Control of Parasite Transmission
CONTROL OF PARASITE TRANSMISSION
KEY POINTS
- Regular Treatment
- Environmental control
- Prevention of zoonotic transmission
ENVIRONMENT
For parasites whose eggs or larvae are passed in the faeces, the control of parasite stages in the environment is essential to minimise the infection risk to other animals or humans (zoonosis). Parasitic contamination of the environment can occur in a number of ways, including the excretion of parasitic eggs or larvae in the faeces and the release of cestode proglottids. Environmental infection pressure of dog-transmitted parasites can be maintained by wild foxes and stray dogs in both rural and urban areas. Similarly, feral and wild cats can form a reservoir of feline infection.
The infection of intermediate or paratenic hosts (i.e. birds, rodents, slugs and snails) can contribute to a longer survival time of parasitic stages in the environment.
Most environmental parasite stages are highly resistant to environmental degradation (from months to years). Freshly excreted stages of many parasites can be directly infective (e.g. Taenia spp. and Echinococcus spp. eggs). Other parasites, such as nematode eggs, require anything from a few days to a few weeks at appropriate temperatures, usually above 16°C, to reach the infective stage. It is therefore important to prevent initial parasite environmental contamination by implementing comprehensive parasite control programmes based on local epidemiological knowledge.
The safe disposal of animal faeces is essential. This should be on a daily basis and faeces should not be flushed down the toilet or disposed of in compost intended for edible crops. In countries or regions where legislation permits, faeces can be disposed of in household waste collections or dedicated “poo bins”.
Measures to facilitate faecal removal, such as the provision of disposal bins and bags should be encouraged. As it is difficult to control where outdoor cats defecate, particular attention should be given to worm control in cats.
Measures to facilitate faecal removal, such as the provision of disposal bins and bags should be encouraged. As it is difficult to control where outdoor cats defecate, particular attention should be given to worm control in cats.
Leash-control and faecal clean-up laws should be enforced by the local authorities, especially in urban areas.
Legislation to control stray dogs and feral cat populations should also be enforced by the appropriate authorities.
Parasitised animals should be treated to minimise environmental contamination. In justified cases, animals should be monitored by faecal examination (e.g. animals with persistent clinical signs or suspected resistance).
Because eggs may persist in the soil for months or years for very contaminated areas, such as highly populated kennels, extreme measures are needed for decontamination, including the removal of sand/soil or covering the soil with concrete or asphalt.
In kennels or multi-animal households, the strict treatment and quarantine of new entrants is essential to avoid the introduction of infected animals.
Children’s playgrounds should be well fenced to prevent entry of animals, especially cats. Sandboxes should be covered when not in use. Sand, particularly if it is uncovered and is likely to have been contaminated with faeces, should be replaced regularly e.g. at least once or twice a year.
Desiccation and ultraviolet light are highly detrimental to worm eggs, so allowing exposure to sunlight and drying of contaminated areas can assist in reducing the level of contamination.
OWNERS
Since some dog and cat parasites can also potentially cause infection in humans, veterinarians have an additional responsibility for human health. A particular zoonotic risk comes from the widely present Toxocara spp. roundworms: after oral ingestion of infective eggs, the larvae can perform a somatic migration (larva migrans complex). If larvae become blocked in the human eye, nerve tract and/or brain during migration, serious health problems can occur.
After infection with E. multilocularis or E. granulosus, humans develop alveolar or cystic echinococcosis, respectively, with formation of cysts in the liver and/or other organs. Alveolar echinococcosis is a carcinoma like disease, which without treatment can have fatal consequences. Human infection occurs as a result of oral ingestion of worm eggs. The main source of contamination of the environment is the fox. Infection can also occur by the ingestion of eggs found on a dog’s fur or of eggs that have been excreted in dog faeces. Important preventive measures for pet owners include:
Practicing good personal hygiene, particularly washing hands after handling pets and before eating food.
Minimising the exposure of children in particular to potentially contaminated environments and teaching them good personal hygiene. Keeping nails short. Teaching children the importance of such practices.
Wearing gloves when gardening.
Washing raw fruit, vegetables and mushrooms before eating.
Controlling pet parasite infections through repeated treatments and/or regular diagnostic testing.
Preventing infection by reducing, where possible, the risk of the pet acquiring infection.
Cleaning up pet faeces regularly to reduce environmental contamination with infective parasite stages. Not disposing of faeces or cat litter in recyclable waste or compost.
Grooming dogs regularly to minimise the risk of coat contamination with worm eggs.
Changing shoes to prevent contamination of domestic areas.
People who are in regular contact with animals that may potentially transmit zoonotic parasites should be made aware of the risks and advised that these health risks are greater for pregnant women and those suffering from underlying illnesses or immunosuppression.
This information should be made available through physicians and veterinarians, without the need for a medical history of the client and his/her family. With this in mind, special care should be taken in the case of:
Immunocompromised individuals such as the elderly, diabetics, people with HIV-infection and those undergoing immunosuppressive chemotherapy, organ transplantation or treatment for autoimmune diseases.
Other susceptible groups such as pregnant women, babies, toddlers and those with learning disabilities.
People with occupational risks such as farmers, kennel workers and hunters.
STAFF
Protocols and recommendations for the control of parasitic infection should be communicated clearly to veterinary and para-veterinary staff and consistently applied. Cooperation between the medical and veterinary professions should be encouraged wherever possible and its benefits underlined in the case of zoonoses.
Pet owners should be made aware of the potential health risks of parasitic infection, not only to their pets but also to themselves and their family and friends. Professional brochures and posters placed in veterinary practices and pet shops are useful tools to facilitate this, as are websites.
The importance of regular anthelmintic treatment or joining a “pet health-check programme” should be made clear to the general public by veterinary surgeons, veterinary nurses and other animal health professionals and promoted consistently. Responsible dog and cat ownership can ease public health concerns and encourage the acceptance of dogs and cats as human companions.
Additional information and resource materials can be obtained from www.esccap.org
