The type of pathogen that can cause scours will largely depend on the calf’s age, and knowing which one is important
Disease is like a hydra with many tendrils, and each should be identified for the best treatment.
In the case of calf scours, the age of the animal, environmental factors and different bugs may contribute to debilitating diarrhea.
“It makes a lot of sense to have your diagnosis in mind because you can have direct treatments. If it is a virus that is causing the diarrhea, then an antibiotic is not going to help anything,” said Dr. Jamie Rothenburger, a pathologist at the University of Calgary’s faculty of veterinary medicine.
“The type of pathogen that can cause scours will depend on the age of the calf. Sometimes these infections are not single infections. Sometimes there are multiple pathogens working together. Those calves that have co-infections tend to do more poorly.”
Veterinarians may send her lab samples of diarrhea or they may send her entire calves that can be necropsied for a full investigation of internal damage, pneumonia symptoms or microscopic analysis of bugs that may cause scours or other infections.
“We need to use multiple angles of evidence to come to a conclusion,” she said.
There is also a concern for human health if cryptosporidium or salmonella caused infection in the calves.
“Until you know what the cause is, there is a potential for people to get sick as well,” she said.
“Farmers with scouring calves have to be really careful with hygiene, hand washing and changing their clothes and monitoring at risk people who are working with those animals.”
Infections may present similar symptoms, said veterinarian Roy Lewis of Merck Animal Health.
“Cyrptosporidium sometimes catches people off guard. It is very similar to coccidiosis,” he said.
“Once one gets it, pretty soon they all get it.”
Cows can be vaccinated for a range of infections before calving. Lewis advises producers who buy bred heifers to ask what scours vaccine was provided. If none, they should be isolated from the rest of the herd.
Pregnant cows are vaccinated two and six weeks before calving to stimulate antibodies that can be delivered through colostrum. It is important to make sure the calves are sucking and receiving adequate colostrum within the first 12 hours of life.
A calf’s gut is immature, and fluid is lost and energy depleted when attacked by an infection. A calf’s weight is approximately 70 percent water at birth, so the loss of body fluids through diarrhea produces the rapid dehydration.
E. coli, Salmonella spp., coronavirus, rotavirus, cryptosporidium and coccidian are the main causes of diarrhea, according to the Merck Veterinary Manual.
E.coli is the leading cause of diarrhea in calves during the first week of life and produces two distinct types of diarrhea because of the way the infection affects the intestine.
Diarrhea due to enterotoxigenic (K99-bearing) E. coli is seen in calves younger than three to five days. Onset is sudden, and profuse amounts of liquid feces are passed. The calves go down hill quickly and can lose more than 12 percent of their bodyweight in fluid. Death can occur, but if fluid and electrolyte therapy is administered early, response is usually good.
Salmonella spp, especially S Typhimurium and S Dublin, cause diarrhea in two- to 12-week-old calves. These cause intestinal inflammation. There may be watery stools that are brown, green, yellow or grey. There may be flecks of blood or mucous. The feces are foul smelling.
Calves can lose weight rapidly and often die despite vigorous therapy.
Rotavirus is the most common viral cause of diarrhea and appears in youngsters four to 15 days of age, although it can also affect older calves. Groups A and B rotavirus are involved, but Group A is most prevalent. Feces are voluminous, and diarrhea can persist for several days.
Cases of viral diarrhea that are uncomplicated by other pathogens commonly respond within a few days to fluid and electrolyte therapy and adequate nutrition. Along with coronavirus, they affect a calf’s immune system and may allow other pathogens to cause further sickness.
Coronavirus is also commonly associated with diarrhea in seven- to 30-day-old calves. It replicates in the epithelium of the upper respiratory tract and in the enterocytes of the intestine, where it produces similar lesions to rotavirus but also infects the epithelial cells of the large intestine.
Cryptosporidium parvum is a common cause of diarrhea in five- to 35-day-old calves. It is a protozoon that adheres to the surface of the small intestine and the colon, causing internal damage. The major signs are diarrhea, dehydration and weakness.
Diarrhea can be mild, but the severity may be related to the general strength of the calf and intensity of challenge of the disease.
How to reduce scours occurrence
- Calve heifers in a separate area from older cows. Heifers’ calves tend to have lower immunity levels.
- Avoid wet calving areas. One of the primary causes of scours is wet, muddy and cold conditions. Wet conditions favour survival of disease-causing agents. When the cows lie down, whatever is on the ground comes in contact with the udder and can be taken in by the calf when it nurses.
- Provide portable calf shelters on pasture to keep calves dry and protect them from cold winds.
- If the calving area is small, turn the pairs out to a clean pasture as soon as possible.
- Isolate scouring calves and treat immediately to prevent the spread of disease.
- Vaccinate pregnant cows six and three weeks before calving.
- Provide fluids and electrolytes to scouring calves to prevent dehydration. Dehydrated calves develop sunken eyes, and the bony shoulders, hips and ribs may be more prominent.
- Fluids are essential, but the gut cannot absorb them unless electrolytes (salts) are provided in the proper proportions. Scouring calves should receive at least 10 percent of body weight of fluids and electrolytes if scouring is mild, and more if it is severe.
- Use a high quality electrolyte mixture administered with a stomach tube, twice daily. Don’t mix the fluid and electrolytes with milk because it will cause the milk to curdle.
- Consult with a veterinarian on whether to use antibiotics.
Source: Alberta Agriculture