Transmission of foot-and-mouth disease virus from experimentally infected Indian buffalo (Bubalus bubalis) to in-contact naïve and vaccinated Indian buffalo and cattle

Kinetics of foot-and-mouth disease vaccine-induced antibody responses in buffaloes (Bubalus bubalis): avidity ELISA as an alternative to the virus neutralization test

The role of water buffaloes in foot-and-mouth disease (FMD) epidemiology as one of the major hosts of the virus that can develop persistent asymptomatic infection highlights the importance of sustaining surveillance on the antibody response elicited by vaccination in these animals. There is gap in the knowledge on how serological assays that measure antibodies against capsid proteins perform with buffalo samples and which would be the most reliable test to substitute the virus neutralization test (VNT) a cumbersome and low-throughput tool for field surveillance. Alternatively, the liquid-phase blocking sandwich ELISA (LPBE) is commonly used. Previous data from our laboratory demonstrated that the vaccine-induced antibodies assessed by the LPBE yielded low specificity with buffaloes' samples. In contrast, a single-dilution avidity ELISA (AE) aimed to detect high-avidity antibodies against exposed epitopes, combined with an indirect ELISA (IE) to assess IgG levels, produced more reliable results. Here we analyzed for the first time the kinetics of the antibodies induced by vaccination in two different buffalo herds (n = 91) over 120 days using AE, IE, LPBE, and the VNT. Kinetics were similar in the different assays, with an increase of antibodies between 0- and 14-days post-vaccination (dpv) which were maintained thereafter. VNT and AE results were concordant (Kappa value = 0.76), and both assays revealed a decay in the antibody response in calves with maternal antibodies at 90 and 120 dpv, which was not evidenced by the LPBE. These results show that kinetics of antibody responses to FMD vaccination are similar in buffalo and cattle, and support the use of indirect ELISA assays, in particular Avidity ELISA, as alternatives to the VNT for vaccine-immunity monitoring irrespectively of the animal's passive or active immune status.

Viral dynamics and immune responses to foot-and-mouth disease virus in African buffalo (Syncerus caffer)

Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While African buffalo (Syncerus caffer) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle inoculation and contact infections with three Southern African Territories serotypes to assess clinical, virological and immunological dynamics for thirty days post infection. Clinical FMD in the needle inoculated buffalo was mild and characterised by pyrexia. Despite the absence of generalised vesicles, all contact animals were readily infected with their respective serotypes within the first two to nine days after being mixed with needle challenged buffalo. Irrespective of the route of infection or serotype, there were positive associations between the viral loads in blood and the induction of host innate pro-inflammatory cytokines and acute phase proteins. Viral loads in blood and tonsil swabs were tightly correlated during the acute phase of the infection, however, viraemia significantly declined after a peak at four days post-infection (dpi), which correlated with the presence of detectable neutralising antibodies. In contrast, infectious virus was isolated in the tonsil swabs until the last sampling point (30 dpi) in most animals. The pattern of virus detection in serum and tonsil swabs was similar for all three serotypes in the direct challenged and contact challenged animals. We have demonstrated for the first time that African buffalo are indeed systemically affected by FMD virus and clinical FMD in buffalo is characterized by a transient pyrexia. Despite the lack of FMD lesions, infection of African buffalo was characterised by high viral loads in blood and oropharynx, rapid and strong host innate and adaptive immune responses and high transmissibility.

Socioeconomic impacts of clinical foot-and-mouth disease and a risk-based partial vaccination campaign for smallholders in Lao People's Democratic Republic

Foot-and-mouth disease (FMD) is endemic in Lao People's Democratic Republic (PDR). A risk-based partial vaccination campaign was implemented in Champasak, Savannakhet and Xiengkhouang Provinces in Lao PDR in 2016-20, which had limited effects on reducing the circulation of FMD virus. The objectives of this study were to measure the socioeconomic effects of (i) a clinical FMD occurrence and (ii) the vaccination campaign on livestock production performance of smallholders in Lao PDR in 2016-2020. Two questionnaire surveys were conducted at the beginning (2016) and the end (2020) of the campaign, involving 1,609 smallholders in 160 villages comparing areas with and without FMD control. Mixed-effect multivariable regression models were fitted to measure the association between livestock production parameters at the household level (rates of birth, sale, purchase, and death, sale price, costs, gross gains and net gains) and (i) a clinical FMD occurrence and (ii) the vaccination campaign, while adjusting for village, herd size, province, vaccination status and FMD knowledge. We found no significant difference in annual household-level costs, gains and net gains by due absence of FMD. However, smallholders with FMD had a 52% higher cattle death rate, a 43% lower goat sale rate and a 78% lower pig sale price than those without FMD. Smallholders with FMD also had a lower purchase rate of livestock (cattle -15% and pigs -93%) compared with those without FMD. There was a general improvement in livestock production in target villages over the five years of the vaccination campaign, whereas there was an overall decline in non-target villages, resulting in USD 218 higher net gains in target villages in 2020 compared with non-target villages, possibly due to reduced severity of disease and improved awareness on FMD and general livestock health. The findings of this study will help improve strategies for sustainable and efficient FMD control in Lao PDR, while the challenges and importance of gaining participation by smallholders are highlighted. This article is protected by copyright. All rights reserved.

Temporal patterns and space-time cluster analysis of foot-and-mouth disease (FMD) cases from 2007 to 2017 in Vietnam

In Vietnam, Foot‐and‐mouth disease (FMD) is endemic, but no nationwide studies have been conducted to assess the monthly variations and space‐time clusters of FMD. The main objective was to identify the temporal patterns and space‐time clusters of FMD from 2007 to 2017 using national surveillance data in Vietnam. A total of 163,733 cases were reported from 2007 to 2017. Among them, the proportion of buffaloes (43.31% of total reported cases; 70,909 cases) was highest followed by cattle (30.11%; 49,306 cases), pigs (26.67%; 43,662 cases) and sheep/goats (0.41%; 675 cases). The serotype O was widely distributed across the country while serotype A was observed in Northeast, Central and Southern part of Vietnam while Asia 1 has been not identified since 2007. For monthly variations, most cases were observed during the dry season (from November to March) except Central Highlands. Under the spatial window was set at 50%, a total of seven clusters were identified. The primary cluster was observed from Dec 2009 to Dec 2010 in the northwest (radius: 101.67 km), showing a ratio of 3.75. The secondary cluster was detected in the northeast region (radius: 76.54 km) with a ratio of 3.53 in Feb 2017. The 3rd cluster was the largest with a radius of 176.69 km and located in the southern part of Vietnam. Interestingly, the most temporal clusters included between December and March during the study period. Our findings provide better insight into the temporal patterns and distribution of clusters of FMD in Vietnam. This study provides useful information to policymakers on the hotspot areas and timing of outbreaks. It also identifies when and where national surveillance and control programmes could be implemented more efficiently for the prevention and control of FMD.

Knowledge and behavior of cattle and sheep owners and herders regarding foot-and-mouth disease in Northern Algeria

Background and Aim:

Foot-and-mouth disease (FMD) has been occurring in Algeria since 2014, when an outbreak was announced in Setif, a district in the eastern region of the country. The problem was apparently resolved with the help of vaccination. However, in 2015, 2016, and 2018, FMD recurred. The veterinary authorities and media educated breeders on how to recognize the clinical signs and how to report the disease. This study aimed to evaluate the knowledge and recognition of FMD by farmers and breeders. Moreover, an assessment of the behavior of cattle and sheep owners and herders following FMD cases is examined.

Materials and Methods:

A cross-sectional survey was conducted from June to October 2018 to evaluate the perception of cattle and sheep owners and breeders regarding FMD in the Northern regions of Algeria, using questionnaires.

Results:

One hundred questionnaires were distributed; 71 were collected. Data showed that all the responders claimed to know about the disease, while more than half of the owners/herders claimed that they knew the clinical symptoms of FMD and mentioned fever, hypersalivation, lameness, and vesicles. Fewer than half (42%) (30/71) took some measures to prevent the disease, while more than half (58%) (41/71) did not take any measures in 2018. No one claimed to have reported the disease to authorities in 2018, while more than half had done so in 2014.

Conclusion:

It appears that experienced farmers recognized the clinical signs of FMD, while an academic background was not conclusively necessary for the identification of the clinical signs of the disease. Concerning the assessment of risk-associated behavior in the event of FMD occurrence, the responses of the breeders were not significantly different from those of risk-associated behaviors in the event of an epidemic. Farmers and breeders expressed similarity in terms of communicating the appearance of the disease in their livestock; the majority of them seemed to be aware of the importance of reporting the disease to local authorities, especially in 2014, when the disease first occurred. This behavior is encouraged by refund and technical assistance policies by the veterinary authorities, but in 2018, no disease was reported due to fear of slaughtering and economic loss.

Efficacy of an adenovirus-vectored foot-and-mouth disease virus serotype A subunit vaccine in cattle using a direct contact transmission model

BACKGROUND

A direct contact transmission challenge model was used to simulate natural foot-and-mouth disease virus (FMDV) spread from FMDV A24/Cruzeiro/BRA/55 infected 'seeder' steers to naïve or vaccinated steers previously immunized with a replication-deficient human adenovirus-vectored FMDV A24/Cruzeiro/BRA/55 capsid-based subunit vaccine (AdtA24). In two independent vaccine efficacy trials, AdtA24 was administered once intramuscularly in the neck 7 days prior to contact with FMDV A24/Cruzeiro/BRA/55-infected seeder steers.

RESULTS

In Efficacy Study 1, we evaluated three doses of AdtA24 to estimate the 50%/90% bovine protective dose (BPD50/90) for prevention of clinical FMD. In vaccinated, contact-challenged steers, the BPD50/90 was 3.1 × 1010 / 5.5 × 1010 AdtA24 particles formulated without adjuvant. In Efficacy Study 2, steers vaccinated with 5 × 1010 AdtA24 particles, exposed to FMDV A24/Cruzeiro/BRA/55-infected seeder steers, did not develop clinical FMD or transmit FMDV to other vaccinated or naïve, non-vaccinated steers. In contrast, naïve, non-vaccinated steers that were subsequently exposed to FMDV A24/Cruzeiro/BRA/55-infected seeder steers developed clinical FMD and transmitted FMDV by contact to additional naïve, non-vaccinated steers. The AdtA24 vaccine differentiated infected from vaccinated animals (DIVA) because no antibodies to FMDV nonstructural proteins were detected prior to FMDV exposure.

CONCLUSIONS

A single dose of the AdtA24 non-adjuvanted vaccine conferred protection against clinical FMD at 7 days post-vaccination following direct contact transmission from FMDV-infected, naïve, non-vaccinated steers. The AdtA24 vaccine was effective in preventing FMDV transmission from homologous challenged, contact-exposed, AdtA24-vaccinated, protected steers to co-mingled, susceptible steers, suggesting that the vaccine may be beneficial in reducing both the magnitude and duration of a FMDV outbreak in a commercial cattle production setting.

Phylodynamics of foot-and-mouth disease virus O/PanAsia in Vietnam 2010-2014

Foot-and-mouth disease virus (FMDV) is endemic in Vietnam, a country that plays an important role in livestock trade within Southeast Asia. The large populations of FMDV-susceptible species in Vietnam are important components of food production and of the national livelihood. In this study, we investigated the phylogeny of FMDV O/PanAsia in Vietnam, reconstructing the virus' ancestral host species (pig, cattle or buffalo), clinical stage (subclinical carrier or clinically affected) and geographical location. Phylogenetic divergence time estimation and character state reconstruction analyses suggest that movement of viruses between species differ. While inferred transmissions from cattle to buffalo and pigs and from pigs to cattle are well supported, transmission from buffalo to other species, and from pigs to buffalo may be less frequent. Geographical movements of FMDV O/PanAsia virus appears to occur in all directions within the country, with the South Central Coast and the Northeast regions playing a more important role in FMDV O/PanAsia spread. Genetic selection of variants with changes at specific sites within FMDV VP1 coding region was different depending on host groups analyzed. The overall ratio of non-synonymous to synonymous nucleotide changes was greater in pigs compared to cattle and buffalo, whereas a higher number of individual amino acid sites under positive selection were detected in persistently infected, subclinical animals compared to viruses collected from clinically diseased animals. These results provide novel insights to understand FMDV evolution and its association with viral spread within endemic countries. These findings may support animal health organizations in their endeavor to design animal disease control strategies in response to outbreaks.

Molecular investigation of foot-and-mouth disease virus in domestic bovids from Gharbia, Egypt

An outbreak of foot-and-mouth disease (FMD) affecting cattle and water buffalo (Bubalus bubalis) occurred in Egypt during 2012/2013. The present study was undertaken to determine the current strains of the FMD virus (FMDV) and the prevalence of FMD among cattle and buffalo in Gharbia, Egypt. The diagnostic sensitivity of two RT-PCR assays for the detection of FMDV was evaluated. The results revealed that SAT2 was the causative agent. The percentage of infected of animals varied with the detection method, ranging from 62.5 % by the untranslated region (UTR) RT-PCR to 75.6 % by SAT2 RT-PCR. The overall prevalence and mortality rates were 100 and 21 %, respectively. The mortality was higher in buffalo (23.3 %) than it was in cattle (17 %). A partial sequence of SAT2 was identical (90-100 %) to Egyptian isolates and was close in similarity to sequences from Sudan and Libya. In conclusion, FMD in Egypt is caused by SAT2. No other serotypes were detected. The results of this study provided the valuable data regarding the epidemiology of SAT2 in cattle and water buffalo from Egypt, which strengthens the need to change the strategies of both control and prevention that help to prevent the spread of the disease.