The 2016–17 European outbreak of H5N8 HPAIV (Clade 2.3.4.4b) affected a wider range of avian species than the previous H5N8 outbreak (2014–15), including an incursion of H5N8 HPAIV into gamebirds in England. Natural infection of captive-reared pheasants (Phasianus colchicus) led to variable disease presentation; clinical signs included ruffled feathers, reluctance to move, bright green faeces, and/or sudden mortality. Several birds exhibited neurological signs (nystagmus, torticollis, ataxia). Birds exhibiting even mild clinical signs maintained substantial levels of virus replication and shedding, with preferential shedding via the oropharyngeal route. Gross pathology was consistent with HPAIV, in gallinaceous species but diphtheroid plaques in oropharyngeal mucosa associated with necrotising stomatitis were novel but consistent findings. However, minimal or modest microscopic pathological lesions were detected despite the systemic dissemination of the virus. Serology results indicated differences in the timeframe of exposure for each case (n = 3). This supported epidemiological conclusions confirming that the movement of birds between sites and other standard husbandry practices with limited hygiene involved in pheasant rearing (including several fomite pathways) contributed to virus spread between premises.

Stress can exert modulatory effects on pain perception in animals, as exposure to a stressor can result in either the reduction or amplification of the perceived severity of pain. These phenomena are widely described as stress-induced analgesia (SIA) and stress-induced hyperalgesia (SIH). The two are mediated by the same underlying mechanisms, but occur due to different stressors and different responses from the pain pathway. SIA and SIH have been demonstrated with a variety of stress and pain stimuli in rodents, humans and other mammals. There is some evidence that SIA occurs in birds and that they have the neurological systems and brain regions necessary for SIH. Tonic immobility (TI) is related to SIA in mammals, and there is evidence the avian brain is compatible with TI having analgesic effect, but it could have a hyperalgesic effect. This review looks at the mechanisms and evidence of SIA, SIH and TI in mammals and discusses evidence relating to the occurrence of these phenomena in birds.

Rhythmic pineal melatonin biosynthesis develops in chick embryos incubated under a light (L)-dark (D) cycle of polychromatic white light. The spectral sensitivity of the embryonic pineal gland is not known and was investigated in this study. Broiler breeder eggs (Ross 308, n=450) were incubated under white, red, green or blue light under the 12L : 12D cycle. Melatonin was measured in extracts of pineal glands by radioimmunoassay. The daily rhythm of pineal melatonin levels in 20-day-old chick embryos was confirmed during the final stages of embryonic life under all four wavelengths of light with expected higher concentrations during dark- than light-times. The highest pineal melatonin levels were determined in chick embryos incubated under red and white light and lower levels under green light. The incubation under blue light resulted in the lowest melatonin biosynthesis. Pineal melatonin concentrations increased substantially on post-hatching day two compared with pre-hatching levels and we did not find differences between birds incubated and kept in either white or green light. Our results demonstrate a selective sensitivity of the chick embryo pineal gland to different wavelengths of light. Rhythmic melatonin production is suggested as a possible mechanism, which transfers information about the quality of ambient light to the developing avian embryo.

The eye is a vital sense organ under neuro endocrine regulation in order to allow sight in the bird. It responds to light stimulus and photoperiodicity of the environment of the birds, where they are reared. The effects of photo stimulation are mediated via the various components of the eye. The physiologic roles of avian eyes have been under-utilised in poultry management to enhance production and consequently, economic efficiency of the birds. Regulatory mechanisms of avian eyes’ function, response of components to photo stimulation and utilisation of photoperiod to enhance production in poultry have been reviewed. In conclusion, avian eyes respond to light stimulation and photoperiod, and these responses may be utilised for commercial poultry production in terms of eggs and meat, as well as for improving the welfare of the birds.

The restricted use of antibiotics in the poultry sector has greatly enhanced the search for environment-friendly alternatives and complementary therapeutic approaches to manage infectious diseases in poultry. Cytokines, as natural immune-modulators, offer alternatives to conventional chemical-based therapeutics. Cytokine usage is becoming more feasible in poultry due to recent advancements in the field of immunology and vaccination, leading to the identification and cloning of avian cytokine genes. Existing adjuvants for poultry vaccines can have deleterious side-effects on the health and products of poultry and a subsequent reduction in profits. Therefore, alternative adjuvants must be developed to enhance the impact of vaccination. The use of cloned cytokines as adjuvants in poultry is attracting attention after the identification of new cytokine genes in chicken. Hence, cytokines may be used as therapeutics and vaccine adjuvants for enhancing immune response during infection and vaccination. This review focuses on the recent advancements in the application of avian cytokines as therapeutics or vaccine adjuvants.

Chlamydia (C.) psittaci, formerly known as Chlamydophila psittaci infections cause important economical losses to the poultry industry and are a danger to public health. The economic and zoonotic impact of C. psittaci infections in the Western poultry industry is well documented. Less is known on its occurrence in Asia. In the following review we address C. psittaci infections in Chinese poultry in view of China supplying 40.8% of global egg production and 14.2, 69.3 and 91.1% of global chicken, duck and goose meat, respectively. The current paper compiles English and Chinese scientific literature on C. psittaci infections in Chinese poultry. The paper is focusing on seroprevalence, culture, direct antigen detection, molecular characterisation, observed symptoms, Chinese traditional medicine and psittacosis case reports. A review on the epidemiology of chlamydiosis in Chinese poultry clearly illustrates the widespread presence of virulent C. psittaci strains in chickens, ducks and geese across China. In Western countries, C. psittaci infections in poultry are principally treated with antibiotics. In China, however, herbal medicine is often used in conjunction with antibiotic treatment or as prophylaxis. The applied production and marketing systems facilitate zoonotic transfer. Chinese occupationally acquired psittacosis cases include reports on infections contracted from ducks, pigeons, chickens and peacocks.

There is a wide spectrum of techniques available to evaluate the functional aspects of the immune system in both humans and animals, including avian species. Some of the immunological techniques are qualitative and others are quantitative. In this paper, these techniques will be reviewed starting with a description of the nature of the antibody-antigen interaction, followed by the immune techniques that are used to detect immune complexes (i.e. antigen-antibody responses) whether free or associated with cells, then the numerous immune markers or parameters that are used to measure the avian immune responses.

Depending on the bird species, about 33-86% of the egg content consists of albumen. In eggs from domestic fowl, albumen contains about 10.5% protein and 88.5% of water and may be regarded as the main water source for the developing embryo. Besides carbohydrates, lipids, and inorganic ions, over 90% of the solids in the albumen are proteins. Several factors are known to influence the amount and composition of the albumen: egg weight, age and genetics of the parent flock, amount and quality of the feed provided, environmental factors (e.g. temperature, light), position in laying sequence, and also storage conditions of eggs prior to incubation. The albumen content of an egg plays an important role during embryonic development. Not only for formation of sub-embryonic fluid, but albumen proteins are known to flow into the amniotic cavity, the yolk sac and finally the digestive tract of the embryo and are used as the main source of proteins for tissue synthesis. Partial removal of albumen had negative consequences on chick weight at hatch, reduced the amount of amniotic and allantoic fluid and may reduce the water content of the chick and the residual yolk. Replacing the removed albumen with saline, however, reduced the residual yolk weight without differences in water content, suggesting increased uptake and utilisation of yolk, possibly as a compensation for the removed albumen proteins. In addition to reduced chick weight at hatch, some authors report an asymmetric growth restriction where nutrients are diverted away from non-vital organs in favour of brain and heart, with a relative ‘sparing’ of these latter two organs. Partial albumen removal led to a reduced whole-body protein synthesis, similar to eggs containing naturally less albumen. Importantly, several studies reported some long-term effects of albumen removal on growth, indicating that prenatal environment will have life-long consequences.

Avian diet selection is hypothesized to be sensitive to seasonal changes in breeding status, but few tests exist for frugivorous tropical birds. Frugivorous birds provide an interesting test case because fruits are relatively deficient in minerals critical for reproduction. Here, we quantify annual patterns of fruit availability and diet for two frugivorous hornbill (Bucerotidae) species over a 5.5-y period to test for patterns of diet selection. Data from the lowland tropical rain forest of the Dja Reserve, Cameroon, are used to generate two nutritional indices. One index estimates the nutrient concentration of the diet chosen by Ceratogymna atrata and Bycanistes albotibialis on a monthly basis using 3165 feeding observations combined with fruit pulp sample data. The second index is an estimate of nutrient concentration of a non-selective or neutral diet across the study area based on tree fruiting phenology, vegetation survey and fruit-pulp sample data. Fifty-nine fruit pulp samples representing 40 species were analysed for 16 nutrient categories to contribute to both indices. Pulp samples accounted for approximately 75% of the observed diets. The results support expected patterns of nutrient selection. The two hornbill species selected a diet rich in calcium during the early breeding season (significantly so for B. albotibialis in July and August). Through the brooding and fledging periods, they switched from a calcium-rich diet to one rich in iron and caloric content as well as supplemental protein in the form of invertebrates. Calcium, the calcium to phosphorus ratio and fat concentration were the strongest predictors of breeding success (significant for calcium and Ca:P for B. albotibialis in June). We conclude that hornbills actively select fruit based on nutritional concentration and mineral concentration and that the indices developed here are useful for assessing frugivore diet over time.

In 2008, avian bornaviruses (ABV) were identified as the cause of proventricular dilatation disease (PDD). PDD is a significant condition of captive parrots first identified in the late 1970s. ABV infection has subsequently been shown to be widespread in wild waterfowl across the United States and Canada where the virus infects 10–20% of some populations of ducks, geese and swans. In most cases birds appear to be healthy and unaffected by the presence of the virus; however, infection can also result in severe non-suppurative encephalitis and lesions similar to those seen in parrots with PDD. ABVs are genetically diverse with seven identified genotypes in parrots and one in canaries. A unique goose genotype (ABV-CG) predominates in waterfowl in Canada and the northern United States. ABV appears to be endemic in North American waterfowl, in comparison to what appears to be an emerging disease in parrots. It is not known whether ABV can spread between waterfowl and parrots. The discovery of ABV infection in North American waterfowl suggests that European waterfowl should be evaluated for the presence of ABV, and also as a possible reservoir species for Borna disease virus (BDV), a related neurotropic virus affecting horses and sheep in central Europe. Although investigations have suggested that BDV is likely derived from a wildlife reservoir, for which the shrew and water vole are currently prime candidates, we suggest that the existence of other mammalian and avian reservoirs should not be discounted.

Recent studies have suggested that avian semen contains a high proportion of polyunsaturated fatty acids (PUFAs) which are characterised by an increased susceptibility to lipid peroxidation. Free radicals are produced as a consequence of lipid peroxidation and these can impact on the fertility of male birds. The seminal plasma has been equipped with a defence mechanism called antioxidant capacity which protects semen integrity against the negative impact of ROS (reactive oxygen species). From the available literature, it can be surmised that lipid peroxidation is one of the major causes of low fertility in male birds which can be remedied with supplementation of exogenous vitamin E. Vitamin E provides biological stability to spermatozoal plasma membranes by inhibiting the generation of reactive oxygen species (ROS). Recent studies have suggested a role of vitamin E in improving semen quality and subsequent better fertility. In this review the current knowledge of physiology of ROS and antioxidative role of vitamin E to treat avian male fertility is discussed.

Avian spermatozoa are characterised by high proportions of polyunsaturated fatty acids (PUFAs) which is associated with increased susceptibility to reactive oxygen species (ROS) and lipid peroxidation. Recent advances in avian reproduction have focused on the potential of ROS as one of the prime mediators of infertility. Although ROS are involved in many physiological functions of spermatozoa, their excessive production may result in oxidative stress. The production of ROS is enhanced during unfavourable environmental and stressful conditions, and an effective scavenging system is essential to counter the production of ROS. Antioxidants are compounds that suppress the formation of ROS. Enzymatic and non-enzymatic antioxidants build a powerful antioxidant system in avian semen which is able to protect it against ROS and lipid peroxidation. The balance between ROS and antioxidants in avian semen is a fundamental determinant of membrane integrity, sperm viability and fertilising ability. A regulating role of ROS in sperm function in mammalian sperm along with their counteractive mechanisms have been extensively studied; but their role for avian species reproduction remains to be elucidated. Various antioxidants belonging both to enzymatic and non-enzymatic groups can counter oxidative stress. Hence the rationale of using antioxidants is advocated.

A honeydew-producing scale insect, Stigmacoccus garmilleri (Margarodidae), is associated with oak trees (Quercus spp.) in highland forests of Mexico. Although feeding by ants on scale-insect honeydew is more frequently documented in the literature, the honeydew produced by feeding instars of S. garmilleri is sufficient to provide nourishment for birds. This study elucidates bird use of honeydew in the tropical montane forests near Chiconquiaco, Veracruz, Mexico, and uncovers patterns in honeydew foraging. Over a 2-mo period, 40 trees harbouring scale insects, located in both forest and pasture areas, were intensely studied (160 h of bird-foraging observations along with quantitative measurements of honeydew production). Fifteen resident bird species and 18 migrant species were observed visiting observation trees. Approximately 72% of the resident bird species and 83% of the migrant bird species observed were recorded to forage on scale-insect honeydew. Audubon's warbler (Dendroica coronata auduboni) was the most active consumer and defender of the resource. Of 118 aggressive chases observed, only 9.65% occurred in forest observation trees, and 90.3% in pasture trees. Audubon's warbler demonstrated preferential defence and territorial patrolling of scale-insect honeydew in scattered pasture trees.

Electrical stimulation in pigeons of the input from the medial subdivision of the nucleus of Edinger-Westphal (EWM) to the choroidal neurons of the ipsilateral ciliary ganglion, which themselves have input to the choroidal blood vessels of the ipsilateral eye, increases choroidal blood flow (ChBF). Since the EWM receives input from the contralateral suprachiasmatic nucleus (SCN), which in turn receives contralateral retinal input, the present study sought to determine if activation of the SCN by microstimulation or by retinal illumination of the contralateral eye would also yield increases in ChBF in that same eye. Using laser Doppler flowmetry (LDF) to measure ChBF, we found that electrical activation of the contralateral SCN by 100-Hz anodal pulse trains yielded increases in ChBF that were stimulus related and proportional to the stimulating current. These increases in ChBF elicited by the SCN stimulation were accompanied by increases in choroidal volume (vasodilation), but not by increases in systemic blood pressure. Furthermore, the increases could be blocked reversibly by lidocaine injection into the EWM. These results suggest that the increases in ChBF in the eye contralateral to the SCN stimulation were specifically mediated by the SCN-EWM pathway. Retinal illumination with a fiber optic light source was also found to increase ChBF in the illuminated eye, and these effects too could be blocked reversibly with lidocaine injection into the EWM or permanently by the EWM lesion. Control studies confirmed that the light-elicited increases were mediated by increases in choroidal volume (i.e. vasodilation), were not accompanied by systemic blood pressure increases, and were not artifactually generated by transocular illumination of the LDF probe. Thus, the SCN-EWM circuit may be involved in regulating ChBF in response to the level of retinal illumination and/or the visual patterns falling on the retina.

The visual system of birds includes an efferent projection from a visual area, the isthmo-optic nucleus in the midbrain, back to the retina. Using a combination of anterograde labeling of efferent fibers, reconstruction of dye-filled neurons, NADPH-diaphorase staining, and transmission electron microscopy, we have examined the distribution of efferent fibers and their synaptic structures in the chicken retina. We show that efferent fibers terminate strictly within the ventral retina. In two completely mapped retinas, only 2 fibers from a total of 15,359 terminated in the dorsal retina. The major synapse made by each efferent fiber is with a single efferent target amacrine cell (TC). This synapse consists of 5–25 boutons of 2 μm diameter, each with multiple active zones, pressed into the TC soma or synapsing with a basketwork of rudimentary TC dendrites in the inner nuclear layer (INL). This basketwork, which is sheathed by Muller cell processes, defines a private neuropil in the INL within which TCs were also seen to receive input from retinal neurons. In addition to the major synapse, efferent fibers typically produce several very thin processes that terminate nearby in single small boutons and for which the soma of a local amacrine cell is one of the likely postsynaptic partners. A minority of efferent fibers also give rise to a thicker process, terminating in a strongly diaphorase-positive ball about 5 μm in diameter.

The retinas of birds receive a substantial efferent, or centrifugal, input from a midbrain nucleus. The function of this input is presently unclear, but previous work in the pigeon has shown that efferent input is excluded from the area centralis, suggesting that the functions of the area centralis and the efferent system are incompatible. Using an antibody specific to rods, we have identified the area centralis in another species, the chicken, and mapped the distribution of the unique amacrine cells that are the postsynaptic partners of efferent fibers. Efferent target amacrine cells are found within the chicken area centralis and their density is continuous across the border of the area centralis. In contrast to the pigeon retina then, we conclude that the chicken area centralis receives efferent input. We suggest that the difference between the two species is attributable to the presence of a fovea within the area centralis of the pigeon and its absence from that of the chicken.

Influenza A viruses that infect poultry can be divided into two groups. Very virulent viruses cause highly pathogenic avian influenza (HPAI), with flock mortality as high as 100%. These viruses have been restricted to subtypes H5 and H7, although not all H5 and H7 viruses cause HPAI. All other viruses cause a milder, primarily respiratory, disease (LPAI), unless exacerbated. Until recently, HPAI viruses were rarely isolated from wild birds, but for LPAI viruses extremely high isolation rates have been recorded in surveillance studies. Influenza viruses may infect all types of domestic or captive birds in all areas of the world. The frequency with which primary infections occur in any type of bird usually depends on the degree of contact there is with feral birds. Secondary spread is typically associated with human involvement, either by birds or bird product movement or by transferring infective faeces from infected to susceptible birds, but potentially wild birds can be involved. In recent years the frequency of HPAI outbreaks appears to have increased and there have been particularly costly outbreaks of HPAI in densely populated poultry areas in Italy, The Netherlands and Canada. In each outbreak millions of birds were slaughtered to bring the outbreaks under control. Since the 1990s, AI infections due to two subtypes have been widespread in poultry across a large area of the World. LPAI H9N2 appears to have spread across the whole of Asia in that time and has become endemic in poultry in many of the affected countries. However, these outbreaks have been overshadowed by the H5N1 HPAI virus, initially isolated in China that has now spread in poultry and/or wild birds throughout Asia and into Europe and Africa, resulting in the death or culling of hundreds of millions of poultry and posing a significant zoonosis threat. To date control methods seem to have been unsuccessful on the larger scale and HPAI H5N1 outbreaks continue to be reported.

Antimicrobial proteins are active against protozoans, fungi, viruses as well as gram-positive and gram-negative bacteria. In many cases, antimicrobial proteins are present as components of innate immunity and are capable of evading bacterial resistance mechanisms. Due to these characteristics, these proteins represent an appealing alternative to conventional antibiotic drugs. Considerable research has been conducted on antimicrobial proteins from invertebrate and mammalian sources. Within the last decade, over 20 novel antimicrobial proteins have been isolated from avian systems. The majority of these proteins has been isolated from the domestic chicken and therefore represents a minuscule fraction of the avian antimicrobial proteins that are potentially awaiting discovery. In this review, we elaborate on these discoveries and on the future of avian antimicrobial protein research.

It appears possible for free-flying native or feral wild birds to be responsible for direct or indirect spread of infectious agents from contaminated poultry product wastes to susceptible commercial poultry. Direct spread involves infected wild birds gaining access to commercial poultry. Indirect spread involves secondary spread to other free-flying birds that may subsequently gain access to commercial poultry.

In analysing the level of risk of such spread consideration is given to three elements. These are the susceptibility of wild birds to infection by the agents concerned, the opportunity for susceptible species coming into direct or indirect contact with both poultry product wastes and commercial poultry, and the occurrence of actual cases of such spread.

The scenario being considered is one in which poultry product wastes contain an infective dose of one of the agents of concern, namely avian influenza, Newcastle disease or infectious bursal disease. A review of the literature was undertaken to assist in assessing the likelihood of spread of these agents by wild birds.

Exposure of wild birds, to any of the three viruses of concern at product waste disposal sites, is a potential threat but the likelihood of spread to commercial poultry appears to be low. More obvious means of spread occur in the poultry industry, as biosecurity is often rudimentary. Spread of infectious agent by fomites, live poultry and infected wild birds could well be involved in transmission of disease agents between farms. Where live bird poultry markets or semi-feral village poultry exist they provide an obvious means of spread of these agents and involvement of access of wild birds to poultry product wastes is probably of little importance.

The likelihood of wild bird involvement in virus spread from poultry products could increase if a susceptible species with gregarious habits (flocking behaviour) leading to high population densities, were to frequent both poultry product waste disposal sites and commercial poultry premises. Some passerines are likely to frequent waste disposal facilities and poultry premises, but it appears that different species congregate at poultry premises than at waste disposal sites.

There is little evidence of spread of disease from waste poultry products to commercial poultry premises having occurred.

The skin of the emu Dromaius novaehollandiae is described in its entirety by light microscopy for the first time, therefore providing a basis for comparison with the integument of volant birds. The epidermal and dermal layers have a similar arrangement to other avian species. The concentration of lipid spheres in the basal layer of the epidermis is unique to emus. Although no differences in collagen density with depth of the dermis were observed, collagen bundle diameter is significantly smaller in the stratum superficiale compared to the stratum compactum (P=0.001). The extensive stratum laxum, comprised predominantly of adipose tissue, may be an evolutionary adaptation to support the large feathers and also enhance insulation against ambient subzero temperatures. Males have a significantly thicker cellular epidermis (P=0.024) and stratum compactum (P=0.04) than females. In contrast, females have denser collagen (P=0.04) within the stratum superficiale and stratum compactum.