Coccidiosis: An Endemic Infection of the Stable
Coccidiosis is an intestinal infection caused by various species of parasitic protozoa of the genus Eimeria spp., with Eimeria crandallis and Eimeria ovinoidalis being the most pathogenic species. Animals between two and four weeks old are usually the most susceptible to infection (although infection can occur at any age) and are typically housed in conditions that favor oral contact with oocysts (the infective form of coccidia), present in feces that contaminate bedding, dams' udders, and drinking and feeding troughs.
Infection is more severe in lambs with lowered immunity and changes in feed, social behavior, possible transport and regrouping, and other concurrent infections (mostly intestinal or respiratory tract infections), often around weaning time. At this moment, the concentration of antibodies from colostrum in the blood drops, leaving the animal defenseless. On the other hand, the animal's immune system is not yet fully mature at that age, making it an ideal time for coccidia infestations to develop.
Symptoms and Consequences
The main symptoms are observed about 3 weeks after infection, during the prepatent period, and include diarrhea with associated dehydration, reduced appetite, anemia, weight loss, poor general condition, and weakness. These symptoms reduce growth and death in 5-10% of the worst afflicted animals. In addition, it is known that Eimeria spp. Infection causes immunosuppression in affected animals, increasing their susceptibility to other diseases, such as respiratory pathologies, which are frequent in animals of this age with poor environmental welfare and housing conditions.
The combination of these circumstances entails serious economic losses in the short and medium term (an affected lamb will never be the sheep it could be), anxiety, and discouragement among farmers and veterinarians.
Environmental Factors and Reinfection Risks
Animals that survive infection develop specific immunity, although they remain asymptomatic carriers who continue to shed oocysts into the environment, representing a constant source of infection in the stable. Even adult ewes are asymptomatic carriers who shed oocysts, especially around lambing.
Maintaining the source of infection combined with the specific resistance of oocysts in the environment means that, in the presence of low bedding turnover, infected animals can be re-infected or become the source of primary infection in subsequently housed animals. Nevertheless, the diarrheal feces of lambs are the primary source of oocysts in the environment, representing up to 100,000 oq/g of feces.
Therefore, coccidiosis is an “endemic infection of the stable” as it is practically impossible to eradicate, meaning we must learn to coexist with it to minimize its negative effects. The appearance of new outbreaks of coccidiosis in a herd with a history of it is to be expected, so in the case of new lambing, we can establish a preventive action protocol to delay its appearance, infection pressure, and clinical severity.
Coccidiosis Control Measures: What can we do if coccidiosis is confirmed in our herd
Coccidiosis control in the herd involves implementing efficient measures at 3 levels:
- Reproductive management
- Cleaning and disinfection of housing facilities
- Diagnosis and treatment of the animals
These measures should aim to achieve two objectives:
- Decrease the load of oocysts in the environment
- Limit exposure of the most susceptible animals as much as possible
Reproductive Management: Adjusting Stocking Density
Firstly, with the vet, we must review the reproductive calendar and design of each lambing to ensure the ideal number of animals in each housing facility where lambing and subsequent rearing will take place (artificial lactation room, feedlot, lambing shed for replacement lambs).
Therefore, estimating the expected fertility and reproduction rate can determine how many ewes will be lambing at any given time. The importance of this initial calculation is based on not oversaturating the lambing pen, lactation room feedlot, etc., in order not to encourage coccidiosis infections.
In addition, shortening the duration of lambing as much as possible (ideally less than 30 days) is recommended for achieving uniform batches of lambs, which will favor implementing the other measures described below.
This form of reproductive control also enables staff to plan better and perform tasks, allowing them to spend more time, for example, on maintaining living spaces.
Following the above calculations and ensuring 1.5 m2 per ewe with lamb, 0.33 m2 per lamb, 0.5 m2 per fattening ewe or replacement ewe lamb helps to control the spread of this disease. For adequate environmental comfort and considering that respiratory pathologies are closely related, we must also take into account the recommendations for optimal static volume per animal: 1.75 m3/unweaned lambs, 4 m3/feeder lamb or replacement ewe lamb, and 10 m3 ewe and her lamb.
These conditions of usable surface area and static volume per animal will significantly impact the animal's environmental well-being. They are also related to heat stress that ewes can suffer in the final phase of gestation, which can potentially condition fetal development and birth weight: lower birth weight can condition the viability of the newborn and the development of its immune system.
Cleaning and Disinfection: Reducing Oocyst Load
Oocysts remain viable and infective for months, so one necessary goal is to prevent them from accumulating in bedding, walls, drinking and feeding troughs, and even on the udders of dams. This will reduce infection pressure and the risk of contagion. Therefore, frequent cleaning and, if possible, disinfection of the facilities are essential.
Adding clean bedding every day establishes a physical barrier between the oocysts, which contaminate bedding and then make animals susceptible to infection. Reducing the humidity of the bedding is also important, as this is an essential factor for the extraordinary viability of the oocysts.
Checking the height of drinking and feeding troughs to ensure their suitability for their intended use will reduce the likelihood of animals defecating and contaminating water and feed with oocysts.
Manure must also be removed and disinfected after each lambing, taking advantage of the production break for cleaning to massively remove the accumulated oocysts. The most highly recommended products for disinfection are those made with peroxides or quaternary ammonium.
As previously mentioned, diarrhoeic feces are the largest source of infection, so it is essential to separate and isolate lambs with diarrhea whenever possible. Even farmers' boots are a means of transmission between facilities, so they are often recommended to start working with healthy animals and work with sick animals last.
In livestock farms, for either milk or meat, where lambs are kept with their mothers (natural weaning), lambs are frequently infected with Eimeria spp. within a few days of birth, as their mothers are typically invisible carriers of the infection. This, coupled with the fact that facility cleaning and disinfection is not carried out at lambing time for management reasons, means that the risk of coccidiosis (presentation of symptoms) just 1 to 2 weeks after weaning is almost inevitable. This may coincide with the changeover of lambs to the feedlot, where the coccidiosis problems are very acute.
In dairy farms with artificial rearing systems, lambs are separated from their mothers at birth after drinking the colostrum. This limits the chances of infection, as they are no longer in contact with their mothers' bedding, where coccidia accumulate. In these cases, when moving the animals to the rearing rooms, where cleaning and disinfection are carried out before the start of each lambing period and production break for cleaning of a certain duration, from 2 weeks to more than 1 month (depending on the reproductive system followed - number of lambing - lambing/year), the incidence of coccidiosis in baby lambs is much lower, with the last lambs to be born and reared being those most affected by the cumulative effect in the lambing pens with warm bedding. In slat systems, the risk is reduced as there is no possibility of such a cumulative effect.
From what we have seen, it seems that eradicating the presence of oocysts in housing is an impossible mission, but reducing them as much as possible may allow lambs to maintain a small amount of contact, a small continuous infection that will provide them with immunity without any clinical signs. However, they may excrete oocysts in their feces, likely in small quantities, but enough to hinder eradication in our herd.
Monitoring, Diagnosis, and Treatment
Since the severity of coccidiosis is determined by the affected animal's immune status, any measure aimed at improving natural defenses is essential: correct vaccination planning during the dam's prepartum period, adequate colostrum intake, and limiting stressful effects in the first weeks of life.
Proper diagnosis is essential before any treatment. Unfortunately, under field conditions, confirmatory coprological tests for coccidiosis are not typically performed as the signs are very characteristic in animals of this age. However, if it is the first time that we observe the above-mentioned clinical signs (2-4 week-old animals with diarrhea, hindquarters stained with dark malodorous feces, stunted growth, poor general appearance, etc.), we should collect fecal samples directly from the rectum of the animals (diarrhoeic and non-diarrhoeic) for laboratory testing of the causative agent (coprological testing via the McMaster method). The suspicion of coccidiosis should be noted, but it is also important to test samples for the presence of other bacterial agents that cause diarrhea in case of concomitant infections.
Samples of feces from several animals (no more than 10) from the same flock, without clinical signs, can be pooled, and individual samples from the animals with diarrhea can be analyzed.
Treatment and Metaphylaxis
Once a coccidiosis diagnosis has been confirmed, the best treatment formula is metaphylactic: treating all animals present, with or without symptoms, from about 10 days of age. The idea is to try to halt the parasite's biological cycle in its prepatent period (3 weeks after infection, which may have been in the first days of life).
Diclazuril is very effective as it affects different internal phases of the coccidia biological cycle, so it can be used on a single day to treat the whole flock of animals present (if we have ensured correct reproductive management, all animals will have an age range of 3-4 weeks maximum). Diclazuril, which has a 0-day withdrawal period, can be used on suckling lambs (still suckling from their mothers or on artificial rearing for slaughter) and fattening lambs or weaned replacement ewe lambs. This single treatment facilitates management and will reduce symptoms in the most affected animals and reduce the shedding of oocysts into the environment (for approximately 2 weeks), thus limiting the likelihood of infecting the next animals to be moved into the same housing area and of possible reinfection in the currently infected animals.
Under conditions of high infection pressure, a second treatment may be indicated approximately 3 weeks after the first dose. This second treatment would break the biological cycle of the parasitic forms developed in the gut after a presumed early re-infestation after the first treatment.
Dosage and Treatment Administration
Dosages must be adapted to each animal's weight, as doses vary for every 2.5 kg of live weight: animals with an age difference of 3-4 weeks can be housed together in lambing pens and present a wide range of weights.
A new coprological test 1-2 weeks post-treatment will provide results of the efficacy of the treatment or the possible appearance of resistance.
If diarrheal feces testing shows other pathogens, antibiotic treatment should be administered according to the findings.
Finally, as mentioned, this disease will persist within housing, so monitoring diagnosis and treatment in future animals will be essential. Moreover, because recovered animals and adult ewes are often asymptomatic carriers, it is highly advisable to perform coprological testing during each pre-lambing period to determine as early as possible the potential likelihood of problems arising in lambs and to implement all the above-mentioned preventive measures.
References
- Bangoura, B. & Daugschies, A. (2020). Coccidiosis in catte. In Coccidiosis in Livestock, Poultry, Companion Animals, and Humans. Edited By J. P. Dubey. CRC Press.
- Bangoura, B., & Bardsley, K. D. (2020). Ruminant Coccidiosis. The Veterinary clinics of North America. Food animal practice, 36(1), 187–203.
- Bowman, D. D. (2022). Georgis’ Parasitology for Veterinarians Saunders, 11va edición. Elsevier.
- Jolley, W. R., & Bardsley, K. D. (2006). Ruminant coccidiosis. Veterinary Clinics: Food Animal Practice, 22(3), 613-621.
- Keeton, S. T. N., & Navarre, C. B. (2018). Coccidiosis in Large and Small Ruminants. The Veterinary clinics of North America. Food animal practice, 34(1), 201–208.
- Kennedy, M. J., & Church, T. L. (2001). Coccidiosis in cattle. Alberta Agriculture, Food and Rural Development.
- Reddy, B. S., Sivajothi, S., & Rayulu, V. C. (2015). Clinical coccidiosis in adult cattle. Journal of parasitic diseases, 39(3), 557-559.
Further reading
Sheep Pox and Goat Pox: A Growing Threat to Greek Livestock Farming and Economic Stability