7International Poultry Production • Volume 25 Number 2

Respiratory diseases of turkeysare currently the most com-monly diagnosed group of

health disorders in intensive animalfarming. They often occur as poly-etiological disease entities develop-ing due to viral, fungal and bacterialfactors alike. What is more, notunimportant in the course of com-plex disease syndromes are ele-ments of production technology,which are sometimes capable ofinducing or aggravating the courseof the disease.

by Albert Nakielski, Veterinary Surgeon,

AviPoint Veterinary Clinic,Olsztyn, Poland.www.biopoint.eu

Currently reported field ‘multi-infections’ of turkeys pose a hugechallenge for veterinarians takingcare of these animals. Isolation ofhighly resistant strains of bacteria,lack of new effective pharmacologi-cal resources, antibiotic residues indrinking lines, animal tissues, pro-longed withdrawal periods, legalregulations and public opinionpressing in favour of food produc-tion without the use of antibioticspose further challenges for veteri-narians and specialists in poultrydiseases.

To meet these expectations andrestrictions we should seek moreand more effective tools whichcould be introduced into everydayuse. One of them is the use of nat-ural plant extracts showing anti-bacterial properties.

The avian respiratory system

The avian respiratory system isexceptional in terms of anatomyand its functions. It is composed ofthe nasal cavity, anterior larynx, trachea and syrinx, a vocal organ,which is comprised of the last tracheal rings and first sections ofthe respiratory tract.

The next element are the lungs, inthe flesh of which the primarybronchus enters, branching off intosecondary dorsal and ventralbronchi. These, in turn, are inter-connected by parabronchi, whichare the proper respiratory compo-nent of the lung parenchyma.

Another vital and unique elementof the respiratory tract are air sacs.They are thin-walled, membranousprotrusions of the primary bronchi.Their functions are manifold, butthe most important ones involvebeing part of an effective gasexchange, bone pneumatisation andthermoregulation. This last role iscrucial when extremely high temperatures prevail, as birds having

no sweat glands primarily exhalethe excess heat through the respira-tory system.

Conversely, during low tempera-tures the air sacs constitute an insu-lating air blanket for importantinternal organs. In addition, theyreduce the specific weight of thebirds' body (for flying and diving),facilitate defecation, enhance theirsound strength and help in layingeggs.

On the other hand, the aboveanatomical structure of the respira-tory system of birds makes theseanimals more prone to develop anumber of health disorders. Highhumidity, optimal temperature andhigh oxygen content within the res-piratory tract are perfect conditionsfor the development of pathogens.

Colibacillosis of therespiratory system

Colibacillosis is caused by one ofthe most commonly isolated Gram-negative ciliated bacteria of theEscherichia coli genus. Due to thecosmopolitan nature of the bacte-ria, large variety of its pathogenicserotypes, ability to produce toxins,mobility, diverse routes of infection,easiness of mucosal colonisationand very rapid multiplication of thebacteria (logarithmic increase every18 minutes), it currently plays themost important role in the pathol-ogy of the respiratory bacterial dis-eases.

As with other bacterial respiratory

infections of turkeys, inducing factors are an essential part in thedevelopment of colibacillosis.

Typically, the clinical form of thedisease occurs as a chronic respira-tory disease (CRD). More and morefrequently recorded are infectionscaused by highly resistant strains ofEscherichia coli (APEC), which posea huge challenge when starting anantimicrobial therapy directedagainst these pathogens.

In the case of turkeys for fatten-ing, in the course of CRD, theutmost importance is ascribed toisolates which are members of O1,O1, O78 serogroups. In the course ofthe disease the following occur:cough, crackles, sneezing, a series ofnon-specific symptoms andincreased mortality in the flock.

The anatomopathological changesregarding the respiratory systeminclude fibrinous-purulent inflam-mation of air sacs, hyperaemia,swelling and hypertrophy of lungtissue. Clinically manifested diseaseis usually diagnosed after 3-4 weeksof life, the intensity of the diseaseand the percentage of daily fallsdepends on the occurrence of pre-disposing factors and associatedinfections.

Pasteurellosis

Pasteurellosis is a disease caused byinfection of a Gram-negative, non-motile Pasteurella multocida bacil-lus (serotype 1 P. multocida subsp.

Plant extract applicationfor controlling respiratorydiseases in turkeys

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Fibrinous inflammation of the dorsal air sacs in an eight-week-old turkey.

Strong congestion of the trachea mucous membrane in a nine-week-oldturkey.

multocida). This bacterium isregarded as a commensal colonisingthe mucous membranes of theupper respiratory tract and rostralcavity and its clinical significance ismost often reflected as a consequence of viral diseases orchronic immunosuppression.The clinical form of the disease is

diagnosed in turkeys usuallybetween 8- 14 weeks of life and itsintensity depends on a number offactors ranging from the environ-mental conditions, the concentra-tion of birds, vitamin deficiencies,technological stress caused by thepresence of vectors (rodents), end-ing with the immunological statusof the animals. The course of the infection

depends on the virulence of thepathogen, although farmed animalsare in most cases diagnosed withperacute and acute form of pas-teurellosis. In the first case, despite the rapid

course of the disease and the highmortality rate of the birds, there areno prodromal symptoms and theonly characteristic change discov-ered during autopsy are petechialand ecchymotic haemorrhages onthe cardiac muscle and pancreas.The clinical picture for the acute

form is non-specific and includesapathy, dejection of birds, loweringof the wings, drop in food consumption, ruffled feathers,increased thirst, sometimes rapidbreathing, gasping or slight

diarrhoea. Due to the septicaemicnature of the disease in the twoabove forms, during the diagnosticsection strong inflammatory lesionsof the pulmonary tissue can beobserved, called fibrinonecroticpneumonia.

Ornithobacteriosis – respiratory form

The aetiological agent of ornitho-bacteriosis are pleomorphic, non-motile, Gram-negative Ornitho-bacterium rhinotracheale bacillicomprising 18 serotypes (A-R).Beside Escherichia coli, it is now

one of the most commonly isolatedbacteria in the course of chronicinfections of the respiratory tract ofturkeys. Due to the possibility of infection

of birds by both the vertical andhorizontal way, and in particular byaerosols and through direct contactof birds, the disease has been classi-fied as one of the most infectiousbacterial diseases of the respiratorytract of turkeys. As with previously described

types of diseases, an important factor in the development andcourse of ornithobacteriosis is thepresence of predisposing factors(for example inadequate productiontechnology, deficient diet, concur-rent bacterial, viral, fungal co-infections). The disease affects birds of all

ages and is manifested mainly by

disorders in the functioning of therespiratory system. These includecoughing, crackles, shortness ofbreath, serous nasal discharge. Inaddition, there has been a swellingof the infraorbital sinuses, apathy,dejection, sudden decrease inappetite and water consumption.During diagnostic section, unilat-

eral or bilateral serous-fibrinous orfibrinous-purulent pneumonia andair sacs inflammation come to thefore. Additionally, swelling and conges-

tion of the lung tissue, severe fibrosis of the dorsal surface of thelungs and the presence of exudatethe texture and colour of yoghurtcan be observed. The mortality ofbirds in the farming environmentdepends on the occurrence of pre-disposing factors and associatedinfections and most often it fluctu-ates between 5-30%.

Bordetellosis

Bordetellosis is a highly contagiousdisease of the upper respiratorytract of turkeys caused by Gram-negative aerobic bacteriumBordetella avium.Distinguishing features of this

bacterium are: high tropism for cili-ated epithelium of the respiratorytract, the capacity of production oftoxins (osteotoxin, dermonecrotictoxin, cytotoxin, endotoxin) andimmunosuppressive activity. In young turkeys (2-4 weeks old),

the disease is highly contagious andsignificant lesions developing in theupper respiratory tract quicklyspread throughout the flock.The morbidity can reach 100% of

birds, and the mortality fluctuatesbelow 5%. Watery mucous andmucous-fibrous discharge fromnares and conjunctival sac, sub-mandibular oedema, dyspnoea,crackles, coughing and eye rubbingcan be observed in the infectedbirds.Macroscopic lesions include the

dorsal-ventral flattening of the tracheal rings, congestion of the trachea mucous membrane, distor-tion of turbinates and the accumu-lation of large amounts of mucuswith fragments of shed epitheliumand fibrin within the above organs.

Other bacterial infections

Clinically, infections with bacteriaof the Mycoplasma spp. genus alsohave a very important role in thehealth of the respiratory tract ofturkeys. A broad immunotherapy ofparental flocks and the eliminationof seropositive flocks led to anextremely rare occurrence ofmycoplasma in turkey flocks for fattening.In addition to the bacteria show-

ing a direct predilection for the respiratory tract of birds, in thecourse of poly-aetiological diseasesyndromes, also isolated are addi-tional bacteria of the Staphylococ-cus, Streptococcus and Klebsiellagenus.They belong to the saprophytic

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International Poultry Production • Volume 25 Number 2 9

Petechial haemorrhages myo-cardium in a 10-week-old turkey.

Fibrinonecrotic pneumonia in a 10-week-old turkey.

Fig. 1. Susceptibility zones of E. coli to a given active substance.

Fig. 2. Susceptibility zones of Klebsiella spp to a given active substance.

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1 Concentrated garlic extract2 Aqueous garlic extract3 Ajoene4 Mint essential oil5 Eucalyptus essential oil6 Pine essential oil7 Carvacrol8 Carvacrol 5%9 Carvacrol 6%10 Carvacrol 7%11 Thymol 5%12 Thymol 6%13 Thymol 7%

n Trachea, 9 weeks n Lungs, 3.5 weeks

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n Trachea, 9 weeks n Lungs, 3.5 weeks

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1 Concentrated garlic extract2 Ajoene3 Mint essential oil4 Eucalyptus essential oil5 Carvacrol6 Carvacrol 5%7 Carvacrol 6%8 Carvacrol 7%9 Thymol 5%10 Thymol 6%11 Thymol 7%

Zone

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microflora of birds, although withpersistent inappropriate technologi-cal conditions in the breeding facili-ties, the lack of proper hygiene ornon-compliance with the rules ofbiosafety, the abovementionedgroups of bacteria may pose anadditional threat to the respiratorysystem of birds. In case of complex bacterial infec-

tions, the infected flock most oftenshows symptoms of dyspnoea,coughing, sneezing, discharge fromnose and conjunctival sac, swolleninfraorbital sinuses and apathy. Post-mortem lesions include most

often serous-fibrinous inflammationof the air sacs, lung congestion andoedema and catarrhal inflammationof the trachea mucous membrane.The occurrence of opportunistic

infections enforces medical treat-ments exhibiting a broad spectrumof activity, which in the long term,results in the emergence of bacteriaresistant to commonly used antibi-otics.

The in vitro effects of naturalherb extracts

‘Multi-infections’ that occur underfield conditions are extremely diffi-cult to control with the use ofantibiotics or chemotherapeuticagents and, therefore, alternativemethods to facilitate the fightagainst common bacteria aresearched for. Great emphasis is puton the insulation and the use of

active substances contained inplants. Subject to intense researchare garlic, oregano, common thyme,field mint and eucalyptus globulus,from which dozens of active sub-stances exhibiting antibacterialeffect can be isolated. For example, garlic (allium

sativum) has in its compositiondozens of chemical compoundswhich, when properly acquired, canprove to be extremely effective infighting pathogens present onfarms. Some of the compounds(Allicin, Ajoene, diallyl disulphideand their derivatives) are determi-nants for antimicrobial properties. These compounds have the ability

to easily penetrate cell membranesof micro-organisms. Inside the cell,they merge with cellular enzymeswhich results in the blockage of thelatter.The inhibition of the enzymatic

processes results in disruption ofthe cell membrane function andbasic metabolic pathways and eventually in the death of the bac-terial cell. Considering the definedframework, the results presented inFigs 1-4 include only selected stud-ies done in the biggest number of repetitions. All published resultswere obtained in the course of theauthor's own tests and are his prop-erty. The tested active substances were

obtained in laboratory conditionswhile maintaining strict parametersand control processes involvingproper temperature adjusted in thecourse of the extraction process;

proper mixing speed adapted to thetype of raw material; the use ofadequate solvents for a variety ofextraction processes; matching timeintervals in the process of activity

assessment; building equipmentwhich enabled the recovery of themaximum amount of active sub-stance, and a packaging process toensure product stability.The pathogens used in the tests

were the bacteria isolated duringthe course of field diseases, in particular, the bacteria which showlow susceptibility to antibiotics andchemotherapeutic agents. In viewof obtaining promising results of thein vitro tests, tests with the use ofnatural extracts of herbs, essentialoils, pure active substances and mix-tures of the above are continued. Currently, work is being carried

out on the possibility of multiplyingthe concentration of the active sub-stance in the test samples. In the interpretation of the

presented results we should con-sider the fact that the raw materialis a mixture of natural ingredientsextracted from plants, thus theaccumulating mechanisms of actionare not fully known and repeatabil-ity of results may vary, dependingon the type and characteristics ofthe tested pathogen. Apart from this, every new tool

which helps to maintain the healthof the birds at an appropriate level,to support drug therapy or reducethe number of antibiotics usedbecomes extremely valuable. In the near future, phytobiotics,

while used in an appropriate man-ner, may prove to be one of the keyelements in the control of bacterialinfections in poultry production. n

International Poultry Production • Volume 25 Number 2 11

Different stages of unilateral fibrinous-purulent pneumonia in 11-week-old turkeys.

Fig. 4. Susceptibility zones of Staphylococcus aureus to a given active substance.

Fig. 3. Susceptibility zones of Enterococcus spp to a given active substance.

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1 Concentrated garlic extract2 Ajoene3 Eucalyptus essential oil4 Carvacrol5 Carvacrol 5%6 Carvacrol 6%7 Carvacrol 7%8 Thymol 5%9 Thymol 6%10 Thymol 7%

n Lungs, 13-week-old turkeys

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n Lungs, turkey

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1 Concentrated garlic extract2 Ajoene3 Eucalyptus essential oil4 Pine essential oil5 Carvacrol6 Carvacrol 5%7 Carvacrol 6%8 zzCarvacrol 7%9 Thymol 5%10 Thymol 6%11 Thymol 7%