Respiratory Diseases Viral : Infectious Bronchitis (IB) Newcastle Disease/Ranikhet Disease Pox Adeno virus

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1 Respiratory Disease Complex in Poultry: Diagnosis and Management Dr. V. Gowthaman and Dr. T.R. Gopala Krishna Murthy Poultry Disease Diagnosis and Surveillance Laboratory Veterinary College and Research Institute Campus Namakkal Tamil Nadu Introduction The world poultry industry has established itself as a flourishing enterprise, which is indicated by its positive growth rate in both table eggs and poultry meat production. This is further substantiated by the fact that chicken meat represents approximately 40% of all meat consumed by humans world wide. During the past two decades total world egg production has doubled and poultry meat consumption has tripled. Poultry rearing in India has taken a quantum jump during the last four decades emerging from a near back-yard practice to a full-fledged Industry. The total India poultry population was nearly million, growing phenomenally at nearly 8-15% every year. With a production of nearly billion eggs and 2.70 million metric tons of meat, India ranks third in world egg production and fourth in poultry meat production. The incredible achievement has been brought about by the adoption of improved breeding methods, nutrition, management and sophisticated health coverage programmes. Despite these, due to selective breeding policy for higher production, intensive rearing and too many vaccinations the birds are facing all sorts of stress beyond the limit of their physiological tolerance making them more vulnerable to diseases. A complex can by defined as a condition with which several known and unknown factors operates sequentially and successfully to precipitate the pathogens (virus, bacteria, or parasite) viably in the vicinity to cause greater havoc in the flock at any age of the bird s life. Among these respiratory disease complex in poultry is of significant economic importance. Etiology of respiratory disease-complex in poultry Among the prevailing diseases, respiratory diseases are frequently reported throughout the world causing economic loss to the poultry farmers in terms of mortality and loss of production. Respiratory diseases of poultry constitute an important cause of economic loss to the poultry industry worldwide in terms of impaired growth, reduced egg production and quality, mortality, slaughter downgrading and several ancillary factors including diagnoses, vaccines and antimicrobials to treat intercurrent bacterial infections etc. The etiology of respiratory disease is complex, often involving more than one pathogen at the same time. In many cases, respiratory disease observed in a flock may be a component of a multisystemic disease or it may be the predominant disease with lesser involvement of other organ systems. The respiratory disease complex arises mainly due to existing pathogens or emergence of newer non pathogenic or pathogenic organisms or some of the vaccine strains under immunosuppression aggravated by secondary complications as well as mis-managemental practices. Different respiratory viruses such as influenza virus type A, paramyxovirus types 1,2,3 and 6, and avian metapneumovirus (APV), infectious bronchitis, infectious laryngotracheities virus, fowl pox have been shown to be able to elicit respiratory problems. Viral infections generally cause rather acute respiratory problems from which birds usually can recover fairly easily. The problems, however, become more critical when bacterial pathogens are involved implicated bacteria include Escherichia coli, Pasteurella multocida, Bordetella avium, Ornithobacterium rhinotracheale, Mycoplasma gallisepticum, and Mycoplasma synoviae. Dust, ammonia and other gases, and other factors associated with poor ventilation, may act as predisposing factors. Morbidity is typically 10-20%, and mortality is 5-10%. If condemned birds are included mortality may be more than 10%. Agents that Cause Disease Proper Respiratory Diseases Viral : Infectious Bronchitis (IB) Newcastle Disease/Ranikhet Disease Pox Adeno virus

2 Infectious Laryngotracheitis Avian Influenza Reo Virus Pneumovirus infection Bacterial : Avibacterium paragalinarum (Coryza) Pasteurellosis (Fowl cholera) Mycoplasmosis (CRD) E. coli (URT) Ornithobacterium rhinotracheale Gallibacterium anatis Fungal : Aspergillosis Mycotoxicosis and immunosuppression Nutritional : Toxicities Deficiencies of vitamin A & C Poor protein intake Dusty feed Managemental/ Environmental complication influences : High density Improper ventilation and elevated temperatures High dusty environment Low humidity High ammonia Incidence of mixed respiratory disease complex in poultry: Disease surveys of common meat breed chicken flocks in Australia revealed that 6% of the diseases were due to respiratory problems. In a survey of outbreaks on commercial village chicken in Indonesia 23.3% of birds has respiratory lesions. Interactions with Newcastle disease virus (NDV) or infectious bronchitis Virus (IBV) have long been known to result in a synergistic effect with M. gallisepticum and M. synoviae. Several of the above descriptions about interactions with vaccine strains of NDV with field strains of NDV and IBV are also influenced virulence of the virus strain, allowing the vaccine virus spread from bird to bird, route of exposure to the virus, timing of the virus vs the mycoplasma infection. Three way interactions of mycoplasma with NDV, or IBV, have also been described; which results in more disease than any of the other two agents in combined, chickens exposed to M. gallispeticum and IBV become fully susceptible to E. coli challenge until post challenge. Other respiratory agents are also known interact with M. gallisepticum. Synergism with Avibacterium paragallinarum is well recognized. Then also reports of interaction between M. gallisepticum and infectious laryngotracheitis virus. Some of the important pathogens associated respiratory disease complex in poultry are described in brief. Newcastle Disease: Newcastle Disease is highly contagious disease affects poultry of all ages. Morbidity is usually high and mortality varies 0-100%. The first documented outbreaks of ND occurred in Java, Indonesia and England during 1926, within a year the disease was identified in India and to Philippines. After few years, worldwide occurrence of ND was recorded. Newcastle disease virus (NDV) has been shown to have a wide range of susceptible avian hosts. ND is caused by avian paramyxovirus-serotype 1 (APMV-I) The NDV has a 15 kb negative sense, single stranded non-segmented RNA genome that codes for six major structural protein (HN), fusion protein (F), matrix protein (M), phosphoprotein (P) and nucleoprotein (NP). NDV isolates not only differ in their ability to induce disease and to respond to laboratory tests, but many are themselves genetically heterogeneous, based upon the pathogenicity for chicken and chicken embryo. NDV strains are divided into three different groups viz. lentogenic, mesogenic and velogenic. Velogenic strains cause CNS disturbances along with respiratory signs causing nervous signs with high mortality. Lentogenic strains produce an upper respiratory disease Mild tracheitis. Mesogenic strains cause production drops along with respiratory disturbances.

3 Transmission of ND occurs via aerosols, fomites, and visitors. The virus survives for long periods at ambient temperature, especially in faeces and can persist in houses in faeces, dust (etc) for up to 12 months It is inactivated by temperatures of 56 C for 3 hours or 60 C for 30 min. acidic ph, formalin and phenol, and is ether sensitive. Some of the observations in precipitating ND are:- 1. Use of innumerable vaccines indiscriminately without considering their side effects. 2. Skipping of important vaccines such as R2B 3. Immunosuppression by vaccines, field infections, nutritional toxicities etc. Signs are highly variable and depend on the nature of the infecting virus, the infective dose and the degree of immunity from previous exposure or vaccination. There is sudden death, depression, inappetance, coughing, dyspnea, diarrhea, nervous signs, paralysis, twisted neck, and severe drop in egg production. Airsacculitis, tracheitis, necrotic plaques in proventriculus, intestine, caecal tonsil, haemorrhage in proventriculus, intestinal lesions, primarily occur in the viserotropic form. A presumptive diagnosis may be made on signs, post-mortem lesion, and serology, Virus infection is confirmed by isolation, detection of antigen and antibodies with AGPT, HA/HI VNT, ELISA and IFA, and by molecular detection with PCR. Isolation (from feces, intestinal contents, colacal swabs, tracheal swabs) is done in embryonated eggs by allantoic route or by cell culture. For vaccination lentogenic strains such as Lasota, F and Hitchner s strains, and mesognic strains such as R2B, Mukteshwar, Roakin and H are employed. Infectious laryngotracheitis(ilt): Infectious laryngotracheitis (ILT) is a highly contagious, acute, upper respiratory disease of chickens having worldwide distribution that affects growth and egg production and leading to significant economic losses. The etiologic agent is ILTV, also designated Gallid herpesvirus 1 (GaHV-1), which belongs to the subfamily Alphaherpesvirinae of the family Herpesviridae. The genome of ILTV is a linear double-stranded DNA of approximately 155 kb in size (Neff et al., 2008). Like other herpesviruses, ILTV induces latent infections, mainly in the trigeminal ganglion. Latently infected chickens are the primary source of ILT outbreaks. The increased frequency of outbreaks in poultry has been associated with denser poultry populations, mixing of different type of birds (breeders, leghorns, and broilers) in the same geographical area, shorter down times, and lack in biosecurity. It is believed that most of the outbreaks are caused by chicken embryo origin (CEO) vaccine isolates that persist in long lived bird operations and spill-over broiler populations. The ILT virus may be introduced into the flock through contact with respiratory exudates of affected birds or by fomites, clothing, or vehicles contaminated with secretions from affected birds. Carrier birds that may be survivors from a previous outbreak or vaccinated birds may also introduce ILT. Following introduction of ILTV into a flock the incubation period varying from 6 to 12 days. The natural portal of entry of the virus is the respiratory tract. The target organ system for ILTV infection and disease is the respiratory tract. The epithelium of the trachea and larynx is always affected whilst other mucus membranes, respiratory sinuses, air sacs and lung tissues may periodically also become infected. Co-infections with other respiratory pathogens, and environmental factors adversely affect the respiratory system. Outbreaks are generally more severe in older rather than younger flocks. The disease is characterized by purulent conjunctivitis, sinusitis, nasal discharge, difficulty in breathing, coughing up blood or bloody mucus, swollen orbital sinuses, high morbidity (up to 100%), and decreased egg production in laying hens are characteristic of the acute form of ILT. Chronic ILT may look like any other respiratory infection. Spots of dried bloody exudate may be found in the bird s environment on sidewalls and equipment when flocks are severely affected. Lesions in the tracheas of infected birds vary in type, which reflect the severity and stage of infection. In some cases, the laryngeal and tracheal mucosa is only slightly reddened or has a rough appearance, and the tracheal lumen may contain a small amount of yellow exudate. In other cases, the laryngeal and tracheal mucosa is hemorrhagic, with yellow, bloody, frothy, or thick exudate on the mucosal surface and in the lumen. Exudate may partially or totally occlude the laryngeal glottis or tracheal lumen resulting in death from suffocation. Syncytial epithelial cells with intranuclear inclusion bodies are identified microscopically in tracheas, eyelids (conjunctivae), or lungs. Inclusion bodies may be basophilic or eosinophilic and either fill the entire nucleus or be surrounded by a halo.

4 The battery of possible tests includes the direct fluorescent antibody (DFA) test, histopathology, PCR, virus isolation, and immunohistochemistry. DNA detection by conventional PCR or real-time PCR has become preferred methods of virus diagnosis. In combination with analyses of restriction fragment polymorphisms and DNA sequencing, the PCR technique also facilitates differentiation of virus isolates for epidemiological and phylogenetic studies. Infectious Bronchitis (IB): IB, the commonest respiratory disease of chickens, was first described in the USA (N.Dakota, 1931). It varies with the virulence of the virus, the age of the bird, maternal immunity and complication with other infections (Mycoplasma, E.coli, and Newcastle disease). Morbidity may vary % and mortality range between 0-25%, depending on secondary infections. The cause is a Corona virus that is antigenically highly variable and its new sero-types continue to emerge. These differences are due to structural differences in the spike proteins (SI fraction). Infection occurs via the conjunctiva or upper respiratory tract with an incubation period of hours. The virus is highly contagious and spreads rapidly by contact, fomits or aerosol. Some birds can be act as carriers. The IB virus may survive 4 weeks in premises, is sensitive to solvents, heat (56 C for 15 min), alkalis and disinfectants. Poor ventilation and high density are the main predisposing factors. The clinical signs are characterized by tracheal rales, coughing, sneezing together with accumulation of excess mucous in bronchi, nasal discharge and respiratory rales, gasping, dyspnea, and conjunctivitis. There is depression, huddling, loss of appetite, wet litter, and diarrhea. Decline in egg production, deterioration egg qualities like watery albumin, misshapen eggs and soft shelled eggs are the other manifestations due to permanent damage to the oviducts. Lesions include mild to moderate respiratory tract inflammation, tracheal oedema, tracheitis, excessive mucus in trachea haemorrhage in the trachea and nasal cavities and conjunctivitis, airsacculitis and caseous plugs in bronchi. Infected chickens have serous, catarrhal, or caseous exudation in the trachea, nasal passages and sinuses. Air sacs may appear cloudy or contain yellow caseous exudates. Some strains of virus cause severe damage to kidney, nephrosis and produce stones urolithiasis where kidneys and ureters are swollen and may have chalky white urates. Some strains cause production drops upto 20% or produce false layers in pullets shortening the length of the oviduct. Tentative diagnosis is based on clinical signs, lesions and serology. Definitive diagnosis is based on viral isolation (from tracheal swab or tracheal tissue) after 3-5 passages in chick embryo with typical lesions of curling and dwarfing. FAT and ciliostasis in tracheal organ culture. Serology includes HA/HI, ELISA SNT and AGPT. RT-PCR is the molecular tool for virus detection. Live vaccine (Vaccine strains- Massachusetts, Connecticut and Arkansas) for broilers and inactivated vaccine for layers and breeders are recommended for prevention of the disease. Avian Influenza: Among the respiratory diseases of poultry, avian influenza is the highly infectious and dynamically evolving disease of birds causing huge morbidity and mortality. The recent waves of the avian influenza in Europe have made the global impact of this transboundary animal disease. The latest outbreaks are beyond the scope and resources of a single region to control. This highlights that no country can exempt itself from such disease in future. Avian influenza viruses (AIV) are enveloped, negative stranded RNA viruses, capable of infecting a wide range of bird and animal species including human beings. Avian influenza outbreaks in domestic poultry as well as feral birds occur throughout the world. The presence of virus in migratory birds particularly in anseriformes and charadriiformes and their worldwide migration makes frequent introductions into feral bird populations with regular or occasional spread to domestic birds depending on the prevailing circumstances. AI virus is excreted from the exudates from nares, conjunctiva, and cloaca of infected birds into the environment because of virus replication in the respiratory, intestinal, renal, and/or reproductive organs. The ability of virus to spread must be related to the amount of virus excreted by the respiratory and intestinal tract. Thus, transmission of influenza viruses via the focally contaminated water-oral route is probably a major mechanism of virus dissemination among aquatic birds. The legal or informal trade of live domestic birds and illegal trade were certainly the key routes of introduction of the virus in countries not previously infected. Two types of AIV have been described based on their pathogenicity, namely, a highly pathogenic type (HPAIV) that causes severe disease with high mortality and a low pathogenic type

5 (LPIV) that causes only asymptomatic infection or a mild disease. Highly pathogenic forms are usually of the groups H5 and H7 and may be identified by the presence of a sequence at the haemagglutinin cleavage site that codes for multiple basic amino acids. The virus infects chickens turkeys, ducts, partridges, pheasants, quall, pigeons, and ostriches. Clinical signs, which are commonly seen in HPAI, include cessation of egg laying respiratory signs, rales, excessive lacrimation sinusitis, oedema of the head and face, subcutaneous hemorrhage with cyanosis of particularly of the head and wattles, and diarrhea occasionally neurological signs may be presence. Postmortem lesions include inflammation of sinus trachea, air sacs and conjunctiva, ovarian regression, hemorrhage, necrosis of skin of comb and wattles, subcutaneous oedema of head and neck, dehydrated/congested muscles, hemorrhage in proventricular gizzard mucosae and intestinal lymphoid tissue. The LPAI viruses generally cause decreased egg production mild to moderate infections, but they can also cause morbidity and mortality when the birds are co-infected other agents. Clinical signs in both field and experimental studies with LPAIV revealed swelling the per orbital tissues and sinuses, nasal and ocular discharge, and severe respiratory distress. Gross lesions consisted congestion of the respiratory tissues, and exudation cast formation in the tracheal bifurcation, which extend to the secondary bronchi. The circulation of the LPAI and mixed infection with other respiratory pathogenic particularly infectious bronchitis virus and M. gallisepticum, were incriminated in the high mortality poultry farms and resulting great economic losses. The diagnosis of avian influenza includes clinical inspection, post-mortem examination for the identification of lesions in tissues and organs and laboratory tests serum, tracheal swabs and tissue samples to detect virus or specific antibodies against it. The clinical constantly and are mostly non specific. So isolation of virus from clinical specimens can often significantly in the accurate diagnosis of this disease poultry and other avian species. RT-PCR can detect the gene, even in specimens that were negative for virus standard testing in eggs. This can be combined sequencing the HA cleavage site, which offers sensitive way to access the virulence potential of avian influenza virus. Collibacillosis (Escherichia coli): E.coli is a Gram-negative non-spore forming, rod-shaped bacterium, of the family Enterobacteriaceae. Most strains are motile and have petrichous flagella. Although E. coli is present in the normal microbiota of the intestinal tract, other host mucosal surfaces and in the bird s environment, only a certain number of these strains possessing specific virulence attributes, designated as avian pathogenic E.coli (APEC), are able to cause disease. Colibacillosis refers to any localized or systemic infection e.g. septicemia, peritotnitis, celluitis, salpingitis, osteomyelitis, synovitis, omphaliitis, airsacculitis, and coligranuloma) caused entirely of partly by APEC, and is the most frequently reported disease in surveys of poultry diseases or condemnations at slaughter, hence responsible for severe economic losses. Lesions include milky fluid in pericardium, thin covering of fibrinous exudates on liver and cloudy air sac membranes. Susceptibility and severity of infection are greatest in young birds. Horizontal infection with E.coli usually occurs through contact with other birds, or through faeces, contaminated water and feed. Natural respiratory tract infection of poultry by APEC is thought to occur via the inhalation of faeces-contaminated dust. Dust in poultry houses may contain colony forming units (cfu) E.coli/g. These bacteria may persist for long period, particularly under dry conditions. Vertical infection results from the transmission of E.coli from breeders, via contaminated shells during hatching, or in ovo, as a result of salpingitis. Besides bacterial virulence factors, probably also host resistance is a great determinant of colibacillosis occurrence. In fact, colibacillosis is usually considered to be a secondary disease, following a primary infection with respiratory pathogenic and/or unfavorable environmental conditions. One of the most common forms of colibacillosis begins as a respiratory tract infection and, if unattended, this infection may evolve into a bacteraemia and a generalized infection which manifests as a polyserositis. Barnes et al. (2003) and Dho-Moulin and Fairbrother (1999) described in detail other localized and systemic colibacillosis-associated disease syndromes. Respiratory origin colisepticemia affects both chickens and turkeys and is the most common type of colispeticemia. Lesions are prominent in respiratory tissues (trachea, lungs, and air sacs), pericardial sac and peritoneal cavities and are typical of the subacute polyserositis stage of colibacillosis. Infected air sacs are thickened and often have caseous exudates on the respiratory surface. Pneumonia is more common in turkeys than chickens.

6 Culture isolation and identification, along with indirect HA and ELISA are employed for detection. Antibiotics such as colistin, streptomycin are recommended for its treatment. Mycoplasmosis (Mycoplasma gallisepticum) M. gallisepticum is the most pathogenic and economically significant mycoplasma pathogen causing respiratory disease in chickens and turkeys. Mycoplasma are bacteria that lack a conventional bacterial cell wall and are surrounded only by a thin tri-laminar membrane and they represent the smallest known organisms in nature capable of self-replication. Because of the lack of cell wall it has slow growth cycle and a considerable dependence upon the host for many nutrients for survival. M. gallisepticum infections naturally occur primarily in gallinaceous birds, and are commonly known as chronic respiratory disease of chickens. M. gallisepticum probably can infect susceptible birds at any age, although it is stated that young birds are, in general, more susceptible to infection with M. gallisepticum. Horizontal transmission occurs readily by direct or indirect contact of susceptible birds with infected carriers or contaminated fomites. It is considered to be primarily a surface parasite of the respiratory tract and conjunctiva, although spread to other organs indicates that transient systemic infections occur, resulting in acute and chronic diseases at multiple sites. Vertical transmission of M. gallisepticum is known to occur in eggs laid by naturally infected hens and has been induced following experimental infections. This is suggested to occur as a sequel to acute respiratory infection, due to contiguity of the abdominal air sacs to the oviduct. Clinical signs, morbidity, and mortality associated with M. gallisepticum infection in chickens may be highly variable depending on M. gallisepticum strain virulence, complicating infections, and environmental and other stressors. Clinical signs attributed to M. gallisepticum seen in chickens include sinusitis, respiratory distress, depression, decreased feed intake, and weight loss. As the disease progresses, tracheal rales, coughing, and labored breathing may become evident if tracheitis or airsacculitis are present. The infection may last for months in untreated flocks and an important characteristic of M. gallisepticum is the frequent occurrence of asymptomatic infection. Gross lesions consist primarily of catarrhal exudates in nasal passages, trachea, bronchi, and air sacs. Sinusitis is usually most prominent in turkeys. Air sacs frequently contain caseous exudates, and some degree of pneumonia may be observed. In severe cases of typical air sac disease, there is the triad of airsacculitis, fibrinous or fibrinorpurulent perihepatitis, and adhesive pericarditis resulting in high mortality and extensive condeminations at slaughter. Antibiotic treatment includes Tylosin, oxytetracycline, tiamutin etc. Rapid plate agglutination test (RPAT), HI and FAT are the test of choice for detection. Conclusion and Future Perspectives: In conclusion, seeing the economic significance and involvement of various important pathogens in respiratory disease complex, surveillance and monitoring of respiratory disease complex in different species of poultry supported with an early diagnosis of the condition need to be emphasized employing both conventional and recent molecular detection tools. Vaccination strategy should be followed strictly, and continuous improvement along with new generation vaccine trials be made for the betterment of poultry production and health. Some of the important factors which need to consider in the prevention of RDC in commercial broilers are chick quality, maternal antibody status, immunosuppression, exposure to pathogens and poultry house environment. Necessary ameliorative measures for management of respiratory disease complex in poultry are to be upgraded. Studies on the antibiogram status of the causative agents, monitoring of vaccinal immunity in vaccinated and unvaccinated flocks and modifications of the vaccination programme for the effective control of respiratory disease complex should be given priority. Also status of respiratory disease complex in chickens (broilers, layers and desi), turkeys, quails and guinea fowls of different age groups during different climatic conditions i.e. winter, summer and rainy seasons need to be explored. Managemental measures inclusive of good management practices with high biosecurity measures need proper and due attention.