Impact of Cryptosporidium and Giardia on Calf Health

Impact of Cryptosporidium and Giardia on Calf Health

Cryptosporidium and Giardia are both protozoan species that affect a wide range of animals, including people. Both organisms are prevalent in dairy and beef herds and can negatively impact the health and productivity of young calves.



Data from the National Animal Health Monitoring System (NAHMS) helps us to understand just how large the impact cryptosporidium has on the livestock industry. 

Dairy: 2014 survey of 2,323 fecal samples found 43.1% of samples to test positive for Crypto.

  • Pre-weaned calves are most susceptible and usually break between 7-21 days of age.
  • Crypto is more likely to be shed in the summer months when the temperature-humidity index (THI) is >70.
  • Cryptosporidium is more prevalent on farms >500 cows.
  • Calves most likely to shed Crypto are between the ages of 3-13 days. Older calves may be less likely to shed the organism as they develop immunity.
  • Estimated that Crypto has infected over 90% of U.S.A. dairy farms.
  • Cryptosporidium is resistant to many disinfectants and is resistant to drying and freezing.

Beef: 1992-1993 NAHMS Beef Cow/Calf Health and Productivity Audit (CHAPA) found that just over 20% of samples collected from calves with diarrhea tested positive for Cryptosporidium.

  • 8% of farms submitting samples from calves that did not have diarrhea had at least one test positive.
  • Crypto was most common in calves 30 days of age and younger.
  • Calves did not have to have diarrhea to test positive.



NAHMS data also helps us to understand the impact Giardia has on the livestock industry.

Dairy: 2014 survey found 1/3 of all fecal samples collected to be positive for Giardia cysts.

  • Giardia infects nearly all dairy calves, but rarely results in clinical disease.
  • Failure of passive transfer makes calves more likely to be infected with Giardia.
  • Calves testing positive for Giardia had lower ADG than those testing negative.
  • Giardia tends to be more of a chronic type of infection compared to Cryptosporidium.

Beef: 26.9% of samples from diarrheic calves and 45.9% of samples from nondiarrheic calves tested positive for Giardia during the 1992-93 CHAPA audit.

  • Calves do not need to have diarrhea to shed Giardia.
  • Over 90% of operations with no calves having diarrhea had at least one calf test positive for Giardia.
  • Fecal samples from 31-60 days of age were most likely to be positive for Giardia.


Cryptosporidium and Giardia appear to be common within both dairy and beef herds whether calves show signs of diarrhea or not. Fecal shedding of both species is related to the age of the animal, older animals are less likely to shed than young calves. Infection can negatively impact growth of the animal, NAHMS data reports calves testing positive for either organism gained 0.066 lb/d (0.03 kg/d) less than calves testing negative.

At some point most dairy and beef producers will run into an outbreak of one of these organisms. Both organisms are resistant to common disinfectants, drying, heat and cold. A lack of drugs or “cure” to treat infectious outbreaks makes control challenging. For now, the best approach is to implement protocols for proper hygiene and housing to keep infections at bay or at least manageable.

As someone speaking from experience, I also want to note that these organisms can be passed on to humans. When you yourself or employees are dealing with infected animals, please be sure to implement proper handwashing and other hygiene protocols to prevent the spread of disease.

In the near future we hope that we have more tools in our toolbox to help producers deal with organisms like Cryptosporidium and Giardia.


Written by: Mariah Gull, M.S.




Average Daily Gain in Preweaned Holstein Heifer Calves NAHMS 2014 (

Presence of Cryptosporidium and Giardia In Preweaned Dairy Calves Dairy 2014 (

CHAPA_is_Crypto.pdf (

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