Review of Equine Cutaneous Leishmaniasis: Not Just a Foreign Animal Disease

Home , Canine leishmaniasis, Cutaneous leishmaniasis, Leishmaniasis, Leishmania aethiopica, Leishmania braziliensis, Leishmania infantum

MEDICINE UPDATE: DIAGNOSTICS AND TREATMENTS

Sarah M. Reuss, VMD, Diplomate ACVIM

Although long considered to be a foreign animal disease, cutaneous leishmaniasis has recently been identiﬁed in two horses in Florida with no history of international travel. Both horses were diag- nosed with Leishmania siamensis, an organism with zoonotic potential. Practitioners in the United States should have this disease on their differential list for horses with ulcers and nodules on the ears, head, and neck. Author’s address: University of Florida, Department of Large Animal Clinical Sciences, PO Box 100136, Gainesville, FL 32610; e-mail: sreuss@uﬂ.edu. © 2013 AAEP.

1. Introduction the parasites reside as intracellular amastigotes Leishmaniasis is a zoonotic disease most well de- within macrophages, where they replicate by binary scribed in people and dogs; however, cutaneous fission. When infected macrophages rupture, sur- leishmaniasis has been documented in horses rounding macrophages phagocytize the amastigotes around the world. Although cases have been seen and become infected. The disease is endemic in in the United States, most of these horses had a tropical and subtropical regions but is spreading history of recent importation from endemic areas. with global climate change. There are more than In 2012, the first autochthonous (non–travel-re- 30 species of Leishmania with a complex classifica- lated) case of equine cutaneous leishmaniasis in the tion scheme. The species of Leishmania vary with United States was published with the discovery of region, and different species are often incriminated Leishmania siamensis in a Morgan mare in Florida.1 to cause different disease manifestations. In the Since that time, a second horse in Florida (also with Eastern Hemisphere, the “Old World” species Leish- no history of international travel) has been diag- mania donovani, Leishmania infantum, Leishmania nosed with L siamensis.a Therefore, leishmaniasis tropica, and Leishmania aethiopica are commonly should be included in the differential list for horses found. In the Western Hemisphere, the “New in the United States with cutaneous lesions regard- World” species Leishmania braziliensis and Leish- less of their travel history or country of origin. mania mexicana are frequently found, most com- The goal of this article is to raise the awareness of monly in South and Central America. However, this disease amongst equine practitioners by review- L mexicana has been reported as the causative ing the etiology, pathogenesis, clinical syndromes, organism of some vector-transmitted outbreaks of diagnosis, and treatment of leishmaniasis. cutaneous leishmaniasis in people and dogs in Texas.2 L siamensis is a recently described species 2. Etiology/Method of Transmission that had not been previously reported in North Leishmaniasis is caused by the obligate intracellu- America until it was determined to be the etiologic lar protozoa of the genus Leishmania. In mammals, organism in both Florida horse cases.1 L siamensis

NOTES

256 2013 ր Vol. 59 ր AAEP PROCEEDINGS MEDICINE UPDATE: DIAGNOSTICS AND TREATMENTS was first described as the cause of autochthonous visceral leishmaniasis in two men in Southern Thailand3,4 but has also been identified as the cause of equine cutaneous lesions in central Eu- rope5 and a cow in Switzerland.6 In all mammalian species affected with leishmaniasis, the primary mode of transmission is believed to be by various species of sand flies. The promas- tigote stages of the protozoa are transmitted in the saliva of the female sand fly at the moment of blood feeding.7 Each species of Leishmania is adapted to transmission in certain species of sandflies: Phlebo- tomus spp in the Old World and Lutzomyia spp in the New World. The vector in equine transmission in the United States remains unidentified; however, the phlebotomine sand flies Lutzomyia shannoni and Lutzomyia vexator are found in Florida, where the two autochthonous equine cases were diag- nosed.8 Lutzomyia shannoni is known to use both humans and other mammals as hosts, and it has been incriminated as a vector of L braziliensis in Central and South America. It has also been shown experimentally to be capable of becoming infected with L infantum when feeding on ill L infantum-infected dogs.9 However, it is not known whether L shannoni will permit Leishmania de- velopment into infectious metacyclic parasites. Leishmania mexicana is considered endemic in south-central Texas, where the organism is main- tained within the ecosystem by small rodents and is presumably spread by a Lutzomyia spp (possibly Fig. 1. Cutaneous leishmaniasis in the left pinna of a 10-year- Lutzomyia diabolica).2 Although vector-borne old Morgan horse mare in Florida. transmission is the primary means of spread be- tween dogs in endemic areas, it is thought that vertical transmission (transplacental and trans- mammary) is probably the major means of spread in In Europe, L infantum has been reported as the dogs in non-endemic areas of the United States.10 causative agent of cutaneous leishmaniasis in The frequency of vertical transmission in endemic horses in Germany,14 Spain,15 and Portugal.16 regions is difficult to determine because of the high Recently, a report from central Europe identified an likelihood of vector contact. Ticks have been shown organism with 98% identity to L siamensis as the experimentally to be capable of transmission in cause of cutaneous lesions in four horses.4 Whereas dogs, and horizontal transmission by direct contact equine leishmaniasis is documented in Puerto Rico,17 with blood has also been shown.10 it is rarely seen in the continental United States. Historically, cutaneous leishmaniasis in the United 3. Clinical Manifestations States was seen in horses with a history of international travel or recent importation. Although autoch- Equine thonous cases may have been observed2, the first Cutaneous leishmaniasis has been documented in documented case occurred in 2011.1 To date, only horses around the world. Lesions are most com- cutaneous lesions have been documented in horses. monly observed as nodules on the head, pinnae, scrotum, legs, and neck. They may be solitary or Human multiple, and are often ulcerated (Fig. 1). No other Leishmaniasis is the second leading parasitic cause signs are seen, and visceral lesions have not been of death in people, after malaria. There are ap- reported. Equine leishmaniasis was first reported proximately 1.8 million new cases per year, making in Argentina in 1927. In South America, L brazil- this a top priority for the World Health Organiza- iensis has been identified as the causative organism tion. Three basic syndromes are seen in people: in horses.11,12 In one endemic region of Brazil, 26 cutaneous, mucocutaneous, and visceral. Cutane- horses, donkeys, and mules were examined. Cuta- ous disease presents as painless nodules, plaques, or neous lesions were found in 10 animals, and eight ulcers. In general, lesions heal spontaneously in animals (30.8% of the examined population) had immunocompetent individuals. Mucocutaneous le- parasites seen on histopathology of ulcer margins.13 sions involve the nares, nasal septum, pharynx, lar-

AAEP PROCEEDINGS ր Vol. 59 ր 2013 257 MEDICINE UPDATE: DIAGNOSTICS AND TREATMENTS ynx, and genitalia; and they can occur concurrently or 1 to 5 years after resolution of cutaneous lesions. These lesions will not heal spontaneously. Visceral leishmaniasis, otherwise known as “kala azar,” is a chronic, insidious disease that may be preceded by cutaneous lesions. Visceral leishmaniasis is usu- ally associated with species of the Leishmania donovani complex (L donovani, L infantum, Leishmania chagasi) and L tropica. Clinical signs include fe- ver, weight loss, anemia, anorexia, cough, diarrhea, and darkening of the skin. Splenomegaly, hepato- megaly, lymphadenopathy, thrombocytopenia, and leukopenia may all be present as the parasite in- vades the reticuloendothelial system. Visceral disease is fatal unless treated, and treated patients will remain carriers and can recrudesce if immuno- suppressed. Canine Fig. 2. Fine-needle aspirate of an ulcerated mass from a horse Dogs are the most commonly affected domestic spe- with cutaneous leishmaniasis exhibiting an intracellular amasti- cies, with 63% to 80% seropositivity in endemic ar- gote (arrow). Photo courtesy of Dr. Mark Dunbar. eas in which they are thought to be the primary reservoir for L infantum and maintain the disease in domestic cycles.10 In endemic areas, all breeds of dogs are affected. Dogs, like humans, can develop amastigotes. Immunohistochemistry can be used cutaneous or visceral disease. Cutaneous lesions to confirm the diagnosis of leishmaniasis and has can present as nonpruritic exfoliative dermatitis, been performed successfully in the horse.5,14,17 nodules, ulcers, and long, brittle nails. Visceral Culture and qPCR can be performed by the Cen- disease results in lethargy, weight loss, anorexia, ters for Disease Control and Prevention or by vari- anemia, splenomegaly, epistaxis, hematuria, me- ous university research labs. Isoenzyme analysis lena, chronic renal failure, and death. Ocular le- of cultured parasites has been the conventional ap- sions have also been reported and include proach for species identification. However, PCR conjunctivitis, keratitis, and uveitis. The majority and sequence analysis can identify the organism to of cases of canine leishmaniasis in the United States the species level more rapidly and with greater sen- have historically involved international travel. sitivity, depending on the targeted region.18 It is However, there have been reports of isolated cases worth noting in the context of equine leishmaniasis and outbreaks, primarily in foxhounds. In 2000, a that PCR methods used to detect Old World leish- New York kennel reported four foxhounds with L in- maniasis have been reported to fail to detect L sia- fantum visceral leishmaniasis without a history of mensis.1,5,6 Amplification of a 350–base pair travel. This led to widespread testing, and by 2005, internal transcriber spacer 1 (ITS1) fragment has 60 kennels in 22 states and two Canadian provinces been successful in identifying this organism.1,5 were found to have seropositive Foxhounds. Cur- Sequence analysis of the ITS1 amplification prod- rent studies of Foxhound kennels show a 9.8% sero- ucts classifies L siamensis as neither Old World nor prevalence; however, in high-risk kennels, the New World.5 percentage of quantitative polymerase chain reac- Serologic testing in humans and canines is the tion (qPCR)-positive dogs is 44.8%.10 primary diagnostic test used for surveillance of visceral infections but is less reliable for cutaneous 4. Diagnosis disease. Indirect fluorescent antibody (IFA) testing Microscopic evaluation of an impression smear or can be performed by the Centers for Disease Control. biopsy of the border surrounding the cutaneous le- Unfortunately, it may cross-react with antibodies to sion is often the preliminary means of diagnosis. Trypanosoma cruzi. One horse with L braziliensis There will be a marked inflammatory response, was positive for anti-Leishmania antibodies on and numerous intracellular protozoa will be seen IFAT11; however, IFAT in one horse in Germany with within macrophages and occasionally extracellu- confirmed L infantum cutaneous lesions on PCR failed larly. These 1- to 4-␮m intracellular organisms to yield a positive result.14 Cutaneous lesions in peo- have an eccentrically placed, basophilic, round nu- ple may also result in no detectable level of serum cleus and a rod-shaped kinetoplast oriented perpen- antibodies; however, skin testing for delayed type hy- dicular to the long axis of the oval nucleus (Fig. 2). persensitivity may be positive in human cutaneous This morphology is indicative of the amasitogote disease. Delayed type hypersensitivity reaction skin form of Leishmania. Electron microscopy will al- testing has been performed in the horse11 but is not low more detailed examination of the intracellular standardized. Anti–L infantum antibodies have been

258 2013 ր Vol. 59 ր AAEP PROCEEDINGS MEDICINE UPDATE: DIAGNOSTICS AND TREATMENTS found in clinically normal horses in endemic areas should be considered in the differential list for cuta- through the use of a protein-A enzyme-linked immu- neous lesions in horses; and cytology, histopathol- nosorbent assay (ELISA) and a specific lymphocyte ogy, and/or molecular diagnostics should be proliferation assay to L infantum.19 Other serologic performed on suspect lesions. Although this is not tests used in people and canines with visceral lesions a fatal disease in horses, we can and should consider include a kinetic-based ELISA and a K39-antigen– our equine patients as sentinels for this potentially based assay.20 Quantitative PCR may be a more sen- fatal zoonotic disease. sitive test, and can detect animals that are asymptomatic or have not yet seroconverted.10 References and Footnotes 5. Treatment 1. Reuss SM, Dunbar MD, Mays MBC, et al. Autochthonous Leishmania siamensis in Horse, Florida, USA. Emerg Infec Different species of Leishmania have varying re- Dis 2012;18:1545–1547. sponses to treatment. Systemic treatment is often 2. McHugh CP, Melby PC, LaFon SG. Leishmaniasis in Texas: indicated in humans to reduce the risk of dissemi- epidemiology and clinical aspects of human cases. Am J nation to the mucosa or viscera. Currently, the Trop Med Hyg 1996;55:547–555. standard treatment for people is intravenous admin- 3. Sukmee T, Siripattanapipong S, Mungthin M, et al. A sus- pected new species of Leishmania, the causative agent of istration of the pentavalent antimony compounds visceral leishmaniasis in a Thai patient. Int J Parasitol sodium stibogluconate or meglumine antimonite. 2008;38:617–622. Unfortunately, these drugs have potentially severe 4. Suankratay C, Suwanpimolkul G, Wilde H, et al. Autoch- side effects including arthralgia, myalgia, pancreati- thonous visceral leishmaniasis in a human immunodeficiency tis, and abnormal liver function tests, and results in virus (HIV)-infected patient: the first in Thailand and re- 21 view of the literature. Am J Trop Med Hyg 2010;82:4–8. treatment failure in 23.5% of cases. Intralesional 5. Mu¨ ller N, Welle M, Lobsiger L, et al. Occurrence of Leish- pentavalent antimony can be an effective alterna- mania sp in cutaneous lesions of horses in Central Europe. tive, resulting in higher drug concentrations at the Vet Parasit 2009;166:346–351. site of infection while reducing the risk of systemic 6. Lobsiger L, Mu¨ ller N, Schweizer T, et al. An autochthonous toxicity.22 In some endemic areas, drug resistance case of cutaneous bovine leishmaniasis in Switzerland. Vet 23 Parasitol 2010;169:408–414. for pentavalent antimony is seen. In the United 7. Secundino NFC, Freitas VCDE, Monteiro CC, et al. The States, pentavalent antimony can only be obtained transmission of Leishmania infantum chagasi by the bite of for military or investigational use from the Centers the Lutzomyia longipalpis to two different vertebrates. Par- for Disease Control and Prevention, thus limiting asites Vectors 2012;5:20. 8. Mann RS, Kaufman PE. The seasonal abundance of phle- clinical access. botomine sand flies, Lutzomyia species in Florida. J Am Mosq Other drugs that have been used for human and Control Assoc 2010;26:10–17. canine leishmaniasis include allopurinol, miltefos- 9. Travi BL, Ferro C, Cadena H, et al. Canine visceral leish- ine, amphotericin B in the lipid emulsion or lipo- maniasis: dog infectivity to sand flies from non-endemic ar- somal form, ketoconazole,18 paromomycin,24 eas. Res Vet Sci 2002;72:83–86. 10. Petersen CA, Barr SC. Canine leishmaniasis in North itraconazole, and cryotherapy. A randomized, dou- America: emerging or newly recognized? Vet Clin North Am ble-blind, placebo-controlled trial of oral fluconazole Small Anim Pract 2009;39:1065–1074. was found to be safe and shortened time to resolu- 11. Barbosa-Santos EGO, Marzochi MCA, Urtado W, et al. tion in people with cutaneous lesions.25 However, a Leishmaniasis disseminated by Leishmania braziliensis in a mare (Equus caballus): immunotherapy and chemotherapy recent Cochrane database review of 38 clinical trials assays. Mem Inst Oswaldo Cruz 1994;89:217–220. for cutaneous lesions through the use of different 12. Yoshida ELA, Correa FMA, Marques SA, et al. Human, interventions found an absence of randomized, con- canine and equine (Equus caballus) leishmaniasis due to trolled, trial-based evidence for alternative treat- Leishmania braziliensis (L braziliensis braziliensis)inthe ments including surgery, oral itraconazole and South-West region of Saô Paulo state, Brazil. Mem Inst Oswaldo Cruz 1990;85:133–134. fluconazole, rifampicin, metronidazole and cotri- 13. Aguilar CM, Rangel EF, Deane LM. Cutaneous Leishman- moxazole, intravenous or topical amphotericin B, iasis is frequent in equines from an endemic area in Rio de oral dapsone, photodynamic therapy, and laser and Janeiro, Brazil. Mem Inst Oswaldo Cruz 1986;81:471–472. cryotherapy.26 14. Koehler K, Stechele M, Hetzel U, et al. Cutaneous leish- Many of the reports of cutaneous leishmaniasis in maniasis in a horse in southern Germany caused by Leish- mania infantum. Vet Parasitol 2002;109:9–17. horses describe spontaneous regression of lesions. 15. Solano-Gallego L, Fernańdez-Bellon H, Serra R, et al. 5 11,17 Surgical resection, pentavalent antimony, and Cutaneous leishmaniasis in three horses in Spain. Equine amphotericin and fluconazole1 have all been used Vet J 2003;35:320–323. “successfully” in horses, but it is unclear how many 16. Rolaõ N, Martins MJ, Joaõ A, et al. Equine infection with would have resolved with no treatment. Leishmania in Portugal. Parasite 2005;12:183–186. 17. Ramos-Vara JA, Ortiz-Santiago B, Segales J, et al. Cutane- ous leishmaniasis in two horses. Vet Pathol 1996;33:731. 6. Summary 18. deAlmedia ME, Steurer FJ, Koru O, et al. Identification of Equine cutaneous leishmaniasis can no longer be Leishmania spp. by molecular amplification and DNA se- considered just a foreign animal disease. With cli- quencing analysis of a fragment of rRNA internal transcribed spacer 2. J Clin Microbiol 2011;49:3143–3149. mate change and the spread of vector habitats, 19. Fernandez-Bellon H, Solano-Gallego L, Bardagi M, et al. emerging diseases will continue to infiltrate the Immune response to Leishmania infantum in healthy horses United States equine population. Leishmaniasis in Spain. Vet Parasitol 2006;135:181–185.

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20. El-Moamly A, El-Sweify M, Hafeez M. Performance of rK39 25. Alrajhi AA, Ibrahim EA, De Vol EB, et al. Fluconazole for immunochromatography and freeze-dried direct agglutina- the treatment of cutaneous leishmaniasis caused by Leish- tion tests in the diagnosis of imported visceral leishmaniasis. mania major. N Engl J Med 2002;346:891–895. Parsitol Res 2012;110:349–354. 26. Gonzalez U, Pinart M, Rengifo-Pardo M, et al. Interventions 21. Ramanathan R, Talaat KR, Fedorko DP, et al. A species- for American cutaneous and mucocutaneous leishmaniasis. speciﬁc approach to the use of non-antimony treatments for Cochrane Database Syst Rev 2009(2). Art No. CD004834. cutaneous leishmaniasis. Am J Trop Med Hyg 2011;84:109– 117. 22. Palumbo E. Current treatment for cutaneous leishmania- a - sis: a review. Am J Ther 2009;16:178–182. Short MA. Kitchen DL. Gainesville, Florida (personal commu nication), January 2013. 23. Croft SL, Sundar S, Fairlamb AH. Drug resistance in Leish- b mania. Clin Microbiol Rev 2006;19:111–126. Mays MBC, MacKay RJ. Gainesville, Florida (personal com- 24. Salah AB, Messaoud MD, Guerdi E, et al. Topical Paromo- munication), circa 1992. mycin with or without gentamicin for cutaneous leishmaniasis. N Engl J Med 2013;368:524–532.

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