Leishmaniasis: a re-emerging zoonosis

Review

Leishmaniasis: a re-emerging zoonosis

Rosanna Marsella, DVM, DipACVD, and Rafael Ruiz de Gopegui, DVM, PhD

From the Department of Small Animal Clinical Sciences, Virginia

Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia,

and Department of Pathology and Animal Production, Veterinary Faculty,

Autonomous University of Barcelona, 08193 Bellaterra (Barcelona),

Spain

CorrespondenceRosanna Marsella, DVM, DipACVD, Department of Small Animal Clinical

Sciences, PO Box 100126, College of Veterinary Medicine, University of

Florida, Gainesville, FL 32610

Introduction

Leishmaniases are a group of infections caused by protozoa

of the genus Leishmania. With some exceptions, leishmani

ases are zoonotic diseases with transmission between sand

fly vectors and mammalian reservoirs in sylva tic or peri

domestic cycles. I Leishmaniases occur in more than 80

countries, and it is estimated that more than 15 million

people are infected, with more than 400,000 new human

cases every year. 2 Estimates are not accurate, however, as

leishmaniasis is a reportable disease in only 30 countries,

and a large number of infections are asymptomatic or

"subclinical." Human visceral leishmaniasis is still endemic

in the Mediterranean basin, and epidemics of the classical

visceral leishmaniasis are ongoing in India, Brazil, Sudan,

South America, North Africa, and central Africa. New

clinical presentations have been reported in American

military veterans acquired during Operation Desert Storm)

The emergence of leishmaniasis as an opportunistic infec

tion in people infected with human immunodeficiency virus

(HIV) has been reported in southern Europe, and it is

possible that leishmaniaI parasites of lower mammals could

also produce disease in humans afflicted with acquiredimmunodeficiency syndrome (AIDS).4

In the USA, imported leishmaniasis is occasionally dia

gnosed. Recently, an enzootic transmission cycle involvingLeishmania mexicana in Texas has been described, indicat

ing that cutaneous leishmaniasis may be more commonthan previously thoughr.! The purpose of this article is

to review, in a comparative manner, the host-parasite

interactions, pathogenesis, clinical signs, and therapy of

leishmaniasis, and to discuss the role of animal reservoirsin human disease.

© 1998 Blackwell Science Ltd

Classification of the agent

Leishmania spp. are intracellular protozoans belongingto the family Trypanosomatidae, order Kinetoplastida.Members of this genus infect primarily mammals, although10 species have been found in lizards in the Old World. Inthe last two decades, the classification of Leishmaniaspp. has been changed following the development of newtechniques.f One of the most useful classification methodsis based on the location of enzymatically active proteins(isoenzymes) via electrophoresis. Zymodemes are definedas groups of Leishmania organisms that share the sameelectrophoretic isoenzyme migration patterns.! The isoenzyme pattern obtained from patient isolates is comparedwith reference strains.

Morphology of l.eishmania parasites

Leishmania is heteroxenus and completes its life cycle usingtwo hosts. It is characterized by three different morphologictypes: amastigote, promastigote, and paramastigote. Theamastigote is found in the cells of the vertebrate hosts, andthe promastigote and paramastigote in the intestine of thesand fly and in culture.

The amastigote stage (2.5-5.0 x I.5-2.0 um) is usuallyfound within' macrophages and other cells of the reticuloendothelial system of the vertebrate host. A special mitochondrial structure containing deoxyribonucleic acid(DNA), called a kinetoplast, is present adjacent to thenucleus. A flagellum is not present (Figs 4-7).

Promastigotes are the form most commonly found in theinvertebrate vector. They are characterized by a spindleshape (14-20 X I.5-3.5 um) and a flagellum in theanterior part. 801

International Journal of Dermatology 1998,37,801-814

802 Review Leishmaniasis

Figure 1 Attachment between amastigotes and macrophageand interaction between T cells and parasite

Figure 2 Granulomatous lesion in the nasal region of a 7year-old crossbred female dog. The lesion appeared somedays after a cat scratch

Figure 3 Same case as in Fig. 2, I month after therapy usingN-methyl glucosamine 100 mg/kg/day s.c. and allopurinol20 mg/kg p.o. b.i.d.

International Journal of Dermatology 1998,37, 801-814

Marsella and Ruiz de Gopegui

Paramastigotes are also found in the invertebrate vector.This is a transitional stage between the previous twomorphologic types.

The vector

Numerous phlebotomine sand flies have been identified asvectors for the transmission of Leishmania (Table I). Theincrimination of a particular sand fly as vector is difficultas the presence of Leishmania stages in the gut doesnot necessarily mean that the insect is able to transmitthe disease."

The taxonomy is described below.Phyllum: ArthropodaClass: InsectaOrder: DipteraSuborder: NematoceraFamily: PsychodidaeSubfamily: PhlebotominaeFive genera comprising over 600 species that are distributedthroughout the tropics, subtropics, including rain forests,deserts, and highlands:Sergentomyia spp.Phlebotomus spp.Lutzomya spp.Brumptomyia spp.Warileya spp.

Sand flies are nocturnal insects that feed on mammals,birds, and reptiles according to the particular species. Onlythe female is hematophagous (blood-sucking) and a bloodmeal is required to lay eggs. The bite is usually painful andcauses a papular reaction that may persist for weeks. Sandflies are more common during warm months. Their flightrange is very limited (estimated to be 250 m). Sand fliespass though ordinary mesh screens due to their small size(2-5 mm). Under favorable conditions, the life cycle canbe completed in as little as 41-58 days. The life stagesinclude eggs, larvae, pupae, and adults. Females lay around100 eggs on the ground that hatch in 1-2 weeks. Larvaerequire a constant temperature, complete darkness, andorganic material to mature.

Life cycle of Leishmania spp.

The cycle starts when a sand fly takes a blood meal on aninfected vertebrate, ingesting amastigotes present in thedermis. Transformation from amastigote to promastigoteoccurs within 24-28 h. Parasites may either be free in theintestinal lumen of the sand fly or attached to the wallsby hemidesmosomes. Localization of the parasite in theintestine varies according to the particular species of vectorand the strain of Leishmania. This feature has been usedin the past as a criterion of classification of Leishmania spp.?



Figure 4 Leishmania infantumamastigotes in a fine needleaspirate from nodule shown inFig. 2. Dot-ELISA was negative.Diff-Quik stain, X 1000

magnification

Figure 5 Leishmania infantumamastigotes in a fine needleaspirate of lymph node. Diff-Quikstain, X 1000 magnification

After replication in the intestine, promastigotes migrate tothe esophagus and pharynx.

Following a sand fly bite, between 10 and 200 promastigotes present within the proboscis are regurgitated andpenetrate the dermis. Sand fly saliva plays a role in establishing the infection by reducing nitric oxide (NO) production by activated macrophages.f In heavily infected sandflies, the proboscis is congested with parasites, makingfeeding difficult and leading to repeated bites and multipleinoculations." Promastigotes do not actively migratetowards macrophages; they remain in the intercellularspace and activate complement by an alternative pathwaytriggering the accumulation of neutrophils and macro-


Leishmaniasis Review 803

phages. Many promastigotes are thought to be destroyedby polymorphonuclear leukocytes and a few transforminto arnastigotes.? Adhesion between the parasite andmacrophages is a fundamental step for invasion of the hostcell. Numerous receptors have been identified on the surfaceof Leishmania, among which glycoprotein 63 (gp63) andlipophosphoglycan (LPG) are the most important. Bothserum-dependent and serum-independent mechanisms ofadhesion occur, and complement receptors (complementreceptors I and 3) are used by the parasite to bind to

macrophages."? Once adhesion has occurred, Leishmaniaparasites are engulfed and enter the phagolysosome. Leishmania spp. have developed several mechanisms to resist

International Journal of Dermatology 1998,37, 801-814


the digestive and antimicrobial activity of the phagocyticcell (Table 2). Amastigotes are more resistant than promastigotes to cytokine-induced, oxygen-dependent antimicrobialmechanisms, reflecting an adaptation to intracellulargrowth. II Amastigotes multiply by binary fission insidemacrophages, leading to their rupture. 10

Epidemiology of the disease and reservoirhosts

With the notable exception of L. tropica and L. donovani,leishmaniases are zoonotic diseases. In most cases, morethan one mammalian species is found to be infected

International Journal of Dermatology 1998, 37, 801-814


Figure 6 Leishmania infantumamastigotes in the spleen of a5-year-old male intact MiniatureSchnautzer. The dog had severerenal failure and was subjected toeuthanasia due to the poorprognosis. Diff-Quik stain, X IOOOmagnification

Figure 7 Leishmania infantumamastigotes in the bone marrowfine needle aspirate of a I -year-oldmale intact Boxer. Dog wasclinically normal, but urinalysisrevealed proteinuria and a protein!creatinine ratio over normal limits.Diff-Quik stain, X IOOOmagnification

with a given species of Leishmania (Table I), making theidentification of a specific reservoir host difficult. In theMediterranean basin, infection is mainly caused by Leishmania infantum. Dogs have long been recognized as thereservoir host. The prevalence of infection is much higherin dogs (20-40%) than in humans (I-2%), and the diseaseis only sporadically reported in humans, even in areasendemic for canine leishmaniasis. The evaluation of theintradermal reactivity to the leishmanial allergen (leishmanin) in humans living in endemic areas showed that theprevalence of positive reactions increased with age, reaching43% in individuals between 45 and 55 years of age,suggesting that humans are frequently exposed to parasites,



Figure 8 A y-year-old male intact Great Dane with advancedleishmaniasis and concurrent babesiosis. Terminal cachexiaand marked abdominal distension due to hepatomegaly andabdominal effusion are evident

but that they develop resistance. 12,13 While the role ofthe canine population as a reservoir for human visceralleishmaniasis (L. infantum) in the Mediterranean basin hasbeen established, a reservoir has not been identified forstrains of L. infantum that cause cutaneous leishmaniasisin humans. These strains have so far been isolated onlyfrom humans.

In the New World, numerous wild and domestic animals,including dogs, cats, horses, and donkeys, may serve asreservoir hosts, allowing the transmission of infection insylvatic and domestic cycles. Humans are considered to beaccidental hosts developing both cutaneous and mucosallesions (Table I). Leishmaniasis has also been reported inthe USA. Cases have been described in humans, dogs(Oklahoma, Ohio, Florida, and Texas), and in one cat,leading to the conclusion that the disease is more commonthan originally thought. I 4- 16 Cutaneous leishmaniasis(L. mexicana) is endemic in Texas, and 20 new cases inhumans were described in this state between 1980 and1989.5 The distribution of cases followed the distributionof wood rats (Neotoma micropus) , suggesting that theseanimals are the reservoir hosts. The annual prevalence ofLeishmania mexicana in wood rats using the polymerasechain reaction varies from 5.6 to 27%.5 Lutzomya anthophora, a sand fly associated with wood rat burrows, wasinitially thought to be the vector. Alternatively, Lutzomyadiabolica, an avid human feeder that has also been foundin association with wood rats, may serve as a vector.

Immunology

Susceptibility to the disease depends on the T-cell andmacrophage response. The murine model of infection withLeishmania major suggests that, of all the T-cell subpopula-



tions, T-helper (Th) cells play a fundamental role in theoutcome of leishmaniasis. Expansion of the Th1 subsetwith the production of interleukin 2 (IL-2) and gammainterferon (y-IFN) leads to the resolution of infection inresistant mice, while Th2 proliferation and IL-4 productionleads to the progression of the disease in susceptibleanimals. Great effort has been made to investigate theregulatory cells and molecules involved in the differentiation of T cells from Tho precursors to the Th1 and Th2subsets, but the exact mechanism is still largely unknown.Factors that may play a role include antigen-presentingcells, antigenic load, type and amount of cytokines presentat the time of inoculation of parasites, and the specificleishmanial antigen.t-"?

In dogs, susceptibility to the disease is due to a lack ofa specific Tcell response (assayed by both intradermal

skin test and proliferation assays) and to a notable, butineffective, humoral response, as previously demonstratedfor mice, guinea pigs, and humans. I 8, I 9 Suggestive evidence

of suppressed cell-mediated immunity also comes from the

observation of high numbers of Demodex mites in dogswith leishrnaniasis.t? Demodex mites are present in low

numbers in the skin of normal individuals, but if immunosuppression occurs they increase in number.

Leishmaniasis and immunosuppression

Since the mid-r oSos, there has been a dramatic increase inthe number of cases of leishmaniasis in HIV-infectedpatients. A synergistic relationship between leishmaniasisand AIDS exists. Specifically, it is now known that promastigotes trigger tumor necrosis factor-alpha (TNF-a) synthesis

(89% of patients with visceral leishmaniasis have elevatedlevels of circulating TNF-a),21 and this cytokine has theability to upregulate HIV virus replication.'? This notion

is supported by data indicating that 3-7% of HIV-positiveindividuals in southern Europe develop visceral leishmaniasis. In these areas, more than 50% of visceral leishmaniasisin adults is now related to HIV infection."

HIV-positive individuals are not only more susceptibleto leishmaniasis, but also develop visceral disease evenafter infection with dermotropic strains of Leishmania,suggesting that tropism of the parasite is largely influencedby the immune status of the host. Progression from seropositivity to AIDS and visceralization of leishmaniasis involvea relative switch from a Th1 to a Th2 response, andthis explains why even seropositive asymptomatic HIVindividuals may develop a visceral dissemination of dermotropic strains. Recent data show that visceralization occurswith the same frequency in both asymptomatic seropositiveindividuals and in AIDS cases.P



Clinical signs: a comparative approach

The concept that each species of Leishmania causes adistinct clinical syndrome is no longer valid. Infection withLeishmania can either lead to clinically silent disease or toa spectrum of clinical signs depending on the immunologicstatus, genetic background and nutritional status of thehost, the number of parasites and their virulence factors,the site of inoculation, the composition of sand fly saliva,and other variables that have yet to be elucidated. I Sandfly saliva containing vasodilators favors the infection ofcirculating monocytes and visceralization, whereas salivathat triggers minimal vasodilation will lead to dermalinfection only.'

Leishmaniasis in humans has been traditionally classifiedas cutaneous, visceral, and mucocutaneous (Table 1).22

I Cutaneous form. New World: L. braziliensis, L. mexicana; Old World: L. major, L. tropica, L. aethiopica,L. infantum.

2 Visceral form. L. donovani, L. infantum.3 Mucocutaneous form. L. braziliensis, L. aethiopica.In dogs, manifestations of the disease are quite variable.v'After infection, various outcomes are possible (Table 3).I Clinically silent infection.2 Cutaneous manifestations.3 Non-specific signs.4 Multisystemic disease.

Clinical pathologic findings

Hematologic and serum biochemical data vary with theclinical presentation of the disease (Table 4).24


Marsella and Rui: de Gopegw

Figure 9 Ehrlichi aplatys morula ina platelet. Buffy coat smear stainedwith Diff-Quik, x 5000

magnification

Pathologic findings

Leishmania spp. amastigotes have been described withinmacrophages in spleen, lymph nodes, tonsils, bone marrow,liver, urinary bladder, intestinal lamina propria, lung,choroid plexus, cerebrospinal fluid, urine, and semen, andalso in phagocytic cell types other than macrophages, suchas monocytes, neutrophils, eosinophils, endothelial cells,and fibroblasts.s! Dogs with an anergic immune systemdevelop generalized distribution of the parasite and achronic and profuse cellular infiltration with macrophages,lymphocytes, and plasma cells. The cells form either adiffuse infiltrate or poorly organized microgranulomata.Animals that are either resistant to the infection or asymptomatic carriers tend to develop highly organized epithelioidgranulomata, evidence of an effective cell-mediatedimmunity. 26

Diagnosis (Table 5)

Parasitologic diagnosis

Amastigotes can be demonstrated in Giemsa-stained smearsfrom tissue aspirates (Figs 4-7). The kinetoplast is usefulin differentiating Leishmania from intracellular pathogenswith similar morphology. Definitive diagnosis has beentraditionally based on cytologic or histopathologic observation of amastigotes. Immunoperoxidase staining is moresensitive for the identification of amastigotes in infectedtissues."? Recently, the application of polymerase chainreaction (PCR) technology has allowed the identificationof Leishmania spp. to a higher degree of sensitivity. Polymerase chain reaction using primers from the LeishmaniarRNA gene allows the identification of parasites from a


Marsel/a and Ruiz de Gopegui Leishmaniasis Review 807

Table 1 Synopsis of the most common types of Leishmania, their geographic distribution, reservoir hosts and type of diseasecaused in humans

Agent Vector Geography Animal reservoir Humans

L. braziliensis complex Lutzomya longipalpis Argentina Forest rodents (Proechimys Mucocutaneous form.

L. braziliensis braziliensis Phlebotomus yucumensis, Bolivia guyanensis) and marsupialia Skin lesions including papules,

L. braziliensis guyanensis P. I/anosmartinsi (Oidelphi marsupialis) have been nodules, and ulcers. Mucosal

L. braziliensis panamensis Lu. umbratilis, Brazil identified as reservoirs, while lesions in the mouth, nose,

Lu. flaviscutel/ata humans are accidental hosts. In pharynx, and larynx leading to

Lu. spinicrassa Colombia Brazil, the main reservoir host in destruction of cartilage and

Lu. trapidoi Boyaca, Caldas the sylvatic cycle has not been disfigurement (espundia) were

Lu. migonei, Lu. gomezi Venezuela identified, but domestic dogs very common in the past (>80%).

(Canis familiaris), horses (Equus At the present time, this form

cabal/us), donkeys, and rats may occurs in less than 5% of cases,

serve as reservoir hosts in the and cutaneous lesions are more

urban cycle. Sloths (Chloepus common. Visceral involvement is

didactylus) , anteaters, and not usually seen, but death may

opossums are the main reservoirs occur due to secondary bacterial

for L. guyanensis. Sloths infections

(Chloepus hoffmannii and

Bradypus infuscatus) are the

major reservoir for L. panamensis

L. mexicana complex Lutzomya anthopora, USA (Texas), Various rodents have been Mucocutaneous form.

L. mexicana amazonensis Lu. diabolica, Bolivia, Brazil, identified as reservoir. Humans Small erythematous papules

L. mexicana pifanoi Riphicephalus sanguineus? Colombia, are accidental hosts. Wood rat occur at the site of the insect bite

L. mexicana aristedesi (Texas), Lutzomya Ecuador, (Neotoma micropus) is the and slowly develop into an

L. mexicana garnhami olmeca olmeca (Belize) Guatemala, reservoir of infection in Texas ulcerated nodule. Eventually, the

L. mexicana venezuelensis Mexico, Peru, lesions heal, leaving a depressed

Venezuela, Belize scar (ears are involved in 40-55%

of cases as they are common

areas of Lutzomya bites). In

Texas, cutaneous nodules are the

most common clinical

presentation. In Belize, this

infection is limited to people

entering the forests

L. enrietli Lutzomya gasparviannai Bahia, Espirito Domestic guinea pigs (Cavia , Human infection not reported

Santo porcel/us) develop ulcers in the

skin and may act as a reservoir.

No visceralization occurs

L. hertigi P. claustrei, P. davisi, Porcupines may act as reservoir. No human infection ever reported

P. chagasi, P. maripaensis No canine infection has ever been

reported

L. chagasi (Cunha and Lutzomya longipalpis Bolivia, Brazil, Foxes are the reservoir hosts in Visceral form.Chagas) Colombia, EI the sylvatic cycle, while dogs and Incubation may last for weeks and

Salvador, opossums (Oidelphi marsupialis) months. Subacute fever,

Honduras, are the hosts in the peridomestic splenomegaly, pancytopenia, and

Mexico, cycle wasting are common clinical

Venezuela presentations

L. peruviana Lutzomya noguchii, Peru, Bolivia Domestic dog (Canis familiaris) is Two different clinical forms are

Lu. verrucarum, the natural host recognized: the "cutaneous

Lu. peruensis Andean form" called uta and the

"Amazonian jungle form" with

mucous membrane involvement

resembling espundia

© 1998 Blackwell Science Ltd International Journal of Dermatology 1998,37,801-814


Table 1 Cant.


Agent

L. donovani

L. infantum

L. tropica

Vector

P. ariasi

p. longicuspis

P. major

P. orientalis

P. perniciosus

P. smtmovi, P. longiductus

P. tobbi

P. martini

P. argentipes

P. chinensis

P. pemiciosus, P. longicuspis.

P. chinensis, P. mongolensis,

P. caucasicus

P. perfiliewi. P. pappatasi,

P. serqent), P. longicuspis

Geography

France

Yemen. Ethiopia,

SomaliaSoutheast Asia

SudanItaly, North Africa

Russia

Cyprus

Kenya

India. Afghanistan

China

Albania. Algeria.

China. Egypt.

France, Greece,

Israel, Italy,

Pakistan,

Portugal, Spain,

Turkey,

Oklahoma (USA)

Afghanistan,

Greece. Kuwait,

Turkey, Yemen

Animal reservoir

Visceral leishmaniasis caused by

L. donovani in India is not thought

to have an animal reservoir, and

parasites can be isolated from

normal-appearing skin of patients

up to 4 years after treatment

Dogs are more commonly

affected (20-40%) than humans

(1-2%) in endemic areas. Other

hosts are jackal, fox, wolf,

porcupine, fennec fox. and rat.

The common rat can also be a

reservoir. In dogs, clinical signs

may range from inapparent to

multisystemic disease. Diagnosed

in a few cases in the USA in dogs

imported from Greece. Spain, and

Portugal

It is thought not to have an animal

reservoir and to be an

anthroponosis. Rats may act as a

reservoir. Isolation of parasites in

the skin of some dogs is raising

the possibility that dogs may be a

reservoir in some areas.

Humans

Visceral form in humans (kala

azar, black fever, dum-dum fever).

After several months of

incubation. irregular fever and

liver and spleen hypertrophy arenoted. Mortality is 75-95% if

untreated. Post-kala-azar dermal

leishmaniasis can occur (up to

20% of cases) after treatment of

the visceral form. and may serve

as a reservoir for infection.

Macules, papules, nodules. and

plaques are numerous

Viscerocutaneous form.It causes Mediterranean or

infantile kala-azar (90% of

affected people are children less

than 5 years old). Cutaneous

lesions are usually more

inflammatory and more likely to

be solitary than those caused by

L. major

Cutaneous form.

Oriental sore (dry). Aleppo button,

Jericho boil, Pendinsk ulcer.

Ulcers and sores in exposed parts

of the body leading to permanent

scars. Rarely fatal. Leishmania

recidivans has been associated

with L. tropica. Typical lesions are

red plaques with spreading

borders and healing centers

L. major P. duboscqi.

P. pappatasi.

P. salehi,

P. caucasicus

Senegal. Egypt, Natural hosts are the desert

Southeast Asia. rodents such as the great gerbil

India, Afghanistan. (Rhombomys opimus). gerbil.

Israel, Kuwait, suslik, sand rat. hedgehog, and

Pakistan. Yemen mustelid carnivores. Infection in

dogs has never been reported

Cutaneous form (wet form of the

oriental sore). It starts as a small

papule, which appears

immediately after the insect bite

or after 2-4 weeks. Papule

enlarges in size. and becomescrusted in the center. When crust

is removed. an ulcer with

ulcerated borders is found.

Subcutaneous nodules develop

along the iymphatics. After 6-12

months, the lesion heals leaving a

depressed scar. No involvement

of mucous membranes. Lymph

nodes are often involved. In some

cases, lesions are active for more

than 24 months (non-healing

chronic cutaneous leishmaniasis)

International Journal of Dermatology 1998,37,801-814 © 1998 Blackwell Science Ltd


Table 1 Cont.


Agent

L. aethiopica

Vector Geography

Ethiopia, Kenya.

Sudan

Animal reservoir Humans

Cutaneous form.Similar to L. major. In some

cases. it causes widespread skin

lesions that resemble lepromatousleprosy

Table 2 Adhesion and escape mechanisms of Leishmania spp.

Leishmania

Lipophosphoglycan

Glycoprotein 63

Superoxide dismutase

Acid phosphatase

Mechanism of interaction with the host

Binds lectin-like binding sites on CR3 and mediates adhesion to macrophages

Inhibits insertion of C5b-9 complex in the membrane preventing lysis

Impairs generation of respiratory burst through inhibition of protein kinase C

Inhibition of lysosomal ~ galactosidase

Oxygen radical scavenger

Protease capable of degrading lysosomal enzymes

Degradation of H20 2

Inhibition of oxidative burst

variety of samples, including human and canine bonemarrow, lymph nodes, skin biopsies, and heparinizedwhole blood.r"

Immunologic diagnosis

This involves the detection of antibodies against Leishmaniaparasites or a specific cell-mediated immune response. Acell-mediated response can be detected by measuring thecytokine production or proliferative response of peripherallymphocytes to Leishmania antigens or delayed hypersensitivity to intradermal injection of leishmanial antigens. Currently, a Leishmania antigen is not approved by the Foodand Drug Administration for intradermal skin testing inthe USA. The identification of anti-leishmania antibodiesin serum has been attempted by several methods; however,cross-reaction between different species of the genus Leishmania with Trypanosoma cruzi and Babesia spp. is possible.Serologic testing should be attempted if visceral leishmaniasis is suspected and the parasitologic diagnosis is negative.A positive serologic titer, however, does not necessarilyimply that clinical leishmaniasis will develop. Serology maybe negative in patients with visceral leishmaniasis secondaryto AIDS. In those cases, the detection of parasites by culture,microscopy or polymerase chain reaction is necessary toachieve a diagnosis of visceral leishmaniasis. 29 In localizedcutaneous leishmaniasis, serologic diagnosis is unreliablein both dogs and people and direct diagnosis is required.t?


The following tests have been developed.I Indirect immunofluorescent antibody test (IFAT) shows

a high specificity and sensitivityY2 Enzyme-linked immunosorbent assay (ELISA) is rou

tinely used in people with visceral disease'> and in dogs.A modification of this method, dot-ELISA, constitutes asimpler immunoassay.t"

3 Immunoblot analysis (Western blot) has a high sensitivityfor the detection of antibodies in human visceral leishmaniasis and canine Ieishmaniasis.H

4 Direct agglutination test (DAT) has a similar specificity toIFAT, but a lower sensitivity in both dogs and humans.U

5 Indirect immunoperoxidase assay (IPA) is more sensitiveand specific than IFAT for the diagnosis of visceralleishmaniasis in people.

6 Recombinant Leishmania infantum proteins (rLIP2a andrLIP2b) have been studied as potential tools for thediagnosis of human mucocutaneous and visceral leishmaniasis. Leishmania P2 acidic ribosomal proteins arerecognized by the sera of some patients with leishmaniasis, avoiding cross-reactivity with sera from patientswith systemic lupus erythematosus and Chagas' disease.t"

Therapy

There is no universally effective therapy for leishmaniasis.Canine leishmaniasis usually has a poorer prognosis than

International Journal of Dermatoiogy 1998,37,801-814


Table 3 Clinical signs commonly reported in dogs and in humans with leishmaniasis

Humans


Dogs

Cutaneous

Systemic

Localized

Disseminated

Mucosal

L. recidivans

Post-kala-azar dermal

leishmaniasis

Mononuclear phagocyte

system

Gastrointestinal

Respiratory

Ocular

Others

Concomitant infections

Single papule evolving into a noduleand then into an ulcer,

Non-ulcerative soft nodules,

resembling leprosy

Occurs only in a small percentage

after the occurrence of

localized cutaneous disease

(L. braziliensis). Nodules in

nasal or pharyngeal mucosa

Caused by L. tropica. Slowly healing

ulcer

Caused by L. donovani (India),

usually after treatment of the

visceral disease. Macules, nodules,

and plaques

Hepatosplenomegaly,

lymphadenopathy

Diarrhea, vomiting, cachexia. Gastric

ulcers, esophageal ulcers,

and rectal masses (HIV patients)

Pleural effusion (HIV patients)

Fever, abdominal distension,

glomerulonephritis, and

renal amyloidosis

HIV, Plasmodium spp.,

M. tuberculosis, secondary

infections

Scaling, erosion, ulcers,

onychogryphosis, paronychia, cold

agglutinin disease (ear margin

necrosis). Nodules on mucous

membranes have also been

reported

Generalized lymphadenopathy

Diarrhea, melena, vomiting,

anorexia, weight loss, terminal

cachexia

Rhiniitis, epistaxis

Conjunctivitis, keratitis,

chorioretinitis, uveitis,

panophthalmitis

Asthenia, decreased activity,

glomerulonephritis, chronic active

hepatitis, polyarthritis, synovitis,

vasculitis

Rickettsia rickettsii, Ehrlichia canis,

E. platys, Babesia canis,

Demodex canis, Microsporum spp.

the human disease, and relapses are frequently observed.New alternative therapies are currently being investigated,including administration of cytokines, new compounds,and plant extracts (Table 6).37-41

Prophylaxis

The treatment of leishmaniasis in both humans and dogscan be unrewarding, emphasizing the need for additionalresearch and for prophylaxis. The prevention of leishmaniasis relies on a knowledge of the parasite and control ofthe vector. Complete eradication of mammalian reservoirhosts has been suggested and attempted, but is impractical

International Journal of Dermatology 1998, 37, 801-814

and, in the authors' opinion, would not eliminate the riskof leishmaniasis. It is probable that the eradication of thenatural host would result in the adaptation of the parasiteto different hosts, and the expansion of the species thatare currently using humans as reservoirs (L. donovani andserotypes of L. infantum). With regard to the role ofdogs in human leishmaniasis in the Mediterranean basin,euthanasia of seropositive and even affected dogs is notjustified as the prevalence of human infection in areasendemic for canine leishmaniasis is low and direct transmission of the disease from dogs to humans is only anecdotal.In addition, although HIV/Leishmania coinfection is clearlyan emerging problem, it has been shown that immunosup-



Table 4 Clinical pathologic abnormalities reported in humans and dogs with leishmaniasis


Hematology

Chemistry

Humans

Non-regenerative anemia, increased ferritin"

Thrombocytopenia, thrombopathia

Hypoalbuminemia, hyperglobulinemia

Azotemia, increased liver enzymes

Dogs

'Non-regenerative anemia" (normochromic,

normocytic), increased ferritin, leukopenia,

plasma cells in peripheral blood samples

Thrombocytopenia, thrombopathia

Hypoalbuminemia, hyperglobulinemia

Azotemia, increased liver enzymes

Hematuria, proteinuria

Positive antinuclear antibody and Coomb's tests

*Anemia due to chronic inflammation.

Table 5 Diagnostic methods reported for human and canine leishmaniasis

Method Species Advantages Disadvantages

Parasitologic

diagnosis

Immunologic

diagnosis"

Cytology (Giemsa,

Romanowsky &

Wright, Diff-Quik)

Histopathology.

Immunoperoxidase

Culture (Novy-MacNeal

Nicolle or in Schneider's

culture medium)

PCR

IFAT

ELISA, dot-ELISA

Immunoblot

OAT

IPA

Recombinant L. infantum

proteins

Humans, dog

Humans, dog

Humans, dog

Humans, dog

Humans, dog

Humans, dog

Humans, dog

Humans, dog

Humans

Humans

High specificity, cheap

High sensitivity,

immunoperoxidase staining

improves the detection of

amastigotes

Sensitive, optimal for in vitro

studies evaluating sensitivity of

parasites to various drugs

High sensitivity

High sensitivity and specificity

Sensitive. Dot-ELISA improves

availability

Sensitive

Specific

Sensitive and specific

High specific

Low sensitivity,

interpretation

Time, availability

Results take 3-10 days,

expensive

Availability

Availability, interpretation

requires fluorescence

microscope, and less

sensitive than ELISA

Less precise than IFAT,

cross-reactions with Babesia

spp. and Trypanosoma

cruzi, and availability

Less sensitive than IFAT

*Immunologic determinations are optimal for epidemiologic studies, but do not confirm clinical disease. Immunosuppressedpatients may require parasitologic diagnosis as immune response may not be detectable. Parasitologic diagnosis is required inall cases of cutaneous disease, even in immunocompetent individuals.

pression is not the only factor in the epidemiology ofLeishmania infection in HIV-positive individuals, and thata more important factor is the sharing of infected syringes.P

Control of the vector is a more reliable strategy due to


the fact that these insects spend their life cycle in a verylimited area (less than I km). Sand fly control can berestricted to inhabited areas only. The use of perrnethrintreated screens alone drastically reduced sand fly popula-


812 Review Leishmaniasis Marsella and Ruiz de Gopegui

Table 6 Therapeutic modalities used for the treatment of leishmaniasis in both humans and dogs

Group Compounds Administration Indications Mechanism of action Observations

Antimonials Meglumine Humans: 20-60 mgt New World Inhibits protozoa Contraindicated in

(pentavalent Sb antimoniate kg/day parenteral mucocutaneous carbohydrate and lipid pregnancy, cardiac,

compounds) Sodium (i.m.) leishmaniasis (L. metabolism hepatic, and renal

stilbogluconate Dogs: 100 mg/kg b.l.d, braziliensis) and disease

s.c. 15 days canine leishmaniasis

Antimicrobials Dapsone 200 mg/kg/day for 45 Old World cutaneous Exact mechanism is Hemolysis or

days leishmaniasis unknown. Thought to leukopenia may occur

decrease phospholipid

synthesis or to

interfere with folic acid

synthesis

Rifampicin (it can be 600-1200 mg/kg/day Old World cutaneous RNA-polymerase Contraindicated in

combined with leishmaniasis inhibitor pregnancy and liver

isoniazide) disease

Metronidazole 250 mg t.i.d. courses Old World cutaneous Cytotoxic effect on Contraindicated with

of 10 days/l0 days leishmaniasis parasite DNA ethanol. Efficacy

rest questioned

Trimethoprim- 160/800 mg b.i.d, 3-4 Old World cutaneous Folic acid metaboiism Efficacy questioned

sulfamethoxazole weeks leishmaniasis inhibitor

Paromoymycin Topically for 10 days, New World Interference with Combined with

plus antirnonials for 7 mucocutaneous protein synthesis antimonials for

days leishmaniases mucocutaneous

leishmaniasis

Aminosidine sulfate 16 mg/kg/day i.rn. Mucocutaneous Interference with

leishmaniasis protein synthesis

Xanthine oxidase Allopurinol 10-15 mg/kg b.Ld. New World Alters protein and Long-term

inhibitor mucocutaneous DNA synthesis of administration in

leishmaniasis and protozoa canine leishmaniasis,

canine leishmaniasis combined with initial

antimonial

administration

Antifungals Ketoconazole 200-400 mg/kg/day New World Ergosterol synthesis Side-effects include

mucocutaneous inhibitor anorexia, vomiting,

leishmaniasis (L. hepatitis, adrenal

mexicana) suppression, and

microsomal enzyme

suppression

Itraconazole 4 mg/kg/day (100-200 Old World cutaneous Ergosteroi synthesis Same side-effects as

mg/day) 6 weeks to 8 leishmaniansis inhibitor ketoconazole, but less

weeks hepatotoxic

Amphotericin B 0.5-1 mg/kg lipid New World Used in patients

complexes (liposomes) mucocutaneous unresponsive to

leishmaniasis and antimonials

visceral leishmaniasis

Physical Local heat 55°C for 5 min Old and New World Inhibition of Severe scarring may

cutaneous and amastigote replication occur

mucocutaneous

leishmaniasis

Cryotherapy End point is when an Old World cutaneous Severe scarring may

ice ball exceeding 2 leishmaniasis occur

mm over the margins

of the lesion is formed

International Journal of Dermatology 1998,37, 801-814 © 1998 Blackwell Science Ltd


Table 6 Cont.


Group

Cytokines

Compounds

Others

y-Interferon

Interleukin-12

Administration

Surgical excision,curettage, laser,electrodessication

Combined withconventional therapy

Combined withconventional therapy

Indications

Old World cutaneousleishmaniasis

Visceral leishmaniasis(experimental)

Visceral leishmaniasis

(experimental)

Mechanism of action Observations

Increases macrophage Experimentalnitric oxide production

Modulates T-cell Experimentalresponse (inhibits Th2cell IL-4 production)

tions in one preliminary study.O In addition, plants thatinhibit the development of Leishmania in sand flies andBacillus sphericus infection of Phelbotomus have beeninvestigated.v-t"

The development of a vaccine against leishmaniasis is along-term goal in both human and veterinary medicine.Protective immunity occurs in the majority of humanpatients with cutaneous leishmaniasis after the resolutionof the clinical signs, and this is the reason why someprimitive populations inoculated their children withinfected materials. I Immunization has been attempted onan experimental basis with killed parasites, parasite fractions, and genetically engineered organisms, including eithermodified Leishmania or Salmonella.ri At the present time,however, a vaccine is not commercially available.

Conclusions

Leishmaniasis remains a serious public health problem inmany regions of the world. Long-term goals to improvethe control of this disease include the development of avaccine and safer drugs that can be administered orallyand for a shorter period of time.

Drug names

Allopurinol, Zyloprim; aminosidine and paromomycin sulfate (not available in the USA); amphotericin B, Fungizone;dapsone, Dapsone Tablets; y-interferon, Actimmune; itraconazole, sporonox; ketoconazole, Nizoral; rifampicin,Rifadin; trimethoprim-sulfamethoxazole, Bactrim.

References

I Hommel M, Jaffe CL, Travi B, Milon G. Experimentalmodels for leishmaniasis and for testing anti-leishmanialvaccines. Ann Trop Med Parasitol 1995; 89: S55-S73.

2 Ashford RW, Desjeux P, DeRaadt P. Estimation ofpopulation at risk of infection and number of cases ofleishmaniasis. Parasitol Today 1992; 8: 1°4-1°5.


3 Magill A, Gragl M, Gasser J, et al. Visceral infectioncaused by Leishmania tropica in veterans of OperationDesert Storm. N Engl J Med 1993; 328: 1383-1385.

4 Gorgolas De M, Miles MA. Visceral leishmaniasis andAIDS. Nature 1994; 372: 33.

5 Kerr SF, McHugh CP, Dronen NO Jr. Leishmaniasis inTexas; prevalence and seasonal transmission ofLeishmania mexicana in Neotoma micropus. Am J TrapMed Hyg 1995; 53: 73-77·

6 Grimalidi G jr, Tesh RB, McMahon-Pratt D. A review ofthe geographic distribution and epidemiology ofleishmaniasis in the New World. Am J Trap Med Hyg

1989; 41: 687- 725.7 Pizzirani S. La Leishmaniosi Canina. Bologna, Italy:

Grasso Editor, 1989: 4-6.8 Hall LR, Titus RG. Sand fly vector saliva selectively

modulates macrophage functions that inhibit killing ofLeishmania major and nitric oxide production.J Immunol 1995; ISS: 3501-3506.

9 Magill A]. Epidemiology of the leishmaniases. DermatolClin 1995; 13: 505-523.

10 Tremblay M, Olivier M, Bernier R. Leishmania and thepathogenesis of HIV infection. Parasitol Today 1996;

12: 257-261.II Hall BF,Joiner KA. Strategies of obligate intracellular

parasites for evading host defenses. Parasitol Today1991; 12: A22-A27.

12 Bettini S, Gramiccia M, Gradoni L, et al. Leishmaniasisin Tuscany (Italy) VIII. Human population response toleishmanin in the focus of Monte Argentario (Grosseto)and epidemiological evaluation. Ann Parasitol HumComp 1983; 58: 539-547·

13 Bettini S, Gradoni L. Canine leishmaniasis in theMediterranean area and its implication for humanleishmaniasis. Insect Sci Appl 1986; 7: 241-245.

14 Swenson CL, Silverman J, Stromberg PC, et al. Visceralleishmaniasis in an English foxhound from an Ohioresearch colony. J Am Vet Med Assoc 1988; 193:1089-1°92.

15 Barnes JC, Stanley 0, Craig TM. Diffuse cutaneousleishmaniasis in a cat. J Am Vet Med Assoc 1993; 202:416-4 18.


814 Review Leishmaniasis Marsella and Ruiz de Gopegui

16 McHugh CP, Melby PC, LaFon SG. Leishmaniasis in leishmaniasis by indirect immunofluorescence, indirectTexas: epidemiology and clinical aspects of human cases. hemagglutination, and counter-immunoelectrophoresis.Am] Trop Med Hyg 1996; 55: 547-555. Am] Vet Res 1988; 49: 1409-I4II.

17 Locksley RM, Scott P. Helper T-cell subsets in mouse 32 Hommel M, Peters W, Ranque J, et al. The micro-ELISAleishmaniasis: induction, expansion and effector technique in serodiagnosis of visceral leishmaniasis. Annfunctions. Immunol Today 1991; 12: A58-A6I. Trop Med Parasitol 1978; 72: 213-218.

18 Martinez-Moreno A, Moreno T, Martinez-Moreno FJ, 33 Pappas MG, Hajkowski R, Hockmeyer WT. Dotet al. Humoral and cell-mediated immunity in natural enzyme-linked immunosorbent assay (Dot-ELISA):and experimental canine leishmaniasis. Vet Immunol a microtechnique for the rapid diagnosis of visceralImmunopath 1995; 48: 209-220. leishmaniasis. ] Immunol Methods 1983; 64: 205-214.

19 Liew FY, O'Donnel CA. Immunology of leishmaniasis. 34 Gari-Toussaint M, Lelievre A, Marty P, et al.Adv Parasitol 1993; 32: 161-259. Contribution of serological tests to the diagnosis of

20 Kennan CM, Hendricks LD, Lightner L, Johnson visceral leishmaniasis in patients infected with theAJ. Visceral leishmaniasis in the German Shepherd dog. human immunodeficiency virus. Trans R Soc Trop MedII. Pathology. Vet Pathology 1984; 21: 80-86. Hyg 1994; 88: 301-330.

21 Pisa P, Gennene M, Soder 0, et al. Serum tumor necrosis 35 Nigro L, Vinci C, Romano F, Russo R. Comparison offactor levels and disease dissemination in leprosy and the indirect immunofluorescent antibody test and theleishmaniasis. ] Infect Dis 1990; 161: 988-991. direct agglutination test for serodiagnosis of visceral

22 Fitzpatrick TB, Eisen AZ, Wolff K, et al. Dermatology in leishmaniasis in HIV-infected subjects. EurJ ClinGeneral Medicine, Volume II, 4th edn. New York: Microbiol Infect Dis 1996; 15: 832-835.McGraw-Hill, 1993: 277 2-2777. 36 Soto M, Requena JM, Quijada L, Alonso C. Specific

23 Kontos VJ, Koutinas AF. Old World canine serodiagnosis of human leishmaniasis with recombinantleishmaniasis. The Compendium 1993; 15: 949-959. Leishmania P2 acidic ribosomal proteins. Clin Diagn

24 Burin-Moreno MM, Madeira ED, Miler K, et al. Lab Immunol 1996; 3: 387-391.Hypergammaglobulinemia in Leishmania donouani 37 Ghanem BM, El-Shazly AM, Fawzy M, et al. Allopurinolinfected hamsters: possible association with a polyclonal in the treatment of zoonotic cutaneous leishmaniasis.activator of B cells and with suppression of T cell ] Egypt Soc Parasitol 1996; 26: 619-628.function. Immunology 1985; 59: 427-434. 38 Brajtburg J, Bolard J. Carrier effects on biological

25 Hervas-Rodriguez J, Mozos E, Mendez A, et al. activity of amphotericin B. Clin Microbiol Rev 1996;Leishmania infection of canine skin fibroblasts in vivo. 9: 512-531.

Vet Pathol 1996; 33: 469-473. 39 Murray HW. Current and future clinical applications of26 Oliveira GGS, Santoro F, Sagidurski M. The subclinical interferon-gamma in host antimicrobial defense.

form of experimental visceral leishmaniasis in dogs. Intensive Care Med 1996; 22: S456-S461.Mem Inst Oswalso Cruz 1993; 88: 243-248. 40 Chance ML. New developments in the chemotherapy of

27 Sells PG, Burton M. Identification of Leishmania leishmaniasis. Ann Trop Med Parasitol 1995; 89: 37-43.amastigotes and their antigens in formalin fixed tissue by 41 Berman JD. Treatment of New World cutaneous andimmunoperoxidase staining. Trans R Soc Trop Med Hyg mucosal leishmaniases. Clin Dermatol 199 6; 14:1981; 75: 461-468. 519-522.

28 Mathis A, Deplazes P. PCR and in vitro cultivation for 42 Alvar G, Gutierrez-Solar B, Pach6n I, et al. AIDS anddetection of Leishmania spp. in diagnostic samples from Leishmania infantum. Clin Dermatol 199 6; 14:humans and dogs. ] Clin Microbiol 1995; 33: 541-546.

II45-II49· 43 Basimike M, Mutinga MJ. Effects of permethrin-treared29 Millesimo M, Zucca M, Caramello P, Savoia D. screens on phlebotomine sand flies, with reference to

Evaluation of the immune response in visceral Phlebotomus martini. ] Med Entomol 1995; 32:leishmaniasis. Diag Microbiol Infect Dis 1996; 26: 7-11. 428-432.

3° Mengistu G, Akuffo H, Fehniger TE, et al. Comparison 44 Schlein Y, Jacobson R. Mortality of Leishmania major inof parasitological and immunological methods in the Phlebotomus papatasi caused by plant feeding of thediagnosis of leishmaniasis in Ethiopia. Trans R Soc Trop sand flies. Am] Trop Med Hyg 1994; 50: 20-25.Med Hyg 1992; 86: 154-157. 45 Modabber F. Vaccines against leishmaniasis. Ann Trop

31 Mancianti F, Meciani N. Specific serodiagnosis of canine Med Parasitol 1995; 89: 83-88.

International Journal of Dermatology 1998, 37, 801-814 © 1998 Blackwell Science Ltd

Leishmaniasis: a re-emerging zoonosis

Documents

Transcript of Leishmaniasis: a re-emerging zoonosis