Parasitology Lecture for MSKL Parasitology Unit Learning Objectives ( 1 ) To understand the main parasites that cause infection of the integumentary and musculoskeletal systems, as regard their names and clinical significance ( 2 ) To understand the following parasites as pathogens of the integumentary and musculoskeletal systems, as regard description of their structure, life cycle, pathogenesis, and laboratory diagnosis ( A ) Leishmania tropica ( B ) Onchocerca volvulus ( C ) Trichinella spiralis ( D ) Sarcocystis ( 3 ) To understand the following parasites as skin pathogens, as regard outline of their structure, life cycle, pathogenesis, and laboratory diagnosis ( A ) Sarcoptes scabiei ( B ) Pediculus humanus ( C ) Phthirus pubis 1

Main parasites  infection of Skin, Muscle, Bone ( 1 ) Leishmania tropica Clinical Significance : Skin ulcer ( Cutaneous Leishmaniasis ) ( 2 ) Dermatobia hominis larva Clinical Significance : Skin ulcer ( Cutaneous Myiasis ) ( 3 ) Onchocerca volvulus Clinical Significance : Skin nodules ( 4 ) Trichinella spiralis Clinical Significance : Muscle pain ( 5 ) Sarcoptes scabiei Clinical Significance : Skin rash and itch ( 6 ) Pediculus humanus Clinical Significance : Skin itch ( 7 ) Phthirus pubis Clinical Significance : Skin itch ( 8 ) Echinococcus ( Hydatid Cyst ) Clinical Significance : Bone hydatid cyst  bone pain 2

Leishmania tropica Structure : ( Amastigote stage ) Size : 3 um Shape : Oval Life Cycle : When Sand Fly bites man it injects promastigote stage into skin ( this stage is found only in the Sand Fly and in the Culture Medium. It is not found in skin lesion of man )  macrophage takes promastigote  develop into amastigote stage which multiply  macrophage rupture  release amastigotes  taken by Sand Fly  bite other man to complete the life cycle Pathogenesis : Multiplication of amastigotes inside macrophages is followed by rupture and release of numerous amastigotes in subcutaneous tissue. The body inflammatory reactions around amastigotes  granuloma  ischaemic ulcer Laboratory diagnosis : ( 1 ) Microscopy Method ( sample is smear from skin ulcer, examined for amastigote stage ) ( 2 ) Culture Method ( 3 ) Serology Method ( 4 ) Molecular Method 3

Right Upper : Leishmania skin ulcers Right Lower : Amastigote ( small oval bodies ) Left Upper : Animal host Left Lower : Sand Fly environment Copyright : Dr M Al Sagayer, Riyadh, KSA 4

On chocerca volvulus Structure : ( Microfilaria stage ) Size : 300 um long Shape : round, no sheath Life cycle : Black Fly injects microfilaria into skin  develop to male and female adult worms  produce more microfilaria in subcutaneous tissue  taken by Black Fly  bite other man to complete the life cycle Pathogenesis : Microfilaria migrate in subcutaneous tissue  Body inflammatory reactions around microfilaria & adult worms  nodule formation Laboratory Diagnosis : (1) Microscopy Method ( sample is skin snip examined for microfilaria stage ) 5

Onchocerca skin nodule ( From : ) Onchocerca microfilaria ( From : ) 6

Trichinella spiralis, Sarcocystis Trichinella spiralis Structure : ( encysted larva ) Size : 0.1 mm Shape : round, like coil Life cycle : Encysted larva in pig muscle  taken by man or animal  adult in intestine  produce more larva  via blood  muscles Pathogenesis : migrating larva cause allergic reactions and oedema, encysted larva in muscle causes allergic reactions and pain Laboratory diagnosis ( 1 ) Microscopy Method ( 2 ) Serology Method Sarcocystis This is a rare parasitic muscle infection in humans. Sarcocystis infection occur mainly in animals eg sheep, pigs. Man is an accidental intermediate host. Sarcocystis infection in man may cause myositis. 7

Right photograph : Dermatobia hominis larva Left photograph : Cutaneous myiasis ulcer Copyright : Akhtar J, Qadri M, Abdelmageed Imam. Saudi Medical Journal, 2000, Volume 21 ( 7 ), Pages 689 – 691 8

Sarcoptes scabiei, Pediculus humanus, Phthirus pubis Sarcoptes scabiei Structure : ( adult stage ) Size : 0.3 mm Shape : oval Life cycle : Egg  hatch larva  develop to adult ( cycle is completed under the skin ) Pathogenesis : Female adult burrow into skin  lay eggs  itch Laboratory diagnosis : Microscopy method Pediculus humanus Structure : ( adult stage ) Size : 2 mm Shape : oval Life cycle : Egg  hatch nymph  develop to adult Pathogenesis : Adult bite  itch Laboratory diagnosis : Microscopy method Phthirus pubis Structure : ( adult stage ) Size : 1 mm Shape : oval Pathogenesis : Adult bite  itch Laboratory diagnosis : Microscopy method 9

Sarcoptes skin rash ( From : ) Sarcoptes parasite ( From : ) 10

Good Parasitology References ( 1 ) Tropical Medicine & Parasitology W Peters & G Pasvol, 5 th edition, 2005 Mosby Publishers, US. Note : 7 copies of this reference are available in Qassim University Library. ( 2 ) Parasitic Diseases Division, CDC ( US ) 11