Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus in the family Bunyaviridae , genus Nairovirus . The virus is transmitted to humans through infected tick bites or from direct contact with viremic animals or humans. In the present study, a total of 1,015 adult ticks were collected from cattle (603 specimens), sheep (17 specimens), and goats (395 specimens) in the Kelkit Valley in Turkey. Four tick species were recognized on the animals in the surveyed region. The most abundant species were Rhipicephalus bursa and Hyalomma marginatum marginatum , at 47.68% (484/1,015) and 46.40% (471/1,015), respectively. Reverse transcriptase PCR was used to recover partial sequences of the CCHFV small (S) genome segment. The presence of CCHFV was determined in 3 of 33 (9.09%) R. bursa pools and in 1 of 31 (3.22%) H. m. marginatum pools. Virus sequences from R. bursa were extremely different from those of the Greek CCHFV strain (U04958) isolated from an R. bursa tick. Phylogenetic analysis indicated that the CCHFV isolates obtained in this study clustered in group 5, whose range encompasses southwestern Russian and Kosovo. This is the first evidence of CCHFV in ticks from Turkey. Even though Hyalomma is the main vector for CCHFV, R. bursa may play a role in CCHFV transmission.

Crimean-Congo hemorrhagic fever (CCHF) is an acute tick-borne zoonotic disease. The disease has been reported in many countries of Africa, Asia, the Middle East, and in Eurasia. During the past decade, new foci of CCHF have emerged in the Balkan Peninsula, southwest Russia, the Middle East, western China, India, Africa, and Turkey. CCHF virus produces severe hemorrhagic manifestations in humans with fatality rates up to 30%. Vaccine development efforts have been significantly hampered by a lack of animal models and therefore, no protective vaccine has been achieved. Lately, IFN α/β receptor deficient (IFNAR^−/−) mice have been established as a novel small animal model of CCHF virus infection. In the present study, we found that IFNAR^−/− mice highly susceptible to CCHF virus Turkey-Kelkit06 strain. Immunization with the cell culture based vaccine elicited a significant level of protection against high dose challenge (1,000 PPFU) with a homologous CCHF virus in IFNAR^−/− mice. The CCHF virus is one of the most geographically widespread tick-borne viruses, and has been reported in many countries of Africa, Asia, the Middle East, and in Eurasia. Since 2002, there have been more than 8000 cases in Turkey, with mortality rate around 5%, making CCHF a public health concern. There are currently no specific antiviral therapies or licensed vaccines for CCHF. Due to limitations in treatment options and difficulties posed by vector control vaccination remains the most logical method of disease control. In the present study, we showed that immunization with the cell culture based vaccine against CCHF elicited a significant level of protection against a high dose challenge (1,000 PPFU) with a homologous CCHF virus Turkey-Kelkit06 strain in IFNAR^−/− mice. The animals vaccinated with 5, 20, 40 μg dose of the cell culture based vaccine were partially protected (60%, 80% and 80% protection, respectively) with a significant delay in time to death. Neutralizing antibody responses are essential for the increased of protection in the mice vaccinated with the cell culture based vaccine but this cannot be the only mechanism of protection.

The COVID-19 pandemic has put global public health at high risk, rapidly spreading around the world. Although several COVID-19 vaccines are available for mass immunization, the world still urgently needs highly effective, reliable, cost-effective, and safe SARS-CoV-2 coronavirus vaccines, as well as antiviral and therapeutic drugs, to control the COVID-19 pandemic given the emerging variant strains of the virus. Recently, we successfully produced receptor-binding domain (RBD) variants in the Nicotiana benthamiana plant as promising vaccine candidates against COVID-19 and demonstrated that mice immunized with these antigens elicited a high titer of RBD-specific antibodies with potent neutralizing activity against SARS-CoV-2. In this study, we engineered the nucleocapsid (N) protein and co-expressed it with RBD of SARS-CoV-2 in Nicotiana benthamiana plant to produce an antigen cocktail. The purification yields were about 22 or 24 mg of pure protein/kg of plant biomass for N or N+RBD antigens, respectively. The purified plant produced N protein was recognized by N protein-specific monoclonal and polyclonal antibodies demonstrating specific reactivity of mAb to plant-produced N protein. In this study, for the first time, we report the co-expression of RBD with N protein to produce a cocktail antigen of SARS-CoV-2, which elicited high-titer antibodies with potent neutralizing activity against SARS-CoV-2. Thus, obtained data support that a plant-produced antigen cocktail, developed in this study, is a promising vaccine candidate against COVID-19.

Zoonotic infections are globally important diseases and lead to huge economic losses in both low- and middle-income and high-income countries. Global warming, environmental and ecological changes, illegal movement of animals and humans, regional civil wars, and poverty are predisposing factors for the emergence of zoonotic infections and their distribution worldwide; they are also a big threat for the future. In addition, environmental pollution and antimicrobial resistance are immense serious threats and dangers to prevent and control zoonotic infections. The natural location of Turkey allows many emerged or re-emerged infections with zoonotic characteristics by animal movements, such as bird immigrations, and by human movements due to civil wars as seen with regional refugees. Numerous zoonotic diseases, including 37 bacterial, 13 fungal, 29 viral, 28 parasitic (3 trematodes, 7 cestodes, 10 nematodes, and 8 protozoan), and totally 107 infections, have been reported from Turkey to date. Additionally, many ectoparasitic zoonoses within 15 different arthropod groups and one leech infestation have been reported from Turkey to date. The "One Health" initiative is particularly relevant for developing strategies to combat zoonotic diseases. In this article, we review the occurrence of zoonotic diseases in man and animals in Turkey in the light of the "One Health" perspective.