Pathological and molecular investigations of systemic form of camelpox in naturally infected adult male dromedary camels in India

Molecular investigations of camelpox virus circulating in dromedary camel population in Rajasthan, India

Camelpox is an important viral disease of dromedary camel in Rajasthan, India. In the present study, partial C18L gene sequences (n = 6) of camelpox virus (CMLV) obtained in an outbreak in Bikaner, Rajasthan, India in year 2022 were compared with other similar sequences obtained in the past in similar geographical location. Clinical and epidemiological features of the disease were also compared. Genomic study suggested variations in C18L gene sequences obtained in the present outbreak from those obtained during the past outbreaks. CMLV were genetically different from cowpox viruses, but appeared identical to CMLV causing disease in Israel, Egypt and Kazakhstan. Genomes of CMLV virus circulating in dromedary camel population of Rajasthan, India appeared diverse and changing, hence complete genome sequencing and identification of genomic changes altering infectivity and pathogenicity is warranted for designing control strategies.

Beta interferons from the extant camelids: Unique among eutherian mammals

The COVID-19 pandemic is a wake-up call on the zoonotic viral spillover events and the need to be prepared for future outbreaks. Zoonotic RNA viruses like the Middle East respiratory syndrome coronavirus (MERS-CoV) are potential pathogens that could trigger the next pandemic. Dromedary camels are the only known animal source of MERS-CoV zoonotic infections, but little is known about the molecular antiviral response in this species. IFN-β and other type-I interferons provide the first line of defense against invading pathogens in the host immune response. We identified the IFNB gene of the dromedary camel and all extant members of the family Camelidae. Camelid IFN-β is unique with an even number of cysteines in the mature protein compared to other eutherian mammals with an odd number of cysteines. The viral mimetic poly(I:C) strongly induced IFN-β expression in camel kidney cells. Induction of IFN-β expression upon infection with camelpox virus was late and subdued when compared to poly(I:C) treatment. Prokaryotically expressed recombinant dromedary IFN-β induced expression of IFN-responsive genes in camel kidney cells. Further, recombinant IFN-β conferred antiviral resistance to camel kidney cells against the cytopathic effects of the camelpox virus, an endemic zoonotic pathogen. IFN-β from this unique group of mammals will offer insights into antiviral immune mechanisms and aid in the development of specific antivirals against pathogens that have the potential to be the next zoonotic pandemic.

Outbreak of a Systemic Form of Camelpox in a Dromedary Herd (Camelus dromedarius) in the United Arab Emirates

Camelpox virus (CMLV) is the causative agent of camelpox, which frequently occurs in the Old World camelids-rearing countries except for Australia. It has also been described in experimentally inoculated New World camelids. Camelpox outbreaks are often experienced shortly after the rainy season, which occurs twice a year on the Arabian Peninsula because of the increased density of the insect population, particularly mosquitos. A systemic form of camelpox outbreak in seven dromedary camels was diagnosed by histology, virus isolation, and PCR. A phylogenetic analysis using full length CMLV genomes of the isolated CMLV strains showed a single phylogenetic unit without any distinctive differences between them. The United Arab Emirates (UAE) isolate sequences showed phylogenetical relatedness with CMLV isolates from Israel with only minor sequence differences. Although the sequences of viruses from both countries were closely related, the disease manifestation was vastly different. Our study shows that the virulence is not only determined by genetic features of CMLV alone but may also depend on other factors such as unknown aspects of the host (e.g., age, overall fitness), management, and the environment.