Cryptosporidial Infections in Calves
Management decisions to reduce the suffering of sick calves demands serious consideration all aspects of nursing care of calves. They are after all 100% dependant on our care. This care must include the use of antibiotics to reduce suffering and minimise death rates.
The prevalence of cryptosporidiosis in calves is frequently reported to be second only to rotavirus in importance on a regional or national basis (throughout the world). And this figure represents approximately 30-40% of cases where infectious agents are found. Mixed infections are particularly common amongst calves where cryptosporidiosis is found. And the mortality rates for these mixed infections can be as high as 20 – 30% of affected calves.
Failure of Colostrum Transfer
In modelled infections in lambs, mixed infections of cryptosporidiosis and E coli show that mortality is highest in hypogammaglobulinaemic animals challenged sequentially with both infections rather than one alone. This is consistent with many reports that mixed infections have significantly more severe outcomes on mortality rates. – see Trial report on Mixed infections.
Weak calves not prepared to suckle or stand may also be at risk of secondary infections. These calves therefore will contribute to mortality statistics especially if calves also have low gamma-globulinaemia. Calves down or weak sucklers require causes for this condition to be identified. Acidosis, hypothermia, and septicaemia are important differential diagnosis for these calves.
Identifying the Septicaemic Calf
Differentiating severely acidotic calves from calves at risk of secondary infections can be based on the presence of sternal recumbency/weakness, and markedly reduced suckling reflexes.
The Effects of Age on illness associated with infectious scours
Septicaemia is more severe in calves less than 5 days of age.
The secondary bacterial infections which occur in young calves when the primary infection is cryptosporidiosis, arise early on in the crypto infection, when there is loss of intestinal wall function and invasion by bowel bacteria – especially E coli. Acidosis from fluid loss tends to be more severe in scouring calves over 8 days of age.
And while cryptosporidiosis is most common in the 8 to 12 day old calf, it does occur as early as 2 – 3 days of age.
Rectal Temperature of Calf
Rectal temperature is a useful guide to differentiate depressed acidotic calves from depressed septicaemic calves. A lower rectal temperature is more likely to be associated with depression and acidosis than associated with secondary infections. Depressed infected calves were more likely to be severely acidotic . And infected calves also grow at a slower rate than non-infected calves.
Energy supplementation alone will not reduce mortality of these weak moribund calves. Nor will more energy treat these clinical infections or lead to recovery of growth rate. That is, high tonicity (i.e. high energy) in an electrolyte as reported by Naylor 1997 may result in higher mortality if infections are not recognized as important. Identifying the sick calf requiring antibiotics remains a challenge.
Use a thermometer to identify calves with a raised body temperature.
Use a thermometer when calves do not thrive and recover as quickly as others in their group, particularly with Kryptade treatment.
What seems to be indicated:
- Fast rehydration with prompt treatment for acidosis i.e. bicarbonate isotonic electrolyte.
- Aggressive attention to volume restoration.
- Possible stomach tubing with small volumes of electrolytes (isotonic) – more frequently to avoid abomasal overload resulting in the rumen filling and secondary acidosis.
- Using pain relief to improve demeanor, and also suckling reflexes.
- Antibiotics will be required.
These will assist some of them.
Treatment of septicaemic calves (where this condition was primarily associated with diarrhoea) can still have high mortalities even when treated aggressively with both iv fluids, and also an antibiotic. Superior activity was reported with the use of cefquinome – once a day injection compared with gentamycin three times daily. Antibiotics which provide systemic treatment such as amoxicillin and oxytetracycline are favoured. Antibiotic resistance to these agents is possible, and surveillance of sensitivity of the farm’s E coli present may be advisable if products have been used for more than one or two seasons. Even within the same calf, coliforms change quickly and iv fluids as well as antibiotics are necessary to improve recovery rates. Even then % of calves succumbing can be quite high.
- In spite of the requirement to avoid antibiotics in tissue residues of calves going to slaughter, it is equally an animal welfare issue to avoid unnecessary suffering of young dependant calves.
- Antibiotics do have a place in treatment of scouring calves, particularly where there are deaths and a diagnosis has been based on an appropriate number of samples to provide a reliable diagnosis (albeit a diagnosis that applies to those calves from which samples were taken). Time may change infectious agents present in an environment where young calves are being reared.
- A number of actions including nursing as well as antibiotics may be required if such infected calves are to be aggressively targeted to have improved survival.
- Sacrificial post mortems of terminally ill calves are extremely valuable to identify the agents associated with scours. This includes having a veterinary consultation.
For further details on anti-bacterials in the calf see a report from Washington State university “Dairy calf treatment for diarrhea: Are the drugs we use effective?”