History

The dog presented mid-November 2022 (day 1) with decreased appetite and weight loss of unknown duration, then developed bloody diarrhea (day 2). The dog was not up to date on endoparasite prevention (fecal test, deworming) and had unknown vaccination status. Clinical history indicated that the dog routinely shared an outdoor environment with rodents, coyotes, fox, and sheep and had been fed a raw meat–based diet within the past 2 months. On physical examination, the dog was thin, with a 2/9 body condition score, and had no other clinically significant findings. The dog lived in the Kelowna region of British Columbia (BC), western Canada. However, other dogs in the home had traveled off the property for working dog competitions (BC and Alberta).

The dog was part of a group of 8 animals that were working Border Collies on a sheep farm (acreage). Dogs from other locations would come for breeding and training purposes and mix with the resident group. All dogs were fed a predominantly dry dog food diet; however, in the recent past they had been fed a raw meat–based diet, which included raw sheep carcasses.

Diagnostic Findings and Interpretation

A fecal sample was submitted (day 2) as part of a GI infectious disease assessment and fecal parasite screening. The copro-PCR (KeyScreen GI Parasite PCR; Antech Diagnostics Inc)¹ detected DNA of Echinococcus multilocularis and Eimeria spp. The latter was considered to indicate coprophagia, as dogs are not definitive hosts for Eimeria spp. This result was confirmed by repeat DNA extraction and quantitative PCR of the same sample (Antech Diagnostics’ laboratory, Mississauga, ON, Canada) and by Antech Diagnostics’ research and development department (Fountain Valley, CA). Confirmation was performed by Sanger sequencing in duplicate; the sample was 100% identical (217 bp of the NAD2 mitochondrial 12S gene) to an E multilocularis isolate collected in a human from Austria in 2020 (GenBank accession No. MN444822, 2020).

The dog’s original fecal sample and extracted DNA were split and submitted for PCR sequencing to the Animal Health Laboratory, University of Guelph (Guelph), and to the University of Saskatchewan Zoonotic Parasite Research Unit for confirmation. The results from Guelph indicated a 100% sequence similarity (368/368 bp) to E multilocularis.² The results from the Zoonotic Parasite Research Unit determined over 846 bp of the NAD2 mitochondrial gene were consistent with the E3/E4 European haplotype of E multilocularis.³ This haplotype was originally reported in France and is increasingly detected in western Canada (wildlife, dogs, and people), including coyotes in BC.^3,4

Zinc sulfate centrifugal flotation of the original sample (Antech Diagnostics) did not detect taeniid eggs (Echinococcus or Taenia spp). Similarly, a canine diarrhea panel (FastPanel Canine Diarrhea Panel; Antech Diagnostics) of the original sample did not detect DNA of Campylobacter jejuni, Campylobacter coli, Cryptosporidium spp, Salmonella spp, Giardia spp, Clostridium difficile toxins A/B, Clostridium perfringens enterotoxin, canine parvovirus, or canine enteric coronavirus.

A CBC and serum biochemistry (Antech Diagnostics), thoracic radiographs, and abdominal ultrasound, performed shortly after treatment of the dog (day 10) by the primary veterinarian, were all unremarkable.

Treatment and Outcome

The dog was treated by the primary veterinarian (day 2) for nausea with maropitant (2 mg/kg body weight [BW] once daily) and for suspected infectious agents (bacterial and parasitic) with metronidazole (15 mg/kg BW every 12 hours) and with milbemycin oxime (0.5 mg/kg BW) and praziquantel (5 mg/kg BW). Clinical improvement was noted by the dog owner on day 4. Recheck fecal tests (KeyScreen GI Parasite PCR; Antech Diagnostics) at approximately 10 days and at 3 weeks after treatment did not detect E multilocularis. Routine monthly deworming (praziquantel) was advised for all dogs on the property at high risk of consuming rodents, along with avoidance of raw meat due to the risk of other parasites and bacteria.

Although E multilocularis is not reportable in BC, the Centre for Disease Control (BC-CDC) and the Ministry of Agriculture were informed of the case due to the risk of human exposure. The dog’s owner was advised to contact their human health-care provider if they (and in-contact people) had health concerns.

Comments

Echinococcus multilocularis is a tapeworm of evolving concern in North America (NA).^2–5 Wild canids (fox, coyote) and domestic dogs are suitable definitive hosts. Adult tapeworms live in the small intestine and produce eggs that are immediately infective and environmentally resistant in the feces (Figure 1). Dogs can serve as definitive hosts and harbor adult cestodes in their intestine after they ingest the larval parasite (metacestode) in the liver of a rodent (intermediate host). Dogs may not demonstrate clinical signs when enteric infection occurs (ie, intestinal E multilocularis). However, diarrhea was reported in this dog and has been reported in other cases of intestinal E multilocularis.³

Adult Echinococcus multilocularis superimposed on a Canadian dime.

Citation: Journal of the American Veterinary Medical Association 261, 9; 10.2460/javma.23.03.0179

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Adult Echinococcus multilocularis superimposed on a Canadian dime.

Citation: Journal of the American Veterinary Medical Association 261, 9; 10.2460/javma.23.03.0179

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• Download figure as PowerPoint slide

Adult Echinococcus multilocularis superimposed on a Canadian dime.

Citation: Journal of the American Veterinary Medical Association 261, 9; 10.2460/javma.23.03.0179

• Download Figure
• Download figure as PowerPoint slide

Increasingly, dogs in NA are serving as dead-end, or aberrant, intermediate hosts. In these instances, dogs are infected through ingestion of eggs in the environment, food, or water or possibly via autoinfection.^3–5 Thereafter, dogs can develop alveolar echinococcosis (AE), cysts, or tumor-like lesions, most commonly in the liver.^3–5 As AE in dogs (and humans) can be severe and fatal, particularly with delayed diagnosis, prompt recognition is essential.^3–5

Dogs with intestinal E multilocularis infection can be a source of zoonotic risk for humans. This can occur through human consumption of eggs that are in dog feces, are adherent to fur, or are in contaminated produce and water.⁵ Since the eggs of Echinococcus spp and Taenia spp are not reliably detected on fecal flotation (as in this case) and, when observed, cannot be differentiated on microscopic examination (eg, centrifugal flotation), fecal PCR to detect (or whenever taeniid eggs are found in dog feces) and provide differentiation is advised. Accurate detection and identification are particularly critical in endemic regions to alert to E multilocularis human risk.³ The KeyScreen GI Parasite PCR panel tests for numerous common GI parasites and differentiates Taenia spp from E multilocularis and Echinococcus granulosus sensu lato. Endoparasite preventive care (fecal screening) of dogs in NA is advised by the Companion Animal Parasite Council (CAPC) and the Canadian Parasitology Expert Panel (CPEP). Utilization of sensitive copro-PCR for this screening may assist with identification of infected dogs, provides surveillance information for emerging parasites, and allows dogs to serve as sentinels for human risk (eg, alveolar echinococcosis, other zoonoses).

The dog in this case had no travel history off the property, and the most likely source of infection was an infected rodent, with subsequent development of enteric E multilocularis. The detection of Eimeria spp, an herbivore coccidian and marker for coprophagic behavior, indicates that this dog was also at risk of being a dead-end host (ie, potential ingestion of eggs from the feces of other dogs or coyotes) and thus possibly developing AE. Additional testing (CBC, serum biochemistry, thoracic radiographs, and abdominal ultrasound) due to the dog’s prior risk of exposure from ingestion of eggs in the feces of other dogs and coyotes was pursued, along with fecal PCR screening of other household dogs. Fortunately, these tests were negative, although AE can take years to develop in dogs and humans, and ongoing monitoring is (and was) advised.^3–5

Further evidence for local infection was provided through identification of European haplotype (E3/E4) E multilocularis. This result was consistent with other studies and has been increasingly detected in wild canids (coyotes), domestic dogs, and humans in western Canada, including coyotes and dogs in BC.^3,4 It is unclear whether this strain was truly imported to Canada/NA (ie, may have been present but not identified until after European strain identification). Unfortunately, the European strains are speculated to have higher pathogenicity and zoonotic potential in humans and dogs.³

Fortunately, as with this dog, enteric E multilocularis can be treated successfully with praziquantel (5 mg/kg BW). As such, and due to ongoing risk of reinfection from local wildlife, treatments, and ongoing monthly treatments with praziquantel, were recommended as per CAPC and CPEP guidelines. For CPEP this includes dogs assessed as high risk for developing GI cestode and nematode infections (eg, hunting dogs, access to carcasses, raw food diets), all of which were concerns for these dogs. There was also concern of egg ingestion from the feces of dogs or coyotes (environmental source) or autoinfection in this dog, and others on the property, and their becoming dead-end hosts, with subsequent development of AE and zoonotic risk. In contrast to enteric E multilocularis infections that are readily treated with praziquantel, therapy of AE in dogs is costly, is invasive, requires long-term (usually lifelong) therapy, and carries a guarded prognosis.^3,5

Raising awareness to inform veterinarians of E multilocularis, particularly for dogs who are at higher risk, is critically important in endemic regions and for dogs that travel to these areas. This evolving risk area now includes most of southern Canada and the north-central US. To address this need, recommendations for fecal testing, differentiation of Taenia spp from Echinococcus spp, proactive deworming with praziquantel in high-risk dogs, and education to ensure that dog owners are made aware of the parasite as well as potential animal and human health concerns are indicated. In this case, despite the lack of reportable status of E multilocularis in BC, public health was notified (BC-CDC, Ministry of Agriculture). The dog’s primary veterinarian advised the dog owner to contact their human health-care provider due to concern of past exposure, infection, and potential need for monitoring due to concern of disease (AE) development.

This case represents a report of a European strain of intestinal E multilocularis diagnosed in a dog with a novel, affordable, rapid (and commercially available) fecal PCR methodology (KeyScreen). It further represents the utility of fecal screening and management in line with existing guidelines (CAPC and CPEP). Fecal surveillance with quantitative PCR may serve to identify the true intestinal E multilocularis prevalence (regional, urban, rural) and, given associations between dog ownership and human AE, should be considered.³