A sheeppox outbreak in Morocco: isolation and identification of virus responsible for the new clinical form of disease

Khalil Zro,Elmostafa El Fahime,Marouane Melloul,Moulay Mustapha Ennaji,Fathiah Zakham

doi:10.1186/1746-6148-10-31

Abstract

BackgroundSheeppoxvirus (SPPV) is a member of the Capripoxvirus genus of the Poxviridae family, which causes significant economic losses in Morocco. The resurgence of the sheeppox disease during 2010 was characterized by an emergence of a classical nodular form for the first time in Morocco. However, little is known about the virus strain responsible for nodular form. In this study, thirty three sheep, from the eastern region of Morocco, clinically infected were examined and dead animals were autopsied.A rapid diagnostic assay for SPPV using different type of clinical samples would be useful for outbreak management. The aim of this work was to isolate the virus strain responsible for nodular form and we identified and compared by phylogenetic analysis the field strain with Moroccan vaccine strain targeting the thymidine kinase (TK) gene and the chemokine analogue receptor of interleukin (IL8) gene. Further, it was important to investigate and validate a real-time PCR using different clinical and post-mortem samples to manage epidemic sheeppox disease.ResultsThe nodular form of sheeppox disease observed in Morocco was clinically characterized by fever, depression, lacrimation, diarrhea in lambs and nodule. At necropsy, the most affected organ was the lung. The etiological strain was successfully isolated from lung nodule in a dead lamb and was identified by using real-time PCR that has been tested and validated on different types of clinical and post mortem samples from naturally infected animals. Sequence and phylogenetic analysis of TK and IL8 gene showed that there was a very close relationship between field and vaccine strain. They were clustered within other SPPV strains.ConclusionIn the current study, we show for the first time the nodular form of sheeppox in Morocco. We demonstrate a robust real-time PCR-based diagnostic assay to detect the sheeppox virus in multiple sample that can be implemented to efficiently manage the disease outbreak. Our study also offers the prospect for future molecular studies to understand the clinical forms.

Highlights

Sheeppoxvirus (SPPV) is a member of the Capripoxvirus genus of the Poxviridae family, which causes significant economic losses in Morocco
Sheeppox outbreaks The SPPV is an infectious transboundary disease that negatively impacts on animal trade and causes significant economic losses, so it must be notified to the Organization for Animal Health (OIE) [3]
Despite the presence of goats in the same flock as affected sheep, in all outbreaks, the clinical signs were observed only in sheep. This assumes that the SPPV Moroccan wild strain has a strictly a sheep tropism which is contrary to what has been recently reported in China where goatpox virus (GTPV) was isolated from sheep [6]

Summary

Introduction

Sheeppoxvirus (SPPV) is a member of the Capripoxvirus genus of the Poxviridae family, which causes significant economic losses in Morocco. The resurgence of the sheeppox disease during 2010 was characterized by an emergence of a classical nodular form for the first time in Morocco. During the epizootic outbreaks recorded during 2010 in the Eastern region of Morocco, we exclusively noted for the first time the appearance of a new form, called the nodular form and was qualified as severe in some cases. This clinical form has been reported in Mauritania [6] and reproduced following experimental inoculation of animals with SPPV strains isolated in some countries in West Africa [7,8]

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