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Chiara Noli DVM, DipECVD
INTRODUCTION
Dr Chiara Noli graduated atthe University of Milan in Leishmaniasis is a disease of human beings and animals caused by the protozoan parasite of the genus Leishmania. Dogs usually develop the systemic (visceral) form of infection, with a highly variable clinical appearance. Canine leishmaniasis may be difficult to diagnose and frustrating to treat. Dogs are considered the main reservoir for visceral leishmaniasis in humans.
Diploma of the EuropeanCollege of VeterinaryDermatology. Since 1996 she ETIOLOGICAL AGENT
works as dermatologyconsultant and Leishmania organisms belong to the genus Protozoa, the order Kinetoplastida and the family Trypanosomidae. The parasite requires two different hosts, a vertebrate and an insect, to complete practice in Milan and in other clinics in Northern Italy. She is its cycle. The flagellate (promastigote) form is about 10–15 µm long Past-President of the Italian Society of Veterinary Dermatologyand Board Member of the European Society of Veterinary and is found in the insect vector and in laboratory cultures Dermatology. Dr Noli is author of a number of Italian and (Figure 1). In the vertebrate host the parasite is observed in the
international papers and of two book chapters. She lectures at amastigote form (i.e., without flagellum), smaller (2–5 µm), and with national and international meetings and at veterinary a visible rod-shaped kinetoplast (Figure 2). The latter is a
mitochondrial structure rich in DNA, associated with the flagellum.
The amastigotes are often seen in the intracellular position,particularly in macrophages, where they are able to survive and KEY POINTS
Several Leishmania species and subspecies, responsible for ● Canine visceral leishmaniasis is a severe systemic different clinical diseases in man and in the dog, have been identified disease caused by the diphasic protozoan parasite (Table 1). Their classification is very complicated: initially they were
Leishmania infantum in the Old World and classified following parasite morphology, insect vector, type of lesions, serological tests, and geographical distribution (1). Todaymore advanced techniques, involving isoenzymatic patterns, DNA ● The geographical distribution of the disease is peptide mapping, monoclonal antibodies, cell membrane structure dependent on its insect vector, the sandflyPhlebotomus spp. in the Old World and Lutzomyiaspp. in the New World.
● Common clinical signs are skin lesions, weight loss, anorexia, lymphadenopathy, ocular lesions, nasalbleeding, locomotory problems, and muscle atrophy. ● Chronic enteritis and renal failure are the most ● Frequent clinical laboratory findings are polyclonal Figure 1 Schematic drawing of Leishmania spp. promastigotes.
hyperglobulinemia, hypoalbuminemia,hyperprotinemia, a slight increase in liver enzymes,non-regenerative anemia and thrombocytopenia,azotemia, and creatininemia.
● The definitive diagnosis is obtained by direct observation of the parasites or serological means.
● The best available therapy today is the combined use of pentavalent antimonial agents withallopurinol.
● The prognosis for a complete cure is guarded.
Figure 2 Amastigotes of Leishmania infantum in a macrophage from a
● Dogs are the main reservoirs for human visceral cytological preparation of a fine needle aspiration biopsy of anaffected lymph node-Hemacolor, 1000ן. Courtesy of Dr. Fabia Scarampella. analysis, and fatty acid analysis have identified at least 17 species and subspecies (2). The most accepted classification worldwide is based on isoenzyme electrophoretic analysis. Populations of Leishmania species, their distribution and the
parasites with similar isoenzyme patterns are called zymodemes.
disease they cause in dogs and humans
Another classification is based on analysis of kinetoplast DNA with
restriction enzymes and recognizes different schizodemes.
Old World
Leishmania infantum
EPIDEMIOLOGY
Leishmania infantum is responsible for the Old World canine New World
visceral leishmaniasis. This species, with different zymodemes, is present in all countries around the Mediterranean Sea, in Portugal, West, East and North Africa, the Middle East, India, and China (2, Leishmania braziliensis Mucocutaneous 3). Its geographical distribution reflects the living area of the insectvector Phlebotomus spp. This is a small (2–3 mm), silent, nocturnal,blood-sucking sandfly belonging to the family Psychodidae.
is rarely seen in very young and very old dogs because of the long Phlebotomi are mostly found in rural areas between 100 and 800 m incubation period (usually more than four months) and the very low above sea level and spend their life in a limited area, not exceeding Visceral leishmaniasis in human beings is caused by the same In some endemic areas of the Mediterranean the incidence of parasites but is much less common than the canine variety. Most seropositivity is about 5–15% of the canine population (4–8). Of human patients have an immunosuppressive disease, such as HIV, or seropositive dogs, 20–40% are asymptomatic carriers and may are receiving anti-tumor chemotherapy. Direct transmission from represent an unrecognized reservoir of the infection for other dogs dogs to humans without an insect vector is probably impossible, and human beings (6–8). In some areas the incidence of clinical although whether contact with open mucosal lesions is entirely disease is about 3.5 new cases per 100 dogs per year.
The endemic area, and the total number of affected animals, has been increasing in recent years (4, 6). This could reflect greater PATHOMECHANISM OF INFECTION
mobility of dog owners with their pets and/or a change in theclimatic conditions that favor the sandflies’ survival in new areas.
The insect vector sucks blood from an infected vertebrate and Leishmania chagasi is the microorganism that causes the ingests the amastigote parasites. These multiply in the intestinal visceral disease in dogs and humans in the New World. This parasite tissues and transform into promastigotes. The flagellum enables is inoculated by the bloodsucking sandfly Lutzomyia spp. and its them to migrate into the insect’s sucking apparatus. With each blood distribution includes Central and South America and small endemic meal parasites are deposited into the skin of a new host. They are areas in North America (Ohio, Alabama, Michigan) (9). In Oklahoma internalized by macrophages and other dendritic cells, where they a case involving L. infantum has been described (2). The visceral can survive and multiply. Leishmanial organisms are able to live in disease caused by L. chagasi is very similar to the Old World visceral the endothelial reticulum of host cells because they neutralize the leishmaniasis, which will be described later.
host cell’s pH and detoxify oxygen metabolites. In macrophages the Other species of Leishmania which may infect dogs and humans parasites multiply by binary fission until they rupture the cell and are L. braziliensis in Brazil, L. tropica in the Mediterranean area, and L. mexicana in Central America and Texas, USA (2). While the It has recently been recognized (15) that Langerhans cells and latter has never been associated with clinical disease in dogs other dendritic cells may also be infected by the parasite. These cells (although antibodies against it have been found in the serum of process and present parasitic antigens on their surface and are able animals living with affected owners), L. braziliensis and L. tropica to prime naive T helper (Th) cells and direct their response to the can cause cutaneous nodules and mucosal ulceration in dogs (10, infection (16). Resistance to infection depends on a strong Type 1 11). Recently L. mexicana has been isolated from nodular cutaneous T-helper response (Th1), which involves production of cytokines lesions in a cat in Texas (12). Rodents, and not dogs, are considered such as interferon gamma (IFNg), tumor necrosis factor (TNF), the main reservoir of these species of Leishmania.
interleukin (IL) 2 and IL 12. These cytokines stimulate the cell- The cases of canine leishmaniasis diagnosed in non-endemic mediated immunity which eliminates the infection. Animals that areas are usually in animals which have been imported from endemic mount a strong Th1 response may have transitory positive serum areas or which have been living there for some time. Occasionally, antibody titers or may temporarily harbor the parasites before they infections following even a short vacation have been reported.
However, autochthonous cases have occasionally been described in In other individuals disease occurs as a consequence of a Type 2 countries where Phlebotomus spp. are absent (13, 14). In these T-helper response (Th2), with production of IL4, IL5, IL6 and IL10, cases the affected animals were born in non-endemic countries and which in turn promote B-cell proliferation and antibody production.
had never traveled abroad, although they had been in contact with Unfortunately these antibodies are not protective and may even be infected animals. This suggests the existence of an alternative insect detrimental, due to the formation of immune complexes and their vector – possibly a tick – or other ectoparasite. In one case a dog subsequent deposition in basement membranes. Antibody-mediated born in a non-endemic area from an affected bitch developed the opsonization of parasites may even increase phagocytosis by disease, suggesting the possibility of transuterine transmission (14).
macrophages and their subsequent parasitosis, according to some The disease may occasionally be transmitted as a result of blood authors (2). The cell-mediated immune system of susceptible dogs is impaired, and lymphocytes have decreased proliferative capacities in There is no age, breed, or sex predilection for the infection, vitro if stimulated with Leishmania antigens (17, 18). although it is thought that toy breeds are less affected, as they often Infected animals may present with either reaction pattern – that have an indoor lifestyle. Furthermore, in endemic areas, the disease is, either they develop a progressive disease with a fatal outcome, or T H E W O R L D ’ S L E A D I N G A U T H O R I T Y O N P E T C A R E A N D N U T R I T I O N
Relative prevalence (%) of different signs in
cutaneous leishmaniasis (signs with a prevalence of
>4% only) (2, 3, 20, 25)
Generalized lymphadenomegaly, symmetrical Skin lesions (see Table 3)
Figure 3 Dog with leishmaniasis: weight loss and generalized scaling
Acute form of leishmaniasis: fever and generalized lymphadenopathy and absence of skin lesions Relative prevalence (%) of different skin lesions (on
Severe renal failure without other signs of leishmaniasis 4 total of affected animals) (3, 20, 25)
they stay asymptomatic. However, in the natural disease both Th1and Th2 cellular subtypes are activated and the variability of the clinical signs and severity of the disease depends on the balance between these two systems (17). Asymptomatic animals represent 20–40% of the seropositive population (6–8). Of these about 80% will The incubation period is very long – between one month and seven years. In this period the microorganisms disseminate widely, with a predilection for the bone marrow, lymph nodes, spleen, and Damage caused by the parasite depends on two factors (19): ● Direct action on the tissues, resulting in the formation of non- suppurative inflammatory lesions in skin, liver, intestines,kidneys, eyes, and bones.
● Indirect damage caused by immune complex deposition in the joints and in the basement membranes of kidneys, blood vessels,and eyes, resulting in vasculitis, glomerulonephritis,polyarthritis, and uveitis.
CLINICAL DISEASE
Several organs may be affected, as parasites have been found in every part of the body, except, probably, the central nervous system.
For this reason leishmaniasis may have several different clinical
features. The relative prevalence of the different signs reported in
the literature is summarized in Table 2.
Figure 4 Dog with alopecia and scaling dermatitis on the ear.
The main presenting signs are weakness, decreased physical activity, skin disease and weight loss (Figure 3). The dogs usually
(22) as well as acute fatal hemorrhagic enteritis (20) have both been appear much older than they are because of the prominent muscular described associated with leishmaniasis. Enteritis may be the result atrophy, particularly on the head. Anorexia, if present, is probably of direct parasitic damage (granulomatous enteritis) or consequence related to renal failure. Weakness and decreased activity may be the of the renal failure. A case of acute hemorrhagic pancreatitis has consequences of anemia, muscle atrophy, polyarthropathy, or chronic renal failure. Locomotory problems are not very frequent and A moderate to severe renal insufficiency is often seen in affected include shifting leg lameness, due to immune-mediated polyarthritis, dogs. Histopathologically, two types of renal lesions have been polymiositis, and bone lesions, in which parasites are found in described (14): membranous glomerulonephritis and an extra- granulomatous inflammatory groups (20, 21). membraneous glomerulonephritis, both a consequence of immune- Leishmanial organisms multiply in the macrophages of the liver, complex depositions. Proliferative lesions have rarely been seen.
causing a chronic active hepatitis and, occasionally, palpable liver Associated proteinuria may lead to nephrotic syndrome and enlargement, vomiting, polyuria and polydipsia, anorexia, and weight uremia, which is the main cause of death in affected dogs. An loss. Chronic ulcerative colitis with large bowel diarrhea and melena acute, rapidly fatal renal insufficiency, without other signs of Characteristicappearance ofulceration due tovasculitis on thepinnae. Figure 5 Histological appearance of leishmaniasis in the skin
(alopecic scaling form): numerous parasitic bodies are seen in
macrophages in the subepidermal dermis-Hematoxilin-Eosin, 500ן.
Arrows: macrophages full of parasitic bodies.
Figure 8 Nodular leishmaniasis: several small cutaneous nodules are
visible on the elbow.
rest of the body. Histologically, a diffuse infiltrate of macrophages,lymphocytes and plasma cells is observed in the dermis and Figure 6 Nasal depigmentation and ulceration and epistaxis.
occasionally subcutis. Parasites, which may be seen in high numbers inside macrophages (Figure 5), reach the skin by vascular
dissemination and their presence in the dermis represents the direct
cause of the dermatitis. Dogs with this form are the most immune Heart disease and thrombosis have been described (26, 27), but competent of all affected animals (16).
seem rather infrequent. Epistaxis, often unilateral, is frequentlyseen, and is considered the result of both ulcerative lesions of the Ulceration (23%) (Figures 6 and 7), particularly affecting bony
nasal mucosa and/or impaired coagulation, due to hyperglobulinemia prominences, mucocutaneous junctions and extremities. Histological and thrombocytopenia (2). Clinicians should note that
features include ulceration with a mixed infiltrate and very few concurrent ehrlichiosis may complicate leishmaniasis in some
parasites. Ulceration may occur due to the direct action of the areas of the world, and, particularly, may contribute to the
parasites or to the necrotizing vasculitis caused by immune complex hematological abnormalities cited above.
deposition (25). Dogs with this pattern probably have an Lymphadenopathy, local or generalized, is one of the most consistent signs, although occasionally it may be absent. There is a Multiple nodules of variable sizes, from a few millimeters to
proliferation of B-cell regions, and a depletion of T-cells.
10 cm (12%) (Figure 8). Histologically there are accumulations of
Cytologically the lymph nodes appear strongly reactive, with the macrophages and high numbers of parasites are observed. Dogs with presence of plasma cells, eosinophils, and macrophages, some of this reaction pattern may have an extremely ineffective immune response against the infection (16) as Langerhans cells are Antibodies in the aqueous humor and cerebrospinal fluid, spongiform neuronal degeneration in the brain and cerebellum,mobilization of glial cells, and accumulation of amyloid have recently A generalized sterile pustular dermatosis (4%) on the trunk.
been described, associated with visceral leishmaniasis in dogs (28).
Histological features include subcorneal pustules with mild dermal, Skin lesions are frequent in canine leishmaniasis. The relative non-suppurative infiltrate and very low numbers of parasites. The prevalence of the different cutaneous signs is shown in Table 3. A
pathogenesis of this form is unknown.
study by Ferrer and co-workers established an association between In some dogs more than one pattern may be present, perhaps the type of skin lesions and the level or immunocompetence of the reflecting the balance between a cell-mediated and a predominantly affected dogs (29). They recognized four main patterns of antibody-mediated response. Other less frequent skin lesions macroscopic and microscopic skin lesions, with different prognostic associated with leishmaniasis are nasal and digital hyperkeratosis, onychogriphosis (Figure 9), paronychia, nasal and oral
Symmetrical alopecia and a silvery scale (Figure 4) is the
depigmentation, localized hyperpigmented hyperkeratotic plaques most common presentation, and is reported in 60% of dogs with skin similar to nevi, ulcerative stomatitis, and nodular dermatofibrosis disease. The lesions often start on the head and then spread to the without renal lesions, which disappear with treatment (20).
T H E W O R L D ’ S L E A D I N G A U T H O R I T Y O N P E T C A R E A N D N U T R I T I O N
Clinical laboratory findings in dogs with visceral
leishmaniasis (2, 3, 19, 20, 25)
Hyporegenerative, normocytic normochronic anemia Leukopenia (normal or low lymphocyte count) scleritis, and retinal hemorrhage. Iridocyclitis has been observed indogs undergoing treatment and is considered by one author (13) asan allergic manifestation, similar to post-kala-azar leishmaniasis inhumans.
CLINICOPATHOLOGICAL FINDINGS
Clinical laboratory abnormalities and their relative prevalence Figure 10 Ocular lesions: blepharitis, keratoconjunctivitis sicca and
(as reported in the literature) are summarized in Table 4.
The most frequent abnormality is hyperglobulinemia, due to polyclonal B-cell activation and antibody production.
Hypoalbuminemia may be present and is the result of protein-losing
nephropathy, liver disease, and malnutrition. Serum protein
electrophoresis has a typical form, strongly suggesting leishmaniasis
(Figure 11): a decrease of albumin is associated with an increase in
beta- and gamma-globulins. Beta-1 and beta-2 globulins increase in
the initial phase of the disease, followed by beta-3 and gamma-
globulins. Monitoring serum protein electrophoresis is considered
the best way of assessing response to treatment.
Thrombocytopenia and non-regenerative anemia may be the result of chronic leishmaniasis but the potential for concurrentdiseases to complicate the hematological picture should not beoverlooked.
DIFFERENTIAL DIAGNOSES
The differential diagnoses of leishmaniasis are legion, since its clinical appearance is extremely variable. The alopecic desquamative Figure 11 Characteristic appearance of serum protein electrophoresis
dermatitis, if not associated with systemic signs, may look similar to (red line) as it appears during leishmaniasis. demodicosis, keratinization disorders, sebaceous adenitis, and Recently a mucosal form, characterized by tissue proliferation on the pyoderma. The ulcerative lesions have to be differentiated from lupus penis, tongue, in the nose, and in the mouth, has been described erythematosus, other causes of vasculitis, deep mycoses, and (30). In addition, histological features of interface band-like cutaneous neoplasia. Differential diagnoses of the cutaneous lymphoplasmocytic cellular dermatitis mimicking lupus nodules are several skin tumors, sterile or infective granulomas, and erythematosus have been described with leishmaniasis (3).
nodular dermatofibrosis. Any pustular diseases, including pyoderma, Ocular lesions involve mainly the anterior segment of the eye pemphigus foliaceus, and demodicosis, are differential diagnoses. (Figure 10). Periorbital dermatitis and associated blepharitis is one
If systemic signs are present, leishmaniasis may be confused of the most common clinical signs. Keratoconjunctivitis sicca may with other infections, such as ehrlichiosis; clinically they may be occur, probably due to the direct destructive action of the parasites very similar, although in ehrlichiosis platelet counts are often on the lachrymal apparatus (31). Other lesions include extremely low and petechiae and hemorrhages are often seen. The granulomatous conjunctivitis refractory to usual treatments, generalized lymphadenopathy has to be differentiated from keratitis, granulomatous uveitis, immune complex-mediated anterior neoplastic lymphoproliferative diseases (malignant lymphoma).
uveitis associated with corneal edema and closed-angle glaucoma, Polyarthritis, glomerulonephritis, vasculitis, and ulcerative skin lesions are features observed also in systemic lupus erythematosus more numerous in the alopecic hyperkeratotic or nodular (SLE). Furthermore the histological appearance of lupus dermatitides, but can be very scarce or absent in other cutaneous erythematosus and of leishmaniasis may be very similar. The forms, such as the ulcerative or the pustular form. In order to differentiation of leishmaniasis from SLE may be very difficult, as up increase the sensitivity of this test, immunohistochemical and to 30% of the dogs with visceral leishmaniasis may have a (weakly) immunocytochemical techniques have been developed (34). These positive antinuclear antibody (ANA), 10% may have a (weakly) methods achieve the selective demonstration of the parasites by positive Coombs test (19) and 13% may have a positive lupus Leishmania spp. can be cultured and isolated from infected Affected animals may have other concomitant diseases, possibly tissues in Novy-MacNeal-Nicolle (NMN) medium, where they can be due to their weak cell-mediated immune responses, such as observed in the promastigote form. Sensitivity tests to different demodicosis (25), dermatophytosis (3), and hemoparasitosis such as drugs may be performed on these cultures. Parasite cultures are not routinely used in veterinary medicine, because they are difficult andexpensive to perform and because they do not always yield positive DIAGNOSTIC PROCEDURES
The diagnosis of canine visceral leishmaniasis is difficult for Serological tests
Several serological tests, which measure circulating antibodies, ● The clinical signs are very variable and may look similar to other have been developed. Among these, indirect immunofluorescence (IFAT), Dot-ELISA and direct agglutination test (DAT) are currently ● The histopathological appearance is extremely nonspecific, and commercially available (18, 35–38). These tests usually have a high may be similar to that of other infectious or immune-mediated sensitivity and specificity (80–100%) but cannot be used as the only means of diagnosis as they may give false positive results in some ● Currently, no available diagnostic test can offer a specificity and healthy, resistant dogs which have previously come into contact with the parasite. False negative results may also occur in some affecteddogs which have not produced antibodies (prepatent phase) (20, 36).
The clinical appearance of the affected dog may suggest the In the latter case it is advisable to repeat the test after six to eight diagnosis but confirmation of the diagnosis is necessary. Three main weeks. Furthermore, the serologic titers are not proportionate to the severity of the clinical disease (36, 38) and are not suitable as a ● Parasitological techniques, whose aim is to visualize the means of monitoring treatment efficacy because antibody titers may remain measurable, even after clinical cure (33).
● Serologic tests, which identify circulating anti-leishmanial Molecular methods
● Molecular methods (polymerase chain reaction), where parasite A polymerase chain reaction (PCR) technique has been DNA is amplified and detected in host tissues.
developed recently and is a highly sensitive, and specific, diagnostictest for leishmaniasis (39). Parasitic kinetoplast DNA in liver, spleen, Parasitological techniques
skin, lymph node, and bone marrow biopsies or blood is selectively These have a specificity of 100%, but may have a very low identified and amplified (33), and both fresh and formalin-fixed sensitivity. The identification of leishmanial organisms in cytological paraffin embedded tissue can be used for this technique. This test preparations made from fine needle aspiration biopsies of lymph can identify the presence of parasites, even in animals which have nodes and bone marrow is rapid and easy. Bone marrow samples been clinically cured for years (40). Unfortunately, PCR for may be collected with a normal needle from the costochondral Leishmania spp. is currently only available in specialized junctions or with a spinal needle from the iliac crest or sternum. The cytological smears are best stained with May-Gruenewald-Giemsa,and the parasites appear as small oval bodies (2–5 µm) containing a TREATMENT
dark nucleus and a small kinetoplast in a perpendicular position
(Figure 2). In bone marrow smears leishmanial organisms are found
Although treatment in the dog achieves clinical cure, it rarely almost exclusively in macrophages, whereas in cytological results in complete elimination of the parasites and recurrences are preparations from lymph nodes they are frequently observed in an frequent. No drug has yet been developed that safely and quickly extracellular position, probably due to cell rupture during the sample eliminates the infection. Current research aims at new therapeutic collection and preparation. No relationship has been observed protocols with drugs already in use and the development of new between the severity of the clinical disease and the number of drugs (41). Current treatment protocols are summarized in Table 5.
parasites found in cytological smears (20).
Before starting treatment, a complete blood count, biochemical Leishmanial organisms may also be observed occasionally in profile and urine analysis (including a quantitative test such as impression cytological preparations obtained from beneath crusts urine protein:creatinine ratio) should be performed in order to and scales, or by fine needle aspiration biopsies from cutaneous assess the renal and hepatic status. Furthermore, it is necessary to nodules. Unfortunately, the sensitivity of cytology as a diagnostic obtain a serum protein electrophoresis profile as a basal value for tool for canine leishmaniasis is low: bone marrow smears may be subsequent comparison and evaluation of treatment efficacy. positive in only about 50–70% of the infected animals (25, 33), andlymph node smears in only about 30% of the cases. This technique Pentavalent antimonials
also relies strongly upon the skill of the person performing it and on N-methylglucamine (meglumine) antimonate is currently the the time devoted to searching for the parasites in the smear, which drug of choice for canine visceral leishmaniasis. In some countries should not be less than 10 minutes per sample. this drug is not available and sodium stibogluconate is used in its Leishmanial organisms may also be observed in histological place. Their mechanism of action is not clear: they may inhibit some sections stained with Hematoxylin-Eosin or with Giemsa. They are parasite glycolytic enzymes. Meglumine antimonate is not absorbed T H E W O R L D ’ S L E A D I N G A U T H O R I T Y O N P E T C A R E A N D N U T R I T I O N
Allopurinol
Allopurinol is a hypoxantine analog. Leishmanial organisms are Treatment regimens for canine visceral
not able to synthesize purines and have to use the host molecules.
leishmaniasis
Allopurinol is incorporated into the parasite’s RNA and alters proteinsynthesis, inducing synthesis of abnormal proteins. As mammals are able to synthesize purines, this drug has a very low toxicity for these species. Allopurinol has a parasitostatic effect, and is best combined with other antileishmaniacal drugs, such as meglumine antimoniate (see above) or amphotericin B (see below) in order to potentiate 10–30 mg/kg every 12 hours PO 9–12 months their effect and obtain longer remission periods. There are few Amphotericin B 0.5–0.8 mg/kg twice weekly reports of the successful use of allopurinol alone (38), although this can represent the sole therapeutic choice in countries where antimonial compounds are not readily available (47).
interrupt for 2 weeks ifcreatinine > 25 mg/l Amphotericin B
Amphotericin B is a polyenic antibiotic produced by Streptomyces nodosus, currently indicated by intravenous administration for systemic and deep mycoses. It acts by irreversibly binding to ergosterole, a main component of the leishmanid cell membrane, causing its disruption and parasite death. Amphotericin B has some affinity to mammalian cholesterol and is toxic, causing a decrease in renal blood perfusion, renal filtration, creatinine clearance, and focal tubular necrosis. Other side effects include phlebitis, hyperthermia, and vomiting (48). In order to minimize the side effects it is diluted in 5% dextrose or in saline and administered by slow intravenous infusion (up to 5 hours). The drug is administered on alternate days at a dose rate of 0.15–0.5 mg/kg untila cumulative dose of 8–12 mg/kg has been given. Plasma creatinine if given by mouth and must be injected, preferably every 12 hours, as should be measured before each administration in order to assess it has a very short half-life and is quickly eliminated in urine (42).
renal function. Although amphotericin B is 400 times more effective Subcutaneous injection is preferred to intramuscular or intravenous than meglumine antimonate against Leishmania spp. its use is administration because of higher bioavailability (43) and a longer limited to cases resistant to meglumine antimoniate because of its half-life (42, 44). Meglumine antimonate, since it is readily excreted toxic potential and difficult administration. Recently a new protocol through the kidneys, does not significantly accumulate and has a has been successfully used by Lamothe to treat 39 cases (48).
very low toxicity. Side effects in the dog are painful local swellings at Intravenous injections (over 5–30 seconds) at a dosage of the site of injection, gastrointestinal problems (44), anorexia, 0.5–0.8 mg/kg are given twice weekly until a total dosage of 6–16 mg/kg is reached. Creatinine is measured weekly during this The initial course of treatment is 50 mg/kg every 12 hours for period. Drug administration is interrupted for two weeks if creatinine 20 days. This is repeated if no obvious improvement is observed. If, values become significantly (> 20%) elevated. With this protocol the after 40 days of treatment, no response is obtained, the Leishmania investigator obtained up to a 90% clinical cure rate, with only 10% strain is considered resistant and other therapeutic options must be chosen. Resistant strains have been repeatedly described, probably Recently, the efficacy and toxicity of a liposome-encapsulated due to inappropriate use of the drug by veterinarians or medical amphotericin B have been evaluated in dogs (49). This formulation is much less nephrotoxic, as less than 1% is excreted through the The use of meglumine antimonate does not prevent recurrences, kidneys, and seems to be effective, although frequent recurrences which take place in about 75% of cases after 6–8 months (41, 44).
have been observed. The major problem with this formulation of the Combination with allopurinol increases efficacy and decreases recurrence rate. Recent protocols (20, 36) advocate the use ofmeglumine antimonate (100 mg/kg every day) until the remission of Aminosidine
clinical signs in combination with allopurinol (10 mg/kg every Aminosidine is an aminoglycosidic antibiotic, derived from 8 hours or 20 mg/kg every 12 hours) for 9–12 months. The dogs are Streptomyces chrestomyceticus, with antimicrobial action against a monitored with serum protein electrophoresis and if a recurrence is wide range of microorganisms. It acts by inhibiting normal ribosomal suspected then meglumine antimoniate is administered again. If the function and causes abnormal protein production. It is administered disease does not recur within the first year then allopurinol is parenterally (IM or SC), as it is not absorbed by mouth, at a dose of withdrawn and the dog is monitored every 3–6 months for the rest of 5–10 mg/kg twice daily. As with every other aminoglycoside, aminosidine can be nephro- and ototoxic and should be given only to Liposome-encapsulated meglumine antimonate may be dogs with adequate renal function. Some studies have observed that commercially available in the future. This formulation has the it gives better results in combination with meglumine antimoniate advantage of obtaining higher serum concentrations, with decreased than when the two products are used alone (50). renal excretion and lower toxicity. Furthermore, liposomes arephagocytosed by macrophages and can exert their action in the Immunomodulation
cytoplasm and lysosome system where the parasites are located (46). Prednisolone may be used in dogs with renal insufficiency, if the use of meglumine antimonate is contraindicated. A dose of 1 mg/kg of prednisolone is given daily, with allopurinol and appropriate supportive therapy until renal values (plasma creatinine and urea) REFERENCES
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and two negative PCR results performed six months apart (33).
d’une enquête sur la leishmaniose canine effectuée pendant une courte
période chez les vétérinaires praticiens des Alpes-Maritimes. Pratique
Médical Chirurgienne des Animaux de Compagnie 1995; 30: 199–201.
PROGNOSIS
8. Fisas, R. Estudio sobre la estructura y dinamica del foco de
The aim of therapy is to eliminate the parasite and definitively leishmaniasis del Priorat. Doctoral Thesis, University of Barcelona, cure the dog. Unfortunately, this is the exception rather than the rule, as recurrence rates are very high. It has been stated that 9. Bravo, L., Frank, L. A., Brenneman, K. A. Canine leishmaniasis in the
affected dogs have a 75% probability of surviving at least four years if United States. The Compendium on Continuing Education 1993; 15:
they are given a course of 21–42 days of meglumine antimoniate and subsequent treatments at every recurrence (2). Dogs having a 10. Pirmez, C., Coutinho, S. G., Marzochi, M. C. A., Nunes, M. P.,
compromised renal function have the worst prognosis. A recent Grimaldi, G. Canine American cutaneous leishmaniasis: A clinical and study reported that dogs can be maintained in clinical remission for immunological study in dogs naturally infected with Leishmania years with long-term intermittent administration of allopurinol (51).
braziliensis in an endemic area of Rio de Janeiro, Brazil. American In the USA, where sporadic outbreaks of the disease have been Journal of Tropical Medicine and Hygiene 1988; 38: 52–58.
described, pentavalent antimonial compounds are not readily 11. Morsy, T. A., Schnur, L. F., Feinsod, F. M. et al. Natural infections of
available and are not registered for use in dogs. Euthanasia of Leishmania tropica major in domestic dogs from Alexandria, Egypt.
infected animals is often performed in order to prevent the American Journal of Tropical Medicine and Hygiene 1987; 37: 49–52.
transmission of the disease (which is potentially hazardous to 12. Barnes, J. C., Stanley, O., Craig, T. M. Diffuse cutaneous
human beings). However, it has been determined that a dog’s leishmaniasis in a cat. Journal of the American Veterinary Medical infective potential correlates with the presence of clinical signs Association 1993; 202: 416–418.
(especially skin lesions), and treated animals in clinical remission 13. Slappendel, R. J. Canine Leishmaniasis. A review based on 95 cases
are not a source of infection (52). Thus euthanasia should be in the Netherlands. Veterinary Quarterly 1988; 10: 1–16.
14. Diaz-Espineira, M. M., Slappendel, R. J. A case of autochthonous
canine leishmaniasis in the Netherlands. Veterinary Quarterly 1997;
PREVENTION AND CONTROL
19: 69–71.
15. Saint-André Marchal, I., Marchal, T., Moore, P. F., Magnol, J. P.,
Prevention and control of canine and human leishmaniasis can Bourdoiseau, G. Infection of canine Langerhans cells and interdigitating be achieved by control of sandflies and by taking steps to avoid dendritic cells by Leishmania infantum in spontaneous canine exposure to them. In endemic areas dogs should not spend the night leishmaniasis. Revue de Médecine Vétérinaire 1997; 148: 29–36.
outdoors and fine mesh nets should be applied to the windows. A 16. Fondevila, D., Vilafranca, M., Ferrer, L. Epidermal
recent study demonstrated that the application of a repellent immunocompetence in canine leishmaniasis. Veterinary Immunology deltamethrin collar to dogs can protect them from sandflies’ bites and Immunopathology 1997; 56: 319–327.
and prevent Leishmania infection (53).
17. Pinelli, E., Killink-Kendrick, R., Wagenaar, J. et al. Cellular and
The elimination of all clinically affected dogs has not improved humoral immune response in dogs experimentally and naturally infected the human infection rate where it has been imposed (54). However, with Leishmania infantum. Infection and Immunity 1994; 62:
treatment of all seropositive (symptomatic and asymptomatic dogs) has significantly decreased the prevalence of new infection cases in 18. Bourdoiseau, G., Bonnefont, C., Hoareau, E. et al. Specific IgG1 and
endemic areas (4). In the future, new prophylactic tools, such as IgG2 antibody and lymphocyte subset levels in naturally Leishmania infantum-infected treated and untreated dogs. Journal of Veterinary
Immunology and Immunopathology 1997; 59: 21–30.
Acknowledgment
19. Ferrer, L. Leishmaniasis. In: Kirk, R. W., Bonagura, J. D. (eds).
I would like to thank Dr Pedro Ginel of the Veterinary Faculty of Current Veterinary Therapy XI, Philadelphia: Saunders, 1992: the University of Cordoba, Spain, for critically reviewing the 20. Denerolle, P. Leishmaniose canine: difficulté du diagnostic et du
traitement. Pratique Médicale et Chirurgienne des Animaux de
T H E W O R L D ’ S L E A D I N G A U T H O R I T Y O N P E T C A R E A N D N U T R I T I O N
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