Tracking Efficiency Improvement According to Incident Beam Size in QPD-Based PAT System for Common Path-Based Full-Duplex FSO Terminals.

Free space optical (FSO) communication can support various unmanned aerial vehicles' (UAVs) applications that require large capacity data transmission. In order to perform FSO communication between two terminals, it is essential to employ a pointing, acquisition, and tracking (PAT) system with an efficient and optimal performance. We report on the development of a common optical-path-based FSO communication system, tailored for applications in UAVs. The proposed system is equipped with a quadrant photodiode (QPD)-based PAT system without an additional beacon beam subsystem. The presented approach reduced the structural complexity and improved the tracking efficiency for the same size, weight, and power (SWaP). To achieve a robust FSO link in a dynamic UAV environment, the observability and controllability were obtained based on the linearized control according to the incident beam size on the QPD, which was verified by optical simulation and experiments. As a result, the QPD-based PAT system for implementing FSO links demonstrated an up to 4.25 times faster tracking performance. Moreover, the FSO link experimentally confirmed the 1.25 Gbps full-duplex error-free communication at a 50 m distance.

Molecular surveillance of viral pathogens associated with diarrhea in pre-weaned Korean native calves.

Calf diarrhea causes severe economic losses in the cattle industry worldwide. This study investigated the prevalence of bovine coronavirus (BCoV), bovine norovirus (BNoV), bovine group A rotavirus (BoRVA), and bovine torovirus (BToV) in calves aged ≤ 60 days, regardless of diarrhea, across nine different regions in the Republic of Korea (ROK) and reported associations between these viruses and diarrhea. Fecal samples were collected rectally from 689 calves: normal (n = 360) and diarrheic (n = 329). BNoV (84/689, 12.2%) was the most prevalent regardless of diarrhea, followed by BCoV (37/689, 5.4%), BToV (15/689, 2.2%), and BoRVA (13/689, 1.9%). Although BCoV (P = 0.032) and BoRVA (P = 0.007) were significantly associated with diarrhea in pre-weaned calves, BNoV and BToV showed no association. Infection by the four pathogens had no relationship with calf age; BoRVA was detected only in calves aged < 30 days, but this finding was not statistically significant. Phylogenetic analysis revealed that BCoV isolates obtained in this study were distinct from the other known BCoVs, and all BNoV isolates belonged to GIII.2 genotype; genetic variations in BNoVs are present in the ROK. BoRVA isolates distributed in the ROK were assigned to G6P[5]. Within the P[5] genotype, our isolates were divided into two lineages: P[5]-III and P[5]-VIII. P[5]- VIII lineage was dominant in pre-weaned Korean native calves. Our BToV isolates were more closely related to a European isolate, B145, than to Japanese isolates. Here, BNoV was frequently identified in calves, suggesting its non-significant contribution to calf diarrhea, whereas BCoV and BoRVA were responsible for calf diarrhea in the ROK. Consequently, our results highlight the importance of rapid diagnosis against these viruses in calf diarrhea.

Prevalence and molecular characterization of Cryptosporidium and Giardia in pre-weaned native calves in the Republic of Korea.

Cryptosporidium spp. and Giardia duodenalis are protozoan parasites that cause diarrhea in humans and animals. Molecular data on Cryptosporidium spp. and G. duodenalis in calves in the Republic of Korea (ROK) is limited; thus, we investigated the prevalence of Cryptosporidium and Giardia in pre-weaned calves, analyzed the association between these parasites and diarrhea, and identified their zoonotic potential for human infection. Fecal samples were collected from 315 pre-weaned calves aged 1-60 days from 10 different regions in the ROK and screened for Cryptosporidium spp. and G. duodenalis using PCR. Overall prevalence of Cryptosporidium spp. and G. duodenalis was 4.4% (n = 14) and 12.7% (n = 40), respectively. Co-infection was not detected. All Cryptosporidium-positive samples were identified as C. parvum after sequence analysis of a small subunit rRNA fragment and further subtyped into zoonotic IIaA15G2R1 (n = 13) and IIaA18G3R1 (n = 1) by DNA sequencing of the 60-kDa glycoprotein gene. To our knowledge, this is the first report of C. parvum IIaA15G2R1 subtype in calves in the ROK. Based on ß-giardin (bg) gene, G. duodenalis-positive samples belonged to assemblages E (n = 36) and A (n = 4), with the latter belonging to subtype A1, the zoonotic genotype. Six subtypes of assemblage E were identified at the bg locus: E1 (n = 6), E2 (n = 3), E3 (n = 13), E5 (n = 1), E8 (n = 1), and E11 (n = 1). The occurrence of C. parvum and G. duodenalis was not associated with diarrhea in pre-weaned Korean native calves. The present results suggest that the prevalence of C. parvum is not related to calf age; in contrast, the prevalence of G. duodenalis was significantly higher in 41-50-day-old calves (odds ratio = 9.90, 95% confidence interval 2.37-41.34; P = 0.001) than in 1-10-day-old calves. Therefore, calves are a potential source of zoonotic transmission, which may have significant public health implications.

Genetic analysis of bovine viral diarrhea virus in pre-weaned native Korean calves.

Bovine viral diarrhea virus (BVDV), a prominent viral pathogen worldwide, causes substantial economic losses in the cattle industry. BVDV comprises two recognized species, BVDV-1 and BVDV-2, and at least 21 subtypes (1a-1u) for BVDV-1 and four subtypes (2a-2d) for BVDV-2 based on its 5'-untranslated region. This study aimed at investigating the prevalence and genetic analysis of BVDV in calf feces in the Republic of Korea (ROK). We collected fecal samples from 635 pre-weaned native Korean calves aged 1-60 days, regardless of diarrhea, and subjected them to RT-PCR and phylogenetic analysis. Thirty-five (5.5%) of the 635 samples were positive for BVDV infection. BVDV was detected in 20, 10, and 5 calves aged 1-20 days, 21-40 days, and 41-60 days, respectively. BVDV was the most frequent in 17 normal feces, followed by 16 diarrheic feces, and 2 hemorrhagic feces. Phylogenetic analysis revealed that 25 samples belonged to BVDV-1b; 1 sample, BVDV-1c; and 9 samples, BVDV-2a. Moreover, the BVDV-1b and BVDV-2a isolates showed genetic variations. BVDV-1b was detected in diarrheic, hemorrhagic, and normal fecal samples. Thus, BVDV-1b is the most prevalent in calves and causes enteric disease with differing severity. BVDV-1c was newly identified in diarrheic calves. Further studies are warranted to elucidate the pathogenesis of BVDV-1c infection and its clinical manifestations. Our results indicate that effective vaccines and control programs against BVDV are required in the ROK.

Identification of zoonotic Giardia duodenalis in Korean native calves with normal feces.

Giardia duodenalis is an important zoonotic protozoan parasite that infects humans and other animals. This study was conducted to investigate the prevalence and molecular characterization of G. duodenalis infection in the feces of normal and diarrheic pre-weaned calves aged 1-60 days. Fecal samples were collected from 90 Korean native calves in 7 different regions in the central region of the Republic of Korea (ROK). Of the 90 fecal samples, 9 (10%, 9/90) were positive for G. duodenalis by PCR using the ß-giardin gene. Phylogenetic analysis identified G. duodenalis assemblages A and E in the farms examined and G. duodenalis with both assemblage A and E was detected in one farm. Assemblage A was detected in calves with normal feces, while assemblage E was frequently identified in calves with diarrhea. This is the first report of the identification of assemblage A in pre-weaned calves with normal feces in the ROK. These results suggest that G. duodenalis infection is closely associated with calf age and management systems including overcrowding, age-mixed grouping, and hygiene. Thus, giardiasis in calves is an important disease because of its zoonotic significance and should be screened in young animals. Further studies are necessary to elucidate the transmission routes of zoonotic G. duodenalis assemblages.

Detection of African Swine Fever at an Abattoir in South Korea, 2020.

In October 2020, a suspect case of African swine fever (ASF) was detected at an abattoir located in the north-central border region of South Korea. The farm of origin was traced and confirmed positive for ASF. This recurrence was following a period of absence of outbreaks in domestic pigs after the first incursion in 2019, during which a total of 14 domestic pig farms were confirmed between September and October 2019. In 2020, a total of two farms were confirmed, and the molecular characterization of key regions of the genome showed that the two isolates from 2020 were identical with the previous isolates from South Korea in 2019. The continued spread and circulation of ASF in the wild boar population represents an increased risk of spill-over outbreaks in domestic pigs, and, therefore, additional control measures should be implemented for farms in these regions, including a heightened level of surveillance. This was the case for the index farm, which was required to send pigs only to the designated abattoir at which the suspect case was quickly detected. The improvement of biosecurity in pig farms, particularly at the wild boar-domestic pig interface, will be key to the successful control of ASF in the region.

Genetic Characterization of African Swine Fever Virus from Pig Farms in South Korea during Outbreaks in 2019-2021.

In South Korea, a total of 21 African swine fever (ASF) infected farms were confirmed during 2019-2021. ASF viruses (ASFVs) were isolated from the blood and spleen samples of the 21 affected farms and their genetic characteristics were analyzed. Phylogenetic analysis indicated that the 21 Korean ASFV strains belonged to p72 genotype II and serogroup 8. All isolates were of the intergenic region (IGR) II variant with 10 tandem repeat sequences between I73R and I329L and the central variable region (CVR) 1 variant of the B602L gene. There were no IGR variations between the A179L and A137R and between the MGF 505 9R and10R nor mutations in the O174L, K145R, MGF 505-5R, CP204L, and Bt/Sj regions. The genes of the 21 ASFV strains were identical to those of Georgia 2007/1 and Chinese and Vietnamese strains (Pig/HLJ/2018, China/2018/AnhuiXCGQ, and ASFV_NgheAn_2019); however, X69R of the J268L region of the 18th isolate (Korea/Pig/Goseong/2021) had three nucleotide (CTA) insertions at the 209th position, which led to the addition of one tyrosine (Y) at the C-terminal. This suggests that there are variations among ASFVs circulating in South Korea and the 18th ASFV-infected farm was due to a variant different from those of the other 20 pig farms.

Comparison of the Virulence of Korean African Swine Fever Isolates from Pig Farms during 2019-2021.

African swine fever (ASF) was first reported in South Korea in September 2019, and as of 31 December 2021, a total of 21 cases in domestic pig farms and 1875 ASFV-infected wild boars have been confirmed in the country. With the continued circulation of ASF in wild boars, and subsequent outbreaks in domestic pigs, concerns were raised about the possible changes in virulence occurring among African swine fever viruses (ASFV) circulating in South Korea. In this study, four Korean ASFV strains isolated from domestic pig farms at different time points between 2019 and 2021 were chosen, and used to experimentally infect domestic pigs by intramuscular inoculation to compare their virulence. All challenged pigs died at 4-9 days post-inoculation, with many showing clinical symptoms of fever, depression, loss of appetite, and recumbency. Gross lesions observed at necropsy included enlargement and hemorrhage of the lymph nodes and hydropericardium. The study showed that all four Korean ASFV isolates caused acute forms of illness, which supports the view that virulence among the circulating ASFV isolates in South Korea remained unchanged and highly virulent during this period.

Characterization of virulence genes in Escherichia coli strains isolated from pre-weaned calves in the Republic of Korea.

BACKGROUND: Escherichia coli is an important cause of diarrhea in calves and its diarrheagenic properties are related to presence of certain virulence genes. In this study, the prevalence of virulence genes F5, F17, F41, sta, stx1, stx2, eae, and saa in E. coli isolated from pre-weaned calves presenting with (n= 329) or without diarrhea (n= 360) was explored using multiplex polymerase chain reaction. We also evaluated the association between detection of E. coli and the presence of diarrhea. RESULTS: Escherichia coli was detected in 56.3% (388/689) of the fecal samples and showed the highest prevalence (66.5%) in 21-40-day-old calves and the lowest (46.3%) among those that were 1-20 days old. The prevalence of the enterotoxigenic E. coli (ETEC) and Shiga toxin-producing E. coli (STEC) pathotypes was detected in 73.9% and 15.9%, respectively. The results showed no association between diarrhea and the presence of E. coli in general, ETEC or STEC. The F17 gene was the most frequently detected virulence factor in E. coli of calves of all ages regardless of diarrhea. Interestingly, the results show that the calves aged 41-60 days with F17-positive E. coli are at a higher risk for production of Shiga toxin (Stx1; 95% confidence intervals: 1.86-31.95; P = 0.005) compared to calves aged 1-20 days; no association between this finding and diarrhea was observed among the calves of this age group. Moreover, the virulence genes associated with the ETEC and STEC strains were not significantly associated with pathogenicity in this study cohort. CONCLUSIONS: These results suggest that while the incidence of E. coli is age-related, there was no relationship linking E. coli virulence genes to calf age and diarrhea. Furthermore, the present study demonstrated that detection of E. coli strains either with or without virulence factors was not associated with diarrhea in pre-weaned calves.

Zoonotic potential of Enterocytozoon bieneusi in pre-weaned Korean native calves.

BACKGROUND: Enterocytozoon bieneusi is the most common microsporidian species infecting humans and various animals worldwide. To date, there has been limited information on the prevalence of infection and genotypes of E. bieneusi in cattle in the Republic of Korea. Therefore, this study investigated the prevalence and genotypes of E. bieneusi circulating in pre-weaned Korean native calves and determined the age pattern of E. bieneusi infection and the relationship between E. bieneusi infection and diarrhea. METHODS: The prevalence of E. bieneusi infection in pre-weaned Korean native calves was screened by polymerase chain reaction. PCR-positive products were sequenced to determine the genotype of E. bieneusi. A Chi-square analysis was used to compare the association between diarrhea and the infection rate of E. bieneusi in each age range or for all ages. RESULTS: PCR and sequencing analysis revealed an overall prevalence (16.9%, 53/314) of E. bieneusi in pre-weaned calves. The prevalence of E. bieneusi was highest in September (36.2%), followed by March (28.3%). Enterocytozoon bieneusi infection was associated with diarrhea in calves (χ2 = 5.82, P = 0.016). Our results also indicated that E. bieneusi infection was significantly associated with calf age (χ2 = 11.61, P = 0.003), and the prevalence of E. bieneusi infection was significantly higher in calves aged 21-40 days-old (odds ratio: 2.90, 95% confidence interval: 1.54-5.45; P = 0.001) than in those aged 1-20 days-old. Interestingly, the association between E. bieneusi infection and diarrhea was observed only in calves aged 1-20 days-old (χ2 = 5.82, P = 0.010). We identified three known genotypes, BEB4 (n = 12), BEB8 (n = 21) and J (n = 16), and three novel genotypes, BEB8-like (n = 21), KCALF1 (n = 1) and KCALF2 (n = 1). The genotype BEB8 was the most prevalent among all age groups. All genotypes identified in this study exhibited zoonotic potential. CONCLUSIONS: To our knowledge, this is the first report of the genotype BEB4 in pre-weaned Korean native calves. Zoonotic E. bieneusi infection was prevalent in pre-weaned calves, indicating that cattle may play an important role as a reservoir host for E. bieneusi transmission to humans.

Isolation and Genetic Characterization of African Swine Fever Virus from Domestic Pig Farms in South Korea, 2019.

On 17 September 2019, the first outbreak of African swine fever in a pig farm was confirmed in South Korea. By 9 October, 14 outbreaks of ASF in domestic pigs had been diagnosed in 4 cities/counties. We isolated viruses from all infected farms and performed genetic characterization. The phylogenetic analysis showed that all of fourteen ASFV isolates in South Korea belong to genotype II and serogroup 8. Additionally, all isolates had an intergenic region (IGR) II variant with additional tandem repeat sequences (TRSs) between the I73R and I329L genes and showed characteristics of central variable region (CVR) 1 of the B602L gene and IGR 1 of MGF 505 9R/10R genes. These are identical to the genetic characteristics of some European isolates and Chinese isolates.

Identification of Zoonotic Tick-Borne Pathogens from Korean Water Deer (Hydropotes inermis argyropus).

Korean water deer (Hydropotes inermis argyropus) are widespread in the Republic of Korea (ROK). Mostly, Korean water deer are essential hosts for maintaining ticks and tick-borne diseases (TBDs). Here, we investigated the prevalence of tick-borne pathogens (TBPs) among rescued Korean water deer. Anaplasma phagocytophilum (21.4%, 6/28), Anaplasma capra (14.3%, 4/28), Babesia capreoli (3.6%, 1/28), and Coxiella burnetii (3.6%, 1/28) were detected, but Borrelia burgdorferi, Ehrlichia, Rickettsia, and Theileria infections were not found. A. phagocytophilum was the most commonly detected pathogen, and co-infection with A. capra and B. capreoli was also noted in one Korean water deer. To our knowledge, this is the first article of B. capreoli infection in Korean water deer in the ROK. The infecting isolate of A. phagocytophilum was genetically characterized by 16S ribosomal RNA (rRNA) gene and ankyrin-related protein (ankA) gene. Although the 16S rRNA gene alone may not be informative enough to delineate distinct host species, ankA-based phylogeny revealed a high identity of Korean water deer sequences with those of the causative agent of human granulocytic anaplasmosis. A. capra was detected by using citrate synthase gene (gltA), heat-shock protein (groEL), and major surface protein 4 (msp4) genes. Phylogenetic tree based on these gene markers revealed that there were at least two distinct variants within A. capra circulating in the ROK. One variant originated from different hosts including humans, ticks, goats, and sheep, whereas the other variant was reported recently in Korean water deer in the ROK. Consequently, these sequences were identified to belong to a zoonotic species. Sequencing analysis of the 18S rRNA gene revealed that our isolate belonged to B. capreoli and was distinct from Babesia divergens and Babesia venatorum. Moreover, our isolate showed 92.2% homology with B. capreoli sequences, indicating that these differences may be attributed to the different tick species that transmit B. capreoli or to different host species. Genotyping and phylogenetic analysis of C. burnetii based on 16S rRNA and IS1111 genes revealed that our isolate was grouped with several strains of C. burnetii and was genetically distant from Coxiella-like bacteria isolates. The present results highlight that Korean water deer act as potential reservoir hosts for zoonotic TBPs, and thus play an important role in the transmission of TBDs in humans, animals, and livestock.

First report of Anaplasma phagocytophilum infection in Holstein cattle in the Republic of Korea.

Global warming has increased the incidence and risk of tick-borne diseases in domestic animals and humans in the Republic of Korea (ROK). In this study, we investigated the prevalence of Anaplasma phagocytophilum in Holstein cattle (n = 214) in the ROK using specific PCR assays. A. phagocytophilum infection was detected in only two animals (0.93%, 2/214). Our findings showed that PCR assay using the 16S rRNA gene, but not groEL, was suitable for detection of A. phagocytophilum in cattle. Phylogenetic analysis based on the16S rRNA gene showed that A. phagocytophilum was divided into two clades. Clade 1 included Korean isolates, such as those from dogs, cats, Korean water deer, and ticks, while A. phagocytophilum identified in Holstein cattle formed clade 2. Our results suggest that there is genetic variability among isolates of A. phagocytophilum circulating in the ROK. This is the first study to report A. phagocytophilum infection in Holstein cattle in the ROK. As A. phagocytophilum has zoonotic potential, additional epidemiological studies are needed to investigate the prevalence and genetic characterization of A. phagocytophilum from different regions and hosts.

Molecular detection of Anaplasma bovis in Holstein cattle in the Republic of Korea.

Anaplasmosis is a tick-borne infectious disease that affects both human and animal health. This study was performed to characterize and investigate the prevalence of infection with Anaplasma bovis in Holstein cattle originating from two regions in the Republic of Korea (ROK). Blood samples (n = 151; 80 from Namwon and 71 from Jeju Island) were analyzed by polymerase chain reaction, and the prevalence of A. bovis infection was compared before and after grazing. In Namwon, A. bovis infection was not detected, while in the Jeju Island, A. bovis infection was detected in three of 13 animals after grazing. Phylogenetic analysis revealed that the A. bovis isolates had homology (97.1-99.7%) with a Korean spotted deer (Cervus nippon) isolate and Haemaphysalis longicornis tick isolates identified in the ROK. A. bovis infection has not previously been diagnosed in cattle in the ROK. This study shows that A. bovis infection in the Jeju Island is closely related to grazing.