8.14 Tropical dermatoses and travel medicine

Tropical skin diseases.

Dermatologic and venerologic diseases that are acquired in tropical or sub-tropical regions.

In non-tropical countries most patients diagnosed are immigrants or travellers.

Up to 50% of the local population in the tropics may be affected by a skin disease. Variable incidence and prevalence for each disease and region. The majority are infections or infestations. 
Skin diseases may affect up to 8% of travellers returning from tropical or sub-tropical climate regions. Frequently common dermatoses such as eczema, acne, psoriasis or a pre-existing skin infection may exacerbate. A small proportion contract a tropical or exotic skin disease by first exposure.

Tropical skin diseases are all communicable and non-communicable cutaneous diseases that occur principally in tropical and sub-tropical regions.

Travellers' Tropical Skin Diseases:  Skin diseases present in travellers returning from the tropics.

Disabling infections that dominate health care in the tropics are known as Neglected Tropical Diseases or NTDs.  The World Health Organisation has focused on a strategy of integrating preventative, investigative, curative and supportive care for NTDs.

A significant burden is caused by different micro-organisms, parasites, land and sea animals, and arthropods. Other skin diseases caused by environmental (such as heat, humidity, and altitude), and nutritional conditions.

Specific and common tropical skin diseases include:

1. Infectious disorders

• Fungal infections: Mycetoma, deep fungal Infections, dermatophytoses.
• Bacterial infections:  Staphylococcus aureus, Group A streptococcal infections.
• Viral Infections: Yellow fever, Zika disease, dengue, chikungunya.
• Treponematosis: Yaws.           
• Mycobacterial disorders: Leprosy, Buruli ulcer, cutaneous tuberculosis, atypical mycobacteria infections.
• Protozoan disorders: Leishmaniasis, trypanosomiasis.
• Parasitic diseases: Schistosomiasis, strongyloidiasis, onchocerciasis, tapeworm, trichuriasis, filariasis, tungiasis, scabies, larva migrans.
• STI (Sexually transmitted infections): HIV infection, chancroid, lymphogranuloma inguinale.

2. Non-infectious disorders:

• Insect bite reactions, athropods, jellyfish.

A wide spectrum of clinical manifestations depending on the etiology. Extremely variable. Tropical dermatoses may show some distinctive clinical patterns:

• Cutaneous rashes associated with fever.
• Itchy rashes.
• Migratory rashes.
• Nodular lesions.
• Muco-cutaneous ulcers.
• Persistent edema of the extremities.
• Papular eruptions, maculo-plaques.
• Eschars.  

The lesions may cause pruritus, loss of sensation (hypoesthesia or anesthesia), or changes of the skin pigmentation (hypo or hyperpigmentation).

Common dermatoses occurring worldwide may show in tropical countries different clinical presentations (e.g. acne, eczema, tinea, insect bites).

Variable. Localized lesions or generalized eruptions. The lesions often develop on exposed areas (face and extremities).

Complete blood cell count. Presence of peripheral blood eosinophilia. Complete biochemical survey. Specific serologies in selected cases. Parasitological studies (blood, smears, skin, and stools).

Identification (visualization) of the responsible agent. Conventional histology. Specific stains besides HE, i.e. Giemsa, PAS, Fite, specific antibodies (eg mycobacterial stains).

Variable depending on the etiology.

Variable depending on the etiology.

Travel and developed activities, exposure to fresh or sea water, animals, arthropods, plants, history of previous trauma.

Past medical history: Immune status of the host, vaccinations, drugs and prophylaxis.

Clinical history:  Time of onset of skin lesions, evolution, and associated symptoms (itching, pain, fever).

Depending on the clinical context: histopathological evaluation (cutaneous biopsy), bacilloscopy (leprosy), microbiological cultures (swabs and/or skin biopsies). 

Parasitological evaluation.

Specific serologies.

Micro-organism PCR amplification.

Preventive measures are required.

Most conditions respond to specific recommended treatments.

Variable prognosis: Depending on the disease and social context.

Knowledge of geographic differences of tropical skin diseases in relation to travel history or country of origin may be useful.

Pre-travel counselling. Recommended vaccination for specific tropical infections. Prevention: Proper clothing, shoes, insect repellents, insecticides, barrier measures, bed netting. Avoiding contaminated water or eating raw or undercooked food.