Food-Producing Animals
Success stories
The animal health industry plays a key role in livestock protection as a provider of tools to help prevent, control and manage animal diseases affecting Europe’s farming community. Thanks to these tools (vaccines and medicines) Europe has been successful in managing animal diseases such as salmonella, bluetongue or foot and mouth disease which just years ago posed serious threats to animal health, food safety and public health.
The industry remains acutely aware of future critical challenges however and strives to continue developing advanced solutions that protect both animal and human health. Below you will find links to a number of fact sheets outlining some of the successes experienced thanks to animal health products.
Worm infections
Several species of parasitic worms have livestock, poultry or fish as a host. They represent a burden for the animal as they compromise its health and welfare, which in turn hinders its performance. In addition, some specific worm species can also use humans as hosts; in such cases they represent a zoonotic risk.
Characteristics
Parasitic worms, often referred to as helminthes, are parasites, living in and feeding on living hosts, receiving nourishment and protection while disrupting their hosts' nutrient absorption, causing weakness and disease. Depending on the species, they live in all kinds of organs, like intestines, lungs, kidneys, etc. Their host-range covers range of species, including livestock, poultry and fish, and even humans.
Societal impact
Animal health and welfare
The symptoms of infection are not always evident. Clinical signs are often easy to see, however the impact of subclinical infections is much bigger as the infection may be unnoticed, which causes treatment to be delayed, with continuing negative consequences for the animal’s health and welfare.
Clinical symptoms vary and depend on the type of worm, e.g. lung worms affecting breathing capacity. The illness may show itself in reduced appetite. Additionally, intestinal worms can often cause diarrhoea and the reduced absorption of nutrients, resulting in deficiencies which often manifest themselves through a dull-looking coat or loss of body weight.
Economic impact
The negative impact of a subclinical infection is often worse than that of a clinical infection, as they may continue unnoticed, e.g. the reduced absorption of nutrients and loss of appetite will negatively impact the production of meat, milk, fibre and eggs.
In a recent paper total costs as a result of a lungworm outbreak on two dairy farms were estimated at £159 and £167 per cow. Milk production was reduced by 15-20% during these outbreaks. Reduced milk production accounted for 52-36% and mortality for 33-51%, respectively. The remaining 13-15% of the total costs were due to extra inseminations, laboratory diagnosis and treatments.
The costs of subclinical infections are more difficult to determine. A Belgian field study estimated the cost per year per cow for gastrointestinal nematode and liver fluke infection at €46 and €6 respectively. UK Food Standards Agency (FSA) data for 2011 show that 22% of cattle livers and 6% of sheep livers were rejected due to fluke infection, costing the UK beef and sheep industry £13-15 million.
Human health/zoonotic impact
Humans can also be a host for these worms. However, EFSA’s zoonoses reports confirm that in Europe human infections by these parasites are uncommon. Incidents are mainly caused by Trichinella. The positive findings reported by Member States in 2010 were from pigs from non-controlled or unspecified housing conditions, mainly originating from wildlife (wild boar hunting).
Prevention, control and treatment
Developing and maintaining effective prevention, control and/or treatment strategies is complicated by the life-cycle of these parasites.
- Their life-cycle can be separated into a parasitic phase on the one hand - living in the host - and a free-living phase on the other - in the environment. Some parasites have specific hosts, but others are capable of infecting and multiplying in a wider range of hosts, e.g. Trichinella spp.
- Part of their life-cycle is in a low-metabolic stage, like eggs. This protects them well against the mechanisms of actions of the anthelmintics that need their metabolism to kill them. These eggs can survive for a long time, either in the host or the environment.
Effective strategies need to address all phases as much as possible. Depending on the husbandry system, measures that interrupt the life cycle of the parasite and/or impact the environmental phase of the life-cycle, like rotation to other pastures for grazing or housing in confinement/stables, are required.
The animal health industry has developed vaccines and de-wormers (anthelminthics).
- Vaccines against parasites are available, but their range is limited as vaccines are pathogen and species-specific.
- Anthelmintics are a more broad-ranged tool for controlling parasites. Application of de-wormers should not only be aimed at treating infected animals showing clinical signs. Instead, the use of de-wormers in a timely manner to reduce infection before symptoms of the disease occur is to the advantage of the animal’s health and welfare and is also more cost-effective.
Anthelmintic resistance can occur over time, therefore regular monitoring is required to identify
- when a change of product is needed and
- which product is expected to be the most effective against the present worms.
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