Difference between revisions of "Leishmania"

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{{Taxobox
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|name              =''Leishmania spp.''
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|kingdom            =Eukaryota
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|sub-kingdom        =
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|phylum            =Euglenozoa
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|super-class        =
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|class              =Kinetoplastea
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|sub-class          =
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|super-order        =
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|order              =Trypanosomatida
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|sub-order          =
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|super-family      =
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|family            =Trypanosomatidae
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|sub-family        =
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|genus              =Leishmania
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|species            =
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}}
 
[[Image:Leishmania Life Cycle.jpg|thumb|right|150px|Leishmania Life Cycle - Wikimedia Commons]]
 
[[Image:Leishmania Life Cycle.jpg|thumb|right|150px|Leishmania Life Cycle - Wikimedia Commons]]
 
[[Image:Leishmania donovani.jpg|thumb|right|150px|''Leishmania donovani'' in bone marrow cell - Dr. L.L. Moore, Jr.]]
 
[[Image:Leishmania donovani.jpg|thumb|right|150px|''Leishmania donovani'' in bone marrow cell - Dr. L.L. Moore, Jr.]]

Revision as of 08:58, 2 August 2010



Leishmania spp.
Kingdom Eukaryota
Phylum Euglenozoa
Class Kinetoplastea
Order Trypanosomatida
Family Trypanosomatidae
Genus Leishmania
Leishmania Life Cycle - Wikimedia Commons
Leishmania donovani in bone marrow cell - Dr. L.L. Moore, Jr.
L. tropica

Yutaka TsutsumiWikiMedia Commons

Overview

Leishmania spp. are intracellular parasites of macrophages from the same family as Trypanosoma spp.. These organisms parasitise human, dogs and wild animals throughout southern Europe, Africa, Asia and South America. The infection is transmitted by sandflies. Infection can cause both cutaneous and visceral disease. Three types of Leishmania spp. are described;

  1. Hypoplaria - found in lizards that ingest the sandfly intermediate host. Development occurs in the hindgut of the fly.
  2. Peripylaria - found in mammals and lizards, development occurs in the fore- and hindgut of the fly.
  3. Suprpylaria - found only in mammals transmitted by the bite of a sandfly, development occurs in the fore- and midgut of the fly.

Recognition

Leishmania spp. are ovoid shaped parasites containing a rod shaped 'kinetoplast'. The kinetoplast is associated with a rudimentary flagellum that does not extened beyond the cell margin. The position of the kinetoplast changes as the parasite changes between life stages. Once ingested by a sand fly the parasite takes the promastigote form and the kinetoplast moves the the posterior of the cell.

Life Cycle

  • Transmitted by blood sucking sand flies
    • Phlebotomus spp. in the Old World
    • Lutzomyia spp. in the New World
  • The amastigote (morphological form) is found in vertebrate macrophages
  • Multiplies and migrates to insect proboscis
    • Inoculated during feeding
    • Can be transmitted percutaneously if sand fly crushed on skin
  • Multiplies by binary fission

Pathogenesis

  • Infection of vertebrate host
    • Produces foci of proliferating Leishmania-infected macrophages in skin (cutaneous) or internal organs (visceral)
  • Very long incubation period
    • Months to years
  • Many infected dogs are asymptomatic
  • Cutaneous form
    • Produces areas of ulceration on pinnae of ears, eyelids or on the lips
  • Visceral form causes chronic wasting condition
    • Generalised eczema
      • Loss of hair around eyes producing 'spectacle' effect
    • Intermittent fever
    • Generalised lymphadenopathy
  • Long periods of remission followed by recurrence of clinical signs is not uncommon in infections

Epidemiology

  • Disease dependent on sand fly vectors
    • E.g. Common in dogs around the Mediterranean coast, foci around southern Europe and around Madrid
  • Reservoirs of infection
    • E.g. Wild animals such as rodents and stray dogs
  • Mechanisms of transmission
    • sand fly bite
    • Rarely through direct contact
  • Leishmaniasis in British dogs
    • Susceptible to infection if exposed whilst abroad in endemic areas as have no immunity
    • No sand flies in Britain but dogs have become infected whilst in contact with infected imported animals

Diagnosis

  • Demonstrate Leishmania organisms

Treatment and Control

  • Chemotherapy
    • Prolonged treatment, expensive, suppresses infection
    • Does not cure infection
  • Destruction of infected and stray dogs
    • Sand flies biting infected dogs may spread the disease to other dogs, humans and wildlife
    • There is a slight possibility of transmission to humans by direct contact


In dogs

  • disseminated disease of the monocyte-macrophage system
  • protozoa; genus Leishmania
  • increased travel means clinincal disease may be acquired in endemic areas but now presents to veterinarians in non-endemic areas
  • lymph node aspirates contain macrophages with organisms