa, FMDV serotypes Southern African Territories (SAT) 1, 2 and 3 are known to be endemic. In this study, we evaluated the efficacy of a pentavalent FMD vaccine in goats against heterologous challenge with a pool of field SAT1 FMDV. Forty FMD sero-negative goats (6-12 months of age) of mixed sexes were randomly allocated to one of five treatment groups: full cattle dose (2 ml), 1/3rd (0.67 ml), 1/6th (0.33 ml), 1/12th (0.16 ml) or unvaccinated placebo control. Goats were vaccinated with an inactivated pentavalent FMD vaccine containing serotypes SAT1, SAT2 and SAT3 on day 0 and revaccinated at day 20 post vaccination. Thereafter, thirty-four goats were challenged by tongue inoculation at day 41 post-vaccination using 10^4.57 50% tissue culture infective dose (TCID₅₀) FMDV SAT1 pool. Animals were examined daily and clinical signs were scored. Rectal temperatures were measured daily, with temperatures ≥40 °C defined as fever. Clinical specimens (nasal, oral and rectal swabs) were collected on days 0, 2, 4 and 6 post challenge. Viral shedding was determined using reverse-transcriptase real-time PCR. None of the goats vaccinated with the full cattle dose developed secondary lesions. All vaccinated groups had lower temperatures compared to the unvaccinated controls (P < 0.001). Based on RT-PCR results, goats in the unvaccinated control group shed more virus compared to all groups except for 1/12th (P < 0.05), while goats in the full dose group shed less virus than goats in the 1/12th and the unvaccinated control group (P < 0.05). The results suggest that the 1/3rd (0.67 ml) dose of the vaccine is sufficient to reduce viral shedding after heterologous challenge with a FMDV SAT1 pool.

Serological response against foot-and-mouth disease virus to FMD-haemorrhagic septicaemia-black quarter combined vaccine and FMD vaccine alone in sheep and goat

Foot-and-mouth disease is subclinical in small ruminants and they may play role in spread of disease. Presently, they are not included in vaccination coverage in India under FMD-control programme. A total of 43 animals including sheep (16) and goat (27) were used for vaccination study by combined vaccine (FMD, HS and BQ) and FMD vaccine alone. Humoral immune response was evaluated by monitoring serum antibody titres against FMDV serotypes O, A and Asia 1 on 30, 60, 90 dpv. In both vaccinated groups, peak antibody titre for all 3 serotypes was obtained on 30 dpv, it remained constant up to day 60 and after that there was gradual decrease at 90 dpv. As in both groups there was no significant difference and protective titre remained upto 90 dpv, use of combined vaccine can be suggested as cost effective strategy.

Effect of FMD vaccination schedule of dams on the level and duration of maternally derived antibodies

Vaccination against Foot and Mouth Disease (FMD) in pregnant cows is crucial to produce greater immunity in new born calves, especially in late gestation, as this directly affects neonatal immunity. Therefore, we aimed to investigate how late gestation FMD vaccination of pregnant cows affects the maternally derived antibodies in their offspring. Pregnant cows were vaccinated with and without booster vaccination during the 3rd months (early gestation vaccination, EGV) or the 6.5th months (late gestation vaccination, LGV). Their offspring were investigated for passive immunity transfer, maternal antibody duration, and the first vaccination age of calves (when the maternal antibody has waned sufficiently to allow the first vaccination). Antibody titers were analyzed by a virus neutralization test (VNT). A digital Brix refractometer (% Brix) was used to estimate passive antibody transfer efficiency measuring total protein (TP) content of calf blood sera and also colostrum IgG content. Two linear mixed effects models were fitted: one for the antibody titer values of the dams, and the other for the antibody titer values of calves before the vaccination. A marginal fixed effects model was also fitted to explore the effects of the dam titers on the antibody titers of the calves after their vaccinations. As a result, the average neutralizing antibody titers did not differ between the EGV and LGV groups nor were any differences detected between dams that received a booster and those that were not boosted. However, the LGV calves' mean maternally derived antibody titers were significantly higher (p-values = 0.0001 for both groups) and the duration was longer than that of the EGV calves (120 days in LGV, 60 days in EGV, p < 0.05). Since no statistical difference was found between the titers of either group of dams at the beginning of the experiment and parturition, it does not appear that the higher VN titers in LGV calves compared to titers in EGV are directly related to the circulating antibody levels in the dams. Furthermore, the TP value (% Brix) of calf blood sera was higher than>8.4% in both calf groups (9.3 ± 0.33 in LGV and 8.6 ± 0.40 in EGV, p > 0.05) indicating that passive immunity transfer had occurred for both groups. In addition, we found that the % Brix mean colostrum IgG content of the LGV (25.8 ± 1.30) was higher than the EGV (21.8 ± 0.58) dams (p < 0.01) and a significant positive correlation found between the colostrum density of LGV dams and TP (% Brix) value of their offspring (r = 0.73, p < 0.01). Our results show that vaccination during the late gestation period increased the colostrum IgG content of dams of LGV in addition to the maternally derived antibody duration and potentially provided greater protection of the offspring.

Serosurveillance of foot-and-mouth disease in sheep and goat population of India

Serological investigation to detect foot-and-mouth disease (FMD) virus circulation in the domestic small ruminant population of India was conducted. A total of 4407 and 4035 serum samples from sheep and goats, respectively were collected at random covering majority of the states across the country during 2010-2012. These samples were analyzed for antibodies against the non-structural proteins (NSP) of FMD virus in an indirect 3AB NSP ELISA and against the structural proteins (SP) in a liquid phase blocking (LPB) ELISA. A total of 20.35% sheep and 13.60% goats were found to be positive for 3AB NSP antibodies providing a serological evidence of extensive viral activity. In LPB ELISA, only 4.54% sheep and 6.27% goats were found to have protective antibody (log10 titre of ≥1.8) against all three serotype strains in the vaccine, which correlates with "no or sparse vaccination" scenario in these species in the country. Hence, to check silent amplification and dissemination of virus in a mixed farming set up, small ruminants may be brought under the ambit of routine vaccination and surveillance programmes.

Clinical protection, sub-clinical infection and persistence following vaccination with extinction payloads of O1 Manisa Foot-and-Mouth Disease monovalent vaccine and challenge in goats and comparison with sheep

Small ruminants play an important role in the epidemiology of Foot-and-Mouth Disease (FMD). Small ruminants are vaccinated with one-half or one-third of cattle dose of oil-based or aqueous vaccines respectively. The extinction antigen payload in vaccine for protection in small ruminants is poorly studied. FMD seronegative Nellore sheep (n=30) and Osmanabadi goats (n=30) were vaccinated with different payloads of O(1) Manisa vaccine (0.45-5 μg). Vaccinated and sero-negative unvaccinated sheep (n=6) and goats (n=6) were challenged intradermally into the coronary band with O(1) Manisa virus. The sheep and goats were monitored for signs of FMD and samples were collected for measuring viraemia and virus associated with nasal swabs and probang samples. Clotted blood was collected for serology. Vaccines containing antigen payload up to 0.94 μg protected sheep and goats against challenge. Sheep and goats vaccinated with 0.45 μg antigen payload were poorly protected against challenge. An antigen payload of 0.94 μg was sufficient to offer complete protection and also absence of carrier status. Sheep and goats with no vaccination or with poor sero conversion to vaccination showed sub-clinical infection and became carriers. The results of the study suggest that vaccination offers protection from clinical disease even at a low payload of 0.94 μg and hence one-half of cattle dose of the oil-based vaccine formulations is sufficient to induce protective immune response in sheep and goats. Since no live virus could be isolated after 5 days post challenge from the nasal swab or probang samples even though viral RNA was detected, the risk of these animals transmitting disease was probably very low.

Recombinant pseudorabies virus expressing P12A and 3C of FMDV can partially protect piglets against FMDV challenge

One of the crucial factors for evaluation of an effective genetically engineered vaccine is whether susceptible animals are protected from virus challenge after vaccination. In this study, a recombinant pseudorabies virus (PRV-P12A3C) that expressed capsid precursor polypeptide P12A and nonstructural protein 3C of foot-and-mouth disease virus (FMDV) was used as a vaccine. The expression of P12A3C and its immunogenicity and protective efficacy against FMDV challenge were measured. Humoral and cellular immune responses were evaluated after each immunization. Subsequently, each piglet was challenged with 1000 ID(50) (50% infection dose) FMDV serotype O, named OR/80, which is used to produce vaccine in China. PRV-P12A3C induced a high level of neutralizing antibody and FMDV-specific lymphocytes. Inactivated vaccine provided 100% protection, and the vector strain (TK(-)/gE(-)/gI(-)) showed no protection. PRV-P12A3C induced 60% protection, compared with piglets that were vaccinated with TK(-)/gE(-)/gI(-). The severity of clinical signs for the remaining two piglets was lighter and the appearance of vesicles was delayed.

Immune Response in Goats to Different Payloads of FMDV Monovalent Vaccine: Protection Against Virulent Challenge and Development of Carrier Status

The relationship of Foot-and-Mouth Disease virus antigen payload and number of dose of vaccine conferring protection against virus challenge in goats was studied. Goats vaccinated with oil adjuvant Foot-and-Mouth Disease vaccines containing different antigen payloads with or without booster resisted virulent challenge at 21 days post-vaccination or 7 days after booster respectively. However, localized sub-clinical infection was observed in two vaccinated goats on 35 days post-challenge. RNA could be detected from 31.8% of vaccinated goats (10(2.69)-10(4.99) viral RNA copies per cotton swab of nasal secretions) on day 35 post-challenge. Since no live virus could be isolated after 5 days post-challenge, the risk of these animals transmitting the disease was probably very low. The finding showed that oil adjuvant Foot-and-Mouth Disease vaccines containing antigen payload of 1.88 μg may prevent or reduce the local virus replication at the oropharynx and shedding of virus from nasal secretions and thereby reduce the amount of virus released into the environment subsequent to exposure to live virus. This study also showed that goats with poor sero conversion to vaccination can be infected without overt clinical signs and became carriers like sheep.