Neonatal diarrhoea is the main infectious disease occurring within the first month of life of calves and its harmful effects extend until the first lactation. Of the various infectious agents that cause calf scours, cryptosporidiosis is probably the most important across European farms due to its prevalence, ubiquity, resistance in the environment, and low infective dose.
Cryptosporidiosis is a leading cause of neonatal calf diarrhoea
Among the germs inducing neonatal diarrhoea in calves, cryptosporidiosis caused by C. parvum is found in 36% to 71.99% of cases, both alone or in combination with other agents. As a sole agent, it is found in 18% to 52.6% of cases1-3. Therefore, cryptosporidiosis can be considered the main cause of neonatal diarrhoea in calves. This is due to several reasons:
- its scope of action ranging from 5 to 28 days of age ; in comparison, enterotoxigenic E. coli affects calves under 5-7 days, rotavirus under 15 and coronavirus under 21 days,
- crypto probably increases the severity and mortality of diarrhoea when associated with other viruses and bacteria,
- diarrhoeic calves usually excrete large numbers of oocysts (up to 107 oocysts per gram)
- the minimal infectious dose is very low, as few as 10 oocysts are needed to induce diarrhoea
- its long persistence in the environment due to its high resistance to climatic conditions and disinfectants4.
Cryptosporidiosis is highly prevalent in European calves
The prevalence of cryptosporidiosis in European farms is extremely high, from 90% to 100% of farms5-10, explaining why the disease can be considered endemic in Europe. Prevalence among calves is also high, with most of the studies reporting a prevalence of 20 to 40%1, 5, with some that exceed 70%2. While there are fewer studies in beef farms, the results are similar: 36.7% of calves can be considered infected in 97% of herds6. Organic farms are also affected by cryptosporidiosis. In Sweden, prevalence of cryptosporidiosis in calves was 44.7% in organic farms compared to 52.3% in conventional farms11. In France, a study recently reported that 40.2% of calves from 20 organic farms tested positive for C. parvum, like classically reared calves12. Varying figures can be found across studies. This is fundamentally due to differences in the sensitivity of the diagnostic method used and the age of the calves. The highest positive results are usually obtained when PCR methods are used in 1- to 3-week-old calves.
C. parvum is the dominant species in suckling calves
There are about 40 species of the genus Cryptosporidium, of which at least 4 are found in cattle13, 14, with C. parvum being predominantly detected in suckling calves and causing severe disease15. Although C. bovis, C. andersoni and C. ryanae have been identified in faeces of calves older than two months, their pathogenicity is low16,17. On the contrary, C. parvum is always identified in calves under one month of age and no longer, because immunity develops with age, except in immunocompromised animals.
Relative prevalence of Cryptosporidium spp. in calf producing farms in Germany15
Cryptosporidiosis caused by C. parvum is zoonotic and cattle are the main reservoir for human infection
Cryptosporidiosis is also an important cause of diarrhoea in humans, especially in children and chronic diarrhoea in immunocompromised adults18. In Europe, the infection is mainly acquired through recreational waters (in swimming pools, public paddling pools, water parks or open waters, as well as at mass sporting events involving water or mud) and contact with animals. C. parvum and C. hominis are responsible for most cases of cryptosporidiosis in people, with cattle representing an important reservoir for zoonotic subtypes of C. parvum. Transmission is faecal-oral, primarily by contact with calves or infected people, or can be airborne19, 20. In 2018, 11,418 confirmed cases of cryptosporidiosis were reported in 21 EU countries, with ratios per 100,000 population of 4.4 cases, rising to 15.8 in children under 4 years of age. The UK, Germany, the Netherlands, and Spain accounted for 76% of these cases and Belgium, Finland, Iceland, and the Netherlands report an increase in cases. The disease is probably underdiagnosed22.
Cryptosporidium parvum, the causative agent of calf cryptosporidiosis, is a major contributor to calf diarrhoea in Europe that is found in most calves and farms, regardless of the type of production: dairy, beef, intensive, extensive, conventional, or organic. In addition, cattle function as the reservoir of human cryptosporidiosis caused by C. parvum, which inflicts acute diarrhoea, especially in infants, and chronic diarrhoea in immunosuppressed patients. Because of the importance of cryptosporidiosis for human and animal health (One Health), its diagnosis and control in ruminant farms is essential.
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