Impact of inland waters on highly pathogenic avian influenza outbreaks in neighboring poultry farms in South Korea

Background@#Since 2003, the H5 highly pathogenic avian influenza (HPAI) subtype has caused massive economic losses in the poultry industry in South Korea. The role of inland water bodies in avian influenza (AI) outbreaks has not been investigated. Identifying water bodies that facilitate risk pathways leading to the incursion of the HPAI virus (HPAIV) into poultry farms is essential for implementing specific precautionary measures to prevent viral transmission. @*Objectives@#This matched case-control study (1:4) examined whether inland waters were associated with a higher risk of AI outbreaks in the neighboring poultry farms. @*Methods@#Rivers, irrigation canals, lakes, and ponds were considered inland water bodies.The cases and controls were chosen based on the matching criteria. The nearest possible farms located within a radius of 3 km of the case farms were chosen as the control farms.The poultry farms were selected randomly, and two HPAI epidemics (H5N8 [2014–2016] and H5N6 [2016–2017]) were studied. Conditional logistic regression analysis was applied. @*Results@#Statistical analysis revealed that inland waters near poultry farms were significant risk factors for AI outbreaks. The study speculated that freely wandering wild waterfowl and small animals contaminate areas surrounding poultry farms. @*Conclusions@#Pet birds and animals raised alongside poultry birds on farm premises may wander easily to nearby waters, potentially increasing the risk of AI infection in poultry farms. Mechanical transmission of the AI virus occurs when poultry farm workers or visitors come into contact with infected water bodies or their surroundings. To prevent AI outbreaks in the future, poultry farms should adopt strict precautions to avoid contact with nearby water bodies and their surroundings.

Molecular Genetic Characterization of Shiga Toxin-producing E. coli Isolated from Diarrhea Patients and Cattle in Gwangju Area, Korea

Shiga toxin-producing Escherichia coli (STEC) can cause a broad spectrum of human illness ranging from symptom-free to hemolytic uremic syndrom (HUS). Associations between known or putative virulence factors of STEC and diseases in human were investigated. PCR analyses showed that 33 (78.6%) isolates carried an ehxA enterohemolysin gene and 6 (14.3%) isolates possessed an saa autoaggutinating adhesin gene, and 31 (73.8%) isolates carried an eae intimin gene (7 isolates with type beta, 16 with type gamma, and 3 with type epsilon). Twenty-nine (69%) isolates from patients carried eae+, ehxA+, saa- (genotype A) and 68 (86%) isolates from asymptomatic outbreaks and 4 (36%) isolates from bovine possessed eae-, ehxA+, saa+ (genotype C). Neither the bundle-forming pilus gene nor the enteropathogenic E. coli adherence factor plasmid was found. In HEp-2 cell adherence assay, isolates carrying eae gene exhibited a localized adherence phenotype, the other isolates carrying saa showed LC (loose clusters of bacteria) and IS (isolated bacteria). In conclusion, most STEC isolated from cattle feces in Gwangju, Korea showed characteristics different from those isolated from patients. But these results may be useful information for pathogenesis judgement of STEC.

Identification of Shiga Toxin-producing E. coli Isolated from Diarrhea Patients and Cattle in Gwangju Area, Korea

Shiga toxin-producing Escherichia coli (STEC) strains are commensal bacteria in cattle and cause food borne disease in human. We analyzed the isolation rate of STEC in stool specimens of patients with diarrhea and in fecal samples of cattle in Gwangju, Korea. STEC strains were detected from 33 (0.19%) out of 17,148 patients with diarrhea while there has been a progressive increase in the incidence rate from 0.07% in 2004 to 0.33% in 2008. We investigated serotypes, shiga toxin genes, and antimicrobial resistance patterns of the 44 STEC isolates from human and cattle sources. The 33 STEC isolates from human belonged to 14 O serotypes including O157, O26 and O111. The 11 isolates from cattle belonged to 11 O serotypes. PCR detection for stx genes showed that 12 (27.3%) isolates carried stx1 genes, 20 (45.5%) possessed stx2 genes, and 12 (27.3%) carried both stx1 and stx2. Of the 33 STEC isolates from human, 25 strains (76%) were resistant to one or more antibiotics. High level of resistance to tetracycline (73%) was most common, followed by ticarcillin and ampicillin (64%). But none of the 33 isolates from human were resistant to amikacin, cefazolin, cefepime, cefotetan, cefotaxime, ciprofloxacin, or imipenem. The 5 strains (45%) of the 11 isolates from cattle were resistant to at least one or three antibiotics but most of the isolates were sensitive to the 16 antibiotics employed in this survey. In conclusion, toxin types and serotypes of STEC isolated from human and cattle were diverse, and non-O157 STEC was also observed to be a greater proportion of STEC isolates. According to a specific comparison solely based on the toxin types and serotypes, most of the STEC strains isolated from cattle feces in Gwangju, Korea showed characteristics different from those isolated from patients. Therefore, laboratory surveillance is required to detect and carefully monitor the potentially hypervirulent STEC not only in human and cattle but also in other animals.

Epidemiological Study of Viral Diarrhea in Gwangju Area During 2000~2002

There are well known infectious diarrheal disease including viral disease such as HuCVs (Human caliciviruses), rotaviruses, enteric adenoviruses and astroviruses. We performed surveillance of infectious diarrheal disease in this study for providing the information for regional prevalence of infectious diarrheal disease and establish basement of diagnostic scheme for these infectious diarrheal disease. For the study, 3,400 stool specimens collected from 10 hospitals in Gwangju from April 2000 to March 2002 were used in investigation for the detection of infectious diarrheal disease. For group A rotaviruses, enteric adenoviruses and astrovirus, we carried out antigen capturing ELISA and RT-PCR with specific primers reacting RNA dependent RNA polymerase gene of HuCVs is used for the detection of RNA of HuCVs. As a results, we detected viral antigen or genome from 537 out of 3,400 specimens (15.8%). 443 out of 537 (82.5%) were confirmed as rotaviruses antigen positively, and 14 (2.6%) and 3 (0.8%) samples were antigen positive to enteric adenoviruses and astroviruses, respectively. We detected HuCV genome from 73 (13.6%) samples by specific amplification. We found that predominantly causative virus is rotavirus in Gwangju but HuCVs take major portion of viral agents causing diarrhea considering the age and seasonal distribution of specimens. Prevalence of adenoviruses and astroviruses are very low compared with worldwide situation. While the infection of rotavirus is limited to young infant under 2 years old, infection of HuCV has wide age distribution. These results suggest that existence of various strains of HuCVs and low rate of cross-protection among distinct antigenic group make it difficult to form immunity in older age. This epidemiological information relating to various diarrheic viruses is first reported in Gwangju, therefore it could provide present prevalence of viral agents causing gastroenteritis and backgrounds to establishment of protection viral diarrhea and development.