Sheep-associated malignant catarrhal fever in Middle Egypt: a one-year study

Malignant catarrhal fever (MCF) is a sporadic viral infection that affects ruminants, including cattle and water buffalo. Its global spread reflects the coexistence of primary carriers, including sheep and wildebeest in domestic settings, with other susceptible hosts. The main objective of the current study was to report a sporadic occurrence of sheep-associated malignant catarrhal fever (SA-MCF) in Middle Egypt across different seasons using molecular and epidemiological approaches. Among 106 sheep, 43 goats, 11 cattle and 4 buffaloes kept together in different premises, a total of nine cases (seven cattle and two buffaloes) showed signs suggestive of MCF. Samples were collected from peripheral blood mononuclear cells and cheek papillae for DNA extraction. A semi-nested PCR targeting a 422 bp region was performed, followed by direct gene sequencing. Naturally infected animals showed depression and high fever (> 41 °C), progressing to nasal and ocular discharges, conjunctival hyperemia, corneal edema, buccal erosion, muzzle encrustation, enlarged lymph nodes and neurological signs. PCR and sequencing confirmed the presence of ovine herpesvirus 2 (OvHV-2), with closely related sequences found previously in Egypt, and no significant genomic differences observed globally. Results proved the circulation of OvHV-2 in the area under investigation and highlighted the challenge of managing multi-species grazing systems under such conditions, as OvHV-2 infections are not limited to specific seasons.