Investigation of field outbreaks of Turkey haemorrhagic enteritis in Hungary

Abstract

Epidemiological, pathological, serological and virological investigations are reported on turkey haemorrhagic enteritis virus (THEV) infection in Hungarian turkey flocks. The pathogenesis of infection in experimentally infected turkeys and chickens, as well as the usefulness of polymerase chain reaction (PCR)/sequencing method for epidemiological investigation and for the differentiation of vaccine and field strains of THEV was also studied. Since the first recognition of the disease in Hungary in the late 1970s, until recently the disease has been diagnosed sporadically in its mild form. In the last few years (2000)(2001)(2002)(2003)(2004)(2005), however, the number of outbreaks and the severity of the disease increased (9-23 affected flocks/year). Most of the outbreaks occurred at the age of 6 to 8 weeks and was complicated with Escherichia coli infection. The antibody levels to THEV in turkey flocks gradually declined till 5-7 weeks of age, and then they increased sharply due to natural infection with THEV. The immune response to vaccination (at 5 weeks of age) showed no significant antibody level increase one week postvaccination, but four weeks later the antibody level reached high values and then remained at this high level. The agar gel immunodiffusion (AGID) test to detect turkey adenovirus A (TAdV-A) antigen and PCR methods for THEVspecific DNA gave similarly positive results if spleens with pathognomonic lesions were tested; however, PCR proved to be more sensitive in cases with less characteristic pathological lesions. Nucleotide sequence alignment of PCR products amplified from Hungarian field strains and the Domermuth vaccine strain and that of the published THEV hexon sequences in GenBank database revealed slight differences between the sequences.

The immune response of young turkeys to haemorrhagic enteritis virus infection at different levels and sources of methionine in the diet

“…. An increased mortality rate due to superinfections with E. coli bacteria is usually observed between week 2 and 4 of life after infection with a low-pathogenic HE virus and may range from 2.5 to 6.5% weekly [24]. Considering the frequent exposure of turkeys to HEV infections and, consequently, their suppressed immunity, any actions aimed at aiding defence mechanisms in the course of the infection should be deemed highly desirable and valuable.…”

Detection of Astrovirus, Coronavirus and Haemorrhagic Enteritis Virus in Turkeys with Poult Enteritis Mortality Syndrome in Turkey

“…The fact that the investigation of rotavirus and reovirus in PEMS-associated turkeys was beyond the scope of the current study can be interpreted as a deficiency. On the other hand, the presence of TCoV and HEV has been reported at different rates in both PEMSassociated and clinically healthy turkey flocks in various studies (Carver et al, 2001, Culver et al, 2006Villarreal et al, 2006;Palya et al, 2007;Teixeira et al, 2007;DomanskaBlicharz et al, 2010;Lojkic et al, 2010).…”

Haemorrhagic enteritis of turkeys – current knowledge

“…Furthermore, the infection with HEV has been found to predispose birds to enteropathogenic E. coli infection in either natural condition or during experimental studies Sponenberg et al 1985;van den Hurk et al 1994;Saif 1998;Palya et al 2007;Giovanardi et al 2014) and clostridial dermatitis (Thachil & Nagaraja 2013). HEV infection also depresses the response to vaccines, as they were shown to produce low antibody titres during Newcastle disease (ND) vaccination .…”

“…Recently, the availability of whole genome sequence data has enabled the development of standard (Hess et al 1999), nested (Beach et al 2009b) and real-time (Beach 2006) PCR assays for detection of viral DNA in splenic tissue samples (Hess et al 1999). PCR is more sensitive than agar gel immunodiffusion test in diagnosing HEV infection in cases where pathological lesions were mild (Palya et al 2007). Also, DNA from group II viruses like MSDV or splenomegaly virus can be differentiated by using different restriction endonucleases (RE) like Bgl II, EcoR I, Hind III, Hha I and Xho I.…”