Avian Pathology最新文献

Research highlights: The cost of coccidiosis in chickens fluctuates considerably, peaking in 2022.Three new Eimeria species can infect chickens and escape current vaccines.Eimeria infection exerts wide-ranging effects on enteric microbiota.

The haemolysin co-regulatory protein (Hcp) plays a significant role in the pathogenicity of avian pathogenic Escherichia coli (APEC) as an effector protein of the type VI secretion system (T6SS) to the host. Meanwhile, mitochondria in the host are the target of effector proteins of various secretion systems. Here, we explored the effects of APEC effector Hcp2b on the mitochondria of DF-1 cells and found that Hcp2b results in damage in mitochondria. Next, 68 target proteins in DF-1 cell lysates were identified that interacted with Hcp2b by streptavidin-biotin pull-down assay combined with LC-MS/MS, among which ADP/ATP transporter carrier (SLC25A4) is a mitochondria-associated protein; protein docking analysis showed that Hcp2b binds well to SLC25A4. Therefore, we hypothesize that the Hcp2b contributes to mitochondrial damage in DF-1 cells through interaction with the SLC25A4.

Reticuloendotheliosis virus (REV) is a species of the genus Gammaretrovirus that can cause neoplasia, immunosuppression, and runting-stunting syndrome. To show the clinical relevance of REV is complicated, and requires the demonstration of the virus, REV antibodies, the presence of typical gross and microscopic lesions, and the exclusion of other oncogenic agents in the case of the presence of tumours. Under field conditions, the first tests to be used might be a commercially available REV antibody ELISA or an RT-PCR to detect the REV genome. In this short paper, we present the experiences with two commercially available ELISAs and RT-PCR that we have gained from a REV outbreak on a large multi-age layer farm and many follow-up tests on samples from control farms with and without a known history of REV and fowlpox virus (FPV). In the field, some of the FPV field strains contain large inserts of the REV genome that might interfere with REV testing. The results of the ELISAs on sera from REV- and FPV- unsuspected flocks suggested that the cut-offs of both ELISAs were somewhat low resulting in a lower specificity. However, cut-offs of 2000 and 3050 for the IDEXX and BioChek ELISAs, respectively, gave an agreement of 100%, suggesting that these cut-offs might be advisable to use. The use of the combination of RT-PCR for REV and PCR for FPV proved to be very useful in separating REV infections from FPV infections. The results of our extended field study can help to interpret REV testing results.

Research highlights: Avian reovirus-infected hens shed virus heavily at 2-3 days post-inoculation.Shedding became minimal after 5-7 days post-inoculation.ARV variants offered 100% protection in hens upon subsequent infections.Infected hens maintained normal egg production with no observable clinical signs.

ABSTRACTThe efficacy of two Mycoplasma gallisepticum commercially available vaccines administered singly or in combination was evaluated in two trials; in both trials, specific-pathogen-free (SPF) chickens were vaccinated with the live attenuated F-strain vaccine at 5 weeks of age (WOA), an inactivated M. gallisepticum bacterin at 9 and 13 WOA, or both vaccines. In the first trial, groups of vaccinated birds, along with controls, were challenged via aerosol with virulent R-strain at 22 and 41 weeks of age. All of the vaccine programs evaluated showed a statistically significant reduction in colonization with the challenge strain following challenge at either timepoint. However, only the programs including the live vaccine also showed significant protection from respiratory lesions and ovarian regression; and although there were numerical differences indicating benefits of a combined (live + bacterin) program, the addition of bacterins did not enhance (or reduce) the efficacy of the F-strain vaccine in a statistically significant manner (P ≤ 0.05). In the second trial, groups of vaccinated birds, along with controls, were challenged via aerosol with different doses of virulent M. gallisepticum R-strain at 17 weeks of age. Both vaccination programs in this trial (live only and live + bacterin) resulted in significant protection against challenge strain colonization and air sac lesions (P ≤ 0.05); In addition, the live + bacterin program showed significantly improved results with respect to colonization with the challenge strain as well as protection from air sac lesions compared to the live vaccine alone (P ≤ 0.05).

Infectious laryngotracheitis (ILT) poses a significant threat to the poultry industry, and vaccines play an important role in protection. However, due to the increasing scale of poultry production, there is an urgent need to develop vaccines that are suitable for convenient immunization methods such as spraying. Previous studies have shown that Newcastle disease virus (NDV)-ILT vaccines administered via intranasal and intraocular routes to commercial chickens carrying maternally-derived antibodies (MDAs) are still protective against ILT. In this study, a recombinant NDV (rNDV) was generated to express infectious laryngotracheitis virus (ILTV) glycoprotein B (gB), named rLS-gB, based on a full-length cDNA clone of the LaSota strain. The protective effect of different doses of rLS-gB administered by spray vaccination to commercial chickens at 1 d of age (doa) was evaluated. The chickens were exposed to 160-μm aerosol particles for 10 min for spray vaccination, and no adverse reactions were observed after vaccination. Despite the presence of anti-NDV MDAs and anti-ILTV MDAs in chickens, the ILTV- and NDV-specific antibody titres were significantly greater in the vaccinated groups than in the unvaccinated group. After challenge with a virulent ILTV strain, no clinical signs were observed in the 10⁷ EID₅₀/ml group compared to the other groups. Furthermore, vaccination with 10⁷ EID₅₀/ml rLS-gB significantly reduced the ILTV viral load and ameliorated gross and microscopic lesions in the trachea of chickens. Overall, these results suggested that rLS-gB is a safe and efficient candidate spray vaccine for ILT and is especially suitable for scaled chicken farms.

Beside biosecurity, vaccination is important for Mycoplasma synoviae (MS) control as it has been shown to contribute to the reduction of economic impact and, experimentally, also lessens horizontal transmission. In this study, the effect of MS live vaccination on horizontal transmission was quantified under field conditions by analysing 4-year MS monitoring data from non-MS-vaccinated broiler and layer breeders and MS-vaccinated broiler breeders with good biosecurity in single-age housing systems. Flocks were monitored at 20 and 30 weeks of age and every 12 weeks thereafter. At every sampling, 60 blood samples or 24 tracheal swabs were tested using rapid plate agglutination test and ELISA serially or MS DIVA PCR, respectively. The MS incidence rate was calculated and the association with vaccination was analysed by logistic regression. The average MS incidence rate per 1000 weeks was 11.6 cases for non-MS-vaccinated broiler breeders and decreased from 29.6 to 5.6 cases with successive vaccinated production cycles. In non-MS-vaccinated layer breeders it was 3.6. A significant negative association with MS incidence was found after vaccinating four to six successive production cycles compared to non-MS-vaccinated or only one production cycle vaccinated breeders (odds ratio (OR) = 0.23, P = 0.05 & OR = 0.12, P = 0.01, respectively). A significant negative association with MS in non-MS-vaccinated layer breeders (OR = 0.29, P = 0.00) was observed compared to non-MS-vaccinated broiler breeders, possibly due to more controlled contact structures within the layer breeder industry. The results suggest that vaccination and control of contacts contribute to the reduction of between-farm MS transmission.

Ascites syndrome (AS) in broiler chickens, also known as pulmonary arterial hypertension (PAH), is a significant disease in the poultry industry. It is a nutritional metabolic disease that is closely associated with hypoxia-inducible factors and rapid growth. The rise in pulmonary artery pressure is a crucial characteristic of AS and is instrumental in its development. Hypoxia-inducible factor 1α (HIF-1α) is an active subunit of a key transcription factor in the oxygen-sensing pathway. HIF-1α plays a vital role in oxygen homeostasis and the development of pulmonary hypertension. Studying the effects of HIF-1α on pulmonary hypertension in humans or mammals, as well as ascites in broilers, can help us understand the pathogenesis of AS. Therefore, this review aims to (1) summarize the mechanism of HIF-1α in the development of pulmonary hypertension, (2) provide theoretical significance in explaining the mechanism of HIF-1α in the development of pulmonary arterial hypertension (ascites syndrome) in broilers, and (3) establish the correlation between HIF-1α and pulmonary arterial hypertension (ascites syndrome) in broilers. HIGHLIGHTSExplains the hypoxic mechanism of HIF-1α.Linking HIF-1α to pulmonary hypertension in broilers.Explains the role of microRNAs in pulmonary arterial hypertension in broilers.

Research highlights: Galleria mellonella larvae are a viable model for determining APEC pathogenicity.Larval disease score is the main variable for determining APEC pathogenicity.Response variables should be evaluated up to 24 h post-inoculation.