1st year DDS: Practical class 1

Argas reflexus

(pigeon tick)

Host: birds, and sometimes mammals (including human).

Life cycle: eggs, larvae (6 legs), nymph (8 legs), adult (8 legs).

Site of infection: skin.

Geographical distribution: endemic (Europe).

Symptoms:
• severe painful itching of reddish swellings on skin, purulent inflammation of the skin, purple papules with necrosis in the center of the lesion and often oozing with serum fluid.

• in allergic persons: severe allergic reactions, including dyspnea.

• wounds that do not heal easily (even 1,5 year). Scars, which can occur due to strong immunological reactions or bacterial superinfections.

Ixodes sp.

(tick)

Host: mammals (including human), birds and reptiles.

Life cycle: eggs, larvae (6 legs), nymph (8 legs), adult (8 legs).

Vector of bacteria (Borrelia), rickettsiae, protozoa (Babesia).

Site of infection: skin.

Geographical distribution: cosmopolitan.

Prevention against tick bite:
• avoid known or suspected areas in which ticks live (walk only on cleared paths and avoid bushes and tall grass);
• wear proper clothing (light colours of clothing, long pants, with long- sleeves shirts and closed-toed shoes);
• use repellents.

Sarcoptes scabiei

(itch mite)

Host: human.

Life cycle: eggs, larvae (6 legs), nymph (8 legs), adult (8 legs).

Transmission: transfer of S. scabiei during personal contact or rarely by dirty bedding and clothes.

Site of infection: skin - predominantly between the fingers and on the wrists.

Diagnostic method(s):
• the appearance and distribution of the rash and the presence of burrows;
• isolation of the mites, larvae or ova from a skin scraping.

Geographical distribution: cosmopolitan.

Remarks: other races of scabies may infect other mammals such as domestic cats, dogs, pigs, and horses.

Demodex folliculorum

(follicle mite)

Host: human.

Life cycle: eggs, larvae (6 legs), nymph (8 legs), adult (8 legs).

Transmission: transfer of D. folliculorum during personal contact or by dirty microscopic oculars or glasses.

Site of infection: hair follicles, epidermis of the nose and adjacent regions of the face.

Diagnostic method(s): microscopic identification of skin scrapings or hair from eyebrows and eyelashes.

Geographical distribution: cosmopolitan.

Remarks: two species of follicle mites parasitize humans; D. folliculorum is found in the hair follicles above the sebaceous glands, and D. brevis occurs in sebaceous glands.

Pediculus sp.

(louse)

Species: P. capitis (head louse), P. humanus (body louse) and Pthirus pubis (crab louse).

Host: human.

Life cycle: eggs (nits), nymphs, adults (incomplete metamorphosis).

Transmission:
• P. capitis and P. humanus - by dirty clothes (hats, scarves), towels and barber instruments (combs, brushes), bedding and personal contact;
• Phthirus pubis - by sexual contact and bedding.

Sites of infection:
• P. capitis - on the scalp;
• P. humanus - on the clothes near the skin;
• Phthirus pubis - on the pubic hair (occasionally in eye brows and beard).

Geographical distribution: cosmopolitan.

Diagnostic method(s): finding nymphs, adult or eggs on the hair or clothes.

Pulex irritans

(human flea)

Host: warm-blooded animals (including human).

Vector of: plague, murine typhus and Dipylidium caninum.

Life cycle: eggs, larvae, pupa, adults (complete metamorphosis).

Sites of infection: skin.

Geographical distribution: cosmopolitan.

Diagnostic method(s): finding adult stage on the host body.

Cimex lectularius

(bedbug)

Host: warm-blooded animals (including human).

Life cycle: eggs, nymph, adults = imago (incomplete metamorphosis).

Sites of infection: skin.

Geographical distribution: cosmopolitan.

Diagnostic method(s):

• In rooms where bedbugs occur, the characteristic sweet smell of coriander or rotting raspberries (caused by a greasy liquid secreted by insects) is felt.

• In addition, painful redness and irritation occur on the skin of affected people.