OSPE

Objective Structured Practical Exam

Total Marks 30Divided as follows:

10 specimens: Slides, jar &/or box

5 specimens : -Identification

-Mention 2 main characteristic features

(20 marks)

(10 marks)

(1 mark each)

Identification only

Slides, jar &/or box

(2 marks each)

(1 mark each)

Time allowed to identify each specimen is one minute

Time allowed to identify each specimen is one minute

Time allowed to write 2 characteristics is another minute

Jars of Trematodes

Adult F.giganticaAdult F.hepatica

Leaf-like flat worm

Lateral borders

are parallel

Lateral borders

are converging

Jars of Trematodes

Adult Fasciola in bile ducts

Liver tissue

A piece of liver infected with Fasciola

Jars of Cestodes

Single Hydatid cyst

Spherical cyst surrounded by fibrous layer

Jars of Cestodes

Hydatid cysts in the liver

Cysts of different sizes in liver tissue

Fibrous tissue lining the cavities

Solitary cyst in the liver tissue

Jars of Cestodes

Hydatid cyst of lung

Lung tissue is consolidated

Solitary cystMultiple cysts

Taenia segments

Jars of Cestodes

Flat segmented worm, tape-like

Some segments are broader than

long, then segments

become squarish then longer than

broad

Jars of Cestodes

Cysticercus bovis in heart muscle

Section of heart showing cysticercus bovis

Piece of heart muscle Slice of heart

muscle

Cysticercus bovis appear as oval body )1X0.5 cm in size(

Cysticercus bovis appear as oval body )1X0.5 cm in size(

Jars of Nematodes

Adult ♀ Ascaris worm

Creamy-white in colour

Cylindrical, about 20 cm long

Adult Ascaris worms

Creamy-white in colour

Cylindrical, about 20 cm long

♀ & ♂Ancylostoma

Cylindrical worms

with bursa

Cylindrical worms with pointed end

Adult Ancylostoma attached to mucosa of small intestine

Jars of Nematodes

Jars for Nematodes

Adult Trichuris trichiura attached to mucosa of caecum

Thin portion of the worms are embedded in

caecal mucosa

Thick portion of the worms are hanging

in the lumen

The worms are whip-like

Jars for Nematodes

Elephantiasis of the skin

Thick, wrinkled skin

Fissured skin

Boxes of Flies

Wohlfahtria Sarcophaga

Abdomen is dotted

In both: Mouth is sucking

In both: Body is composed of head, thorax & abdomen

Abdomen is chess-board

like

Boxes of Flies

Musca domestica

Abdomen with median dark band

In both: Body is composed of head, thorax & abdomenIn both: Mouth is sucking

Lucilia

Metallic green in colour

Fleas

HABITS:

Temporary ectoparasites.

Both sexes are blood suckers.

They are host specific.

Increase in spring and autumn.

Medically Important Fleas

Is a vector of diseases:1- Plague:

Pulex irritans

Human Flea

2- Endemic or murine typhus:

Anterior station

Posterior station

Multiplication of Yersinia

Multiplication in epithelial

cells

caused byYersinia pestis.

caused by Richettsia mooseri.

Mechanism: Propagative transmission

Mode of infection

Skin contamination by flea faeces

Inhalation of dried faeces

Crushing of infected flea

Skin lesions caused by flea bite

Animal Fleas

Dog flea

Intermediate host of parasitic diseases:

I.H. for H.nana and H.diminuta )rat flea(I.H. for D.caninum )dog flea(

Rat fleaCat flea

Infected stool on the ground

Adult ♀flea

Flea egg

H.nana egg

H.diminuta egg

D.caninum egg capsule

Flea larvaFlea pupa Cysticercoid nana

Cysticercoid diminutaCysticercoid caninum

Infected flea

How can fleas transmit infection to man?

Fleas found in animal hairs

Tunga penetrans

In dusty soil

Causes Chigger’s or Jigger’s disease.

Found in South America.

It attacks humans walking bare-footed on dusty soil

Has angular head

Control of Fleas

Human fleas:

Insecticides and vacuum cleaner to clean floors and carpets from eggs and larvae of fleas.

Dog and cat fleas:Dusting animals and their resting places with insecticides.

Rat fleas:Dusting rat holes with insecticides.Using rodenticide )warfarin(.

Strict quarantine measures against ships by fumigation.

Lice Lice infecting man:Pediculus humanus capitis )head louse(.Pediculus humanus corporis )body louse(.Phthirus pubis )pubic louse(.

Habits:Permanent ectoparasites.Spread epidemics of louse-borne diseases.Season: winterTransmitted by combs, brushes, hats and clothes.

Male Female Female Male

Pediculus humanus capitis )head louse(

Cause the following lesions

Adult lice hanging to human hair

Skin lesions from lice bitesLice attach their

eggs to human hair

Body louse is a vector of the following diseases

1- Epidemic typhus: caused by R. prowazekii.

Source of the epidemic:a case of typhusa case of Brill-Zinsser disease

Posterior station

2- Trench fever: caused by R. quintana.

Posterior station

3- Epidemic relapsing fever: caused by B. recurrentis.

Disappear from gut to body

cavity )crushing(gut

Body cavity

Mechanism of disease transmission:

Propagative

)faeces, dried faeces

or crushing)

)faeces or crushing(

A human carrying R.prowazekii in a dormant form for years then disease appeared on him due to depressed immunity

Body louse cause Pediculosis

Also called: vagabond’s disease

Occurs in persons who had lice for long periods

Phthirus pubis )Pubic louse( Found attached to pubic hairs, axillary hair and eye lashes.

Blepharitis )inflammation of lid margin(.Eggs of Phthrirus pubis

Skin becomes thickened & dark coloured

Control of Lice

Boiling the underwear.Shaving pubic and axillary hairs.Removal of lice from eyelashes by forceps and

application of yellow oxide of mercury ointment.

Body louse:Bathing and boiling of clothes.

Head louse: Spraying of hair by synthetic pyrethrum )Licid(.

Pubic louse:

Bed Bugs )Cimex lectularius(

Cimex on bed matress

Female Male

Habits: Temporary ectoparasites.Feed only on blood )Nocturnal feeders(

Give a characteristic odour.

Cimex lectularius )Bed bugs(

Cimex on human skin

Cimex bite on skin

Medical importance:

Persistent biting by night causes insomnia and nervous irritability.

Mechanical carriers of human diseases.

May transmit hepatitis B virus.

Control:

Application of insecticides to hiding places. Fumigation.

Collection and destruction of bugs.

Winged Bugs)Cone-nosed, kissing, Assassin and Barber’s bug(

Vector of Trypanosoma cruzi that causes Chagas’

disease.

Egg

Romana’s sign

larva

nymph

adult

Habits:Temporary ectoparasites.

Nymphs and adults are blood suckers.

Nocturnal feeders.

Attack face with no pain.

Medical Importance:

Mechanism of disease transmission by winged bug T.cruzi in human blood

Epimastigote form

Short stumpy metacyclic

trypanosomes )infective stage(

Amastigote form

Pass out with faeces

Cyclopropagative transmission

Alimentary canal of

bug

A patient presenting with corneal ulcer

a b c

1 -Which of the following parasites can cause corneal ulcer?

E.histolytica trophozoite

Acanthamoeba trophozoite

Trypanosoma cruzi

A patient presenting with corneal ulcer

a b c

2 -Which of the following represents the mode of infection by the

causative protozoa?

Contamination by Triatoma faeces

Use of contaminated contact lens

Flies standing on eyes & face

A patient presenting with corneal ulcer

a b c

3 -How can you confirm your diagnosis?

Corneal scraping to detect the

parasite

CSF examination to detect the

parasite

Sample suspension in fresh water

A patient presenting with swollen eye-lid

1 -Which of the following parasites can cause swollen eye?

a b c

Toxoplasma gondii

trophozoite

Acanthamoeba trophozoite

Trypanosoma cruzi

A patient presenting with swollen eye

a b c

2 -Which of the following represents the mode of infection by the

causative protozoa?

Contamination by Triatoma faeces

Use of contaminated contact lens

Flies standing on eyes & face

A patient presenting with swollen eye

a b c

3 -How can you confirm your diagnosis?

Corneal scraping to detect the

parasite

Blood film examination

Sample suspension in fresh water