Active virological surveillance in backyard ducks in Bangladesh: detection of avian influenza and gammacoronaviruses

ABSTRACT

Domestic waterfowl play an important role in the perpetuation and transmission of avian pathogens including avian influenza viruses (AIV) of low and high pathogenicity, which pose severe economic and public health concerns in Bangladesh. This study focused on active surveillance of several avian viral pathogens with a special reference to AIV in selected backyard duck populations in Bangladesh. A total of 500 pooled oropharyngeal and cloacal samples from individual ducks of four districts were tested by real time PCRs for the presence of AIV, avian avulavirus-1, anatid herpesvirus-1, avian parvovirus, avian bornavirus and avian coronavirus. The investigation identified 27 (5.4%) ducks positive for AIV and 12 (2.4%) positive for avian coronavirus. In 13 samples, RNA specific for AIV H4N6 was detected. Phylogenetic analysis of the AIV haemagglutinin H4 and neuraminidase N6 genes suggested a clustering of Bangladeshi AIV H4N6 in Eurasian lineage group 2. Other AIV positive samples had very low virus loads (Cq?>?36) and were not subtyped. Coronaviral sequences of a fragment of the polymerase gene were related to Eurasian-Australian duck gamma-coronaviruses. Our current active surveillance in free-range domestic backyard ducks in Bangladesh failed to detect highly pathogenic (HP) AIV in contrast to our previous passive monitoring study. Nevertheless, active monitoring of domestic duck populations may be important to highlight presence and transmission dynamics of economically less important AIV that still may serve as reassortment partners for the generation of new HP and zoonotic AIV.

RESEARCH HIGHLIGHTS

• Active surveillance for viral pathogens in domestic free-range backyard ducks.

• Detection of avian influenza virus subtype H4N6.

• First identification of avian gammacoronavirus in ducks in Bangladesh.

     

Pathology of clade 2.3.2.1 avian influenza virus (H5N1) infection in quails and ducks in Bangladesh

We performed pathological and molecular virological investigation of three outbreaks of highly pathogenic avian influenza (HPAI) in a quail farm and two duck farms of Mymensingh and Netrokona districts of Bangladesh in 2011. HPAI viruses of subtype H5N1 were detected from all three outbreaks and phylogenetic analysis of HA gene sequence placed the viruses into clade 2.3.2.1. The outbreak in the quail farm was characterized by acute death with 100% mortality within two days. Marked haemorrhages and congestion with necrotic and inflammatory lesions in the respiratory tract, liver, pancreas and kidneys were the major gross and histopathological lesions. In the case of ducks, nervous signs were the remarkable clinical manifestations and the mortality was around 10%. No significant gross lesions were observed at necropsy. Non-purulent encephalitis with gliosis and neuronal degeneration was observed on histopathological examination. By immunohistochemistry, viral antigen could be detected in different organs of both quails and ducks. This study records varying clinical and pathological manifestations of HPAI in ducks and quails following natural infection with the same strain of the virus.

RESEARCH HIGHLIGHTS

• HPAIV of clade 2.3.2.1 was detected from clinical outbreaks in quails and ducks

• Sudden death with severe haemorrhages in various organs was found in quails

• Pronounced nervous signs with non-purulent encephalitis were observed in ducks

• Viral antigen could be localized in different organs by immunohistochemistry

     

Cross-species transmission of poultry pathogens in backyard farms: ducks as carriers of chicken viruses

ABSTRACT

In backyard farms of Lao People’s Democratic Republic, mixed-species rearing of poultry is a breeding-ground for cross-species transmission. Here, the epidemiology of viruses circulating among backyard poultry in Vientiane Province was assessed to guide future control strategies. Oral/tracheal and cloacal swabs, collected from 605 poultry (308 ducks, 297 chickens) between 2011 and 2015, were screened by PCR for Newcastle disease virus (NDV), coronavirus (CoV) and chicken anaemia virus (CAV). Chicken sera were screened for anti-NDV antibodies by ELISA. Statistical and phylogenetic analyses revealed transmission patterns and relationships.

Closely related strains co-circulated in chickens and ducks. While CoV RNA was detected in oral/tracheal swabs of 9.3% of the chickens and 2.4% of the ducks, rates were higher in faecal swabs of both species (27.3% and 48.2%). RNA of infectious bronchitis virus (IBV) and duck CoV was found in faecal swabs of chickens (19.7% and 7.1%) and ducks (4.1% and 44.1%). Moreover, DNA of the generally chicken-specific CAV was detected in oral/tracheal swabs of chickens (18.1%) and, sporadically, of ducks (2.4%). Despite serological evidence of NDV circulation or vaccination (86.9%), NDV RNA was not detected. We found a high prevalence and indication for cross-species transmission of different CoV strains in backyard poultry. Interestingly, ducks served as biological, or at least mechanical, carriers of viral strains closely related not only to IBV, but also to CAV. Bird containment and poultry species separation could be first steps to avoid cross-species transmission and emergence of novel strains with broad host range and enhanced pathogenicity.

RESEARCH HIGHLIGHTS

• High rates of avian viruses were detected by PCR in backyard poultry from Lao PDR.

• Diverse coronavirus and chicken anemia virus strains co-circulated.

• Phylogenetic analyses suggested virus transmission between chickens and ducks.

• Serological evidence of Newcastle disease was found, but viral RNA was not detected.

     

Physiological,biochemical and histopathological changes associated with heatstroke in the galah (Eolophus roseicapilla) and rock dove (Columba livia)

The pathophysiology of heat illnesses in birds has not been well characterized. In this study, we describe the changes in heart rate, respiratory rate, blood biochemistry and histopathological findings in galahs and rock doves after heat exposure under standardized conditions designed to induce heatstroke. Birds in the heat-exposed group were exposed to environmental heat stress and compared to control birds. Both groups of birds were under general anaesthesia throughout the experiment and serial blood collections were performed for biochemical analyses, while organs were collected at the end of the experiment for histopathology. No electromyography traces consistent with the onset of heat cramps were observed in any of the birds. Biochemical changes suggestive of skeletal muscle and hepatocellular injury, including hyperkalaemia and increased serum muscle and hepatic enzyme activities, were often observed in heat-exposed galahs and rock doves at the onset of heatstroke. Microscopic analyses did not reveal any significant cardiac changes, although some lungs had signs of acute congestion. Some heat-exposed rock doves had microscopic changes indicative of necrosis in the pectoral muscle. There were significant hepatic changes in some heat-exposed galahs, but not in rock doves. This suggests that there may be species differences amongst birds in the organs most affected by heatstroke. The observed species differences in the physiological, biochemical and histopathological changes indicate that bird species should be studied separately for clinical syndromes such as heatstroke.

RESEARCH HIGHLIGHTS

• Biochemical changes suggestive of skeletal muscle and hepatocellular injury in heat-exposed galahs and rock doves at the onset of heatstroke

• No electromyography traces consistent with the onset of heat cramps were observed

• Some heat-exposed rock doves had indications of necrosis in the pectoral muscle

• There were significant hepatic changes in some heat-exposed galahs

     

Genotyping of Riemerella anatipestifer by ERIC-PCR and correlation with serotypes

Riemerella anatipestifer (RA) is a widely distributed bacterial pathogen of birds responsible for remarkable losses to poultry production, especially among waterfowl. We characterized the genomic diversity of 166 field isolates of RA, collected from geese and ducks, using enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR). The field strains and five reference strains showed 17 distinct patterns consisting of five to 12 bands ranging from approximately 150–1800bp. The majority of the strains belonged to two closely related ERIC-PCR types (A and B), while the other types contained only a few isolates each. There was no association between ERIC-PCR type and host species, place, or year of isolation; however the ERIC-PCR pattern was correlated with serotype for most isolates. The majority of serotype 1 strains (101/107) belonged to ERIC-PCR type A while the remaining six strains represented five different ERIC-PCR types (D, G, L, M, and O). Serotypes 1,7 and 7 corresponded to ERIC-PCR types B and C, respectively. Serotypes 2, 4, and 10 could be subdivided by ERIC-PCR revealing two to four patterns within each serotype. These results indicate that ERIC-PCR may be a suitable technique for the molecular identification of RA serotypes, and the detection of subtypes within certain serotypes may aid further epidemiological investigations.

RESEARCH HIGHLIGHTS

• ERIC-PCR analysis of field R. anatipestifer strains revealed 17 distinct patterns

• Most strains belonged to two closely related ERIC-PCR types

• Serotype 1 was the most prevalent serotype representing 64.5% of the strains

• ERIC-PCR may be suitable for molecular identification of R. anatipestifer serotypes

     

Protection afforded by avian influenza vaccination programmes consisting of a novel RNA particle and an inactivated avian influenza vaccine against a highly pathogenic avian influenza virus challenge in layer chickens up to 18 weeks post-vaccination

The efficacies of an oil adjuvanted-inactivated reverse genetics-derived H5 avian influenza virus (AIV) vaccine and an alphavirus replicon RNA particle (RP) AIV vaccine were evaluated in commercial Leghorn chickens. Challenge utilized A/turkey/MN/12582/2015, an isolate representing the U.S. H5N2 Clade 2.3.4.4 responsible for the 2015 highly pathogenic avian influenza (HPAI) epornitic in commercial poultry the United States. As part of a long-term, 36-week study, chickens were challenged at seven weeks of age after receiving a single vaccination, at 18 weeks of age following a vaccine prime-single boost, and at 36 weeks of age after a prime- double-boost. All vaccine programmes reduced virus oropharyngeal and cloacal shedding and mortality compared to the non-vaccinated control birds; however, chickens receiving at least one administration of the RP vaccine generally had diminished viral shedding especially from the cloacal swabbings. A detectable serum antibody response and protection were observed through 18 weeks post-vaccination. Our data suggest that, in conjunction with a comprehensive eradication, enhanced biosecurity and controlled marketing plan, vaccination programmes of commercial layer chickens with novel RP vaccines may represent an important tool for preventing HPAI-related mortalities and decreasing viral load during a catastrophic influenza outbreak.

RESEARCH HIGHLIGHTS

• Immunization of poultry following a vaccination schedule consisting of inactivated and RNA particle vaccines offered significant protection against lethal disease following HPAIV challenge.

• Virus shedding was significantly (P?<?0.05) reduced in chickens vaccinated with either inactivated and/or recombinant vaccines.

• Serum antibody titres were not a reliable indicator of protection.

• An inactivated vaccine containing 384 HAU of the homologous antigen was unable to induce complete protection.

     

Chicken endothelial cells are highly responsive to viral innate immune stimuli and are susceptible to infections with various avian pathogens

It is well established that the endothelium plays a prominent role in the pathogenesis of various infectious diseases in mammals. However, little is known about the role of endothelial cells (EC) as targets for avian pathogens and their contribution to the pathogenesis of infectious diseases in galliform birds. First, we explored the innate immune response of primary chicken aortic endothelial cells (pchAEC), obtained from 18-day-old embryos, to stimulation with pathogen-associated molecular patterns or recombinant chicken interferons (type I, II and III IFNs). In spite of the abundant expression of a number of innate immune receptors, marked cytokine responses to stimulation with pathogen-associated molecular patterns were only seen in pchAEC treated with the TLR3 agonist polyI:C (pI:C) and the MDA5 agonist liposome-complexed polyI:C (L-pI:C), as was assessed by quantitative PCR and luciferase-based IFN-I/NFκB reporter assays. Treatments of pchAEC with IFN-α, IFN-γ and IFN-λ resulted in STAT1-phosphorylation/activation, as was revealed by immunoblotting. Next, we demonstrated that pchAEC are susceptible to infection with a variety of poultry pathogens, including Marek’s disease virus (MDV), infectious bursal disease virus (IBDV), avian pathogenic Escherichia coli (APEC) and Eimeria tenella. Our data highlight that chicken EC are potential targets for viral, bacterial and protozoan pathogens in gallinaceous poultry and may partake in the inflammatory and antimicrobial response. The pchAEC infection model used herein will allow further studies interrogating avian pathogen interactions with vascular EC.

• RESEARCH HIGHLIGHTS

• Use of a well-defined primary chicken aortic endothelial cell (pchAEC) culture model for studying avian host–pathogen interactions.

• pchAEC are responsive to innate immune stimulation with viral pathogen-associated molecular patterns and chicken type I, II and III interferons.

• pchAEC are susceptible to infections with economically important poultry pathogens, including MDV, IBDV, APEC and Eimeria tenella.

     

Individual and stable autoantibody repertoires in healthy individuals

In the era towards precision medicine, we here present the individual specific autoantibody signatures of 193 healthy individuals. The self-reactive IgG signatures are stable over time in a way that each individual profile is recognized in longitudinal sampling. The IgG autoantibody reactivity towards an antigen array comprising 335 protein fragments, representing 204 human proteins with potential relevance to autoimmune disorders, was measured in longitudinal plasma samples from 193 healthy individuals. This analysis resulted in unique autoantibody barcodes for each individual that were maintained over one year’s time. The reactivity profiles, or signatures, are person specific in regards to the number of reactivities and antigen specificity. Two independent data sets were consistent in that each healthy individual displayed reactivity towards 0–16 antigens, with a median of six. Subsequently, four selected individuals were profiled on in-house produced high-density protein arrays containing 23,000 protein fragments representing 14,000 unique protein coding genes. Based on a unique, broad and deep longitudinal profiling of autoantibody reactivities, our results demonstrate a unique autoreactive profile in each analyzed healthy individual. The need and interest for broad-ranged and high-resolution molecular profiling of healthy individuals is rising. We have here generated and assessed an initial perspective on the global distribution of the self-reactive IgG repertoire in healthy individuals, by investigating 193 well-characterized healthy individuals.

• Highlights

• A unique longitudinal profiling of autoantibody repertoires in healthy individuals

• Autoantibody profiles are highly individual and stable over time

• All individuals display IgG binding to human protein fragments

• The specificity of disease associated autoantigens needs to be thoroughly characterized

• The identification of a small set of highly reactive autoantigens

• Importance of stringent antigen and sample specific cut-offs for defining reactivity

     

Dose-dependent differential resistance of inbred chicken lines to avian pathogenic Escherichia coli challenge

Avian pathogenic E. coli (APEC) cause severe respiratory and systemic disease. To address the genetic and immunological basis of resistance, inbred chicken lines were used to establish a model of differential resistance to APEC, using strain O1 of serotype O1:K1:H7. Inbred lines 7₂, 15I and C.B12 and the outbred line Novogen Brown were inoculated via the airsac with a high dose (10⁷ colony-forming units, CFU) or low dose (10⁵ CFU) of APEC O1. Clinical signs, colibacillosis lesion score and bacterial colonization of tissues after high dose challenge were significantly higher in line 15I and C.B12 birds. The majority of the 15I and C.B12 birds succumbed to the infection by 14?h post-infection, whilst none of the line 7₂ and the Novogen Brown birds developed clinical signs. No difference was observed after low dose challenge. In a repeat study, inbred lines 7₂ and 15I were inoculated with low, intermediate or high doses of APEC O1 ranging from 10⁵ to 10⁷ CFU. The colonization of lung was highest in line 15I after high dose challenge and birds developed clinical signs; however, colonization of blood and spleen, clinical signs and lesion score were not different between lines. No difference was observed after intermediate or low dose challenge. Ex vivo, the phagocytic and bactericidal activity of lung leukocytes from line 7₂ and 15I birds did not differ. Our data suggest that although differential resistance of inbred lines 7₂, 15I and C.B12 to APEC O1 challenge is apparent, it is dependent on the infectious dose.

• Research Highlights

• Lines 15I and C.B12 are more susceptible than line 7₂ to a high dose of APEC O1.

• Differential resistance is dose-dependent in lines 15I and 7₂.

• Phagocytic and bactericidal activity is similar and dose independent.

     

Biological characteristics and immunological properties in Muscovy ducks of H5N6 virus-like particles composed of HA-TM/HA-TMH3 and M1

Highly pathogenic avian influenza viruses (HPAIVs), including H5N6 strains, pose threats to the health of humans and poultry. Waterfowl play a crucial role as a reservoir of HPAIVs. Since current influenza vaccines induce poor antibody titres in waterfowl, there is an urgent need to develop an efficient vaccine against H5N6 infection. In this study, we constructed two H5N6 virus-like particles (VLPs) composed of matrix-1 (M1) and haemagglutinin of wildtype (HA-TM) or haemagglutinin with transmembrane domain replacement (HA-TM_H3) (designated as H5N6 VLPs-TM and H5N6 VLPs-TM_H3). Biological characteristics of the composed H5N6 VLPs were compared including localization, expression, contents of HA trimers, thermal stability, morphology and immunogenicity in Muscovy ducks. Our results indicate that the H5N6 VLPs-TM_H3 contained more HA trimers and presented better thermal stability. Moreover, Muscovy ducks immunized with H5N6 VLPs-TM_H3 produced higher titres of HI antibody and IFN-γ compared with those immunized with the same dose of H5N6 VLP-TM, thus providing a promising approach for the development of influenza virus vaccines for waterfowl.

RESEARCH HIGHLIGHTS

• H5N6 VLPs-TM_H3 had more HA trimers and resisted higher temperature than H5N6 VLPs-TM

• H5N6 VLPs-TM_H3 induced higher titre of HI than H5N6 VLPs-TM in Muscovy ducks

     

Fatal necrotic tracheitis by Aviadenovirus in captive Alagoas curassows (Pauxi mitu) extinct from the wild

Extinct from nature, captive young Alagoas curassows (Pauxi mitu) were found agonizing or dead with respiratory disease. Intranuclear inclusion bodies were found in the epithelia of the trachea, associated with marked necrotic tracheitis. An Aviadenovirus was isolated in chicken eggs and characterized genetically with 99% identity to the fowl Aviadenovirus A, as based on the hexon protein gene. This is the first report of respiratory disease caused by Aviadenovirus in any cracid species in Brazil, recommending for stricter biosecurity in the conservation premises.

RESEARCH HIGHLIGHTS

• Fatal tracheitis in curassows extinct from nature was associated with Aviadenovirus A.

• Seven-month-old Alagoas curassows (Aves: Cracidae) died with haemorrhagic tracheitis.

• Aviadenovirus A with 99% identity to fowl adenovirus 1 was detected in dead curassows.

• Fatal tracheitis by Aviadenovirus was described in Pauxi mitu (Aves: Cracidae).

     

Parasitological and molecular survey of scattered parasitism by trichomonads in some avian species in Iran

ABSTRACT

Outbreaks of avian trichomonosis are being reported worldwide; meanwhile, the genetic and virulence variations are under investigation. In this study, the occurrence and genetic variability of oral or faecal trichomonads among various avian species were investigated. Samples obtained from either the oropharyngeal cavity, crop/oesophagus, droppings/cloaca, or conjunctival swabs of avian species were inspected for flagellates. Phylogenetic analysis of partial ITS1-5.8s rRNA-ITS2 sequences from selected samples was performed to investigate the genetic diversity of the isolates. Investigation of 737 birds revealed an infection rate of 15.7% in the upper gastrointestinal tract, 7.3% in the faecal samples, and 0.7% involvement of the conjunctiva. Phylogenetic analysis of partial ITS1-5.8s rRNA-ITS2 sequences from selected samples, identified genotypes A and B of Trichomonas gallinae and genogroups A-C and E of Tetratrichomonas gallinarum. A novel ITS genotype of intestinal trichomonads was also detected in hooded crow (Corvus cornix) and common mynah (Acridotheres tristis). In the present study, in addition to Columbiformes and Falconiformes, trichomonads were detected in Passeriformes and Galliformes with the involvement of organs other than the gastrointestinal tract. Genotype A T. gallinae was detected in domestic pigeons (Columba livia domestica), a laughing dove (Spilopelia senegalensis), a common kestrel (Falco tinnunculus), a budgerigar (Melopsittacus undulates), and a canary (Serinus canaria). Distinct genotype B was detected in a common mynah and a budgerigar. Genogroups A-C of T. gallinarum were also demonstrated in Galliformes and Anseriformes. Furthermore, two novel trichomonad ITS genotypes were detected in hooded crows and a common mynah warranting detailed multi-locus molecular analysis.

RESEARCH HIGHLIGHTS

• ITS diversity of trichomonads was shown in various avian species.

• Diversity of the parasites’ target organ and clinical manifestations was demonstrated.

• Two novel ITS genotype trichomonads from common mynah and hooded crow were identified.

     

Experimental model of oral transmissible AA amyloidosis in quails

ABSTRACT

In poultry and zoo birds, mass outbreaks of amyloid A (AA) amyloidosis are often reported, and horizontal transmission is considered as one of the causes. However, oral transmission of avian AA amyloidosis in nature has been unclear. In order to clarify the horizontal transmission of avian AA amyloidosis, basic research using an appropriate oral transmission model is necessary. In this study, we developed an oral transmission model of AA amyloidosis using quails, and assessed the oral transmission efficiency of AA amyloidosis in quails and mice. Young quails, adult quails, and young mice received inflammatory stimulation with lipopolysaccharide; simultaneously, homogeneous amyloid fibrils were orally or intravenously administered. By histological examination, induction of amyloidosis by oral or intravenous administration of amyloid was confirmed in all species. Furthermore, both quail and murine AA amyloidosis were orally transmitted in a dose-dependent manner. These results support the possibility of horizontal transmission of avian AA amyloidosis in nature. This model will be able to contribute to the elucidation of spontaneous horizontal transmission of avian AA amyloidosis in the future.

RESEARCH HIGHLIGHTS

• Quail AA amyloidosis was orally transmitted in a dose-dependent manner.

• Oral transmission was less efficient than intravenous transmission.

• In-cage horizontal transmission did not occur during 4-week cohabitation.

• Amyloid deposition in tissues of quail was grossly visible.

     

Comparative pathogenicity of two subtypes (hepatitis-type and pancreatitis-type) of duck hepatitis A virus type 1 in experimentally infected Muscovy ducklings

Duck hepatitis A virus type 1 (DHAV-1) causes acute hepatitis with high morbidity and mortality in ducklings of the genera Cairina and Anas and is characterized by ecchymotic haemorrhage and necrosis of the liver surface. Since September 2011, a new subtype of DHAV-1 (named pancreatitis-type DHAV-1) has been isolated. This new subtype is characterized by yellowish or haemorrhagic pancreatitis, but with no significant pathological changes in the liver. To further investigate the difference in pathogenicity between hepatitis-type DHAV-1 and pancreatitis-type DHAV-1, we infected Muscovy ducklings with a hepatitis-type DHAV-1 strain, FZ86, or a pancreatitis-type DHAV-1 strain, MPZJ1206, and then compared the resulting gross lesions, histopathological changes, viral distribution and cellular apoptosis in the liver and pancreas of Muscovy ducklings. The results suggested that FZ86 induced a more efficient viral propagation in the liver than MPZJ1206, and the gross and histopathological lesions were also limited to the liver. However, MPZJ1206 induced more effective viral replication in the pancreas than FZ86. The MPZJ1206-infected Muscovy ducklings showed an obviously yellowed and haemorrhagic pancreas, but with no significant pathological changes in the liver. Furthermore, FZ86 induced notable hepatocyte apoptosis and increased the expression of caspase-3 in the liver, whereas MPZJ1206 caused apoptosis in a large number of acinar epithelial cells and elevated the expression of caspase-3 in the pancreas. Taken together, these results demonstrated that pancreatitis-type DHAV-1 has many new pathogenic features which distinguish it from the hepatitis-type DHAV-1.

RESEARCH HIGHLIGHTS

• Pancreatitis-type DHAV-1 (MPZJ1206) was characterized by pancreatic haemorrhage and yellow discolouration, but with no obvious haemorrhage and necrosis in the liver.

• Pancreatitis-type DHAV-1 (MPZJ1206) exhibits many new pathogenic features which distinguish it from the hepatitis-type DHAV-1 (FZ86).

     

Dermanysuss gallinae attacks humans. Mind the gap!

ABSTRACT

Dermanyssus gallinae is a haematophagous ectoparasite primarily known as a pest of domestic and wild birds. It occasionally feeds on a range of mammals, and, more importantly, is of growing concern in human medicine. This review highlights mite attacks on people working with poultry, and updates the increasing incidence of dermanyssosis in urban environments in Europe. Although several cases of dermanyssosis have been documented, there are a number of reasons why diagnosis of D. gallinae infestations in humans is likely to be underestimated. Firstly, medical specialists are not well aware of D. gallinae infestations in humans. There is also a lack of collaboration with specialists from other disciplines. The problem is compounded by misdiagnoses and by the lack of diagnostic tools. We review the literature on human dermanyssosis cases in Europe, and also provide information on the epidemiology, clinical, histo-pathological and immunological aspects of dermanyssosis. We stress the need for improved recognition of this challenging infestation in humans, and provide straightforward recommendations for health practitioners, starting with collection of the correct anamnestic information and including appropriate management methods for case recognition and resolution. Finally, we indicate the most urgent areas to be addressed by future research.

RESEARCH HIGHLIGHTS

• Dermanyssus gallinae is of growing concern in human medicine.

• Most physicians are not well aware of dermanyssosis in humans.

• Bio-epidemiological and clinical aspects of this ectoparasitosis are highlighted.

• Practical key actions for diagnosis and correct management of infestation in humans are provided.

     

How can Dermanyssus gallinae (De Geer 1778) (Acari: Anactinotrichida: Dermanyssidae) walk upwards on slippery surfaces?

ABSTRACT

Scanning electron microscopy observations of the distal leg region of the poultry red mite Dermanyssus gallinae (De Geer 1778) identified the presence of a compound ambulacrum, the part of the leg that contacts the substratum when the mite walks. The ambulacrum is comprised of a praetarsus (the ambulacrum stalk), a pulvillus and two claws. The pulvillus is a weakly sclerotized structure that can be partly expanded or retracted in the praetarsus. When expanded, the pulvillus shows a cushion-like shape which can, as a result of its soft surface, function as a sucker, thus allowing D. gallinae to adhere to a smooth surface. When traversing an irregular surface, or clinging to a soft surface, the mite retracts the pulvillus and uses only its strongly sclerotized movable claws. These observed morphological adaptations explain the ability of D. gallinae to climb upwards on a slippery surface, resist an air flux, walk on smooth and rigid feathers of its avian hosts, and cling to the bird’s or human's soft skin. This knowledge is important to better understand the attachment mechanism of this species to its host and to the substratum on which it moves, and also to provide insight into the circumstances under which it is able to move.

RESEARCH HIGHLIGHTS

• The ambulacrum is the distal part of the leg touching the substratum

• D. gallinae’s ambulacrum consists of a praetarsus, a pulvillus and two claws

• The weakly sclerotized pulvillus can be part expanded/retracted in the praetarsus

• The expanded pulvillus functions as a sucker to adhere to smooth surfaces

• The claws are used to walk on an irregular surface or cling to a soft surface

     

Pathogenicity and genomic characterization of a novel avian orthoreovius variant isolated from a vaccinated broiler flock in China

Avian orthoreovirus (ARV) infections of broiler flocks cause arthritis/tenosynovitis syndrome and significant economic losses. ARV variants were detected in the USA and Canada. Viral arthritis/tenosynovitis syndrome has occurred frequently in China in recent years. In this study, a variant ARV strain associated with viral arthritis/tenosynovitis syndrome was isolated from broilers and designated as LY383. Genomic sequence and phylogenetic analysis of the σC nucleic acid and amino acid sequences revealed that the isolate was closely related to ARV field strains Reo/PA/Layer/01224B/14, Reo/PA/Broiler/1551/13, GA/14602/2014, GA/13569/2013 and GA/13542/2013, in cluster V, but distinct from most Chinese field strains or commercial vaccine strains. Experimental challenge showed that the isolate could cause arthritis/tenosynovitis syndrome in broilers, which possessed a high level of maternal antibodies induced by commercial ARV vaccines (S1133, 1733 and T98). Furthermore, viral nucleic acid could be detected in cloacal swabs of all challenged birds throughout the entire test from 5?dpi onward. These results suggest that a novel ARV genotype emerges and might become prevalent in broiler flocks in China.

RESEARCH HIGHLIGHTS

• A variant avian orthoreovirus was isolated from a vaccinated broiler flock in North China.

• The ARV field strain was distinct from previous China-origin ARV isolates and vaccine strains.

• The current commercial ARV vaccine could not provide effective protection of broilers against the field isolate infection.

• These findings indicated that variant ARV field strains might become frequent in broiler flocks in China and effective measures should be conducted to prevent and control the disease.

     

Co-infections of chickens with avian influenza virus H9N2 and Moroccan Italy 02 infectious bronchitis virus: effect on pathogenesis and protection conferred by different vaccination programmes

ABSTRACT

Since the emergence of low pathogenic avian influenza (LPAI) H9N2 viruses in Morocco in 2016, severe respiratory problems have been encountered in the field. Infectious bronchitis virus (IBV) is often detected together with H9N2, suggesting disease exacerbation in cases of co-infections. This hypothesis was therefore tested and confirmed in laboratory conditions using specific-pathogen-free chickens. Most common field vaccine programmes were then tested to compare their efficacies against these two co-infecting agents. IBV γCoV/chicken/Morocco/I38/2014 (Mor-IT02) and LPAI virus A/chicken/Morocco/SF1/2016 (Mor-H9N2) were thus inoculated to commercial chickens. We showed that vaccination with two heterologous IBV vaccines (H120 at day one and 4/91 at day 14 of age) reduced the severity of clinical signs as well as macroscopic lesions after simultaneous experimental challenge. In addition, LPAI H9N2 vaccination was more efficient at day 7 than at day 1 in limiting disease post simultaneous challenge.

RESEARCH HIGHLIGHTS

• Simultaneous challenge with IBV and AIV H9N2 induced higher pathogenicity in SPF birds than inoculation with IBV or AIV H9N2 alone.

• Recommended vaccination programme in commercial broilers to counter Mor-IT02 IBV and LPAIV H9N2 simultaneous infections: IB live vaccine H120 (d1), AIV H9N2 inactivated vaccine (d7), IB live vaccine 4-91 (d14).

     

Synergistic effect of a combination of nicarbazin and monensin against coccidiosis in the chicken caused by Eimeria spp.

ABSTRACT

A clinical study was made into the abilities of nicarbazin and monensin and a nicarbazin?+?monensin combination to control Eimeria acervulina, E. maxima, and E. tenella in chickens. When included in the feed, at concentrations of 40?ppm nicarbazin or 40?ppm monensin, these products showed partial efficacy evaluated by daily weight gain (DWG) but no activity judged by daily feed intake (DFI) or feed conversion ratio (FCR). By contrast, the combination of 40?ppm nicarbazin?+?40?ppm monensin provided complete control of infection judged by greater DWG and DFI, and lower FCR. Monensin at a concentration of 40?ppm was ineffective in preventing lesions caused by all three species. Nicarbazin at a concentration of 40?ppm was unable to suppress lesions of E. acervulina and E. maxima but was able to suppress lesions caused by E. tenella. Nicarbazin 40?ppm?+?monensin 40?ppm suppressed lesions of all three species.

RESEARCH HIGHLIGHTS

• Nicarbazin or monensin at 40 ppm gave only partial control of Eimeria spp.

• A combination of 40 ppm nicarbazin + 40 ppm monensin controlled DWG, DFI and FCR.

• Nicarbazin or monensin at 40 ppm did not suppress all Eimeria spp. lesions.

• Nicarbazin 40 ppm + monensin 40 ppm suppressed lesions of all three species.

     

Biological control as an alternative to synthetic fungicides for the management of grey and blue mould diseases of table grapes: a review

Abstract

Grey and blue mould diseases are among the most important diseases of grapes worldwide. They are causing extensive decay in postharvest grapes. Chemical fungicides remain the primary treatment for managing these diseases. However, consumer’s interest in organic produce, restrictions on chemical use by some countries, and concerns about human and environmental safety have driven research to identify safe and effective alternatives. Among several alternative approaches, the use of biological control agents (BCAs) is getting more acceptance and has been comprehensively studied. This review summarizes the use of BCAs as a postharvest treatment to control the postharvest grey and blue mould of grapes. The review also emphasizes the economic importance of these two major postharvest diseases of grapes. In addition, other non-chemical postharvest treatments, the advantage of an integrated approach and finally problems, challenges, and future trends of the BCAs are described. Several yeasts that have a promising result to control grey and blue mould disease of grapes are thoroughly reviewed. The current market share of BCAs and their future directions on commercialization are also suggested in this review.

• Biocontrols can be a potential control method for postharvest diseases of fruits and vegetables in place of chemical fungicides.

• Antagonistic yeasts have high ability to suppress fungal growth.

• Integrated approach utilizes a combination approaches, which often results in a synergistic effect to control the diseases.

• USA and Europe are currently the largest markets for biocontrol products.