(after disappearance of microfilariae) varies from microscopic lesion to lymph varicosity to marked elephantiasis. High eosinophilia and superficial lymphadenopathy in Malayan filariasis. Pathology probably a general and focal sensitization response Blood: Thick and thin smears, concentration. Intradermal test gives useful group

 

L. donovani

Chronic febrile disease, causing hyperplasia and then blockage

of the reticuloendothelial system, particularly spleen and liver.

Irregular fever (may spike twice a day) with chills, sweating,

diarrhea, edema, cachexia, leukopenia, anemia. Splenomegaly

and leukopenia characteristic. (Incubation period: 2 to 9

months.) Untreated cases usually end fatally; with proper

treatment, fatality is under 5%

Blood: Thick and thin smears, culture in

NNN or Tobie’s diphasic blood agar. CF test

diagnostic; nonspecific tests such as Napier

and Chopra serum tests for screening; skin

tests for past infection. Nasal scrappings,

lymph node biopsy, sternal marrow and

splenic or hepatic aspirate. Stained smears,

culture, inoculation of hamsters

Oriental sore

(cutaneous

leishmaniasis)

L. tropica

Endothelial cells and lymphoid tissue of skin parasitised. Itching

red papule → scaling → crusted ulcer → ulcer enlargement

→ healing. May be multiple [Incubation period: several days to

months, depending on strain, (1) dry (urban), relatively benign,

slowly ulcerating form; or (2) moist (rural) acute, rapidly

ulcerating zoonotic form]

Ulcer curettings (from margin, not center of

ulcer): Stained smears, culture

American leishmaniasis

(espundia, forest yaws,

uta; mucocutaneous

leishmaniasis)

L. braziliensis

Initial ulcers similar to oriental sore, but this enlarges,

producing weeping ‘saucer’ ulceration. Destructive and

deforming secondary lesions occur at mucocutaneous

junctions, particularly of nasopharynx. Produces fever, pain,

malaise, and anemia (Incubation period: indeterminate). Initial

lesion—few days, complications—months to years. Nutrition

probably very important in severity

Ulcer curettings (from margin not center, of

smear): Stained smears, culture

Sleeping sickness West

African (Trypanosoma

gambiense) East

African (Trypanosoma

rhodesiense)

Local lesion at fly bite followed by fever, adenitis, rash,

transitory edemas. May fulminate (T. rhodesiense) or go on

to meningoencephalitis and meningomyelitis, with mental and

physical wasting leading to coma and death

(T. gambiense). (Incubation period: T. gambiense, 1–3 weeks;

T. rhodesiense, 1–2 weeks.)

Blood: Thick and thin smears, concentration,

culture. Spinal fluid sediment smears. Lymph

node fluid: Smears and culture

Chagas’ disease T. cruzi Acute, usually in children: Febrile illness with generalized

adenopathy lasting a few months; placental infection common.

Chronic cardiac involvement, particularly of right ventricle,

consisting of degeneration of cardiac muscle. Patient seldom

lives beyond age 50. Megacolon or megaesophagus a sequel.

Anemia. Romana’s sign (palpebral edema) most probably an

allergy to insect bite (Incubation period: 1 to 2 weeks)

Blood: Thick and thin smears only in initial

phases. Culture. Xenodiagnosis. Complement

fixation most reliable serologic test

* Direct blood film stain positive except in heavy infections; buffy coat smear or culture better.*

Medical Parasitology 147

Leishmaniasis

148 Concise Book of Medical Laboratory Technology: Methods and Interpretations Visceral Leishmaniasis (Kala-Azar) Caused by Leishmania donovani

Medical Parasitology 149

Cutaneous Leishmaniasis (Oriental Sore, Chiclero’s Disease, Uta, etc.) Caused by Leishmania tropica

150 Concise Book of Medical Laboratory Technology: Methods and Interpretations Trypanosomiases: African Type: Sleeping Sickness

Contd...

Medical Parasitology 151

Contd...

152 Concise Book of Medical Laboratory Technology: Methods and Interpretations Trypanosomiasis South American Type: Chagas’ Disease

Contd...

Medical Parasitology 153

Contd...

154 Concise Book of Medical Laboratory Technology: Methods and Interpretations Common Intestinal Roundworms of Man—Pathology (Table 8.5)

TABLE 8.5: Common intestinal roundworms of man—pathology

Disease and etiology Clinical features Laboratory diagnosis

Enterobiasis

Pinworm infection

Enterobius vermicularis

Symptomless to perianal itching and irritation. Vaginal itch when female

worms leave anus and enter genital passage. Nervousness, insomnia

in persistent or heavy infection, especially from biting finger-nails after

scratching infected rectal area

Cellulose (Scotch) tape swab

Trichuriasis

Trichuris trichiura

Depend on worm load. Symptomless to chronic debilitating diarrhea and

anemia, with damage to physical and mental development. Lower right

quadrant pain is quite a common complaint. Chronic diarrhea, bloody

stools, and tenesmus in heavier infections. Weight loss, wasting, rectal

prolapse in massive trichuriasis, especially in children. Worms visible

attached to mucosa under sigmoidoscopy in heavy infections, mucosa

hyperemic, friable, edematous, stools are mucoid and sticky with sreaks

of blood, numerous Charcot-Leyden crystals, eosinophils, trichuris eggs

Feces: Direct smear,

concentration

Ascariasis

Ascaris lumbricoides

Larvae (migratory phase): Rarely pneumonitis with cough, hemoptysis,

hemorrhages, lung consolidation, focal eosinophilic inflammation.

Eosinophilia (usually under 30%) during larval migration, falls rapidly

afterwards. Adults (intestinal phase): Symptomless to serious intestinal

mechanical complications (pancreatitis, appendicitis, diverticulitis)

especially after disturbance of worms causing obstruction or perforation;

metabolic complication (malabsorption, nutritive drain). Nausea,

vomiting, aggravation of malnutrition

Feces: Direct smear,

concentration

Hookworm infection

Ancylostoma duodenale

Necator americanus

Larvae (migratory phase): Intense skin invasion may produce “ground

itch”, pruritic vesicular lesions followed by lung reactions (less intense

than in ascariasis); cough, tracheal irritation, eosinophilia. Nausea,

vomiting, dyspnea may result from larvae of Ancylostoma (Wakana

disease in Japan)

Feces: Direct standardized

smear to count eggs or

examine after concentration,

cultivation of feces on filter

paper strips in test tubes

(Harada-Mori technique)

Adults (intestinal phase): Hypochromic, microcytic anemia is the chief

clinical feature, varies with intensity and duration of infection, iron intake

nutritive state, age and condition of patient. Hypoproteinemia, edema,

trophic skin disorders, growth reduction, and mental retardation may

follow. Allergic urticaria, diarrhea, abdominal pain in heavy infections.

Intestinal malfunction through malabsorption and possible metabolic

disturbance probably of significant importance, particularly in children

and undernourished populations

Strongyloidiasis

Strongyloides stercoralis

with larvae in focal lesions

Larvae: Invasion of skin may cause “ground itch,” similar to hookworm.

Malaise and cough, pulmonary infiltration may occur; high eosinophilia in

colon, abdominal lymph nodes, liver, lungs following autoreinfection

Feces: Larvae (not eggs) in

direct smear, concentration.

Cultivation of feces on filter

paper strips in test tubes

technique)

(Harada-Mori) Adults: Alternate diarrhea and constipation; inflammation of intestinal

mucosa; may be hemorrhage and microulceration with watery, mucoid

diarrhea, colicky abdominal pain, tenderness, flatulence. Heavier.

infections produce atrophy of mucosa, ulcerous enteritis, edema, and

fibrosis of intestinal wall. Extreme cases (usually after autoreinfection)

with rapid deterioration, asthenia, anorexia, and death or chronic

invalidism. Intestinal malfunction with impaired protein digestion and fat

absorption may produce a condition similar to sprue

Medical Parasitology 155

Extraintestinal Roundworm Infection of Man—Larval Worm Pathology (Table 8.6)

TABLE 8.6: Extraintestinal roundworm infections of man—larval worm pathology

Disease and etiology Clinical features Laboratory diagnosis

Trichinosis

Trichinella spiralis

Adults (intestinal phase): Irritate and inflame the intestinal

mucosa, vomiting, diarrhea, pain

Larval migration and penetration (1–6 weeks after infection):

Muscular rheumatic pains, edema of the eyes, face and

hands. Irregular persistent sweating and fever; difficulty

with breathing, swallowing, and speech; rash and high

eosinophilia (50–90%)

Larval encystment (muscle phase) (after 6 weeks): Cachexia,

toxic edema, skin eruptions, anemia, dehydration, and

gradual subsidence of muscular pains. Fatalities usually

occur 4–6 weeks after ingestion of heavily infected pork

by nonimmune individuals. Using a home-butchered hog

implicated

Biopsy material: Examination by

compression of tissue between glass slides

or by digestion.

Intradermal test, complement fixation,

bentonite flocculation and latex agglutination

tests

Cutaneous larva migrans

Ancylostoma braziliense

and other non-human

hookworms, species of

animal Strongyloides,

Gnathostoma spinigerum,

and possibly other

nematodes

Intracutaneous violently itching, serpiginous tunnels, which

are caused by wandering of hookworm larvae unable to

complete normal penetration, migration, and development.

Worms move about in the area of initial penetration, producing

irregular papulovesicular lesions. Dry crust may form with

local eosinophilia and cellular infiltration. This condition usually

is transitory but larvae may also penetrate to deeper tissues;

produce pulmonary infiltration and be recovered in sputum.

The larvae may last several weeks to months, moving at

intermittent periods of 1–3 cm/day

Clinical signs sufficient. No worms identified

except in experimental animals

Visceral larva migrans:

Toxocara canis, T. cati (dog,

cat ascarids); also

Ancylostoma caninum,

A. braziliense, Capillaria

hepatica, possibly Ascaris

lumbricoides var suum

and filariae of the genus

Dirofilaria, other animal

nematodes

Chiefly in children aged 1–4, often benign, asymptomatic;

later there may develop 20–90% eosinophilia and

hepatomegaly. Fever, cough, joint and muscle pains,

anorexia, weight loss, nervousness, abdominal pain,

pneumonitis, splenomegaly all reported. Symptoms vary

with number and location of larvae and patient’s allergic

response. Chief result of wandering of larvae is indication of

a series of focal eosinophilic inflammations succeeded by

granulomatous reactions. Endophthalmitis reported in young

adolescents who apparently harbored larvae in their tissues

from childhood

Heavy infections show larvae and

eosinophilic granulomatous lesions in

liver biopsy. Chiefly a clinical diagnosis

(persistent eosinophilia, hepatomegaly,

hyperglobulinemia and frequent

pneumonitis); hemagglutination technique

useful for confirmation

156 Concise Book of Medical Laboratory Technology: Methods and Interpretations Plasmid Nematodes

Hookworms

Medical Parasitology 157

Enterobius vermicularis (Thread, Pin or Seat Worm)

Synonym: Oxyuris vermicularis

158 Concise Book of Medical Laboratory Technology: Methods and Interpretations Enterobius vermicularis

Medical Parasitology 159

Ascaris lumbricoides (The Roundworm)

160 Concise Book of Medical Laboratory Technology: Methods and Interpretations The Hookworms

Medical Parasitology 161

Tissue Roundworms of Man, Chiefly Filariae (Tables 8.7 and 8.8)

Parasite and

distribution

Intermediate host Mode of human

infection

Site of worm

maturation

Larvae found in Exit Larval

development in

Reservoir host

Wuchereria

bancrofti

Brugia malayi

Tropics and

subtropics

Culex, aedes,

anopheles,

Mansonia, and

other mosquitoes

Filariform larvae

actively leave

mosquito at time

of biting, usually

enter skin via

puncture

In lymph vessels and

nodes

Bloodstream (nocturnal

periodicity)* certain strains

sub- or non-periodic

Microfilariae

taken up by

insect when

biting

Thoracic muscles;

larvae migrate to

proboscis (8–15

days)

For B. malayi—

cats, dogs

monkeys

Loa loa

Tropical Africa

Chrysops (deer

or mangrove

flies)

Probably same In subcutaneous

tissues

Bloodstream (diurnal

periodicity)

Same Abdomen,

larvae migrate to

proboscis

Primates?

Onchocerca

volvulus

Tropical Africa

Venezuela, and

mountainous

portions of

Central Africa

Simulium

(buffalo gnat)

Probably same Same, host reaction,

produces nodule

around cluster of adults

Subcutaneous tissue; eye

(no periodicity)

Same Thoracic muscles;

larvae do not

concentrate in

proboscis

Man

Dracunculus

medinensis

Africa, India, Far

and Middle East,

Indonesia

Cyclops

(water flea)

Infected cyclops

accidentally

ingested in water

Digested out of

cyclops, then worm

migrates into tissues;

mature female passes

to skin (may be 1 m

long)

Adult female in skin causes

host to form blister near

head of worm. Blister then

filled with larvae, bursts

when skin immersed in

water, discharging larvae.

New blister later forms as

female moves to new site

Cyclops feeds

on larva, which

penetrates gut,

develops in

hemocoel (18–21

days)

Man

*Periodicity of microfilarial appearance in peripheral blood. May be nocturnal in circulating blood from 8 pm, after which microfilariae confined to pulmonary capillaries

TABLE 8.7: Tissue roundworms of man—chiefly filariae, life cycle

162 Concise Book of Medical Laboratory Technology: Methods and Interpretations TABLE 8.8: Tissue roundworms of man—chiefly filariae, pathology Disease and etiology Clinical features Laboratory diagnosis Bancroft’s filariasis W. bancrofti Malayan filariasis B. malayi Filariae in afferent lymph nodes (of lower extremities, male genitalia, vulva, mammary gland) may cause inflammation followed by intensely fibrotic reaction involving whole area in a mass of scar tissue. Pain, fever, chills, toxemia, eosinophilia. Chronic stage (after disappearance of microfilariae) varies from microscopic lesion to lymph varicosity to marked elephantiasis. High eosinophilia and superficial lymphadenopathy in Malayan filariasis. Pathology probably a general and focal sensitization response Blood: Thick and thin smears, concentration. Intradermal test gives useful group filaria reaction, indirect hemagglutination, fluorescent antibody tests Loiasis Loa loa Fugitive swelling (“Calabar swelling”) in skin due to local edema and skin reaction against migrating adult worm. The latter commonly moves across surface of eyeball or under skin at bridge of nose (best times for removal with local anesthesia). Eosinophilia with occasional proteinuria produced Microfilariae in nodule aspirate or skin snip; repeated skin snips may be required; scapular cutaneous region area of choice, manifestations: eosinophilia ocular lesions, pruritus may follow diethylcarbamazine (Hetrazan) therapy Onchocerciasis O. volvulus Small cutaneous fibrous skin nodules with filariae entwined in center. Microfilariae in nodule, in neighboring tissue, or in normal skin far from nodules, rarely in blood. Skin reactions particulary common in Africa; reduction of elastic fibers, depigmentation, progressive thickening, pruritus, papulovesicular lesions or hyperkeratotic patches with microfilariae in scrapings. Eosinophilia and transient urticaria during incubation. Ocular involvement leading to blindness, a common result of prolonged infection. Conjunctiva and vitreous humor with numerous microfilariae. Pathology due to mechanical action, toxins, hypersensitive response of patient; ocular symptoms after 7–9 years Dracontiasis D. medinensis Asymptomatic until reddish papular lesion appears, usually on legs. Lesion forms blister bearing head of female worm and numerous larvae. Blister bursts when immersed in water, releasing larvae. Urticaria, pruritus, allergic symptoms, eosinophilia. Accidental rupture of worm may produce intense inflammatory reaction with secondary infection Local lesion with head of worm and larvae in blister X-ray reveals calcified worm; reflected light shows worm under skin. Intradermal test Eosinophilic lung describes a host allergic response to migration of microfilariae that are trapped in lungs, producing an allergic, asthma-like response. Probably, caused by human filariae or closely related species,