Parasite control in Canadian companion animal shelters and a cost-comparison of anthelmintics

Abstract

Animal shelters have limited resources and must accommodate large numbers of animals at unpredictable intake rates. These dogs and cats are often parasitized, which can adversely affect the health of animals and expose shelter workers and adoptive owners to zoonoses. We analyzed survey responses from rural (n = 32) and urban (n = 50) companion animal shelters across Canada, and compared the wholesale cost of commercially available anthelmintics to identify cost-effective methods of managing parasites within shelters. Almost all shelters employed nematocides (98% to 99%), but cestocides and ectoparasiticides were used less frequently. Shelters identified cost as an important consideration in choosing to perform fecal diagnostic testing and administer anthelmintics, and this motivated many shelters to selectively perform testing (66%) or never to test (32%), and to use drugs extralabel (80%).

Introduction

Companion animals surrendered to animal shelters may be at higher risk of parasitism than owned animals due to age (very young or very old), disruptions to or lack of regular anthelmintic administration, scavenging behavior, or poor health (1–3). In particular, dogs and cats of rural origin exhibit higher prevalence and intensity of endoparasitism than dogs and cats of urban origin (4–7). Animals often undergo vaccination, deworming, and reproductive sterilization at intake or prior to being adopted by a new owner. These measures minimize transmission of pathogens among shelter animals, from shelter animals to pre-existing pets of foster or adoptive owners, as well as zoonotic transmission from animals to shelter workers and adoptive owners. However, shelters vary greatly with respect to budget, size, number and species of animals processed, staff, and expertise. In the western United States, only 6% of shelters rely on veterinarians to manage infection control, and few shelter workers routinely receive training in infectious disease management (3).

A wide range of anthelmintic formulations are commercially available in Canada, each with different target parasites and host species. The Canadian Parasitology Expert Panel (CPEP) ranks Toxocara canis, Isospora, Giardia, and Cryptosporidium as the most common parasites in dogs in Canada, and T. cati, Isospora, Giardia, Cryptosporidium, and Taenia as the most common parasites in cats in Canada (8). The CPEP recommends that puppies be administered nematocides at 2, 4, 6, and 8 wk of age, and then monthly until 6 mo old (8). Kittens require a similar schedule starting at 3 wk of age. Dogs and cats older than 6 mo might require less frequent anthelmintic treatment or the addition of a cestocidal agent, depending on factors such as geographic region, outdoor access, immune status of owners, behavior (scavenging, coprophagia, hunting, etc.), and number of other household pets. Animals residing in regions endemic for heartworm (Dirofilaria immitis), ticks, or fleas should receive prophylactic treatment during high risk seasons. As well, CPEP recommends fecal flotations to identify parasite species twice per year for young dogs (< 1 y old), and 1 to 4 times per year for adult pets, depending on their risk factors (8). Fecal flotations (versus prophylactic anthelmintic administration) are useful for identifying protozoan parasites (e.g., Giardia, Isospora) that are not eliminated by most anthelmintic formulations. The United States based Companion Animal Parasite Council (CAPC) recommends treating cats and dogs for coccidiosis with a variety of drugs, including sulfadimethoxine, furazolidone, totrazuril, trimethoprim/sulfonamide, and ponazuril (9).

Previous research has demonstrated that deworming recommendations given to clients vary among veterinarians, and may even vary between practitioners working in the same clinic despite having established deworming protocols (10). As well, most veterinarians in western Canada do not educate clients on managing zoonotic risk within their homes (e.g., safe disposal of animal waste, hand washing, preventing access to wildlife and scavenging) (10). Surrendered cats and dogs spend variable amounts of time in animal shelters prior to being adopted and this is an ideal time to ensure that optimal pathogen management is practiced; however, cost is a deterrent. As well, adoption is an ideal time to discuss local deworming recommendations with future clients. Therefore, the objectives of this study were to i) determine differences in parasite control protocols in rural versus urban animal shelters in Canada; and ii) to compare the cost of commercially available anthelmintics.

Materials and methods

Shelter selection

From May to July of 2014, we contacted 125 Humane Society (HS) and Society for the Prevention of Cruelty to Animals (SPCA) shelters in every province and territory in Canada to survey veterinarians and shelter workers on companion animal parasite control protocols. We contacted each shelter a minimum of 2 times by telephone (7 to 10 days apart), and followed up by e-mail if we did not receive a response. “Urban” parasite control policies were examined by surveying every HS or SPCA in a population centre of more than 30 000 people, according to Statistics Canada 2013 Census data (11). “Rural” policies were examined by surveying shelters in the 5 most populous towns of less than 30 000 people in each province and territory (11).

Survey

Our survey asked respondents to provide information on surrender statistics (numbers of cats and dogs per year), parasiticides used, use of diagnostic parasitology tests, and extra-label drug use. We cross-checked respondents’ claim of nematocide, cestocide, ectoparasiticide, and anti-coccidial use with the label claim of reported products. Fisher’s exact test was used to detect significant differences between urban and rural data, and differences in treatment frequency for nematodes, cestodes, and ectoparasites between cats and dogs at the 5% level.

Cost-comparison

We estimated the treatment costs of anthelmintic products available in Canada using 2013 wholesale prices, average weights for cats and dogs (7 kg and 20 kg, respectively), and the recommended dosage for a single treatment course (12). Calculations were performed by 2 technicians and compared to ensure accuracy. Ear mite infestations were assumed to be bilateral, and for topical sprays, a dispersal rate of 5 to 7.5 g/kg body weight (BW) was used. As well, we simulated shelter purchasing practices by selecting product prices for bulk purchases where possible (e.g., 500 tablet bottles versus 50 tablet bottles).

Results

Overall, 50 of 78 urban shelters and 32 of 47 rural shelters participated in the survey (participation rates of 64% and 68%, respectively; Figure 1). One shelter declined to participate on the basis of confidentiality; all other non-respondents did not answer our telephone calls, return the e-mailed survey, or were unable to answer the survey questions. Most often, respondents reported their occupation as shelter directors/managers or shelter veterinarians, followed by veterinary technicians or animal care attendants. The median number of animals surrendered per shelter annually was 1850 (range: 400 to 14 000) in urban centers and 400 (range: 30 to 1300) in rural areas. There were no significant differences in treatment frequency between dogs and cats, and no significant differences in nematocide or endoparasiticide use between urban and rural shelters. Overall, 98% to 99% of shelters treated all dogs and cats for nematodes (Table 1), but only 27% of shelters treated all animals for cestodes. Only urban shelters reported using products to treat coccidiosis (7 of 50; 14%). The proportion of urban versus rural shelters that treated all dogs against cestodes was significantly different (18% versus 41%, respectively). The majority of shelters (70%) administered cestocidal agents to a subset of the population, generally after staff observed fleas on the animal or tapeworm segments in stool. Approximately half of all shelters (41% to 50%) administered ectoparasiticides to all animals. For both urban and rural shelters, fecal diagnostic tests were frequently conducted “as needed” (e.g., diarrhea, melena), and rarely for all animals. Treatment cost was the most important consideration for choosing anthelmintic products, followed by availability and whether or not the product was broad-spectrum.

Figure 1.

Location of urban and rural shelter survey participants (PE — Prince Edward Island; NS — Nova Scotia; NB — New Brunswick; NL — Newfoundland and Labrador; QC — Quebec; ON — Ontario; MB — Manitoba; SK — Saskatchewan; AB — Alberta; BC — British Columbia; YK — Yukon; NT — Northwest Territories; NU — Nunavut).

Table 1.

Summary of urban and rural companion animal parasite control protocols in animal shelters across Canada (2014)

	Urban N (%)	Rural N (%)	P-value	All N (%)
Fecal diagnostic test
Always	1 (2)	1 (3)	0.15	2 (3)
Sometimes	34 (74)	16 (53)		50 (66)
Never	11 (24)	13 (43)		24 (32)
Dogs
Nematocide
Always	49 (98)	31 (97)	1.0	80 (98)
Sometimes	1 (2)	1 (3)		2 (2)
Never	0	0		0
Cestocide
Always	9 (18)	13 (41)	< 0.001	22 (27)
Sometimes	39 (78)	18 (56)		57 (70)
Never	2 (4)	1 (3)		3 (4)
Ectoparasiticide
Always	22 (44)	12 (38)	0.36	34 (41)
Sometimes	26 (52)	16 (50)		42 (51)
Never	2 (4)	4 (13)		6 (7)
Cats
Nematocide
Always	49 (98)	32 (100)	1.0	81 (99)
Sometimes	1 (2)	0		1 (1)
Never	0	0		0
Cestocide
Always	9 (18)	13 (41)	0.07	22 (27)
Sometimes	39 (78)	18 (56)		57 (70)
Never	2 (4)	2 (6)		3 (4)
Ectoparasiticides
Always	27 (54)	14 (44)	0.59	41 (50)
Sometimes	21 (42)	16 (50)		37 (45)
Never	2 (4)	2 (6)		4 (5)

Overall, extra-label drug use (ELDU) was reported by most urban and rural shelters (85% and 72%, respectively). The most common ELDU was equine pyrantel pamoate (Strongid T; Zoetis Canada, Kirkland, Quebec), followed by equine ponazuril (Marquis paste; Bayer Healthcare, Toronto, Ontario), bovine ivermectin (Ivomec; Mérial Canada, Baie-D’Urfé, Quebec), and large animal fenbendazole (Safeguard; Merck Animal Health, Whitehouse Station, New Jersey, USA); these were used in 73%, 8.5%, 3%, and 3% of shelters, respectively.

Table 2 summarizes the wholesale treatment costs of anti-parasitic products commonly available in Canada. Costs ranged from $0.03 CAD (bovine ivermectin, Ivomec; Mérial Canada) for treating roundworms in 7 kg cats to $25.56 CAD (pyrantel pamoate and praziquantel, Drontal; Bayer Healthcare) for treating roundworms and tapeworms in 20 kg dogs. Of the topical treatments, Advantage Multi (imidacloprid and moxidectin; Bayer Healthcare) was efficacious against the greatest range of ectoparasite and endoparasite species, followed closely by Revolution (selamectin; Zoetis). Of the systemic treatments, Sentinel (milbemycin and lufenuron; Novartis Animal Health Canada, Mississauga, Ontario), Ivomec, Dolpac (pyrantel, oxantel, and praziquantel; Vétoquinol Canada, Cambridge, Ontario), and Drontal Plus (pyrantel and praziquantel; Bayer Healthcare) were labelled to treat the most parasite species; and Ivomec was least expensive when used extra-label.

Table 2.

Cost-comparison of commercially available anti-parasitic products (2013 Canadian dollars)

Trade name	Generic name	Dogs	Cats	Ecto-parasites									Endo-parasites										Wholesale cost (2013 CAD)
				Ear Mite (Otodectes)	Flea (Ctenocephalides)	Flea — larvicide	Lice (Unspecified)	Mange (Demodex)	Mange (Sarcoptes)	Tick (Dermacentor)	Tick (Rhipicephalus)	Tick (unspecified)	Heartworm (Dirofilaria)	Hookworm (Ancylostoma)	Hookworm (Uncinaria)	Roundworm (Toxascaris)	Roundworm (Toxocara)	Tapeworm (Dipylidium)	Tapeworm (Echinococcus)	Tapeworm (Mesocestoides)	Tapeworm (Taenia)	Whipworm (Trichuris)	Cost/dog (20 kg)	Cost/cat (7 kg)
TOPICAL
Canaural	Oily carrier	✓	✓	*																			21.98	21.98
Surolan	Oily carrier	✓	✓	*																			11.98	11.98
Hexamite	Allethrin	✓	✓	*																			2.30	2.30
Milbemite	Milbemycin	✓	✓	*																			11.13	11.13
Otomite Plus	Pyrethrins	✓	✓	*																			5.3	5.3
Ecto-Spray	Pyrethrins	✓	✓		*							*											3.11	0.97
Ecto-Soothe Plus (Shampoo)	Pyrethrins	✓	✓		*					*	*												6.34a	6.34a
Vet-Kem Ovitrol Plus (Spray)	Pyrethrins s-Methoprene	✓	✓		*					*	*												3.75	1.31
Vet-Kem Ovitrol Dual Action Collar	Propoxur s-Methoprene	✓	✓		*					*	*												7.69	7.71
Preventic LA Spray	Permethrin	✓	X		*					*	*												4.62	X
Revolution (dogs)	Selamectin	✓	✓	*	*		EL		*	*	*		*				*						10.8
Revolution (cats)	Selamectin	✓	✓	*	*		EL						*	*			*							8.69
Advantage	Imidacloprid	✓	✓		*		EL																7.99	7.56
Advantage II	Imidacloprid Pyriproxyfen	✓	✓		*	*	EL																8.23	N/A
Advantage Multi	Imidacloprid Moxidectin	✓	✓	*	*		EL	*	*				*	*	D	D	*					D	11.55	8.84
K9 Advantix	Imidacloprid Permethrin Pyriproxyfen	✓	X		*	*	EL					*											9.70	X
Profender	Emodepside Praziquantel	X	✓											*			*	*	EL	EL	*		X	9.47
SYSTEMIC
Ivomec	Ivermectin	EL	EL	EL			EL	EL	EL				EL	EL		EL	EL					EL	0.09	0.03
Heartgard Plus	Ivermectin Pyrantel	✓	X										*	*	*	*	*						4.03	2.43
ProHeart 6	Moxidectin	✓	X										*	*	*								21.18	13.34
Interceptor	Milbemycin	✓	✓			EL	EL	EL					*	*		D	*					D	4.57	4.57
Milbemax	Milbemycin Praziquantel	EL	✓										*	*			*	*	*		*		18.14	7.26
Trifexis	Milbemycin Spinosad	✓	X		*								*	*		*	*					*	11.17	X
Sentinel Flavor Tabs	Milbemycin Lufenuron	✓	X	EL	*		EL	EL	EL				*	*		*	*					*	7.75	X
Program Flavor Tabs	Lufenuron	EL	✓		*	*																	6.87	5.52
Comfortis	Spinosad	✓	✓		*																		8.17	7.83
Bravecto	Fluralaner	✓	X		*					*	*												N/A	N/A
Capstar	Nitenpyram	✓	✓		*																		2.99	3.33
Immiticide	Melarsomine dihydrochoride	✓	X										*										15.23	X
Pyran	Pyrantel	✓	✓											*	D	D	*						0.46	0.65
Strongid T (liquid)	Pyrantel	EL	EL											EL	EL	EL	EL						0.23	0.08
Dolpac	Pyrantel Oxantel Praziquantel	✓	X											*	*	*	*	*			*	*	7.99	X
Drontal Plus	Pyrantel Praziquantel Febantel	✓	X											*	*	*	*	*	*		*	*	10.07	X
Drontal	Pyrantel Praziquantel	EL	✓											*			*	*			*		25.56	5.11
Droncit (tabs)	Praziquantel	✓	✓															*	D	D	*		9.16	4.58
Cestex	Epsiprantel	✓	✓															*			*		13.76	4.15
Panacur Singles (Granule)	Fenbendazole	✓	EL											*	*	*	*				*	*	11.23	1.20
Lopatol	Nitroscanate	✓	EL											*	*	*	*	*			*		10.35	5.20

EL — Extra-label use; N/A — Not applicable; D — label claim for dogs only; X — Not available.

^aPrice per 236 mL bottle of shampoo.

^*Label claim for both cats and dogs.

Discussion

Caring for largely transient pet populations is a challenging work environment for frontline animal health care providers. Both publicly and privately funded shelters often have strict financial constraints as well as limitations in human resources and knowledge of infection control (2,3). Many organizations provide shelter to all animals brought to them, including strays, family pets surrendered for re-adoption, pets seized by animal protection officers, animals with serious medical conditions, and pets with owners in crisis. Animals might be handled frequently and by many different people (shelter staff and the public), thereby facilitating pathogen transfer between animals, and between people and animals. High levels of stress have also been observed in shelter animals, due to housing density, pre-existing disease, novel environment, disruptions to routines, and/or separation anxiety (13,14). Collectively these factors mean that shelters need to employ strict bio-security protocols and regionally appropriate prophylactic treatment regimens.

Our survey demonstrated that SPCA and HS shelters in Canada employ adequate nematode control for cats and dogs, but that cestocides, ectoparasiticides and parasite diagnostic tests were frequently used “as needed” to save time and money. This strategy would have a high level of success at shelters where ascarids were the most common parasite observed (6). However, focusing broad-spectrum deworming and parasite diagnostic tests on symptomatic animals could overlook those shedding protozoans (e.g., Sarcocystis, Giardia, Isospora, Cryptosporidium) or trematodes (e.g., Metorchis, Alaria), and those infected with heartworm (D. immitis). As well, parasite species and prevalence in companion animals differ by region, and protocols should be optimized to control locally endemic pathogens. For example, Giardia and Echinococcus multilocularis, two zoonotic parasites of public health concern, were recently demonstrated to have higher than expected prevalence in urban pets and wildlife in western Canada; neither of which would be eliminated by a nematocide (7,15,16). As health and behavior have been identified as the most important factors in successfully re-homing shelter animals, proper diagnosis and appropriate treatment ensure the optimal health of an animal prior to adoption, maximize retention by newly adoptive owners, and minimize risks to public health (17).

A higher percentage of rural shelters treated all animals for cestodes than did urban shelters, which reflects the increased endoparasitism in those animals with access to wildlife and insect vectors (5). Our sample group did not include privately managed rescue groups, some of which transport high risk animals from endemic to non-endemic parasite areas without examination by a veterinarian or diagnostic parasitology testing. Animals transported to Canada from the United States are at heightened risk of infection with parasites such as Dirofilaria, Leishmania, and Ancylostoma (2,18,19), which are not believed to be present, or broadly distributed across Canada. Animals transported within Canada from north to south are at heightened risk of rabies exposure. This practice puts other animals and handlers at risk of exposure, and contributes to pathogen range expansion (20).

In the current study, shelters identified cost as a major deciding factor in choosing anti-parasitic drugs, which is similar to shelters in the United States, where heartworm positive dogs are frequently untested, untreated, and/or ultimately euthanized (2). Likewise, shelters in this study used anthelmintics extra-label to reduce operating costs, and according to our cost-comparison, there was a 2- to 8-fold difference between using pyrantel pamoate in the form of Strongid T (a liquid nematocide approved for horses) versus Pyran tablets (a tablet nematocide approved for cats and dogs; Vétoquinol Canada, Lavaltrie, Quebec). Anti-parasite pharmaceuticals were also used extra-label to treat coccidiosis, which is a potentially serious illness caused by Isospora spp. in dogs and cats, and common in young animals (< 1 y old) housed in stressful and/or crowded environments (21). Sulfadimethoxine is commonly used to treat coccidiosis in Canada, but it is coccidiostatic rather than coccidiocidal, allowing some animals to continue shedding low levels of oocysts (21). Ponazuril (Marquis paste; Bayer Healthcare) is approved for the treatment of Equine Protozoal Myeloencephalitis. It also has anti-coccidial activity in dogs and cats and is proven to reduce oocyst shedding. Ponazuril is most efficacious when administered once daily for 3 d at 50 mg/kg BW and is low cost ($0.23 CAD to treat a 1 kg animal for 3 d) (21). Another option available in Canada, but not reported by our survey respondents, is toltrazuril (Baycox 5% solution; Bayer Healthcare), the parent drug of ponazuril. It is approved for the treatment of coccidiosis in sheep and swine. In field trials, toltrazuril administered as a single dose at 10 to 20 mg/kg BW suppressed oocyst shedding with no reported side effects, and also at low cost ($0.19 to treat a 1 kg animal once) (22). One additional advantage to using Baycox 5% solution is that it can be dosed more accurately for small animals than can Marquis paste.

Participation rates among urban and rural shelters were similar (64% and 68%, respectively); however, our sample groups were biased towards larger shelters with established protocols, and those with sufficient staff to participate in our survey. Our survey addressed in-house protocols only and was limited in that it did not measure shelter worker compliance. Likewise, we report only the efficacy of a protocol against 1 species of nematode, cestode, or ectoparasite, rather than comprehensive control of a protocol against all species within a category. Shelters that employed veterinarians or animal health technicians were more likely to complete surveys, as opposed to volunteer run organizations, whose workers often lacked knowledge about protocols. Wholesale drug calculations were performed with as much accuracy as possible, but in some cases estimates were required if a pharmaceutical company could not provide certain information (e.g., the number of doses per bottle). Our study also did not compare the efficacy of different formulations, which is also an important consideration when selecting a treatment. We strongly encourage all animal health practitioners to use the Decision Cascade, designed by the Canadian Veterinary Medical Association, when choosing pharmaceuticals for client-owned animals (23). Approved drugs, administered at the label dose, are the safest treatment course. Compounded drugs and ELDU should only be considered when Health Canada approved pharmaceuticals are not available in the appropriate concentration or formulation for dosing (23).