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.

Serological Detection of Antibodies to Peste des Petits Ruminants Virus in Large Ruminants.

Peste des petits ruminants (PPR) is an economically important disease of small ruminants with a rapidly expanding geographical distribution. Peste des petits ruminants virus may manifest in a variety of ways with disease ranging from acute to subclinical. We investigated the exposure of large ruminants to PPRV in areas where the virus is endemic in the small ruminant population by assessing the serological status of groups of animals. This study focused on the Punjab province of Pakistan as an area where the virus is endemic and where mixed farming practices occur enabling close interactions between small and large ruminant populations. An overall PPR seropositivity was detected in 10.0% of cattle and 14.16% of buffaloes. Following an assessment of serological profiles in large ruminants within different age groups, a maximum seroprevalence was observed in cattle (17.5%) and buffaloes (22.5%) over 2 years of age indicating the potential utility of sampling large ruminant populations for PPR serosurveillance. The large ruminants sampled between one and two years of age had similar levels of seropositivity within populations with 11.2% and 16.2% of animals being seropositive, respectively. Current PPR vaccination strategies do not enable the differentiation between infected and vaccinated small ruminants, and as such, the serological surveillance of sheep and goats is of little value. When considering eradication programmes for PPRV, this factor is of great significance. However, where large and small ruminants are farmed together, serological surveillance of large ruminants may provide a snapshot of virus infection within populations where mild disease is present or where small ruminants are regularly vaccinated.