Deworming dogs...how often??
Deworming is a controversial subject. There are numerous opposing views, strong opinions and conflicts of interest that drive a lot of debate on the subject. There's no argument that parasites can be bad for the pet and some can pose a risk to people. There's no argument we want to reduce parasite burdens in pets to improve pet health and decrease human risks. It's the 'how' that causes all of the problems. Developing deworming strategies requires you to think of a few different things, such as:
- What parasites are in the area?
- Are the risks the same the year round or mainly seasonal?
- What parasites pose a risk to the individual pet or what are the pet's chances of exposure? (Does the pet go outside? Does it get exposed to many other animals? Are there multiple pets in the household?...)
- Are there any people in the household at particular risk for parasitic infections? (Young children, people with developmental disorders that might be more likely to get exposed to pet feces?...)
There are a few different approaches to managing this in adult animals (everyone agrees puppies and kittens need more aggressive deworming).
The Companion Animal Parasite Council advocates monthly deworming. There are a few reasons for this. One is the fact that the duration of activity of the drugs means that monthly treatment allows you to prevent establishment of significant parasite populations in the animal (and therefore also in the animal's environment). It also keeps the treatment user-friendly, in that it's easy for people to remember to treat their pet. Some concerns with this approach as the 'one plan fits all' mentality, despite the fact that there are great differences in the risks between different regions and between pets in the same area. There are also concerns about drug resistance (which is a problem in some other species like horses and sheep), although that doesn't seem to be a major concern...at least yet.
Recent European guidelines take a somewhat different approach and use a philosophy more geared towards individual risks for each animal. These guidelines recommend that if regular deworming is used, animals should be treated at least 4 times a year, with no more than 3 months between each treatment. This is based on some research indicating that dropping treatment to 3-4 times per year had no effect on parasite levels. This approach is therefore more conservative (in terms of the number of treatments) and probably has less of an impact on the development of resistance, but it requires more organization and thought. If used properly, it's probably a good approach.
Yet another approach was recommended by a Canadian Parasite Expert Panel. With that approach, in low-risk households (both pets at low risk for parasite exposure and people at low risk of infection), treatment is based on fecal examination results or, if fecal testing is not performed, once or twice yearly treatment is recommended. In high risk households, fecal testing is recommended 3-4 times per year, with treatment based on results, or administration of routine preventive treatment at least 2, and preferably 3-4 times per year. The main criticism of this approach is that it's more complicated and perhaps prone to errors or missed treatments.
There's no clear answer, nor should there be. There really can't be a 'one program fits all' approach that properly addresses the risks for all pets in all regions. Tailoring the deworming strategy to your pet, based on your pet's and your family's risk, is a logical approach. Regardless of the chosen approach, regular fecal testing is a good (and underused) way to assess what's going on with parasites in your pet and to identify treatment failure or the emergence of drug resistance.
Monthly heartworm prevention has an impact on what you do as well, since typical heartworm preventives are also effective against roundworms and hookworms, the main parasites that routine deworming is aimed against. If you are in a region where heartworm is present, monthly treatment during the heartworm season is indicated, and the main decision that needs to be made is what to do the rest of the year (when heartworm isn't a risk year-round).
Some Beach, Somewhere
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"Some Beach, Somewhere" is not only a popular country music song AND the name of one of the best Standardbred racehorses in the world (originally Canadian, no less!), it's also the prime source of infection for a disease called cutaneous larval migrans.
Cutaneous larval migrans is a skin disease caused by migration of hookworm larvae. The most common hookworm species involved is Ancylostoma braziliense, which can be shed in the stool and dogs and cats. Ancylostoma caninum and A. tubaeforme are other species of hookworms that parasitize dogs and cats, respectively, and can also cause the disease, but much more rarely.
Animals infected by the hookworms shed hookworm eggs in their stool. These eggs then develop into larvae, and people become infected through skin contact with hookworm larvae in the environment, particularly in sandy areas like beaches where infected animals may have defecated.
Cutaneous larval migrans is characterized by a "serpiginous (snake-like) rash" that is intensely itchy (see picture left). This is caused by the parasite larva burrowing through the skin. In North America, the disease is most common in the southeastern US and the Caribbean. Most , if not all, cases in people in Canada are associated with travel, especially to Caribbean countries; they presumably caused by exposure to hookworm larvae on the beach. Ancylostoma braziliense is not found in Canada.
The best means of controlling cutaneous larval migrans are to promptly remove dog and cat stool from the environment and dispose of it in the garbage, and to regularly deworm dogs and cats. This is important in areas where A. braziliense is endemic, but is easier said that done in areas where feral (wild) dogs are common.
Photo source: http://www.leeds.ac.uk
