A study examined the impact of coastal pastures on the hygienic quality of surface waters – risk of infection in humans low
The risk of infection caused by coastal grazing is estimated to be low in recreational use of surface waters. This is revealed by a study on the occurrence of pathogens originating from cattle and sheep grazing in coastal areas in surface waters off the coast of North Ostrobothnia.
In the study, enteric microbes of ruminant origin were also observed on bathing sites. These microbes indicating faecal contamination do not automatically pose a risk of infection to humans. However, as no enteric pathogens from ruminants were found in the water samples, the risk of infection caused by coastal grazing remains low for the users of the water areas.
Microbes indicating faecal contamination generally end up in surface waters along with run-off waters from sources other than grazing livestock and are commonly found in surface waters. Enteric microbes of different animal species may originate from farmed animals, pets or wild animals.
Human norovirus is the most common cause of epidemics at bathing sites
Human enteric microbes usually originate from wastewater treatment plants, but they may also end up in surface waters from the private wastewater systems or may be brought to bathing sites by bathers themselves. The most common cause for epidemics at bathing sites is human norovirus and occasionally, Campylobacter, which occur both in humans and in different animal species.
Microbes causing gastrointestinal diseases were found in water samples taken from the bathing sites and ditches near pastures, but also in bathing waters far from any pastures. Most of these observations concerned a Campylobacter species that is most likely to have entered the water resource in the faeces of waterbirds.
“The health risk to recreational users remained low in the weather conditions where rainfall was low at the time of sampling, and no pathogens originating from ruminants were detected even in the samples from waters next to pastures," says Anna-Maria Hokajärvi, Senior Planning Officer at THL.
Although the study indicates that the risk of infection from coastal pastures is low, certain weather conditions, such as heavy rainfall, may increase runoff from pastures to water resources and increase the risk of infection.
“Hygiene hazards to water resources can be avoided, for example, by placing the drinking and mineral feeding sites of animals further away from the shore line ,” says Annastiina Rytkönen, a visiting researcher at THL, who is preparing her doctoral dissertation at the University of Helsinki on the hygiene quality of surface waters.
Coastal grazing can still be developed in a more sustainable direction
Coastal grazing is an effective way of maintaining endangered coastal meadows. However, livestock grazing on coastal areas has raised concerns about the impact of the manure on the hygiene of water resources. In Finland, enteric microbes of ruminant origin have previously been found in surface waters, and based on the findings, it is possible that animals also import microbes that cause infectious diseases into the water resources.
The RANTALAIDUN project coordinated by the Natural Resources Institute Finland and funded by the European Agricultural Fund for Rural Development studied the impacts of coastal pastures on the hygiene of local waters during the grazing seasons in 2021 and 2022.
The aim of the project was to increase knowledge of the impacts of grazing livestock on water resources and find solutions to practical problems related to the management of coastal grazing. The increasing information is aimed at promoting comprehensive planning and monitoring of the management of coastal areas and to develop coastal grazing in a more sustainable and effective direction.
The project also published a list of recommendations to minimise the potential health risks of coastal grazing:
- The locations of new pastures should be considered carefully, taking into account possible conflicts and disadvantages, for example, regarding recreational use of coastal areas.
- The grazing pressure should not be too high. Otherwise, the plant cover may erode excessively and there is a risk for sediment and nutrients to leach from the exposed soil.
- The division of pastures into smaller paddocks and grazing them rotationally should be increased. This helps to regulate the grazing pressure and prevents excessive erosion of the coastal pasture.
- Possible drinking and mineral feeding sites should be located further away from the shore line and in areas with less valuable habitat. This reduces the possibilities for leaching of nutrients and microbes, as well as prevents damage to valuable species and habitats.
- In coastal pastures, livestock should not be offered additional forage, and the pasture should be separated from fertilised pastures with a fence. Otherwise there is a risk of nutrients being transported to the coastal area.
Further information:
Recommendations for coastal grazing in the Rantalaidun project (Luke) (in Finnish): https://www.luke.fi/fi/rantalaiduntaminen-ja-vesistovaikutukset
Bathing water quality: Anna-Maria Hokajärvi
Finnish Institute for Health and Welfare
[email protected]
tel. +358 29 524 7715
Pathogens in ruminant manure: Annastiina Rytkönen
University of Helsinki
annastiina.rytkonen(at)helsinki.fi
Coastal grazing: Marika Laurila
Natural Resources Institute Finland
marika.laurila(at)luke.fi
