Common Causative Agents of Calf Scours

Common causative agents of calf scours can be broken down into three groups; viral, bacterial and parasites.

All of these agents are contracted orally and cause calf scours in the first month. Definitive diagnosis by fecal float, bacterial culture, and detection of viral DNA is usually required to determine which agent is involved.

Types of Viral:

  • Rotavirus
  • Coronavirus

Types of Bacteria:

  • E. coli
  • Clostridium perfringens
  • Salmonella

Types of Parasites:

  • Cryptosporidium
  • Coccidiosis

Multiple Causative Agents

  • A Rota or Corona viral infection will not respond to antibiotic treatment, but the severe damage done to the intestinal wall often results in a secondary bacterial infection.
  • Clostridial enteritis caused by Clostridium perfringens is actually the result of a poison produced by the bacteria. Antibiotics may kill the bacteria, but have no effect on the preformed toxins and an antitoxin may be required.
  • Antibiotics may also have no effect on the parasitic agents of scours.  A parasiticide such as Amprolium for coccidiosis may be required.

Age and symptoms of Infection

  • The consistency or color of the manure is not a good indicator of the organisms involved but age of infection can give you information on what organism is involved
  • Rota and Corona virus and Cryptosporidium parvum usually occur between 7-21 days old with watery diarrhea and may contain blood but not always
  • E. coli (K99 enterotoxigenic form) occurs within the first 3 days of life and the calf usually becomes septic and dies before many symptoms arise.
  • Coccidiosis from Eimeria sp. occurs after 20 days old and presents as a dark and bloody water diarrhea.  Calves lose weight rapidly but death is rare unless symptoms persist for over a week.
  • Salmonellosis can occur at any time but Salmonella dublin usually presents itself as pneumonia around 2-3 weeks old.  Many calves die or become chronic pneumonia cases.
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