Deworming Without Regular Testing: What's Missed
Routine deworming for intestinal worms in dogs without testing for faecal parasites is a popular choice among veterinary professionals across large parts of Europe. These treatments cover many parasites, including tapeworms, hookworms, whipworms, and roundworms. Sometimes, preventives are given based on a risk assessment and, sometimes, in a blanket fashion.
Given that modern flea preventives are highly efficacious, the question becomes, "If we're routinely treating for these parasites, why test at all?" The answer spans from non-compliant pet owners to preventive resistance—highlighting that, even if dewormers are being deployed, additional reasons for testing persist.
Not All Pet Owners Follow Treatment Suggestions
Many veterinarians assume that by recommending routine deworming, pet owners will be willing and able to carry out their instructions, and treatment will be effective. However, studies studies of pet owner behavior at specialists show compliance can be poor because owners may struggle to give medications, don't perceive the value in doing so, or simply forget the recommended schedule.
Faecal testing reveals whether worms are still present, and if so, a discussion can be facilitated with the owner to address whether a lack of compliance may be the cause. Issues preventing good compliance can then be addressed.
Regular negative tests in pets on routine preventive treatments are also hugely beneficial as they demonstrate value to the client, showing good treatment efficacy and pet owner compliance. This results in positive reinforcement, building owner confidence in both the current recommendations and how the owner is administrating the product.
Routine Treatments Aren't 100% Effective
Although current licensed preventive treatments are highly effective, they aren't 100% effective in all cases or with all parasites. Additionally, pet owners don't always consistently give the treatment—and if treatments are given at a frequency less than the pre-patent period of a parasite, ova shedding may still occur. Also, preventives do not prevent fleas from getting on the pet where flea tapeworm infections can still occur. In addition, the insecticidal compounds active against fleas have not been proven to kill the tapeworm D. caninum in any life stage. If ingested, an infected flea can transmit disease.
This is important as ova may build up over time leading to zoonotic exposure or parasite buildup in intermediate or paratenic hosts. If highly pathogenic worms, such as Ancylostoma caninum, are left in situ, dogs can potentially face serious health ramifications. Without testing, there's no way of knowing whether current treatment regimens are adequate.
Risk Assessments Aren't 100% Accurate
Some intestinal worms, such as tapeworms, are well suited to risk assessment using lifestyle and geographic data to decide whether dogs are likely to be exposed. However, these assessments are only as good as the data available, and sometimes, dogs will be exposed while not on treatment.
Faecal testing allows these infections to be detected and feeds data back into future risk assessments. This is particularly important for geographic assessment—without testing, we wouldn't have parasite distribution maps.
Detecting Preventive Resistance
Once preventives have been prescribed and we feel that pet owners are on board with our recommendations, there's often a temptation to assume products will be effective and parasites eliminated. However, the rapid spread of multiple drug-resistant hookworms in North America has demonstrated the importance of regular faecal testing to detect resistance early and take steps to prevent further spread.
Without faecal testing, we're blind as to whether preventive resistance is present and how quickly it is spreading.
Confirming Effective Treatment of Infections
It's important to know if infections have been eliminated after treating a dog for intestinal parasites. This is true for protozoa such as Cystoisospora and Giardia as well as other intestinal parasites.
The potential ramifications of undetected intestinal parasites depend on the worm involved:
- Toxocara roundworms: If infection is missed, ova will be passed in the faeces. If roundworms are allowed to build up and mature in the environment, they represent a significant zoonotic risk with infection leading to ocular and visceral problems as well as links to asthma, epilepsy, cognitive dysfunction, and other neurological syndromes.
- Hookworms: In countries where it is endemic, Ancylostoma caninum can cause life-threatening anaemia in dogs. Larvae hatching from ova in the environment mature and can then cause creeping eruptions known as cutaneous larva migrans if they come into contact with human skin. To eliminate hookworm infections from kennel runs and communal spaces, testing and treating infected dogs is essential to prevent numbers from building up to a point where clinical disease may be caused in dogs. This is also true for Uncinaria stenocephala, A. caninum's less pathogenic cousin.
- Whipworms: If not detected, whipworm eggs will build up as they live a long time in their environment, leading to clinical disease, particularly in dogs housed together or sharing kennel runs.
- Flea tapeworm: Flea tapeworm infections are well-tolerated by dogs, and human infection rarely occurs through flea exposure. Detecting the presence of flea tapeworm in faeces, however, is an excellent safeguard for loss of flea control where exposure to flea tapeworm and a range of other zoonotic pathogens could occur.
Without routine faecal testing, the efficacy of worm treatment and the distribution of parasites remain unknown. Regular testing is crucial to address issues in worm control before clinical disease in both pets and humans occurs.
Faecal tests used for screening should have a high sensitivity and specificity, and where worms such as Ancylostoma caninum can cause disease in the pre-patent period, detecting infection in the absence of ova shedding is also beneficial.
