We have had a number of calls and farm visits recently related to scours, particularly in older, weaned or soon to be weaned calves. While older calves can still be affected by all the causative agents that affect newborn and younger calves, such as E coli, Rota and Corona virus, Clostridium, and even Cryptosporidium, calves that are older are typically less susceptible to clinical disease from these pathogens. Coccidiosis, however, tends to be a more common diagnosis in older scouring calves, typically starting at 1-2 months of age, and up to a year of age. The reverse is also true, in that newborn or really young calves are typically not clinically affected by coccidiosis as the incubation period (time from exposure or infection to symptoms) is 17-21 days, vs E coli and rota, corona viruses that have a much shorter incubation period and tend to be a much more common cause of scours in younger, pre-weaned calves. There have been a number of newsletters over the years specific to cause and treatment, and prevention of scours in young calves, this newsletter will focus on clinical signs, diagnosis, treatment and prevention of coccidiosis.
Coccidiosis is usually an acute invasion and destruction of intestinal mucosa by protozoa microorganisms (Eimeria and Isospora) and can be a serious disease of cattle, sheep, goats, pigs, poultry and rabbits. Dogs, cats, and horses can also be affected and result in clinical disease, but is typically less common. Infection and clinical disease is characterized by diarrhea, fever, inappetence, weight loss and emaciation, and sometimes death. The clinical signs are due to the destruction of intestinal mucosa after infective parasite eggs are ingested from the environment in the feces from other infected animals. This damage to the intestinal lining results in the clinical signs of diarrhea, which can sometimes include blood or destroyed intestinal tissue, straining and eventually dehydration. The most typical syndrome is more of a chronic or subclinical disease in groups of growing calves. The calves may appear unthrifty and have soiled rear quarters, and feed efficiency may be reduced. Watery feces is a common finding, with little or no blood, and mild discomfort for a few days. More severely calves develop bloody diarrhea which may continue for a week or more. They may develop fever, be off-feed, and show signs of depression and dehydration. If severe enough calves may die in the acute period, or from secondary complications such as pneumonia.
Coccidia tend to be thought of as opportunistic pathogens. The severity of infection may be influenced by various stressors. Therefore clinical coccidiosis is most common under situations of poor nutrition, poor sanitation, overcrowding, or after stressors of recent weaning, shipping, feed or weather changes.
Coccidia are easily identified in feces by sugar float methods under a microscope and this is something Milverton-Wellesley Veterinary Services can perform in clinic without having to send out to an external lab. It is important to note that microscopic findings should always be interpreted in conjunction with clinical signs, as coccidial oocysts can be found in normal healthy or unaffected cattle.
The life cycles of coccidia are considered to be self-limiting, meaning once ingested and gone through its reproductive stages, infection will resolve spontaneously within a few weeks. However, reinfection may occur. Therefore, prompt treatment is recommended to slow or inhibit development of stages resulting in re-infection, thereby shortening the length of illness, reducing the discharge of infectious eggs into the environment from infected animals, alleviating hemorrhage and diarrhea and reducing the likelihood of secondary infections and death. Sick animals should be isolated so they can be treated individually and help prevent exposure of other animals. Antibiotics containing sulfonamides (Trimidox injectable or oral scour boluses) are usually very effective at treating. Amprolium given orally can also be very effective at either individual (drenching) or mass treatment in medicated water if a larger group is affected where isolation or treatment of individuals is impractical or not possible.
Prevention is targeted at limiting the intake of oocysts by younger animals so that infection may be established to induce immunity but not clinical signs. Good feeding practices, good management and sanitation are all important. Young animals should be housed in a clean, dry environment, with regular cleaning of feeding and watering equipment to prevent fecal contamination. Stressors such as weaning, sudden feed changes, and shipping should be minimized wherever possible. Administration of anticoccidials is also recommended when various management protocols can predictably result in stressors. Deccox and Rumensin, the most commonly known coccidiostats, are typically fed at low levels in starters or other prepared feeds during times of known stress. It is important to be aware that these products are labelled as aids in the prevention of coccidiosis. They are not to be used and are not successful in the treatment of an outbreak or clinical coccidiosis. Recent experience has shown that even cattle on a label rate of deccox can still get clinical coccidiosis under the right conditions.