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[[Coccidia - Poultry]]
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== Introduction ==
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'''Pathogenesis'''
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Coccidiosis is a disease of poultry which is of worldwide importance, both economically and for animal welfare reasons. It is a disease of over-crowding and poor hygiene, hence it is prevalent in intensive chicken farming globally, however, it can affect birds in any facilities. Although outbreaks of the disease are not common, coccidia remians in most flocks as a subclinical disease, which in times of stress can establish into a clinical disease. Many commercial units now use prophylactic drugs in order to try and control the disease.
*7 important ''[[Eimeria spp.|Eimeria]]'' species
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*4 malabsorptive species
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There are&nbsp;7 important coccidia species in chickens, all which fall into the Eimeria genus.&nbsp;<br>There are 4 malabsorptive species, which range from low to moderate pathogenicity&nbsp;and 3 haemorrhagic species, which are all highly pathogenic. All seven species have different predilection sites in the alimentary system and cause unique pathological changes.
**''[[Eimeria spp.|Eimeria]] acervulina'' which is moderately pathogenic
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'''Epidemiology'''<br>Oocysts are ubiquitous and robust and can survive several months to several years in the environment, meaning it is almost impossible to keep buildings free from infection. Even with strong disinfection after every batch has gone, the new chicks will become infected by pecking the ground shortly after being placed in the poultry house.<br>The biotic potential is enormous and generation time is short, meaning infections can build up rapidly. Immuntiy however, develops slowly and certain species of Eimeria will inflict a faster immune response and longer lasting immunity than others.
**''[[Eimeria spp.|Eimeria]] maxima'' which is moderately pathogenic
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**''[[Eimeria spp.|Eimeria]] mitis'' which has low pathogenicity
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**''[[Eimeria spp.|Eimeria]] praecox'' which has low pathogenicity
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*3 haemorrhagic species
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**''[[Eimeria spp.|Eimeria]] tenella''
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**''[[Eimeria spp.|Eimeria]] necatrix''
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**''[[Eimeria spp.|Eimeria]] brunetti''
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**All highly pathogenic
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**Form large sub-epithelial second generation schizonts at the base of intestinal crypts
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**Deep eruptions form when cells rupture to release merozoites
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**Destruction of crypt stem cells and marked haemorrhage
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**Blood stained faeces
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**High morbidity and high mortality
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'''Diagnosis'''
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*Post-mortem diagnosis of lesion severity
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**Region of intestine affected
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**Appearance of lesion
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**Presence or absence of haemorrhage
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**Size of schizonts and oocysts found in mucosal scrapings
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*''[[Eimeria spp.|Eimeria]] acervulina''
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== Clinical Signs ==
**Proximal gut
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**Thickening of walls
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**'White ladder lesions' produced by dense foci of gamonts and oocysts
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**Watery exudate
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*''[[Eimeria spp.|Eimeria]] maxima''
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Depends on the pathogenicity of the coccidia involved and the concurrent health status of the chicken.
**Mid-gut
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**Thickening of walls
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**Pink exudate
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*''[[Eimeria spp.|Eimeria]] tenella''
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With any infection will usually see depression, general malaise, reluctance to eat, weight loss and sudden death. Often the only sign will be sudden death in severe cases. In most cases of coccidiosis, there will be&nbsp;a watery or mucoid diarrhoea which will often be blood-tinged.
**Swollen [[Caecum - Anatomy & Physiology|caeca]]
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**Thickening of wall
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**Dark colouring containing a core of necrotic tissue and blood
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*Lesion scoring is the best method of diagnosing the severity of the lesions and therefore the causative ''[[Eimeria spp.|Eimeria]]'' species
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*''[[Eimeria spp.|Eimeria]] necatrix''
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**Mid-gut
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**Ballooning of wall
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**White spots and petechiae forming 'salt and pepper' lesions
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**Haemorrhage into lumen
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'''Immunity'''
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== Diagnosis ==
*Different ''[[Eimeria spp.|Eimeria]]'' species produce different levels of protective immunity
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**''E.maxima'' -> ''E.brunetti'' and ''E.acervulina'' -> ''E.tenella'' and ''E.necatrix''
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*There is no cross immunity between species
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As clinical signs can vary, the most useful diagnostic tool is&nbsp;a necropsy&nbsp;on a recently dead bird that has been sacrificed for this purpose. A bird that has died naturally and has been dead for over one hour will make post mortem examination difficult due to post mortem changes in the intestinal mucosa.
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*There is very little passive immunity
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The presence of coccidia and mild lesions are present in most young birds between the age of 3- 6 weeks of age but do not mean the bird has clinical coccidiosis. The severity of the lesions should determine a diagnosis of coccidiosis being made.
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*Evokes a cell-mediated response
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Lesions and their location vary depending on which Eimeria genus is causing the disease:
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*All ages of poultry are susceptible
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''[[Eimeria spp.|Eimeria]] acervulina:'' proximal gut, thickened walls, 'white ladder lesions' produced by dense foci of gamonts and oocysts and a watery exudate are likely to be found in this case.<br>''[[Eimeria spp.|Eimeria]] maxima: ''mid-gut, thickened walls and a pink exudate with this coccidia.<br>''[[Eimeria spp.|Eimeria]] tenella: s''wollen [[Caecum - Anatomy & Physiology|caeca]], thickened intestinal walls, dark colouring of damaged intestine&nbsp;containing a core of necrotic tissue and blood.<br>''[[Eimeria spp.|Eimeria]] necatrix: ''mid-gut, the wall will show 'ballooning', white spots and petechiae form characteristic&nbsp;'salt and pepper' lesions and there will be haemorrhage into lumen.
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'''Epidemiology'''
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As well is post mortem examination of gross lesions, scrapings of the mucosa should be taken for examination under the microscope. The number of&nbsp;oocysts should be counted and examined for shape and size to aid identification.
*Oocysts are ubiquitous and robust
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**Able to survive several months to years
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*It is impossible to keep buildings free from infection
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**Chicks become infected by pecking the ground shortly after being placed in the poultry house
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*Biotic potential is enormous
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**Generation time is short
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**Massive infections can build up rapidly
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*Immunity develops relatively slowly
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== Treatment and Control ==
**With high stocking densities the situation is explosive
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'''Control'''
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Prevention of this disease is much more valuable than treatment should an outbreak occur. In commercial poultry farms, many measures are undertaken to control the disease. Intensive poultry production is largely dependent on the use of anticoccidial drugs, as well as strict hygiene controls.
*Chemical
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**Intensive poultry production is largely dependent on the use of anticoccidial drugs
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**For more information see [[Anti-Protozoal Drugs|here]]
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*[[Vaccines|Vaccines]]
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For more information see [[Anti-Protozoal Drugs|here]]
**Paracox
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***Multivalent attenuated [[Vaccines#What antigen(s) do we use in the vaccine?|live vaccine]] for replacement layers and broilers
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***Contains 7 live strains of ''[[Eimeria spp.|Eimeria]]''
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***Lack the most pathogenic life cycle stage making the prepatent period shorter
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***Known as '''precocious''' strains
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***Chicks [[Vaccines|vaccinated]] on a single occasion when 1-9 days old through oocyst suspension in the feed or water
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***[[Vaccines|Vaccinated]] birds have sub-optimal growth rates so is not used for broilers
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**Paracox 5
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***Contains 5 strains of the most pathogenic ''[[Eimeria spp.|Eimeria]]''
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***Used for broilers
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***Sprayed onto the first feed offered to new batches of chicks
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*Integrated control
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'''Layers<br>[[Vaccines|Vaccines]]&nbsp;are used for laying hens as these have a longer life span than broilers so will develop an immunity.
**Careful management is needed so in-feed prophylaxis and [[Vaccines|vaccination]] do not fail
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**Remove litter and thoroughly clean houses in between crops
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***Optimum turn-around time is 10 days
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**Use the lowest stocking density which is compatible with economic production
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**Water bowls, roofs and walls should be well maintained to prevent litter becoming damp
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**Stress factors should be avoided and adequate nutrition provided
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==Literature Search==
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Paracox 7&nbsp;vaccine is a multivalent attenuated [[Vaccines#What_antigen.28s.29_do_we_use_in_the_vaccine.3F|live vaccine]] for replacement layers, which contains 7 live strains of ''[[Eimeria spp.|Eimeria]]. ''These live strains lack the most pathogenic life cycle stage making the prepatent period shorter. These are known as '''precocious''' strains.
[[File:CABI logo.jpg|left|90px]]
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Chicks are&nbsp;[[Vaccines|vaccinated]] on a single occasion when they are&nbsp;1-9 days old through oocyst suspension in the feed or water. For a short period, v[[Vaccines|accinated]] birds have sub-optimal growth rates so&nbsp;this is why they are not used for&nbsp;broilers.
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Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation).
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<br><br><br>  
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[http://www.cabi.org/cabdirect/FullTextPDF/2009/20093257328.pdf '''Coccidiosis in poultry: review on diagnosis, control, prevention and interaction with overall gut health.''' Gussem, M. de; World's Poultry Science Association (WPSA), Beekbergen, Netherlands, World Poultry Science Association, Proceedings of the 16th European Symposium on Poultry Nutrition, Strasbourg, France, 26-30 August, 2007, 2007, pp 253-261, 36 ref. - '''Full Text Article''']
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'''Broilers<br>'''As broilers have a much shorted life span than laying hens, vaccination is not the most economical option in this case.
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The continuous use of a single anti-coccidial&nbsp;drug from day one of life through to slaughter is used. As the broiler does not live for long, immunity would not have time to develop so providing anti-coccidial drugs on a constant basis controls the disease well.
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Some producers will use the 'dual' or 'shuttle' method, which follows the same basis of using anti-coccidials constantly, but two or three different drugs are given throughout the chickens' life; e.g. one drug in the starter, a different one in the grower and another in the finisher. This is thought to control coccidia more efficiently as it will reduce the resistance build up to one drug.
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A vaccine called Paracox 5, which contains 5 strains of the most pathogenic ''[[Eimeria spp.|Eimeria]]&nbsp;''can be used for broilers. It is sprayed onto the first feed offered to new batches of chicks and will provide integrated control. Careful management throughout is required so in-feed prophylaxis and [[Vaccines|vaccination]] do not fail.
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Strict hygiene measures in both layers and broilers is needed to control coccidia. Litter should be removed and the housing thoroughly disinfected between crops. The ideal turnaround should be no less than 10 days, but this often is impracticable for economic reasons. Over-crowding exacerbates coccidiosis, so the lowest stocking density which is compatible with economic production should be used.<br>Water bowls, roofs and walls should be well maintained to prevent litter becoming damp and sttress factors should be avoided and adequate nutrition provided.
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Should an outbreak occur, treatment with anti-coccidial drugs, such as sulphonamides, diclazuril, decoquinate and monensin should be administered into the drinking water with immediate effect. The farms' control measures should then be examined and reviewed.
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== References ==
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Fox, M and Jacobs, D. (2007) Parasitology Study Guide Part 1: Ectoparasites Royal Veterinary College <br>Jordan, F, Pattison, M, Alexander, D, Faragher, T, (1999) Poultry Diesease (Fifth edition) W.B. Saunders<br>Merck &amp; Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial<br>Randell, C.J, (1985) Disease of the Domestic Fowl and Turkey, Wolfe Medical Publication Ltd<br>Saif, Y.M, (2008) Disease of Poultry (Twelfth edition) Blackwell Publishing<br>
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== Literature Search ==
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[[Image:CABI logo.jpg|left|90px]]
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<br>Use these links to find recent scientific publications via CAB Abstracts (log in required unless accessing from a subscribing organisation). <br><br><br>[http://www.cabi.org/cabdirect/FullTextPDF/2009/20093257328.pdf '''Coccidiosis in poultry: review on diagnosis, control, prevention and interaction with overall gut health.''' Gussem, M. de; World's Poultry Science Association (WPSA), Beekbergen, Netherlands, World Poultry Science Association, Proceedings of the 16th European Symposium on Poultry Nutrition, Strasbourg, France, 26-30 August, 2007, 2007, pp 253-261, 36 ref. - '''Full Text Article''']  
    
== Test yourself with the Coccidia Flashcards  ==
 
== Test yourself with the Coccidia Flashcards  ==
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[[Coccidia Flashcards|Coccidia Flashcards]]  
 
[[Coccidia Flashcards|Coccidia Flashcards]]  
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[[Category:Coccidia]] [[Category:Alimentary_Diseases - Birds]] [[Category:To_Do_-_Kate]]
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[[Category:Coccidia]] [[Category:Alimentary_Diseases_-_Birds]] [[Category:To_Do_-_Review]]
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