Cryptosporidium and giardia are two protozoal parasites found in the intestinal tract of domestic and wild animals and humans. These protozoa are of concern to cattle producers because they can cause disease and lower production in cattle. Recently, these two parasites have also received a lot of media attention because they can cause gastrointestinal disease in humans who consume contaminated water supplies.
Cattle are often implicated as the source of the parasites in waterborne outbreaks of disease in humans, even though this is not always the case. In Western Canada, a lot of water quality monitoring surveys and research studies are on the go to get a better handle on the sources of these parasites to humans. Cattle and pigs are the focus of some of these studies.
Cryptosporidia are most commonly found in young calves a few weeks of age. This parasite can cause diarrhea in calves between one and three weeks of age, and it is often associated with rotavirus and coronavirus in mixed infections. Clinically normal calves can also shed cryptosporida in their feces and serve as a source of infection for other calves and the environment.
The only treatment for cryptosporidia is fluids. There is no vaccine currently available for cattle, but there is an experimental vaccine in the U.S. that shows some promise in reducing fecal shedding. This vaccine could potentially be useful in reducing spread and transmission of the parasite amongst calves and to humans via contaminated water or food supplies.
Giardia is found normal in cattle of all ages. It is rarely diagnosed as a cause of clinical diarrhea in calves. A few studies suggest that infection may be associated with reduced performance. Benzimidazoles (such as fenbendazole) can be used to treat giardia in cattle. There is no vaccine currently available in cattle to prevent infection or reduce fecal shedding.
Control of cryptosporidia and giardia in cattle has become important, not only to reduce the risk of disease in cattle, but also to reduce the risk of infection in humans. If the manure from cattle contaminates water supplies and the water is not properly cleaned or if fresh manure is used on produce, humans may become infected and develop diarrhea. This disease is usually self-limiting in most people, except those whose immune system is compromised. Then infection can become life-threatening.
To reduce the risk of human infection, management practices on farm must reduce fecal contamination of water bodies. The largest contamination of lakes and rivers occurs during spring thaw. This is the time when water treatment plants have a hard time filtering and chlorinating the water to reduce the parasite loads to acceptable levels for human water consumption. Sometimes there are orders to boil water prior to drinking when the parasite levels after water treatment are too high for safe human consumption.
So, what can producers do to reduce the risk of outbreaks of disease in their cattle and to reduce the risk of human infection from cattle? Prevent manure runoff from entering water bodies. To do so:
- Move wintering sites away from lakes and rivers
- Avoid frozen lakes and rivers for wintering sites
- Use berms or dikes to divert runoff away from water bodies
- Use wetlands or catch basins to collect runoff
- Use vegetative filter strips along water ways to filter runoff
- Move wintering sites frequently to reduce manure build-up by rotating feeding, bedding, and watering areas
- Clean up areas where manure has accumulated
- Select wintering, calving, and nursing areas that are not on heavily sloped land that drains directly into a water body
- Reduce stocking density (spread animals out)
- Have separate wintering, calving and nursing grounds
- Bed calving and nursing areas well and move shelters frequently to prevent manure build-up
- Restrict calf shelters to calf access only (for example, fence low so only calves can enter)
- Control cattle access to water bodies with off-site waterers (such as nose pumps, solar pumps, electric pumps), rotational/restricted grazing in riparian areas, access ramps and fencing
- Use properly composted manure on gardens and vegetable crops
- Utilize new technologies as they become available such as vaccines, beneficial manure and riperian management practices, and
- Drink filtered and chlorinated water.