Calf mortality constitutes a substantial loss for agriculture economy-based countries and is also a significant herd problem in developed countries. However, the occurrence and frequency of responsible gastro-intestinal (GI) pathogens in severe newborn diarrhea is still not well known. We aimed to determine the seasonal and age-associated pathogen distribution of severe diarrhea in newborn calves admitted to the intensive care unit (ICU) of Erciyes University animal hospital over a year. Fecal samples were collected during the ICU admissions, and specimens were subjected to a diarrheal pathogen screening panel that included bovine coronavirus (BCoV), Cryptosporidium spp., ETEC K99+, and bovine rotavirus, using RT-PCR and conventional PCR methods. Further isolation experiments were performed with permissive cell cultures and bacterial enrichment methods to identify the clinical importance of infectious pathogen shedding in the ICU. Among the hospitalized calves aged less than 45 days old, the majority of calves originated from small farms (85.9%). The pathogen that most frequently occurred was Cryptosporidium spp. (61.5%) followed by rotavirus (56.4%). The frequency of animal admission to ICU and GI pathogen identification was higher during the winter season (44.9%) when compared to other seasons. Most calves included in the study were 1–6 days old (44.9%). Lastly, co-infection with rotavirus and Cryptosporidium spp. occurred more frequently than other dual or multi-infection events. This study was the first to define severe diarrhea—causing GI pathogens from ICU admitted newborn calves in Turkey.

Crimean–Congo hemorrhagic fever (CCHF) is an emerging zoonotic infectious disease caused by Crimean–Congo hemorrhagic fever virus (CCHFV). The first clinical CCHF infection was described in 1944 in the Crimean Peninsula, exclusively in humans, with case-fatality rates exceeding 30%. The increasing number of cases, high mortality rate, and lack of effective therapy make CCHF a serious threat to public health and a potential bioterrorism agent. The present study evaluated the development, immunogenicity, and immune response durations for cell-culture-derived inactivated vaccine (CCVax) formulations in comparison with those of mouse-brain-derived vaccine (MBVax) formulations. In this study, the Kelkit06 CCHF virus strain was propagated in both suckling mice and Vero E6 cells, and purified with a sucrose gradient. Formalin-inactivated vaccine candidates were formulated at various doses [low dose (LD), 5 μg; medium dose (MD), 10 μg; high dose (HD), 20 μg)] and mixed with an alum adjuvant. BALB/c mice received the same doses of the vaccine formulations three times at 3-week intervals. The humoral endpoint IgG responses were evaluated and compared for the MBVax and CCVax treatments. The duration of the presence of IgG and neutralizing antibody (Ab) titers was evaluated and compared until up to 1 year after immunization. The humoral IgG responses indicated that the CCVax and MBVax candidates enhanced the IgG endpoint titers in a dose-dependent manner, which were induced more strongly in all the CCVax groups than in the MBVax mice. The fold changes in neutralizing Ab levels were also found to be higher in the CCVax groups: between 2- and 7.6-fold after the second week of the last immunization. The neutralization titers peaked 4 months after immunization in all the vaccine-receiving groups, but these were still comparable at the end of the first year. The CCVax formulations induced higher IgG and neutralizing Ab titers at all the measured time points. In this study, we showed that cell-culture-purified and formalin-inactivated vaccine candidates induced strong and robust immunity in vaccinated mice dose-dependently, more so than mouse-brain-derived vaccines.

Zoonotic coronaviruses have caused several endemic and pandemic situations around the world. SARS caused the first epidemic alert at the beginning of this century, followed by MERS. COVID-19 appeared to be highly contagious, with human-to-human transmission by aerosol droplets, and reached nearly all countries around the world. A plethora of studies were performed, with reports being published within a short period of time by scientists and medical physicians. It has been difficult to find the relevant data to create an overview of the situation according to studies from accumulated findings and reports. In the present study we aimed to perform a comprehensive study in the context of the case fatality ratios (CFRs) of three major human Coronavirus outbreaks which occurred during the first twenty years of 21st century. In this study, we performed meta-analyses on SARS, MERS and COVID-19 outbreak events from publicly available records. Study analyses were performed with the help of highly reputable scientific databases such as PubMed, WOS and Scopus to evaluate and present current knowledge on zoonotic coronavirus outbreaks, starting from 2000 to the end of 2020. A total of 250,194 research studies and records were identified with specific keywords and synonyms for the three viruses in order to cover all publications. In the end, 41 records were selected and included after applying several exclusion and inclusion criteria on identified datasets. SARS was found to have a nearly 11% case fatality ratio (CFR), which means the estimated number of deaths as a proportion of confirmed positive cases; Taiwan was the country most affected by the SARS outbreak based on the CFR analysis. MERS had CFRs of 35.8 and 26 in Saudi Arabia during the 2012 and 2015 outbreaks, respectively. COVID-19 resulted in a 2.2 CFR globally, and the USA reported the highest mortality ratio in the world in the end of first year of COVID-19 pandemic. Some members of the Coronaviridae family can cause highly contagious and devastating infections among humans. Within the last two decades, the whole world has witnessed several deadly emerging infectious diseases, which are most commonly zoonotic in nature. We conclude that pre-existing immunity during the early stages of a pandemic might be important, but case control and management strategies should be improved to decrease CFRs. Finally, we have addressed several concerns in relation to outbreak events in this study.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a zoonotic, tick-borne pathogen that is endemic to some parts of Europe, Africa, and Asia. The disease causes fever and hemorrhagic manifestations in humans but not in animals. Domestic and wild animals are asymptomatic hosts of CCHFV and are critical in the transmission cycle. Hyalomma marginatum spp. has been identified as the natural reservoir and vector of the virus in Turkiye. A few studies have been conducted on domesticated animals showing the seroprevalence of CCHFV in them, but seroevidence in wild animals is absent. For contributing this antrum to the understanding of virus transmission in Turkiye, we performed a seroprevalence investigation of CCHFV in both wild and domesticated animals in various geographical areas of Turkiye. In-house IgG iELISA was performed for the screening of sera IgG in a total of 582 animal samples collected from boar (n = 40), cattle (n = 259), goat (n = 132), hare (n = 21), and sheep (n = 130). Results from ELISA performed on domestic animals revealed 10.81%, 15.15%, and 19.23% anti-CCHF virus seropositivity in cattle, goats, and sheep, respectively, in collected serum samples. ELISA tests performed in wild animals showed 23.81% and 2.5% positivity in hare and wild boars, respectively, suggesting the importance of wild animals in CCHF virus epidemiology in Turkiye. This study performed the first serological investigation of CCHFV in wild animals and provided the first seroevidence of CCHFV in wild boars and hare in Turkiye.

Neonatal calf diarrhea is a widespread and multifactorial condition that poses a significant challenge in cattle farming. The major etiological pathogens include Cryptosporidium parvum, Escherichia coli, bovine group A rotavirus (RVA), and bovine coronavirus (BCoV). Accurate identification of these pathogens is essential for the development of targeted prevention and control strategies. This study aimed to obtain comprehensive molecular epidemiological data on neonatal calf diarrhea by determining the prevalence of major pathogens, evaluating the frequency of mixed infections, and analyzing their association with predisposing factors. Between September 2023 and August 2024, 120 fecal samples were collected monthly from diarrheic neonatal calves across 18 different small-scale cattle farms with similar traditional management practices. Samples were initially screened using polymerase chain reaction (PCR), and positive amplicons were confirmed through sequence analysis. A total of 117 (97.5%) calves were found to be infected with at least one pathogen. Cryptosporidium parvum was the most frequently detected agent, identified in 95 samples (79.1%), followed by E. coli in 61 (50.8%), RVA in 36 (30%), and BCoV in 27 (22.5%). The C. parvum subtype IIaA13G2R1 was identified for the first time in the research area, confirming its dominance as a subtype in calves in Türkiye. Age emerged as the most influential predisposing factor, with E. coli infections occurring most frequently during the first week of life, whereas RVA/BCoV and C. parvum infections peaked during the second week. Seasonal variation also shaped pathogen patterns, with C. parvum occurring at relatively similar rates across seasons, whereas E. coli infections were more frequent in autumn and spring, and RVA/BCoV detections peaked in winter. These findings underscore the importance of early-life monitoring and season-aware management strategies to mitigate neonatal calf diarrhea. Cite this article as: Sürsal Şimşek, N., Çakmak, I., Özen, D., Cengiz, S., Akgüç Çöl, N. , Çanakoğlu, N., & Şimşek, E. (2026). Molecular epidemiology and risk factors analysis of major pathogens causing neonatal calf diarrhea in Muğla, Türkiye. Acta Veterinaria Eurasia, 52, 0198, doi:10.5152/actavet.2026.25198.