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== Introduction  ==

== Introduction  ==

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, [[:Category:Coccidia|coccidia]] remains 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 to control the disease.  

Seven species infect turkeys – the big three of concern are ''Eimeria meleagrimitis, E. adenoeides,'' and ''E. gallapovonis''.

 

Currently 13 species of coccidia have been reported in ducks but only certain species have been researched. ''Eimeria, Wenyonella'' or ''Tyzzeria'' genuses are found in wild and farmed birds.  

 

There are three main species of coccidia in pheasants, all three of which fall into the ''Eimeria'' genus.  

There are 7 important coccidia species in chickens, all which falle [[Eimeria spp.|''Eimeria'']] genus. <br>There are 4 '''malabsorptive''' species, which range from low to moderate pathogenicity 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.  

In Geese, there are two strains ''Eimeria truncata'' and ''E. anseris'', which are of most pathogenic importance, with the latter causing intestinal disease and ''E. truncata'' causing renal coccidiosis.  

'''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. Immunity however, develops slowly and certain species of ''Eimeria'' will inflict a faster immune response and longer lasting immunity than others.  

Coccidia have a direct life cycle, with a one week prepatent period. After oocysts are ingested, sporozoites are released which penetrate the intestinal epithelium and 2 asexual phases of multiplication called schizogony occur followed by a phase of sexual multiplication called gametogony. The zygote develops into an oocyst which is then shed in the faeces. An oocyst measures around 20-30μm and for each oocyst ingested, thousands are shed. The life cycle is '''self-limiting '''and organisms from a single infection go through the sequence of developmental stages synchronously. Organisms leave the body simultaneously as oocysts. Oocysts are only infective once they have sporulated and sporulation requires warmth, moisture and oxygen; this will take around 2-3 days in broiler houses.  

== Clinical Signs  ==

== Clinical Signs  ==

Depends on the pathogenicity of the coccidia involved and the concurrent health status of the chicken.  

Depends on the pathogenicity of the coccidia involved and the concurrent health status of the chicken.  

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 a watery or mucoid diarrhoea which will often be blood-tinged.  

In most poultry animals, severe enteritis is the main clinical symptom. Haemorrhagic diarrhoea is seen with the most pathological strains of the disease along with mucoid discharge. Weight loss, general malaise, reduced appetite and depression are other common signs. Sudden death can occur, often in younger birds. Morbidity is usually very high but mortality is variable. In geese, renal coccidiosis can occur and signs include severe depression such as reduced appetite and huddling, emaciation and diarrhoea. Mortality rates are high, however, birds that recover from the infection remain strongly resistant to it for life.

 

== Diagnosis  ==

== Diagnosis  ==

As clinical signs can vary, the most useful diagnostic tool is a necropsy 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.  

Clinical signs and history are usually enough to make a presumptive diagnosis. However, as clinical signs can vary, the most useful diagnostic tool is a necropsy 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. Observation of caseous core lesions in the caecum and sloughing of the intestinal walls will strengthen a presumptive diagnosis. A sample of mucosa should be taken for examination under the microscope in order to identify oocysts, which will confirm the diagnosis. Specific identification of genus of coccidia is not required as treatment is the same for all.

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.  

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.  

== Treatment and Control  ==

== Treatment and Control  ==

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.  

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.  

== References  ==

== References  ==

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>

Fox, M and Jacobs, D. (2007) '''Parasitology Study Guide Part 1: Ectoparasites''''' Royal Veterinary College''

 

 

Jordan, F, Pattison, M, Alexander, D, Faragher, T, (1999) '''Poultry Diesease''' (Fifth edition) ''W.B. Saunders''

 

Randell, C.J, (1985) '''Disease of the Domestic Fowl and Turkey''', ''Wolfe Medical Publication Ltd''

 

Saif, Y.M, (2008) '''Disease of Poultry''' (Twelfth edition) ''Blackwell Publishing''

 

[[Category:Alimentary_Diseases_-_Birds]] [[Category:Expert_Review]]

[[Category:Coccidia]] [[Category:Avian_Parasites]] [[Category:Alimentary Diseases - Birds]][[Category:Expert_Review]]