Parasitology INM module

1. Malaria 2. Leishmaniasis 3. Toxoplasmosis 4. Filariasis

Define high receptive areas of Malaria

Areas with high densities of the major vector Anopheles culicifacies

What are the 2 hosts necessary for the Plasmodium sp. to complete their life cycle?

1. Definitive host

2. Intermediate host

What is the definitve host of the Plasmodium sp.?

The female Anopheles mosquito where the sexual phase of the parasite’s life cycle takes place.

What is the intermediate host of the Plasmodium sp.?

Man, where the asexual phase of the Malaria parasite’s life cycle takes place.

What the advantages of serology in diagnosis of malaria?

1. A tool to screen blood donors

2. Screening blood donors involved in cases of transfusion induced malaria when donor’s parasitemia may be below detectable level of blood film

What are the disadvantages of serology in diagnosis of malaria?

1. Doesn’t detect current infection (only measures past exposure)

2. Not practical for routine diagnosis of acute malaria (time required for antibody development and persistence of antibodies

3. Cross reactions between Plasmodium sp. and Babesia sp.

Why is serology not suitable for diagnosis of acute infections of malaria?

Detectable levels of anti-malaria antibodies do not appear until after the infection and persist long after parasitemia has resolved

What are the central features of Pathogenesis of P.falciparum malaria?

Cytoadherence

Rosetting

Agglutination

What are the complications of P.falciparum malaria?

1. Jaundice

2. Cerebral malaria

3. Generalized convulsions

4. Severe normocyctic anaemia

5. High fever (39-40oC)

6. Hypoglycemia

7. Acute renal failure

8. Hyperparasitemia

9. Malaria hemoglobinuria

10. Cicruclatory collapse, shock, septicemia

11. Acute pulmonary edema and ARDS

12. Abdominal bleeding

13. Metabolic acidosis with respiratory distress

14. Fluid electrolyte imbalance

What are the drugs used to treat acute malaria in Sri Lanka?

1. Chloroquine

2. Quinine

3. Artemisinin derivatives

4. Lumefantrine

What are the drugs available to treat acute malaria besides those used in SL?

1. Halofantrine

2. Proguanil

3. Pyrimethamine

4. Sulphones and sulphate

5. Mefloquine

Name the drugs used in chemoprophylaxis of malaria in SL

Mefloquine

What are the adverse effects in choloroquine?

1. NVAD

2. Corneal deposits (dose and time related and usually occurs when cumulative dose >100g )

3. Retinopathy/maculopathy

4. Qt prolongation

5. Headaches

6. Dizziness

7. Convulsions

8. Hyperpigmentation (skin,nails)

9. Hair loss and depigmentation

10. Pruritus , skin reactions

11. Hemolysis in G6PD deficiency

What are the cautions to be considered when administering chloroquine?

1. Diabetes

2. Psoriasis

3. Myasthenia graves

4. Long term therapy

5. Neurological disorders- especially epilepsy hx.

6. Severe GI disorders

7. Acute porphyrias

8. G6PD deficiency

What is chloroquine effective against?

1. Blood schizonts of

a. P. vivax

b. P. Ovale

c. P.malarie

2. Gametocytes of

   a. P.vivax.

What is chloroquine NOT effective against?

1. Blood schizonts of P.falciparum (due to drug resistance)

2. Hypnozoites of P.vivax and P.ovale

3. Gametocytes of P.falciparum

What are the clinical uses of chloroquine?

Treatment of

1. P vivax

2. P Ovale

3. P malariae

What is the dosage of chloroquine administered?

Chloroquine base at a dosage of 25 mg/kg over three days

Day 1 and 2(10mg/kg)

600mg CQ sulphate (4tabs) - single dose each day

Day 3 (5mg/kg)

300mg CQ sulphate (2tabs) - single dose

What does relapse mean in the context of malaria?

Infection without an infective bite/Reactivation of malarial infection via hypnozoites

What is recrudescence in malariae?

The situation in which parasitemia falls below detectable levels and then later increases to a patent parasitemia

What is the average incubation period of malaria?

7-30 days

How many merozoites are released in the rupture of a Plasmodium falciparum erythrocytic schizont?

24-32 merozoites

How many merozoites are released in the rupture of a Plasmodium vivax erythrocytic schizont?

12-16

State the virulence factors of P.falciparum that result in sever malaria.

1. Hn

How long can the hypnozoite lay dormant in P.vivax?

Up to 5 years

What is the distribution of toxoplasmosis?

Worldwide

State the definitive host of toxoplasmosis

Cat

State the intermediate host of toxoplasmosis

Warm blooded animals including humans, birds and rodents

What is the causative agent of toxoplasmosis?

Obligate intracellular parasite Toxoplasma gondii

What is depicted in the image?

Toxoplasma gondii sporulated oocyst in an unstained wet mount

What is depicted in the image?

Toxoplasma gondii tachzyoites stained with Giemsa

What is depicted in the image?

Toxoplasma gondii tissue cyst with bradyzoites seen within the cyst

How does the definitive host get infected with toxoplasmosis?

By ingestion of tissue cysts or sporulated oocysts

How long do Toxoplasmosis oocysts take to become infective?

Once shed in cat feces, they take 1-5 days to sporulate in the environment and become infective

How do intermediate hosts become infected with toxoplasmosis?

After ingestion of plant matter, soil or water contaminated with oocysts

What is the clinical manifestation of toxoplasmosis in otherwise healthy individuals?

Majority of patients (85-90%) are asymptomatic

• Febrile illness with malaise

• Fatigue

• Headache

• Muscle pain

• Cervical and axillary lymphadenopathy

What is the clinical manifestation of toxoplasmosis in immunosuppressed individuals?

Severe infection with high fever and skin rash

Meningo-encephalitis

Pneumonitis

Myocarditis

Hepatitis

What is the classical triad for congenital infections of toxoplasmosis?

1. Chorioretinitis

2. Hydrocephalus

3. Intracranial calcifications

What is the clinical manifestation in relapse of toxoplasmosis in immunosuppressed individuals?

Headache

Confusion

Nausea/vomitting

Fever

Poor cordination

When can ocular toxoplasmosis come about?

Reactivation of congenital acquired toxoplasmosis infections

Reactivated retinal cysts cause tissue damage and inflammation

Commonly seen in teenagers and young adults

Describe the immune response in toxoplasmosis.

• Stimulates both cellular and humoral immune response

• Cell mediated immune response is important in controlling the infection

• IgM and IgA appear early in the infection

• IgG appear 2-3 weeks after and peak at 6-8 weeks

List the diagnostic methods of toxoplasmosis.

1. Serologic tests

2. Molecular techniques

3. Direct visualization of the parasite and/or its antigens'

4. By isolation of the parasite

What are the serological tests that can be used for the diagnosis of toxoplasmosis?

1. Enzyme linked immunosorbent assay (ELISA)

2. TORCH screen

3. Lateral flow chromatographic assay

4. Indirect fluorescent test (IFT)

5. Agglutination tests

6. Complement fixation tests (CFT)

State methods of direct demonstration of the toxoplasmosis parasite.

1. Mouse inoculation

2. Cell cultures

3. Autopsy material - Brain, fetal tissue

4. Biopsy material - Bone marrow, lymph nodes

What is the treatment for toxoplasmosis in immunocompetent symptomatic patients?

1. Sulfadiazine+pyrimethamine+Folinic acid OR

2. Trimethoprim sulfamethoxazole

How is ocular disease of toxoplasmosis in adults treated?

1. Sulfadiazine+pyrimethamine+folinic acid OR

2. Intravitreal clindamycin + dexamethasone

Why and how should folinic acid (leucovorin) be given in the treatment of toxoplasmosis?

For prevention of hematological toxicity

Should be given during and for one week after pyrimethamine therapy

How are immunocompromised patients with toxoplasmosis treated?

1. Sulfadiazine + pyrimethamine + folinic acid OR

2. Pyrimethamine + folinic acid + clindamycin OR

3. Trimethoprim sulfamethoxazole

How is a congenital infection of toxoplasmosis treated?

Sulfadiazine + pyrimethamine + folinic acid

Started ASAP after birth and continued for at least one year

How is toxoplasmosis treated in pregnancy if POA < 14 weeks with no fetal infection?

Spiramycin

Can pyrimethamine be given for treatment of toxoplasmosis in first trimester?

No, pyrimethamine is teratogenic in the first trimester

List the primary prevention methods of toxoplasmosis.

1. Dispose of cat feces daily

2. Eating well cooked meat

3. Wash hands thorougly with soap and water after handling raw meat or gardening

4. Washing vegetables and fruits before consumption

How would you prevent transmission of toxoplasmosis through blood transfusions and organ transplants?

1. Screening potential organ donors

2. Transfusing antibody negative blood to high risk patients

3. Transfusing leucocyte depleted blood components

State the causative agent for visceral leishmaniasis.

Leishmania donovani complex

State the causative agent for muco-cutaneous leishmaniasis.

Leishmania braziliensis

State the causative agent for cutaneous leishmaniasis

Leishmania major

Leishmania tropia

Leishmania aethiopica

State the morphological forms of the causative agent of leishmaniasis.

Amastigote

Promastigote

State the morphological features of amastigote.

1. Rounded shape

2. Non flagellated

3. Non motile

4. Found in host cells

5. Enters sandfly vector during a blood meal

State the morphological features of promastigote.

1. Thin and elongated in shape

2. Motile

3. Flagellated

4. Found inside sandfly or in culture

5. Enters host when infected sandfly bites the host

State the vector of leishmaniasis.

Infected female sand fly

Smaller than mosquitoes, light brown in color

State the incriminated vector species of leishmaniasis in humans.

Phlebotomus in the Old World

Lutzomyia in the New World

State the probable vector of Leishmaniasis in Sri Lanka.

Phleobotomus argentipes

State the hosts of Leishmania parasites.

Mammals:

• Humans

• Rodents

• Cattle

• Dogs

State the methods of leishmania transmission

Zoonotic

Anthropronotic

What are the clinical types of cutaneous leishmaniasis?

1. Papules

2. Nodules

3. Plaques

4. Ulcers

What are papules in the context of cutaneous leishmaniasis?

Very small palpable lesions raised above the skin

Longest diameter is less than 1 cm

What are nodules in the context of cutaneous leishmaniasis?

palpable lesions raised above the skin

Longest diameter is more than 1 cm

What are plaques in the context of cutaneous leishmaniasis?

A palpable flat lesion more than 1 cm in diameter

What are ulcers in the context of cutaneous leishmaniasis?

‘Volcanic’ in appearance with a raised border and a central crater

What are the main organs affected by visceral leishmaniasis?

1. Liver

2. Spleen

3. Bone marrow

State common clinical signs and symptoms of visceral leishmaniasis.

1. Rigors and chills

2. Lymphadenopathy

3. Pancytopenia

4. Non tender splenomegaly with or without hepatomegaly

5. Weight loss

How is mucocutaneous leishmaniasis caused?

1. Cutaneous lesions extending directly to adjacent mucuos membranes

2. Metastasis of cutaneous lesions via lymphatic or haematagonous spread to mucosal layer of mouth and upper respiratory tract

What are the signs of nasal involvement in mucocutaneous leishmaniasis?

Stuffed nose

Nasal bleeding

Where are the lesions of mucocutaneous leishmaniasis commonly seen?

Mouth

Nose

Throat

What is post kalar-azar dermal leishmaniasis (PKDL)?

It is a cutaneous sequela of visceral leishmaniasis, common with VL caused by L.donovani

What is the appearance of Post kalar-azar dermal leishmaniasis?

Hypopigmented or erythematous macules papules or nodules appearing on exposed parts of body such as face, arms and upper part of body

Wha is the most common clinical form of leishmaniasis seen in leishmaniasis HIV co -infection?

Visceral leishmaniasis

What is disseminated cutaneous leishmaniasis?

Co existence of different types of lesions such as papules, nodules and ulcers

What is diffuse cutaneous leishmaniasis?

Chronic

Non ulcerating

Non necrotising

Multiple skin lesions widespread over the body except on

• Scalp

• Axillae

• Inguinal folds

• Palms

• Soles

Where are samples obtained for testing in CL, MCL and VL?

CL and MCL - samples are obtained from active edge of lesion

VL

1. Bone marrow aspirate

2. Liver aspirate

3. Lymph node aspirate

4. Spleen aspirate

5. Buffy coat of whole blood

List methods of sampling used in testing for leishmaniasis.

1. Tissue scraping/ split skin smear

2. Biopsy of lesion

3. Blood for serology

4. Tissue-impression smear

5. Bone marrow aspirate

6. Fine needle aspiration

State laboratory methods used to confirm the diagnosis of leishmaniasis.

1. Parasitological

   1. Light microscopy

   2. Culture

2. Molecular methods

   1. PCR

3. Serological methods

   1. Dipstick assays

   2. ELISA

What is the most commonly used method in parasitological diagnosis of Leishmaniasis currently?

Demonstration of amastigotes by light microscopic examination of Giemsa stained lesion material

What are smears prepared from for light microscopy?

Slit skin scrapings

Lesion aspirates

Bone marrow aspirates

Impression smears from biopsies

In which type of leishmaniasis are serological methods used?

Visceral leishmaniasis since most patients don’t develop a significant antibody response in CL.

What is the specific antigen used in serological methods to detect the specific antibody against the L.donovani complex?

rK39 antigen in ELISA and ICT

What is the currently used main molecular diagnostic method of leishmaniasis?

Detection of parasitic DNA using PCR-based assays

List the challenges faced in the diagnosis of leishmaniasis.

1. Lack of pathognomic clinical features

2. Wide spectrum of clinical features

3. Existing as co-infections with other diseases

4. Overlapping with clinical features of other common diseases in the region such as malaria, leprosy and tuberculosis

What are tissue impression smears?

They are ‘imprints’ of the biopsy

Describe how a tissue impression smear is prepared and used in leishmaniasis diagnosis.

It is prepared by rolling the freshly cut surface of the biopsy on a clean glass slide

The glass slide is stained with Giemsa to observe under microscope

If there is a lot of blood, it must be blotted prior to making the smear.

What are the measures taken for control and prevention of leishmaniasis?

1. Personal protective measures to reduce contact with sandflies

2. Early diagnosis and effective treatment

3. Vector control measures targeting adult sandflies

4. Health education

5. Notification and active surveillance

What is the treatment for intestinal amoebiasis?

Metronidazole for 5 days

Diloxanide furoate (500 mg tds - 10 days)

What is the treatment for extra intestinal amoebiasis?

Metronidazole for 5-10 days

Diloxanide furoate (500 mg tds - 10 days)

List the available laboratory tests for amoebic diseases

1. Concentration technique

   1. Floatation technique

2. Direct smears

   1. Saline

   2. Iodine

3. Staining - help differentiating amoebae

   1. Iron-hematoxylin

   2. Trichome

4. Imaging

5. Serology - useful in invasive forms - esp extra intestinal amoebiasis

6. Blood - leucocytosis

7. Stool culture - not routinely used

8. Colonoscopy - may reveal colonic ulcers and can take biopsies from lesion for microscopy/histopathology