Spatial trend of Foot and Mouth Disease virus (FMDV) serotypes in cattle and buffaloes, Pakistan

Circulation of foot-and-mouth disease serotypes, risk factors, and their effect on hematological and biochemical profiles among cattle and buffalo in Quetta, Balochistan, Pakistan

Background and Aim

Foot-and-mouth disease (FMD) is an infectious disease of cloven-hoofed animals, including buffalo, cattle, sheep, goats, and pigs, causing major economic losses to the local farmers and, overall, to the national economy of the country. This study aimed to detect FMDV serotypes in year-round FMD outbreaks, hematological and biochemical changes, and oxidative stress in FMDV-infected cattle and buffaloes in the district of Quetta, Balochistan, Pakistan, and the socioeconomic impact of FMD outbreaks on farmers.

Materials and Methods

We conducted a cross-sectional study in the district of Quetta, Balochistan, Pakistan, where FMD virus (FMDV) serotypes were detected by enzyme-linked immunosorbent assay (ELISA). Hematological, biochemical, and oxidative analyses were performed by analyzing the blood of FMDV-infected and non-infected animals. Information on the associated risk factors was obtained through a structured questionnaire by interviewing farmers in each FMD-affected farm.

Results

Thirty-four out of 38 farms (89%, 95% confidence interval [CI]: 75%-97%) were positive for FMD by ELISA. Higher FMD infection was detected in farms with a herd size of <50 animals (50%, 17/34), followed by >100 animals (32%, 11/34) and 51-100 animals (18%, 6/34). Fifty-seven percent (114/200, 95% CI: 50%-64%) of animals were positive for FMD. Of these, 61% (69/114) were cattle and 39% (45/114) were buffalo. FMD positivity was higher in females (86%, 98/114) than in males (14%, 16/114) and higher in animals older than 2 years of age (52%, 59/114). On average, farmers lose U.S. dollars 3000 annually due to FMD outbreaks. Animals infected with FMDV had significantly (p ≤ 0.05) white blood cell counts and significantly (p ≤ 0.05) lower hemoglobin and total protein concentrations in buffalo and cattle, whereas infected cattle showed significantly (p ≤ 0.05) lower albumin levels. Globulin levels were lower in buffaloes infected. Alanine aminotransferase levels were lower in infected cattle (p ≤ 0.05). Creatinine levels were higher in infected buffalo (p ≤ 0.05). Urea and phosphorus concentrations were higher in FMDV-infected cattle and buffalo (p ≤ 0.05). Calcium levels were lower in infected cattle and buffalo (p ≤ 0.05). Catalase enzyme activity in infected cattle and buffaloes was significantly lower (p < 0.05). Lipid peroxidation was significantly higher in FMDV-infected cattle and buffalo (p ≤ 0.05).

Conclusion

This study confirmed serotype O circulation among cattle and buffalo in year-long FMD outbreaks in the Quetta District of Balochistan. Blood analysis identified a parameter deviated from the normal level due to FMDV infection. In addition, the outbreak of FMD has a significant negative economic impact on livestock farmers.

The prevalence of foot-and-mouth disease in Asia

Foot-and-mouth disease (FMD) is listed among the highly contagious diseases in animals and is endemic throughout the Asian continent. The disease is caused by the Foot-and-mouth disease virus (FMDV) and affects a wide variety of domesticated animals as well as wild ungulates. Clinically, the disease is described as a vesicular lesion on the tongue, muzzle, lips, gum, dental pad, interdigital cleft, coronary band, and heel of the foot. Sometimes these lesions give rise to lameness. Mastitis is also caused due to teat lesions. A biochemical test reveals that during FMD infection, there are elevated levels of interleukin-1 (IL-1), tumor necrosis factor-alpha, interferon-gamma (IFN-γ), interleukin-6, serum amyloid A protein, lactoferrin, mannose-binding lectin, and monocytes chemo-attractant protein-1 in the serum of infected animals. There is no specific treatment for FMD although some antivirals are given as prophylaxis and antibiotics are given to prevent secondary bacterial infection. This review presents comprehensive data on the prevalence of FMD and serotypes of FMDV that are attributable to the cause of FMD from a regional point of view. It also explains the worldwide dynamics of the seven serotypes of FMD and tries to identify epidemiological clusters of FMD in various geographical areas. Furthermore, the pathology associated with the foot and mouth disease virus along with the pathophysiology is discussed. The continent-wide prevalence and diversity patterns of FMD suggest that there is a need for stringent policies and legislation implementation regarding research and development aimed at manufacturing strain-specific vaccination, infection prevention, and control of the disease.

Genetic stability of foot-and-mouth disease virus during long-term infections in natural hosts

Foot-and-mouth disease (FMD) is a severe infection caused by a picornavirus that affects livestock and wildlife. Persistence in ruminants is a well-documented feature of Foot-and-mouth disease virus (FMDV) pathogenesis and a major concern for disease control. Persistently infected animals harbor virus for extended periods, providing a unique opportunity to study within-host virus evolution. This study investigated the genetic dynamics of FMDV during persistent infections of naturally infected Asian buffalo. Using next-generation sequencing (NGS) we obtained 21 near complete FMDV genome sequences from 12 sub-clinically infected buffalo over a period of one year. Four animals yielded only one virus isolate and one yielded two isolates of different serotype suggesting a serial infection. Seven persistently infected animals yielded more than one virus of the same serotype showing a long-term intra-host viral genetic divergence at the consensus level of less than 2.5%. Quasi-species analysis showed few nucleotide variants and non-synonymous substitutions of progeny virus despite intra-host persistence of up to 152 days. Phylogenetic analyses of serotype Asia-1 VP1 sequences clustered all viruses from persistent animals with Group VII viruses circulating in Pakistan in 2011, but distinct from those circulating on 2008–2009. Furthermore, signature amino acid (aa) substitutions were found in the antigenically relevant VP1 of persistent viruses compared with viruses from 2008–2009. Intra-host purifying selective pressure was observed, with few codons in structural proteins undergoing positive selection. However, FMD persistent viruses did not show a clear pattern of antigenic selection. Our findings provide insight into the evolutionary dynamics of FMDV populations within naturally occurring subclinical and persistent infections that may have implications to vaccination strategies in the region.

Interplay of foot and mouth disease virus with cell-mediated and humoral immunity of host

Foot and mouth disease virus (FMDV) causes a communicable disease of cloven hoofed animals, resulting in major economic losses during disease outbreaks. Like other members of the Picornaviridae FMDV has a relatively short infectious cycle; initiation of infection and dissemination, with production of infectious virions occurs in less than a week. The components of innate immunity as well as cell-mediated and humoral immunity play a crucial role in control of FMDV. However, it has been shown in vitro using a mouse model that FMDV has evolved certain mechanisms to counteract host immune responses ensuring its survival and spread. The viral leader proteinase, L pro, deters interferon beta (IFN-β) mRNA synthesis, thus, inhibiting host cell translation. Another viral proteinase, 3C pro, disrupts host cell transcription by cleaving histone H3. A transient lymphopenia in swine as a consequence of FMDV infection has also been observed, but the mechanism involved and viral protein(s) associated with this process are not clearly understood. In this review, we have covered the interaction of FMDV with different immune cells including lymphocytes and antigen presenting cells and their consequences.

An appraisal on the occurrence of foot-and-mouth disease virus serotypes in cattle and buffaloes, Pakistan

Foot-and-mouth disease (FMD) is a livestock disease that has serious economic repercussions. Here, we report the laboratory results for samples from suspected outbreaks that were sent for confirmation of FMD in Pakistan. From January 2010 to December 2011, 132 suspected outbreaks were investigated, and samples from 58 out of the 76 outbreaks sent to the National Veterinary Laboratory (NVL) were positive. The highest proportion of positives were of serotype O (65.52 %), followed by serotype A (24.14 %) and serotype Asia-1 (10.35 %), whereas amongst the samples sent to the World Reference Laboratory, Pirbright, UK (WRL), samples from 48 out of 56 outbreaks were confirmed to be FMD positive, with the following serotypes identified: O (56.25 %), Asia-1 (37.50 %) and A (6.25 %). The outbreaks affected cattle, buffalo and mixed (cattle and buffalo) herds at rates of 91, 70 and 76 %, respectively. The trend of positive outbreaks was higher in the months of winter and late spring (November to April). Although the serotype O isolates and some of the serotype A isolates from the field samples resembled the vaccine strains (r-value ≥ 0.3), this was not the case for the Asia-1 isolates. These results help to improve our understanding of the occurrence and distribution of FMD in cattle and buffaloes in Pakistan and to provide baseline information for the FMD progressive control program in the country.

Foot-and-mouth disease: overview of motives of disease spread and efficacy of available vaccines

Control and prevention of foot and mouth disease (FMD) by vaccination remains unsatisfactory in endemic countries. Indeed, consistent and new FMD epidemics in previously disease-free countries have precipitated the need for a worldwide control strategy. Outbreaks in vaccinated animals require that a new and safe vaccine be developed against foot and mouth virus (FMDV). FMDV can be eradicated worldwide based on previous scientific information about its spread using existing and modern control strategies.