First detection of two novel malignant catarrhal fever-related gammaherpesviruses associated with sudden deaths of dorcas gazelles (Gazella Dorcas osiris)

Abstract

Malignant catarrhal fever (MCF) is a sporadic infectious disease of domesticated and non-domesticated ruminants including: cattle, sheep, bison, cervids, antelope and buffaloes, and is caused by gammaherpesviruses. Between March and May 2023, several cases of sudden death were observed in endangered species of dorcas gazelle (Gazella dorcas osiris) in zoological garden in southeastern Poland. Given the rapid course of disease, MCF was suspected. During the epizootic investigation, other ruminants that could be a source of infection and routes of spread were examined, also taking into account the possibility of air-born and via rodents transmission. In total, tissue, blood, nasal swab and fecal samples were collected from 52 animals kept in the zoo between March 2023 and August 2025. Samples came from 10 ruminants species: dorcas gazelle (Gazella dorcas), blackbuck (Antilope cervicapra), lechwe (Kobus leche), Defassa waterbuck (Kobus ellipsiprymnus defassa), Reeves’s muntjac (Muntiacus reevesi), Kirk’s dik-dik (Madoqua kirkii), gemsbok (Oryx gazella), Barbary sheep (Ammotragus lervia), mhorr gazelle (Nanger dama) and domestic goat (Capra hircus). Additionally, environmental swabs and tissue samples from rats (Rattus norvegicus) trapped at the premises were collected. To identify possible causes of dorcas mortality, samples were tested using PCRs specific to gammaherpesviruses followed by characterisation of strains based on DNA polymerase fragment sequences. Clostridium spp. was also investigated in the differential diagnosis. Results: In total 4 different strains of gammaherpesvirus were detected in 26.9% (14/52) of the tested ruminants, It was also established that the five gazelles with suspected MCF were infected with at least one of the two previously unknown gammaherpesviruses provisionally called: Gazelle dorcas gammaherpesvirus 1 and Gazelle dorcas gammaherpesvirus 2. Those viruses showed significant similarity to Rusa unicolor equina gammaherpesvirus later detected in asymptomatic dik-diks and Bovidae gammaherpesvirus 2 in healthy blackbucks, respectively. These viruses were not detected in newborn, nor in the two remaining dorcas survivors. Histopathological analysis showed changes that might be associated with MCF in kidneys, lungs and livers of two affected dorcas gazelles. C. perfringens type D co-infection was detected also in two adult dorcas which died suddenly. The same bacteria was also found in the feeder in one of the enclosures, suggestive of environmental contamination. Conclusion: This is the first description of two novel gammaherpesvirus, associated with fatal disease in dorcas gazelles. Additionally, our results showed possibility of transmission of those viruses between different Antilopinae species. While ranges of those species do not overlap in their natural habitat, our results could have potential implication for conservation strategies and initiatives for endangered species.