Cryptosporidium in cattle, are things getting better or worse?

Cryptosporidium is one of the major causes of scour in young calves. It accounts for approximately half of the neonatal diarrhoea cases investigated by SAC C VS. The peak of cases occurs in May, coinciding with susceptible spring-born calves. Cryptosporidium is a tiny, single celled parasite and ingestion of just a small number of oocysts can cause disease. The parasite multiplies rapidly within the gut and one infected animal can shed more than 1,000,000,000 oocysts in their faeces. This means that calves born later in the calving season could be exposed to a higher challenge than those born early in the season if managed in the same area. It should be remembered that some of the strains of Cryptosporidium that infect calves are zoonotic and can therefore also infect people.

A PhD project carried out at the Moredun Research Institute has looked at calf shedding patterns with the following findings to date:

• Cryptosporidium is prevalent in calves up to at least six weeks with the most predominant species being C. parvum.
• Older calves and adult cattle can shed C. parvum and act as reservoirs of infection even if they do not show clinical signs.
• The same species and genotypes of Cryptosporidium are generally present on farms year after year.

Further work is underway to identify the strains of Cryptosporidium present and this may help us understand why some farms have severe problems with calf diarrhoea due to Cryptosporidium yet others remain unaffected despite the parasite being present.

A review of cases of cryptosporidiosis diagnosed by SAC C VS each year indicates that there was a decrease in the number of diagnoses made in 2014 (figure 1). However, numbers of diagnoses of calf scour due to Salmonella, rotavirus, coronavirus, K99 strain of E. coli and coccidiosis had all also fallen in 2014. In autumn 2013, cattle were housed in better condition than the previous year. This together with better quality silage being fed over the housing period of 2013-2014 compared with 2012-2013 will have improved colostrum volume and quality and subsequent calf health.  The good summer and autumn of 2014 would therefore suggest that outbreaks of calf scour should stay low in spring 2015 – time will tell.

Number of cases of cryptosporidiosis diagnosed by SAC C VS

2010: 405 cases

2011: 311 cases

2012: 314 cases

2013: 329 cases

2014: 208 cases

Figure 1: Cryptosporidiosis diagnoses

In order to prevent calf scour (regardless of cause) we need to focus on two principles; maximising calf immunity and minimising the build up of the agents that cause diarrhoea.

• Ensure calves receive sufficient, good quality colostrum as soon as possible after birth. Calves should receive the equivalent of 10% of their body weight within the first six hours i.e. 4 litres for a 40kg calf.
• Consider vaccination of cows against three of the common causes of scour (rotavirus, coronavirus and the K99 strain of E. coli) to help boost colostrum quality.
• Regular mucking out of calving boxes, disinfection and provision of clean, dry bedding are essential. Buildings should have good drainage and ventilation to minimise build up of disease causing organisms.
• Cryptosporidial oocysts can survive for long periods in the environment and are resistant to commonly used disinfectants. Steam cleaning of buildings or use of specific disinfectants such as Keno Cox, Neopredisan, Ox-Virin or hydrogen peroxide is necessary. In addition slurry and manure should be composted before application to pasture.
• If calving outside, fields should be managed to minimise poaching and environmental contamination – moving feed areas may help with this.
• Manage calves in groups of similar ages; if young calves go into an environment heavily contaminated by older calves they will succumb to disease.
• Disinfect pens between batches of calves or use different fields for calf batches of different ages.

Helen Carty, Veterinary Investigation Officer, SAC Consulting