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CRYPTOSPORIDIOSIS IN YOUNG CALVES
Cryptosporidium parvum is a small single-celled intestinal parasite capable of infecting all
mammals, and is closely related to coccida, writes Mícheál Casey, head of regional
veterinary laboratories, Backweston Laboratory Campus, Department of Agriculture, Food
and the Marine.
Cryptosporidium parvum multiples in the gut of infected animals, and damages the lining of
the lower end of the small intestine, resulting in mild to serve diarrhoea (‘scour’). It can
cause death, especially in younger calves. It is highly infectious and is very difficult to
eradicate once established in calf housing. While the focus here is on bovine
cryptosporidiosis, the disease it causes in calves, it is also a noteworthy human parasite and
can produce life-threatening illness, especially in the young, the old, or people whose
immune system is compromised in any way. It affects calves in their first month of life, with
peak incidence in the second week. It is capable of causing severe, occasionally fatal, disease
on its own. More severe cases are typically mixed infections, most frequently from a
combination of cryptosporidium and rotavirus. Infection is by the faecal-oral route, through
the ingestion of the infectious stage of the parasite (oocysts) passed in the faeces of
infected animals oocysts may be present in faecal matter in the calf’s environment and may
be transmitted by utensils or dirty protective clothing. Older calves that have recovered can
be a significant source of oocysts.
Diagnosis
In any calf scour outbreak, it is really important to confirm whether or not you are dealing
with cryptosporidiosis at an early stage. In young live calves, it is not possible to distinguish
cryptosporidiosis from the other causes of scour like rotavirus, coronavirus, Escherichia coli
and Salmonella on clinical signs alone as these are non-specific tests to be carried out either
by a veterinary laboratory or your veterinary practitioner. Faecal samples (collected in
sterile plastic containers) from untreated, scouring calves should be submitted to the
nearest suitable laboratory during the early stages of an episode of diarrhoea in a group of
calves. Where death occurs before a diagnosis is made, freshly dead calves should be
referred to your nearest Regional Veterinary Laboratory for post mortem examination as
soon as possible after death.
Treatment of affected calves
No routine drug regimen has proven consistently successful, so treatment is primarily aimed
at supporting the calf and improving its own ability to fight the infection. Optimal animal
husbandry and good nursing skills are required. Affected calves should be isolated and
housed in a clean, warm and dry area. Continue to feed milk or milk replacer as usual
(isolate affected suckler calves with their dam), and give one or two extra feeds (2L each) of
a good quality oral rehydration solution (see the Animal Health Ireland [AHI] leaflet).
Affected suckler calves should be left with their dams but separate from other young calves.
Treat the calves with halofuginone lactate of C parvum infection. Although this drug has had
mixed results in treating sick calves, it may reduce the severity of disease if administered
early in the course of infection. Please note that as this product is a prescription-only
medicine (POM) a prescription from your veterinary practitioner is required to obtain it.
Where there are mixed infections (more than one pathogen or ‘bug’ identified) control
measures appropriate for each specific agent should be put in place, which would include
vaccination in the case of rotavirus.
Prevention
High standards of animal management are key. Providing calves with a good-quality, dry,
warm environment and optimising their care and nutrition (especially colostrum feeding)
will reduce the level of challenge from this parasite while also improving their ability to fight
it. It is also important to quarantine any affected calves and administer halofuginone lactate
to their unaffected contacts, which will help to prevent spread of infection. Calving pens and
calf-rearing pens/ houses should be thoroughly cleaned (which means power hosing or
steam cleaning back to bare and clean metal/ concreate surfaces). Wooden and other
absorbent surfaces are not easily disinfected and should be removed/ replaced. It should
then be disinfected and left free of animal for at least three or four months before the new
calving season. Effective disinfectants suggested by AHI include the amine-based Keno Cox
(CIDLines NV, Belgium), p-chloro-m-cresol (Neopredisan [Vertriab GMBH, Germany])
hydrogen peroxide with peracetic acid (Ox-Virin, [Ox-Oxcta, Spain]), and 3 per cent
hydrogen peroxide.