Exercise 4: Blood and Tissue Flagellates: Leishmania and Trypanosoma

1. Trace the lifecycle of

a. Trypanosoma brucei gambiense and T.b. rhodisiense

b. Leishmania species

2. Discuss the pathogenesis, pathology, clinical manifestations and laboratory diagnosis of:

a. African Sleeping Sickness

*Pathogenesis, Pathology, Clinical Manifestations • Incubation Period (IP): 2-23 days

• Trypomastigotes found in the bloodstream, LN, CNS (CSF) – trypomastigote stage

• Lodge at site of injection or bite

• Local inflammation • Into the bloodstream- parasitemia

• LN: marked proliferation of endothelial cells in sinuses, leukocyte infiltration around the blood

vessels

• CNS - arachnoid spaces - lymphoplasmacytic infiltrate - perivascular proliferation of endothelial and neuroglia cells

• Initial lesion: chancre - Elevated and painful - Later becomes indurated

• During IP: nonspecific manifestations - Local irritation - Headache - Fever - Chills - Loss of appetite

• Symptomless patent period

• Abortive, lymphatic stage, CNS type – meningoencephalitis stage

❖ Acute Febrile Period – Hemolymphatic Stage

• Invasion of LN

• Fever

• Enlargement of spleen, liver, LN • Winterbottom’s sign – enlargement of posterior cervical lymph nodes

• Kerandel’s sign – hyperesthesia; patient reacts in an exaggerated way to painful stimulus

• Edema: hips, hands, legs

❖ 2nd stage: Meningoencephalitic Stage

• CNS invasion • Sleeping sickness stage

• Headache • Mental dullness

• Apathy

• Muscle spasms

• Disturbed

❖ Death

• From asthenia

• Complications:

- Malaria

- Hookwork infection - Schistosomiasis

- Pneumonia

- Dysentery

Laboratory Diagnosis

• (+) symptoms

• Endemic area • Demonstration of parasite in the blood, LN juice, sternal bone marrow, CSF

b. Chagas’ disease

Pathogenesis and Pathology

• Organisms are engulfed by histiocytes in the adipose and muscle tissues and they multiply as

amastigotes.

• At nearby LN, there is proliferation of histiocytes. • Chagoma – appearance of small, painful, reddish nodule in the site of inoculation

• Via blood or lymph: LN, lung, spleen, liver multiply in fixed histiocytes, muscle fibers,

Clinical Manifestations • IP: 7-14 d

• Acute form

- Children: 20-30 d

- High fever, edema - LN, spleen, liver enlargement • Romaña’s sign – edematous eyelid and conjunctiva; unilateral periorbital edema

• Chronic form

- Digestive form: megaesophagus, megacolon (myenteric and mesenteric plexuses are destroyed) - Cardiac enlargement due to direct destruction of heart muscle cells – compensatory mechanism

- Neurologic form: aphasia, paraplegia, spastic paralysis

Laboratory Diagnosis

• Demonstration of the parasite in the blood or tisues

• Xenodiagnoses – live human being; Laboratory-reared triatomine bugs are allowed to feed on patients suspected of being infected then the bugs are later examined for the presence of T. cruzi.

• Serologic test – not so helpful in endemic area

c. Old World Cutaneous Leishmaniasis

Pathogenesis, Pathology • Early stage: proliferation of macrophages with amastigotes

• Lymphoplasmacytic infiltrates • Epithelium: acanthosis (thickening of the epidermis), parakeratosis (nuclei are retained in the

superficial epidermis)

• Necrosis, ulceration • Healing: granulation tissue (redness/bluish discoloration around lesion)

• Secondary bacterial infection is common

Clinical Manifestations • IP: few days to 6 months

• Single or multiple

• Primary lesion: site of bite • Papules and nodules (solid raised lesion > 1 cm)

• Ulcers

• Relapsing lesions (leishmaniasis recidiva/lupoid leishmaniasis)

Laboratory Diagnosis: Amastigote • Puncture indurated edge of sore

• Biopsy of lymphoid material at the edge of ulcer • Leishmanin reaction

o Montenegro skin test

o Intradermal injection of washed promastigotes o Delayed hypersensitivity reaction

d. Mucocutaneous Leishmaniasis

Pathogenesis • Similar to oriental sore

• Invade mucous membrane ( no keratinization)

• Direct extension or metastasis (lymphatic channel or bloodstream) • Minimal to mutilation of the face

o Espundia- destruction of nose & palate

Pathology • Papules, ulcers: same as oriental sore

• Espundia: nose, mouth, larynx

o Polyps in nasal cavity/pharynx o Fungating & indurated ulcers

o Tongue, gums, buccal mucosa

o Histiocytes: containing amastigotes

Clinical Manifestations • Chiclero ulcer: face, ears

• Pian bois (forest yaws): can metastasize

o Ulcerative lesion

• Panamania: one or few ulcers, metastasis • Uta: self limiting, no metastasis (usually just one, from one sandfly)

• Espundia: most notorious

o Mutilitation, persistence • DCL: papules to plaques to nodules

Laboratory Diagnosis • Puncture edge of initial ulcer

• Nodules or ulcers at the mucus membrane

• Culture- promastigotes

• Montenegro test (+) infected

(-) uninfected

e. Kala-azar or Visceral Leishmaniasis

Pathogenesis • Amastigotes multiply slowly • Macrophages free in bloodstream to viscera

• Spleen, liver, bone marrow

• Marked proliferation of macrophages

• Leukopenia • Anemia

• Thrombocytopenia

• Spleen, liver enlarged • Lymphadenopathy

• Hyperglobulinemia: relative increase in globulin levels because of hypoalbuminemia

• Simulate as Aplastic Anemia

Pathology • Spleen: prominent Malphigian corpuscles (seen in the white pulp)

• Liver: fatty infiltration, amastigotes • BM: parasites in macrophages

• Heart: myocardial degeneration

• Kidneys: hydropic change (swelling of renal tubular cells) • Lymph nodes: hyperplastic

• Intestine: parasite in submucosa, ulcers

o Coinfection: amoebiasis, hookworm infections

• PBS: anemia, leukopenia, low platelet count

Clinical Manifestation • IP 10 days to > 1 year (2-4 months) • Leishmanoma (nodular lesion at the site of bite): initial lesion

• Malaise, headache, fever

• Splenomegaly • Anemia

• Emaciation

• No ascites

• Post kala-azar dermal leishmaniasis (PKDL): reactivation of the disease , localized to the skin

Laboratory Diagnosis • Splenic puncture

• BM biopsy

• Lymph node aspiration • Montenegro skin test