Capsular type diversity of Mannheimia haemolytica determined by multiplex real-time PCR and indirect hemagglutination in clinical isolates from cattle, sheep, and goats in Spain

This study compares the utility of a commercially available multiplex q-PCR assay for serotyping A1, A2, and A6 M. haemolytica serotypes with indirect hemagglutination, for determining the relative distribution of M. haemolytica capsular types associated with respiratory disorders in cattle, sheep, and goats. For the 129 isolates analyzed, both q-PCR and IHA assays exhibited nearly complete agreement for capsular types A1 (k = 0.965) and A2 (k = 0.888) and substantial agreement for A6 (k = 0.801). Despite the overall good performance of the commercial q-PCR, its effectiveness differed between the host origin of the isolates. The serotype was identified by q-PCR in 83.3 % of cattle, 77.8 % of goat, and 53.8 % of sheep isolates. Combining the results of both methods, A1 was the most prevalent in cattle and sheep (55.6 % and 22.25 %, respectively) but was not detected in goats, A2 was the most prevalent in goats (61.1 %) and the second most prevalent in cattle (16.7 %) and sheep (20.5 %). The prevalence of A6 was 7.4 %, 5.1 %, and 16.7 % in cattle, sheep, and goats, respectively. Other capsular types determined exclusively by IHA were A16 in cattle, A9 in goats, and A7, A8, A9, and A13 in sheep. Capsular type diversity was greater in sheep (H = 0.601) than in cattle (H = 0.408) and goat (H = 0.330) isolates. The commercial multiplex q-PCR is a valuable tool, alternative to IHA, for identifying isolates of capsular types A1, A2, and A6, the most frequent serotypes of M. haemolytica associated with respiratory disease in ruminants. However, when testing sheep isolates it should be complemented with immunological assays due to the wider range of serotypes implicated.

Conventional and real time RT-PCR assays for the detection and differentiation of variant rabbit hemorrhagic disease virus (RHDVb) and its recombinants

Since its emergence, variant RHDV (RHDVb/RHDV2) has spread throughout the Iberian Peninsula aided by the apparent lack of cross protection provided by classic (genogroup 1; G1) strain derived vaccines. In addition to RHDVb, full-length genome sequencing of RHDV strains has recently revealed the circulation of recombinant viruses on the Iberian Peninsula. These recombinant viruses contain the RHDVb structural protein encoding sequences and the non-structural coding regions of either pathogenic RHDV-G1 strains or non-pathogenic (np) rabbit caliciviruses. The aim of the work was twofold: firstly to validate a diagnostic real time RT-PCR developed in 2012 for the detection of RHDVb strains and secondly, to design a conventional RT-PCR for the differentiation of RHDVb strains from RHDVb recombinants by subsequent sequencing of the amplicon.