Contribution of DNA-based diagnostic methods to the treatment of coccidiosis in poultry. What’s New?

In the fight against infectious diseases, the first step is the correct identification of the causative agent, and the symptoms and lesions that it causes in the host. A correct diagnosis influences on the effectiveness of the treatment established, particularly if it is combined with preventive measures such as vaccination. Traditional techniques such as microscopic observation and oocysts counting remain very useful as screening methods, and an aid in the diagnosis and treatment of coccidiosis in animals. DNA-based methods such as PCR have overcome some limitations of these conventional methods, allowing the analysis of more samples in less time, increasing sensitivity and allowing the quantification of the parasite in one step.


These new methods positively influence the treatment of coccidiosis, expanding the possibilities for the poultry veterinarian to control the disease.

Diagnosis of coccidiosis in poultry by stool analysis methods in the laboratory has some limitations inherent to the type of sample used. Faeces collected on the farms are sent to the laboratory for microscopic examination of Eimeria oocysts. If this first step takes too long oocysts change their morphology, which makes microscopic identification tricky. The possibility of obtaining false results when analysing samples in poor condition is high. This may affect the effectiveness of the treatment of coccidiosis in broilers and laying hens.
Another limitation of conventional parasitology in the diagnosis of coccidiosis in poultry is the simultaneous presence of three or more species of Eimeria within a flock of birds. If the treatment of coccidiosis or its prevention by vaccination is aimed at the kind of acting Eimeria, misidentification could induce treatment failures. Finally microscopy as a diagnostic method of coccidiosis in poultry is limited to the identification of the species of parasite and the approximate amount present in a gram of sample. Other characteristics such as resistance to certain anticoccidials, etc., cannot be assessed by these techniques.
At the end of the 90s, new methods of detection and identification of Eimeria in chickens based on DNA techniques were developed. Specifically PCR (polymerase chain reaction) protocols for epidemiological purposes (Schnitzler 1998) were described. Subsequently the PCR method has been improved, and in the 2000s the first methods of real-time PCR (Kawahara 2008) that reduced analysis time, improve assay sensitivity and reduce cross-contamination between samples were optimized. This made possible to establish the treatment of coccidiosis more accurately and quickly.
The refinement of PCR methods has been continued in recent years. One of the limitations inherent to the analysed samples is the presence in the faeces of substances capable of inhibiting the action of the polymerase, which is the engine of the synthesis of DNA copies during the amplification step. The development of optimized methods of obtaining and purifying DNA (Gerhold 2015), and the addition of internal control (IPC) in each reaction well (Raj 2013), has largely reduced false negative results due to reaction inhibition. The IPC must be positive in each and every one of the samples analysed in order to be considered a valid PCR assay.
The PCR reaction can be divided into four phases that are displayed in the amplification plot (see image above).
More recently, the real-time PCR has been optimized for simultaneous obtaining of qualitative and quantitative results. Thus, it is possible to get accurate identification of the species of Eimeria present in the sample as well as the amount of each of them (Nolan 2015). At present, the PCR is a robust and target-specific detection method for Eimeria in poultry. The PCR solves some major limitations of microscopic examination of stool, allowing analysis of large numbers of samples in less time, the examination of faeces, tissues and even suspensions of oocysts, and even serves as a method to ensure the identity and purity of strains present in vaccine preparations (You 2014).
Therefore, the PCR has a direct impact on the treatment of coccidiosis, based on a timely and reliable diagnosis. However the laboratories using quantitative PCR methods for the diagnosis of coccidiosis in poultry, require highly trained personnel, calibrated instruments, and standardized protocols to ensure repeatability and accuracy.
Finally, successes in diagnostic and subsequent treatment of coccidiosis in poultry depend largely on the interpretation of the results. Interpretation should be based on the clinical history, the estimated time of infection and signs and lesions observed. PCR along with the classic method of observation of the parasite and the clinical judgment allows improving the treatment of coccidiosis on the basis of a comprehensive approach.
This video animation illustrates the main advantages of the quantitative real time PCR.

New strategies for the control of coccidiosis in poultry: rotation programmes with vaccines against Eimeria

From the very beginnings of this type of animal production, control of digestive diseases in the poultry industry has been one of the most significant health challenges. Moreover, among digestive diseases, coccidiosis in poultry continues to pose a challenge for the poultry farming worldwide. The incorporation of new tools provides new resources for safe and effective control.


Where are we coming from?

The housing conditions of birds used in production constitute a trigger factor for digestive diseases, with coccidiosis in poultry being one of the most prevalent, caused by parasites of the Eimeria genus. 

From the very beginnings of industrial poultry farming, controlling coccidiosis in poultry has been largely based on the use of so-called coccidiostats or anticoccidial drugs. According to Chapman (2001), in the USA 99% of industrial operations involving broiler chickens between 1995 and 1999 used anticoccidial drugs. This figure currently stands at between 60 and 99% of operations, depending on the time of year (Chapman, unpublished observations). One consequence of this widespread use of anticoccidial drugs has been the development of resistances, which have been documented against all drugs and in all areas where poultry production takes place under industrial conditions (Chapman, 1997). The poultry industry has handled resistance-related problems through medication schemes that are commonly known as “shuttle” and “rotation”. These administration patterns involve different types of drugs (ionophores and chemicals) and have been able to delay the development of resistances, although most Eimeria isolates show varying levels of resistance to more than one drug (Chapman, 1997; Peek and Landman, 2003).

Where are we headed?

In the wake of vaccines against avian coccidiosis, a new tool has been introduced in control programmes against coccidiosis in poultry. The use of vaccines as part of a rotation scheme (alternating vaccinated cycles with cycles with traditional anticoccidial programmes) has revealed an improvement in sensitivity to anticoccidial drugs used prior to the introduction of the vaccines (Chapman and Jeffers, 2015; Mathis and Broussard, 2006; Peek and Landman, 2006; Dardi et al., 2015).

The main effect of including vaccines against coccidiosis in poultry in rotation programmes is the recovery of sensitivity to anticoccidials. This was shown by Dardi et al. (2015), who used the McDougald et al. (1986) method to assess the percentage by which gut lesions had been reduced (Johnson & Reid, 1970) in comparison to the unmedicated and infected group. Accordingly, after the first vaccination cycle, the parasites present at the vaccinated farm revealed already an improved sensitivity to anticoccidials:


This effect is justified based on:

Recombination during the sexual stage of replication (gametogony): field strains can exchange genetic material with the vaccinal ones. In this way, vaccinal strains can introduce in the field population sensitivity genes (Shirley et al., 2000, 2007).

Farms are “seeded” with sensitive oocyst.

Taking out anticoccidials, also the selective pressure which induces the strains to be resistant decreases. Decreasing the selection for resistant strains, there is already a return to more sensitive profile in the oocyst field population (Chapman, 1997).

Strategy for using vaccines against coccidiosis in poultry

Introducing precocious attenuated vaccines such as HIPRACOX® in rotation programmes for the control of coccidiosis in poultry is no longer complicated or difficult to implement as we now have access to massive spray application systems for chickens. The rotation programmes that include these vaccines may follow a scheme such as the one proposed by Chapman and Jeffers (2014) for broiler chickens in the US. If yearly chicken production cycles are six, an anticoccidial program is used for the first two flocks (January to April), then litter is removed (cleanout) to reduce the resident Eimeria population. Afterward, a vaccine containing sensitive strains is used for two flocks (May to August) to repopulate the house and finally from September to December (two flocks) a different anticoccidial programme is used.

Alternatively, there are schemes based on the incorporation of precocious attenuated vaccines such as HIPRACOX®, for which there are no strict guidelines regarding periods of the year when to use the vaccine or litter handling, for markets such as Europe where litter recycling is prohibited.

Rotation programmes with vaccines against coccidiosis in poultry currently represent a new strategy which may ensure a better long-term response to coccidiosis control, as well as improved production results due to the implementation of precocious attenuated vaccines within the control scheme against the Eimeria parasite.

Does vaccination of 8 weeks old pigs protect them against PRRS until slaughter?

Answered by: Tomasz StadejekPublished on: July 21
Vaccination of 8 weeks old pigs can protect them against PRRS until slaughter. However it is very important to remember that the protective immunity against PRRSV develops slowly and it takes at least 4 weeks, or longer.

So, pigs vaccinated at 8 weeks of age should be protected against the challenge at least until 12 weeks of age. Even then vaccinated pigs can get infected. The level of cross protection of a given vaccine and a given wild type strain can be different. The same vaccine can have different efficacy in different farms.
However, even if the cross protection against the infection with filed PRRSV is not ideal, it is usually sufficient to protect against clinical disease caused by the infection and limits virus shedding.

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Eimeria immunogenicity, basic information and protection conferred by a precocious line of Eimeria necatrix.

Eimeria spp is a protozoan parasite with a complex life cycle and so is the host immune response to Eimeria infection. In the last decade, huge progress has been made in the identification of host and parasite genes involved in immunogenicity but there are still some immunity mechanisms to be discovered.

As a general rule, we say that Eimeria immunity is species-specific, meaning that each species of Eimeria is able to stimulate protective immunity against itself. Although some studies suggest that partial cross-protection can be achieved (Augustine et al. 1991), from a practical perspective we have to assume the widely accepted belief that there is no cross-protection between species.

The role of antibodies is negligible in the immune response to Eimeria spp despite being abundantly synthesized after contact with the parasite, whilst the role of cell-mediated immunity is vital. This fact has been described in several studies where the removal of the bursa of Fabricius did not interfere with the development of immunity against Eimeria (Lillehoj et al. 1988).

Eimeria infection will induce an inflammatory reaction in the intestine that will start with the secretion of mucin by the goblet cells to build up a physical barrier in an attempt to minimize the invasion of epithelial cells by the sporozoites.

Other mechanisms of the innate immune response will be activated following exposure to the sporozoites. Macrophages, dendritic cells (DCs) and natural killer cells (NK) will be mediators in this primary non-specific immune response. Macrophages are phagocytes with cytotoxic activity that produce cytokines which mediate in the inflammatory response. DCs are also components of the mononuclear phagocyte system which express high levels of major histocompatibility complex class II (MHC II) and they are the main antigen presenting cells to T helper cells during the primary immune response. NK cells are non-phagocytic cells with cytotoxic effect that will lyse infected enterocytes. Chickens don’t have lymph nodes so it’s likely that primary antigen processing occurs in the mucosal-associated lymphoid tissue of the gut (GALT).

Avian GALT includes the bursa of Fabricius, the caecal tonsils, Meckel´s diverticulum, Peyer patches and intraepithelial lymphocytes. CD4+ T cells recognize antigen peptides displayed by MHC class II molecules. CD 4+ T cell activation by DCs triggers their differentiation along two pathways: CD4+ Th 1 lymphocytes that secrete IL-2, IFN-g and TNF b providing support to cytotoxic T cells (CD8+), and CD4+ Th 2 that mainly secrete IL-4, IL-5 and IL-13 and essentially provide support to B Lymphocytes. In subsequent Eimeria infections, an adaptative immune response will take over from a non-specific immune response and cytotoxic T cells (CD 8+) will play the major role in controlling the infection. The main determinant of differentiation of CD4+ T cells towards the Th 1 or Th 2 pathways is the extent and type of DC activation by the innate system.
Specific adjuvants may favour CD4+ responses to Th 1 or Th 2. HIPRAMUNE® T is an adjuvant that, applied together with EVALON® vaccine, skews the CD4+ response towards the Th 1 pathway, increasing the secretion of IL-2 and IFN-gamma and consequently the CD8+ T cell differentiation.

Nowadays live vaccines are the only alternative to anticoccidial drugs as an effective coccidiosis control measure. A large number of oocysts is generally required to generate a good immune response so the use of attenuated Eimeria lines in a vaccine is crucial to avoid the problems associated with non-attenuated lines.

In the development of a live attenuated vaccine against avian coccidiosis for long-life cycle chickens we have to pay special attention to Eimeria necatrix. This species is one of the most pathogenic, schizogony occurs in the lamina propria and crypts of Lieberkühn of the midgut causing extensive haemorrhage, so achieving a good level of immunity after vaccination is essential. On the other hand, Eimeria necatrix produces a low number of oocysts per cycle so the initial dose delivered in the vaccine should be high to assure sufficient replication. As a result, we need a very well balanced attenuated line that lacks the pathogenicity of the parent strain but keeps enough reproductive potential to retain its immunogenicity.

Three methods of attenuation to produce a live attenuated Eimeria line are known: by serial passage of the parasite in the choriallantoic membrane (CAM) of embryonated eggs, by gamma irradiation, or by selection for precocious development. In the literature we can find papers on Eimeria necatrix attenuated lines produced by serial passage in CAM and attenuated lines produced by selection for precocious development as candidates for inclusion in a live vaccine against coccidiosis. Shirley in 1980 described an attenuated line of E. necatrix produced by passage in CAM. Later on, in 1984, Shirley et al. found that attenuation of virulence in their line was not genetically stable. The line produced after 29 passages in CAM became highly pathogenic after only six consecutive passages in chickens.
Other studies showed the trait of attenuation to be stable in precocious lines of Eimeria tenella, E. acervulina and E. praecox so in 1984 the Shirley’s group attempted to develop an Eimeria necatrix line attenuated by selection for precociousness. They used the Houghton (H) strain of E. necatrix as the parent strain and several precocious lines with different generations of selection, 20, 25 and 30 generations, derived from the H strain. They checked body weights and intestinal coccidiosis gross lesions to test the pathogenicity of the different lines. To check the reproductive potential they measured the output of oocysts from chickens given different doses of oocyst of the different lines. And to check the immunogenicity, birds inoculated with different doses of the different lines were challenged 15 days after the primary inoculation.
The results showed that despite a marked attenuation of virulence, the precocious lines retained much of the immunogenicity of the parent strain. These studies support the idea that precocious lines are preferable to egg-adapted lines for production of live attenuated vaccines against avian coccidiosis.

Which of vaccination protocols (mass vaccination or 6/60, or others) will be more effective in PRRS elimination from a herd? Can we introduce naïve replacement gilts, or rather vaccinated? 

Answered by: Tomasz Stadejek
Published on: July 14, 2016
Having in mind that PRRSV can persist in tonsils for a year, and that following elimination procedure, after 8 months the diagnostic results are negative, can we introduce naïve replacement gilts, or rather vaccinated? If vaccinated, with what vaccine, modified live or inactivated?

The question should be more specific, are we talking about elimination of PRRSV circulation in sows and production of PRRSV free piglets (stable herd), or the plan is to obtain complete elimination of PRRSV and specific antibodies (negative herd)? At present the most often used criteria are those developed by Holtkamp and co-workers.

Sow farms with animals reacting positive in ELISA and PCR, and showing clinical symptoms of PRRS are termed positive unstable (category I). Sow farms positive stable (category II) are ELISA positive but in piglets at weaning PRRSV was not detected in the last 90 days, in at least 4 consecutive tests, and no clinical symptoms of PRRS are observed.

In provisionally negative farms (category III) naïve replacement gilts remain seronegative after 60 days from introduction to a seropositive herd. Lack of seroconversion after direct contact with seropositive sows proves that older sows do not shed PRRSV.

Negative sow farms (category IV) are PCR and ELISA negative. Herd stabilization (category II) can be achieved following herd closure and/or mass vaccination program with modified live vaccine.

If the herd is open, replacement gilts have to be vaccinated at quarantine. Next steps depend on the final goal the producer wants to achieve. If the goal is category IV, no vaccines can be used. Maintaining category II requires gilts vaccination with modified live vaccine. If the risk of PRRSV re-infection is high (low external biosecurity, high pig farm density) it makes more sense to continue mass vaccination in sow herd, and keeping category II. Application of inactivated vaccines can be only considered as an additional booster following vaccination with attenuated vaccine.

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Coarse spray application of a coccidia vaccine for correct oocyst ingestion

Proper oocyst distribution is a key point for the success of spray application of a coccidia vaccine. Generally speaking, a coccidia vaccine is a suspension of sporulated oocysts in a PBS solution. Because of this fact and because of the characteristics of the oocysts, there are some differences to a common viral freeze-dried vaccine that must be taken into account during the vaccination process.


There are several methods by which coccidia vaccines can be applied, but probably the most convenient, consistent, reliable and accurate way is via coarse spray in the hatchery. Spraying the vaccine directly on to the feed risks desiccating the oocysts and that is one of the few weak points of oocysts. Other options such as via the drinking water are also suitable, but this is tedious and involves some risks, for example, in the case of long nipple drinker lines oocysts will be deposited at the bottom and can also be retained along the nipple mechanism. In some countries the vaccine is applied by spray on the farm at the time the chicks are received. This method is also effective but it is time-consuming for the staff, there is inconsistency between farms, portable sprayers or backpacks are not as accurate as cabin sprayers and it can be counterproductive for the day old chicks if water and feed withdrawal are increased after an already long journey.
As shown in the title, oocyst distribution is the key factor for the success of spray vaccination in the hatchery. The first challenge that we face is maintaining a homogenous distribution of the oocysts in the suspension. Once the vaccine is diluted in the total amount of water that will be used for vaccination, the oocysts have to be kept evenly distributed in the vaccine solution. To achieve this nowadays, magnetic stirrers or aquarium oxygenation systems are used. As the vaccine solution is used and the volume decreases, if no adjustments are made to the speed of the magnet or the bubbling, the oocysts will be unevenly distributed in the solution and consequently the vaccine will not be applied evenly. Some boxes will receive high numbers of oocysts, while others will receive low numbers or, in extreme situations, no oocysts at all. Nowadays, technology allows us to control this critical point of the process with more precise stirring mechanisms such as the one used in HIPRASPRAY®. The vaccine container in HIPRASPRAY® has a volume level control and the stirrer mechanism adjusts itself automatically according to the level in the container.
A second challenge for a homogenous distribution of the oocysts is the time when the vaccine is actually sprayed. There are two main parameters that have to be controlled, droplet size and spray pattern.
Oocysts have to be ingested so a really coarse spray is needed, over 200 µm, preferably 250 µm, at the time of vaccination. To obtain such a large droplet size, the type of nozzle, the volume of vaccine solution and the pressure of the piston have to be considered.


Starting with the nozzle, there is no standard recommendation so the supplier of the vaccination equipment has to provide a guideline as starting point. Most of the time, the nozzle is the limiting factor and decisions such as cone type versus fan type, as well as flow rate, have to be made. The selection of cone or fan will be mainly made according to the kind of spray device that is used. Manual cabin sprayers require a cone-type nozzle, usually a hollow cone, so it is not uncommon to find a “dead” area that is not covered by the vaccine solution. Automatic or semiautomatic devices allow conveyor belts and fan type nozzles to be used, spraying a “curtain” covering the whole surface of the chick box with no “dead” areas.


This kind of spray device using conveyor belts allows us to introduce belt speed and box size sensors, increasing the reliability and accuracy of the vaccination process. A minor detail but crucial for good oocyst distribution is the absence of any obstruction such as strainers on the circuit or nozzle.
Moving on to the pairing volume & pressure – with a fixed volume and by modifying the pressure applied on the piston, the droplet size as well as the spray pattern can be varied, and vice versa. This is the reason why it is important to have a consistent and reliable source of pressure. We are used to cabin sprayers using compressed air to move the piston and the source of the compressed air comes from a portable compressor or from a central compressed air line commonly found in hatcheries. Sometimes we experience fluctuations in compressed air flow that can affect the accuracy of the vaccination process. Electronically operated pistons eliminate this risk factor and are far more accurate than any air-operated pistons. While for respiratory vaccines we apply volumes of vaccine solution between 12 to 18 ml per box (80 to 100 chicks per box), in coccidiosis vaccines larger volumes of around 25 to 28 ml per box will be used. It is important that all the birds in the box are wet and that there is no excessive waste of vaccine solution outside the box or on the walls. The vaccine solution on the walls of plastic boxes can be consumed by the chicks but this phenomenon can’t be exploited on cardboard boxes where vaccine solution will be immediately absorbed and the oocysts will therefore be unavailable.
Hatchery coccidiosis spray vaccination can be the best option if we manage to obtain proper oocyst distribution during the process. With a spray device like HIPRASPRAY® all the variables that can affect the efficacy of the vaccination are under control.

Why in 5 weeks old piglets respiratory disease due to PRRSV appears despite vaccination of sows with a MLV PRRS vaccine every 4 months, and which have high level of antibodies?

Answered by: Tomasz Stadejek
Respiratory symptoms in piglets can be caused by a number of pathogens. In order to identify a causing factor it is necessary to conduct laboratory diagnosis.
Confirmation of PRRSV role can be performed through PCR analysis of lungs from sick animals. If such material is not available, serum obtained from pigs from different age groups can be tested by PCR or ELISA. Detection of PRRSV in serum of sick animals indicates viremia and can be considered as a proof of the virus’ role in respiratory disease in a given age group.
Appearance of antibodies against PRRSV in pigs at about 2 weeks from the start of the symptoms also supports such diagnosis. However, analysis of serological results is complex and we have to keep in mind that maternal antibodies can be detected in pigs for several weeks. This is why it is so important to test sera from groups of pigs of different age (e.g. 4, 6, 8 weeks of age etc.) and to assess the dynamics of seroconversion (compare the levels of antibodies in different age groups).
If diagnostic results confirm the role of PRRSV in the clinical disease in piglets, it may suggest that the vaccination program in sows is inefficient. It can be caused by insufficient cross protection against the local strain, poor colostrum management as well as vaccination errors.
The impact of limited cross protection can be diminished with the increase of frequency of mass vaccination in sows, from 3 to 4 per year. Vaccination every 3 months will likely increase the level of passive immunity.
The level of antibodies in vaccinated sows is difficult to correlate with the level of immunity. Antibodies detected in ELISA are directed against capsid protein and they are not protective. Moreover, sows from stable farms, where PRRSV does not circulate, and which were vaccinated with modified live vaccine multiple times, can have low or undetectable in ELISA levels of antibodies, and still be immune

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Can we enhance pecking and preening for oocyst ingestion in coarse spray vaccination against coccidiosis?

Uniform ingestion of coccidiosis vaccines made of attenuated sporulated oocysts is of paramount importance for the correct intake of these vaccines and subsequent onset of immunity and has to take place soon after the vaccine is coarse sprayed over the chicks. In order to achieve this, we need to enhance the pecking and preening behaviour of the chicks with the help of a colour and an aroma.

The application of vaccines via coarse spray was conceived mainly for the oral administration of coccidiosis vaccines made of sporulated oocysts.

This type of vaccination requires a droplet size of more than 200 microns, which is achieved by controlling the type of nozzle and the pressure that are used. For consistent vaccination, active ingestion of the vaccinal water droplets containing oocysts is crucial. It has been reported in the literature that the inclusion of colouring agents has a marked effect on coarse spray vaccination, inducing greater preening activity and thus increasing the ingestion of spray-applied vaccines.
The ingestion of oocysts contained in the vaccinal water after coarse spray administration is achieved by the birds actively pecking the droplets that are located in the feathers of other birds or by pecking the droplets from themselves (behaviour called self-preening). Any component of the vaccinal water that increases the ability of the birds to locate the droplets or enhances the intake of vaccinal water droplets will be of great importance for correct and homogenous vaccination.
The selection of the components to be associated with the oocyst vaccine HIPRACOX® started by studying the work of other authors in which the colour preferences in young chicks had been described. It has been reported that chicks have colour peak preferences in the orange-red and blue-violet regions (Fischer et al.). 1, 2
However, blue-violet seems to be the colour spectrum of maximum preference of one day-old chicks and because of that, this was the colour spectrum selected.
Due to the fact that blue-violet (a secondary colour) can be only achieved by mixing two primary colours, a red colour and a blue colour were chosen, giving a light purple as a result.
By the addition of the light purple coloration to the vaccinal solution containing the oocysts, under normal light conditions the birds easily detected the vaccinal droplets and thus homogeneity of vaccination was improved.
Caldwell et al.3, 4 demonstrated a direct correlation between ingestion of droplets containing oocysts (increased preening activity) and photo-intensity. Unfortunately, the conditions of light intensity in most hatcheries is very poor in the area were chicks are spray vaccinated or in the area where the cages are piled up after vaccination and stored before transportation to the farm.
Commonly, light intensity in working conditions needs to be between 200 and 300 lux. However, the study of several hatcheries showed that where coarse spray oocyst vaccination takes place, light intensities varied from 100 to 200 lux, and was even lower in one (80 lux). Fischer et al.2 demonstrated that birds have light-adapted viewing, thus, these low light intensities could adversely affect vaccination. Moreover, light intensity is also decreased by the fact that after vaccination birds’ boxes are commonly piled up, further decreasing light conditions.
Because of this, the colouring agent was also selected for being the one that gave better results at a light intensity of less than 100 lux. Moreover, another component was introduced to the colouring agent to solve this problem: an aroma.
It is interesting to mention that Burne et al.5 demonstrated that birds can respond to odorants and that they first use the visual stimulus and secondly they can use an odour stimulus. Because of this, the possibility was investigated of introducing an odorant into the final colouring agent in order to make it effective at poor light intensities as well.
We finally decided to include vanillin in the formula due to the fact that it increased the number of pecking events in conditions of poor light intensity (80lux).

The application of vaccines via coarse spray was conceived mainly for the oral administration of coccidiosis vaccines made of sporulated oocysts.

This type of vaccination requires a droplet size of more than 200 microns, which is achieved by controlling the type of nozzle and the pressure that are used. For consistent vaccination, active ingestion of the vaccinal water droplets containing oocysts is crucial. It has been reported in the literature that the inclusion of colouring agents has a marked effect on coarse spray vaccination, inducing greater preening activity and thus increasing the ingestion of spray-applied vaccines.
The ingestion of oocysts contained in the vaccinal water after coarse spray administration is achieved by the birds actively pecking the droplets that are located in the feathers of other birds or by pecking the droplets from themselves (behaviour called self-preening). Any component of the vaccinal water that increases the ability of the birds to locate the droplets or enhances the intake of vaccinal water droplets will be of great importance for correct and homogenous vaccination.
The selection of the components to be associated with the oocyst vaccine HIPRACOX® started by studying the work of other authors in which the colour preferences in young chicks had been described. It has been reported that chicks have colour peak preferences in the orange-red and blue-violet regions (Fischer et al.). 1, 2
However, blue-violet seems to be the colour spectrum of maximum preference of one day-old chicks and because of that, this was the colour spectrum selected.
Due to the fact that blue-violet (a secondary colour) can be only achieved by mixing two primary colours, a red colour and a blue colour were chosen, giving a light purple as a result.
By the addition of the light purple coloration to the vaccinal solution containing the oocysts, under normal light conditions the birds easily detected the vaccinal droplets and thus homogeneity of vaccination was improved.
Caldwell et al.3, 4 demonstrated a direct correlation between ingestion of droplets containing oocysts (increased preening activity) and photo-intensity. Unfortunately, the conditions of light intensity in most hatcheries is very poor in the area were chicks are spray vaccinated or in the area where the cages are piled up after vaccination and stored before transportation to the farm.
Commonly, light intensity in working conditions needs to be between 200 and 300 lux. However, the study of several hatcheries showed that where coarse spray oocyst vaccination takes place, light intensities varied from 100 to 200 lux, and was even lower in one (80 lux). Fischer et al.2 demonstrated that birds have light-adapted viewing, thus, these low light intensities could adversely affect vaccination. Moreover, light intensity is also decreased by the fact that after vaccination birds’ boxes are commonly piled up, further decreasing light conditions.
Because of this, the colouring agent was also selected for being the one that gave better results at a light intensity of less than 100 lux. Moreover, another component was introduced to the colouring agent to solve this problem: an aroma.
It is interesting to mention that Burne et al.5 demonstrated that birds can respond to odorants and that they first use the visual stimulus and secondly they can use an odour stimulus. Because of this, the possibility was investigated of introducing an odorant into the final colouring agent in order to make it effective at poor light intensities as well.
We finally decided to include vanillin in the formula due to the fact that it increased the number of pecking events in conditions of poor light intensity (80lux).
In conclusion, the components selected to be included in the colouring agent for administration of the oocyst vaccine HIPRACOX® via coarse spray enhance the ingestion of the spray-applied vaccine in conditions of either normal or poor light intensities.
HIPRACOX® and now also EVALON® are the only coccidiosis oocyst vaccines with a dedicated colouring agent and aroma which are able to enhance the intake of the vaccine even under poor light conditions.

Which few words come to mind when you hear PRRS?


The Porcine Reproductive and Respiratory Syndrome is at the centre of every conversation between farmers and swine veterinarians in the most important pig producing countries worldwide, with the exception of Australia, Brazil, Argentina and some Scandinavian countries.
If you are working in an environment that is positive for the porcine respiratory and reproductive syndrome, control of the disease is the key element in all discussions. The vets in this video reflect perfectly what PRRS means when someone mentions this BIG WORD.
PRRS means problems, regardless of whether it is the respiratory or the reproductive form of the disease, everything gets worse when PRRS is around, says Albert Rovira in his contribution, and this is really relevant because working in diagnostics as he does, there are few cases where the porcine respiratory and reproductive syndrome is not involved. It´s pretty well known that this disease is normally at the centre of any respiratory coinfection in piglets and fatteners.

However, for Alberto Stephano the key word is frustration and it certainly is, he is absolutely right because, in the past or even today, a great deal of effort has gone into to controlling this syndrome and yet there have been many failures. Moreover, another of our speakers, Darwin Reicks from the Swine Vet center in Minnesota, agrees on that statement and I loved one of the quotes when he says: It seems the virus is often one step ahead of us . 
Coming back to Europe and from Barcelona University, one of the most highly regarded European researchers in the porcine respiratory and reproductive syndrome, Enric Mateu, introduces a new word to us: challenges, because of the difficulty of control in the long term, and this is also a key point we would like to mention. We have enough knowledge for this disease to be controlled, but the question here is for how long? It´s clear and even though it is a parameter, some vets are using it as an indicator, reinfections do exist, and the question that many producers are asking is… When will the next PRRS outbreak occur on my farm?
Quim Segales and Luc Dufresne concur on another shocking word, devastation and devastating disease, but not only when the disease affects a negative farm for the first time, but with the persistence of the virus circulating with a heterologous pattern around the multiple buildings of the farms.
However, for practitioners like Albert Finestra and Alberto Morillo, the disease symptoms are at the top of the list of words that come to mind, and as well as that, Albert adds that more than words you´ll have mixed feelings, such as panic amongst others. Carlo Lasagna from Italy agrees on panic and he adds a crucial term, not mentioned so far….disappointment for the farm´s employees.
Last but not least, and as usual, from the American point of view and with a tremendously practical vision, Scott Dee reflects on what the porcine respiratory and reproductive syndrome really means for producers and veterinarians…and it means ECONOMIC LOSSES.
We believe that the highlighted words (in bold) in the text provide a true summary of what this disease means for everyone involved in this industry. Let´s not lose hope!!!!!!