Septicaemic colibacillosis is a major cause of early calf deaths. The condition is often fatal or leads to post-septicaemic infections that are often non-responsive to treatment. If an outbreak occurs, every effort should be made to isolate the affected calves immediately. If the cause of the condition is known, systemic antibiotic therapy can be helpful.
Various serotypes of enterotoxigenic Escherichia coli (ETEC) can cause either diarrhoea or septicaemia in very young calves (first 4 days of life). The main factor in these infections is inadequate passive immune transfer from the dam to calf or exposure to the pathogen before colostrum was ingested, immediately after birth. The main risk factors for ETEC infection in young calves are non-successful transfer of passive immunity in colostrum (inadequate ingestion or absorption or inadequate antibodies in colostrum), inclement weather, use of milk replacers as opposed to whole milk, and poor hygiene, especially in calving pens.
- Causes of Colibacillosis (E.coli)
- Effects of Colibacillosis (E.coli)
- Treatment & Control of Colibacillosis (E.coli)
Causes of Colibacillosis (E.coli)
Three groups of E. coli bacteria have been associated with diarrhoea in calves. The most common are enterotoxigenic E. coli (ETEC). Enteropathogenic and enterohaemorrhagic types are also common but non-pathogenic to cattle, including the verocytotoxic (VTEC) forms that cause severe illness in humans such as E. coli 0157. The VTEC have been isolated from calves with diarrhoea (10% of diarrhoeic calves less than 2 weeks old) but were also found in non-diseased calves (16% of animals tested), therefore although EHEC 0157 may be associated with neonatal diarrhoea, it is also carried asymptomatically by many animals.
Environmental challenges in the form of inclement weather and diet changes have also been associated with ETEC infections. Septicaemic colibacillosis, caused by another serotype of ETEC, is an acute disease with very few diagnostic signs and is the most common cause of acute, fatal illness in neo-natal calves. Depressed, weak animals initially have a fever but become hypothermic rapidly.
Mortality rates are high and survivors are often affected by post-septicaemic localisation of infection in the form of arthritis, meningitis or pneumonia. Inadequate transfer of passive immunity from the dam is considered the main risk factor for colibacillosis.
Effects of Colibacillosis (E.coli)
ETEC cause diarrhoea in very young calves, less than 3-4 days of age (typically less than 48 hours of age). Calves are depressed, do not drink or suckle, become dehydrated, and die rapidly. Very profuse and watery diarrhoea is typical of ETEC scours.
Diarrhoea caused by enterotoxigenic E. coli (ETEC) occurs in outbreaks in herds where the pathogen has been introduced and susceptible calves are present.
Inadequate intake of colostrum and absorption of immunoglobulins is the main reason for susceptibility. ETEC diarrhoea in calves has also been associated with the presence of viral scour pathogens, rotavirus and coronavirus.
Treatment & Control of Colibacillosis (E.coli)
The passive immunity acquired from the colostrum and absorbed into the circulation from the gut is the calf’s main defence mechanism against E. coli diarrhoea. Inadequate amounts of immunoglobulins in the colostrum, inadequate intake of the colostrum and inadequate absorption of immunoglobulins from the gut render very young calves susceptible to infection.
Additionally, among calves aged 1-4 months old, carriage of VTEC E. coli O157 was reduced if the calf had suckled colostrums from the mother or if the calf had stayed more than 2 days with the mother after calving.
An improvement in colostrum feeding in the first 6-9 hours of life and dam immunisation against ETEC E. coli F5 (K99) adhesin (Rotavec Corona, Schering Plough Animal Health) are the main ways of controlling disease in herds that have been infected. The disease can be controlled and prevented by the use of dam vaccine 4-6 weeks before calving, improved hygiene around calving and improved colostrum administration.
Where the disease is absent from the herd, the prevention should concentrate on keeping it out by good herd security, as it has been suggested that routine vaccine use may select for more virulent strains of virus to become a problem in the herd.
Intestinal microflora balance has been reported to be improved in calves fed on green tea extracts in one experimental study. Although this are experimental results only and not available commercially.
The disease requires an immediate response, centred on isolation and rehydration therapy. Antibiotics can be useful if given early, but not without rehydration therapy. If given orally, amoxicillin is recommended, with amoxicillin, ampicillin, potentiated sulphnamides and ceftifur suggested as appropriate treatments for calves with diarrhoea which are also systemically ill.
In calves with diarrhoea and no systemic illness (normal appetite and no fever) antimicrobials are not recommended. Multiresistant (to antibiotics) strains of E. coli have been identified, and antibiotics should not be the main approach to treatment. One study has suggested that use of dried oregano leaves, which provides essential oils, may be effective as an oral treatment against colibacillosis. However, this is only experimental work and is, as yet not a commercial option.
There is evidence to suggest that the addition of antibiotics to the rehydration solution does not improve recovery. The use of oral antibiotics should be carefully considered in the case of undiagnosed outbreaks of calf scours to avoid further disruption of gut flora. If the calf is incapable of drinking the dehydration solution, parenteral rehydration has to be provided.
The isolation of affected calves, effective treatment with rehydration solutions and the provision of dry and warm conditions are vital in the treatment of calf scours, in order to avoid further suffering.