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Some aspects of coccidiosis in sheep and goats
Small Ruminant Research 110 (2013) 93–95
Contents lists available at SciVerse ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Some aspects of coccidiosis in sheep and goats夽 A.H. Andrews Acorn House, 25, Mardley Hill, Welwyn, Hertfordshire AL6 0TT, United Kingdom
a r t i c l e
i n f o
Article history: Available online 14 December 2012 Keywords: Coccidiosis Eimeria Kid Lamb Oocyst
a b s t r a c t This paper provides a brief review of the widespread and economically important disease of coccidiosis. At one time, coccidia were considered to be virtually non pathogenic, but by the 1960s they were recognised to cause disease. Almost all young lambs and kids will be exposed and become infested during their early life and there are similarities and differences between the two host species. Coccidian species are mainly identified by their morphology and the predilection site within the host’s alimentary tract. At one time, it was thought the species in goats and sheep were the same, but cross transmission studies have shown that the coccidia are host-specific. Currently, 11 coccidian species are recognised in sheep and nine in goats. Two sheep species are known to be highly pathogenic and these two parasites inhabit both the small and large intestine. Much less work has been undertaken on goat coccidia, although it is considered that several Eimeria species might be pathogenic. Often, clinical signs in sheep and goats are limited and mild, but it is common for animals to decrease their weight gain or even lose weight. The faeces may alter and there may be diarrhoea. Whilst there are production losses, there has been little quantification in sheep or goats. Moreover, infested animals appear more susceptible to other infections. Diagnosis is often more difficult than it seems. Because of problems, this has resulted in suggestions that the diagnosis of coccidiosis should be based on a number of parameters: epidemiology, clinical signs, oocyst counts in faecal samples, pathological findings and, finally, clinical response to treatment. There are several preparations licensed in the United Kingdom for sheep, but none for goats. There are also several management factors which can assist in control of the disease, but often medication has to be used to prevent the disease. © 2012 Published by Elsevier B.V.
1. Introduction Coccidia, the causative agents of coccidiosis, are protozoa within the Class Sporozoasida, in the Family Eimeriidae. They ultimately produce oocysts, which can then infect other animals. The life cycle is complex and involves both sexual and asexual stages. One ingested oocyst can produce many millions of oocysts. Almost all young sheep and
夽 This paper is part of the special issue entitled “Lectures of the 1st European Conference on Small Ruminant Health Management”, held in Athens, Greece, October 2011. Guest Edited by G.C. Fthenakis. E-mail address: [email protected] 0921-4488/$ – see front matter © 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.smallrumres.2012.11.011
goats will become infested with coccidia, usually within their first 6 months of life. 2. The disease 2.1. Aetiology It was originally thought that the coccidian species in goats and sheep were the same. However, cross-infection studies have shown that coccidia are species-specific, which also means that they do not cause zoonoses. Thus, it appears that cross infections between sheep and goats do not occur. The species are distinguished by their morphology and their predilection sites within the host’s gut.
94
A.H. Andrews / Small Ruminant Research 110 (2013) 93–95
Table 1 The main coccidian species found in sheep faeces (Joyner et al., 1966). Species
Proportion of animals in which found (%)
Eimeria arloingi (now E. ovina) E. crandallis E. ninakohlyakimovae (now E. ovinoidalis) E. faurei E. arsata E. .parva E. pallida
95 90 88 72 62 57 37
In general, the more pathogenic species tend to inhabit the posterior part of the intestines (Taylor, 2012). Currently, at least 11 species are found in sheep and 9 species are in goats. In sheep, there are two species that are known to be highly pathogenic, namely Eimeria crandallis (prepatent period: 15–20 days) and Eimeria ovinoidalis (prepatent period: 12–15 days). Both species have parasitic stages that infest the small and large intestine, thereby potentially causing a large area of damage. Initially sheep coccidia were not considered pathogenic, and it was not until the 1960s that the disease was considered a problem in Great Britain (Table 1). There has been considerably less work undertaken on coccidian species in goats, but it is considered that several are probably pathogenic (Table 2). Eimeria arloingi causes polyp formation and focal mucosal hyperplasia, Eimeria ninakohlyakimovae and Eimeria caprina cause much mucosal destruction in small and large intestines and Eimeria christenseni and Eimeria hirci are also probably pathogenic. 2.2. Clinical significance The signs of infestation are often minimal and in the majority of animals they can be inapparent. However, it is common for there to be some degree of inappetance or anorexia, but it is often difficult to detect. There is also a reduction in weight gain, loss of weight or animals being static in their growth. Sometimes, faecal pellets are softer than normal or the stools are not pelleted or there is diarrhoea. Usually, there is no blood in the faeces or tenesmus. Occasionally, deaths can occur. Goats often react to pathogens in a more severe and prolonged way and immunity and resistance to infestation can be slow to build up. In both infested sheep and goats immunity can be lowered and result in concurrent parasitic infestations, such as parasitic gastroenteritis, nematodirosis or haemonchosis,
Proportion of animals where most common species (%) 42 29 19 2.0 – 5.0 3.0
whilst any faecal staining can lead to fly strike. Vitamin and mineral disturbances can occur due to poor alimentary function and absorption and respiratory and other infections are more common due to lowered immunity. There are production losses, although the author is unaware of their full quantification in sheep or goats. However, in growing cattle, work has shown there was a loss in their growth and this weight difference continued for over 10 months even when the cattle were again challenged later on and also following turnout. Thus, in some animals any weight difference at the time of infestation between affected and unaffected animals may be maintained for a long period. 2.3. Diagnosis This can be difficult and Andrews (2004) has provided an indication of criteria to diagnose coccidiosis. This is because diagnosis is often based on oocyst counts, which are often high for a much shorter period than the duration of any faecal change. Thus, any definitive diagnosis should involve several factors including epidemiology (age, number affected, mortality) and clinical signs present (De Waal, 2012). Faecal sampling should consist of 5 samples collected per 20 affected animals and should always include samples from some apparently healthy animals. Usually one or more samples containing >5000 oocysts per gram with clinical signs present in the respective animals, indicate probable infestation. Speciation confirms the involvement of pathogenic strains, but is expensive. Gross pathological examination can reveal chronic inflammation and thickening of large intestines and/or caecum, haemorrhages on the mucosal surface, white dots in small intestine; on histological examination, there is evidence of loss of mucosal surface, villous atrophy, mucosal scrapes with numerous oocysts and gamonts. Finally, the response to treatment can be used diagnostically, but it must be remembered that the
Table 2 The main coccidian species found in goat faeces (Lloyd, 1994). Species
Proportion of animals in which found (%)
Species dominance
Species pathogenicity
Eimeria arloingi E. christenseni E. hirci E. caprina E. ninakohlyakimovae E. .alijevi E. apsheronica E. jolchijevi E. caprovina
95 73 67 58 51 39 26 6 4
++++ ++
+ + +++ + (?) +++++
A.H. Andrews / Small Ruminant Research 110 (2013) 93–95
treatments can also affect other potential pathogens and organisms, as well as act as growth promoters. The main differential diagnoses are for causes of diarrhoea in growing lambs and kids and include parasitic gastroenteritis, nematodirosis and some deficiencies. 2.4. Control Several methods of treatment are available and licensed in different EU countries. There are differences in the ways products are used. However, which therapeutic agent is decided upon does depend on the stage of infestation, efficacy, ease of administration and expense. In the United Kingdom 3 products are licensed for sheep, but none for goats. Decoquinate is used as a premix (powder 60 g decoquinate kg−1 ) at a dose rate of 1.67 kg premix tonne−1 feed, producing 100 mg kg−1 feed when fed on an unrestricted basis, and it should be administered for 28 days. The calculation is based on 100 g feed intake 10 kg−1 bodyweight (bw). However, if the lamb feed is restricted, then at 75 g feed 10 kg−1 bw the concentration is 2.22 kg tonne−1 feed and at 50 g feed 10 kg−1 bw, it is 3.34 kg tonne−1 feed. The feed can be pelleted, if the feed is preconditioned, for up to 10 min at a temperature not over 80 ◦ C. The decoquinate is stable in the finished feed for up to 3 months. The medicated feed may be continued, if the risk of disease is prolonged beyond this period. Decoquinate should not be used in sheep producing milk for human consumption. Where feed incorporation is difficult or there may be problems with ensuring feeding decoquinate for the required length of time, then there are two drenches available. Diclazuril is used as an oral suspension (2.5 mg diclazuril mL−1 ) at a single dose of 1 mg kg−1 bw (1 mL 2.5 kg−1 bw). If infestation pressure is high, then a second dose may be given after about 3 weeks. Diclazuril has a zero withdrawal time for meat. Diclazuril has a coccidiocidal effect for some coccidian species, but, usually, it would reduce oocyst shedding for up to 14 days. Toltrazuril is used as an oral suspension (50 mg toltrazuril mL−1 ) at 20 mg kg−1 bw (0.4 mL kg−1 bw) and again as a single dose. Best benefit is obtained by dosing in the pre-patent period, before signs develop. All animals within a group or pen should be treated at the same time. Toltrazuril should not be used in sheep producing milk for human consumption and the meat and offal withdrawal time is 42 days. It is active against all intracellular asexual and sexual stages of the parasite and is coccidiocidal. In kids and goats, under the ‘cascade’ regulations, the same general principles should be observed. However, the withdrawal time must be specified by the veterinary surgeon prescribing and must be at least equal to the statutory minimum withdrawal period.
95
The lambs/kids should not be overcrowded whether indoors or outside and all parturition pens must be kept clean and dry, with all bedding quickly removed to prevent oocysts sporulating. All animals should have water and feed troughs and bowls off the ground, and must be kept clean and free from faecal contamination; area around troughs should be as dry as possible. Pastures used for young animals should be rotated. Despite good management, it may be necessary to use prophylactic treatments in the feed or by drench. It is generally suggested that such preventative treatments should be carried out about a week to 10 days before signs are anticipated to develop. The problem with the advice is predicting this time, so if infestation is minimal or absent, treatment will have a minimal effect. Oral doses of diclazuril and toltrazuril are as for treatment. However, decoquinate inclusion rate in feed is halved (833 g of premix/tonne of feed providing a recommended concentration of 50 mg kg−1 feed). If feed is restricted (based on less than 500 g feed intake/50 kg bw), then decoquinate levels should be increased to provide a target intake of 0.5 mg kg−1 bw. Whatever is done, attention should be paid to providing clean and dry conditions, with high quality feed and low stocking densities. 3. Concluding remarks Whilst coccidiosis is a commonly recognised and diagnosed disease, our knowledge of many of its basic aspects is poor. Thus, although some of the apparent rise in incidence of clinical signs is due to management, this cannot be the full cause for the increase. Also, in many instances when detailed studies are carried out, there are other problems besides that of coccidiosis present in the farm. Again, more work and understanding of the interaction of coccidial infections with other diseases is required. Considering how ubiquitous, coccidial infestations are in sheep and goats, almost all recent research appears to have been focussed on the development of new treatments and the fundamental problems still remain unsolved. Conflict of interest statement None. References Andrews, A.H., 2004. The diagnosis of clinical coccidiosis in calves. UK Vet 9, 45–47. De Waal, T., 2012. Advances in diagnosis of protozoan diseases. Vet. Parasitol. 189, 44–51. Joyner, L.F., Norton, C.C., Davies, S.F.M., Watkins, C.V., 1966. The species of coccidia occurring in cattle and sheep in the South West of England. Parasitology 56, 531–541. Lloyd, S., 1994. Parasitology in goats. Protozoal parasites. Goat Vet. Soc. J. 15, 144–161. Taylor, M.A., 2012. Emerging parasitic diseases of sheep. Vet. Parasitol. 189, 2–7.
Contents lists available at SciVerse ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Some aspects of coccidiosis in sheep and goats夽 A.H. Andrews Acorn House, 25, Mardley Hill, Welwyn, Hertfordshire AL6 0TT, United Kingdom
a r t i c l e
i n f o
Article history: Available online 14 December 2012 Keywords: Coccidiosis Eimeria Kid Lamb Oocyst
a b s t r a c t This paper provides a brief review of the widespread and economically important disease of coccidiosis. At one time, coccidia were considered to be virtually non pathogenic, but by the 1960s they were recognised to cause disease. Almost all young lambs and kids will be exposed and become infested during their early life and there are similarities and differences between the two host species. Coccidian species are mainly identified by their morphology and the predilection site within the host’s alimentary tract. At one time, it was thought the species in goats and sheep were the same, but cross transmission studies have shown that the coccidia are host-specific. Currently, 11 coccidian species are recognised in sheep and nine in goats. Two sheep species are known to be highly pathogenic and these two parasites inhabit both the small and large intestine. Much less work has been undertaken on goat coccidia, although it is considered that several Eimeria species might be pathogenic. Often, clinical signs in sheep and goats are limited and mild, but it is common for animals to decrease their weight gain or even lose weight. The faeces may alter and there may be diarrhoea. Whilst there are production losses, there has been little quantification in sheep or goats. Moreover, infested animals appear more susceptible to other infections. Diagnosis is often more difficult than it seems. Because of problems, this has resulted in suggestions that the diagnosis of coccidiosis should be based on a number of parameters: epidemiology, clinical signs, oocyst counts in faecal samples, pathological findings and, finally, clinical response to treatment. There are several preparations licensed in the United Kingdom for sheep, but none for goats. There are also several management factors which can assist in control of the disease, but often medication has to be used to prevent the disease. © 2012 Published by Elsevier B.V.
1. Introduction Coccidia, the causative agents of coccidiosis, are protozoa within the Class Sporozoasida, in the Family Eimeriidae. They ultimately produce oocysts, which can then infect other animals. The life cycle is complex and involves both sexual and asexual stages. One ingested oocyst can produce many millions of oocysts. Almost all young sheep and
夽 This paper is part of the special issue entitled “Lectures of the 1st European Conference on Small Ruminant Health Management”, held in Athens, Greece, October 2011. Guest Edited by G.C. Fthenakis. E-mail address: [email protected] 0921-4488/$ – see front matter © 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.smallrumres.2012.11.011
goats will become infested with coccidia, usually within their first 6 months of life. 2. The disease 2.1. Aetiology It was originally thought that the coccidian species in goats and sheep were the same. However, cross-infection studies have shown that coccidia are species-specific, which also means that they do not cause zoonoses. Thus, it appears that cross infections between sheep and goats do not occur. The species are distinguished by their morphology and their predilection sites within the host’s gut.
94
A.H. Andrews / Small Ruminant Research 110 (2013) 93–95
Table 1 The main coccidian species found in sheep faeces (Joyner et al., 1966). Species
Proportion of animals in which found (%)
Eimeria arloingi (now E. ovina) E. crandallis E. ninakohlyakimovae (now E. ovinoidalis) E. faurei E. arsata E. .parva E. pallida
95 90 88 72 62 57 37
In general, the more pathogenic species tend to inhabit the posterior part of the intestines (Taylor, 2012). Currently, at least 11 species are found in sheep and 9 species are in goats. In sheep, there are two species that are known to be highly pathogenic, namely Eimeria crandallis (prepatent period: 15–20 days) and Eimeria ovinoidalis (prepatent period: 12–15 days). Both species have parasitic stages that infest the small and large intestine, thereby potentially causing a large area of damage. Initially sheep coccidia were not considered pathogenic, and it was not until the 1960s that the disease was considered a problem in Great Britain (Table 1). There has been considerably less work undertaken on coccidian species in goats, but it is considered that several are probably pathogenic (Table 2). Eimeria arloingi causes polyp formation and focal mucosal hyperplasia, Eimeria ninakohlyakimovae and Eimeria caprina cause much mucosal destruction in small and large intestines and Eimeria christenseni and Eimeria hirci are also probably pathogenic. 2.2. Clinical significance The signs of infestation are often minimal and in the majority of animals they can be inapparent. However, it is common for there to be some degree of inappetance or anorexia, but it is often difficult to detect. There is also a reduction in weight gain, loss of weight or animals being static in their growth. Sometimes, faecal pellets are softer than normal or the stools are not pelleted or there is diarrhoea. Usually, there is no blood in the faeces or tenesmus. Occasionally, deaths can occur. Goats often react to pathogens in a more severe and prolonged way and immunity and resistance to infestation can be slow to build up. In both infested sheep and goats immunity can be lowered and result in concurrent parasitic infestations, such as parasitic gastroenteritis, nematodirosis or haemonchosis,
Proportion of animals where most common species (%) 42 29 19 2.0 – 5.0 3.0
whilst any faecal staining can lead to fly strike. Vitamin and mineral disturbances can occur due to poor alimentary function and absorption and respiratory and other infections are more common due to lowered immunity. There are production losses, although the author is unaware of their full quantification in sheep or goats. However, in growing cattle, work has shown there was a loss in their growth and this weight difference continued for over 10 months even when the cattle were again challenged later on and also following turnout. Thus, in some animals any weight difference at the time of infestation between affected and unaffected animals may be maintained for a long period. 2.3. Diagnosis This can be difficult and Andrews (2004) has provided an indication of criteria to diagnose coccidiosis. This is because diagnosis is often based on oocyst counts, which are often high for a much shorter period than the duration of any faecal change. Thus, any definitive diagnosis should involve several factors including epidemiology (age, number affected, mortality) and clinical signs present (De Waal, 2012). Faecal sampling should consist of 5 samples collected per 20 affected animals and should always include samples from some apparently healthy animals. Usually one or more samples containing >5000 oocysts per gram with clinical signs present in the respective animals, indicate probable infestation. Speciation confirms the involvement of pathogenic strains, but is expensive. Gross pathological examination can reveal chronic inflammation and thickening of large intestines and/or caecum, haemorrhages on the mucosal surface, white dots in small intestine; on histological examination, there is evidence of loss of mucosal surface, villous atrophy, mucosal scrapes with numerous oocysts and gamonts. Finally, the response to treatment can be used diagnostically, but it must be remembered that the
Table 2 The main coccidian species found in goat faeces (Lloyd, 1994). Species
Proportion of animals in which found (%)
Species dominance
Species pathogenicity
Eimeria arloingi E. christenseni E. hirci E. caprina E. ninakohlyakimovae E. .alijevi E. apsheronica E. jolchijevi E. caprovina
95 73 67 58 51 39 26 6 4
++++ ++
+ + +++ + (?) +++++
A.H. Andrews / Small Ruminant Research 110 (2013) 93–95
treatments can also affect other potential pathogens and organisms, as well as act as growth promoters. The main differential diagnoses are for causes of diarrhoea in growing lambs and kids and include parasitic gastroenteritis, nematodirosis and some deficiencies. 2.4. Control Several methods of treatment are available and licensed in different EU countries. There are differences in the ways products are used. However, which therapeutic agent is decided upon does depend on the stage of infestation, efficacy, ease of administration and expense. In the United Kingdom 3 products are licensed for sheep, but none for goats. Decoquinate is used as a premix (powder 60 g decoquinate kg−1 ) at a dose rate of 1.67 kg premix tonne−1 feed, producing 100 mg kg−1 feed when fed on an unrestricted basis, and it should be administered for 28 days. The calculation is based on 100 g feed intake 10 kg−1 bodyweight (bw). However, if the lamb feed is restricted, then at 75 g feed 10 kg−1 bw the concentration is 2.22 kg tonne−1 feed and at 50 g feed 10 kg−1 bw, it is 3.34 kg tonne−1 feed. The feed can be pelleted, if the feed is preconditioned, for up to 10 min at a temperature not over 80 ◦ C. The decoquinate is stable in the finished feed for up to 3 months. The medicated feed may be continued, if the risk of disease is prolonged beyond this period. Decoquinate should not be used in sheep producing milk for human consumption. Where feed incorporation is difficult or there may be problems with ensuring feeding decoquinate for the required length of time, then there are two drenches available. Diclazuril is used as an oral suspension (2.5 mg diclazuril mL−1 ) at a single dose of 1 mg kg−1 bw (1 mL 2.5 kg−1 bw). If infestation pressure is high, then a second dose may be given after about 3 weeks. Diclazuril has a zero withdrawal time for meat. Diclazuril has a coccidiocidal effect for some coccidian species, but, usually, it would reduce oocyst shedding for up to 14 days. Toltrazuril is used as an oral suspension (50 mg toltrazuril mL−1 ) at 20 mg kg−1 bw (0.4 mL kg−1 bw) and again as a single dose. Best benefit is obtained by dosing in the pre-patent period, before signs develop. All animals within a group or pen should be treated at the same time. Toltrazuril should not be used in sheep producing milk for human consumption and the meat and offal withdrawal time is 42 days. It is active against all intracellular asexual and sexual stages of the parasite and is coccidiocidal. In kids and goats, under the ‘cascade’ regulations, the same general principles should be observed. However, the withdrawal time must be specified by the veterinary surgeon prescribing and must be at least equal to the statutory minimum withdrawal period.
95
The lambs/kids should not be overcrowded whether indoors or outside and all parturition pens must be kept clean and dry, with all bedding quickly removed to prevent oocysts sporulating. All animals should have water and feed troughs and bowls off the ground, and must be kept clean and free from faecal contamination; area around troughs should be as dry as possible. Pastures used for young animals should be rotated. Despite good management, it may be necessary to use prophylactic treatments in the feed or by drench. It is generally suggested that such preventative treatments should be carried out about a week to 10 days before signs are anticipated to develop. The problem with the advice is predicting this time, so if infestation is minimal or absent, treatment will have a minimal effect. Oral doses of diclazuril and toltrazuril are as for treatment. However, decoquinate inclusion rate in feed is halved (833 g of premix/tonne of feed providing a recommended concentration of 50 mg kg−1 feed). If feed is restricted (based on less than 500 g feed intake/50 kg bw), then decoquinate levels should be increased to provide a target intake of 0.5 mg kg−1 bw. Whatever is done, attention should be paid to providing clean and dry conditions, with high quality feed and low stocking densities. 3. Concluding remarks Whilst coccidiosis is a commonly recognised and diagnosed disease, our knowledge of many of its basic aspects is poor. Thus, although some of the apparent rise in incidence of clinical signs is due to management, this cannot be the full cause for the increase. Also, in many instances when detailed studies are carried out, there are other problems besides that of coccidiosis present in the farm. Again, more work and understanding of the interaction of coccidial infections with other diseases is required. Considering how ubiquitous, coccidial infestations are in sheep and goats, almost all recent research appears to have been focussed on the development of new treatments and the fundamental problems still remain unsolved. Conflict of interest statement None. References Andrews, A.H., 2004. The diagnosis of clinical coccidiosis in calves. UK Vet 9, 45–47. De Waal, T., 2012. Advances in diagnosis of protozoan diseases. Vet. Parasitol. 189, 44–51. Joyner, L.F., Norton, C.C., Davies, S.F.M., Watkins, C.V., 1966. The species of coccidia occurring in cattle and sheep in the South West of England. Parasitology 56, 531–541. Lloyd, S., 1994. Parasitology in goats. Protozoal parasites. Goat Vet. Soc. J. 15, 144–161. Taylor, M.A., 2012. Emerging parasitic diseases of sheep. Vet. Parasitol. 189, 2–7.