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- Newborn calves often present with diarrhoea, which leads to sizable losses for dairy farms. There may be several reasons for diarrhoea in calves, but rotavirus is responsible for as much as 28% of so-called ‘early’ diarrhoea in the first week or two post birth.
- It is possible to identify rotavirus without there being any clinical symptoms present. Researchers are also of the opinion that not all rotaviruses are pathogenic or disease-causing.
- Rotavirus infections occur most frequently between days three and 21 post birth.
- The pathogens responsible for diarrhoea in calves typically present as a mixed infection. Along with rota- and coronaviruses, a number of other bacteria may lead to diarrhoea in particularly young calves.
- As with most other diseases, the phrase ‘prevention is better than cure’ is equally apt in the case of rotavirus infections.
Newborn calves often present with diarrhoea, which leads to sizable losses for dairy farms. There may be several reasons for diarrhoea in calves, but rotavirus is responsible for as much as 28% of so-called ‘early’ diarrhoea in the first week or two post birth, and as much as 51% of ‘late’ diarrhoea four or more weeks post birth.
It is possible to identify rotavirus without there being any clinical symptoms present. Researchers are also of the opinion that not all rotaviruses are pathogenic or disease-causing. Rotavirus damages the intestinal tract, although this is usually not fatal. However, bacteria such as E. coli or protozoa such as Cryptosporidium may cause secondary infections, which drives up the mortality rate.
Livestock infected with only rotavirus usually recover without treatment. Young animals are more prone to infection and death than older animals.
Rotavirus infections occur most frequently between days three and 21 post birth. A newborn calf has no antibodies against rotavirus, nor any of the other diarrhoea-causing viruses and bacteria, and for this reason a strategic, effective immunisation programme for late-pregnant cows is essential. Immunised cows produce antibodies than can serve as protection from week one to six post calving (period of high susceptibility).
Diarrhoea in calves
Dr Chris van Dijk, specialist ruminant veterinarian, concurs that there are several bacteria, viruses and protozoa responsible for diarrhoea in young calves. These pathogens, he says, complement one other to some extent.
The pathogens responsible for diarrhoea in calves typically present as a mixed infection. Along with rota- and coronaviruses, a number of other bacteria may lead to diarrhoea in particularly young calves. Diarrhoea may be caused by Escherichia coli (E. coli), salmonella strains such as Salmonella dublin and Salmonella typhimurium, and organisms such as Cryptosporidium and various coccidia.
Read more on how to combat diarrhoea among your herd here.
Diarrhoea due to rotavirus
The rotavirus is one of the more common culprits responsible for viral enteritis and is clinically indistinguishable from most other causes of diarrhoea in newborn calves. Therefore, it is often found in combination with other viral, bacterial and parasitic diarrhoea causing pathogens. This double-stranded RNA virus belongs to the Reoviridae family and is responsible for gene rearrangement, and thus multiple strains such as the coronavirus.
The virus normally inhabits the intestinal tract of mature cattle, and when excreted in manure it proceeds to infect the environment, leading to calves becoming infected when they ingest the virus. Once ingested, the virus infects, damages and destroys the cells of the intestinal tract, which impairs nutrient and fluid exchange.
In newborn calves, clinical signs are observable from two to four days of age. A common characteristic of the disease is excessive watery, pale yellow diarrhoea that can lead to dehydration, an electrolyte imbalance, metabolic acidosis and death.
At a clinical level it is difficult to distinguish rotavirus infections from diseases caused by other viruses or bacteria. Dr Van Dijk says some tests can be performed on the farm, but the best course of action is to have an accredited laboratory confirm the presence of rotavirus. This is necessary if it turns out that the administered vaccine is not 100% effective. This is necessary if it turns out that the current vaccine is not 100% effective. In such a case, typing of the virus should be considered, which will allow for the production of an autogenous vaccine for the farm in question.
Act preventively
As with most other diseases, the phrase ‘prevention is better than cure’ is equally apt in the case of rotavirus infections. Dairy calves are usually penned before weaning, which creates an ideal environment for the virus load to slowly build up over time. Thorough disinfection of pens prior to the next group of calves arriving is non-negotiable.
The immunisation programme must assist in transferring enough immunoglobulins or antibodies to the calf via the mother’s colostrum in those crucial first six hours post birth. A combination vaccine containing rota- and coronavirus fractions, as well as E. coli and Clostridium perfringes type C, which are responsible for certain forms of redgut, are available. – Christal-Lize Muller, Stockfarm
For more information, send an email to Dr Chris van Dijk at dairyvetza@outlook.com.
