Parasitic infections

Parasitic Infections of Skin, Soft
Tissue and Musculoskeletal
System

Essentials of Medical Microbiology by Apurba S Sastry © Jaypee Brothers Medical Publishers
Learning objectives
2
At the end of the session, the students will be able to understand:
▰ Life cycle, pathogenesis, clinical features, lab diagnosis, treatment and
prevention of cutaneous leishmaniasis, cutaneous filariasis, Dracunculiasis,
trichinellosis, cutaneous larva migrans.

Parasitic infections of skin, soft tissue and
musculoskeletal system
3
Protozoan infections
 Cutaneous leishmaniasis
 Cutaneous amoebiasis
 Acanthamoeba skin lesions
 Trypanosoma chancre and chagoma
 Sarcocystosis
Cestode infections
 Muscular cysticercosis
 Sparganosis (Spirometra)
Trematode infections
 Cercarial dermatitis
 Cutaneous paragonimiasis
Nematode infections
 Cutaneous filariasis
 Dracunculiasis
 Trichinellosis
 Cutaneous larva migrans

CUTANEOUS LEISHMANIASIS
5
▰ CL: Cutaneous leishmaniasis (CL) - most common form of leishmaniasis.
▰ Global annual incidence of 6-10 lakh new cases.
▰ About 95% of CL cases - America, the Mediterranean basin, the Middle East
and Central Asia

CUTANEOUS LEISHMANIASIS (Cont..)
6
▰ MCL: Over 90% of mucocutaneous leishmaniasis (MCL) cases - Bolivia, Brazil,
Ethiopia and Peru.
▰ Post kala-azar dermal leishmaniasis (PKDL) - another cutaneous
manifestation - occurs few months to years following VL

Various agents of cutaneous leishmaniasis
7
Species Geographical
distribution
Clinicalsyndrome Vector (sandfly) Reservoir Transmission
L. L. tropica
(Oriental sore)
Western India, North
Africa, and Middle
East
CL, LR Phlebotomus
sergenti
Humans Anthroponotic
(human)
L. L. aethiopica Ethiopia, Uganda,
and Kenya
CL, DCL P. longipes Hyraxes Zoonotic
L. L. major Middle East, India,
China, Africa, Central
and Western Asia
CL P. papatasi Rodents Zoonotic

Old World Cutaneous Leishmaniasis (CL)
8
▰ Old world CL is caused by Leishmania tropica complex - comprises of three
species—L. tropica, L. aethiopica and L. major.
▰ Vary from each other in - geographical distribution, reservoir (human or
animal) and species of sandfly vector involved in transmission and the type of
cutaneous lesions produced.

Life Cycle
9
Life cycle of the L. tropica complex is same
as L. donovani , except that:
 Vector: Sandfly, but different species of
Phlebotomus.
 Habitat: In humans, the amastigote forms
reside in reticuloendothelial cells of skin
(they do not migrate to viscera).

Clinical Features
10
▰ Cutaneous leishmaniasis: Also known as “Oriental
sore”, Delhi boil, Aleppo boil and Baghdad Button, etc.
▰ Occurs on face and hands – painless papule, becomes
nodular and finally it ulcerates.
▰ Heals spontaneously or - leaves behind disfigurement
or scar.

Clinical Features (Cont..)
11
▰ Leishmaniasis recidivans (LR): Granulomatous
response producing new lesions - occur years after
healing of primary sore due to L. tropica. It is
▰ Characterized by scaly, erythematous papules and
nodules - develop in center or periphery of a
previously healed sore.

Clinical Features (Cont..)
12
▰ Diffuse cutaneous leishmaniasis (DCL): Caused by L. aethiopica. It is
▰ Characterized by - lack of CMI response to the parasite, resulting in
widespread cutaneous lesions
▰ Rare -100 cases have been reported so far - Kenya and Ethiopia
▰ Responds poorly to treatment; disease may last long.

Laboratory Diagnosis of CL
13
▰ Microscopy: Amastigotes - demonstrated from punch biopsies - from the
edge of the active lesion and touch preparation (impression smear) stained
with Giemsa
▰ Culture: Aspiration from the ulcers - cultured in NNN medium and Schneider’s
Drosophila medium - isolation of promastigote forms

Laboratory Diagnosis of CL (Cont..)
14
▰ Montenegro test: Positive leishmanin skin test - delayed hypersensitivity
reaction to the parasite.
▰ Negative in diffuse CL.

Treatment of Cutaneous Leishmaniasis (Old
World)
15
▰ Local therapy - usually recommended. Options available are:
 (i) paromomycin (15%) or methyl benzethonium (12%) ointment - 20 days
 (ii) intralesional antimonials
 (iii) cryotherapy
 (iv) thermotherapy.

Treatment of Cutaneous Leishmaniasis (Old
World) (Cont..)
16
▰ Systemic therapy: Only for disfiguring or scarring lesions.
 L. major—(i) fluconazole for 6 weeks, (ii) pentavalent antimonials with or
without pentoxifylline for 10–20 days
 L. tropica—pentavalent antimonials for 10–20 days. In LR cases -
combined with oral allopurinol
 L. aethiopica—pentavalent antimonials + paramomycin for 60 days or
longer.

New World Cutaneous Leishmaniasis
17
▰ Mainly caused by:
 Leishmania Leishmania (L.L.) mexicana complex
 Leishmania Viannia (L.V.) braziliensis complex
 Leishmania Leishmania (L.L.) chagasi - Causes atypical CL and American
VL.

New World Cutaneous Leishmaniasis (Cont..)
18
▰ Morphology and life cycle - identical to L.
donovani, except:
▰ Vector: Lutzomyia species
▰ Reservoir of infection: Dogs, foxes (zoonotic)
▰ Amastigote forms - reside in reticuloendothelial
cells of skin and mucous membrane (do not
invade viscera).

Leishmania Leishmania mexicana complex and
Leishmania Viannia braziliensis complex
19
Leishmania Leishmania mexicana complex Leishmania Viannia braziliensis complex
Species Geographical
distribution
Clinical syndrome Species Geographical
distribution
Clinical syndrome
L. L. mexicana Central America
and
northern parts of
South
America (the
Amazon
basin)
CL (chiclero ulcer)
DCL
L. V. braziliensis Brazil CL, MCL (espundia),
LR (rare)
L. L. amazonensis CL, DCL and VL
(rare)
L. V. panamensis Panama,
Colombia
CL, MCL
L. L. venezuelensis
L. L.garnhami
CL L.V. guyanensis Guyana CL(forest yaws),
MCL
L. L. pifanoi CL, DCL L. V. peruviana Peru CL(Uta), MCL
Reservoir: Forest rodents, marsupial and humans Reservoir: Dogs, foxes, forest rodents and humans
Vector: Lutzomyia species and Transmission: Zoonotic (for both complexes)

Chiclero ulcer
20
▰ L. mexicana causes - specific form of CL - chiclero ulcer (or bay sore).
▰ Characterized by persistent ulcerations in pinna.
▰ Seen in Central America - workers living in forests harvesting chicle plants to
collect chewing gum latex.

Espundia (mucocutaneous leishmaniasis or MCL)
21
▰ L. braziliensis infects mucous membrane of the
nose, oral cavity, pharynx or larynx.
▰ Presents months to years after the CL.
▰ Ulcerative lesions - formed with erosion of the soft
tissue and the cartilages - loss of lips, soft part of
nose and soft palate

Espundia (mucocutaneous leishmaniasis or MCL)
(Cont..)
22
▰ Gradually, the nasal septum - destroyed, resulting in nasal collapse with
hypertrophy of upper lip and nose leading to development of “tapir nose”.

Treatment New World cutaneous leishmaniasis
23
▰ In contrast to Old World CL - systemic therapy – recommended for New World
CL - as lesions are more chronic, multiple and have tendency for mucosal
involvement.
▰ Local therapy - given in addition - agents used for treatment - same as used
for Old World CL

(Cont..)
24
▰ The regimen for systemic therapy depends upon - causative agent.
 L. mexicana: Ketoconazole or miltefosine for 28 days
 L. braziliensis: Pentavalent antimonials for 20 days; or amphotericin B

(Cont..)
25
 Relapse treatment: Amphotericin B or pentavalent antimonials + topical
imiquimod.

(Cont..)
26
▰ For MCL (all species):
 (i) pentavalent antimonials with or without oral pentoxifylline for 30 days
 (ii) amphotericin B
 (iii) Bolivia - miltefosine - agent of choice.

CUTANEOUS FILARIASIS
28
▰ Filarial nematodes - Wuchereria and Brugia cause lymphatic filariasis
▰ Many other filarial nematodes - reside in skin and subcutaneous tissue -
several cutaneous manifestations—Loa loa, Onchocerca volvulus, and
Mansonella species.

Loa loa
29
▰ Also called - African eye worm.
▰ Cause infection of subcutaneous tissue and eyes.
▰ Infection - restricted to West and Central Africa.

Life Cycle
30
▰ Similar to- W. bancrofti except for the vector - female Chrysops species (deer
flies, or tabanid flies).
▰ Following mosquito bite (during day time) - L3 larvae - transmitted to man and
transform into adult worms - migrate to subcutaneous tissues and eyes
▰ Microfilariae - from gravid female worms migrate to blood - exhibit diurnal
periodicity.

Clinical Features
31
▰ Calabar swellings: Most common form of loiasis - called fugitive swelling -
subcutaneous swelling developing on the extremities (knee or wrist).
▰ Ocular manifestations - conjunctival granuloma, edema of the eye lid.
▰ Complications: Meningoencephalitis, nephropathy and cardiomyopathy

Laboratory Diagnosis
32
▰ Peripheral blood smear examination reveals - characteristic microfilariae.
 Microfilaria shows diurnal periodicity - blood collected in day time between
10 am to 3 pm
 Sheathed, measure 275 (250–300) μm long and bear a column of nuclei
extending till the tail tip
 Adult worms - isolated from the eye or biopsy of the subcutaneous swelling.

Laboratory Diagnosis (Cont..)
33
▰ Other methods include—
 (1) molecular method - nested PCR-based assays for the detection of specific
DNA, and
 (2) antibody detection: Lateral flow assay (ICT) - detects antibodies to Ll-SXP-
1 antigen.

Treatment of Loiasis
34
▰ Diethylcarbamazine (DEC) - drug of choice—multiple courses - necessary to
resolve loiasis completely
▰ Glucocorticoids: Required in heavy microfilaremia - reduce inflammatory
reactions against microfilariae - preventing neurological complications

Treatment of Loiasis (Cont..)
35
▰ Albendazole or ivermectin - effective in reducing microfilarial loads –
ivermectin- contraindicated in heavily infected patients with loiasis
▰ Surgical removal of the adult worms - rarely required if they migrate through
the bridge of the nose or through the conjunctiva.

Onchocerca volvulus
36
▰ Causative agent of “river blindness” in man.
▰ Endemic in West Africa and also in South and Central America.

Life Cycle
37
▰ Life cycle - similar to - W. bancrofti, except the vector is Simulium (black flies).
▰ Following the bite of black flies - L3 larvae - transmitted to man and transform
into adult worms - migrate to subcutaneous tissues and eyes
▰ Gravid female worms release microfilariae - migrate to the blood - infective to
the black flies.

Clinical Features
38
▰ Skin (Dermatitis)
 Leopard skin
 Sowda
▰ Onchocercoma
▰ Ocular lesions
▰ Lymphadenopathy

39
Detection of the Parasite:
▰ In a skin snip smear - gold standard method for diagnosis of onchocerciasis.
▰ Microfilariae - found either in the skin (90%) or in the nodules (10%).

40
▰ Microfilariae: Measure 254 μm long, pointed tail tip without any nuclei -
unsheathed and nonperiodic.
▰ Adult worms - detected from the biopsy of the subcutaneous nodules - less
sensitive

41
▰ Other Methods:
 Serology
 Molecular methods
 Mazzotti skin test

Treatment of Onchocerciasis
42
▰ Ivermectin - drug of choice for onchocerciasis.
▰ Active against the microfilariae but not against the adult worms
▰ Given orally in a single dose of 150 μg/kg - yearly or biannually.
▰ Contraindicated - areas of Africa co-endemic for O. volvulus and L. loa.
▰ Surgical excision - recommended when nodules are located on the head.

Mansonella Species
43
▰ Named after Patric Manson.
▰ Rarely infect humans - either nonpathogenic or asymptomatic in most of the
individuals.

Mansonella perstans
44
▰ Transmission: By Culicoides (midges).
▰ Adult worms reside in serous cavities, mesentery and perirenal tissues.
▰ Microfilariae circulate in – blood without periodicity
▰ Clinical features: Nonpathogenic – occasionally cause - angioedema, urticaria,
pruritus and calbar-like swelling - also produces acute periorbital
inflammation - bung-eye or bulge-eye

Mansonella perstans (Cont..)
45
▰ Laboratory diagnosis: Microfilariae in peripheral blood are nonperiodic,
nonsheathed, measures 195 μm long - straight tail and blunt end.
▰ Body nuclei - extended till the tail tip
▰ Treatment: DEC or albendazole.

Mansonella streptocerca
46
▰ Transmission: Biting midges (Culicoides grahami)
▰ Clinical feature: Asymptomatic - some people develop - inguinal
lymphadenopathy, pruritus, dermatitis with hypopigmented macule - no
sensory loss

Mansonella streptocerca (Cont..)
47
▰ Laboratory diagnosis: Detection of the characteristic microfilariae in skin
snips - nonperiodic, nonsheathed, measures 210 μm with a curved tail (looks
like Shepherd’s crook). Nuclei - extended till the blunt tail tip
▰ Treatment: DEC - effective for streptocerciasis.

Dirofilaria Species
48
▰ Parasites of lower animals.
▰ Humans - unusual hosts.
▰ Parasite undergoes - incomplete development in humans either in the lungs,
eyes and or subcutaneous tissue, producing various lesions.
▰ Man acquires infection by the bite of mosquito (Aedes, Culex, Anopheles, or
Mansonia) containing L3 filariform larvae.

Prevention of Cutaneous Filariasis
49
▰ Vector control - useful in highly endemic areas.
▰ Insecticide spraying - destroy the breeding sites.
▰ Mass administration of ivermectin every 6–12 months is being used to
interrupt the transmission in endemic areas.

DRACUNCULIASIS
51
▰ It is a parasitic infection by the somatic nematode - Dracunculus medinensis.
▰ Also called as Guinea worm disease or dracunculiasis, characterized by
cutaneous blisters.

Epidemiology
52
▰ Crippling parasitic disease on the verge of eradication,
▰ Currently endemic to only to 3-4 countries in Sub-Saharan Africa.
▰ About 187 countries including India - already declared free of transmission.
▰ In 2019, only 54 human cases reported in 2019.

Life Cycle
53

Pathogenesis and Clinical Features
54
▰ Signs and symptoms appear - 1 year after the
infection - when gravid adult female worm
emerges near the surface of the skin.
▰ Characterized by painful blister from which the
female worm emerges, accompanied by local
erythema, fever, nausea and pruritus
A B

Pathogenesis and Clinical Features (Cont..)
55
▰ Most common sites—lower leg, ankle and foot
▰ Secondary bacterial infections - occur at the bister site.

56
Detection of adult worm:
▰ Possible when the gravid female worms
appear in the blisters.
▰ Calcified adult worms from the deeper
tissue - detected by X-ray
A B

57
▰ Detection of L1 larvae: When the leg with ulcer is placed in a container with
cold water - large number of motile larvae - discharged - examined under the
microscope
▰ Antibody detection: Antibodies to D. medinensis - detected by ELISA
▰ Peripheral blood Eosinophilia.

Treatment of Dracunculiasis
58
Worm removal:
▰ Slowly and gently extracted over a period of 15–20 days using a small stick
and wounding out daily with small traction.
▰ Heavy pressure – avoided because breaking the worm - lead to allergic
reactions and secondary bacterial infection.

Treatment of Dracunculiasis (Cont..)
59
Symptomatic treatment:
▰ Application of wet compresses to the affected skin, administration of
analgesics and prevention of secondary bacterial infection by the use of
topical antibiotics.
▰ No anti-helminthic drugs known to be effective against D. medinensis.

Reasons for Eradication from India
60
▰ The national Guinea worm eradication program - launched in 1984 with
technical assistance from World Health Organization (WHO).
▰ Provision of safe drinking water
▰ Cyclops control: Killing copepods in sources of drinking water by application
of abate (temephos) larvicide

Reasons for Eradication from India (Cont..)
61
▰ Provision of clean drinking water from boreholes or wells (was a major source
of infection)
▰ Health education about boiling or filtering of drinking water
▰ Treatment of cases.

TRICHINELLOSIS
63
▰ Trichinella spiralis causes trichinellosis (or trichinosis) - zoonotic infection
acquired from domestic pigs or other carnivores.

Morphology
64
▰ Like other somatic nematodes, it has an adult worm (1.5– 3 mm long), and
four stages of larvae.
▰ No egg stage.
▰ L1 larva - infective form - forms cysts in muscles.

Life Cycle
65

Larva of Trichinella liberated from bear meat
66

Pathogenicity and Clinical Features
67
▰ Clinical symptoms - depend on the phase of parasitic invasion.
▰ Intestinal stage: Most of the infections – asymptomatic - heavy load of
parasite - provoke watery diarrhea (most common feature) during the first
week after infection.

Pathogenicity and Clinical Features (Cont..)
68
▰ Larval migration: Symptoms appear in the second week after infection
 Periorbital and facial edema is common
 Hemorrhages in the subconjunctiva, retina and nail beds (“splinter”
hemorrhages)
 Maculopapular rash
 Migration to heart, CNS and lungs - rare.

Pathogenicity and Clinical Features (Cont..)
69
▰ Muscle encystment: Occurs 2–3 weeks after infection.
▰ Common symptoms - myositis with myalgia, muscle edema, and weakness.
▰ Extraocular muscles - common to be involved, followed by biceps, muscles of
the jaw, neck, lower back, and diaphragm.

Laboratory Diagnosis - Demonstration of Larvae
70
▰ Definite diagnosis - demonstration of larvae in muscle biopsy - from
gastrocnemius, deltoid, and biceps.
▰ Direct slide technique: Fresh muscle tissue - compressed between glass
slides and examined under low power microscope

Laboratory Diagnosis - Demonstration of Larvae
(Cont..)
71
▰ Histopathologic examination:
Performed either on fresh muscle
tissues directly or after artificial
digestion of muscle mass by pepsin
Trichinella cysts in the human muscle
biopsy (hemotoxylin and eosin stain).

Laboratory Diagnosis - Antibody Detection
72
▰ ELISA - detecting parasite specific IgG antibody against excretory secretory
antigen of muscle larvae.
▰ Confirms the diagnosis but cannot differentiate past and present infection.
▰ Also cross reacts with other nematodes.

Laboratory Diagnosis - Coproantigen Detection
73
▰ Modified double sandwich ELISA – developed using polyclonal antibodies
raised in rabbit to detect larval somatic antigens in stool.
▰ Detectable from first day of infection up to third week.

Laboratory Diagnosis - Bachman Intradermal Test
74
▰ Intradermal injection of Bachman antigen (prepared from Trichinella larvae) -
immediate induration and erythema.
▰ Becomes positive in 2–3 weeks of infection and persists for life - cannot
differentiate past infection present infection.

Laboratory Diagnosis - Other Tests
75
▰ Blood eosinophilia: Elevated in more than 90% symptomatic patients
▰ Elevated muscle enzymes: Elevated serum creatine phosphokinase
▰ X-ray to detect the calcified muscle cyst.

Treatment of Trichinellosis
76
▰ Mild infection: Symptomatic treatment – with bed rest, antipyretics, and
analgesics.
▰ Moderate infection: Mebendazole and albendazole - active against enteric
stages of the parasite.
▰ Severe infection: Glucocorticoid is added - beneficial for severe myositis and
myocarditis.

Prevention
77
▰ Direct inspection of pork and microscopic examination of small tissue
samples of pig diaphragm before use.
▰ Maintenance of strict standards for freezing, cooking, and curing of pork and
pork products.
▰ All parts of pork muscle tissue - heated to >58.3°C.
▰ Microwaving might not kill the parasite.

CUTANEOUS LARVA MIGRANS
79
▰ Cutaneous larva migrans - skin lesions produced by nematodes of lower
animals, when they accidentally infect man.

Arrested Life Cycle and Pathogenesis
80
▰ Felines - natural hosts.
▰ Humans - abnormal accidental host.
▰ Filariform larva (L3) - infective form present in soil, transmitted by skin
penetration.
Agents:
▰ A. brasiliensis, A. caninum and A. ceylanicum.

(Cont..)
81
▰ Rarely CLM may also be caused by:
▰ Strongyloides stercoralis, Ancylostoma duodenale and Necator americanus
▰ Other nematodes of lower animals - Gnathostoma spinigerum.

(Cont..)
82
In lower animals:
▰ Nematodes when infect lower animals - larvae migrate to various organs (e.g.
intestine) - develop into adult worms -mate to lay eggs (e.g. in feces) and the
cycle continues

(Cont..)
83
▰ In humans: Larvae of these lower animal nematodes - accidentally infect man
- not able to complete their normal development (because humans are the
unusual host for them) and their life cycle gets arrested.
▰ The larvae wander - aimlessly in skin and subcutaneous tissue -cutaneous
larva migrans (CLM) or creeping eruption.

Clinical Features
84
▰ Larvae wander in the superficial layers of the skin and back - linear tracks and
provoke allergic reaction in previously sensitized patients - leads to:
 Ground itch
 Larva currens

85
▰ Diagnosis - made by clinical feature (presence of the linear tracks) and history
of exposure.
▰ Larvae - not detected in skin biopsy.
▰ PCR - detection of larval DNA in human tissues
▰ Elevated eosinophilia - seen in peripheral blood or sputum - Charcot-Leyden
crystals in sputum.

Treatment of Cutaneous larva migrans
86
▰ Oral and topical thiabendazole is effective
▰ Freezing the advancing end of creeping eruption in ethyl chloride is useful.

PARASITIC AGENTS THAT
RARELY CAUSE SSTI
87

PARASITIC AGENTS THAT RARELY CAUSE SSTI
88
▰ Cutaneous amoebiasis
▰ Acanthamoeba skin lesions
▰ Trypanosoma chancre
▰ Chagoma
▰ Muscular sarcocystosis

PARASITIC AGENTS THAT RARELY CAUSE SSTI
(Cont..)
89
▰ Cysticercosis
▰ Sparganosis
▰ Cercarial dermatitis
▰ Cutaneous paragonimiasis

Parasitic infections

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