Rotavirus and Coronavirus

Cattle Diseases

Rotavirus and Coronavirus in Cattle

Rotavirus and coronavirus are common viruses in cattle herds and are associated with almost 60% of diagnosed calf diarrhoea outbreaks (VLA, 2004). Rotavirus is the more common virus, responsible for 47% of diagnosed cases in the UK (VLA, 2004) and 24% of diagnosed cases in Sweden (Bjorkman et al, 2003). In comparison, corona virus was detected in 10% and 3% of diagnosed cases in the UK and Sweden respectively. They can both cause diarrhoea in calves on their own but are often detected in association with each other and other diarrhoea pathogens, like Cryptosporidium (Snodgrass et al., 1986; Reynolds et al., 1986).  The viruses have often been isolated from healthy as well as from diarrhoeic calves.

The severity of the disease depends on the age of the animal, the environmental conditions and the dam’s immune status. The ingestion of adequate amounts of colostrum is also an important risk factor.

Viral diarrhoea in calves occurs mostly between 5 and 10 days of age, and virtually always under 3 weeks of age. Rapid outbreaks with profuse watery diarrhoea and recovery in 2-3 days are characteristic of viral scours.

Winter Dysentery

Corona virus is also associated with a dysenteric syndrome seen in both older calves and adult cattle, most commonly in the UK in winter. The disease is characterised by sudden onset severe diarrhoea with high morbidity and is commonly known as Winter Dysentery. Older animals tend to be more severely affected and may pass blood in the faeces, have a severe milk yield drop and have a marked pyrexia (Cho et al., 2000). There is some suggestion that the same coronavirus strains cause calf scours and winter dysentery, and that in some cases disease spread is by respiratory secretion of virus from new cattle arrivals although the disease is not well understood (Cho et al., 2001; Traven et al., 2001; Hasoksuz et al., 2002). Adult cows will generally recover after 2-3 days of clinical signs although occasional deaths have been reported and there is substantial milk loss in dairy cows.

Control and Prevention of Rotavirus and Coronavirus

The control and prevention of viral diarrhoea in cattle is mainly based on the same principles as the control and prevention of calf scours in general (see: Calf Diarrhoea). Whilst the absorbed colostrum provides the necessary passive immunity against most infectious agents, the only protection the calf has in its early life against viral diarrhoea agents is the presence of immunoglobulins in the gut, obtained from the colostrum. The immunoglobulins obtained from the first colostrum feed during the first 24 hours of life are only protective for a few days, after which time the calf is very vulnerable to viral diarrhoea agents (hence the peak of viral diarrhoea occurrence at 5-10 days of age). The calves can, however, be further protected by continuing colostrum feeding up to 30 days of age as colostral antibody can have a local protective effect in the gut during this time (Andrews, 2004). Even small amounts of daily colostrum feeding are adequate to provide extra protection, compared with calves who do not get any colostrum after the first feeds.

In order to increase specific immunoglobulins in the colostrum, the dam can be vaccinated against rotavirus and coronavirus several weeks before calving (Castrucci et al., 1989; Rosic et al., 2000; Crouch et al., 2001). However, the long-term aim should be good calf rearing as disease prevention, rather than reliance on vaccination. There is also evidence to show that eradication of bovine viral diarrhoea virus from the herd and genuine closure of the herd reduce the incidence of rotavirus diarrhoea in calves (Klingenberg et al., 1999).

As the pathogens are ubiquitous, it is virtually impossible to prevent exposure to them. As the viruses are often isolated from both healthy and diseased calves, it is assumed that other risk factors play a more important role.

Treating Rotavirus and Coronavirus

Oral and/or parenteral rehydration therapy is the main treatment for viral diarrhoea in young animals (See Calf Diarrhoea). For sick and depresses calves a buffer containing solution should be used to balance the metabolic acidosis. Antibiotics are not indicated in viral infections, but are often used in severely affected animals that are suspected of having a secondary bacterial infection in addition to the viral disease. Non-steroidal anti-inflammatory drugs (NSAIDs) are also beneficial (Todd et al., 2010)

Withholding of milk for 24 hours is beneficial but not necessary. Suckled calves should be left with the dams. Non-suckled animals should be isolated immediately from other calves to avoid spread of infection.

There is no recommended specific treatment for Winter Dysentery as most animals recover without intervention, although fluid therapy may be considered in some cases.

Rotavirus, Coronavirus and Welfare

Calf diarrhoea is considered by the Farm Animal Welfare Council to be the main cause of early deaths in calves in the UK, and is a major animal welfare concern in dairy herds (FAWC, 1998). The fact that the majority of scouring problems can be avoided by good management adds to the need to tackle calf diarrhoea problems if they exist in pasture based cattle herds.  Isolation of affected calves, effective treatment with rehydration solutions and provision of dry and warm conditions is vital in the treatment of calf scours, in order to avoid further suffering.

Good Practice Based on Current Knowledge

The main areas of good practice for the prevention of viral calf scours can be divided into two categories: maintenance of immune status and reduction of stress.
Maintenance of immune status:

• Provide adequate bedding to allow calf to stand without difficulty
• Ensure early feeding of sufficient colostrum, assist if needed, monitor the intake as closely as possible and record it (“maximum supervision, minimum interference”)
• Keep a supply of frozen colostrum in case the dam leaks colostrum before calving
• Feed the calves colostrum as long as possible to provide passive, “in-gut” protection against viral diarrhoea; and
• Encourage outdoor calving
• Consider vaccination if a severe viral diarrhoea outbreak occurs
• If the farm has an undiagnosed continuous calf diarrhoea problem during the first three weeks of life, organise sampling during the next outbreak to identify the causative agent and factors and make a plan to improve control.
• Set up a recording system for individual calf scour cases and outbreaks of scours. Review the records at least twice and assess the situation, particularly after the first calf crop that has received whole milk
• Consider setting up a system where all calves are fed at least small amounts of colostrum during the first three weeks of life – This should come from Johne’s unsuspicious animals.

Reduction of stress:

• Avoid overcrowding in calf pens
• Avoid wet bedding
• Make sure that calves are well bedded during cold weather and do not suffer from draught
• Provide shelter during prolonged cold and wet conditions on pasture; and
• Do not transport very young calves.