Summary

Many farms worldwide suffer from cryptosporidiosis in their neonatal calves. With some farms reporting up to 30% of calf losses attributed to the parasite. During my PhD, I have researched potential transmission routes of the parasite to calves along with determining the effect infection could have long-term on calf growth. In this article, the best control measures and best disinfectants to combat the parasite will be discussed.

Cryptosporidiosis

Cryptosporidiosis is a disease primarily affecting neonatal calves, although the disease is also found in many other mammalian, avian and reptile species. It is caused by the protozoan parasite Cryptosporidium, of which there are over 35 recognised species, although not all of them are capable of causing disease. The main species of concern in livestock in the UK is the species C. parvum, which is zoonotic and also causes disease in humans. The main symptoms of this disease are watery diarrhoea, lethargy, dehydration and loss of appetite. Normally, the diarrhoea is self-limiting and the animal will make a full recovery, however, if animals are left untreated, receive a high dose, or are immune compromised in any way (perhaps also infected with another pathogen for example), death can occur.

There are four species of Cryptosporidium which commonly infect cattle; C. parvum, C. bovis, C. ryanae and C. andersoni. Cryptosporidium parvum is the species most commonly found in neonatal calves and is most associated with clinical disease. Cryptosporidium bovis and Cryptosporidium ryanae are more commonly found in older calves from 1.5–11 months of age. Generally, these species are not associated with clinical disease and so do not pose a risk to young or older calves in the UK. However, in some other countries such as Sweden and China, these species do cause disease. Cryptosporidium andersoni is more commonly found in adult cattle and it has been suggested this could be associated with reduced weight gain and milk yield however further research is required to confirm this.

Infection routes

There are many potential sources of infection for young calves, as Cryptosporidium oocysts (eggs) are very hardy, with the ability to survive a range of different temperatures and conditions. Infected animals have the ability to shed billions of Cryptosporidium oocysts and so the potential for the parasite to spread rapidly through a group of calves is very high. Potential routes of transmission include the farm environment such as contaminated sheds and feeding bottles, from people via contaminated boots and overalls, from other animals such as other calves, older cattle and wildlife species. As few as ten oocysts are required to cause an initial infection. Some studies have demonstrated that C. parvum is also found in older calves and adult cattle; however, in these studies, the variety of the parasite differed between adult cattle and calves and therefore it was concluded that it is unlikely that the older cattle were a significant source of infection for the calves.

Costs

Research carried out at the Moredun Research Institute has shown that the effect of Cryptosporidiosis could affect calves in the long term. Damage to the gut lining during infection appears to result in the reduction in growth rates in beef calves. This parasite has the ability to damage the epithelial cells in the gut which in turn leads to the calf having an inability to absorb nutrients. A sick calf tends to suffer a reduction in appetite and so is likely to suckle less in the first instance. A study carried out on a beef suckler farm in Aberfeldy, Perthshire showed that a calf with severe clinical cryptosporidiosis weighed, on average, 38 kg less at 6 months of age than a calf with no clinical disease. This could result in a loss of around £100 when these animals are sold at market compared to an animal which didn’t suffer clinical cryptosporidiosis. That, unfortunately, is only the tip of the iceberg. When totalling treatment costs, vet call outs, farm labour etc.; the real cost per severely infected calf is likely to be more in the region of £200.

This research also showed that animals with a mild infection still suffered from a reduction in weight gain over a 6 month period. This demonstrates that treating only the severely affected animals is not sufficient to protect the long-term health and profitability of the herd.

Control measures and management strategies

Control measures for this parasite are mostly management based, due to the lack of available treatment and vaccine options. Only one treatment (Halocur ®) is licensed for use in calves. This drug can be used as a preventative if you already know that there is a Cryptosporidium problem on the farm. It must be given for 7 consecutive days from birth and cannot be given to animals which are already suffering from severe diarrhoea for more than 24 hours. It is toxic at only twice the recommended dose and so it is very important to ensure the correct dose for each calf is given. This treatment was reported as being very good at reducing clinical disease and oocyst excretion, however, it does not cure the disease. Unfortunately, there is currently no vaccine for this parasite.

Keeping calves away from faeces is one of the top management strategies. This can be achieved by steam cleaning of animal pens and calving areas. Temperatures over 60°C are required to inactivate the parasite and so steam cleaning is able to both inactivate and wash away oocysts. Cleaning calf pens between each calf; calving areas between each season and ensuring calves have deep straw bedding, all help in keeping calves away from oocysts. Ensuring calves are strong enough to cope with an infection is also vital and so it is essential calves receive the correct quantity and quality of colostrum. This will boost their immune system and give them the best chance at surviving this disease. It is recommended that calves receive three litres of high quality colostrum within the first two hours of life, followed by a similar feed within 12 hours of birth. Colostrum quality can be checked using a colostrometer or a Brix refractometer.

Ideally, any animals which are already sick should be quarantined for at least a week after they stop suffering from diarrhoea. Calves are still able to shed oocysts in the week after they have stopped showing clinical signs of the disease and so keeping these animals away from naïve calves is important. It would also be good practise to age group calves so that older calves which may still be shedding oocysts do not infect younger calves. Sick calves should be rehydrated with electrolytes to prevent dehydration and these animals should always be treated/fed after the healthy ones to prevent Cryptosporidium transfer to healthy animals on dirty overalls and boots. It is so important to replace the lost fluids and electrolytes lost by a scouring calf. AHDB recommend one or two extra feeds of 2 litres oral rehydration solution which is given independently of milk feeds.

Concurrent infections of Cryptosporidium can occur with other pathogens such as Rotavirus, Coronavirus, E. coli and Salmonella. This can result in more severe clinical disease and is more likely to result in the death of the animal. Ensuring dams are vaccinated prior to calving against Rotavirus, Coronavirus and E.coli can minimise the chance of a concurrent infection. It is very important to consult a veterinarian, in order to accurately diagnose the cause of diarrhoea, to ensure that the correct treatment can be given.

Slurry and manure should be well fermented, reaching temperatures of 60°C in order to inactivate the Cryptosporidium oocysts, before spreading on pasture. Frequent turning of manure should ensure that all the faecal material reaches the required temperature to avoid environmental contamination.

Disinfectants

The use of disinfectants can also assist in the removal of Cryptosporidium oocysts from the environment. This parasite is resistant to many of the commonly used disinfectants used on farms; however, research at The Moredun Research Institute has shown that 3% Hydrogen Peroxide is the best at reducing the viability of Cryptosporidium oocysts. The shelf life of Hydrogen Peroxide is only 1 month so alternatives such as 2% Keno™cox and 3% Neopredisan 135-1 are also good options. It has been shown that disinfectants do not work as well on oocysts which are in faeces, and so it is essential to clean out the pen thoroughly before disinfection for the best results.

Conclusion

In order to combat this parasite, it is essential to ensure calves are given adequate colostrum to help them deal with the disease, as severe disease can result in a long-term reduction in weight gain. To keep your calves safe it is essential to reduce environmental contamination of oocysts by steam cleaning pens and calving areas as well as using disinfectants such as 3% Hydrogen Peroxide, 3% Neopredisan 135-1or 2% Keno™cox. Using disinfectants on clean pens and making them up fresh on the day of use will help to maximise the efficacy of these products.

References

Cryptosporidiosis in cattle, The Moredun Foundation, News Sheet Vol. 6, No 1. February 2014.

The 3 Qs of feeding colostrum: Quantity, Quality and Quickly. AHDB Dairy and RVC 2015.