Is Eimeria tenella the only species diagnosed in poultry coccidiosis?

On several occasions in this blog, we have talked about coccidiosis diagnosis, and we recently focused on the lesion scoring technique, which is certainly the most widely used method for diagnosing Eimeria tenella in the field. Let us carry out a brief review of all the posts published on this subject with a view to understanding how to make the most of each technique. 

Oocyst counts & morphological evaluation

Oocysts per gram of faeces (OPG) count and morphological identification are often wrongfully considered the gold standard technique for coccidiosis diagnosis.

Wrongfully because the presence of oocysts cannot be interpreted as an outbreak of coccidiosis, as Eimeria oocysts are ubiquitous.

Therefore, the significance of this finding must be weighed against the level of oocysts/gram first and then other indicators of disease, such as the presence of clinical signs in live animals, as well as macro- and microscopic lesions in the intestine at necropsy.

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Eimeria species involved in avian coccidiosis: Who claims 7 and who claims 9?

Avian coccidiosis is a costly intestinal disease caused by parasites of the Phylum Apicomplexa, genus Eimeria, which frequently affect poultry. Apart from the three best known Eimeria spp. (Eimeria acervulina, Eimeria maxima and Eimeria tenella), other species can also affect chickens, and their appearance is mostly related to the category of birds under consideration: long or short-lived birds. In this post we will review the most important posts published so far on this subject and we will try to shatter a myth: do Eimeria mivati and Eimeria hagani really exist?

Eimeria tenella grade 4 lesion: caecal wall greatly distended with blood or large caseous cores; faecal debris lacking or included in cores (according to Johnson and Reid, 1970).

Chickens are susceptible to seven Eimeria species: Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox and Eimeria tenella. Very often this is the start of many articles about coccidiosis, however many argue that another two species should be included in this list.

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Coccidiosis in poultry does not only come from Eimeria tenella and has started to affect more and more laying hens.

Eimeria tenella is by far the most widely detected species on farms when routine lesion scoring is performed. However, it is well known that most of the time Eimeria infections are multiple. On the other hand, during last decade the egg sector has probably undergone the biggest changes, with an ever-increasing percentage of cage-free laying hens, especially in Europe. 

Generally in layers and breeders we distinguish between caecal and intestinal coccidiosis. Caecal coccidiosis is due to Eimeria tenella  that is confined to the caecum and consists of the presence of hemorrhages on the outside or inside of the wall of the caecum.

This acute infection occurs most commonly in young chicks and is by far the most widely diagnosed in the field due to its typical lesions and location. For this reason, a common belief is that Eimeria tenella is the most prevalent all over the globe. In fact, macroscopic lesions are amongst the most pathognomonic with blood or typical molds in the caecum and common findings of bloody droppings in the litter.

Eimeria tenella lesion, coccidiosis in poultry
A common belief is that Eimeria tenella is the most prevalent all over the globe.

Continue reading Coccidiosis in poultry does not only come from Eimeria tenella and has started to affect more and more laying hens.

Eimeria tenella is probably the most diagnosed Eimeria on the planet, but what is the prevalence of the other Eimeria species that cause coccidiosis in poultry?

Eimeria tenella is by far the most widely detected species on farms when routine lesion scoring is performed. However, it is well known that Eimeria infections very seldom occur with one single species of Eimeria, most of the time they are multiple. Let’s investigate what are the most prevalent species and how multiple infections usually occur.

E-tenella-3rd-degree-lesion

As Eimeria tenella is probably the easiest species to detect by lesion scoring, a common belief is that this species is the most prevalent all over the globe. In fact, macroscopic lesions are amongst the most pathognomonic with blood or typical moulds in the caecum and common finding of bloody droppings in the litter.

Continue reading Eimeria tenella is probably the most diagnosed Eimeria on the planet, but what is the prevalence of the other Eimeria species that cause coccidiosis in poultry?

Eimeria species in long life-cycle birds: focus on Eimeria tenella

Avian coccidiosis is a common protozoal gastrointestinal parasitosis caused by the Eimeria species resulting in considerable economic losses in the poultry industry, especially in long life-cycle birds such as layers and breeders. In these high value birds, Eimeria species infection results in clinical or subclinical coccidiosis associated with increased mortality, decreased flock uniformity and a general rise in secondary pathologies subsequent to intestinal damage. Without any doubt, the best known and most widely diagnosed species is Eimeria tenella.

E-Tenella-23-Junio-AMicroscopic picture of the five Eimeria species included in EVALON®: Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria necatrix and Eimeria tenella.

Chickens are susceptible to seven Eimeria species, the most common species affecting long-life birds being Eimeria tenella, Eimeria necatrix, Eimeria brunetti, Eimeria acervulina and Eimeria maxima.

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