Foot-and-mouth disease virus O/ME-SA/Ind 2001 lineage outbreak in vaccinated Holstein Friesian cattle in Saudi Arabia in 2016

A review of foot-and-mouth disease in Ethiopia: epidemiological aspects, economic implications, and control strategies

Foot-and-mouth disease (FMD) is a contagious viral disease that affects the livelihoods and productivity of livestock farmers in endemic regions. It can infect various domestic and wild animals with cloven hooves and is caused by a virus belonging to the genus Aphthovirus and family Picornaviridae, which has seven different serotypes: A, O, C, SAT1, SAT2, SAT3, and Asia-1. This paper aims to provide a comprehensive overview of the molecular epidemiology, economic impact, diagnosis, and control measures of FMD in Ethiopia in comparison with the global situation. The genetic and antigenic diversity of FMD viruses requires a thorough understanding for developing and applying effective control strategies in endemic areas. FMD has direct and indirect economic consequences on animal production. In Ethiopia, FMD outbreaks have led to millions of USD losses due to the restriction or rejection of livestock products in the international market. Therefore, in endemic areas, disease control depends on vaccinations to prevent animals from developing clinical disease. However, in Ethiopia, due to the presence of diverse antigenic serotypes of FMD viruses, regular and extensive molecular investigation of new field isolates is necessary to perform vaccine-matching studies to evaluate the protective potential of the vaccine strain in the country.

Genetic characterization of foot-and-mouth disease virus serotype O isolates collected during 2014-2018 revealed dominance of O/ME-SA/Ind2001e and the emergence of a novel lineage in India

Foot-and-mouth disease (FMD) is endemic in India with a preponderance of outbreaks caused by FMD virus (FMDV) serotype O. Out of the 11 global topotypes of serotype O, only ME-SA topotype has been reported in the country so far. Lineage O/ME-SA/Ind2001 and O/ME-SA/PanAsia are documented as the most dominant ones in terms of the number of outbreaks caused by them. To understand the distribution of topotype/lineages in India and their antigenic behaviour during the year 2014-2018, a total of 286 FMDV serotype O viral isolates were sequence determined at the VP1 region, and 109 isolates were characterized antigenically. All the isolates grouped in the ME-SA topotype, being distributed in lineage O/ME-SA/Ind2001 (within sub-lineages O/ME-SA/Ind2001d and O/ME-SA/Ind2001e), and a new group designated here as O/ME-SA/2018 cluster. The sub-lineage O/ME-SA/Ind2001e reported for the first time in India during the year 2015, replaced sub-lineage O/ME-SA/Ind2001d gradually, which was dominating since 2008. During the years 2014-2018, the sub-lineage O/ME-SA/Ind2001e was found to be the most predominant one whose mean evolutionary rate was observed to be faster than that of the sub-lineage O/ME-SA/Ind2001d. The codon sites 45 and 85 of VP1 were found to be under diversifying selection in a large proportion of trees. The common ancestor predicted for sub-lineages O/ME-SA/Ind2001e and O/ME-SA/2018 dates back to 2012 and 2016, respectively. The sustenance and spread of the new O/ME-SA/2018 cluster need to be assessed by continued surveillance. The Indian vaccine strain O/INDR2/1975 was found to provide adequate antigenic coverage to the emerging and prevalent serotype O lineages. The trait association tests showed frequent virus exchange among different states, which could be an important confounder in the region-specific assessment of effectiveness of FMD control programme.

Early origin and global colonisation of foot-and-mouth disease virus

In this study, we compiled 84-year worth (1934-2017) of genomic and epidemiological data of foot-and-mouth disease virus (FMDV), and performed comprehensive analyses to determine its early origin and transmission route. We found that recombination is a key feature of FMDV, and that the genomic regions coding for structural and non-structural proteins have markedly different evolutionary histories, and evolve at different rates. Despite all of these differences, analyses of both structural and non-structural protein coding regions consistently suggested that the most recent common ancestor of FMDV could be dated back to the Middle Age, ~ 200 to 300 years earlier than previously thought. The ancestors of the Euro-Asiatic and SAT strains could be dated back to the mid-seventeenth century, and to the mid-fifteenth to mid-sixteenth century, respectively. Our results implicated Mediterranean counties as an early geographical origin of FMDV before spreading to Europe and subsequently to Asia and South America.

Foot-and-Mouth Disease Surveillance Using Pooled Milk on a Large-Scale Dairy Farm in an Endemic Setting

Pooled milk is used for the surveillance of several diseases of livestock. Previous studies demonstrated the detection of foot-and-mouth disease virus (FMDV) in the milk of infected animals at high dilutions, and consequently, the collection of pooled milk samples could be used to enhance FMD surveillance. This study evaluated pooled milk for FMDV surveillance on a large-scale dairy farm that experienced two FMD outbreaks caused by the A/ASIA/G-VII and O/ME-SA/Ind-2001d lineages, despite regular vaccination and strict biosecurity practices. FMDV RNA was detected in 42 (5.7%) of the 732 pooled milk samples, and typing information was concordant with diagnostic reports of clinical disease. The FMDV positive milk samples were temporally clustered around reports of new clinical cases, but with a wider distribution. For further investigation, a model was established to predict real-time RT-PCR (rRT-PCR) C_T values using individual cattle movement data, clinical disease records and virus excretion data from previous experimental studies. The model explained some of the instances where there were positive results by rRT-PCR, but no new clinical cases and suggested that subclinical infection occurred during the study period. Further studies are required to investigate the effect of vaccination on FMDV excretion in milk, and to evaluate more representative sampling methods. However, the results from this pilot study indicate that testing pooled milk by rRT-PCR may be valuable for FMD surveillance and has provided evidence of subclinical virus infection in vaccinated herds that could be important in the epidemiology of FMD in endemic countries where vaccination is used.

Serological evaluation for the current epidemic situation of foot and mouth disease among cattle and buffaloes in Egypt

AIM

The present study was aimed to investigate the epidemic situation of foot-and-mouth disease (FMD) in Egypt from 2016 to 2018 based on the detection of FMD virus (FMDV) in carrier or previously infected animals, by determination of antibodies against non-structural protein (NSP), implementation a pilot study on circulating FMDV serotypes and assure the efficacy of locally produced inactivated trivalent vaccine.

MATERIALS AND METHODS

A total of 1500 sera were collected from apparent healthy vaccinated cattle and buffaloes from three Egyptian geographical sectors, representing ten governorates. Determination of FMD antibodies against NSP was carried out using 3ABC enzyme-linked immunosorbent assay (ELISA) test. Serotyping of the circulating FMDV and assure the vaccine efficacy was performed using solid-phase competitive ELISA.

RESULTS

The 3ABC ELISA test revealed 26.4% and 23.7% positive for FMDV-NSP antibodies in cattle and buffalo sera, respectively. The highest positivity was in Delta Sector among both cattle 42.3% and buffaloes 28.8%. Serotyping of FMDV-positive NSP sera in El-Qalyubia Governorate for the circulating FMDV serotypes O, A, and Southern African Territories (SAT) 2 was 52.2%, 17.4%, and 30.4% in cattle and 31.8%, 27.3%, and 40.9% in buffaloes, respectively. The overall protection level due to the vaccination program was 62.1 and 60.9% in cattle and buffaloes, respectively, while the protective level of the FMDV serotypes O, A, and SAT2 included in the inactivated trivalent vaccine was 73.9, 84.6, and 63.8% in cattle and 72.3, 82.3, and 63.5% in buffaloes, respectively.

CONCLUSION

The present study recommended full determination for the immunogenic relationship between the vaccine strains and the field strains to attain maximum protection against the circulating viruses.