Cryptosporidiosis in calves
What is the problem?
Diarrhea in calves is still a very important pathogen for the modern dairy industry as it is responsible for 57% of young animal losses. Furthermore, diarrhea causes reduced growing performance in calves, which has a long-lasting effect on future lactations.
In neonatal calves, there are four main pathogens to cause diarrhea: E. coli, rotavirus, coronavirus and cryptosporidia. Mixed infections with multiple of these pathogens are common. In recent years, cryptosporidiosis has gained in importance and is now the most challenging form of diarrhea in newborn calves, as there is no vaccination available and prevention of cryptosporidia has shown to be difficult.
What are cryptosporidia?
Cryptosporidia are unicellular parasites that infect the cells of the gastrointestinal tract. There are many species of cryptosporidia that can infect many kinds of animals. In calves, Cryptosporidium parvum is by far the most significant species.
C. parvum is a non-host-specific pathogen, which means that apart from calves it can also infect other animals, including humans. In humans, an infection with cryptosporidia is usually much less severe than in calves and rarely lasts longer than a week. Nevertheless, this should be considered when treating cryptosporidiosis in calves
What happens in the calf?
An infection with cryptosporidia starts with the ingestion of so-called oocysts. Oocysts can be compared to an egg that is extremely resistant to environmental impacts and can survive for up to one year in the calf’s environment. When these oocysts enter the calf’s gastrointestinal tract via food or bedding, they hatch and nest in the intestinal mucosa. Once incorporated by the intestinal cells, cryptosporidia start to multiply and to infect further cells. After several stages of development, the cryptosporidia form new oocysts that are excreted to the environment to infect further animals.
How can cryptosporidiosis be prevented?
Cryptosporidiosis is a widespread problem in newborn calves that mainly affects calves with a poor immune system. Therefore, good colostrum management is essential. In general, this means from the 1st milking 2 – 3 liters should be fed within the first 2 hours after birth. Within the first 12 hours after birth, another 2 liters should be given. The colostrum should contain at least 50 g IgG/liter, which can easily be checked using a colostrometer or refractometer.
The second pillar of cryptosporidia prevention is hygiene in the calving box and calf hut. If possible, the calving box should be mucked out after each calving. Also, the use of the calving box as a sick box is to be rejected urgently. Both measures considerably reduce the pathogen pressure on the calf. Calf huts should also be kept clean and dry. Before the calf huts are re-occupied, they should be thoroughly cleaned and disinfected. When disinfecting, care must be taken to the fact that cryptosporidia are resistant to many disinfectants. Disinfectants that are suitable for destroying cryptosporidia and other unicellular parasites usually state this.
Furthermore, feed additives that stabilize gut health and improve gut integrity can help to prevent cryptosporidiosis, as it requires much higher numbers of cryptosporidia to establish an infection in a healthy gut compared to a gut with preexisting disorders. If a calf has fallen sick, it is most important to keep the milk uptake high, as water and energy loss from the gut must be compensated to reduce the impact of diarrhea. Bitter substances have proven to improve milk intake in calves, even during diarrhea.