Exploiting serological data to understand the epidemiology of foot-and-mouth disease virus serotypes circulating in Libya

The first evidence of bovine viral diarrhea virus circulation in Libya

Background and Aim

Bovine viral diarrhea (BVD) is endemic in North Africa and the Mediterranean Basin with high socioeconomic impacts. However, there are no data on this disease in Libya. One of the aims of this study was to provide data on BVD in Libya, to fill in the gap in the region and to investigate the level of seroprevalence of BVD virus (BVDV) in Libya and associated risk factors.

Material and Methods

A total of 1599 serum samples were collected from cattle herds belonging to seven Libyan regions. All sera were assayed using a screening enzyme-linked immunosorbent assay for the detection of antibodies against BVDV.

Results

The overall seroprevalence of BVDV was estimated to be 48.6% (95% confidence interval, 46.08%-50.98%). A seroprevalence rate of 36.8% was detected in cattle aged <1 year, 41.0% in cattle aged between 1 and 2 years, and 49.7% in cattle aged >2 years. Statistically significant differences (p = 0.001) were observed between age groups. BVDV seroprevalence was significantly associated with geographical region (p = 0.033).

Conclusion

To the best of our knowledge, this is the first study on BVD in Libya, and the results suggest that BVD is endemic in Libya. Further studies are required to isolate and characterize the circulated BVDV in Libya.

Seroprevalence of antibodies to non-structural protein of foot-and-mouth disease virus in vaccinated dairy cattle

Foot-and-mouth disease (FMD), a highly contagious viral disease of livestock, is endemic in Iran. To investigate the prevalence of antibodies against 3ABC non-structural protein (NSP) of FMD virus, a cross-sectional study was conducted on dairy cattle in eight cities of Kurdistan Province from May to September 2016. Serum samples (n = 283), were collected from cattle vaccinated with the recommended dose of a commercial vaccine and tested by a Competition enzyme-linked immunosorbent assay. Results showed the overall seroprevalence of antibodies against NSP of FMD virus in the vaccinated cattle was 22.30% (95.00% CI: 17.40 - 27.20%). The seroprevalence of antibodies was affected by geographical regions, with the highest seroprevalence related to the samples of vaccinated cattle in the cities of Marivan 95.00% (95.00% CI: 92.50 - 97.50%) and Saqqez 38.50% (95.00% CI: 32.80 - 44.20%). In terms of age, the highest seroprevalence of antibodies to FMD virus 26.70% (95.00% CI: 21.60-31.80%) belonged to ≤ 24-month-old cattle. These findings suggest that the presence of NSP antibodies in vaccinated cattle indicates the risk of infection with FMD virus serotypes circulating in the west of the province, so further studies with a larger sample size are recommended.

FTA Cards as a Rapid Tool for Collection and Transport of Infective Samples: Experience with Foot-and-Mouth Disease Virus in Libya

Foot-and-mouth disease (FMD) is a viral disease, widespread and highly contagious, that mainly affects cloven-hoofed domestic and wild animals. FMD can lead to high economic losses due to the reduction in animal production such as a drop in milk production, loss of body weight, and a high mortality rate in young ruminants. Sixteen samples were collected from animals showing typical clinical signs of FMD during the last FMD outbreak in Libya in 2018-2019. Flinders Technology Associates (FTA) cards impressed with blood, swabs, or vesicular epithelium samples were shipped to the WOAH FMD reference laboratory in Brescia, Italy, and tested for the detection of FMD viruses. Nucleic acids were extracted from the FTA cards, and molecular testing based on real-time RT-PCR assays was carried out, of which one was specifically designed for the detection of the FMD virus of serotype O, topotype O/East Africa-3 (O/EA-3), that was further confirmed by a sequence analysis of the VP1 gene. The phylogenetic analysis of the VP1 gene showed a nucleotide identity of more than 99% between the virus circulating in Libya and the FMD virus strains isolated in Algeria in 2019.

Rift valley fever in Africa with the emerging interest in Libya

Rift valley fever (RVF) is an acute vector-borne viral zoonotic disease of domestic and wild ruminants. The RVF virus (RVFV) belonging to the Phlebovirus genus of the Bunyaviridae family causes this disease. Studies have shown that mosquitoes are the vectors that transmit RVFV. Specifically, Aedes and Culex mosquito species are among the many vectors of this virus, which affects not only sheep, goats, buffalo, cattle, and camels but also human beings. Since the 30s of the last century, RVF struck Africa, and to a lesser extent, Asian continents, with subsequent episodes of epizootic, epidemic, and sporadic outbreaks. These outbreaks, therefore, resulted in the cumulative loss of thousands of human lives, thereby disrupting the livestock market or only those with seropositive cases. After that outbreak episode, RVF was not reported in Libya until January 13, 2020, where it was reported for the 1st time in a flock of sheep and goats in the southern region of the country. Although insufficient evidence to support RVF clinical cases among the confirmed seropositive animals exists, neither human cases nor death were reported in Libya. Yet, the overtime expansion of RVF kinetics in the Libyan neighborhoods, in addition to the instability and security vacuum experienced in the country, lack of outbreak preparedness, and the availability of suitable climatic and disease vector factors, makes this country a possible future scene candidate for RVF expansion. Urgently, strengthening veterinary services (VS) and laboratory diagnostic capacities, including improvement of monitoring and surveillance activity programs, should be implemented in areas at risk (where imported animals crossing borders from Libyan neighborhoods and competent vectors are found) at national, sub-national, and regional levels. The Libyan government should also implement a tripartite framework (one health approach) among the veterinary public health, public health authority, and environmental sanitation sectors to implement RVF surveillance protocols, along with an active partnership with competent international bodies (OIE, FAO, and WHO). Therefore, this review comprises the most updated data regarding the epidemiological situation of RVF infections and its socioeconomic impacts on African and Asian continents, and also emphasize the emerging interest of RVF in Libya.

Epidemiological study on foot-and-mouth disease in small ruminants: Sero-prevalence and risk factor assessment in Kenya

Foot-and-mouth disease (FMD) is endemic in Kenya affecting cloven-hoofed ruminants. The epidemiology of the disease in small ruminants (SR) in Kenya is not documented. We carried out a cross-sectional study, the first in Kenya, to estimate the sero-prevalence of FMD in SR and the associated risk factors nationally. Selection of animals to be sampled used a multistage cluster sampling approach. Serum samples totaling 7564 were screened for FMD antibodies of non-structural-proteins using ID Screen^® NSP Competition ELISA kit. To identify the risk factors, generalized linear mixed effects (GLMM) logistic regression analysis with county and villages as random effect variables was used. The country animal level sero-prevalence was 22.5% (95% CI: 22.3%-24.3%) while herd level sero-prevalence was 77.6% (95% CI: 73.9%-80.9%). The risk factor that was significantly positively associated with FMD sero-positivity in SR was multipurpose production type (OR = 1.307; p = 0.042). The risk factors that were significantly negatively associated with FMD sero-positivity were male sex (OR = 0.796; p = 0.007), young age (OR = 0.470; p = 0.010), and sedentary production zone (OR = 0.324; p<0.001). There were no statistically significant intra class correlations among the random effect variables but interactions between age and sex variables among the studied animals were statistically significant (p = 0.019). This study showed that there may be widespread undetected virus circulation in SR indicated by the near ubiquitous spatial distribution of significant FMD sero-positivity in the country. Strengthening of risk-based FMD surveillance in small ruminants is recommended. Adjustment of husbandry practices to control FMD in SR and in-contact species is suggested. Cross-transmission of FMD and more risk factors need to be researched.

Detection of Foot-and-Mouth Disease Virus in the Absence of Clinical Disease in Cattle and Buffalo in South East Asia

Foot-and-mouth disease virus (FMDV) is widespread throughout much of the world, including parts of South East Asia. Surveillance is often limited in endemic areas, relying predominantly on passive outbreak reporting. As part of the World Organisation for Animal Health (OIE)'s South East Asia and China Foot-and-Mouth Disease Project (SEACFMD), field sampling was performed to help understand evidence of widespread virus exposure observed in previous studies. Serum and dry mucosal swabs were collected to evaluate the presence of FMDV RNA on the nasal, oral, and dorsal nasopharyngeal mucosal surfaces of 262 healthy cattle (n = 84 in Laos; n = 125 in Myanmar) and buffalo (n = 48 in Laos; n = 5 in Myanmar) immediately following slaughter in three slaughterhouses. Swabs and serum were tested by the OIE/FAO World Reference Laboratory for foot-and-mouth disease (WRLFMD) using pan-serotypic real-time reverse transcription-PCR (rRT-PCR) and serum was evaluated using the FMD PrioCHECK non-structural protein (NSP) ELISA. In total, 7.3% of animals had detectable FMDV RNA in one or more of the three sites including 5.3% of nasopharyngeal swabs, 2.3% of oral swabs, and 1.5% of nasal swabs. No FMDV RNA was detected in serum. Overall, 37.8% of animals were positive for NSP antibodies, indicating likely past natural exposure to FMDV. Results were comparable for Laos and Myanmar, and for both cattle and buffalo, and were not significantly different between age groups. Detectable FMDV RNA present on the oral and nasal mucosa of clinically-healthy large ruminants in Laos and Myanmar demonstrates the importance of sampling asymptomatic animals as part of surveillance, and may indicate that subclinical infection plays a role in the epidemiology of FMD in these countries.

Are Epitopic Sites of 3AB and 3D Nonstructural Proteins Sufficient for Detection of Foot and Mouth Disease?

An efficient method for detection of foot and mouth disease (FMD) and, particularly, differentiation of vaccinated from infected animals is the use of nonstructural (NS) proteins as antigens in Enzyme-Linked Immunosorbent Assay (ELISA) Kits. In this study, only epitopic regions of 3AB and 3D NS proteins were used for recombinant protein production, as a cost-effective method instead of peptide synthesis, for application in in-house ELISA diagnostic kits. Specific primers were designed according to the antigenic regions of 3AB (C-terminus of 3A and the whole 3B) and 3D (N-terminus) proteins, and the polymerase chain reaction (PCR) amplification was performed. Purified amplicons were cloned into pET21a (+) vectors and then transformed into Escherichia coli (BL21). Thereafter, bacteria were induced with 1 mM isopropyl β-d-1-thiogalactopyranoside (IPTG) for expression of antigenic proteins. Antigenic 3AB protein was expressed in soluble form, but 3D protein was extracted from the bacterial lysate. Protein expression was confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses. An indirect ELISA was developed for each protein, and the diagnostic sensitivity and specificity were determined. The 3AB-ELISA showed higher sensitivity and specificity than 3D-ELISA (95.24% and 100%, compared with 90.48% and 88.71%, respectively). The epitopic 3AB-ELISA developed here can be used for detection and differentiation of FMD infected from vaccinated animals, but the epitopic 3D-ELISA showed lower efficiency in screening for FMD status.

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.

Seroepidemiology of foot and mouth disease (FMD) virus non-structural protein (NSP) antibodies in the livestock of Oman

Foot and mouth disease (FMD) is a highly contagious acute viral disease that causes severe economic losses to the affected countries. To estimate the serological prevalence of the local livestock to the natural infection with FMD virus, a cross-sectional study was conducted from 2015 to 2017 in Oman. Sera from 5807 randomly selected animals (1792 cattle, 2119 goats and 1896 sheep) belonging to 884 herds were tested for the presence of antibodies against 3ABC non-structural protein (NSP) of the FMD virus by a Competition ELISA. Prevalence along with confidence intervals (CI) and odds ratio (OR) was calculated, and the data were further analysed through univariable and multivariable techniques. The herd-level seroprevalence of NSP (41.4%) varied significantly among 11 governorates of Oman. At herd-level seroprevalence varied significantly among cattle (55.2%), goats (38.2%) and sheep (37.7%). At animal-level, the significantly higher prevalence was recorded in cattle (26.8%) followed by sheep (17.9%) and goats (17.3%). Binary logistic regression analysis at the individual level indicated that cattle (OR: 1.88), livestock above one year of age (OR: 3.47), imported breeds (OR: 1.82) and females (OR: 1.27) were the risk factors associated with higher prevalence. Whereas, sedentary (OR: 2.63) farming system, vaccination against FMD (OR: 5.98) and previous history of FMD (OR: 5.55) were the variables found associated with higher seroprevalence at the herd-level. We conclude that natural infection of FMDV is widespread in Oman and in future molecular typing of FMD virus outbreaks strains and vaccine matching studies should be employed to develop an effective control program in Oman.

Seroprevalence of some Infectious transboundry diseases in cattle imported from Sudan to Egypt

OBJECTIVE

Animal trade has an important role in the economy but in contrast, it causes the spread of infectious diseases overall the world, in particular, the trans-boundary animal diseases. Therefore, the aim of this study is to report the prevalence rate of some transboundary infectious diseases to assess the effectiveness of quarantine measure in the detection of exotic disease and clarify the role of live animal trade in infectious transboundary diseases spread.

MATERIALS AND METHODS

The study was done on 176 serum samples obtained from cattle imported from Sudan in order to determine the prevalence of foot and mouth disease (FMD), Peste Des Petits Ruminants (PPR), and Infectious Bovine Rhinotracheitis (IBR). Three serological tests were used; Serum neutralization test for FMD, Indirect enzyme-linked immunosorbent assay (i-ELISA) for PPR, and Competitive ELISA for IBR.

RESULTS

The seroprevalence of FMD in tested sera was; 77.27% in the serotype A (A-Iran), 68.18% in the serotype A (A-Africa), 93.82% in the serotype O (O-Pan Asia), and 35.227% in the serotype South African Territories-2 (SAT-2) SAT-2. While the overall seroprevalence of PPR was 49.431% and the IBR was 93.75%.

CONCLUSION

The result indicates the serious role of live animal trade as "hubs" for infectious diseases spread. Subsequently, the common control measures must be taken to avoid the spread of the diseases through the animal trade; which include screening, surveillance, precautions at borders, and vaccination.

Exploiting serological data to understand the epidemiology of bluetongue virus serotypes circulating in Libya

The epidemiological patterns of Bluetongue (BT) in North Africa and Mediterranean Basin (MB) dramatically changed by emergence of subsequent episodes of novel bluetongue virus (BTV) serotypes with highly pathogenic indexes and socio-economic impacts. The objective of the study was to investigate the sero-prevalence and serotype distribution of BTV in Libya. During 2015-2016, a total of 826 serum samples were collected from domestic ruminants in Libya. All sera were assayed by competitive enzyme-linked immunosorbent assays (c-ELISA). C-Elisa-positive samples (43.3%; 173/400) were further analyzed by virus neutralization assay to identify BTV serotypes and determine the antibody titre of positive samples. An overall BTV sero-prevalence was 48.4% (95% CI: 45.0%-51.8%). Neutralizing antibodies were detected against the following BTV serotypes namely: BTV-1, BTV-2, BTV-3, BTV-4, BTV-9 and BTV-26. While BTV-1, BTV-2, BTV-4 and BTV-9 circulation was unsurprising as they have been responsible of the last year outbreaks in Northern African Countries, the detection of BTV-3 and BTV-26 was definitely new and concerning for the animal health of the countries facing the Mediterranean Basin. It is crucial that European and Northern African authorities collaborate in organizing common surveillance programmes to early detect novel strains or emerging serotypes in order to set up proper preventive measures, and, in case, develop specific vaccines and plan coordinated vaccination campaigns.

A traditional evolutionary history of foot-and-mouth disease viruses in Southeast Asia challenged by analyses of non-structural protein coding sequences

Recombination of rapidly evolving RNA-viruses provides an important mechanism for diversification, spread, and emergence of new variants with enhanced fitness. Foot-and-mouth disease virus (FMDV) causes an important transboundary disease of livestock that is endemic to most countries in Asia and Africa. Maintenance and spread of FMDV are driven by periods of dominance of specific viral lineages. Current understanding of the molecular epidemiology of FMDV lineages is generally based on the phylogenetic relationship of the capsid-encoding genes, with less attention to the process of recombination and evolution of non-structural proteins. In this study, the putative recombination breakpoints of FMDVs endemic to Southeast Asia were determined using full-open reading frame sequences. Subsequently, the lineages’ divergence times of recombination-free genome regions were estimated. These analyses revealed a close relationship between two of the earliest endemic viral lineages that appear unrelated when only considering the phylogeny of their capsid proteins. Contrastingly, one lineage, named O/CATHAY, known for having a particular host predilection (pigs) has evolved independently. Additionally, intra-lineage recombination occurred at different breakpoints compared to the inter-lineage process. These results provide new insights about FMDV recombination patterns and the evolutionary interdependence of FMDV serotypes and lineages.

Genetic diversity and comparison of diagnostic tests for characterization of foot-and-mouth disease virus strains from Pakistan 2008-2012

We report the laboratory analysis of 125 clinical samples from suspected cases of foot-and-mouth disease (FMD) in cattle and Asian buffalo collected in Pakistan between 2008 and 2012. Of these samples, 89 were found to contain viral RNA by rRT-PCR, of which 88 were also found to contain infectious FMD virus (FMDV) by virus isolation (VI), with strong correlation between these tests (κ = 0.96). Samples that were VI-positive were serotyped by antigen detection ELISA (Ag-ELISA) and VP1 sequence acquisition and analysis. Sequence data identified FMDV serotypes A (n = 13), O (n = 36) and Asia-1 (n = 41), including three samples from which both serotypes Asia-1 and O were detected. Serotype A viruses were classified within three different Iran-05 sublineages: HER-10, FAR-11 and ESF-10. All serotype Asia-1 were within Group VII (Sindh-08 lineage), in a genetic clade that differs from viruses isolated prior to 2010. All serotypes O were classified as PanAsia-2 within two different sublineages: ANT-10 and BAL-09. Using VP1 sequencing as the gold standard for serotype determination, the overall sensitivity of Ag-ELISA to correctly determine serotype was 74%, and serotype-specific sensitivity was 8% for serotype A, 88% for Asia-1 and 89% for O. Serotype-specific specificity was 100% for serotype A, 93% for Asia-1 and 94% for O. Interestingly, 12 of 13 serotype A viruses were not detected by Ag-ELISA. This study confirms earlier accounts of regional genetic diversity of FMDV in Pakistan and highlights the importance of continued validation of diagnostic tests for rapidly evolving pathogens such as FMDV.