Bloodstream: Hemoflagellates, lymphatic filariasis Flashcards
Hemoflagellates
Flagellated protozoa that are found in peripheral blood circulation. Eg., leishmania and trypanosoma (transmitted by insect vector)
Oval to elongated body, nucleus and a single flagellum arising from kinetoplast (multiple mDNA)
Axoneme is present
4 morphological forms: amastigote, promastigote, epimastigote, trypomastigote
Leishmaniasis
By obligate intercellular protozoa Leishmania, which primarily affects the reticulo endothelial system
Transmitted by female sandfly bite
Three forms: visceral leishmaniasis, PKDL, cutaneous forms
Two sub genera: L leishmania and vienna
Visceral leishmania
Caused by Leishmania donovani
Promastigote - infective form in alimentary canal of female sandfly
Pentad: 🤒, progressive weight loss, hepatosplenomegaly, pancytopenia and hypergammaglobulinemia
Death occurs due to superimposed infections, anemia and hemorrhages
Life cycle of Leishmania donovani in human
In humans:
- Promastigotes are phagocytosed by the skin macrophages and turn into
- Amastigotes which multiply within macrophages causing cell rupture and are released into circulation.
- Amastigotes leave the circulation to liver, spleen and bone marrow and invade invade RES cells like macrophages, endothelial cells.
Life cycle of Leishmania donovani in sandfly
- During blood meal, amastigotes are ingested
- They reach midgut, then ransform into promastigote
- Multiplication and then migration to foregut
Pathogenicity of visceral leishmania
- Phagocytosis of promastigotes is facilitated by binding of its surface antigens such as gp-63 and LPG lipophosphoglycan
- LPG - principle virulence factor preceding phagosome maturation and protects the parasite against phagolysis
- GPI protects from phagolysis.
Visceral Leishmaniasis
host response
- TH-1 response:
• CMI ➡️ macrophage activation ➡️ amastigotes killed
• observed in cutaneous leishmaniasis and patients after recovery/treated for VL
• delayed type hypersensitivity developed - TH-2:
• polyclonal B cell activation ➡️ hypergammaglobulinemia
• observed in patients with active VL and diffuse CL
• negative for leishmanin skin test
• pathogenesis
Visceral leishmaniasis Kala azar
Clinical features
- Pentad: 🤒, progressive weight loss, hepatosplenomegaly, pancytopenia and hypergammaglobulinemia
- Lymphadenopathy and leishmanoma in African
- Hyperpigmentation in Indian
- Pedal edema and ascites in advanced illness
- Mucosal lesions in African
Post-kala-azar dermal leishmaniasis
PKDL
Non-ulcerative lesson of skin in some patients of VL following treatment with antimonials
Aggravated on exposure to sunlight
Develops as hypopigmented macule near mouth which spreads to face, arms, trunk and finally becomes nodules resembling leprosy
Conjunctivitis and uveitis in some
Post-kala-azar dermal leishmaniasis
PKDL
Diagnosis and treatment
Diagnosis: 1. Amastigotes in nodular lesions 2. Direct agglutination test DAT 3. Antibodies to rK39 antigen DoC: amphotericin B
Leishmaniasis
Lab diagnosis
- Microscopy
- Culture
- Antibody detection
- Antigen detection
- Molecular method
- Leishmanin test
- Animal inoculation
Leishmaniasis
microscopy and culture
Microscopy: Giemsa staining detects LD bodies
1. Splenic aspiration: Most sensitive
2. Bone marrow aspiration: Lymph node aspiration
3. Liver biopsy
4. Peripheral blood smear: in HIV
Culture: species investigation and drug sensitivity
1. NNN medium
2. Schneider’s liquid medium
Leishmaniasis
antibody tests
- Direct agglutination test:
100% sensitive and specific, simple, rapid
Ab persist for 5 years - Immunochromatographic test ICT:
Similar to DAT, but with less sensitivity in East Africa and HIV patients - ELISA and IFA
Leishmaniasis
Antigen detection
Latex agglutination test for Ag in urine Good specificity but variable More useful in: 1. HIV-VL co-infection 2. As a prognostic marker 3. Indicating active infection
Leishmanin test
Montenegro test
Skin test to detect delayed hypersensitivity to a suspension of killed L. donovani promastigote injected intradermally
Positive in people with good CMI
Negative even active VL and diffuse CL
Treatment of visceral leishmaniasis
- Pentavalent antimonials
- Liposomal amphotericin B: current DoC
- Miltefosine
- Paromomycin
- Immunotherapy
Leishmaniasis
control measures
- Personal prophylaxis using insect repellents or bed nets
- Control of canine or rodent reservoir
- Phlebotomus does not fly high and is nocturnal. So 😴 at higher floors can prevent
Chaga’s disease
Life cycle of T. cruzi in humans
- Rubbing of vector feces on abraded skin
- Trypomastigotes are carried to various tissues
- Amastigotes form and multiply intracellularly in RES, muscles and nervous tissue
- Trypomastigotes are reformed in peripheral blood (extracellular)
- Invasive ones migrate to many organs and short stubby forms are ingested by reduviid bugs
Chaga’s disease
vector cycle
- In gut of reduviid bugs, the trypomastigotes transform into epimastigotes
- In hindgut, it is further developed into metacyclic trypomastigotes
- Excreted in feces
Classification of trypanosomes
Trypanosomes are hemoflagellates that reside in peripheral blood and tissues of host
1. African trypanosomes:
T. brucei complex transmitted by vector tse-tse fly
African sleeping sickness
2. American trypanosomes:
T. cruzi transmitted by reduviid/triatomine bug
Chaga’s disease
Pathogenesis of Chaga’s disease
1. Early stage disease • Chagoma and Romana’s sign 2. Acute Chaga’s disease 3. Indeterminate Chaga’s disease 4. Chronic Chaga’s disease:
Early stage of Chaga’s disease
Characterized by:
- Chagoma: painful subcutaneous nodule at the site of deposition of bug feces (face,…)
- Romana’s sign: it causes unilateral painless edema of the eyelid and conjunctivitis
Acute and indeterminate Chaga’s disease
Acute Chaga’s disease:
In few early stage patients; 🤒, hepatosplenomegaly, lymphadenopathy
Indeterminate Chaga’s disease:
Asymptomatic, lasting for years to decades
Chronic Chaga’s disease
manifestations
The parasite multiplies in the muscles (cardiac and GIT) and nervous tissue
1. Cardiac form:
Dilated cardiomyopathy, arrhythmia, thromboembolism
2. Gastrointestinal form:
Megaesophagus and megacolon
Chronic Chaga’s disease
Mechanism
Molecular mimicry ➡️ ADCC
HIV and HTLV-II infected people are at higher risk of reactivation of underlying T. cruzi infection
Congenital trypanosomiasis
Rarely T. cruzi can be transmitted transplacentally both in acute and chronic stages. It manifests as:
- Low birth weight, stillbirth
- Rarely myocarditis and neural alterations
Chaga’s disease
lab diagnosis
1. Peripheral blood microscopy: Thick and thin 2. Culture for epimastigote forms 3. Ab detection for chronic 4. Ag from serum or urine for acute and congenital 5. Molecular method: most effective 6. Animal inoculation 7. Xenodiagnosis
Treatment for Chaga’s disease
Unsatisfactory
1. Acute:
Benznidazole DoC (Nifurtimox/ allopurinol)
2. Chronic:
Drugs ineffective with ADR
Surgery for megacolon, pacemakers for cardiac,…
Prophylaxis for Chaga’s disease
- Residual insecticides
- Health education
- Measures to reduce insect exposure
- Housing improvement
African sleeping sickness
By Trypanosoma brucei through tsetse fly inoculation into skin
Two types
Infective form metacyclic trypomastigote
It undergoes periodic antigen variation ➡️ changes in Variable Surface Glycoprotein VSG ➡️ evades immune response
African sleeping sickness
types
1. T. brucei gambiense: West African of humans primarily Chronic course with slow progression Winterbottom sign 2. T. brucei rhodesiense: East African of cattle primarily Rapid progression with early death High virulence and parasitemia
African sleeping sickness
life cycle in humans
- Site of inoculation, they transform into long slender trypomastigote
- Multiplication by binary fission
- Non-dividing short stumpy trypomastigote which invade bloodstream
- The rest migrate to other organs
African sleeping sickness
life cycle in tsetse fly
- Short stumpy trypomastigote becomes long slender
- The trypomastigote then becomes epimastigote
- Then metacyclic trypomastigote is formed- infective form
African sleeping sickness
stages of disease
treatment
Stage 1: hemolymphatic
Stage 2: CNS invasion
Drugs used are pentamidine and suramin (eflornithine, melarsoprol)
Treatment is based on the type (West or East) and the presence of CNS invasion.
African sleeping sickness
stage I: hemolymphatic stage
- Trypanosomal chancre:
Self limited lesion week after the bite - Asymptomatic period:
A few months - Systemic febrile illness:
Dissemination of parasites in lymphatics and bloodstream
• remittent irregular 🤒 with night sweats
• Winterbottom’s sign: post. cervical lymphadenopathy of West
African sleeping sickness
stage II CNS invasion
Progressive chronic meningocephalitis
Daytime somnolence with restless and sleepless nights
African sleeping sickness
lab diagnosis
- Direct microscopy
- Ag from serum and CSF: staging and prognosis
- Ab from serum and CSF
- Molecular methods: PCR, FISH
- Culture into KIVI
- Animal inoculation in 🐁 for East
African sleeping sickness
Microscopy
1. Blood: trypomastigotes Wet mount, thin/thick smear, concentration method 2. CSF examination: for invasion • trypomastigotes • WBC >20/μL 3. Lymph nodes for West Others are chancre fluid, bone marrow
African sleeping sickness
antibody tests
- Card agglutination test:
For trypanosomes b to detect Ab to VSG antigen - Semi-quantitative ELISA:
Using VSG antigen of T. brucei gambiense
Types of filariasis
- Lymphatic filariasis:
Eg., W. bancrofti, Brugia malayi, B. timori - Cutaneous and ocular filariasis:
Eg., Loa Loa, Onchocerca volvulus, Mansonella
Forms of filarial worms 🪱
1. Adult worm: Lymphatic filariasis 2. Larvae: 1st stage - microfilaria 3rd stage - filariform larva 3. Microfilaria: Can cause tropical pulmonary eosinophilia, but usually non-pathogenic
Bancroftian filariasis
host, vector and infective form
Intermediate host: mosquito 🦟
Principle vector: Culex quinquefasciatus
Infective form: L3 filariform larva
Bancroftian filariasis
human cycle
- L3 deposited in skin by 🦟 bite
- Penetrate skin ➡️ enter lymphatic vessels ➡️
- Local lymph nodes ➡️ adult worms upto 20 years,…
- Fertilization ➡️ microfilaria upto 1 yr
- Pre-patent period: b/w infection and diagnosis
82-142 days
Bancroftian filariasis
🦟 cycle
- Culex bites at 🌃 and Aedes bites at 🏙
- Microfilaria comes out of sheath ➡️ penetrates stomach wall ➡️
- Migrate to thoracic muscle ➡️ molt twice to L3
- Migrate to proboscis
Takes 7-21 days
Bancroftian filariasis
pathogenesis when 🪱 is alive
Related to migration of adult 🪱: 1. Lymphatic dilation 2. Thickening of vessel walls Related to antigens and toxic metabolites 2° bacterial and fungal infections Host inflammatory response: 1. Infiltration 2. 🔼 tortuosity of vessels and damage to valves
Bancroftian filariasis
pathogenesis after death of 🪱
🔼 granulomatosis and fibrosis of lymph vessels ➡️ lymphatic obstruction
Endosymbiosis b/w W. bancrofti and Wolbachia (rickettsia)
W. bancrofti is found to be infected with Rickettsia called Wolbachia and maintain an endosymbiotic relationship
Microfilaremia
Increases with age
Starts at 5 years and peaks at >30 years
🧔🏽♂️>👩🏽🦰 because of hormonal factors
Bancroftian filariasis
host immune response
Early infection:
Amicrofilaremic individuals- both TH1 and TH2
Microfilaremic individuals:
TH1🔽 & TH2🔼 so 🔼 IL-4,5,13,10, profound eosinophilia, IgE 🔼, 🪱 specific IgG-4
Chronic filariasis:
progression- IL-4,5,13,10
🪱 specific IgG-1,2,3
Bancroftian filariasis
clinical manifestations
- Lymphatic filariasis: 4 stages
• endemic normal
• asymptomatic microfilaremia
• acute adenolymphangitis
• chronic filariasis - Tropical pulmonary eosinophilia TPE or occult filariasis
- Immune complex mediated manifestations
Bancroftian filariasis
endemic normal
0-50% of normal people residing in endemic areas Not infected Reasons: 1. Insufficient exposure 2. Resistance 3. Prepatent period
Bancroftian filariasis
Asymptomatic microfilaremia
In endemic areas
Do not have symptoms of filarial infection, but microfilaria present
1. Microscopic hematuria, proteinuria
2. Dilated and tortuous lymphatics
3. Filarial dance 💃 sign:
Ultrasound shows adult 🪱 in scrotal lymphatics
Bancroftian filariasis
Acute filariasis or
Acute lymphangitis
- Filarial fever (high grade)
- Lymphatic inflammation: nodes and vessels
• lower extremities more common
• lymph nodes: firm, discrete, tender, enlarged
• male genital organs: funiculitis, epididymitis, orchitis (not in Brugian) - Transient local edema
Reversible (on raising) pitting edema - Dermatolyphangitis:
Plaque like lesions over nodes
In Brugian episodes more frequent and abrupt
Bancroftian filariasis
Chronic filariasis
It develops 10-15 years later 🪱 dead ➡️ granuloma and fibrosis ➡️ severe lymphatic obstruction ➡️ pedal edema 1. Hydrocele: M/C Straw colored fluid in tunica vaginalis 2. Elephantiasis: Lower limb, arm, vulva, breast 3. Chronic funiculitis 4. Chyluria
Bancroftian filariasis
Tropical pulmonary eosinophilia or
Occult filariasis
Hypersensitivity to filarial antigen
Rapidly cleared from blood, filtered, lodged and destroyed in 🫁
Microfilaria not detected in blood
Bancroftian filariasis
Immune complex mediated manifestations
Kidneys: nephrotic syndrome, hematuria, proteinuria
Joints: filarial arthritis of knee & ankle
