Lumpy skin disease virus isolation, experimental infection, and evaluation of disease development in a calf

Abstract

Lumpy skin disease (LSD) is one of the most economically significant viral diseases of cattle caused by the Lumpy Skin Disease Virus (LSDV), classified as a member of the genus Capripoxvirus and belongs to the family Poxviridae. Nodular skin samples were collected from clinically sick cattle in the districts of Amuru and Wara Jarso Ethiopia to isolate LSD virus. The virus was isolated using primary lamb testis and kidney cells. The isolated LSDV was infected into a healthy calf while maintaining the necessary biosecurity measures to generate skin lesions and to assess disease progression using postmortem examinations. On the fourth day after virus inoculation, the calf developed typical LSD skin nodules with increased rectal temperature, which lasted until the 12th day, when they began to decrease. Viral shedding was detected in nasal, oral, and conjunctival swabs from 6 to 14 days after infection using real-time PCR. Post-mortem tissue specimens tested positive for LSD virus using real-time PCR and virus isolation. This study showed that LSDV were responsible for the LSD outbreaks, and the appearance of typical skin nodules accompanied by fever (> 39.5 °C) defined the virus's virulent status. The experimental infection with the isolated infectious LSDV could serve as a platform for future vaccine evaluation study using an LSDV challenge model.

Keywords: Calf; Disease development; Experimental infection; Lumpy skin disease; Virus isolation.

Figure 1

Cattle showing typical clinical signs of lumpy skin disease with generalized nodular skin lesions covering the entire body and perineum area.

Figure 2

Monolayer of normal lamb testis cells (A); Lamb testis monolayer cells infected with LSDV where cytopathic effects developed at day 6 (B) and day 10 (C) (the arrows indicate infected cells aggregation and destruction).

Figure 3

Conventional PCR results on LSD outbreak samples.

Figure 4

Real time PCR results. (A) Melting curve profiles of the tested samples and CaPV controls after PCR amplification of the RPO30 gene, (B) Representative normalized melt curve profiles, (C) Melting curve analysis of LSDV field isolates and controls.

Figure 5

The experiment’s healthy calf (A); and the calf after clinical disease development with typical skin nodules distributed all over the body surface (B).

Figure 6

The daily rectal temperature of an experimentally infected calf with the LSD virus.

Figure 7

Gross lesions in cattle following experimental LSD virus infection. (A) Development of typical nodule on the rumen. (B) Swelling of the superficial lymph node.

Figure 8

Map of Ethiopia with sample collection sites identified in yellow in the Amuru district of Horo Guduru Wellega zone and Wara Jarso district of North Shewa zone (generated using QGIS version 3.10).