Lumpy skin disease of cattle: an emerging problem in the Sultanate of Oman

Abstract

Lumpy skin disease (LSD) is a highly infectious disease of cattle caused by a virus belonging to the Capripoxvirus genus of the family Poxviridae. The purpose of this study is to place on record the first confirmation of LSD in the Sultanate. The disease was diagnosed and confirmed using polymerase chain reaction, histopathology, transmission electron microscopy and serum neutralization testing. The epizootic occurred in 2009 involving a large number of animals and covering a wide area including Nezwa, Alqabel, Sohar, Saham and Burimi. Morbidity and mortality rates of 29.7 and 26.3 %, and 13.6 and 15.4 % were observed at Nezwa and Sohar, respectively. The clinical signs were much more severe in Holstein-Friesian cattle compared to indigenous breeds and were characterized by multiple skin nodules covering the neck, back, perineum, tail, limbs and genital organs. Affected animals also exhibited lameness, emaciation and cessation of milk production. Oedema of limbs and brisket, and superficial lymph node enlargement were highly prominent. It is not known from where the virus originated, or how it spread to the Sultanate. The disease has become endemic in the country and is liable to extend to other Gulf Cooperation Council Countries and cause a pandemic. It is of major concern to the Omani dairy industry. Due to the widespread presence of screw worm, serious economic losses can follow outbreaks.

Fig. 1

A small artery in the vicinity of a skin nodule. Note the vasculitis indicated by the presence of inflammatory cells inside and around blood vessels (arrows)

Fig. 2

Mononuclear cells displaying intracytoplasmic inclusions (arrows)

Fig. 3

A small artery showing marked thickening of the tunica media (arrow), as well as a narrow lumen (star)

Fig. 4

Transmission electron micrograph of two negatively PTA-stained LSDV particles indicated (arrows) in close association with a collagen fibre (C). The particles show a typical thread-like structure on their surface and typical “brick-shaped” morphology (arrows)

Fig. 5

Agarose gel (1 %) electrophoresis separation of PCR amplification products of Oman LSD samples. Note: DNA was stained using ethidium bromide and viewed and photographed under a UV light source. Lanes 1 and 9, Phage lambda PstI marker DNA; lanes 2–8, PCR products generated using primer pair 1; lanes 10–16, PCR products generated using primer pair 2. Lane 2, Oman 1; lane 3, Oman 2; lane 4, Oman 3; lane 5, Oman 4; lane 6, positive control (LD18 LSDV field isolate); lane 7, positive control (LSDV Onderstepoort vaccine); lane 8, sterile water negative control; lane 10, Oman 1; lane 11, Oman 2; lane 12, Oman 3; lane 13, Oman 4; lane 14, positive control (LD18 LSDV field isolate); lane 15, positive control (LSDV Onderstepoort vaccine); lane 16, negative control (sterile water)