Tag Archives: Coccidiosis in poultry

Anticoccidial Eimeria vaccines for poultry: where are we coming from and what is next? (Part II)

Live Eimeria vaccines have been widely used in poultry for more than 50 years now and we already described the differences among each other in a previous post (Part I). Since the 80s, attempts to develop next-generation recombinant coccidiosis vaccines have led to the identification of several candidate antigens (Blake et al. 2017). In spite of this, no recombinant Eimeria vaccine has been brought to market so far. So has anything new come to market since the 1950’s?

The reality is that nothing more than classic live Eimeria vaccines has been developed since the 1950s when the first coccidiosis vaccine reached the market. At first glance, if we think about all the other vaccines that have been brought to market in the meantime – both viral and bacterial -, and given that recombinant vaccines have been available for almost a decade now, it seems that research in the field of Eimeria vaccines has failed to keep pace.

Of course, this is not true and there has recently been one important step forward in the field of coccidiosis vaccines. In fact, HIPRA was the first company in the world to introduce the concept of immunomodulation in a live vaccine and more specifically an Eimeria live vaccine: EVALON®. So why use an immunomodulator for a live coccidiosis vaccine?

The reason is very simple: in order to survive, the Eimeria parasite fights back. In fact, it has evasion mechanisms that are able to play with immunity and, in this way, it is able to elicit a type of immunity that is not protective and effective (Jang 2011, Schmid 2014, Miska 2013).

Using immunomodulation, we use an adjuvant that make the vaccine work better, as this adjuvant triggers the type of immunity (cell-mediated) that is important for a protective immune response against Eimeria.

Specifically, the action of the adjuvant used in EVALON®’s HIPRAMUNE®T leads the immune response towards more effective immune mechanisms: the Th1 and Th2 responses need to be balanced and this is what the immunomodulator does. Results obtained from experimental trials indicate that HIPRAMUNE®T is able to increase the level of Th1 cytokines, as indicated by the results obtained for IL-2. Regarding IFN-gamma, statistically significantly higher levels were detected on different days both in the mucosa and Peyer’s patches. In contrast, levels of IL-4 and IL-10 were equal or lower when the group receiving EVALON® plus HIPRAMUNE®T was compared to the group receiving EVALON® alone. These results confirm the ability of HIPRAMUNE®T to stimulate a cellular immune response. It is therefore hypothesized that EVALON®, when administered together with HIPRAMUNE®T, is able to polarize the immune response towards a Th1 response.

Moreover, we have seen that HIPRAMUNE®T’s immunomodulator is also able to balance the Th1 and Th2 responses throughout almost the whole of the birds’ lives. In fact, in the duration of immunity trial we saw protection for up to 60 weeks after vaccination.

Coccidiosis vaccines using live Eimeria parasites are surely an effective alternative to anticoccidials. They are able to elicit a robust protective immunity after ingestion and re-cycling of the vaccine oocysts in the litter. However, very often this re-cycling can be hindered by several factors: dry conditions of the litter, low densities or production facilities (e.g. aviary systems, slats, etc…). It is exactly under these ever-increasing circumstances that the presence of an immunomodulator is of paramount importance as it can drive the development of the immunity towards a cell-mediated one even when the correct replication of the vaccine cannot take place completely.


Blake D.P., Pastor-Fernández I., Nolan M.J., Tomley F. (2017). Recombinant anticoccidial vaccines – a cup half full? Infection, Genetics and Evolution Nov; 55: 358-365.

Jang S.I., Lillehoj H.S., Lee S.H., Kim D.K., Pagès M., Hong Y.H., Min W., Lillehoj E.P. (2011). Distinct immunoregulatory properties of macrophage migration inhibitory factors encoded by Eimeria parasites and their chicken host. Vaccine Nov 8; 29 (48): 8998-9004.

Miska K.B., Kim S., Fetterer R.H., Dalloul R.A., Jenkins M.C. (2013). Macrophage migration inhibitory factor (MIF) of the protozoan parasite Eimeria influences the components of the immune system of its host, the chicken. Parasitol Res. May; 112(5): 1935-44.

Schmid M. , Heitlinger E. , Spork S. , Mollenkopf H.-J. , Lucius R. and Gupta N. (2014). Eimeria falciformis infection of the mouse caecum identifies opposing roles of IFNƳ-regulated host pathways for the parasite development. Mucosal Immunology Dec 7; 969–982.


Anticoccidial Eimeria vaccines for poultry: where are we coming from and what is next? (Part I)

Eimeria vaccines have been widely used in poultry since the early 1950’s and their advantages have been clearly shown. In spite of this, there are some differences between them -attenuation, composition, administration route-, but they all consist of live parasites that need to undergo two and sometimes three entire life cycles inside the host gut in order to trigger the immune system and subsequently establish full protective immunity.

There are both live non-attenuated and attenuated Eimeria vaccines on the market. Live non-attenuated vaccines consist of parasites that still maintain their natural virulence. Control of the development of adverse reactions (coccidiosis disease) is achieved by using low numbers of oocysts in vaccine preparations and in some cases even by the use of anticoccidials to control the excessive spread of vaccine strains. This strategy of “controlled exposure” allows protective immunity to develop before the contamination of litter with non-attenuated oocysts becomes severe.

Live attenuated Eimeria vaccines are specifically designed to generate an immune response whilst limiting the threat of possible adverse events. The most widely used attenuation system is the selection of strains by precocious development (Jeffers 1975), although attenuation via passages on embryonated eggs has also been used in E. tenella for some commercial live attenuated vaccines. There can therefore be different grades of attenuation due to the use of different attenuation processes.

As regards the composition of the Eimeria vaccine, this depends mainly on the category of birds for which the vaccine has been developed: broilers or breeders and layers. In spite of this, the main core of any vaccine should contain at least Eimeria acervulina, E. maxima and E. tenella, as these are species affecting all the birds. E. mitis and E. praecox have very fast biological life cycles within the host and this is closely related to their effect in the first weeks of production cycles. Thus, the impact of these Eimeria species is relevant for broilers but very limited for breeders and layers. In fact, the growth rate and weight gain within the first weeks of life in breeders and layers is quite irrelevant and even later on (from 3-4 weeks) the weight is monitored and the feed administered is restricted.

On the other hand, in the case of long life cycle birds such as breeders and layers, it is necessary to include E. necatrix and E. brunetti in the composition of Eimeria vaccines.

In addition, two species of Eimeria – in the past considered as separate species – are no longer included by the scientific community in the list of Eimeria species affecting Gallus gallus:

• Eimeria hagani – described only once by Levine P.P.in 1938;

• E. mivati, which appeared to be a mixture of E. mitis and E. acervulina (M. W. Shirley et al. 1983, V. Vrba et al. 2011).

However, both species are still present in a commercial vaccine registered on the American Continent.

Finally, regarding administration methods, a number of different ones have been developed for live Eimeria vaccines. The first ones included:

Drinking water: the best equipment to be used are bell-type drinkers. Usually one drinker is required for 100-150 chicks. In some cases, even pipeline systems have been used, but they are not suitable. In fact, when pipeline nipple drinkers are used, the risk is always that the vaccinal oocysts, due to their weight, become trapped in some angles of the line or in the biofilm that usually forms all along the lines.

On-feed spray: it should be pointed out that temperatures on farms are high on day 0, thus the time from vaccination to ingestion of feed becomes crucial. If this time is too long, vaccine oocysts may die from desiccation before the chicks can ingest them;

Eye drops: this is an individual method that can be very accurate, but due to the need for skilled labour it has fallen out of use, although it is still used in a few countries.

More recently:

Oral Gel/ Rain Gel: another delivery method is the incorporation of vaccine in a coloured gel that is placed in chick trays at the hatchery or on feed trays in the poultry house immediately after placement. However, this method can lead to non-uniform distribution of the oocysts inside the gel and consequently uneven intake of the vaccine.

In-ovo injection of sporulated oocysts into 18-day-old embryonated eggs. In-ovo administration has several distinct advantages, including the increased accuracy and repeatability of vaccine delivery. However, for this route of administration, a specific in-ovo machine adapted to deliver oocysts into the amniotic cavity of embryos is needed.

Coarse spray administration of 1-day-old chicks is probably the most common method and consists of spraying the vaccine over the chicks’ trays either at the hatchery or at farm level. The oocysts are suspended in a coloured dye (like the light purple used in HIPRACOX® & EVALON®) that has the dual advantage of allowing hatcheries to evaluate visually the success of the procedure and stimulating the chicks to take up the vaccine by preening themselves and pecking each other. In addition, HIPRACOX® & EVALON®, together with the colouring agent, contain an aroma –vanillin- that is able to enhance pecking and preening even under low light conditions. The devices most frequently used for the application of Eimeria vaccines are hatchery spraying cabinets or in-line devices that are able to combine coarse spray droplets -for the correct ingestion of the vaccine- together with uniformity of distribution of the vaccine within the chicks’ box. Hipraspray® is the first device that has been specially developed for the administration of the Eimeria vaccines EVALON® and HIPRACOX®.


Jeffers T.K. (1975). Attenuation of Eimeria tenella through selection for precociousness. J Parasitol. Dec; 61(6):1083-90.

Levine P.P. 1938. Eimeria hagani n.sp. (Protozoa: Eimeriidae) a new coccidium of the chicken. Cornell Veterinarian, 28: 263—266.

Shirley M. W., Jeffers T. K., Long P. L. (1983). Studies to determine the taxonomic status of Eimeria mitis, Tyzzer 1929 and E. mivati, Edgar and Seibold 1964. Parasitology 87(2), 185-198.

Vrba V., Poplstein M., Pakandl M. (2011). The discovery of the two types of small subunit ribosomal RNA gene in Eimeria mitis contests the existence of E. mivati as an independent species. Veterinary Parasitology 183, 47-53.

Raised without antibiotics: How to control coccidiosis in broilers and reach this goal? (Part 2)

Nowadays there is an increasing demand for products that come from animals raised without antibiotics. The concerning thing about antibiotic resistance and the alarming situation with the superbug is that it increases the demand for these distinctive products. Problems such as coccidiosis in broilers and maintaining productive efficiency have to be taken into account.

In broiler production, coccidiosis can be controlled through the use of inonophores. Ionophores are antimicrobials and yet they are used in many countries with antibiotic reduction policies. The reason for this is that there are no public health concerns regarding this type of product. Despite this, it can (and it will) induce resistance in microbials, such as Eimeria, and will have an impact on animal health and production results as consequence.

The most significant use of antibiotics for broiler production is for the prevention of coccidiosis in poultry (ionophore coccidiostats are one type of antibiotic), and for the treatment or prevention of necrotic enteritis.

Coccidiosis control is important for the production of broilers raised without antibiotics, helping to prevent the common secondary clostridial disease, necrotic enteritis. One effective way of controlling coccidiosis without the use of antibiotics is vaccination, which is an advantage because of the lack of resistance so commonly found with the use of coccidiostats.

Nutritional management is imperative for the maintenance of gut health. There are more and more types of feed additives on the market, direct-fed microbials, prebiotics, essential oils, and enzymes are just a few of the products available. The idea of combining different feed additives to get maximum efficacy in improving gut health in order to promote feed efficiency and keep birds healthy is a popular one.

One of the pillars of poultry production is biosecurity; not only is nutrition a key factor, but aspects such as the prevention of the entry of pathogens are also essential in the control of pathologies in poultry production. Prevention, such as vaccination against coccidiosis in poultry and biosecurity, are two of the most important factors in the control of pathologies.

However, nutrition and biosecurity measures are not the only resources that help animal producers to rear animals without the use of coccidiostats and antibiotics. On the other hand, we are now living in a highly technological world where everybody collects data that are susceptible of being transformed into information.

Statistics and mainly data analysis is the science that gives us the answers in situations of uncertainty. Statistics is widely used in different fields: from car factories to animal production, companies take advantage of the usefulness of this tool. Hiprastats® -Hipra’s department of statistics- helps customers in different areas, for instance in assessing the risks affecting the results of coccidiosis vaccination.

As matter of fact, HIPRA®, as the reference in prevention for Animal Health, has dedicated its best efforts to the development of ORIGINS®, a pioneering comprehensive consultancy programme powered by Hiprastats® and designed to create plans for raising livestock animals efficiently and competitively, without antibiotics or coccidiostats.

ORIGINS® is based on the identification of the factors that are key for production without antibiotics and with the use of vaccines against coccidiosis in broilers. This allows the classification of those farms in a company with the highest statistical probability of success in producing animals without the use of antibiotics or coccidiostats. Achieving this objective can also improve the overall results of the company, as it will identify strengths and weaknesses.

To sum up, rearing animals without antibiotics and coccidiostats is within the reach of most companies thanks to the new tools currently available in the field of animal production. Nutrition, biosecurity and data analysis are the most important topics to take into account for the achievement of a more sustainable form of production without abuse of antibiotics or ionophore coccidiostats for the control of coccidiosis in broilers.

Data Management and Big Data: Something to deal with coccidiosis in poultry?

The world is connected and this connection generates millions and millions of data. We currently generate data every time we are online whether it’s by using our smartphones, GPS, social networks, when we buy things, when we go to work or when we communicate with each other, among other things.

It could be said that we leave tracks in the form of digital data due to almost every activity we carry out in our daily lives. It is predicted that by 2020, there will be 50 trillion devices connected to the Internet. So what about the poultry sector? The sector is also connected and it is becoming increasingly so. In industry, and particularly in the poultry farming industry, this digital transformation is also taking place.

For example, there are increasingly more devices being used in farms and hatcheries that have humidity sensors, sensors to regulate food, air quality control sensors, sensors for biosecurity, etc. Many of these devices are connected to the Internet and generate digital data on a daily basis. A clear example of this is with Hipraspray®, the vaccination device for COCCIDIOSIS AND RESPIRATORY DISEASES IN POULTRY which is connected to the Internet and provides 100% traceability through its HIPRAlink® software.

What do we get from this digital data and what value is there in BIG DATA Management? 

Does it make sense to opt for mass data management? Does it make sense to invest in big data and in the management of coccidiosis in poultry, for example? Are we capable of predicting, analysing and searching for epidemiological patterns in our hatcheries? The concept has had a low take-up in the poultry sector and only a few people manage their decision-making based on the analysis of big data. However, there is a growing trend to use such technology and in the future such technology will be applied to all business strategies, and this is especially true in the poultry industry when making correct or incorrect decisions could make a really significant difference to production. The 3 key aspects with big data, which also apply to the poultry industry, are:
1. High volume, real time data storage.

2. Thanks to the big data database, we can merge separate data and improve connectivity between different sources (for example, air quality sensors, production management programs, vaccine traceability, farm management software, etc.).
3. Big data software provides the ability to obtain and analyse data streams at high speed. It provides information in real time and helps decision-making become quick and effective (for example, when correlating air quality with data).

The topic is complex, but the answer is yes, if these 3 values are introduced and we use big data, we will be able to hold data that will provide us with answers during times of uncertainty at our farms precisely if we face a big problem of coccidiosis in poultry.

The importance of a smart vaccination in the control of Eimeria

The importance of information and data quality in any production process is no longer a matter for debate. Poultry production is no exception to this and we are increasingly seeing how the use of technology and relevant information is on the rise. The vaccination process and, more specifically, the control of Eimeria should form part of this new information model.In the 2016 ‘Power of Meat’ survey, one of the emerging trends was consumers’ increasing awareness regarding traceability and transparency in the production process of the meat they consume.

There is a general consensus that consumers in the future will be more sensitive towards where their meat comes from and treatments given to animals used for meat production. For example, the same survey from 2017 stated that “antibiotic-free” was the most highly valued specific characteristic for poultry meat consumers ahead of others such as “organic” or “natural”.

HIPRA is completely aligned with these trends with its Origins programme  for rearing antibiotic-free animals and, more specifically, with vaccinations against Eimeria so as to achieve antibiotic-free rearing in poultry production.
As mentioned above, another important trend must be considered: the use of information and technology in any production process. Again, there is an overwhelming consensus that this trend is not going to slow down and that the adoption of new technologies is a key factor in terms of efficiency and productivity. Therefore, with a growing population and the resultant increased demand for protein in the coming years, concepts like efficiency and productivity should not be dismissed.
HIPRA is a strong advocator of the use of technology and believes that the vaccination process should be approached by taking into account all such trends. Our answer to vaccination in terms of traceability, transparency and efficiency is called Smart Vaccination.
With Smart Vaccination, HIPRA offers a new concept in its portfolio to ensure precision and efficacy during the vaccination process, whilst at the same time providing relevant information to make decision-making easier and to increase reliability.
Information such as the time of the vaccination, who administered it, which device was used and the specific details of all vaccine vials used are just one click away with HIPRAlink.
Furthermore, all this information can be easily shared with all stakeholders involved in the production process.

Vaccines are not dosed in the same way as antibiotics. This concept is even more relevant for vaccines against coccidiosis in poultry

A vaccine dose does not depend on body weight: the mechanism of action of vaccines is different to that of antibiotics and, as a result, the dose does not depend on the body weight of the target animal. When considering vaccines against coccidiosis in poultry, the dose is made up of a suspension of sporulated oocysts of different species of Eimeria.

In this suspension, the oocysts are not evenly distributed unless it is mixed thoroughly. If, in addition to this, the dose is reduced, the chance that the chicks will receive all the oocysts of every species decreases exponentially.
A vaccine does not have to be distributed throughout the body and the vaccine components (antigen and adjuvant) do not act directly on the pathogen. In general, the activity of vaccines starts with a rapid and local innate response depending on the route of administration.

Usually vaccines against coccidiosis in poultry are administered orally, thus the first innate immune response takes place in the gut. As a result of this first phase, antigen-presenting cells are activated (dendritic cells and/or macrophages) that are responsible for processing the antigen and carrying it to Peyer patches where they activate specific T lymphocytes, thereby starting the acquired immune response. As Eimeria is an intracellular parasite, the acquired immunity needed is of the cellular type. In this second phase, effector T cells are generated that produce cytokines ensuring a concentration in the tissues that is independent of the age/weight of the animal for the same dose of vaccine.
Does the same thing happen with human vaccines?
In human medicine, the vaccines that are used in children (paediatric vaccines) and in adults are the same and are used in the same dose. It would not occur to anyone to reduce a vaccine dose for children because of the risk of inadequate protection that this would entail. There are examples of toxoids (tetanus), inactivated vaccines (rabies) and live vaccines (varicella) where the dose is the same for children as for adults.
How is a vaccine dose determined?
The dose that is indicated in the leaflet for each vaccine is the one that has been shown to be effective during the different research phases in the target animal species and with the minimum age that can be vaccinated. On the basis of these studies, the health authorities in each country recommend the specified dose for each product. For this reason, the dose should be administered irrespective of the age of the animal.
There are some older products that have different doses for different age groups, but this would not be allowed nowadays.
What harm can be done by a dose that is lower than the recommended one?
Administration of a vaccine dose that is lower than the recommended one can result in a lower immune response, compromising the protection of the individual against the pathogen. Specifically, with vaccines against coccidiosis in poultry, if a full dose is not administered, there is a very strong possibility that there will be an uneven administration of both oocysts and Eimeria species amongst the vaccinated animals with a consequent lack of onset of immunity in some of the chicks.

Dealing with coccidiosis by reducing the use of antibiotics: is it sustainable? (Part 2)

It is our responsibility to search for and choose the right tools to deal with coccidiosis in poultry with current consumer preferences tending towards the purchase of products from livestock grown using sustainable methods.

Because of worldwide concern about drug resistance associated with the immoderate use of antibiotics in poultry production, there has been a major effort to find alternative treatment and methods of prevention.

There is a greater demand for products from sustainable livestock and the higher prices may encourage the farmer. All these factors are in addition to the strongly held beliefs of many consumers that broilers reared with less antibiotic use not only provide additional health benefits to them and their families, but also that sustainable farming practices provide long-term environmental benefits.

It is well known that the major use of antibiotics in poultry farming is linked to coccidiosis prevention and treatment. Therefore, this is the starting point for thinking about reducing their use.

First of all, a biosecurity program needs to be implemented and well managed. It is an everyday goal. The program should address points such as controlling access by individuals, cleaning and disinfection, feed and water quality, access by other animals.

The second step is to study the available alternatives for dealing with coccidiosis. Researchers like Niewold in 2007 have suggested that the unique and highly reproducible effects of in-feed antibiotics may be due to the prevention of immunological stress or their anti-inflammatory effect rather than their antimicrobial role, and this should be considered when searching for new compounds to be used as replacements.

Since we know that prevention it is a key point in sustainable animal farming, vaccination is an important tool to be considered.

Over the past 10 years, experiences in the field have provided data regarding this cost/benefit ratio, derived from the use of rotation programs with precocious attenuated vaccines, such as HIPRACOX®.

Rotation programs allow the poultry farmer to decide on the use of fewer preventive antibiotics – anticoccidials – and to decrease coccidiosis lesions, which means less use of antibiotics as treatment.

This is a long term plan, in which every decision must be taken in a responsible way. Using the right tools, success can be achieved in the matter of coccidiosis with the use of sustainable methods.

Niewold T.A. 2007. The nonantibiotic anti-inflammatory effect of antimicrobial growth promoters, the real mode of action? A hypothesis. Poultry Science, vol. 86 (4), 605-609.

Dealing with coccidiosis by reducing the use of antibiotics: is it sustainable? (Part I)

One of the most worrying problems in poultry production is coccidiosis and how to deal with it without using antibiotics. It is a challenge that, we know, lies in prevention. Furthermore, it is impossible to think in terms of prevention and not to link this to sustainable action.

Thinking sustainably is to link the human population, animals and the environment into every decision or action. It is believing that the world is entirely interconnected.

The concept of One Health was envisaged and implemented by the OIE in the early 2000s as a collaborative global approach to understanding the risks to human and animal health and ecosystem health as a whole, and has everything to do with sustainable action.
Global sustainability affects veterinary medicine on a significant scale, and it is a particular challenge. Since the veterinary professionals play key roles in different parts of the ecosystem, it is necessary for them to understand what is happening in almost every other area of knowledge. Moreover, veterinary medicine is the only profession that routinely operates at the interface of these three components of One Health.
It is important to say that sustainable ways of thinking also look at economic aspects, which are needed for efficient production.
With regard to the poultry industry, it is impossible to make any decision without taking into account the health aspect. Every management plan looks first at the birds’ health because it is something that is influenced by every factor on a farm: buildings, nutrition, welfare.
The importance of digestive diseases is well known and, amongst these, coccidiosis can be named as one of the major health problems, and how to deal with it has been widely discussed during recent years. However, nowadays, there is a great deal of concern about the use of antibiotics in the poultry industry. The widespread use of anticoccidials or antibiotics has led to a resistance problem, which means that many of these drugs are no longer effective. One approach to be considered is to decrease antibiotic usage so that fewer numbers of bacteria are exposed to antibiotics and fewer resistant genes develop. Unnecessary use of antibiotics has been identified, and government associations are recommending a reduction in their usage (e.g. White House, 2015. National Action Plan for Combating Antibiotic-resistant Bacteria Washington, DC pp. 1–62).
Keeping the sustainability aspect in mind, it is to be recommended that poultry farming should focus on prevention rather than treatment. Indeed, in veterinary medicine, prevention and sustainability could be synonymous.
The prevention of coccidiosis without the use of anticoccidials or antibiotics is now a reality for forward-looking farms. There is increasing awareness amongst consumers about the products they purchase. They want to know how the animal was raised and processed, besides what sustainable practices were applied during the process chain.
It is a win-win situation: famers guarantee a standard of flock health, consumers purchase sustainable products.

Key points in the diagnosis of coccidiosis (Part 2: Lesion Scoring)

When decisions concerning the prevention or control of coccidiosis in poultry are based on the subjective scoring of macroscopic lesions, observed in the gut of a number of birds in a flock, several factors affecting the method should be considered. Proper selection of birds, a careful sampling procedure and sample handling along with an accurate judgment of lesions, are some of the most important methodological indicators for success in lesion scoring during a flock inspection.

1. Selection of the right birds in the right number:

Before necropsy, it is essential to check the history of vaccinations, treatments (anticoccidials in particular) and previous diagnoses of the flock to be sampled. It has been shown that the existence of gut lesions is not necessarily accompanied by clinical signs of coccidiosis in poultry (Williams et al., 2000).
In fact, the score that has been used for decades was developed in naive birds (Johnson et al., 1970). However, it has been shown that immunized birds may display lesions and high oocyst counts, with no growth retardation or clinically overt disease. In these cases the lesions are of no economic significance.
As for the number of birds to be examined, it is necessary to seek the right balance between the need to evaluate a representative sample of the batch of birds, and the willingness of the farmer to provide enough birds. Generally, a total of 5 to10 broilers, 25-35-days old, from each house would be reasonable. These birds should be of the average weight of the batch, and be alive at the time of sampling, not debilitated or fasted.
2. Sampling:
As previously mentioned, it is crucial that birds examined for gross lesions (at least 5 per batch), are alive and within the appropriate age range. If multiple groups are inspected, it is better to sacrifice one group and then another to reduce post-mortem artifacts. It is equally important that, as far as possible, the inspections are always carried out by the same person who evaluates the different batches of birds coming from the same farm. This is mainly because their experience enables them to reduce the variation inherent in the scoring system.
The intestine is the first organ to decompose after death. Postmortem changes negatively influence the assessment of pathological changes in the gut. Make the sacrifice humanely with the least possible stress. The preferred euthanasia method on the farm is generally cervical dislocation. This should be carried out by trained staff because if not done quickly and effectively, it can inflict pain and distress. Sacrifice by carbon dioxide inhalation is another valid alternative, if it is available.
3. Sample handling:
To complete the inspection in a systematic way, consider the four segments of the intestine that are shown in Figure 1. Do not expose the inner surface of the intestine until you have inspected the outer wall. It is important to record any change in thickness, colour or presence of spots that may be indicative of injury.
Expose the inside of the digestive system including the gizzard, proventriculus and cloaca. Do it using a different scissors and forceps kit for each group of animals. Observe and describe the content found (amount and appearance), as well as any other signs that catches your attention. Inflammation of the intestine can sometimes be identified immediately after cutting the wall longitudinally, as it tends to fall back on itself.
This only happens when it belongs to a bird that has been recently sacrificed. List all the lesions observed, their exact location, colour, appearance, distribution, shape, etc. Whenever possible, take photos of the lesions found.

There are seven Eimeria species that are responsible for avian coccidiosis, 5 of which cause the disease in broilers: E. acervulina, E. mitis, E. tenella, E. maxima and E. praecox.

Finally, close collaboration between the veterinarian and the farm staff is crucial to avoid possible biases of the method, or the over-interpretation of the lesions found. The availability of detailed information on health management of the flock, and the right amount of suitable birds for inspection will be very important, before making decisions on the control of coccidiosis based on the results of inspections and lesion scoring.

Key points in the diagnosis of coccidiosis (Part 1: Identifying and counting oocysts)

The prerequisite for the control and treatment of coccidiosis in poultry is to correctly identify the presence of disease. Two of the most widely used methods for this purpose are the identification and enumeration of oocysts, and the identification of lesions in the intestine. Although egg identification and counting was described for decades, and has been used since then, it is important to consider some key aspects of the method to obtain valid results.

1) Be familiar with the morphology of the parasite:

Have skills to identify the Eimeria species is the main element to be considered for the success of the morphometric study of field samples. For this, it is convenient to train yourself using pure parasite suspensions obtained in the laboratory.
Although field samples differ greatly from these suspensions (Figure 1), particularly as regards the debris and impurities contained, if they are well preserved (refrigeration at 4-8ºC) the typical morphology of each Eimeria species is easily recognizable.Once familiar with the microscopic appearance, experience after analyzing many samples is what allows you to refine the method, always with an error range due to the “atypical” forms that can be found in all field samples.
2) Use only samples in good condition:
Counting and identification of oocysts, like any other diagnostic method, requires samples to be preserved in good condition. There is, however, a trend to believe that Eimeria oocysts are “indestructible”.
Whilst these parasitic forms are among the most resistant known, their shape can be altered if the oocyst ages or matures (sporulates) over time, particularly when the temperature and humidity are favorable. To avoid this disadvantage, it is very important that the samples are fresh (preferably <7 days after being collected) and remain stored under refrigeration until they are analyzed.Thus maturation is prevented and the number of atypical forms is reduced.
3) Place your confidence in a certified laboratory that provides a guarantee:
Not all laboratories perform the identification and counting of Eimeria oocysts in exactly the same way. However, there are some requirements that must always be met, if valid, repeatable and accurate results are expected. The validity is mainly linked to the prevention of cross-contamination among samples. The possibility of getting false positive results by cross-contamination in the laboratory is very high, particularly in places with a high workload. Thus, practices such as using disposable and sterile materials, changing gloves between critical steps in the procedure, etc., are crucial.
On the other hand, the robustness and accuracy depend very much on the use of calibrated instruments and validated methods. Some key points are the correct homogenization of the sample before processing, weighing accuracy, the use of the correct dilution factor, and a microscopic observation method without artifacts.
Finally, before making decisions about the treatment of coccidiosis based on the laboratory results, it is important to consider that Eimeria is prevalent and is found in the faeces and intestines of poultry.
Therefore the significance of this finding must be weighed against other indicators of disease, such as the presence of clinical signs in live animals, as well as macro lesions and microscopic lesions in the intestine.