Investigation of a Possible Link Between Vaccination and the 2010 Sheep Pox Epizootic in Morocco.

Sheep pox is endemic in most parts of Northern Africa and has the potential to cause severe economic problems. Live attenuated vaccines are used in Morocco, and in many other countries, to control the disease. Sheep pox virus (SPPV) re-appeared in 2010 causing a nodular clinical form previously not observed in Morocco. The severe clinical signs observed during the course of this outbreak and initial reports citing similarity in nucleotide sequence between the Moroccan vaccine strain and field isolates warranted a more in depth analysis of this epizootic. In this study, sequence analysis showed that isolates obtained from four provinces of eastern Morocco were identical, demonstrating that a single SPPV strain was responsible for the 2010 epizootic. In addition, the genome fragments sequenced and phylogenetic analyses undertaken as part of this study showed significant differences between field isolates and the Moroccan vaccine strain. New PCR methods were developed to differentiate between wild-type isolates and vaccine strains of SPPV. Using these methods, no trace of wild-type SPPV was found in the vaccine and no evidence was found to suggest that the vaccine strain was causing clinical disease.

PCR-based assay to detect sheeppox virus in ocular, nasal, and rectal swabs from infected Moroccan sheep.

Sheeppox is now enzootic in Morocco. The development of a reliable method for rapid diagnosis of the disease is a central part of any control strategy. The aim of this study is to determine the diagnostic value of a variety of clinical samples such as ovine nasal, ocular or rectal swabs for the detection of sheeppox virus (SPPV) by qualitative conventional polymerase chain reaction (PCR), using a single pair of primers targeting the inverted terminal repeats of the SPPV InS-1 strain, a virulent field isolate. Swab and blood samples were collected from forty animals naturally infected with SPPV who had clinical signs of sheeppox. All animals tested PCR-positive for SPPV. Positive results were obtained infrequently with blood samples, whereas swab samples from at least two sites (nasal, ocular, rectal) were positive per evaluated animal. These results indicate that swab samples are suitable for quantitative molecular SPPV diagnosis. PCR product sequences obtained from all types of sheep samples proved to be identical to the corresponding regions of sheeppox virus strain Romania 65.

Development and validation of three Capripoxvirus real-time PCRs for parallel testing.

Capripoxviruses have the potential to cause outbreaks with a severe socio-economic impact. The latter, combined with an altered virus dissemination pattern, warrants its status as an important emerging disease. Disease control or eradication programmes can only be applied successfully if the necessary diagnostic tools are available allowing clear and unequivocal identification of the pathogen. Real-time PCR combines high sensitivity/specificity with a reduced analysis time and is thus a proven useful tool for identification of many pathogens, including Capripoxviruses. In order for a real-time PCR to be used in a diagnostic capacity, the different analytical and diagnostic parameters need to be evaluated to assure data quality. The implementation of parallel testing using multiple real-time PCRs with similar characteristics can improve further Capripoxvirus diagnosis. It was therefore the purpose of this study to develop a triplet real-time PCR panel with similar high sensitivity/specificity and provide sufficient validation data regarding the performance characteristics that the panel can be used in parallel, depending on the purpose and local situation.