Use of real-time PCR to rule out Marek's disease in the diagnosis of peripheral neuropathy.

This article reports nine cases of neurological disease in brown layer pullets that occured in various European countries between 2015 and 2018. In all cases, the onset of neurological clinical signs was at 4-8 weeks of age and they lasted up to 22 weeks of age. Enlargement of peripheral nerves was the main lesion observed in all cases. Histopathological evaluation of nerves revealed oedema with moderate to severe infiltration of plasma cells. Marek's disease (MD) was ruled out by real-time PCR as none of the evaluated tissues had a high load of oncogenic MD virus (MDV) DNA, characteristics of MD. Based on the epidemiological data (layers with clinical signs starting at 5-8 weeks of age), gross lesions (peripheral nerve enlargement with a lack of tumours in other organs), histopathological lesions (oedema and infiltration of plasma cells), and no evidence of high load of MDV DNA, we concluded that those cases were due to peripheral neuropathy (PN). PN is an autoimmune disease easily misdiagnosed as MD, leading to a costly enforcement of the vaccination protocol. Additional vaccination against MD does not protect against PN and could worsen the clinical signs by over-stimulating the immune system. Differential diagnosis between PN and MD should always be considered in cases of neurological disease with enlargement of peripheral nerves as the only gross lesion. This case report shows for the first time how real-time PCR to detect oncogenic MDV is a very valuable tool in the differential diagnosis of PN and MD.

Comparison of infectious bursal disease live vaccines and a HVT-IBD vector vaccine and their effects on the immune system of commercial layer pullets.

Infectious bursal disease (IBD) is an economically important disease affecting poultry production worldwide. Previous experimental studies indicated that IBD live vaccination may induce transient immunosuppression, leading to suboptimal vaccine responses and therefore insufficient protection against other pathogens. Layer pullets are commonly not only vaccinated against IBD within their rearing period, but also against a variety of other pathogens. Therefore, it is of interest to investigate the effects of different IBD vaccination regimes on conventionally applied vaccines against other pathogens, and possible protection against widely spread very virulent IBD-virus (vvIBDV). A commercially available Herpesvirus of turkey vector vaccine (vHVT-IBD) expressing viral protein 2 of IBDV, and two IBD live vaccines were compared in commercial pullets for their effects on circulating B cell numbers, the ability of vaccinated birds to mount a humoral immune response against different antigens as well as their ability to induce protection against vvIBDV challenge. The results of this study demonstrate a clear immunosuppressive effect of the intermediate plus IBD live vaccine on the humoral branch of the immune system. On the other hand, no detectable effects of vHVT-IBD vaccination on these parameters were observed. All tested IBD vaccines protected against clinical IBD, although none induced sterile immunity in commercial layer pullets. vHVT-IBD-vaccinated birds showed significantly less lesions after vvIBDV challenge than IBD live-vaccinated or non-vaccinated birds (P < 0.05). Therefore, vHVT-IBD may be a suitable alternative to conventional IBD live vaccines, and may be applied even in the presence of maternally derived IBD antibodies without induction of detectable humoral immunosuppression.

Assessment of impact of a novel infectious bursal disease (IBD) vaccination programme in breeders on IBD humoral antibody levels through the laying period.

OBJECTIVES: The purpose of this study was to assess whether broiler breeders vaccinated in ovo with a Vaxxitek (HVT&IBD) (Merial) plus an inactivated IBD vaccine prior to the onset of lay had a significantly different humoral IBD antibody response to broiler breeders vaccinated solely with Vaxxitek (HVT&IBD) (Merial) in ovo. In addition, maternally derived antibody (MDA) passed to the progeny of these two breeders flocks was also compared at three time points during lay. DESIGN: The study was a case-control study where the two flocks were the same breed, reared on the same farm and transferred to the same laying farm, the only difference between the flocks being the IBD vaccination programme. The humoral IBD antibody response in the flocks and their progeny was measured using two commercial ELISA tests and a serum neutralisation (SN) test. RESULTS: There was no significant difference (P<0.05) in the humoral IBD antibody response in the two breeder flocks as measured by ELISA test except at a single time point at 22 weeks when measured by BioChek ELISA and at 60 weeks when measured by IDEXX ELISA. There was no significant difference (P<0.05) in the humoral IBD antibody response in the two breeder flocks as measured by SN test except at 27 and 55 weeks. There was no significant difference (P<0.05) in the levels of MDA passed to progeny of these two breeder flocks as measured by ELISA or SN test. CONCLUSIONS: It is proposed that a single vaccination with Vaxxitek (HVT&IBD) (Merial) will provide a similar level of IBD protection to breeders and their progeny as a Vaxxitek (HVT&IBD) (Merial) plus inactivated IBD vaccine, vaccination programme. This novel IBD vaccine provides additional options for vaccination programmes for broiler breeders without impacting on the protection of the broiler progeny.

Duration of immunity induced in chickens by an attenuated live Salmonella enteritidis vaccine and an inactivated Salmonella enteritidis/typhimurium vaccine.

The aim of this study was to examine the duration of immunity of different vaccination schemes using the S. enteritidis live vaccine Gallivac Se and the S. enteritidis-S. typhimurium inactivated vaccine Gallimune Se+St. Three groups of Lohman Brown chickens were used. Group one was vaccinated three times orally with Gallivac Se at weeks one, seven and 13 of age. Group two was vaccinated twice orally with Gallivac Se in weeks one and seven and once i.m. with Gallimune Se+St in week 14 of age. A third group was not vaccinated and served as the control group. Eight randomly selected chickens from each of the three groups were challenged with a nalidixic acid resistant S. enteritidis PT4 strain in weeks 24, 51 and 71 of age and the same number of animals were challenged with a S. typhimurium DT 104 strain in weeks 26, 54 and 73 (75) of age.The chickens were euthanised seven days post challenge and the number of challenge strain organisms (log10 cfu) in the liver and on caecal mucosa was determined.The quantitative investigation of the challenge strain in the liver and caecal mucosa revealed a statistically significant (p < 0.05) lower challenge strain burden in the vaccinated groups compared with the non-vaccinated control group up to week 71 (73) of age. The protective effects were demonstrated for both challenge strains.