Commercial poultry are the most numerous type of domestic animal. This section discusses the large variety of infectious diseases, metabolic disorders, and management issues affecting this group of species.
Poultry Sections (A-Z)
Air Sac Mite
Cytodites nudus is a small cosmopolitan mite occasionally noticed as white spots on the bronchi, lungs, air sacs, and abdominal organs of chickens, turkeys, pheasants, pigeons, canaries, and mallards. (Also see Air Sac Mites.) These mites are readily transmissible between birds through coughing. They are rarely found in commercial industries. The 14- to 21-day life cycle involves a larval and two nymphal stages. Infestation densities vary, and clinical signs range from none to weakness, weight loss, pneumonia, peritonitis, pulmonary edema, and death. Recommended treatments include ivermectin, a nearby dichlorvos pest strip (placed out of reach of the birds), topical moxidectin, or a pyrethrin/piperonyl butoxide spray.
Artificial insemination (AI) is widely used to overcome low fertility in commercial turkeys, which results from unsuccessful mating as a consequence of large, heavily muscled birds being unable to physically complete the mating process. This is a serious and costly problem in the production of commercial turkey hatching eggs. In most commercial chicken production systems in the USA, it has not been necessary to implement AI programs because natural mating results in adequate fertility levels, but AI is routinely used in special breeding work and research. However, as managing commercial broiler breeders to maximize fertility becomes more challenging, the use of AI in commercial poultry operations outside the USA is becoming more common. Certainly, the use of AI in chickens, as in turkeys, can improve fertility; however, the cost of implementing AI on a large scale is often cost prohibitive.
Aspergillosis is a disease, usually of the respiratory system, of chickens, turkeys, and less frequently ducklings, pigeons, canaries, geese, and many other wild and pet birds. In chickens and turkeys, the disease may be endemic on some farms; in wild birds, it appears to be sporadic, frequently affecting only an individual bird. Severe outbreaks usually occur in birds 7–40 days old. (Also see Aspergillosis and see Aspergillosis.)
Avian Campylobacter Infection
Campylobacteriosis is a significant enterocolitis of people frequently acquired through consumption of undercooked poultry meat contaminated with Campylobacter jejuni. It is the leading bacterial cause of sporadic enteritis in developed countries. It can also be acquired from handling backyard poultry as well as diarrheic companion animals and from contaminated water. The organism colonizes the intestine of chickens, turkeys, and waterfowl but is generally nonpathogenic in birds. Some strains of C jejuni have been reported to cause enteritis and death in newly hatched chicks and poults; however, it has not been possible to satisfy Koch’s postulates and reproduce the syndrome previously termed “avian vibrionic hepatitis” by administering isolates of C jejuni to chickens.
Avian chlamydiosis can be an inapparent subclinical infection or acute, subacute, or chronic disease of wild and domestic birds characterized by respiratory, digestive, or systemic infection. Infections occur worldwide and have been identified in at least 460 avian species, particularly caged birds (primarily psittacines), colonial nesting birds (eg, egrets, herons), ratites, raptors, and poultry. Among poultry, turkeys, ducks, and pigeons are most often affected. The disease is a significant cause of economic loss and human exposure in many parts of the world.
Avian encephalomyelitis (AE) is a viral disease of young chickens, turkeys, Japanese quail, pheasants, and pigeons. Turkeys are less susceptible to natural infection and generally develop a milder clinical disease than chickens. Ducklings and guinea fowl are susceptible to experimental infection. AE is characterized by neurologic signs that result from infection of the CNS with an RNA virus in the family Picornaviridae. Infection occurs via vertical and horizontal transmission. If a breeder flock becomes infected during egg production, the virus is vertically transmitted to the offspring and a major outbreak occurs. The disease often appears in a series of flocks hatched from the infected breeder flock. Field strains of the virus are enterotropic and multiply in the intestine. Infected birds shed the virus in their feces for a few days to a few weeks, which serves to spread the infection to hatchmates. There is no convincing evidence that the virus persists in infected birds. AE virus is resistant to environmental conditions and may remain infectious for long periods.
Avian influenza (AI) viruses infect domestic poultry as well as pet, zoo, and wild birds. In domestic poultry, AI viruses are typically of low pathogenicity (LP), causing subclinical infections, respiratory disease, or drops in egg production. However, a few AI viruses cause severe systemic infections with high mortality. This highly pathogenic (HP) form of the disease has historically been called fowl plague. In most wild birds, AI viral infections are subclinical except for the recent H5N1 HP AI viruses of Eurasian lineage.
Avian metapneumovirus (aMPV) causes turkey rhinotracheitis, an acute respiratory tract infection of turkeys. It is also associated with swollen head syndrome in broilers and broiler breeders, as well as egg production losses in layers. The virus was first detected in turkeys in South Africa in the late 1970s and has spread to all the major poultry-producing areas in the world except for Australia. aMPV has been detected not only in chickens and turkeys but also in pheasants, Muscovy ducks, and guinea fowl. Geese, most other duck species, and possibly pigeons are suggested to be refractory to disease. Epidemiologic studies provide evidence for the circulation of aMPV in wild birds, especially water-associated species. Some outbreaks have been attributed to vaccine-derived viruses, which may persist for several months in the environment. Infection with aMPV is often complicated by secondary bacterial infections, leading to high economic losses. In 2001 the first human metapneumovirus (hMPV) was isolated and classified as a member of the genus Metapneumovirus, which causes respiratory infections in people. Experimental studies suggest that turkeys also may be susceptible to hMPV. Complete genome sequencing confirmed that the genomic organization of hMPV is similar to that of aMPV. Overall, little is known about the cross-species pathogenicity of these two viruses.
Avian Nephritis Viral Infections
Avian nephritis viral infections are contagious infections of chickens characterized by renal damage and visceral urate deposits, growth retardation, and limited mortality (0–10%). They are seen mainly in chickens <7 days old, but interstitial nephritis can be seen in chicks as old as 4 wk. These infections have been reported worldwide. Subclinical infections are common and have been detected by serologic surveys in some SPF flocks and in turkeys.
Avian blood may contain various disease agents, including viruses, bacteria, rickettsiae, protozoa, microfilariae, and rarely fungi. These organisms can be identified by microscopic examination of wet mounts, buffy coat, or blood smears or by appropriate culturing and molecular techniques. Microscopically, some are within blood cells (Plasmodium, Haemoproteus, Leucocytozoon, Isospora[Atoxoplasma], Hepatozoon, Babesia, Aegyptianella), while others are free in the plasma (Trypanosoma, microfilariae, bacteria, spirochetes). None live exclusively in the blood; most are found in tissues but are present in blood during part of their life cycle. Some, such as microfilariae and Plasmodium, may have a periodicity when numbers or stages of parasites vary with time. In such cases, examining multiple smears at intervals will increase the likelihood of obtaining a diagnosis. Seasonal variations in infection rates relate to the activity of arthropod vectors. When possible, tissue cytology is also a useful adjunct to examination of blood. Most bloodborne organisms are either uncommonly or not associated with clinical disease. However, weakened or injured birds infected with hemoprotozoa may have higher mortality and slower recovery than uninfected birds. Examination for bloodborne organisms should be included in the clinical and diagnostic procedures for any ill bird.
Avian bordetellosis is a highly infectious, acute upper respiratory tract disease of turkeys characterized by high morbidity and usually low mortality. Other synonyms previously used for the disease include Alcaligenes rhinotracheitis, adenovirus-associated respiratory disease, acute respiratory disease syndrome, and turkey rhinotracheitis.
Botulism is an intoxication that results from ingestion of preformed exotoxin of Clostridium botulinum. The disease occurs worldwide and has been identified in at least 117 species of wild birds representing 22 families. There is concern that endangered avian species may be at risk of extinction because of the disease. Mammalian species affected by the toxin include people, mink, ferrets, cattle, pigs, dogs, horses, laboratory rodents, and various zoo animals. Intoxications are sporadic in poultry, but massive mortality has occurred in waterfowl. Ruminants fed poultry manure contaminated with C botulinum spores have developed the disease.
Candidiasis is a mycotic disease of the digestive tract of various avian species, including chickens, turkeys, and quail caused by Candida albicans. It commonly develops after use of therapeutic levels of various antibiotics or when using unsanitary drinking facilities. Lesions are most frequently found in the crop and consist of thickened mucosa and whitish, raised pseudomembranes. The same lesions may be seen in the mouth and esophagus. Occasionally, shallow ulcers and sloughing of necrotic epithelium may be present. Listlessness and inappetence may be the only signs. A presumptive diagnosis may be made on observation of gross lesions. Diagnosis can be confirmed by demonstrating tissue invasion histologically and by culture of the organism. However, culture alone is not diagnostic of disease, because the yeast-like fungus is commonly isolated from clinically normal birds. Young chicks and poults are most susceptible.
Chicken Anemia Virus Infection
Coccidiosis is caused by protozoa of the phylum Apicomplexa, family Eimeriidae. In poultry, most species belong to the genus Eimeria and infect various sites in the intestine. The infectious process is rapid (4–7 days) and is characterized by parasite replication in host cells with extensive damage to the intestinal mucosa. Poultry coccidia are generally host-specific, and the different species parasitize specific parts of the intestine. However, in game birds, including quail, the coccidia may parasitize the entire intestinal tract. Coccidia are distributed worldwide in poultry, game birds reared in captivity, and wild birds. (Also see Cryptosporidiosis.)
Coronaviral Enteritis of Turkeys
Coronaviral enteritis is an acute, highly contagious disease of turkeys characterized by depression, anorexia, diarrhea, and decreased weight gain. Mortality may be high, particularly in young poults, but failure to gain body weight in adult birds may be more important economically. The causative agent is turkey coronavirus (TCV), but clinical disease usually is complicated by other enteric viral, bacterial, and protozoal infections.
Cryptosporidiosis is caused by protozoa (phylum Apicomplexa) that are members of the family Cryptosporidiidae and are related, but distinct, to coccidia of the genera Eimeria, Isospora, Sarcocystis, and Toxoplasma. Until recently, it was thought that there were 19 species in the genus Cryptosporidium, but research has shown that most are merely species that lack host specificity. Cryptosporidia are parasitic in the intestine of mammals (see Cryptosporidiosis), but in birds they are commonly found in the bursa and in the respiratory tract. Cryptosporidiosis is more severe in turkeys than in chickens and is frequently fatal in quail.
Disorders of the Reproductive System
Fluid accumulation in the vestigial right oviduct is a common finding in hens. The abdominal cyst is filled with clear fluid and is attached to the right side of the cloacal wall. The cyst may vary in size from barely perceptible to 15–20 cm in diameter. An increased incidence has been seen in flocks after infectious bronchitis virus outbreaks. Oviductal cysts are a necropsy finding that rarely, if ever, affect flock performance.
Disorders of the Skeletal System
Production characteristics of modern poultry lines (eg, body weight in broiler chickens, egg production in laying hens) place high demands on the skeletal system, and inadequacies in nutrition or husbandry often result in skeletal diseases. Skeletal disorders may be primarily infectious or noninfectious; both may be seen concurrently within a flock. Skeletal disorders cause lameness from biomechanical dysfunction and in broiler chickens result in poor growth, culled birds, increased mortality (caused by starvation and dehydration), and carcass condemnation and downgrading. Bone fractures in spent hens may be a welfare issue. Before postmortem examination, flocks should be assessed; live, lame birds should be examined, and general flock health and management assessed. Serum samples may be collected for viral and mycoplasmal serology and/or biochemistry (eg, serum calcium). Gross pathology alone is often insufficient, and histopathology is usually necessary to reach a diagnosis. Bone ash measurement, feed nutritional analysis, and bacteriology are useful complementary investigations.
Dissecting Aneurysm in Turkeys
Dissecting aneurysm is a fatal disease of turkeys. It is characterized by sudden death of rapidly growing birds with massive internal hemorrhage. The hemorrhage results from rupture of aneurysms formed in various parts of the vascular system. The frequency with which the posterior aorta is affected has given rise to the term “aortic rupture.” The disease has been reported in North America, Europe, and Israel. Most breeds of turkeys are susceptible, and the largest and most rapidly growing males, 8–24 wk old, are affected most often; females are also affected but at a lower incidence.
Duck Viral Enteritis
Duck viral enteritis (DVE) is an acute, highly contagious disease of ducks, geese, and swans of all ages, characterized by sudden death, high mortality (particularly among older ducks), and hemorrhages and necrosis in internal organs. It has been reported in domestic and wild waterfowl in Europe, Asia, North America, and Africa, resulting in limited to serious economic losses on domestic duck farms and sporadic, limited to massive die-offs in wild waterfowl. In the USA, considerable losses due to DVE have been reported in the concentrated duck-producing areas located in Long Island, New York.
Duck Viral Hepatitis
Duck viral hepatitis is an acute, highly contagious, viral disease of young ducklings characterized by a short incubation period, sudden onset, high mortality, and characteristic liver lesions. The disease is of economic importance in all duck-raising areas of the world. Three distinct types of duck hepatitis virus (DHV) have been isolated from diseased ducklings. A natural outbreak of DHV Type I has been reported in mallard ducklings; experimental DHV Type I infections have been produced in goslings, turkey poults, young pheasants, quail, and guinea fowl. In Muscovy ducks, DHV Type 1 has been reported to cause pancreatitis and encephalitis. The viruses that cause hepatitis in ducklings should not be confused with duck hepatitis B virus, a hepadnavirus infection of older ducks.
Cimex lectularius is a common bloodsucking parasite in temperate and subtropical climates that attacks poultry, people, and most other mammals. It is rare in modern laying operations, but breeding houses and pigeon lofts may become heavily infested. The life cycle may be completed in 2–6 wk or extend much longer, because nymphs can withstand fasting for ~70 days, and adults for as long as 12 mo. Feeding usually occurs at night. Bedbugs become engorged within 10 min, then hide in cracks and crevices. If attacked by large numbers of bedbugs, birds may become irritable and anemic. Bites are usually followed by swelling and itching due to injection of saliva into the wound. Signs of infestation include bug fecal droppings on eggs and nest boxes, breast and leg skin lesions, reduced egg production, and increased feed consumption.
Egg Drop Syndrome '76
Egg drop syndrome ’76 (EDS ‘76) is an atadenovirus-induced disease characterized by the production of pale, soft-shelled, and shell-less eggs by apparently healthy laying hens. The disease in laying hens has commonly been called "egg drop syndrome," but the full name (egg drop syndrome ’76 [EDS ’76]) should be used to distinguish it from the recently recognized flaviviral disease of ducks, which has been called "egg drop syndrome in ducks," and "duck egg drop syndrome," creating potential for confusion.
Enterococcosis has been reported in a variety of avian species worldwide. Enterococcus spp are normal microflora found in the intestinal tract of poultry and other bird species; infections are usually secondary to another disease. Enterococcus infections can result in either an acute or subacute/chronic form.
Erysipelas is a bacterial disease caused by infection with Erysipelothrix rhusiopathiae. The disease is most often seen as septicemia, but urticarial and endocardial forms exist. E rhusiopathiae infects a wide range of both avian and mammalian hosts. The disease has been reported in domestic fowl, feral avian species, and captive wild birds and mammals. Infection in reptiles and amphibians has been reported. The organism has also been isolated from the surface slime on fish (without causing disease), which may serve as a source of infection for other species. From an economic standpoint, turkeys are the most important poultry species affected, but serious outbreaks have occurred in chickens, ducks, and geese. Among affected mammals, swine are the most economically important species, but E rhusiopathiae infection is also a cause of polyarthritis in lambs. (Also see Erysipelothrix rhusiopathiae Infection.)
Fatty Liver Hemorrhagic Syndrome
Fatty liver hemorrhagic syndrome (FLHS) was first described in the 1950s as excessive fat in the liver of prolific laying hens, associated with varying degrees of hemorrhage. The condition is almost universally confined to caged birds fed high-energy diets and is most often seen in white-egg layers in warm, summer months. The liver is usually enlarged, putty colored, and very friable, showing varying degrees of hemorrhage. The abdominal cavity often contains large amounts of oily, unsaturated fat. Affected birds often have pale combs, likely as a consequence of reduced egg production. The ovary is usually active, at least in the early stages of FLHS, and the metabolic and physical stress associated with oviposition may be factors that induce the final fatal hemorrhage.
Fowlpox is a slow-spreading viral infection of chickens and turkeys characterized by proliferative lesions in the skin that progress to thick scabs (cutaneous form) and by lesions in the upper GI and respiratory tracts (diphtheritic form). Virulent strains may cause lesions in the internal organs (systemic form). Fowlpox is seen worldwide.
Gangrenous dermatitis is a disease of turkeys and chickens caused by Clostridium septicum, C perfringens type A, and Staphylococcus aureus, either singly or in combination. The condition is characterized by rapid onset of acute mortality. Birds succumbing to the infection have necrosis of the skin and subcutaneous tissue, usually involving the breast, abdomen, wing, or thigh.
Goose Parvovirus Infection
Goose parvovirus infection is a highly contagious and fatal disease of goslings and Muscovy ducklings, often causing as much as 70%−100% mortality in goslings <4 wk old. Goose parvovirus has been reported from all the major goose-farming countries of Europe and the Far East, where the disease is of serious economic significance. Muscovy ducks and several hybrid duck breeds are also susceptible to another parvovirus that has been shown to be antigenically related to goose parvovirus. This so-called Muscovy duck parvovirus has been isolated from an outbreak among Muscovy ducks in California. Goose parvovirus has not been detected in the USA.
Approximately 100 worm species have been recognized in wild and domestic birds in the USA. Nematodes (roundworms) are the most significant in number of species and in economic impact. Of species found in commercial poultry, the common roundworm (Ascaridia galli) is by far the most common. Field studies show that poultry maintained under free-range conditions may be heavily parasitized; therefore, control measures such as preventing infections or chemotherapy are likely to improve weight gain and egg production. In surveys of poultry raised under nonconfinement conditions throughout the world, an incidence of infection >80% is not uncommon.
Hemorrhagic Enteritis/Marble Spleen Disease
Hemorrhagic enteritis is an acute GI disorder affecting young turkeys ≥4 wk old. In its most severe form, it is characterized by depression and hemorrhagic droppings. Mortality may be increased; however, this is rare because of extensive use of vaccines. Marble spleen disease is an acute respiratory disease of pheasants characterized by depression, enlarged mottled spleens, pulmonary congestion, and death. Both diseases are caused by similar viruses. Species-specific differences in clinical response are thought to be related to differences in the target organs for anaphylaxis and variation in viral pathotype. Infection with less virulent pathotypes in either host often may go undetected until secondary bacterial infections begin to develop as a result of viral-induced immunosuppression.
Hexamitiasis is an acute, infectious, catarrhal enteritis of turkeys, pheasants, quail, chukar partridges, and peafowl. The highest mortality occurs in birds 1–9 wk old. Natural infection has not been observed in chickens. Pigeons are susceptible to another species of Spironucleus (S columbae). Hexamitiasis is rare in North America.
Inclusion Body Hepatitis/Hydropericardium Syndrome
Adenoviruses are widespread throughout all avian species. Studies have demonstrated the presence of antibodies in healthy poultry, and viruses have been isolated from normal birds. Despite their widespread distribution, most adenoviruses cause no or only mild disease; however, some are associated with specific clinical conditions. Avian adenoviruses (AAVs) in chickens are the etiologic agents of two important diseases known as inclusion body hepatitis (IBH) and hydropericardium syndrome (HP). Although in some cases each disease is observed separately, the two conditions have been frequently observed as a single entity; therefore, the name hepatitis hydropericardium has been widely used to describe the pathologic condition. The syndrome is an acute disease of young chickens associated with anemia, hemorrhagic disorders, and hydropericardium. It is a common disease in several countries, where broilers are severely affected, resulting in high mortality rates.
Infectious bronchitis is an acute, highly contagious disease of major economic importance in commercial chicken flocks throughout the world. It is usually characterized by respiratory signs, although decreased egg production and poor egg quality are sometimes seen in breeders and layers. Some strains of the etiologic agent, infectious bronchitis virus (IBV), are nephropathogenic, causing interstitial nephritis, particularly in chicks. Associations with myopathy and proventriculitis have also been reported.
Infectious Bursal Disease
Infectious bursal disease (IBD) is seen in domestic chickens worldwide. It can present as a clinical or subclinical disease, but immunosuppression and related secondary infections are typically seen. Severity of the immunosuppression depends on the virulence of the infecting virus and age of the host.
Infectious coryza is an acute respiratory disease of chickens characterized by nasal discharge, sneezing, and swelling of the face under the eyes. It is found worldwide. The disease is seen only in chickens; reports of the disease in quail and pheasants probably describe a similar disease that is caused by a different etiologic agent.
Infectious laryngotracheitis (ILT) is an acute, highly contagious, herpesvirus infection of chickens and pheasants characterized by severe dyspnea, coughing, and rales. It can also be a subacute disease with nasal and ocular discharge, tracheitis, conjunctivitis, and mild rales. The disease is caused by Gallid herpesvirus I, commonly known as infectious laryngotracheitis virus (ILTV). It has been reported from most areas of the USA in which poultry are intensively reared, as well as from many other countries.
Listeriosis is caused by the bacterium Listeria monocytogenes. Although many species of birds, including chickens, turkeys, pigeons, ducks, geese, canaries, and cockatiels, are susceptible to infection, clinical disease in birds is rare. Generally, young birds are more susceptible to infection and more likely to develop clinical disease than older birds. In chickens, the disease occurs sporadically as either septicemia or encephalitis.
Malabsorption syndrome is a transmissible disease characterized by stunted growth and a lack of skin pigmentation in growing chickens, most commonly broiler breeds. Turkeys may also be affected; in these birds, it resembles poult enteritis mortality syndrome. The disease has been identified in virtually all countries in which intensive poultry production occurs. It has been associated with several different enteric viruses and appears to be multifactorial, although the true etiology remains to be identified. Poor management may contribute to the problem.
Miscellaneous Conditions of Poultry
Ascites is an accumulation of noninflammatory transudate in one or more of the peritoneal cavities or potential spaces. The fluid, which accumulates most frequently in the two ventral hepatic, peritoneal, or pericardial spaces, may contain yellow protein clots. Ascites may result from increased vascular hydraulic pressure, vascular damage, increased tissue oncotic pressure, or decreased vascular oncotic (usually colloidal) pressure, but is most commonly associated with venous hypertension resulting from right heart failure in response to increased pulmonary resistance.
Mycoplasmas are bacteria that lack a cell wall and are the smallest prokaryotes (0.2–0.8 μm in diameter). They have complex nutritional requirements but will grow on specialized artificial medium containing serum. Growth in broth and on agar media is slow (5–21 days), and the small (0.1–1 mm diameter) colony morphology typically has a "fried egg" appearance under low magnification. Mycoplasmas do not survive for more than a few days outside the host and are vulnerable to common disinfectants.
A mycotoxicosis is a disease caused by a natural toxin produced by a fungus. In poultry, this usually results when toxin-producing fungi grow in grain and feed. Hundreds of mycotoxins have been identified, and many are pathogenic. Mycotoxins may have additive or synergistic effects with other natural toxins, infectious agents, and nutritional deficiencies. Many are chemically stable and maintain toxicity over time. (Also see Mycotoxicoses.)
Exertional myopathy results from overly strenuous muscular exercise and can be precipitated by preexisting conditions such as selenium deficiency. Inadequate energy metabolism and/or mechanical stresses occurring during contraction are thought to be the cause of myofiber degeneration. The lesions can be monophasic (resulting from a single event, eg, transport, capture, or restraint myopathy) or polyphasic (with repeated or ongoing events). Early gross lesions include muscle pallor with edema or bloodstained transudate. There is swelling, degeneration, necrosis, and mineralization of muscle fibers, with edema, hemorrhage, and infiltration of heterophils and macrophages. Deep pectoral myopathy and capture myopathy are the main examples of exertional myopathy in birds. Leg muscle myopathy after transport of poultry can also occur and is associated with increased body size and weight, increased transport time to processing plant, cool ambient temperatures, and valgus leg deformities.
Necrotic enteritis is an acute enterotoxemia. The clinical illness is usually very short, and often the only signs are a severe depression followed quickly by a sudden increase in flock mortality. The disease primarily affects broiler chickens (2–5 wk old) and turkeys (7–12 wk old) raised on litter but can also affect commercial layer pullets raised in cages. Early mortality is often related to coccidiosis vaccination programs, with Eimeria cycling in these flocks.
Depending on whether the etiologic agent is known, neoplasms of poultry are divided into two main categories: virus-induced neoplasms and neoplasms of unknown etiology. There are three economically important virus-induced neoplastic diseases of poultry: Marek’s disease, caused by a herpesvirus, and avian leukosis/sarcoma and reticuloendotheliosis, caused by retroviruses. While these neoplastic diseases cause economic losses from tumor mortality and poor performance, some of them have served as highly suitable models to study neoplasia.
Newcastle Disease and Other Paramyxovirus Infections
Newcastle disease is an infection of domestic poultry and other bird species with virulent Newcastle disease virus (NDV). It is a worldwide problem that presents primarily as an acute respiratory disease, but depression, nervous manifestations, or diarrhea may be the predominant clinical form. Severity depends on the virulence of the infecting virus and host susceptibility. Occurrence of the disease is reportable and may result in trade restrictions.
Nutrition and Management: Poultry
Poultry convert feed into food products quickly, efficiently, and with relatively low environmental impact compared with other livestock. The high rate of productivity of poultry results in relatively high nutrient needs. Poultry require the presence of at least 38 dietary nutrients in appropriate concentrations and balance. The nutrient requirement figures published in Nutrient Requirements of Poultry (National Research Council, 1994) are the most recent available and should be viewed as minimal nutrient needs for poultry. They are derived from experimentally determined levels after an extensive review of the published data. Criteria used to determine the requirement for a given nutrient include growth, feed efficiency, egg production, prevention of deficiency symptoms, and quality of poultry product. These requirements assume the nutrients are in a highly bioavailable form, and they do not include a margin of safety. Consequently, adjustments should be made based on bioavailability of nutrients in various feedstuffs. A margin of safety should be added based on the length of time the diet will be stored before feeding, changes in rates of feed intake due to environmental temperature or dietary energy content, genetic strain, husbandry conditions (especially the level of sanitation), and the presence of stressors (such as diseases or mycotoxins).
Omphalitis is a condition characterized by infected yolk sacs, often accompanied by unhealed navels in young fowl. It is infectious but noncontagious and is associated with poor regulation of incubation temperature or humidity and marked contamination of the hatching eggs or incubator. If young poultry are placed in contaminated transportation boxes before their navels are completely closed, bacteria can migrate up the patent yolk stalk and infect the yolk sac.
Perirenal Hemorrhage Syndrome of Turkeys
Perirenal hemorrhage syndrome (PHS) is a noninfectious cardiovascular disorder usually affecting rapidly growing male turkeys 8–15 wk old. It is characterized by sudden death, perirenal hemorrhage, and hypertrophic cardiomyopathy. Mortality is usually 0.5%–2% but can be higher; there is no morbidity. Healthy, rapidly growing flocks are more likely to be affected.
Also see Toxicology Introduction et seq.
Quail bronchitis is a naturally occurring, highly contagious, often fatal respiratory disease of bobwhite quail, seen both in the wild and in captivity. The disease is of major economic significance to gamebird breeders and has a worldwide distribution. It is a serious disease on certain farms where quail are pen-raised, and particularly when quail of different ages are maintained on the same premises.
Riemerella anatipestifer Infection
Rotaviral Infections in Chickens, Turkeys, and Pheasants
Salmonella infections are classified as nonmotile serotypes (S Pullorum, S Gallinarum) and the many motile paratyphoid Salmonella. These Salmonella infections have a worldwide distribution. As a result of the institution of a testing and control program in the USA through the USDA-administered National Poultry Improvement Plan, the incidence of S Pullorum or S Gallinarum has decreased dramatically. Historically, S Arizonae was placed in its own category, but it is now included with the paratyphoid Salmonella. S Arizonae is an egg-transmiited disease primarily of young turkeys. In addition to the above nonmotile salmonellae, Salmonella paratyphoid infections in poultry are relatively common and have public health significance because of contaminated poultry product consumption.
Spontaneous Cardiomyopathy of Turkeys
Staphylococcosis is a bacterial disease that can affect a wide range of avian species, including poultry, and is seen worldwide. Staphylococcus aureus is most commonly isolated from staphylococcosis cases, but species such as S hyicus have also been reported as the causative agent of osteomyelitis in turkey poults. The disease conditions associated with staphylococcosis vary with the site and route of inoculation and can involve the bones, joints, tendon sheaths, skin, sternal bursa, navel, and yolk sac. Economic losses may result from decreased weight gain, decreased egg production, lameness, mortality, and condemnation at slaughter.
Streptococcosis has been reported in numerous bird species throughout the world. There are two forms of the disease, an acute septicemic form and a chronic form. Flock mortality can be as high as 50%. Because streptococci are part of the normal flora of the intestinal mucosa of most avian species, infections are often thought to occur secondarily to other diseases.
Sudden Death Syndrome of Broiler Chickens
A syndrome of sudden death has been reported in most areas of the world that raise broilers intensively. Young, healthy, fast-growing broiler chickens die suddenly with a short, terminal, wing-beating convulsion. Many affected broilers just “flip over” and die on their backs; 60%–80% are males. The condition is uncommon or unrecognized when low-density feed is used.
Tuberculosis is a slowly spreading, chronic, granulomatous bacterial infection characterized by gradual weight loss. All birds appear to be susceptible, although to variable degrees; pheasants seem to be highly susceptible, whereas the disease is uncommon in turkeys. Tuberculosis is more prevalent in captive than in free-living wild birds. It is unlikely to be seen in commercial poultry because of the short life span and husbandry practices used. (Also see Tuberculosis and other Mycobacterial Infections.)
Turkey Viral Hepatitis
Turkey viral hepatitis is an acute, highly contagious, frequently subclinical disease of turkey poults 5 wk of age. The disease is widespread and common in some areas, with morbidity rates of as much as 100%. Mortality has been reported only in poults, is confined to a 4- to 8-day period, and may reach 25%.
Ulcerative enteritis was first diagnosed in bobwhite quail (Colinus virginianus). It also affects chickens, turkeys, pheasants, grouse, and other gallinaceous birds. The disease has also been reported in pigeons and psittacine birds. In Japanese quail (Coturnix coturnix japonica), only experimentally induced cases have been reported in highly inbred populations. An ulcerative enteritis–like disease is caused by Clostridium perfringens in Coturnix quail. Ulcerative enteritis occurs worldwide and may be acute or chronic.
Reovirus infections are ubiquitous in commercial poultry flocks. They are global in distribution, although the virulence of viruses appears to differ between regions. Most strains are nonpathogenic and appear to survive harmlessly in the intestine, whereas others have been associated with several disease conditions, including malabsorption and other enteric disorders, hydropericardium, and occasionally respiratory disease. In many instances, the association of the reovirus with disease is uncertain. An exception to this is viral arthritis, or tenosynovitis, because it can be reproduced experimentally by infecting birds with reovirus alone.
Encephalitis in poultry and farm-reared gamebirds may be caused by several different arboviruses. These include Eastern equine encephalitis (EEE) virus, Western equine encephalitis (WEE) virus, Highlands J (HJ) virus, Israel turkey meningoencephalitis virus, and West Nile Virus (See also West Nile Virus Infection in Poultry). The term “arbovirus,” an abbreviation of arthropod-borne virus, is used to describe a virus that replicates in a hematophagous (bloodsucking) arthropod and is transmitted by bite to a vertebrate host.
West Nile Virus Infection in Poultry
Also see Equine Arboviral Encephalomyelitis.