Hye-Young Jeoung

Avian necrotic enteritis: Experimental models, host immunity, pathogenesis, risk factors, and vaccine development

The increasing trends of legislative restrictions and voluntary removal of antibiotic growth promoters worldwide has already affected, and will continue to affect, poultry production and animal health. Necrotic enteritis (NE) is being considered among the most important infectious diseases in the current poultry production system globally, with an estimated annual economic loss of more than

A novel reassortant canine H3N1 influenza virus between pandemic H1N1 and canine H3N2 influenza viruses in Korea

2 billion, largely attributable to medical treatments and impaired growth performance. Thus, there is an urgent need to develop rational, alternative, and integrated management strategies not only to control NE, but also to prevent it. In both humans and many warm-blooded animals and birds, NE is caused by Clostridium perfringens, a gram-positive, anaerobic, spore-forming bacterium. To accomplish these goals, better understanding of host- and environmentally related factors on the development of NE and potential vaccination strategies against C. perfringens infection will be necessary. Furthermore, a reliable and reproducible NE disease model is needed for characterization of C. perfringens pathogenesis and host protective immunity. This review summarizes recent developments in NE disease models, pathogenesis, host immunity, risk factors, and vaccine development for C. perfringens-associated NE in poultry.

Kobuvirus in South Korean black goats

During recent canine influenza surveillance in South Korea, a novel H3N1 canine influenza virus (CIV) that is a putative reassortant between pandemic H1N1 2009 and H3N2 CIVs was isolated. Genetic analysis of eight genes of the influenza virus revealed that the novel H3N1 isolate presented high similarities (99.1-99.9 %) to pandemic influenza H1N1, except for in the haemagglutinin (HA) gene. The HA gene nucleotide sequence of the novel CIV H3N1 was similar (99.6 %) to that of CIV H3N2 isolated in Korea and China. Dogs infected with the novel H3N1 CIV did not show any notable symptoms, in contrast to dogs infected with H3N2 CIV. Despite no visible clinical signs of disease, nasal shedding of virus was detected and the infected dogs presented mild histopathological changes.

A novel canine influenza H3N2 virus isolated from cats in an animal shelter.

Kobuviruses have been detected in humans and several animal species, including cattle, swine, sheep, canines, mice, and probably bats. While investigating the possibility of Kobuviruses infecting additional animal host species, we detected kobuvirus in three fecal samples from domestic Korean black goats. In a maximum parsimony tree and a Bayesian tree, the 08KG680 strain fell within the bovine kobuvirus lineage, but the 09KG172 and 10KG056 strains did not fall within any of the known animal kobuvirus lineages. Comparative analysis of the partial nucleotide sequences of the RNA-dependent RNA polymerase (RdRp) gene of the 08KG680 strain also revealed high amino acid sequence identity and a close genetic relationship with bovine kobuvirus, but the amino acid sequences of the other two strains had low similarity to those of known kobuvirus isolates from any animal species. The similarity of the sequence of the 08KG680 strains with the bovine kobuvirus indicate that the infectious may have originated from cattle, but the possible source for remaining strains could not be classified.

Identification and cloning of two immunogenic Clostridium perfringens proteins, elongation factor Tu (EF-Tu) and pyruvate:ferredoxin oxidoreductase (PFO) of C. perfringens

The interspecies transmission of avian-origin H3N2 canine influenza virus (CIV) to dogs was first reported in 2007. The present study characterized a novel CIV H3N2 isolated from cats in an animal shelter. A comparative analysis of the deduced amino acid sequences of the A/Canine/Korea/CY009/2010(H3N2) (CY009) and A/Feline/Korea/FY028/2010 (H3N2) (FY028) strains isolated from dogs and cats, respectively, in the animal shelter identified point mutations in 18 amino acid positions within eight viral genes. Interestingly, CY009 and FY028 replicated well in specific pathogen-free embryonated chicken eggs and in mice, respectively. Mice infected with the FY028 strain exhibited significant over expression of IL-10, TNF-α, and IFN-γ (p<0.001) at 3 days postinfection. Thus, an emergency monitoring system should be developed to identify influenza mutations that occur during interspecies transmission in companion animals and for continuous public health surveillance.

Clostridium perfringens α-Toxin and NetB Toxin Antibodies and Their Possible Role in Protection Against Necrotic Enteritis and Gangrenous Dermatitis in Broiler Chickens

Clostridium-related poultry diseases such as necrotic enteritis (NE) and gangrenous dermatitis (GD) cause substantial economic losses on a global scale. Two antigenic Clostridium perfringens proteins, elongation factor Tu (EF-Tu) and pyruvate:ferredoxin oxidoreductase (PFO), were identified by reaction with immune sera from commercial meat-type chickens with clinical outbreak of Clostridium infections. In addition to the genes encoding EF-Tu and PFO, C. perfringens alpha-toxin and necrotic enteritis B-like (NetB) toxin were also expressed in Escherichia coli and their corresponding recombinant proteins were purified. Using the four recombinant proteins as target antigens in ELISA immunoassays, high serum antibody titers were observed not only in chickens with clinical signs of Clostridium infections, but also in apparently healthy animals from the same disease-endemic farm. By contrast, no antibodies against any of the proteins were present in the serum of a specific pathogen-free bird. In ELISA using recombinant proteins of C. perfringens, the levels of anti-bacterial protein antibodies were also higher in chickens which were experimentally induced to show NE clinical signs after co-infection with C. perfringens and Eimeria maxima compared with uninfected controls. These results show that two antigenic C. perfringens proteins, EF-Tu and PFO can be useful detection antigens for C. perfringens-afflicted infections in commercial poultry.

Encephalomyocarditis in Korea: serological survey in pigs and phylogenetic analysis of two historical isolates.

SUMMARY. Necrotic enteritis (NE) and gangrenous dermatitis (GD) are important infectious diseases of poultry. Although NE and GD share a common pathogen, Clostridium perfringens, they differ in other important aspects such as clinical signs, pathologic symptoms, and age of onset. The primary virulence factors of C. perfringens are its four major toxins (&agr;, &bgr;, &egr;, &igr;) and the newly described NE B-like (NetB) toxin. While neutralizing antibodies against some C. perfringens toxins are associated with protection against infection in mammals, the serologic responses of NE- and GD-afflicted birds to these toxins have not been evaluated. Therefore, we measured serum antibody levels to C. perfringens &agr;-toxin and NetB toxin in commercial birds from field outbreaks of NE and GD using recombinant toxin-based enzyme-linked immunosorbent assay (ELISA). Initially, we used this ELISA system to detect antibody titers against C. perfringens &agr;-toxin and NetB toxin that were increased in birds experimentally co-infected with Eimeria maxima and C. perfringens compared with uninfected controls. Next, we applied this ELISA to field serum samples from flock-mated birds with or without clinical signs of NE or GD. The results showed that the levels of antibodies against both toxins were significantly higher in apparently healthy chickens compared to birds with clinical signs of NE or GD, suggesting that these antitoxin antibodies may play a role in protection against NE and GD.

Relative Disease Susceptibility and Clostridial Toxin Antibody Responses in Three Commercial Broiler Lines Coinfected with Clostridium perfringens and Eimeria maxima Using an Experimental Model of Necrotic Enteritis

Serum samples from 3315 pigs from 363 farms located throughout all nine Korean provinces were tested for the presence of encephalomyocarditis virus (EMCV) antibodies using the virus neutralization test. The seroprevalence of EMCV in the total pig population was 9.1%, whereas in the herd the prevalence was 43.5%. The first two EMCVs isolated were K3 and K11; these strains were isolated in 1990 from a mummy and a stillborn fetus, respectively, suspected of having EMCV. Phylogenetic analyses of the capsid coding region and the VP3/VP1 genes using the Bayesian approach, and a neighbor-joining analysis, revealed that the EMCV strains fell into two clusters: groups 1 and 2, with two sub-clusters within group 1, group 1a and 1b. The Korean isolates belonged to the group 1a cluster, along with strains BJC3 (China), B424/90 (Greece) and BEL-2887A/91 (Belgium), whereas five strains isolated from Sus scrofa in Belgium (B279/95, B440/95), Italy (I001/96, I136/86), and Cyprus (C108/95) belonged to the group 2 cluster.

Effects of anticoccidial and antibiotic growth promoter programs on broiler performance and immune status

SUMMARY Necrotic enteritis is an enteric disease of poultry resulting from infection by Clostridium perfringens with coinfection by Eimeria spp. constituting a major risk factor for disease pathogenesis. This study compared three commercial broiler chicken lines using an experimental model of necrotic enteritis. Day-old male Cobb, Ross, and Hubbard broilers were orally infected with viable C. perfringens and E. maxima and fed a high-protein diet to promote the development of experimental disease. Body weight loss, intestinal lesions, and serum antibody levels against &agr;-toxin and necrotic enteritis B-like (NetB) toxin were measured as parameters of disease susceptibility and host immune response. Cobb chickens exhibited increased body weight loss compared with Ross and Hubbard breeds and greater gut lesion severity compared with Ross chickens. NetB antibody levels were greater in Cobb chickens compared with the Ross or Hubbard groups. These results suggest that Cobb chickens may be more susceptible to necrotic enteritis in the field compared with the Ross and Hubbard lines. RESUMEN Nota de Investigación—Susceptibilidad relativa a la enfermedad y respuesta de anticuerpos contra toxinas clostridiales en tres líneas de pollo de engorde comerciales coinfectadas por Clostridium perfringens y Eimeria maxima utilizando un modelo experimental de enteritis necrótica. La enteritis necrótica es una enfermedad entérica de las aves comerciales que resulta de la coinfección por Clostridium perfringens y Eimeria spp. que constituye un factor de riesgo importante para la patogénesis de la enfermedad. En este estudio se compararon tres líneas de pollos de engorde comerciales utilizando un modelo experimental de enteritis necrótica. Pollos de engorde de un día de edad, de las líneas Cobb, Ross y Hubbard fueron infectados oralmente con C. perfringens y con E. maxima viables y fueron alimentados con una dieta alta en proteínas para favorecer el desarrollo de la enfermedad experimental. Se midieron la pérdida de peso corporal, las lesiones intestinales, y los niveles séricos de anticuerpos contra la toxina &agr; y contra la toxina de enteritis necrótica similar a la toxina B (NetB) y se analizaron como parámetros de susceptibilidad a la enfermedad, también se midió la respuesta inmune del huésped. Los pollos de la línea Cobb mostraron una mayor pérdida de peso corporal en comparación con los pollos de las líneas Ross y Hubbard y mayor severidad de lesiones intestinales en comparación con los pollos Ross. Los niveles de anticuerpos contra la toxina NetB fueron mayores en pollos Cobb en comparación con los pollos de las líneas Ross y Hubbard. Estos resultados sugieren que los pollos Cobb pueden ser más susceptibles a la enteritis necrótica en el campo en comparación con las líneas Hubbard y Ross.

Prevalence of Korean cats with natural feline coronavirus infections

This study investigated the effects of various coccidiosis control programs in combination with antibiotic growth promoters (AGPs) on growth performance and host immune responses in broiler chickens. The coccidiosis programs that were investigated included in ovo coccidiosis vaccination (CVAC) with Inovocox or in-feed medication with diclazuril as Clinacox (CLIN) or salinomycin (SAL). The AGPs were virginiamycin or bacitracin methylene disalicylate plus roxarsone. As a negative control, chickens were non-vaccinated and fed with non-supplemented diets (NONE). All animals were exposed to used litter from a commercial broiler farm with confirmed contamination by Eimeria parasites to simulate in-field exposure to avian coccidiosis. Broiler body weights in the CVAC group were greater at 14 and 32 days of age, but not at day 42, compared with the NONE, CLIN, and SAL groups. At day 14, the SAL group showed decreased body weight and reduced ConA-stimulated spleen cell proliferation compared with the CLIN and SAL groups. In contrast, at days 34 and 43, splenocyte proliferation was greater in the CVAC and CLIN groups compared with the NONE and SAL groups. Lymphocyte subpopulations and cytokine mRNA expression levels in the intestine and spleen were also altered by the denoted treatments. Collectively, these results suggest that in ovo coccidiosis vaccination or coccidiostat drug medication programs in combination with AGPs influences chicken growth and immune status in an Eimeria-contaminated environment.