Leishmania Flashcards
What DIVA stands for
-differentiate between infected and vaccinated
-DIVA vaccine doesn’t elicit Ab response or Ab produced are different from natural infection
What does DAT stands for?
-direct agglutination test
-serology that directly detect Ab to whole promastigotes
-no intermediate steps
What is FAST?
-fast agglutination screening test
-similar with DAT
-faster reading
What does ELISA detect?
-serology that detects Ab to soluble, purified or recombinant Ag of Leishmania
What does IFAT detect?
-serology indirectly detects Ab to whole promastigotes of Leishmania
What does LPA stand for?
Leishmania promastigote Ag: whole parasite
-detect Ab specific to Lesihmania
What is Leishmanin skin test?
-Intradermal test
-may induce delayed type hypersensitivity
What are vectors ?
Old world- Phlebotomus L.infantum
-New world- Lutzomya L.chagasi
Which other vectors of leishmania have been recognised?
-tick
-flies
What else do sand flies transmit ?
-Bartonella baciliformis (Orayo fever )
-Lyme
-Toscana virus
What is Kala-azar?
visceral Leishmaniasis in people caused by L.donovani
What sources of infection?
-dog (main reservoir)
-wild dogs
-rodents
-wild mammals
What are the types of leishmania in people and dogs?
People:
1. Cutaneous
2. Mucocutaneous
3. Visceral
Dogs:
1. visceral - always cause both cutaneous and visceral disease
What is definition of clinical leishmaniosis ?
-clinical signs and/or clinicopathological abnormalities and confirmed L.infatnum infection
What is subclinical leishmaniosis
-no clinical signs, no clinicopathological abnormalities but confirmed leishmania infection
-self-limited disease
What is the prevalence of infection in endemic areas ?
> 50%
-disease prevalence 3-10%
What are the 2 major patters of progression?
- Acute- severe
-shortly after infection
-unable to develop effective cellular immune response
-develop strong humoral response - Chronically infected
-no lesions, no clinical disease
-but change in health status or immunosuppressive drug/disease can activate infection
What are the ways or transmission in non endemic ares?
- travel dogs
- no travel history but live with imported dogs
- Pups born from infected queens
- Blood transfusion
- Climate changes?
- shared syringes
- licking of wounds by an infected animal
What is life cycle of Leishmania
DIPHASIC parasite-2 host to complete life cycle
1. Sand fly-harbours flagellated extracellular promastigotes (infective)
2. Mammal-intracellular amastigote form develops and replicate
Incubation?
3 months to 7 years
How do sand flies infect mammals /pathogenesis
-they inoculate promastigotes from gut via proboscis (only females feed with blood, males on plants)
-enter dermis and phagocytosed by macrophages
-in phagosome vacuoles and try to eliminate it by NO, lysosomal hydrolyses
-if leishmania escapes , multiplies in macrophages
+ has SUPEROXID DISMUTASE
-progress of infection depends on host immune response
What systemic lesions are found in diseased animals
- poor body condition
- generalised muscle atrophy -myositis / masseter
- lymphadenomegaly
- renal disease: interstitial nephritis, glomerular deposition of parasite Ag, amyloidosis , deposition of immune complexes
- increased blood pressure - due to increased proteinuria, reduce GFR
- splenomegaly -increase in monocytes and macrophages
- joint and bone lesion- erosive/non-erosive poly arthritis, osteolysis, joint swelling, osteoporosis-proliferative bone lesion
- ocular lesion- anterior uveitis, kcs, blepharitis
- homeostatic disorder- platelet aggregation abnormalities, low plt, decrease coat factors, fibrinolysis, nose bleeding, hematuria, hemorrhagic diarrhoea
- anemia- renal disease or decreased erythropoietin + blood loss, immune mediated blood loss
- ch hepatitis, colitis, neurological disease (meningitis), autoimmune disorder , pericarditis, vasculitis, thromboembolism, hyper viscosity syndrome
Histopathologic changes ?
- Periadnexal nodular to diffuse pyogranulomatous/granulomatous dermatitis (+ orto/para HK, acanthosis, crusting, ulceration, macrophages and amastigotes, obliteration of sebaceous glands (SA dDX), decrease in col I, III
- Suncorneal pustular dermatitis
- Lichenoid dermatitis
- Vasculitis
- Panniculitis
Genetic susceptibility is seen ?
- Age: <3, >8
- breed: boxer, Rotweiler, cocker, GSD, foxhound
- Sex: maybe male
Which breed is resistant to lesihmania?
Ibizan hound
Which genes are involved in resistance/susceptibility?
- NRAMP1=Slc11a1
- certain alleles of MHC II genes (DLA-DRB1)
- TAG-8-141 (boxer predisposed to CanL)
Which type of immune response is protective?
Cell mediated
-production of CD4+ Th1
-release of IFN-gamma, TNF-alpha, IL-2
-macrophage secrete NO and intracellular killing of Leishmania
-apoptotic cell death controlled by proteasome inhibitors
Which test are used for evaluation of cellular immunity?
- Leishmanin skin test
- Lymphocyte proliferation test + clinical evaluation
Mild papular dermatitis represent which type of Th response?
-mix of Th1 and Th2
-early infection: IFNgamma produced by NK cels and phagocytes
-Later: balance between Th1 and Th2 , inhibit bacterial activity of infected macrophages (spleen cells from infected dogs have increased IL-10)
TLR: decrease expression / associated with disease progression/ parasites down regulate expression?
Name diagnostic methods ?
- PCR- based on kinetoplast DNA more reliable (RT-PCR detects extreme low levels of parasites)
- Culture
- Serology: IFAT, ELISA; DAT, western blot, immunochromatography (may cross react with T.cruzi)
- Cytology
- Histopathology/IHC (biopsies not from chronic lesions)
What is the % of asymptomatic dogs to have leishmania in clinically normal skin?
20%
Serology is usually when performed?
- To confirm the disease
- investigate presence of infection (epidemiological status, blood transfusion, import of infected dogs, monitor response to treatment )
- Negative status- repeat after 3 months
What are ddx ?
- DLE
- SLE
- PF
- PE
- dermatophytosis
- SA
- Zn- resposnive dermatitis
What are the steps in diagnosing leishmania ?
- Detection of specific Ab by serology (IgG)- quantitative serology: IFAT, Elisa
- Demonstration of parasite DNA in tissue by molecular techniques: parasitological diagnosis
-conventional, nested, real time PCR - Conclusive- microscopic finding of parasite
How to diagnose leishmania in vaccinated dogs?
- compatible clinical signs, clinicopathological abnormalities
- no serology alone, combined with detection of DNA parasite by PCR or cytology