12 November 2012

3 minute read

Farmers are most often concerned about Crypto because it causes diarrhoea and death in calves, the research team of Nick Jonsson, Lee Innes says.

Crypto is also important to public health because some species of the parasite, including the one that causes most disease in young calves, can cause disease in humans. Although Crypto are quite closely related to coccidia, they are much more resistant to treatment with most of the drugs that are effective against them. Crypto were only discovered to cause disease in cattle in 1971, and they have since been shown to be one of the three common non-bacterial causes of diarrhoea in calves between one and three weeks of age, the others being rotavirus and coronavirus. In recent years several vaccines have been introduced to the market to control E coli, rotavirus and coronavirus, but there is no equivalent vaccine for Crypto. The options for drug treatments against Crypto are also limited, with little agreement on the value of the products that farmers can use. Crypto are very resistant to environmental stress and to disinfection and not much is known about how the disease spreads in populations of cattle. As a consequence, it is probably no surprise that farmers and veterinarians have been increasingly indicating that the disease is a bigger problem than previously thought.

Why Work is Needed

The list of questions without answers is long and some of the recommendations made to farmers for the control of Crypto are based on theory rather than evidence. For example, it is not known why some farms have heavy mortalities as a result of infection with the organism while neighbouring properties using similar management strategies do not. Likewise, the effects of bedding management, hygiene and calving management on the disease are not well understood, although the fact that the parasite is transmitted from faeces to mouth of calves has led to suggestions that hygiene might be an important control strategy. It is thought that simultaneous infection with rotavirus increases the risk of disease, but not known whether vaccination with commonly used enteric vaccines has any impact on disease due to Crypto.

What has been Achieved so Far

With the participation of four veterinary practices in northeastern Scotland, 41 farmers have been questioned about their management relating to Crypto and its impact on their operation. Before starting, the vets identified farmers who thought that they had a problem with the disease and an equal number of farmers who did not think that they had a problem with the disease. The objective was to identify differences between the two groups to try to get some leads on where to go with future studies to find useful control methods. The same farmers have also been submitting faecal samples from calves and cows and it was found that most calves are infected at some time and that almost all of the farms are infected, whether there is a recognised problem or not. Those farmers who thought that they had a problem with Crypto had much higher number of scouring calves in the previous season (range 4 to 100%, with a median of 22%) than farmers who did not think there was a problem (range 0 to 32%, median 6%) and a higher number of calves dying with scour (2.7% compared with 1%). So far, all data are preliminary and should not be over-interpreted. Once the set of faecal samples is complete, careful examination of the proportions of animals in each herd and proportion of herds with animal testing positive for Crypto will be undertaken and all of the parasites from the faecal and post-mortem samples will be examined genetically. Further discussions will take place with all participating farmers in July to get a more accurate indication of losses for this season.

November 2012

Further Reading Find out more information on Cryptosporidium by clicking here.