Peer reviewed ParasiTe ProTocols

Parasite ProtoCols For Your PraCtiCe Canine Protozoa Recommendations from the Companion Animal Parasite Council Susan E. Little, DVM, PhD, Diplomate ACVM, and Emilio DeBess, DVM, MPVM

The mission of the Companion Animal Parasite Council (CAPC) is to foster animal and human health, while preserving the human–animal bond, through recommendations for the diagnosis, treatment, prevention, and control of parasitic infections. For more information, including detailed parasite control recommendations, please visit capcvet.org.

rotozoan parasites, including vector-borne Vectors & Transmission. Many different tick species infections and intestinal protozoa, are respon- transmit species when feeding on dogs; the sible for a number of different diseases in dogs most common U.S. species include: P(Table, page 44). Although many infections are • B vogeli (formerly, B canis vogeli), transmitted by acquired by direct ingestion of infective stages, others Rhipicephalus sanguineus ticks may be transmitted by . These parasites are • B gibsoni; transmission with this species has been distributed worldwide or regionally. Accurate, prompt associated with dog fighting. diagnosis and appropriate, specific treatment are critical Transmission of any Babesia species can to managing and preventing protozoan parasitic dis- occur following blood transfusion.1 eases in dogs. Diagnosis. Dogs with babesiosis present with fever, anorexia, de- VectOr-BOrne InfectIOnS pression, and often, hemolytic ane- Babesia Species mia.1 Diagnosis is achieved by ex- Distribution. Worldwide, dogs may become infected amining stained blood smears for with Babesia canis, B vogeli, B rossi, B gibsoni, B con- characteristic piroplasms in erythro- radae, and other small and large Babesia species, some cytes (Figure 1). that have yet to be named.1,2 Treatment. Preferred treatment op- Figure 1. Piroplasms of a tions include:3 large Babesia species in • canine erythrocytes About This Series Imidocarb diproprionate for large Babesia species (B canis, B vogeli, B rossi) one of caPc’s principal achievements has • Atovaquone/azithromycin for small Babesia species been creating recommendations that support (B gibsoni, B conradae). practitioners in their efforts to protect pets and people from parasites. These recommendations Prevention. Infection prevention requires careful at- are based on peer-reviewed, published research tention to tick control and avoidance of fighting among findings and the collective parasitologic and dogs. clinical expertise of the caPc board. in this series, caPc board members will: Species • review the diagnosis, treatment, and control of Distribution. Hepatozoon americanum has only been common parasites of dogs and cats described in the U.S., while H canis is found worldwide.4 • suggest strategies for implementing specific Vectors & Transmission. H canis and H america- caPc recommendations in practice. num are transmitted to dogs by ingestion of the vec- The full recommendations are available at tor—ticks—rather than their bite. H americanum can capcvet.org. also be transmitted by ingestion of paratenic vertebrate hosts.

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Diagnosis. H americanum infection presents as se- and long-term therapy consisting of ponazuril or trim- vere, febrile disease, with lethargy, myalgia, and mus- ethoprim/sulfamethoxazole combined with clindamycin cle wasting commonly reported. It also infects skeletal and azithromycin, followed by long-term decoquinate and cardiac muscle, and induces pyogranu- therapy and pain management with nonsteroidal anti- lomatous myositis. Chronically infect- inflammatory drugs.5 ed dogs often develop periosteal Prevention. Tick control helps prevent infection by proliferative lesions on their long limiting the number of ticks ingested. Prevention of bones and bloodwork reveals H americanum also requires limiting consumption of profound neutrophilia. Clinical paratenic hosts, especially rabbits and rodents.6 disease with H canis is relative- ly mild by comparison.5 Leishmania Species Diagnosis of both Hepatozoon Distribution. Althought fairly uncommon in North Amer- species can be made by:5 ica, dogs are infected with Leishmania species through- • Identifying gamonts in leukocytes out much of the world. Infection has been diagnosed in on stained blood smears; gamonts Figure 2. Gamont of dogs imported from endemic areas, such as the Mediter- Hepatozoon americanum are rare in H americanum infection ranean basin and Central and South America. in canine leukocyte but much more common in H canis infection (Figure 2). Vectors & Transmission. In many areas of the world, • Polymerase chain reaction (PCR) of whole blood phlebotomine sandflies that have fed on an infected ver- • Histologic examination of muscle biopsy (more sensi- tebrate transmit Leishmania species to dogs. In the U.S., tive in detecting H americanum infection than PCR). transmission by sandflies has not been epidemiologically demonstrated, but canine infections are recognized, par- Treatment. H canis infection is treated with imidocarb ticularly in foxhound kennels, and are presumably ac- diproprionate. H americanum requires more aggressive quired by direct transmission between dogs.7

TAble. U.S. Canine Protozoa: routes of Acquisition, diagnostic Strategies, & Preferred Treatments trAnSMISSIOn DIAGnOSIS PreferreD treAtMent cAnIne VectOr-BOrne PrOtOZOA Babesia Tick bite Blood smear large Babesia species: species Blood transfusion Pcr of whole blood imidocarb diproprionate Dog fighting (B gibsoni) serology small Babesia species: atovaquone/azithromycin combination therapy Hepatozoon ingestion of ticks (H canis, H Blood smear H canis: imidocarb diproprionate species americanum) Pcr of whole blood H americanum: Ponazuril or ingestion of vertebrate Histologic examination trimethoprim sulfa combined paratenic host (H of muscle biopsy (H with clindamycin and americanum) americanum) azithromycin, followed by long- term decoquinate Leishmania sandfly bite impression smear of lesion Pentavalent antimonials species Direct dog-to-dog Pcr allopurinol transmission serology Trypanosoma stercorarian from kissing bug Blood smear Benzinidazole (not available in cruzi ingestion of infected bugs Pcr the U.s.) serology cAnIne VectOr-BOrne PrOtOZOA ingestion of oocysts Fecal flotation sulfadimethoxine species Ponazuril Cryptosporidi- ingestion of oocysts Fecal flotation Paromomycin um species Fecal iFa azithromycin Giardia species ingestion of cysts Fecal flotation Fenbendazole Fecal iFa Febantel Fecal elisa Additional treatment options and dosages for the medications listed in this table are available at capcvet.org (select CAPC Recommendations).

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Diagnosis. Infected dogs may Prevention. Preventing infection requires limiting ac- remain asymptomatic or can cess to kissing bugs by sealing kennels and keeping develop severe, chronic dogs inside. Limiting predation is also recommended disease, involving mus- because, although unproven, ingestion of infected reser- cle wasting, ocular signs, voir hosts is a suspected route of transmission.12 renal disease, and alope- Zoonosis. T cruzi is zoonotic and, in endemic areas, 8 cia and other skin lesions. people are readily infected from a feeding bug vector’s Diagnosis is made by serol- feces. In the U.S., most human infections are associated ogy or identification of amasti- with blood transfusion or travel to endemic areas.11 Figure 3. amastigotes of gotes in impression smears from Leishmania species from affected tissues (Figure 3); PCR InteStInAl PrOtOZOA ruptured macrophages assays are also available. Cystoisospora Species on impression smear Treatment. Canine leishmani- Distribution. is a common finding in dogs, asis is difficult to treat, although pentavalent antimoni- with some studies suggesting approximately 1% to 5% of als and allopurinol can be used. dogs may be infected worldwide. Prevention. In endemic areas, protecting dogs from Vectors & Transmission. Canine infection with Cys- sandflies by routine application of repellent insecticides toisospora species ( species) commonly occurs decreases transmission of Leishmania species9; isola- upon ingestion of:13,14 tion of infected dogs is recommended to prevent direct • Sporulated oocysts from an environment contami- transmission. nated with feces • Zoonosis. Dogs are a major reservoir host for leishmani- Transport hosts. osis—a zoonotic disease. Euthanasia of infected dogs has Diagnosis. Many infected been recommended to limit transmission to humans and dogs remain asymptom- other dogs, particularly in regions where vector-borne atic, developing immuni- Leishmania transmission is not yet endemic. ty to limit infection and

protect them from future canine Protozoa: recommendations from the companion animal Parasite council Trypanosoma cruzi infections; however, diar- Distribution. Trypanosoma cruzi is the agent of Ameri- rhea, weight loss, dehydra- can trypanosomiasis or Chagas disease. Autochthonous tion, and even death can occur Figure 5. oocysts of cases are occasionally reported from dogs in the south- in severe infections, particularly Cystoisospora canis on ern U.S., where natural maintenance cycles exist, and those in young animals.15 Infec- fecal float are common in parts of South and Central America and tions are diagnosed by fecal flota- Mexico.10,11 tion, which reveals the characteristic oocysts (Figure 5). Vectors & Transmission. Infection is transmitted from Treatment. Treatment with sulfadimethoxine, which is kissing bugs (triatominae) to dogs and humans. Canine labeled as effective against the enteritis associated with infections occur when infected kissing bugs are ingest- , or ponazuril is recommended. ed or the bugs’ feces, which contain the organism, are Prevention. Oocysts are resistant to environmental deposited on or around the skin wound created by their degradation; careful attention to sanitation, particularly feeding activity; infection is also transmitted transpla- in kennels and shelters where large numbers of young centally.12 dogs are cohoused, is necessary to prevent infection.15 Diagnosis. Dogs with acute dis- ease develop generalized Species lymphadenopathy, leth- Distribution. Cryptosporidium species infect a vari- argy, enlarged liver and ety of vertebrate hosts, including dogs and humans. Ac- spleen, and myocardi- tive infections are present in a very small percentage of tis. Chronic infection dogs; most of these are due to C canis, which rarely in- often results in dilative fects people.16 The more common zoonotic agent, C par- myocarditis.12 Trypomas- vum, is not known to occur in dogs. tigotes may be identified Vectors & Transmission. Oocysts of Cryptosporidi- on stained blood smears from Figure 4. um species are immediately infective when shed in the acutely infected dogs (Figure Trypomastigotes of feces, which usually occurs 3 to 6 days after infection.13 Trypanosoma cruzi on 4); serology and PCR are also blood smear of dog available. Diagnosis. Infections can cause secretory diarrhea, which can be particularly severe in immunocompromised indi- Treatment. Benznidazole, the drug of choice for treat- viduals. Diagnosis is by sucrose flotation of feces, but rec- ing T cruzi in dogs, is not available in the U.S., and in- ognizing minute oocysts can be difficult and use of a refer- fected dogs are often euthanized. ral parasitology laboratory is recommended.

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Treatment. Treatment is difficult—few drugs are con- APPlIcAtIOn tO clInIcAl PrActIce sistently effective against Cryptosporidium species in Protozoal parasites of dogs can critically affect canine dogs. and human health, with overt clinical disease from ca- Prevention. Canine infections are considered a low- nine protozoa most often seen in debilitated or young risk zoonosis; C canis has only been reported in immu- animals. Infected dogs often present with signs of dis- nocompromised humans in the U.S.16 ease; however, asymptomatic infections also occur, and some protozoa may live undetected within the host for Giardia Species years.8 Distribution. Infection with Giardia duodenalis is common in U.S. dogs.17 Identification Identifying protozoal infections largely depends on Vectors & Transmission. Infection occurs following ingestion of cysts from fecal-contaminated water, food, awareness so that appropriate diagnostic tests are pur- or fomites, or through self-grooming. The different as- sued, particularly with vector-borne infections. Careful semblages of G duodenalis are considered to be fairly history taking and physical examination, along with a host specific. judicious use of diagnostic tools, can lead to better man- agement and improved outcomes. Diagnosis. Following infection, trophozoites attach to intestinal villi, resulting in maldigestion, mal- Prevention absorption, and diarrhea. Diagnosis is INTESTINAL PROTOZOA. Prevention of infection with achieved by detection of: intestinal protozoa requires careful attention to envi- • Trophozoites in direct smear of ronmental sanitation. Re-infection following treatment feces 19 • Cysts on fecal flotation with zinc often occurs, particularly in canine giardiasis. sulfate (Figure 6) • Antigen in feces of symptomatic VECTOR-BORNE INFECTIONS. Canine vector-borne dogs. diseases are highly prevalent, increasing in distribu- Intermittent shedding of cysts and tion, and often difficult to treat; preventing infection by trophozoites can make direct micro- consistent use of insecticides and acaricides and limiting scopic identification of infection chal- exposure to ticks and other vectors are the Figure 6. cysts of lenging. most effective ways to protect dogs from these diseases. Giardia duodenalis on Treatment & Prevention. No drugs canine fecal float Protection are approved for treatment of canine giardiasis in the U.S., but fendbendazole and febantel Protecting dogs from protozoal parasites is critical to have shown effectiveness.18 Bathing dogs removes cysts human health. Some of these infections, such as Leish- adhered to the hair and helps prevent re-infection.19 mania species and T cruzi, are well recognized zoono- ses, while others, such as canine Cryptosporidium or Zoonosis. Giardia is a common infection in humans, Giardia infections, are considered to carry a very low although the most common assemblages found in zoonotic risk.8,12,16,20 Veterinarians should pay close at- humans are distinct from those most often found in tention to: 20 dogs. Human giardiasis contracted from a dog has • Limiting protozoal parasite infections in dogs not been conclusively demonstrated in North America. • Staying up-to-date on emerging zoonotic diseases. n

elisa = enzyme-linked immunosorbent assay; iFa = indi- Canine Protozoan Parasites: Zoonotic Potential rect fluorescent assay; Pcr = polymerase chain reaction

VectOr-BOrne InfectIOnS Zoonotic References 1. irwin PJ. Canine babesiosis. Vet Clin North Am Small Anim Pract 2010; Babesia species No* 40(6):1141-1156. Hepatozoon species No 2. Sikorski le, birkenheuer AJ, Holowaychuk MK, et al. Babesiosis caused by a large Babesia species in 7 immunocompromised dogs. J Leishmania species Yes Vet Intern Med 2010; 24(1):127-131. 3. di Cicco MF, downey Me, beeler e, et al. re-emergence of Babesia Trypanosoma cruzi Yes conradae and effective treatment of infected dogs with atovaquone and azithromycin. Vet Parasitol 2012; 187(1-2):23-27. InteStInAl PrOtOZOA 4. little Se, Allen Ke, Johnson eM, et al. New developments in canine Cystoisospora species No hepatozoonosis in North America: A review. Parasit Vectors 2009; 2(Supp 1):S5. Cryptosporidium species rare 5. Allen Ke, Johnson eM, little Se. Hepatozoon spp. infection in the United States. Vet Clin North Am Small Anim Pract 2011; 41:1221- † Giardia species rare 1238. 6. Johnson eM, Panciera rJ, Allen Ke, et al. Alternate pathway of * infection in humans with other Babesia species does occur. infection with Hepatozoon americanum and the epidemiologic † Human giardiasis from a dog source has not been importance of predation. J Vet Intern Med 2010; 23:1315-1318. conclusively demonstrated in North america. 7. Petersen CA, barr SC. Canine leishmaniosis in North America: emerging or newly recognized? Vet Clin North Am Small Anim Pract

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2009; 39(6):1065-1074. 8. Solano-Gallego l, Miro G, Koutinas A, et al. leishvet guidelines for the practical management of canine leishmaniosis. Parasit Susan E. Little, DVM, PhD, Diplo- Vectors 2011; 4:86. mate ACVM, is the Director of the Na- 9. Otranto d, de Caprariis d, lia rP, et al. Prevention of endemic canine vector-borne diseases using imidacloprid 10% and tional Center for Veterinary Parasitol- permethrin 50% in young dogs: A longitudinal field study. Vet ogy at Oklahoma State University’s Parasitol 2010; 172:323-332. 10. Kjos SA, Snowden KF, Craig TM, et al. distribution and Center for Veterinary Health Sciences, characterization of canine Chagas’ disease in Texas. Vet where she serves as Regents Profes- Parasitol 2008; 152:249-256. sor and the Krull-Ewing Chair in Vet- 11. esch KJ, Petersen CA. Transmission and epidemiology of zoonotic protozoal diseases of companion animals. Clin Microbiol erinary Parasitology. Her research fo- Rev 2013; 26:58-85. cuses on zoonotic parasites and tick- 12. barr SC. Canine Chagas’ disease (American Trypanosomiasis) borne diseases. She has been recognized for teaching excel- in North America. Vet Clin North Am Small Anim Pract 2009; 39:1055-1064. lence, receiving the Pfizer (Norden) Distinguished Teaching 13. dubey JP, lindsay dS, lappin Mr. Toxoplasmosis and other Award (1999, 2010) and national Student AVMA Excellence intestinal coccidial infections in cats and dogs. Vet Clin North Am Small Anim Pract 2009; 39:1009-1034. in Teaching Award (1998, 2005), and for her outstanding re- 14. Gates MC, Nolan TJ. endoparasite prevalence and recurrence search with the Pfizer Award for Research Excellence (2012). across different age groups of dogs and cats. Vet Parasitol 2009; Dr. Little received her DVM from Virginia Tech and completed 166:153-158. 15. lappin Mr. enteric protozoal diseases. Vet Clin North Am Small her PhD at University of Georgia. Anim Pract 2005; 35:81-88. Emilio DeBess, DVM, MPVM, is 16. lucio-Forster A, Griffiths JK, Cama vA, et al. Minimal zoonotic risk of from pet dogs and cats. Trends Parasitol the state public health veterinarian 2010; 6(4):174. with the Oregon Health Authority. His 17. Carlin eP, bowman dd, Scarlett JM, et al. Prevalence of Giardia primary job is to track zoonotic dis- in symptomatic dogs and cats throughout the United States as determined by the ideXX SNAP Giardia test. Vet Ther 2006; eases in both humans and animals in 7(3):199-206. Oregon. He has received 2 Director 18. barr SC, bowman dd, Heller rl. efficacy of fenbendazole Excellence Awards from the Depart- against giardiasis in dogs. Am J Vet Res 1994; 55:988-990. 19. Payne PA, ridley rK, dryden Mw, et al. efficacy of a ment of Human Services in Oregon. combination febantel–praziquantel–pyrantel product, with or Dr. DeBess conducts surveillance projects related to zoo-

without vaccination with a commercial Giardia vaccine, for canine Protozoa: recommendations from the companion animal Parasite council treatment of dogs with naturally occurring giardiasis. JAVMA notic diseases, including leptospirosis, toxoplasmosis, cryp- 2002; 220:330-333. tococcosis, West Nile virus, and tick-borne illnesses. He re- 20. Covacin C, Aucoin dP, elliott A, Thompson rC. Genotypic ceived his DVM from University of California–Davis. characterisation of Giardia from domestic dogs in the USA. Vet Parasitol 2011; 177:28-32.

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