Skin complaints are common in travellers to foreign countries and are responsible for up to 25% of medical consultations by military personnel during deployments in the tropics. They also have relatively high rates of field hospital admission, medical evacuation and referral to UK Role 4 healthcare facilities. Non-infectious tropical skin diseases include sunburn, heat rash, arthropod bites, venomous bites, contact dermatitis and phytophotodermatitis. During tropical deployments skin infections that commonly occur in military personnel may become more frequent, severe and difficult to treat. Several systemic tropical infections have cutaneous features that can be useful in making early diagnoses. Tropical skin infections such as cutaneous larva migrans, cutaneous myiasis, cutaneous leishmaniasis and leprosy do occur in British troops and require specialist clinical management. This illustrated review focuses on the most significant tropical skin diseases that have occurred in British military personnel in recent years. Clinical management of these conditions on deployments would be improved and medical evacuations could be reduced if a military dermatology ‘reach-back’ service (including a telemedicine facility) was available.
- Tropical medicine < INFECTIOUS DISEASES
- Skin diseases, infectious
- Military personnel
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A wide range of skin diseases cause significant problems on military deployments to the tropics.
These may be due to non-infectious causes, common skin infections, systemic tropical infections or tropical skin infections.
The development of a military dermatology ‘reach-back’ service (including a telemedicine facility) should be considered.
Skin complaints are common in travellers to foreign countries1 and are responsible for up to 25% of medical consultations by military personnel during deployments in the tropics.2 They account for about 20% of primary care consultations by British troops in Afghanistan and have relatively high rates of field hospital admission and medical evacuation.3 Skin complaints are also the commonest cause of referral to the UK Role 4 Military Infectious Diseases and Tropical Medicine Service.4 ,5 This illustrated review focuses on the most significant tropical skin diseases that have occurred in British military personnel in recent years.
Non-infectious skin diseases in the tropics
Common non-infectious skin diseases include sunburn, heat rash (miliaria rubra), arthropod bites (including bed bugs) and ectoparasites (especially ticks), which medical officers will already be familiar with. More unusual non-infectious skin diseases include venomous bites and various forms of contact dermatitis and phytophotodermatitis. Venomous bites from vipers and cobras produce both local and systemic effects that require treatment with anti-venom and other supportive measures.6 However, bites from recluse spiders (loxoscelism) produce local skin necrosis only and there is no specific treatment apart from symptom relief, wound care and sometimes surgical debridement.7 Contact dermatitis may be either irritant or allergic in origin and can have many possible causes in military personnel.8 These include reactions to N,N-diethyl-meta-toluamide (DEET) insect repellents and the beetle dermatitis that affects British troops in Kenya.9 Phytophotodermatitis is caused by plant substances (psoralens) that induce localised photodermatitis when they come into contact with skin.10 The resulting skin lesions looks like a severe, blistering sunburn that has a focal distribution. Treatment for both types of dermatitis consists of symptomatic relief including the possible use of topical or systemic steroids, and prevention is possible by avoiding or washing off the substances responsible as soon as possible.
Common skin infections in the tropics
The commonest skin infections in military personnel during deployments to the tropics are usually the same as those seen in everyday military practice.11 Streptococcal and staphylococcal skin infections (including Panton-Valentine leukocidin producing strains) seem to occur more frequently on deployments due increased heat and humidity and also diminished washing, laundry and accommodation facilities. Eradication of staphylococcal carriage and environmental contamination can be very difficult under such circumstances.
Superficial fungal skin infections may occur in greater than 50% of deployed troops due to environmental and living conditions.2 These can present as tinea pedis, tinea cruris, tinea corporis, tinea axillae, tinea capitis, intertrigo or pityriasis versicolour, which are usually cured by prompt topical anti-fungal treatments and improved hygiene measures. Onychomycosis (Figure 1) may also develop and requires prolonged oral treatment with terbinafine or itraconazole.
Viral infections such as varicella can occur and cause outbreaks on military deployments12 and it is important to remember that some of these diseases are much less common in the tropics, which gives them the potential to cause outbreaks of severe disease in adults. Oral herpes is more likely to relapse with increased sun exposure and genital warts (but not genital herpes) also seem to recur and relapse during military deployments to the tropics and sub-tropics (D Leverton and N Dufty, personal communication, 2013). HIV should be considered if personnel develop a febrile illness with a generalised macular rash, resistant seborrhoeic dermatitis, varicella zoster or other HIV-associated skin diseases.13
Tropical infections with cutaneous features
Many tropical infections have cutaneous features, which can be useful in making an early diagnosis, especially if a patient presents with an undifferentiated febrile illness (UFI).14 Arboviral infections usually produce non-specific rashes that may be macular, papular or petechial. However, more characteristic skin features include the possible eschar and vasculitic rash of rickettsial infections (Figure 2), the ‘rose’ spots of typhoid or paratyphoid enteric fever (Figure 3) and the purpuric rash of meningococcal infection.
Exposure to freshwater containing Schistosoma cercariae may initially produce a ‘swimmer's itch’ with few visible signs, but if acute schistosomiasis (Katayama fever) occurs 2–4 weeks later, then a UFI with urticarial lesions and eosinophilia is typical.15 Microscopy for eggs in urine or faeces and serology tests are usually negative at this early stage of the illness and so treatment with praziquantel and steroids is often given empirically. Since praziquantel is not effective against immature schistosomes, a repeat course of treatment should be given at least 1 month later. This also explains why praziquantel cannot be used for post-exposure prophylaxis against schistosomiasis.
Hookworm infection and strongyloidiasis are intestinal helminth infections that spread via faeco-dermal transmission and are more common in British military personnel than helminths transmitted by mouth.16 Penetration of the larvae through skin may produce a transient ‘ground itch’ with few visible signs, but Strongyloides larvae are able to circulate throughout the body, producing a transient, linear, urticarial rash called ‘larva currens’ (Figure 4). This advances by several millimetres or centimetres per hour and usually occurs in association with gastrointestinal and respiratory symptoms and eosinophilia. Although hookworm and other intestinal helminths can be diagnosed simply by microscopy of faeces, strongyloidiasis requires specialist charcoal stool cultures or serology tests. Furthermore, these other helminths can be treated with a single course of albendazole, but strongyloidiasis is best treated with two courses of ivermectin taken 3 weeks apart (because auto-infection occurs despite good hygiene and anti-helminthic drugs are usually not effective against immature worms). Unfortunately, ivermectin is less effective against the other intestinal helminths and so it is important to make confirmed diagnoses in order to choose the best treatment for these diseases. This is especially true for strongyloidiasis, which can lead to life-long infection with possible life-threatening dissemination or hyperinfection if patients become immunocompromised in later life.17
Tropical skin infections
Cutaneous larva migrans is a form of creeping eruption caused by hookworm larvae from animals such as dogs and cats, which are not adapted to human hosts.18 After entering the skin they are not able to penetrate the basement membrane and so migrate throughout the epidermis producing a raised, erythematous, serpiginous and pruritic eruption (Figure 5). This advances by a few millimetres or centimetres per day and may become vesicular or even bullous in appearance. Systemic features are unusual and should prompt investigations for other related helminth infections.16 Oral treatment with ivermectin or albendazole is more effective than topical treatments and anti-histamine medication for the pruritis is usually much appreciated.
Myiasis refers to the infestation of humans or other vertebrates with dipterous larvae, which can affect various anatomical sites and be caused by many different species.19 In recent years, British troops have suffered from ophthalmomyiasis due to Oestrus ovis (sheep nasal bot fly) in Afghanistan, with similar cases occurring previously in Iraq and Cyprus.20 Troops have also developed cutaneous (furuncular) myiasis due to Cordylobia anthropophaga (tumbu fly) from Sierra Leone and Dermatobia hominis (bot fly) from Belize. These cutaneous infestations usually present as furuncles that discharge a sero-sanguinous or purulent fluid and patients often complain of pain and feelings of movement within the lesion.21 Tumbu fly myiasis takes several days to develop and the egg-shaped larvae are more likely to emerge spontaneously, whereas bot fly myiasis takes several weeks to develop and the flask-shaped larvae are more likely to require surgical removal. In both cases conservative treatment to occlude the punctum (using petroleum jelly under an occlusive dressing) should be tried to suffocate the larva and cause it to emerge. If this fails, then a cruciform incision over the punctum will allow the larva to be squeezed out. More extensive surgery is not required, but a previous complete excision of a bot fly furuncle (Figure 6) does illustrate how narrow the punctum can be in comparison to the larva and hence why conservative treatment is not always effective.
Cutaneous leishmaniasis (CL) is an infection caused by various species of Leishmania protozoa, which are transmitted by the bite of various species of phlebotomine sandflies.22 In recent years cases have occurred in British troops deployed to Belize,23 Afghanistan,24 ,25 Iraq and elsewhere and 45% of all cases seen in the UK from 1998 to 2009 were in military personnel.23 These skin lesions usually develop weeks or months after inoculation and typically form ulcers with raised edges (Figure 7), but may also have a hyperkeratotic or nodular appearance. They are usually non-tender unless secondary infection occurs and do not respond to anti-bacterial treatment. Military personnel with possible CL should be referred to the UK Role 4 Military Infectious Diseases and Tropical Medicine Service at Birmingham Heartlands Hospital5 because of problems that have occurred when cases are referred elsewhere.26 The diagnosis is made from a skin biopsy of the edge of the lesion that is sent for histology and parasitology tests, which can identify the exact species involved. The choice of treatment is currently dependent on the site, size and number of lesions, whether there are features of dissemination and the species involved.27 Local treatments such as intralesional injection of sodium stibogluconate (SSG) and cryotherapy may be effective for some lesions,28 but systemic treatments such as intravenous SSG and oral miltefosine are sometimes required.27
Leprosy is a chronic infection of the skin, peripheral nerves, eyes and nasal mucosa by Mycobacterium leprae, which is transmitted by respiratory droplets and has low infectivity overall.29 Cases have occurred recently in British Gurkha soldiers and their families (D Lockwood, personal communication, 2013) and in other Commonwealth countries where British troops are recruited and so medical officers need to be aware of the clinical features. Early skin lesions may occur as poorly defined macules or nodules that are hypopigmented or erythematous and have normal sensation, which then progress to disease that ranges from ‘tuberculoid’ to ‘lepromatous’. Tuberculoid or paucibacillary leprosy (where there is a good immune response) presents with one or a few lesions, which are usually macules or plaques with well-defined edges and surfaces that are dry, scaly, hairless and anaesthetic. In dark skin they are usually hypopigmented, whereas in light skin they may be erythematous. Lepromatous or multibacillary leprosy (where there is a poor immune response) presents insidiously with multiple, widely distributed lesions, which begin as nodules with poorly defined edges and more subtle colour changes. These coalesce to cause skin thickening with associated hair loss and there is also widespread peripheral nerve enlargement that leads to neuropathy. Patients may develop a ‘leonine’ facies, destruction of the nasal cartilage and eye complications such as corneal damage and cataracts (Figure 8). Suspected or confirmed cases of leprosy should be referred to the infectious and tropical diseases units in Birmingham, Liverpool or London in accordance with recent guidelines.30 The diagnosis is made from slit-skin smears or skin biopsies and treatment requires multi-drug therapy for at least 6 months depending on the type of disease and response to treatment.
Military doctors have made major contributions in the field of tropical dermatology31 and a wide range of skin diseases cause significant problems on military deployments to the tropics. However, the latest UK Defence Medical Services manpower review (DMS 20)32 has cut the requirement for any regular service dermatologists, which will reduce the military expertise and support available to medical officers (especially on deployments) unless alternative reserve service or National Health Service provision is made. Clinical management of skin diseases on deployments would be improved and medical evacuations could be reduced if a military dermatology ‘reach-back’ service (including a telemedicine facility) was available.
Competing interests None.
Provenance and peer review Not commissioned; internally peer reviewed.