As technology improves, veterinarians can better treat their patients for parasites. Image courtesy Antech Diagnostics Seventy percent of American households have a pet, which studies show keep people happy, healthy, bring families closer together, and even lowers healthcare costs.1,2 Most pet owners consider them part of the family and strive to keep them healthy. Indeed, most dogs, and an increasing number of cats, receive wellness exams,3 and broad-spectrum parasite protection is widely available. However, despite these opportunities, parasites are on the rise, developing treatment resistance, and carrying zoonotic disease, all of which present a vexing challenge to both animal and human health. Some background Parasitic infections are common in cats and dogs. However, today’s parasites, characterized by rapid mutations and drug resistance, have successfully outpaced traditional screening and diagnostic capabilities, which are either not sensitive enough or they do not detect the number of parasites of significance to pet health. “Fecals” are the most frequently used screening technology: the ova and parasite (O&P) diagnostic protocol aims to identify parasitic eggs in fecal samples. It is an unpleasant, time-consuming process that is more than 100 years old. In addition, O&P misses important parasites, misidentifies others, and relies on an individual’s ability to detect eggs under a microscope, which is highly variable. O&P is unable to identify all parasites with zoonotic potential nor can it detect treatment resistance, making it difficult to always understand when and what treatment is required or if there is a human health risk. The next diagnostic advance, the enzyme-linked immunosorbent assay (ELISA), came 60 years later, offering detection of proteins shed by parasites. However, it, too, remains unable to reveal specific information about a parasite. The past few decades have seen little diagnostic progress, yet better diagnostic screening modalities are what is needed to detect a new generation of resistant parasites and ones that carry a human infectious risk. Zoonotic disease: Dangerous and on the rise COVID-19 sharpened awareness of the connections between humans, animals, and disease. Climate change, overtreatment in livestock populations, and loss of wild spaces contribute to the increase in zoonotic disease. According to the World Health Organization (WHO), 60 percent of emerging infectious diseases in humans are zoonotic, accounting for one billion cases of illness and millions of deaths each year. While the risk of contracting disease from pets remains low, there are critical advantages to knowing if a pet is infected with a zoonotic genotype or assemblage: Giardia offers an instructive example. A complex species, Giardia has seven assemblages, A to G. Some have a host preference: dogs are primarily infected with C and D; and cats tend to get the F assemblage. Other assemblages have a limited host range. For instance, E affects hoofed livestock, while assemblages A and B can infect a wide range of species, including humans. O and P and ELISA cannot differentiate between genotypes, making it nearly impossible to know if a Giardia-positive pet could be a threat to human health, particularly children and older or immunocompromised adults. Additionally, if a Giardia-positive dog infected with a non-zoonotic assemblage has no clinical signs, treatment may be unnecessary. Considering the limitations of current diagnostics however, well-intentioned treatment could follow, which runs counter to the veterinary profession’s commitment to pharmaceutical stewardship. The ability to understand which Giardia assemblage is present allows veterinarians to treat pets without clinical signs upon confirmation of a zoonotic strain. They can also educate pet owners about the increased risk of transmission to vulnerable human groups. If the zoonotic strain is not identified, veterinarians can reassure pet owners. Finally, if a dog in a non-risk environment is not showing clinical signs of disease, veterinarians can feel confident in the decision not to treat, preventing overtreatment and supporting pharmaceutical stewardship. Molecular testing affords this opportunity. It is uniquely able to address new parasitic threats, such as zoonotic Giardia because its diagnostic modality is fundamentally different than any other diagnostic modality. To detect parasites, molecular diagnostics reads their genetic material as it looks for the DNA of a parasite, not its eggs or a protein. Additionally, molecular technology can screen for a wide range of parasites—20 from a single sample. This vastly exceeds what is possible with conventional tests. While veterinary access to molecular testing is relatively new, its routine use will dramatically advance the ability to identify, treat, and protect pets and pet owners from disease with greater precision. The threat of treatment-resistant hookworms When parasites do not respond to treatment, the threat to human and animal health multiplies. Drug resistance is a growing threat to effective treatment of veterinary patients, and, in particular, the recognition of anthelmintic drug-resistant parasites that have evolved to become a more serious concern, a hallmark being multidrug resistance (MDR). The canine hookworm (Ancyclostoma caninum) is one of the most prevalent intestinal parasites affecting U.S. dogs. Prevalence is rising dramatically. A 2019 study of 39 million fecal samples showed a 47 percent increase between 2012-2018.4 While there are three main drug classes and many treatment options available, their intensive overuse has created high levels of anthelmintic resistance and MDR.5 MDR A. caninum is also zoonotic, which compounds the threat to human health. Once again, molecular testing affords this novel capability, presenting veterinary medicine with an opportunity to address treatment resistance before it becomes a runaway train. Molecular testing as a wellness imperative Veterinarians play a vital role in the One Health Initiative. With parasitic challenges increasing, migrating, and mutating, comprehensive, precision parasite testing is a wellness imperative. Molecular diagnostics plays a fundamental role. The ability to detect a broad range of parasites in one sample, identify zoonotic genotypes, and differentiate among assemblances of Giardia to inform effective treatment all extend the veterinary professions’ leadership in addressing emerging threats to both human and animal health. However, the best diagnostic modality is irrelevant if it is not a part of routine testing. As pet-owner compliance with wellness testing continues to improve, particularly among newer generations of pet owners, the opportunity to leverage the best testing modality is now practical and affordable for routine screening. Molecular testing ensures veterinarians continue to demonstrate their leadership, inspiring new levels of trust, confidence, and willingness among pet owners to follow recommended preventive care practices. As pet ownership continues to rise and pandemic challenges persist, to say that today’s veterinary practices are time- and resource-constrained is an understatement; those points are receiving focused attention, and appropriately so. Molecular testing contributes several benefits to the busy practice. First, it requires a very small sample that can be stored refrigerated for up to 10 days. Upon detection of Giardia or hookworm, it automatically tests for assemblages with zoonotic potential or resistance genes, eliminating the time and resource strain of repeat pet owner visits. Molecular testing can also preserve precious staff time by eliminating lost time for patient care to process and analyze in-clinic O&P. Integrating molecular testing into the wellness exam means veterinary teams can find more disease earlier, offering pet owners and practices the time and cost savings that naturally follow when veterinary medicine can focus resources on patient care and deliver precise treatment faster. As science and technology advances, we have been able to identify the increased prevalence of important parasitic threats, emerging threats, and parasites previously believed to be insignificant. There remains much to learn. Molecular testing is a sophisticated new tool with numerous advantages, including an exquisite ability to have a lens into the genetics of the parasite, use the results to be clinically meaningful for the pet, guide owners in safe, responsible practices, and uphold issues central to the profession such as pharmacological stewardship and the responsible use of anthelmintic drugs. These important One Health priorities support positive change in veterinary medicine while also safeguarding human health. Traditional diagnostic modalities do not offer the level of differentiation veterinarians require to diagnose clinical disease in sick patients or detect a chronic infection in a healthy animal during wellness testing. The level of specificity that molecular testing allows can facilitate informed decision making regarding treatment, affirming veterinarians’ role—once again—as One Health stewards amidst evolving challenges. FAST FACT Pet owner compliance with wellness exams is strong. In 2016, 90 percent of dogs and 65 percent of cats received exams, numbers that are expected to reach 96 percent and 80 percent respectively by 2030. Source: AVMA https://www.avma.org/blog/pet-populations-are-way Christian M. Leutenegger, Dr.Med.Vet., BSc, PhD, FVH is director of molecular diagnostics and research and development for Antech Diagnostics. References American Pet Products Association, National Pet Owners Survey, 2021-22. Michael J. Dotson, Eva M. Hyatt, Understanding dog–human companionship, Journal of Business Research, Volume 61, Issue 5, 2008, Pages 457-466. “Pet populations are on their way up,” AVMA.org. 12.10.20. Accessed 12.7.21 Drake J, Carey T. Seasonality and changing plrevalence of common canine gastrointestinal nematodes in the USA. Parasites Vectors. 2019;12:430. Kaplan RM. Drug resistance in nematodes of veterinary importance: a status report. Trends Parasitol. 2004;20:477–81
