Poultry Medicine: Chapter 1 PDF

VMED 4305 Chapter 1. Poultry Medicine Elfren F. Celestino Jr., MSc, PhD 1. Mechanism of disease transmission 2. Biosecurity 3. Physiological effect of high ambient temperature 4. Management of flock at high ambient temperature 5. Design of chicken housing 6. Disinfect...

VMED 4305 Chapter 1. Poultry Medicine Elfren F. Celestino Jr., MSc, PhD 1. Mechanism of disease transmission 2. Biosecurity 3. Physiological effect of high ambient temperature 4. Management of flock at high ambient temperature 5. Design of chicken housing 6. Disinfection/Decontamination of chicken houses 7. Water quality Disease Prevention Prevention of disease depends on a comprehensive program incorporating a sequence of planning, implementing and control in a repetitive cycle (Figure 1.1). Strategies to prevent infection are based on the purchase of breeding stock free of vertically-transmitted disease. Vaccination of parent flocks and progeny and appropriate levels of biosecurity represent the components of disease prevention subject to direct managemental control. The components of biosecurity comprise a hierarchy with each of 3 levels (Figure 1.2): Conceptual Biosecurity Structural Biosecurity Operational Biosecurity Conceptual Biosecurity: Includes selecting the location of a complex or operation in a specific area to separate different types of poultry, reduce biodensity, and avoid contact with free-living birds. Siting of farms in relation to public roads and service facilities such as hatcheries, feed mills, and processing plants has a profound impact on the effectiveness of a program to maintain optimal standards of production. Cannot be changed in response to the emergence of new diseases which may result in severe losses or even failure of an enterprise. Structural Biosecurity Layout of farms, erection of fences, construction of drainage, all weather roads, equipment for decontamination, bulk feed installations, change rooms, exclusion of rodents and wild birds, and the interior finishes in houses. Operational Biosecurity Routine managemental procedures intended to prevent introduction and spread of infection within a complex or enterprise. These activities can be modified at short notice to respond to disease emergencies. Constant review of procedures, participation by all levels of management and labor and appropriate monitoring of the health status and immunity of flocks contributes to effective operational biosecurity General Principles The primary purpose of any enterprise is to maximize return on investment over the long-term. It is therefore necessary to market poultry, meat products, and eggs at a price which allows farmers or integrators to maintain profitability in a competitive market. Cost-effective programs of biosecurity and vaccination are required to prevent or limit the impact of disease. Physiological Effects of High Ambient Temperature High ambient temperature exposure of poultry flocks above the zone of minimum metabolism results in an increase in endogenous heat production. Convective transfer of heat is the major thermo-regulatory mechanism of chickens and depends on movement of air by natural or fan-powered ventilation. An increase in convective heat transfer as a result of air movement is proportional to air velocity of up to 100 m/minute, provided ambient air temperature is below body temperature. Physiological Effects of High Ambient Temperature Hyperpnea (panting) occurs in mature chickens exposed to temperatures exceeding 30 ºC. Respiratory rate can increase from 22 breaths/minute (bpm) to 200 bpm when ambient temperature is increased from 27 ºC to 45 ºC within 20 minutes. Panting facilitates evaporative cooling, and above 38 ºC, chickens are almost entirely dependent on latent heat loss for thermoregulation. Prolonged hyperpnea results in excessive excretion of carbon dioxide resulting in respiratory alkalosis. Exposure to high ambient temperature has a profound economic impact on liveability, growth rate, egg production, egg shell quality, and feed conversion efficiency Physiological Effects of High Ambient Temperature Exposure to high environmental temperature for extended periods will suppress the humoral immune response of chickens, reducing antibody titer. It is presumed that a reduction in circulating antibody is associated with a corticosteroid- induced change in serum ions. Cellular immunity is also suppressed by prolonged exposure to temperatures in excess of 36 ºC. Design of Housing in Tropical Countries Convection-ventilated housing is most frequently used in temperate and tropical areas where moderately high seasonal temperatures occur. Structures should be designed to permit passive airflow over the flock. Size and siting of houses in relation to local topography are critical to achieving satisfactory results. The significant design characteristics for convection-ventilated houses relate to internal dimensions, provision of adequate air inlets, and insulation. Convection houses should not exceed 10 m in width to facilitate cross flow of air at low velocity. Design of Housing in Tropical Countries Houses should be oriented in an east-west direction to limit solar heat load, and the interior height at the apex should not be less than 4 m to reduce air temperature at bird level. Roof overhang should extend at least 0.8 m to limit solar gain through the side walls. The lateral ventilation openings should comprise at least 60% of the side 14 wall area and should be fitted with impervious curtains. In modern units, the area of the side opening can be controlled automatically by a thermostatically activated motorized winch with an emergency high temperature release mechanism in the event of power failure. Design of Housing in Tropical Countries Stocking density is generally low (eight to ten broilers or pullets or two to three mature breeders per square meter) compared with more advanced housing, the relatively low capital and operating costs optimize profitability. Simple mechanical and electrical installations and elementary technology for management and maintenance favor the basic convection-ventilated unit in tropical and subtropical areas. To overcome high environmental temperatures, it is necessary to increase the rate of air movement in a house. When daily ambient temperatures exceed 30 ºC with any frequency, mechanical ventilation is required. This can be achieved either by installing fans in closed housing or by selecting an appropriate configuration of air inlets in relation to the dimensions of convection- ventilated units. Management of Flocks at High Temperature Pad cooling systems are used extensively in Asia, the U.S.A. and Latin America, where seasonally high temperatures are encountered. The principal deficiency of the pad lies in the inherently lower efficiency of evaporation compared with the ultra-high pressure fogger. Modern cooling pads are composed of cellulose material in a honeycomb configuration to increase surface area. Although this enhances cooling, the system is susceptible to algae and mineral contamination in water. The efficiency of cooling may be enhanced by spraying pads with water from suitably placed nozzles. Management of Flocks at High Temperature The survival of birds at high temperature is strongly influenced by the volume of water consumed. Cold water functions as a heat sink in the intestinal tract and surface evaporation from the comb, wattles, and head exerts a cooling effect. It is essential to provide additional watering points to facilitate consumption in areas where ambient temperature exceeds 3º∫C for more than 2 hours per day. Recommendations include 1 suspended drinker with a diameter of at least 40 cm, for 75 broilers or 50 breeders and 1 cup or nipple per cage of up to 5 commercial layers. Insulation of header tanks and supply piping is indicated if the temperature of water at the point of consumption exceeds 25ºC. PREVENTION OF DISEASE Prevention of disease in commercial poultry operations requires the application of a coordinated program of biosecurity, vaccination and hygiene. Mechanisms of Disease Transmission In order to develop control procedures, it is important to understand the mechanisms by which pathogens are introduced into commercial poultry farms and how disease agents are disseminated among units. Biological transmission occurs when the pathogen multiplies in the infected host which then transmits the agent when placed in contact with susceptible flocks. Mechanical transmission involves transfer of a pathogen from an infected source or reservoir host to a susceptible flock by contaminated personnel, equipment, insect vectors, rodents, wild birds, or dust carried by wind. Transovarial Route Pathogens may be transmitted by the vertical route from hen to progeny via the egg. Mycoplasmosis, pullorum disease (Salmonella pullorum), reoviruses and adenoviruses are transmitted in this way. Salmonella enteritidis (Se) may also be transmitted vertically by incorporation of the bacterium into the albumen of the egg in the oviduct. Transmission on the Egg Shell Pathogens such as E. coli and paratyphoid Salmonella spp deposited from the cloaca or nest-box litter can penetrate the shell and infect the developing embryo. This form of vertical transmission results in contamination of the hatchery environment and direct and indirect infection of chicks. Omphalitis and salmonellosis may be introduced into brooding and rearing units by contaminated egg-shells. Direct Transmission Contact between susceptible flocks and clinically affected or asymptomatic reservoirs of disease will result in infection. This situation occurs in multiage units and is a common method of transmitting salmonellosis, coryza, mycoplasmosis, laryngotracheitis and pasteurellosis. Indirect Transmission Introduction of contaminated transport coops, equipment or feed onto farms or movement of personnel between infected and susceptible flocks without appropriate biosecurity measures will effectively transmit disease. Imperfectly decontaminated buildings which have housed infected flocks often contain pathogens including infectious bursal disease virus (IBDV) and Salmonella spp which can infect successive placements especially when interflock intervals are less than 10 days in duration. Dissemination by Wind Infected flocks may excrete large numbers of viruses which can be entrained in dust and moved by wind for distances of up to 5km. Spread of vvND and ILT by wind has been documented in several outbreaks. Biological Vectors Wild birds are reservoirs of avian influenza and Pasteurella spp. Rodents carry a wide range of diseases including pasteurellosis and salmonellosis. Insects are responsible for transmission of various diseases. Pox, West Nile and Highland J arbovirus may be transmitted by mosquitoes and spirochetosis by Argas ticks. Litter beetles (Alphitobius diaperinus) are reservoirs of a wide range of infections including Marek’s disease, IBD, salmonellosis, pasteurellosis and coccidiosis. House flies transmit campylobacteriosis. Argasid ticks (Argas spp) are vectors of spirochetosis. Feed Contamination of ingredients or manufactured feed with pathogens such as Salmonella spp, or IBD and paramyxovirus virus can result in infection of susceptible flocks. Vaccines Contaminated poultry vaccines prepared in eggs derived from non-specific pathogen free (SPF) flocks may contain pathogens including adenoviruses, reoviruses, or the agents responsible for chicken anemia and reticuloendotheliosis. Pathogens may also be transmitted among flocks as a result of contaminated vaccination equipment or personnel used to administer vaccines. Biosecurity Evaluating the biosecurity of ongoing operations is important in developing effective programs to prevent the introduction of disease into a complex or to limit subsequent dissemination among farms. A successful biosecurity program presumes an understanding of the principles of epidemiology and economics and requires teamwork to maximize benefits. Biosecurity Biosecurity programs require a structured approach involving the following sequence: Planning and evaluation of programs. Locating resources and training of personnel. Implementing including erection of facilities. Control involving review of results and analytical procedures. Conceptual Biosecurity Location of the complex in relation to concentrations of poultry of the same or different species. Distance among breeder and grow out farms and facilities such as hatcheries, feed mills, and processing plants or packing units. Location of major and minor roads and the movement of commercial and backyard poultry in relation to company facilities. Proximity to large lakes or waterways or migratory flyways. For commercial egg production consider the implications of multi-age on-line units or single-age, company-owned or contractor-operated facilities. Structural Biosecurity Fenced farm area with notices to prevent trespass. Fencing of house area, with secured gates. Water supply free of pathogenic bacteria and chlorinated to a level of 2 ppm. Farm service module comprising an office, storage, and change roomshower facilities. Concrete apron with a suitable water and power supply to permit decontamination of vehicles entering the farm. All-weather roads within secured perimeter to facilitate cleaning and to prevent dissemination of disease agents by vehicles and footwear. Appropriate location of bulk bins or secure, vermin-free storage areas for bagged feed. Installations for disposal of dead birds (incinerators, composters, pits). Structural Biosecurity Secure housing with appropriate bird and rodent proofing. Concrete floors for breeding stock at the grandparent level. In many countries with endemic salmonellosis, concrete floors are required in both rearing and laying housing for breeders. Correct positioning of extractor fans to prevent airborne transmission of pathogens to flocks in adjacent houses. Impervious apron adjacent to the door of each house and installation of drains. Feed, unused litter and cleaned equipment should be stored in a module separated from the live-bird area of the house to prevent contamination of flocks by delivery and maintenance workers. Operational Biosecurity Operational manuals should be developed for routine procedures carried out in feed mills, hatcheries, breeding and grow out facilities. Manuals should incorporate contingency plans in the event of a deviation from normal production parameters or outbreaks of disease on company farms or in units located in close proximity to the operation. Manuals should be developed for appropriate levels of management including company veterinarians and health maintenance professionals, service personnel, contractors, and employees. Operational Biosecurity Standardized procedures should address specific aspects of operation including: Decontamination and disinfection of units following depletion of flocks. Storage, reconstitution and administration of vaccines according to recommended route. Specific procedures on entering and leaving farms should be designated for managers, supervisors, authorized visitors, work crews and permanent and part-time employees. Controls required to prevent contact with exotic avian species, and backyard poultry. Decontamination of Housing and Equipment Decontamination is the process of physically removing biological and inorganic material from the surfaces of a building or equipment. Disinfection is the destruction of pathogenic organisms. Decontamination Thorough decontamination is necessary to achieve effective disinfection. Cleaning programs require planning followed by implementation and control to ensure satisfactory preparation of surfaces for subsequent application of disinfectants. Disinfectants Several compounds are available commercially, each with characteristics for specific applications. Cresols, derived from petroleum distillation are cheap and effective biocides when applied to buildings and soil. These compounds should not be used in the presence of live poultry, eggs, or processed meat as tainting of products will occur. Organic phenols are suitable for use in hatcheries to decontaminate equipment. Quaternary ammonium compounds (QATs) are highly recommended to decontaminate housing, equipment, and in hatcheries provided that an anionic detergent precedes application of a QAT. Disinfectants Chlorine compounds are widely used in processing plants and to purify water on farms. Hypochlorite is only effective over a pH range of 6.5 to 7.5 in water free of organic matter and requires 10 - 20 minutes exposure to inactive bacteria Formalin is a corrosive and potentially carcinogenic compound suitable to fumigate eggs in purpose-designed cabinets. Use of formalin requires special precautions to avoid exposure and injury to applicators who must be provided with protective clothing, functional equipment and chemical monitors. Disinfection of Poultry Houses Complete depopulation of houses and decontamination of units and surroundings at the end of each broiler, rearing, breeder or layer cycle will contribute to enhanced liveability and performance in subsequent flocks. Disinfection of Poultry Houses The following procedures should be followed: The surface of the litter and the lower side walls should be sprayed with a 2% carbamate insecticide. Litter should be graded to the center of the house for removal either manually or with a front-end loader. Litter should be either bagged or alternatively transported in bulk from the house to a central site for composting or disposal. Equipment should be disassembled and removed from the house for cleaning and disinfection Disinfection of Poultry Houses Electrical units, motors, and switch gear should be cleaned using a high-pressure air spray and then sealed to protect installations from water damage. The floor of the house should be swept to remove residual litter. The house should be decontaminated by spraying a non-ionic detergent at a concentration recommended by the supplier. Detergent should be applied to the exterior in the sequence of roof, exterior walls, drains, and service areas. Cleaning the interior should follow the sequence of ceiling, internal walls, and then the floor. Disinfection of Poultry Houses The interior structure and equipment should be rinsed with water and remaining detergent solution should be allowed to drain. The interior of the house should then be sprayed with a quaternary ammonium or phenolic disinfectant solution at a concentration recommended by the manufacturer. A cresolic disinfectant can be applied to earth floors. A 2% carbamate insecticide solution should be sprayed on the ceiling, walls, and floor to control litter beetles. (Alphitobius spp) Disinfection of Poultry Houses Equipment should be reassembled and routine preventative maintenance completed. A clean, dry substrate (wood shavings, groundnut hulls, rice hulls, sawdust) should be spread to a depth of 3 - 10 cm, over the floor area. Breeder houses should be sealed and fumigated with formalin generated from heated paraformaldehyde or from a mixture of formaldehyde and potassium permanganate. A fog generator can also be used to distribute formalin in aerosol form through the house. It is emphasized that formalin is a toxic compound and is potentially carcinogenic. Disinfection of Poultry Houses Water lines and drinkers should be drained and cleaned. A quaternary ammonium compound (1 - 2,000 dilution) or chlorine solution (1 liter of 6% sodium hypochlorite per 8 liters of water as a stock solution, proportioned at 1%) should be used to flush water lines. Rodent control measures should be implemented including sealing of burrows and baiting. Control of Rodents Rodents are nocturnal and are active after lights have been turned off. Rats and mice are seldom seen during the day unless infestation is very heavy. Colonization can be detected by the presence of active nesting sites in attics, in cracks in concrete slabs, under cages, in manure, in corners, or in burrows around the foundation walls. Fresh droppings may be observed around the inner perimeter of the poultry house. Outdoor burrows may be closed by filling with soil and observed for reopening of entrances. The frequency of catching rodents in traps may also be used to assess the level of infestation. Control of Rodents Rats and mice are significant pests in poultry facilities. They cause damage to building structures, including foundations, water lines, electrical cables, switch gear, and insulation. Rodents are major vectors and reservoirs of poultry and zoonotic pathogens, including Pasteurella multocida, Salmonella typhimurium and S. enteritidis. Mice amplify environmental contamination and will infect poultry and products. Rodents serve as mechanical transmitters of infectious agents such as influenza and infectious bursal disease viruses and Salmonella and Pasteurella spp. Control of Rodents A continuous integrated program to control rodents includes rodent proofing of buildings, elimination of nesting places, appropriate management and sanitation, and chemical and nonchemical elimination. Preventing access to feed, water, and shelter is an important part of a rodent-control program. Chemical methods to control rodents include bait and tracking powder. All rodenticides are poisonous at various levels for poultry, livestock, and humans. Caution in the use of rodenticides is required, and manufacturer’s label instructions should be strictly followed. A single-dose rodenticide will kill rodents after one feeding if an adequate amount is consumed. Multiple-dose compounds have a cumulative effect and will kill rodents after several feedings Control of Free-Living Birds Free-living migratory and resident birds serve as reservoirs and disseminators of numerous infections of commercial poultry. These include Newcastle disease, avian influenza, duck viral enteritis, chlamydiosis, salmonellosis, and pasteurellosis. The following precautions can be applied to reduce the probability of infection: Water obtained from lakes or ponds on which waterfowl accumulate must be filtered and treated with chlorine to a level of 2 ppm. Control of Free-Living Birds Buildings housing flocks and warehouses should be bird-proofed. This includes netting over air inlets, exhaust openings, and screen doors. A commercial product, Avipel® (9,10-anthraquinone) can be applied as a paint suspension to roof areas, gantries and structures where resident pigeons and sparrows congregate. Quality of Water Water supply for farms and hatcheries should be obtained from a municipal source which is filtered and chlorinated or from a deep (+50m) cased well or from a filtered and treated source from a dam or river. Water containing mineral impurities can affect skeletal integrity, intestinal function and detract from optimal growth and feed conversion efficiency. Microbiological contamination including fecal coliforms and viable Newcastle disease and avian influenza viruses can result in infection of flocks. Standards for mineral and microbiological quality are shown in Table 4.1. Chlorine can be added to drinking water at a level of 2 ppm using either sodium hypochloride or a gas chlorine installation. For effective treatment the pH of water should be adjusted within the range of 6.5 to 7.5. Water lines can be flushed and decontaminated with solutions as indicated in Table 4.2. Thank you..