Medicina pediĂĄtrica en pequeĂąos animales
Presentation brochure
Siempre portada Servet
Vaccination in poultry
Authors: Francisco Javier Torrubia Díaz, Sonia
Téllez Peña, Cristina Gómez Martínez, Rüdiger Hauck, Thierry van den Berg.
Format: 22 × 28 cm. Number of pages: 208. Number of images: 290. Binding: hardcover.
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Vaccination is one of the cornerstones of poultry production. In fact, it is one of the aspects that most influence production parameters in the poultry industry. In broilers, the optimum time of vaccination should aim at obtaining the maximum meat yield. In layers and breeders, both time and the route of administration have an influence in the quality of egg shells and the number of eggs per laying, among others.
Vaccination in poultry
Presentation of the book Vaccination is probably the main, although not the only, method for the control of diseases in poultry. More effective vaccination schedules should be accompanied both by good biosecurity practices and by programmes for constant epidemiological surveillance, especially in the case of specific notifiable diseases. This combination of measures forms a true health programme for the control of these diseases. The purpose of vaccination is to protect animals from possible disease outbreaks. Therefore, the first element that needs to be taken into account is that only clinically healthy birds should be vaccinated. In addition, it should not be forgotten that the correct application of biological products is decisive to achieve this objective. This book addresses vaccination and is divided into four essential parts: the first chapter deals with diseases of viral origin, which are probably the most numerous; the second chapter addresses diseases of bacterial origin; the third chapter includes parasitic diseases, which are more complex due to their specific immune mechanisms; and finally, the book concludes with a chapter about the vaccines of the future. We, the authors, are convinced of the unquestionable clinical value of this book, even though we know that vaccination is a highly dynamic concept that evolves rapidly, as can be concluded from the section on the vaccines of the future. In addition, we must also be aware of the fact that, in practice, there is no single, infallible and universal vaccination programme. Programmes vary according to the diseases present in the different regions, the level of challenge, the appearance of new serotypes or variants, not to mention emerging diseases, etc. That is why the validity of the information contained in this book may suddenly vary, and we believe regular updates will be necessary. Finally, I would like to especially thank StÊphane Lemière and Francisco Rojo for their selfless help in gathering information about vaccination in different countries, as well as the specialists that have allowed us to use their images of numerous diseases, without which this book would have been much less visual and instructive. I hope and wish this book is of use to its readers; I have contributed to it with great enthusiasm and tried to update all the knowledge I have acquired throughout my more than 30 years of dedication to vaccination in poultry. Furthermore, I would like to congratulate and thank the rest of authors of this book for their enthusiasm and interest in transmitting their experience with a multidisciplinary approach. Javier Torrubia
Authors Francisco Javier Torrubia Díaz Graduated from the Universidad Complutense of Madrid in 1976, Javier Torrubia owns a vast experience as a specialist in avian health, both in egg and meat production. His areas of expertise include the study of poultry diseases, as well as the management and establishment of health and vaccination programmes. Javier Torrubia has worked with many national and international companies, and has attended many national and international meetings and congresses all over the world.
Sonia Téllez Peña Dr Téllez obtained her Veterinary Degree (1998) and PhD (2003) from Universidad Complutense of Madrid (UCM) in Spain. She joined the Department of Animal Health of UCM in 1999 with her doctoral thesis “Detection and characterisation of Salmonella spp. in reptiles and amphibians”. Since then, she has been doing research within the VISAVET Health Surveillance Centre of the UCM, focusing mainly in the surveillance of the microorganisms responsible for food-borne zoonoses and antimicrobial resistances. She is currently doing research in the private sphere.
Cristina Gómez Martínez Cristina Gómez received her Veterinary Degree from the University of Extremadura (Spain) in 2007 and her Master on Food Safety in 2010 from the College of veterinary surgeons of Madrid and the Universidad Complutense of Madrid (UCM). The research project she presented at the end of her studies dealt with “Application, assessment and improvement of management plans as the basis of a system based on HACCP principles, in order to reduce the prevalence and the risk of introduction and spreading of food-borne zoonoses in poultry meat”. Currently, she is in charge of the Unit of Project Management of VISAVET Health Surveillance Centre of the UCM.
Vaccination in poultry
Rüdiger Hauck Certified Veterinary Specialist for Poultry Diseases and Microbiology and Diplomate of the European College of Poultry Veterinary Science, Dr Rüdiger Hauck received his degree in Veterinary Sciences from Freie Universität Berlin in 2002. His areas of interest include viral vaccination studies, detection and typing of bacterial pathogens, and studies on protozoan parasites. At present, he is a Veterinary Consultant at the Bundesamt für Verbraucherschutz und Lebensmittelsicherheit, where Dr Hauck is a member of the team Antimicrobial Resistance.
Thierry van den Berg Dr van den Berg holds a DVM (University of Liège, Belgium, 1983), a MSc in Molecular Biology and Biotechnology (University of Brussels, Belgium, 1987) and a PhD in Sciences (University of Brussels, Belgium, 1994). He is also a member of the European Society for Veterinary Virology. He is currently the Operational Director of the unit “Viral Diseases” in CODA-CERVA and the former Head of the Small Stock Diseases Section at VAR, where he coordinated various studies on Avian Viral Diseases of Poultry. Dr van den Berg has a particular interest in promoting collaboration between research teams in Europe, training of young scientists and disseminating know-how and technology in the poultry field. He is also member of the editorial board of Avian Pathology.
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Table of contents 1. VACCINATION AGAINST VIRAL DISEASES. Marek’s disease
Avian encephalomyelitis Description of the disease Affected parameters and clinical signs
Description of the disease
Vaccination
Affected parameters and clinical signs
Relationship between vaccination
Vaccination
and disease control
Relationship between vaccination
Performance parameters that should be monitored
and disease control Performance parameters that should be monitored
Newcastle disease
Avian influenza Description of the disease Affected parameters and clinical signs
Description of the disease
Vaccination
Affected parameters and clinical signs
Relationship between vaccination
Vaccination
and disease control
Relationship between vaccination
Performance parameters that should be monitored
and disease control Performance parameters that should be monitored
Infectious bronchitis
Avian pneumovirus Description of the disease Affected parameters and clinical signs
Description of the disease
Vaccination
Affected parameters and clinical signs
Relationship between vaccination
Vaccination
and disease control
Relationship between vaccination
Performance parameters that should be monitored
and disease control Performance parameters that should be monitored
Infectious bursal disease
Infectious laryngotracheitis Description of the disease Affected parameters and clinical signs
Description of the disease
Vaccination
Affected parameters and clinical signs
Relationship between vaccination
Vaccination
and disease control
Relationship between vaccination
Performance parameters that should be monitored
and disease control Performance parameters that should be monitored
Fowlpox
Chicken anemia virus infection Description of the disease Affected parameters and clinical signs
Description of the disease
Vaccination
Affected parameters and clinical signs
Relationship between vaccination
Vaccination
and disease control
Relationship between vaccination
Performance parameters that should be monitored
and disease control Performance parameters that should be monitored
Egg drop syndrome Description of the disease Affected parameters and clinical signs Vaccination
Relationship between vaccination and disease control Performance parameters that should be monitored
Fowl cholera
Relationship between vaccination
Description of the disease
and disease control
Affected parameters and clinical signs
Performance parameters that should be monitored
Vaccination
Reovirus Description of the disease Affected parameters and clinical signs Vaccination
Relationship between vaccination and disease control Performance parameters that should be monitored
Avian colibacillosis
Relationship between vaccination
Description of the disease
and disease control
Affected parameters and clinical signs
Performance parameters that should be monitored
Vaccination
References 2. VACCINATION AGAINST BACTERIAL DISEASES Pullorum disease and fowl typhoid
Relationship between vaccination and disease control Performance parameters that should be monitored
Ornithobacterium rhinotracheale infections
Description of the disease
Description of the disease
Affected parameters and clinical signs
Affected parameters and clinical signs
Vaccination
Vaccination
Relationship between vaccination
Relationship between vaccination
and disease control Performance parameters that should be monitored
Infectious coryza
and disease control Performance parameters that should be monitored
Mycoplasma synoviae infections
Description of the disease
Description of the disease
Affected parameters and clinical signs
Affected parameters and clinical signs
Vaccination
Vaccination
Relationship between vaccination
Relationship between vaccination
and disease control Performance parameters that should be monitored
Mycoplasma gallisepticum infections
and disease control Performance parameters that should be monitored
Paratyphoid
Description of the disease
Description of the disease
Affected parameters and clinical signs
Affected parameters and clinical signs
Vaccination
Vaccination
Relationship between vaccination and disease control Performance parameters that should be monitored
Other bacterial diseases Erysipelas
3. VACCINATION AGAINST PARASITIC DISEASES Introduction
Coccidiosis Introduction
Description of the disease
Causative agent
Affected parameters and clinical signs
Prophylaxis by other means than vaccination
Vaccination
Immunity against coccidiosis
Relationship between vaccination
Vaccination
and disease control Performance parameters that should be monitored
Necrotic enteritis Description of the disease Affected parameters and clinical signs Vaccination Relationship between vaccination and disease control Performance parameters that should be monitored
Bacterial diseases specific to turkeys and ducks Bordetellosis
Vaccines against other parasites Leucocytozoon caulleryi Histomonas meleagridis Dermanyssus gallinae Ascaridia galli
References 4. VACCINES OF THE FUTURE. FOCUS ON VIRAL DISEASES Introduction Measurement of the protective immune response Limitations of classical live and inactivated vaccines
Affected parameters and clinical signs
Molecular engineering of modified classical live vaccines
Vaccination
Vector vaccines
Relationship between vaccination
Subunit vaccines
Description of the disease
and disease control Performance parameters that should be monitored
Infections with Riemerella anatipestifer
Adjuvant and formulations Immune complexes In ovo vaccination
Affected parameters and clinical signs
Perspectives: focus on hatchery vaccination
Vaccination
Conclusions
Relationship between vaccination
References
Description of the disease
and disease control Performance parameters that should be monitored
References
VACCINATION AGAINST VIRAL DISEASES ChICkEN ANAEMIA VIRuS INFECTION
a
b
Figure 6. Specific lesions caused by CAV. Pale and atrophied bone marrow. (a) Image courtesy of Dr Rafael Fernández. (b) Image courtesy of Dr Pedro Villegas.
a
b
Figure 7. Specific lesions caused by CAV. Pale and atrophied thymus. (a) Image courtesy of Dr Rafael Fernández. (b) Image courtesy of Dr Pedro Villegas.
The most important route of transmission is vertical, via the egg. This is the primary cause of anaemia in young birds. Transmission through the egg occurs between 8 and 14 days after infection of the hen and persists at the field level for about nine weeks, peaking at 1-3 weeks, and affecting up to 100 % of the flock. In these cases, some of the chicks infected by vertical transmission are born with pancytopenia and develop clinical disease between 7 and 14 days of age.
Figure 8. Gangrenous dermatitis. Image courtesy of Dr Rafael Fernández.
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VACCINATION IN POULTRY
After intestinal replication, the virus spreads throughout the entire body via the bloodstream. The most pathogenic viruses are located in the tibiotarsal joint, where they cause arthritis. The liver may also be affected. One-day-old chicks are more sensitive than older birds: the younger the infected bird the more likely they are to develop disease.
Affected parameters and clinical signs The symptoms most commonly produced by reoviruses are viral arthritis and tenosynovitis. These symptoms are usually observed in birds of 3-4 weeks of age; between 5 % and 10 % of the population of the farm are affected, and show varying degrees of lameness and stiffness. Affected birds exhibit inflammation of the hock joint (Fig. 1), limb paralysis (Fig. 2) and clenched feet in cases of bilateral paralysis. Inflammation of the digital flexor tendons and the metatarsal extensors is observed (Fig. 3), and to a lesser extent, of the footpad and tarsal joint (Figs. 4 and 5). The inflammation of tendinous areas subsequently progresses to the formation of chronic lesions characterised by the hardening and fusion of tendon sheaths. The gastrocnemius tendon may rupture (Fig. 6) in older birds (Jones et al., 1975). A significant percentage of infected birds show stunted growth (Fig. 7). Mortality ranges from 2-10 %. MAS is characterised by continuous lesions of the mucosa of the small intestine, stunting (Fig. 8), prostration, pallor of the mucous membranes and appendages of the head, poor pigmentation of the shanks (Fig. 9), abnormal feathering (helicopter disease; Fig. 10), diarrhoea and bloating.
Figure 1. Open hock joint with marked inflammation. Image courtesy of Dr Rafael Fernández.
Figure 2. Paralysis of the legs in a chicken affected by avian reovirus. Image courtesy of CESAC.
Lesions Necropsy reveals inflammation of the gastrocnemius and the flexor tendon (Fig. 11); in severe cases, rupture of the gastrocnemius tendon may be observed. Marked oedema of the tarsal and metatarsal tendon sheaths is observed at the onset of infection. The affected tarsus or hock shows bloody or yellowish exudate (Fig. 12). MAS may be accompanied by disorders of the digestive system such as proventriculitis, enteritis, pancreatitis and pancreatic atrophy. Examination of the intestines may reveal undigested food or water, peeling of the intestinal mucosa, and in some cases hypertrophy of the proventriculus. Lesions typical of viral arthritis are also quite common, and some authors have described necrosis of the humeral head (Fig. 13).
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Figure 3. Swollen tarsus and joint in chicken with viral arthritis. Image courtesy of Dr Rafael Fernández.
VACCINATION AGAINST VIRAL DISEASES REOVIRuS
Figure 4. Swollen footpad in chicken affected by reovirus. Image courtesy of Dr Rafael Fernรกndez.
Figure 5. Swelling of the leg and lower joints in chicken with viral arthritis. Image courtesy of Dr Antonio Hernรกndiz.
Figure 6. Ruptured tendon in chicken affected by avian reovirus. Image courtesy of CReSA.
Figure 7. Differences in the growth within a batch of chickens affected by avian reovirus. Image courtesy of CESAC.
Figure 8. Delayed growth in a batch of chickens affected by avian reovirus. Image courtesy of CESAC.
Figure 9. Altered shank pigmentation in chicken affected by avian reovirus. Image courtesy of Dr Rafael Fernรกndez.
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VACCINATION IN POULTRY
2. Infectious coryza Description of the disease Infectious coryza is an acute disease of the upper respiratory tract that affects chickens and hens (Gallus gallus) and is caused by the bacterium Avibacterium paragallinarum (Blackall and Soriano-Vargas, 2013). The disease is distributed worldwide and causes severe economic losses in the poultry industry both in egg-laying birds, due to a reduction in egg production (10-40 %) and in broilers, due to stunting and an increase in the number of birds culled (Blackall and Soriano-Vargas, 2013). All members of the species Gallus gallus are natural hosts and are susceptible to infection at any age. However, the bacterium has also been isolated from quail, pheasants, guinea fowl and parrots. It is generally considered to be a primary pathogen in susceptible birds (Blackall and SorianoVargas, 2013).
bacteria was eventually reclassified in the new genus Avibacterium (Blackall et al., 2005). A. paragallinarum is a very sensitive bacteria with little environmental resistance. It is transmitted by direct contact between animals (nasal or ocular discharge), in the air (aerosols), or by indirect contact with fomites or contaminated water or food.
A primary pathogen is one that causes disease in a healthy individual. A secondary or opportunistic pathogen is one that causes disease only in cases of a pre-existing state of immunosuppression (due to stress, primary infection, etc.). A. paragallinarum is a gram-negative bacterium (Fig. 1) belonging to the family Pasteurellaceae. It is characterised by its dependency on nicotinamide adenine dinucleotide (NAD) as a growth factor in culture medium. NAD (also known as V-factor) can be added to the medium or supplied by a feeder bacteria (Staphylococcus aureus) cultivated in parallel to A. paragallinarum (Fig. 2). NAD-independent strains have been isolated in Mexico and South Africa (Soriano-Vargas and Terzolo, 2004a; Blackall and Soriano-Vargas, 2013). In 1932, De Blieck proposed the name Bacillus haemoglobinophilus coryzae gallinarum for the causal agent of “contagious catarrh” of chickens. Subsequently, Biberstein and White proposed the establishment of a new species (Haemophilus paragallinarum) for the V-factor dependent microorganism that causes infectious coryza (Soriano-Vargas and Terzolo, 2004a; Blackall and Soriano-Vargas, 2013). In 2005, based on the results of 16S rRNA sequencing studies, the
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Figure 1. Gram stain. Typical gram-negative bacilli of the family Pasteurellaceae (Public Health Image Library, CDC).
Figure 2. Satellite colonies of A. paragallinarum growing around a stretch of Staphylococcus aureus (Public Health Image Library, CDC).
VACCINATION AGAINST BACTerIAl DISeASeS INfeCTIOuS COryzA
Vertically transmission has not been described. This disease has the greatest impact in multi-age sites (Soriano-Vargas and Terzolo, 2004b; Blackall and Soriano-Vargas, 2013).
The main reservoirs of infectious coryza are chronically infected birds and asymptomatic carriers. Based on the results of haemagglutination inhibition tests, isolates of A. paragallinarum were classified into three serotypes: A, B and C (Page, 1962). Subsequently, Kume et al. (1983) identified seven haemagglutinins (H1 to H7) distributed across the three serogroups. Based on these findings and the identification of two additional haemagglutinins, Blackall et al. (1980) combined the two groupings and altered the nomenclature to recognise nine serovars within these serogroups: A-1, A-2, A-3, A-4, B-1, C-1, C-2, C-3 and C-4 (Soriano-Vargas and Terzolo, 2004a; Blackall and SorianoVargas, 2013). The development of this classification system is shown in Table 1. This classification is clinically important because the pathogenicity and immunogenicity of A. paragallinarum strains are directly correlated with their haemagglutinating capacity, and no cross-protection is observed between the different serogroups (Soriano-Vargas and Terzolo, 2004a; Blackall and Soriano-Vargas, 2013). Another factor implicated in the pathogenicity and virulence of A. paragallinarum is the capsule,
which is associated with colonisation capacity and protection against the bactericidal effect of serum, and has even been proposed as a key factor in the development of lesions associated with coryza (Blackall and Soriano- Vargas, 2013). The pathogenicity and immunogenicity of A. paragallinarum strains correlate directly with their haemagglutinating capacity. No cross-protection is observed between different serogroups. No risk to public health has been demonstrated for this bacteria or any other members of the genus Avibacterium (Blackall and Soriano-Vargas, 2013).
Affected parameters and clinical signs The characteristic signs of infectious coryza include depression, serous or mucoid nasal discharge (Fig. 3), sneezing, inflammation of the infraorbital sinuses (Fig. 4), facial oedema and conjunctivitis (Fig. 5). Inflammation of the wattles (Fig. 6) may be particularly evident in males. Tracheal rales may also be heard in birds with lower respiratory tract involvement (Soriano-Vargas and Terzolo, 2004b; Blackall and SorianoVargas, 2013). More severe respiratory symptoms may be observed in cases of concomitant infection with Mycoplasma synoviae,
Table 1. Evolution of the classification of A. paragallinarum. Source: BM Editores, 2014. PAGE, 1962
A
B
C
STRAIN
0083
0022
Modesto
KUME ET AL., 1983
STRAIN
BLACKBALL ET AL., 1990
STRAIN
ORIGIN
HA-1
221
A-1
221
Japan
HA-2
2403
A-2
2403
Germany
HA-3
E-3C
A-3
E-3C
Brazil
-
-
A-4
HP-14
Australia
HA-7
2671
B-1
2671
Germany
HA-4
H-18
C-1
H-18
Japan
HA-5
Modesto
C-2
Modesto
United States
HA-6
SA-3
C-3
SA-3
South Africa
-
-
C-4
HP-60
Australia
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VACCINATION IN POULTRY
Table 2. Performance parameters affected by colibacillosis (adapted from Vandekerchove, 2004). PARAMETER AFFECTED
LAYERS/BREEDERS BROILERS Yes Decreased hatchability Yes Developmental delays Yes Increased feed conversion rate Yes Yes Increased mortality Yes Yes Increase in number of birds culled Yes Yes Increased number of Yes condemnations at processing Decreased egg production
Figure 4. Haemorrhagic swelling and congestion of the ovary and oviduct caused by E. coli. Image courtesy of Dr Manuel Pizarro.
The symptoms and the morbidity and mortality caused by E. coli vary greatly depending on the presentation of the disease and the age of affected animals (Lutful Kabir, 2010; Nolan et al., 2013). Colibacillosis of respiratory origin usually affects young animals acutely, with morbidity reaching 50 % and mortality ranging from 5 % to 10 %. Clinical symptoms include respiratory difficulties or dyspnoea accompanied by rales (Vandekerchove, 2004; Nolan et al., 2003). In adult layers and breeders the most common clinical form is salpingitis, with or without peritonitis (Figs. 5 and 6). This is a chronic disease with a slow course and a mortality rate of 2-3 %. The production performance of egg-laying hens decreases due to a slight fall in egg production. In broilers,
Figure 5. Necrotising typhlitis caused by E. coli (haematoxylin-eosin staining). Image courtesy of Dr Manuel Pizarro.
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the main manifestations are swollen head syndrome, cellulitis and airsacculitis (Vandekerchove, 2004; Nolan et al., 2003). Table 2 shows the performance parameters most affected by APEC infection in poultry.
Vaccination Due to the great genetic and antigenic diversity among APECs, vaccination it not an effective preventive measure, and its use is limited. The protection afforded by vaccination is dependent on the antigen specificity of the vaccine strain; vaccines thus protect only against antigenically homologous field strains (Lutful Kabir, 2010; Nolan et al., 2013).
Figure 6. Egg-laying hen with fibrinous peritonitis and salpingitis caused by E. coli. Image courtesy of Dr Manuel Pizarro.
VACCINATION AGAINST BACTerIAl DISeASeS AVIAN COlIBACIllOSIS
In 1947, Kauffmann proposed a method to differentiate between E. coli strains by determining the surface antigens. This allows differentiation between innocuous and virulent strains (Fig. 7). In most countries, the serotypes most commonly associated with cases of avian colibacillosis are O1, O2 and O78.
Cell wall (endotoxin, O antigen)
Capsule (K antigen)
It is important to note that a single outbreak can be caused by the joint action of different strains of E. coli (Dziva and Stevens, 2008; Nolan et al., 2013).
Types of vaccines A wide range of vaccines and vaccine strategies against APEC have been developed, including active and passive immunisation, the use of inactivated, live attenuated, recombinant and subunit vaccines, and immunisation against specific virulence factors. The vast majority of these approaches remain in the research phase (Yaguchi et al., 2009; Lynne et al., 2012; Nagano et al., 2012; La Ragione et al., 2013; Nolan et al., 2013).
Inactivated vaccines Inactivated vaccines consist of an antigenic phase to which an adjuvant that promotes an immune response is added. This results in the stimulation of a humoral immune response mediated by CD4+ T cells. The antigenic phase in E. coli vaccines can contain entire inactivated organisms (e.g. autogenous vaccines and some commercial vaccines) or part of their antigenic structures. Vaccines that contain the entire organism usually include a mixture of strains corresponding to the serotypes that are most commonly associated with colibacillosis outbreaks in poultry worldwide, such as O1, O2 and O78. As mentioned above, protection is provided against homologous strains; these vaccines are not fully effective in outbreaks caused by other APEC serovars. For this reason, it is common to autovaccinate against E. coli when the desired result is not obtained using commercial vaccines. Autogenous vaccines are inactivated vaccines developed using strains isolated from affected animals on a farm. These vaccines are thus extremely specific and require the prior isolation of the bacterium or bacteria involved. Moreover, tracking of the dynamics of the strains causing the infection over time is necessary to ensure that the vaccine remains effective.
Fimbriae (F antigen)
Flagellum (H antigen)
Figure 7. Major surface antigens (O, K, H and F) of E. coli (modified from Blanco et al., 2002).
Inactivated vaccines in which the antigen consists of antigenic structures of the bacteria of interest usually contain proteins (virulence factors) that are commonly associated with the pathogenicity of disease-causing APEC strains. Examples include the F1 fimbrial antigens and other adhesins, and the Iss outer membrane protein (Lynne et al., 2012). The advantage of these vaccines is that they confer cross-protection against different serotypes.
Live attenuated vaccines attenuated vaccines contain a live infectious agent, homologous to one which causes the disease, but whose virulence has been attenuated such that it induces long-lasting immunity to the homologous virulent agent without causing any secondary lesions in the vaccinated individual. Live vaccines allow the stimulation of cellular and humoral responses mediated by CD4+ and CD8+ T cells. To date, two live attenuated strains of E. coli have been described; both belong to serotype O78 and lack certain virulence factors, and thus can be safely used (Nagano et al., 2012; Fernandes Filho et al., 2013). Both have proven effective in the prevention of colibacillosis in poultry caused by strains of serotype O78 (Nagano et al., 2012; Fernandes Filho et al., 2013). Table 3 lists the avian colibacillosis vaccines that are currently commercially available.
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VACCINATION IN POULTRY
Table 2. Eimeria species of turkeys included in commercially available vaccines. SPECIES
Eimeria adenoides (Moore and Brown, 1951)
Eimeria dispersa (Tyzzer, 1929)
Eimeria gallopavonis (Hawkins, 1952)
Eimeria meleagrimitis (Tyzzer, 1929)
Site with lesions
Site of multiplication
• Caeca • Ileum and rectum down to the cloaca
• The whole duodenum, jejunum, ileum and rectum • Caeca are not affected
• Ileum • Rectum
• Jejunum • Duodenum and ileum may also be affected
Characteristic lesions in GI tract
• First, oedema and petechia • Later, massive fibrinous cores
• Usually mild lesions • Intestinal wall thickened and cream-coloured
• Thickened mucosa covered with fibrinous and necrotic material
• Segments of affected intestines appear dilated and filled with fluid, mucoid content
Other lesions
• Weight loss • Mortality 100 % under experimental conditions
• Weight loss • Mucoid faeces
• Mortality can occur
• Dehydration • Disturbed general condition • Reduced weight gain • Mortality may occur
Oocysts
• Small to medium sized • Oblong
• Large • Ovoid
• Large • Oblong
• Small to medium sized • Ovoid
Additional information
Lesions may be suggestive of histomonosis. In 1910 Eimeria were mistakenly described as the causative agent of the “blackhead disease”.
In contrast to most other Eimeria species of poultry, E. dispersa is not host specific, but can infect several other gallinaceous birds. The bobwhite quail (Colinus virginianus ) seems to be the natural host.
After infection of a flock, which will almost inevitably occur, dry litter will slow down the sporulation of oocysts. Top dressing the litter and keeping drinkers and feeders clean will further help to limit the spread of the parasite and to reduce the infection pressure, which will lead to less damage, since the damage caused by infection with coccidia is directly linked to the infection dose. Regarding coccidiosis, “complete house sterilisation is never complete” (McDougald and Fitz-Coy, 2008) and can only be considered as a mean to reduce the initial infection pressure.
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Especially in broilers and turkeys, prophylaxis of coccidiosis relies heavily on the use of anticoccidial feed additives. Several different compounds can be used for that purpose, which have different modes of action and act on different stages. Traditionally, polyether ionophore antimicrobials like salinomycin, monensin or lasalocid are differentiated from “chemical” compounds, a heterogeneous group, including diclarzuril, nicarbazine and robenidine, among others.
VACCINATION AGAINST pArASITIC DISEASES COCCIDIOSIS
50 µm
20 µm
Figure 8. Severe histopathological lesions due to Eimeria necatrix. Image courtesy of Dr H. L. Shivaprasad, California Animal Health and Food Safety Laboratory System.
Figure 9. Histopathological lesions with different stages of Eimeria necatrix. Image courtesy of Dr H. L. Shivaprasad, California Animal Health and Food Safety Laboratory System.
Figure 11. Opened small intestine with typical lesions due to Eimeria necatrix. Image courtesy of Dr H. L. Shivaprasad, California Animal Health and Food Safety Laboratory System.
Figure 12. Unopened caeca with typical lesions due to Eimeria tenella. Image courtesy of Dr H. L. Shivaprasad, California Animal Health and Food Safety Laboratory System.
When designing a control program using anticoccidials, several factors have to be taken into account: 1. Not all compounds are equally efficacious against all relevant Eimeria species. 2. Anticoccidials may be coccidiocidal (killing the parasitic stages they act on) or they may be coccidiostatic (merely stopping the development of parasites until they are withdrawn). 3. Many anticoccidials require a withdrawal time of several days before slaughter or before eggs for human consumption are produced. 4. Some compounds are toxic for the birds themselves, e.g. polyether ionophores have a very narrow therapeutic spectrum and, even at recommended
Figure 10. Unopened small intestine with typical lesions due to Eimeria necatrix. Image courtesy of Dr H. L. Shivaprasad, California Animal Health and Food Safety Laboratory System.
Figure 13. Opened caeca with typical lesions due to Eimeria tenella.
levels, can have a negative effect on weight gain in broilers. 5. Last and most importantly, after prolonged use of anticoccidials, coccidia become resistant. This has been observed for a long time and resistance to anticoccidial drugs is now regarded as ubiquitous. To slow down the further development and spread of resistances, the same anticoccidial is not given for a prolonged time (Fig. 14, single program), but anticoccidials are changed on a regular basis, either after a certain time (Fig. 15, rotation program), after each flock (Fig. 16, switch program) or between starter and grower feed (Fig. 17, shuttle or dual program) (Chapman, 2014).
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VACCINATION IN POULTRY
The HVT vaccine is provided either under the cell-associated or the cell-free form, which is lyophilised. The relatively fast growth and ease of production of HVT in chicken embryo fibroblast (CEF) culture are two important factors that have contributed to its wide use as recombinant vaccines. Among other advantages, HVT vaccines can be administered by the in ovo route 3–2 days before hatching or by the subcutaneous (SC) or intramuscular routes to day-old chicks. Also, HVT vaccine is well-known to be fully safe and poorly sensitive to interference with MDA when under the cell-associated form (Bublot et al., 2007). For all these reasons, it has long been proposed as a vector (Sondermeijer et al., 1993), first against IBD (Darteil et al., 1995; Tsukamoto, 2002; Perozo et al., 2009) and then against ND and AI (Heckert et al., 1996; Reddy et al., 1996; Rauw et al., 2010).
Vector vaccine
HVT has long been proposed as a vector, first against IBD, and then against ND and AI.
HVT-vectored vaccines against these three diseases are currently licensed and commercialised. Even in the presence of H5 MDA, HVT-H5 vaccines are able to protect against mortality and clinical signs after HPAIV homologous or heterologous challenge with the induction of a high H5 humoral response (Palya et al., 2012; Rauw et al., 2013). In addition, such vaccination was able to protect against challenge with two highly antigenically divergent H5N1 strains (Rauw et al., 2011). Herpesvirus-vectored AI vaccines can be applied in mass vaccination strategies.
Viral antigen First in vivo replication of live vector vaccine by targeted cells
CTL
CTL
Peptides
Cytokines CTL
APC
Priming: viral antigen capture and presentation by APCs
APC
- Th cells activation - Cytokine production - CTL and B activation
B Th
Th
CMI PRIMING (Th1)
HUMORAL PRIMING (Th2)
Antibodies Dying inoculated cell
Memory T cells
Th
Effective responses: - Ab production - CTL activity - Induction of memory immunity
Memory B cells
Figure 7. Principles of DNA and live vector vaccines. DNA and live vector vaccines are a promising new approach for the prevention and treatment of many diseases because of their ability to induce both humoral and cellular immune responses against pathogens. After inoculation into the host, they enter the cells, where the antigen is expressed and processed, and subsequently recognised by the immune system as in a natural infection.
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